Why Poor Ventilation Strains AC Systems

Why Poor Ventilation Strains AC Systems

automobile repair shop

The Relationship Between Ventilation and AC Efficiency



In the quest for indoor comfort, especially during hot and humid months, air conditioning (AC) systems play a pivotal role. However, an often overlooked aspect that significantly affects the efficiency and longevity of these systems is ventilation. The relationship between ventilation and AC efficiency is crucial; poor ventilation can strain AC systems, leading to higher energy consumption, increased wear and tear, and ultimately more frequent breakdowns.

Ventilation involves the exchange of indoor air with outdoor air to improve indoor air quality by reducing pollutants, moisture levels, and odors. Unusual odors from your vents might indicate a problem that requires HVAC Repair Emergency AC repair to optimize your heat exchanger performance. When homes or buildings are poorly ventilated, it means that stale air laden with heat and humidity remains trapped inside. This situation compels the AC system to work harder than necessary because it must continually cool down the same volume of hot air without any fresh influx from outside.

One primary way poor ventilation strains an AC system is through increased load demand. Without adequate ventilation to expel warm indoor air and bring in cooler outside air (when applicable), the burden on the AC unit intensifies as it tries to maintain a comfortable temperature indoors. This continuous cycle of cooling not only spikes energy usage but also accelerates wear on key components like compressors and fans.

Moreover, inadequate ventilation can lead to imbalanced humidity levels within a space. High humidity makes it harder for sweat to evaporate off our skin, making us feel hotter than we actually are-prompting individuals to lower thermostat settings further straining the AC system. Excessive moisture can also contribute to mold growth within ducts or around vents if proper airflow isn't maintained, potentially damaging both health conditions indoors as well as structural integrity over time.

Proper ventilation aids in maintaining optimal operational conditions for an AC system by ensuring that there is adequate airflow throughout all areas served by ductwork while minimizing pressure differences across rooms which could otherwise disrupt effective cooling cycles needed during peak seasons when temperatures soar high outdoors necessitating efficient service delivery from HVAC units installed therein too!

To alleviate these issues associated with poor ventilation affecting ac performance negatively: homeowners should ensure regular maintenance checks conducted periodically involving cleaning filters replacing worn-out parts upgrading insulation where necessary optimizing layout designs maximizing natural cross-breezes possible via strategic window placements using ceiling fans assistively circulate refreshed atmosphere amongst various spaces inhabited daily basis – thereby promoting healthier living environments overall enhanced satisfaction derived thereof!

In conclusion: understanding importance attributed towards fostering symbiotic relationship existing between sufficient ventilating practices alongside optimized utilization strategies pertaining specifically towards installed hvac infrastructures paramount achieving desired results long-term success sustaining comfort required modern lifestyles today tomorrow alike!

How Poor Ventilation Contributes to System Overload



Poor ventilation is a critical factor that often goes unnoticed when discussing the efficiency and longevity of air conditioning (AC) systems. The relationship between inadequate ventilation and system overload is both direct and detrimental, leading to increased energy consumption, higher operational costs, and potential system failures.

To understand how poor ventilation affects AC systems, it's essential to first consider the basic function of an air conditioner: it regulates indoor temperature by removing heat from a given space. For this process to occur efficiently, adequate airflow is necessary. When a room or building has poor ventilation, the circulation of air becomes restricted. This means that stale indoor air remains trapped while fresh outdoor air is limited in entering the environment. As a result, the AC unit must work harder to cool down the same volume of stagnant warm air repeatedly.

This constant cycle places an undue burden on the AC system for several reasons. Firstly, poor ventilation can lead to uneven cooling throughout a space. Some areas may remain warmer than others due to inadequate air distribution, prompting residents or employees to lower the thermostat settings further in an attempt to achieve comfort. This adjustment forces the AC unit into overdrive as it attempts to meet these demands across varying zones within a building.

Moreover, restricted airflow can cause components within the AC system-such as coils and filters-to accumulate dust and debris more rapidly. These blockages diminish the unit's efficiency by impeding heat exchange processes crucial for cooling operations. Over time, clogged filters can even lead to overheating issues as they restrict internal airflow needed for proper mechanical functioning.

Another consequence of poor ventilation is increased humidity levels indoors. An effective AC system not only cools but also dehumidifies; however, without proper airflow facilitating moisture removal outside through exhaust pathways or vents, humidity builds up inside instead.

Why Poor Ventilation Strains AC Systems - automobile repair shop

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High humidity creates additional strain because humid air requires more energy for temperature reduction compared with dry conditions-thus amplifying electricity usage unnecessarily.

In addition to immediate performance concerns like reduced cooling effectiveness or elevated electric bills due largely in part from this inefficiency caused by insufficient venting methods employed around facilities where people live/work/play daily lives together harmoniously under one roof alike everywhere else too! Long-term repercussions are inevitable if left unaddressed: premature wear-and-tear breakdowns will likely occur sooner than expected timelines dictate otherwise typically seen before now historically speaking across varied industries worldwide today already experienced firsthand stories shared among peers universally acknowledged truthfully stated unequivocally confirmed beyond doubt whatsoever!

To mitigate these risks associated with inadequate ventilation impacting overall HVAC health status quo maintained optimally running smoothly always ensure proactive measures taken into account regularly scheduled inspections performed diligently serviced promptly addressed issues identified resolved swiftly avoiding costly repairs replacements down road potentially saving money long run benefiting everyone involved ultimately achieving desired outcomes successfully attained mutually beneficial manner conducive positive experiences enjoyed collectively whole community engaged actively participating willingly contributing towards goal attainment realizing dreams aspirations fulfilled reality lived happily ever after finally reaching pinnacle prosperity achieved together collaboratively united front presented proudly look back fondly upon achievements made possible teamwork dedication commitment excellence pursued relentlessly strive greatness forevermore onward upward progress continues unabated unwavering determination perseverance triumphantly prevailing victorious end journey embarked embarked upon initially started anew beginning anew chapter unfolds exciting adventures await discovery awaits exploration beckons enticingly inviting all join partake revelry celebration life itself offers boundless opportunities endless possibilities infinite potential unleashed fully realized maximized fullest extent imaginable conceivable attainable grasp reach destiny awaits those dare dream big bold enough pursue passionately wholeheartedly embrace challenges head-on conquer obstacles overcome difficulties rise above adversities emerge stronger wiser better equipped face future confidently assuredly poised succeed grand scale monumental achievement unparalleled

Increased Energy Consumption Due to Inadequate Airflow

Increased Energy Consumption Due to Inadequate Airflow



The modern world places a significant emphasis on the comfort and efficiency of indoor environments, particularly through the use of air conditioning (AC) systems. However, one often overlooked factor that can place undue strain on these systems is poor ventilation. Inadequate airflow not only diminishes the effectiveness of AC units but also leads to increased energy consumption, ultimately impacting both our wallets and the environment.

To understand why poor ventilation strains AC systems, it's crucial to grasp how these systems function. Air conditioners work by removing heat and humidity from indoor air and expelling it outside. For this process to be efficient, there must be a continuous exchange of air; fresh air should enter while stale air exits. When ventilation is inadequate, this essential exchange is disrupted. The system finds itself battling against stagnant indoor conditions where heat builds up faster than it can be expelled.

In such scenarios, AC units have to exert more effort to achieve the desired temperature settings. This means running longer cycles or even operating continuously during peak hours, which directly translates into higher energy consumption. The underlying problem here is that without proper airflow, an AC unit cannot efficiently transfer heat out of the building or circulate cool air throughout it evenly. As a result, rooms may feel warmer in some areas despite the AC working overtime.

Moreover, poor ventilation affects humidity levels indoors. Excess moisture remains trapped inside due to insufficient airflow, leading to discomfort and potentially fostering mold growth over time-conditions that most people find undesirable and unhealthy. To combat high humidity levels without effective ventilation support means pushing an AC system harder than necessary because it's forced into simultaneously cooling the space while attempting dehumidification under suboptimal conditions.

From an economic perspective too much energy usage results in inflated utility bills - something no household or business desires when striving for cost-efficiency amidst rising energy prices globally . On another front , environmental concerns arise since excessive power consumption contributes significantly toward carbon emissions thereby exacerbating climate change issues worldwide .

To alleviate these problems associated with inadequate airflow , regular maintenance checks become indispensable steps ensuring proper operation vents free blockages filters cleaned timely manner allowing unrestricted passage currents necessary maintaining balanced atmospheric pressure indoors .

Additionally incorporating supplementary solutions like installing ceiling fans strategically placed windows doors open periodically facilitate natural cross-ventilation practices help augment artificial methods resulting reduced reliance solely mechanical cooling mechanisms sustainable approach long-term benefits everyone involved including planet itself

In conclusion poor ventilation represents silent adversary lurking within buildings quietly undermining efforts optimize living spaces economically environmentally therefore addressing tackling head-on paramount importance preserving functionality longevity integrity investments made towards creating comfortable habitable surroundings future-proofed against inevitable challenges tomorrow holds

Increased Energy Consumption Due to Inadequate Airflow
Common Signs of Strain on AC Systems from Poor Ventilation

Common Signs of Strain on AC Systems from Poor Ventilation

Common Signs of Strain on AC Systems from Poor Ventilation



Air conditioning systems are essential for maintaining comfortable indoor environments, particularly during the sweltering months of summer. However, their efficiency and longevity can be significantly compromised by poor ventilation. Understanding the common signs of strain on AC systems due to inadequate ventilation is crucial for preventing costly repairs and ensuring optimal performance.

One of the most noticeable indications that an air conditioning system is under strain from poor ventilation is reduced cooling efficiency. When a space lacks proper airflow, it forces the AC unit to work harder to maintain the desired temperature. This excessive effort not only leads to higher energy consumption but also results in uneven cooling throughout the area. As a consequence, some rooms may remain uncomfortably warm while others become excessively cold, creating an inconsistent climate within the home or building.

Another symptom of strain on an AC system caused by poor ventilation is frequent cycling on and off.

Why Poor Ventilation Strains AC Systems - Chickasaw

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Poor airflow limits heat exchange processes, making it difficult for the system to achieve its set temperature efficiently. Consequently, the system ends up cycling more frequently than necessary as it struggles to keep up with demand. This constant starting and stopping wears down components faster than normal operation would, ultimately reducing the lifespan of critical parts such as compressors and fans.

Increased humidity levels indoors can also signal that your AC unit is strained by insufficient ventilation. Air conditioners are designed not only to cool spaces but also to dehumidify them by removing excess moisture from the air. When there is inadequate ventilation, however, this dehumidification process becomes less effective. High humidity levels make interiors feel warmer and more uncomfortable even if temperatures are moderate, thereby forcing occupants to lower thermostat settings further straining the system.

Moreover, strange noises emanating from your air conditioner can indicate stress due to improper airflow. Grinding or squealing sounds often suggest that internal components like motors or belts may be overworking themselves because they lack sufficient fresh air intake needed for smooth operation.. Ignoring these audible warnings could lead to severe mechanical failures requiring extensive repairs or even replacement.

Higher utility bills without a corresponding increase in usage might also point towards an overburdened AC resulting from bad ventilation practices . Since systems must expend extra energy trying compensate lack circulation , homeowners notice sudden spikes electricity costs despite no changes habits patterns use .

To mitigate these issues related poor airflow , regular maintenance including cleaning filters ducts checking vents ensure unobstructed passage vital . Additionally installing exhaust fans strategically placed windows doors help promote adequate cross-ventilation prevent buildup stale stagnant inside environment which ultimately safeguards both machinery inhabitants alike .

In conclusion recognizing responding promptly telltale signs trouble save significant headaches expense down line . By addressing root causes behind inefficient operations namely deficient one protect investment enhance comfort those rely upon daily basis .

Long-term Effects on System Longevity and Maintenance Costs

Long-term Effects on System Longevity and Maintenance Costs



Poor ventilation in a building can have significant long-term effects on the longevity of air conditioning (AC) systems and can substantially increase maintenance costs.

Why Poor Ventilation Strains AC Systems - Chickasaw

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Understanding these impacts is crucial for anyone responsible for maintaining a facility, as well as for homeowners who wish to ensure their AC systems function efficiently over time.

Firstly, poor ventilation forces AC systems to work harder than necessary. When a space lacks adequate ventilation, it often results in uneven temperature distribution and increased humidity levels. The AC unit must then run longer cycles to maintain the desired temperature, leading to excessive wear and tear on its components. Over time, this constant strain can shorten the lifespan of the system significantly. Compressors and fans may fail sooner than expected due to overuse, necessitating costly repairs or even premature replacement of the entire unit.

Moreover, poor ventilation often leads to an accumulation of dust and other particulates within the AC system itself. Filters become clogged more quickly when they are forced to circulate stale air loaded with contaminants that would otherwise be expelled by proper ventilation. This not only reduces the efficiency of the system but also increases energy consumption as the unit struggles against restricted airflow. Regular cleaning and filter replacement become more frequent needs under such conditions, adding additional maintenance costs.

Another factor to consider is how inefficient ventilation contributes to higher humidity levels inside buildings. High humidity can lead to condensation within ductwork and other parts of the AC system, potentially causing rust and corrosion over time. These issues further degrade system components and necessitate expensive repairs or replacements.

Additionally, inadequate ventilation may contribute indirectly by affecting indoor air quality negatively-leading occupants to adjust temperatures more frequently in search of comfort, which places added demand on cooling systems.

To mitigate these problems, it is essential for property owners and managers to invest in improved ventilation solutions such as opening windows where possible or installing mechanical ventilators that promote better air circulation throughout a building. Doing so not only helps preserve an AC system's integrity but also enhances overall indoor comfort while reducing operational costs associated with unnecessary repairs or inflated energy bills.

In conclusion, ensuring adequate ventilation is vital for protecting an investment in any air conditioning system by promoting its longevity and reducing ongoing maintenance expenses significantly-benefits worth considering when evaluating building infrastructure management strategies comprehensively.

Strategies for Improving Ventilation to Enhance AC Performance
Strategies for Improving Ventilation to Enhance AC Performance

Strategies for Improving Ventilation to Enhance AC Performance



Effective ventilation plays a crucial role in optimizing air conditioning (AC) performance, yet it is often overlooked. Poor ventilation can significantly strain AC systems, leading to inefficiencies and increased energy consumption. To understand why this occurs, one must first consider the relationship between ventilation and indoor air quality.

When an AC system operates in a poorly ventilated environment, it struggles to maintain the desired temperature and humidity levels because the air within the space becomes stagnant. This stagnation means that pollutants, moisture, and heat are not adequately removed from the indoor environment. Consequently, the AC unit has to work harder to compensate for these factors, which can lead to wear and tear over time.

One strategy for improving ventilation involves integrating mechanical ventilation systems alongside traditional AC units. Mechanical systems like exhaust fans or energy recovery ventilators can help exchange stale indoor air with fresh outdoor air without compromising on energy efficiency. By doing so, they reduce the load on AC systems by maintaining more consistent indoor conditions.

Another effective strategy is ensuring that existing ductwork is properly sealed and insulated. Leaky ducts can allow conditioned air to escape into unconditioned spaces such as attics or crawlspaces, while also allowing unfiltered outdoor air into living areas. This results in uneven cooling distribution and forces the AC system to operate longer than necessary.

Regular maintenance of both the ventilation components and the AC system itself is critical as well. Filters should be replaced regularly to prevent clogging which restricts airflow; coils should be cleaned to ensure efficient heat exchange; and thermostats should be calibrated correctly for accurate temperature readings.

In addition to technical approaches, incorporating natural elements like strategically placed windows or vents can enhance cross-ventilation in buildings. When designed effectively, natural ventilation reduces reliance on mechanical cooling methods by leveraging wind patterns and thermal buoyancy to circulate fresh air throughout a space.

Ultimately, improving ventilation requires a holistic approach that considers both mechanical solutions and structural design elements. By implementing these strategies proactively, building owners can enhance their AC systems' performance while reducing operational costs and extending equipment lifespan-a win-win scenario for comfort sustainability alike.

Diagram of a HEPA (high-efficiency particulate air) filter
Reusable washable HVAC air filter

A particulate air filter is a device composed of fibrous, or porous materials which removes particulates such as smoke, dust, pollen, mold, viruses and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) may also remove odors and gaseous pollutants such as volatile organic compounds or ozone.[1] Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines.

Some buildings, as well as aircraft and other human-made environments (e.g., satellites, and Space Shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method, air ionizers, use fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and air compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favour aside from niche uses. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid dynamics of the air-compressor part of the gas turbines.

Do-it-yourself air cleaner are low-cost alternative to commercial portable air cleaners.[2]

HEPA filters

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High efficiency particulate arrester (HEPA),[3][4] originally called high-efficiency particulate absorber but also sometimes called high-efficiency particulate arresting or high-efficiency particulate arrestance, is a type of air filter. Filters meeting the HEPA standard have many applications, including use in clean rooms for IC fabrication, medical facilities, automobiles, aircraft and homes. The filter must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE).

Varying standards define what qualifies as a HEPA filter. The two most common standards require that an air filter must remove (from the air that passes through) 99.95% (European Standard)[5] or 99.97% (ASME standard)[6] of particles that have a size greater than or equal to 0.3 μm.

Automotive cabin air filters

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The cabin air filter, also known in the United Kingdom as a pollen filter, is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the engine air filter. Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes.

The first automaker to include a disposable filter to keep the ventilation system clean was the Nash Motors "Weather Eye", introduced in 1940.[7]

A reusable heater core filter was available as an optional accessory on Studebaker models beginning in 1959, including Studebaker Lark automobiles (1959-1966), Studebaker Gran Turismo Hawk automobiles (1962-1964) and Studebaker Champ trucks (1960-1964). The filter was an aluminum frame containing an aluminum mesh and was located directly above the heater core. The filter was removed and installed from the engine compartment through a slot in the firewall. A long, thin rubber seal plugged the slot when the filter was installed. The filter could be vacuumed and washed prior to installation.

Clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream. Since the cabin air temperature depends upon the flow rate of the air passing through the heater core, the evaporator, or both, clogged filters can greatly reduce the effectiveness and performance of the vehicle's air conditioning and heating systems.[8]

Some cabin air filters perform poorly, and some cabin air filter manufacturers do not print a minimum efficiency reporting value (MERV) filter rating on their cabin air filters.[citation needed]

Internal combustion engine air filters

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Used auto engine air filter, clean side
Used auto engine air filter, dirty side
Auto engine air filter clogged with dust and grime
Low-temperature oxidation catalyst used to convert carbon monoxide to less toxic carbon dioxide at room temperature. It can also remove formaldehyde from the air.

The combustion air filter prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination.

Most fuel injected vehicles use a pleated paper filter element in the form of a flat panel. This filter is usually placed inside a plastic box connected to the throttle body with duct work. Older vehicles that use carburetors or throttle body fuel injection typically use a cylindrical air filter, usually between 100 millimetres (4 in) and 400 millimetres (16 in) in diameter. This is positioned above or beside the carburetor or throttle body, usually in a metal or plastic container which may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid. The overall unit (filter and housing together) is called the air cleaner.

Paper

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Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The "paper" term is somewhat misleading, as the filter media are considerably different from papers used for writing or packaging, etc. There is a persistent belief among tuners, fomented by advertising for aftermarket non-paper replacement filters, that paper filters flow poorly and thus restrict engine performance. In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt. Construction equipment engines also use this. The reason is that the paper is bent in zig-zag shape, and the total area of the paper is very large, in the range of 50 times of the air opening.[citation needed]

Foam

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Oil-wetted polyurethane foam elements are used in some aftermarket replacement automobile air filters. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-wetted foam in these applications. Foam filters are still commonly used on air compressors for air tools up to 5 horsepower (3.7 kW). Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer minimal airflow restriction or very high dirt capacity, the latter property making foam filters a popular choice in off-road rallying and other motorsport applications where high levels of dust will be encountered. Due to the way dust is captured on foam filters, large amounts may be trapped without measurable change in airflow restriction.[citation needed]

Cotton

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Oiled cotton gauze is employed in a growing number of aftermarket automotive air filters marketed as high-performance items. In the past, cotton gauze saw limited use in original-equipment automotive air filters. However, since the introduction of the Abarth SS versions, the Fiat subsidiary supplies cotton gauze air filters as OE filters.

Stainless steel

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Stainless steel mesh is another example of medium which allow more air to pass through. Stainless steel mesh comes with different mesh counts, offering different filtration standards. In an extreme modified engine lacking in space for a cone based air filter, some will opt to install a simple stainless steel mesh over the turbo to ensure no particles enter the engine via the turbo.

Oil bath

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An oil bath air cleaner consists of a sump containing a pool of oil, and an insert which is filled with fiber, mesh, foam, or another coarse filter media. The cleaner removes particles by adhering them to the oil-soaked filter media rather than traditional filtration, the openings in the filter media are much larger than the particles that are to be filtered. When the cleaner is assembled, the media-containing body of the insert sits a short distance above the surface of the oil pool. The rim of the insert overlaps the rim of the sump. This arrangement forms a labyrinthine path through which the air must travel in a series of U-turns: up through the gap between the rims of the insert and the sump, down through the gap between the outer wall of the insert and the inner wall of the sump, and up through the filter media in the body of the insert. This U-turn takes the air at high velocity across the surface of the oil pool. Larger and heavier dust and dirt particles in the air cannot make the turn due to their inertia, so they fall into the oil and settle to the bottom of the base bowl. Lighter and smaller particles stick to the filtration media in the insert, which is wetted by oil droplets aspirated there into by normal airflow. The constant aspiration of oil onto the filter media slowly carries most of the finer trapped particles downward and the oil drips back into the reservoir where the particles accumulate.

Oil bath air cleaners were very widely used in automotive and small engine applications until the widespread industry adoption of the paper filter in the early 1960s. Such cleaners are still used in off-road equipment where very high levels of dust are encountered, for oil bath air cleaners can sequester a great deal of dirt relative to their overall size without loss of filtration efficiency or airflow. However, the liquid oil makes cleaning and servicing such air cleaners messy and inconvenient, they must be relatively large to avoid excessive restriction at high airflow rates, and they tend to increase exhaust emissions of unburned hydrocarbons due to oil aspiration when used on spark-ignition engines.[citation needed]

Water bath

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In the early 20th century (about 1900 to 1930), water bath air cleaners were used in some applications (cars, trucks, tractors, and portable and stationary engines). They worked on roughly the same principles as oil bath air cleaners. For example, the original Fordson tractor had a water bath air cleaner. By the 1940s, oil bath designs had displaced water bath designs because of better filtering performance. [9]

Bulk solids handling filters

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Bulk solids handling involves the transport of solids (mechanical transport, pneumatic transport) which may be in a powder form. Many industries are handling bulk solids (mining industries, chemical industries, food industries) which requires the treatment of air streams escaping the process so that fine particles are not emitted, for regulatory reasons or economical reasons (loss of materials). As a consequence, air filters are positioned at many places in the process, especially at the reception of pneumatic conveying lines[10] where the quantity of air is important and the load in fine particle quite important. Filters can also be placed at any point of air exchange in the process to avoid that pollutants enter the process, which is particularly true in pharmaceuticals and food industries. The physical phenomena involved in catching particles with a filter are mainly inertial and diffusional[11]

Filter classes

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Under European normalization standards EN 779, the following filter classes were recognized:

Usage Class Performance Performance test Particulate size
approaching 100% retention
Test Standard
Coarse filters

(used as

Primary)

G1 65% Average value >5 μm BS EN779
G2 65–80% Average value >5 μm BS EN779
G3 80–90% Average value >5 μm BS EN779
G4 90%– Average value >5 μm BS EN779
Fine filters

(used as

Secondary)

M5 40–60% Average value >5 μm BS EN779
M6 60–80% Average value >2 μm BS EN779
F7 80–90% Average value >2 μm BS EN779
F8 90–95% Average value >1 μm BS EN779
F9 95%– Average value >1 μm BS EN779
Semi HEPA E10 85% Minimum value >1 μm BS EN1822
E11 95% Minimum value >0.5 μm BS EN1822
E12 99.5% Minimum value >0.5 μm BS EN1822
HEPA H13 99.95% Minimum value >0.3 μm BS EN1822
H14 99.995% Minimum value >0.3 μm BS EN1822
ULPA U15 99.9995% Minimum value >0.3 μm BS EN1822
U16 99.99995% Minimum value >0.3 μm BS EN1822
U17 99.999995% Minimum value >0.3 μm BS EN1822

European standard EN 779, on which the above table is based, remained in effect from 2012 to mid-2018, when it was replaced by ISO 16890.[12]

See also

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References

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  1. ^ "California Environmental Protection Agency - Air Cleaning Devices for the Home, Frequently Asked Questions" (PDF). California Environmental Protection Agency Air Resources Board. Retrieved 2016-12-14.
  2. ^ Holder, Amara L.; Halliday, Hannah S.; Virtaranta, Larry (2022). "Impact of do-it-yourself air cleaner design on the reduction of simulated wildfire smoke in a controlled chamber environment". Indoor Air. 32 (11): e13163. doi:10.1111/ina.13163. ISSN 1600-0668. PMC 9828579. PMID 36437679.
  3. ^ HEPA Company glossary of terms
  4. ^ Originally High Efficiency Particulate Arrestment - see thefreedictionary.com
  5. ^ European Standard EN 1822-1:2009, "High efficiency air filters (EPA, HEPA and ULPA)", 2009
  6. ^ American Society of Mechanical Engineers, ASME AG-1a–2004, "Addenda to ASME AG-1–2003 Code on Nuclear Air and Gas Treatment", 2004
  7. ^ Vwlarry (19 May 2009). "Nils Wahlberg and Nash - Salute To A Great Engineer And Unsung Automobiles".
  8. ^ "Dirty cabin air filter symptoms". FIRST BRANDS GROUP LLC. Retrieved 12 June 2024.
  9. ^ Peter, Paul. "Isolier Konzept". Retrieved 26 September 2022.
  10. ^ "Air filtration - Dust collectors".
  11. ^ "Solid Gas separation (cyclone - filtration)".
  12. ^ ISO 16890-1:2016(en) Air filters for general ventilation — Part 1: Technical specifications, requirements and classification system based upon particulate matter efficiency (ePM)
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There are various types of air conditioners. Popular examples include: Window-mounted air conditioner (Suriname, 1955); Ceiling-mounted cassette air conditioner (China, 2023); Wall-mounted air conditioner (Japan, 2020); Ceiling-mounted console (Also called ceiling suspended) air conditioner (China, 2023); and portable air conditioner (Vatican City, 2018).

Air conditioning, often abbreviated as A/C (US) or air con (UK),[1] is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature and in some cases also controlling the humidity of internal air. Air conditioning can be achieved using a mechanical 'air conditioner' or by other methods, including passive cooling and ventilative cooling.[2][3] Air conditioning is a member of a family of systems and techniques that provide heating, ventilation, and air conditioning (HVAC).[4] Heat pumps are similar in many ways to air conditioners, but use a reversing valve to allow them both to heat and to cool an enclosed space.[5]

Air conditioners, which typically use vapor-compression refrigeration, range in size from small units used in vehicles or single rooms to massive units that can cool large buildings.[6] Air source heat pumps, which can be used for heating as well as cooling, are becoming increasingly common in cooler climates.

Air conditioners can reduce mortality rates due to higher temperature.[7] According to the International Energy Agency (IEA) 1.6 billion air conditioning units were used globally in 2016.[8] The United Nations called for the technology to be made more sustainable to mitigate climate change and for the use of alternatives, like passive cooling, evaporative cooling, selective shading, windcatchers, and better thermal insulation.

History

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Air conditioning dates back to prehistory.[9] Double-walled living quarters, with a gap between the two walls to encourage air flow, were found in the ancient city of Hamoukar, in modern Syria.[10] Ancient Egyptian buildings also used a wide variety of passive air-conditioning techniques.[11] These became widespread from the Iberian Peninsula through North Africa, the Middle East, and Northern India.[12]

Passive techniques remained widespread until the 20th century when they fell out of fashion and were replaced by powered air conditioning. Using information from engineering studies of traditional buildings, passive techniques are being revived and modified for 21st-century architectural designs.[13][12]

An array of air conditioner condenser units outside a commercial office building

Air conditioners allow the building's indoor environment to remain relatively constant, largely independent of changes in external weather conditions and internal heat loads. They also enable deep plan buildings to be created and have allowed people to live comfortably in hotter parts of the world.[14]

Development

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Preceding discoveries

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In 1558, Giambattista della Porta described a method of chilling ice to temperatures far below its freezing point by mixing it with potassium nitrate (then called "nitre") in his popular science book Natural Magic.[15][16][17] In 1620, Cornelis Drebbel demonstrated "Turning Summer into Winter" for James I of England, chilling part of the Great Hall of Westminster Abbey with an apparatus of troughs and vats.[18] Drebbel's contemporary Francis Bacon, like della Porta a believer in science communication, may not have been present at the demonstration, but in a book published later the same year, he described it as "experiment of artificial freezing" and said that "Nitre (or rather its spirit) is very cold, and hence nitre or salt when added to snow or ice intensifies the cold of the latter, the nitre by adding to its cold, but the salt by supplying activity to the cold of the snow."[15]

In 1758, Benjamin Franklin and John Hadley, a chemistry professor at the University of Cambridge, conducted experiments applying the principle of evaporation as a means to cool an object rapidly. Franklin and Hadley confirmed that the evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water. They experimented with the bulb of a mercury-in-glass thermometer as their object. They used a bellows to speed up the evaporation. They lowered the temperature of the thermometer bulb down to −14 °C (7 °F) while the ambient temperature was 18 °C (64 °F). Franklin noted that soon after they passed the freezing point of water 0 °C (32 °F), a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about 6 mm (14 in) thick when they stopped the experiment upon reaching −14 °C (7 °F). Franklin concluded: "From this experiment, one may see the possibility of freezing a man to death on a warm summer's day."[19]

The 19th century included many developments in compression technology. In 1820, English scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate.[20] In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachicola, Florida. He hoped to eventually use his ice-making machine to regulate the temperature of buildings.[20][21] He envisioned centralized air conditioning that could cool entire cities. Gorrie was granted a patent in 1851,[22] but following the death of his main backer, he was not able to realize his invention.[23] In 1851, James Harrison created the first mechanical ice-making machine in Geelong, Australia, and was granted a patent for an ether vapor-compression refrigeration system in 1855 that produced three tons of ice per day.[24] In 1860, Harrison established a second ice company. He later entered the debate over competing against the American advantage of ice-refrigerated beef sales to the United Kingdom.[24]

First devices

[edit]
Willis Carrier, who is credited with building the first modern electrical air conditioning unit

Electricity made the development of effective units possible. In 1901, American inventor Willis H. Carrier built what is considered the first modern electrical air conditioning unit.[25][26][27][28] In 1902, he installed his first air-conditioning system, in the Sackett-Wilhelms Lithographing & Publishing Company in Brooklyn, New York.[29] His invention controlled both the temperature and humidity, which helped maintain consistent paper dimensions and ink alignment at the printing plant. Later, together with six other employees, Carrier formed The Carrier Air Conditioning Company of America, a business that in 2020 employed 53,000 people and was valued at $18.6 billion.[30][31]

In 1906, Stuart W. Cramer of Charlotte, North Carolina, was exploring ways to add moisture to the air in his textile mill. Cramer coined the term "air conditioning" in a patent claim which he filed that year, where he suggested that air conditioning was analogous to "water conditioning", then a well-known process for making textiles easier to process.[32] He combined moisture with ventilation to "condition" and change the air in the factories; thus, controlling the humidity that is necessary in textile plants. Willis Carrier adopted the term and incorporated it into the name of his company.[33]

Domestic air conditioning soon took off. In 1914, the first domestic air conditioning was installed in Minneapolis in the home of Charles Gilbert Gates. It is, however, possible that the considerable device (c. 2.1 m × 1.8 m × 6.1 m; 7 ft × 6 ft × 20 ft) was never used, as the house remained uninhabited[20] (Gates had already died in October 1913.)

In 1931, H.H. Schultz and J.Q. Sherman developed what would become the most common type of individual room air conditioner: one designed to sit on a window ledge. The units went on sale in 1932 at US$10,000 to $50,000 (the equivalent of $200,000 to $1,200,000 in 2024.)[20] A year later, the first air conditioning systems for cars were offered for sale.[34] Chrysler Motors introduced the first practical semi-portable air conditioning unit in 1935,[35] and Packard became the first automobile manufacturer to offer an air conditioning unit in its cars in 1939.[36]

Further development

[edit]

Innovations in the latter half of the 20th century allowed more ubiquitous air conditioner use. In 1945, Robert Sherman of Lynn, Massachusetts, invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air.[37] The first inverter air conditioners were released in 1980–1981.[38][39]

In 1954, Ned Cole, a 1939 architecture graduate from the University of Texas at Austin, developed the first experimental "suburb" with inbuilt air conditioning in each house. 22 homes were developed on a flat, treeless track in northwest Austin, Texas, and the community was christened the 'Austin Air-Conditioned Village.' The residents were subjected to a year-long study of the effects of air conditioning led by the nation’s premier air conditioning companies, builders, and social scientists. In addition, researchers from UT’s Health Service and Psychology Department studied the effects on the "artificially cooled humans." One of the more amusing discoveries was that each family reported being troubled with scorpions, the leading theory being that scorpions sought cool, shady places. Other reported changes in lifestyle were that mothers baked more, families ate heavier foods, and they were more apt to choose hot drinks.[40][41]

Air conditioner adoption tends to increase above around $10,000 annual household income in warmer areas.[42] Global GDP growth explains around 85% of increased air condition adoption by 2050, while the remaining 15% can be explained by climate change.[42]

As of 2016 an estimated 1.6 billion air conditioning units were used worldwide, with over half of them in China and USA, and a total cooling capacity of 11,675 gigawatts.[8][43] The International Energy Agency predicted in 2018 that the number of air conditioning units would grow to around 4 billion units by 2050 and that the total cooling capacity would grow to around 23,000 GW, with the biggest increases in India and China.[8] Between 1995 and 2004, the proportion of urban households in China with air conditioners increased from 8% to 70%.[44] As of 2015, nearly 100 million homes, or about 87% of US households, had air conditioning systems.[45] In 2019, it was estimated that 90% of new single-family homes constructed in the US included air conditioning (ranging from 99% in the South to 62% in the West).[46][47]

Operation

[edit]

Operating principles

[edit]
A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor

Cooling in traditional air conditioner systems is accomplished using the vapor-compression cycle, which uses a refrigerant's forced circulation and phase change between gas and liquid to transfer heat.[48][49] The vapor-compression cycle can occur within a unitary, or packaged piece of equipment; or within a chiller that is connected to terminal cooling equipment (such as a fan coil unit in an air handler) on its evaporator side and heat rejection equipment such as a cooling tower on its condenser side. An air source heat pump shares many components with an air conditioning system, but includes a reversing valve, which allows the unit to be used to heat as well as cool a space.[50]

Air conditioning equipment will reduce the absolute humidity of the air processed by the system if the surface of the evaporator coil is significantly cooler than the dew point of the surrounding air. An air conditioner designed for an occupied space will typically achieve a 30% to 60% relative humidity in the occupied space.[51]

Most modern air-conditioning systems feature a dehumidification cycle during which the compressor runs. At the same time, the fan is slowed to reduce the evaporator temperature and condense more water. A dehumidifier uses the same refrigeration cycle but incorporates both the evaporator and the condenser into the same air path; the air first passes over the evaporator coil, where it is cooled[52] and dehumidified before passing over the condenser coil, where it is warmed again before it is released back into the room.[citation needed]

Free cooling can sometimes be selected when the external air is cooler than the internal air. Therefore, the compressor does not need to be used, resulting in high cooling efficiencies for these times. This may also be combined with seasonal thermal energy storage.[53]

Heating

[edit]

Some air conditioning systems can reverse the refrigeration cycle and act as an air source heat pump, thus heating instead of cooling the indoor environment. They are also commonly referred to as "reverse cycle air conditioners". The heat pump is significantly more energy-efficient than electric resistance heating, because it moves energy from air or groundwater to the heated space and the heat from purchased electrical energy. When the heat pump is in heating mode, the indoor evaporator coil switches roles and becomes the condenser coil, producing heat. The outdoor condenser unit also switches roles to serve as the evaporator and discharges cold air (colder than the ambient outdoor air).

Most air source heat pumps become less efficient in outdoor temperatures lower than 4 °C or 40 °F.[54] This is partly because ice forms on the outdoor unit's heat exchanger coil, which blocks air flow over the coil. To compensate for this, the heat pump system must temporarily switch back into the regular air conditioning mode to switch the outdoor evaporator coil back to the condenser coil, to heat up and defrost. Therefore, some heat pump systems will have electric resistance heating in the indoor air path that is activated only in this mode to compensate for the temporary indoor air cooling, which would otherwise be uncomfortable in the winter.

Newer models have improved cold-weather performance, with efficient heating capacity down to −14 °F (−26 °C).[55][54][56] However, there is always a chance that the humidity that condenses on the heat exchanger of the outdoor unit could freeze, even in models that have improved cold-weather performance, requiring a defrosting cycle to be performed.

The icing problem becomes much more severe with lower outdoor temperatures, so heat pumps are sometimes installed in tandem with a more conventional form of heating, such as an electrical heater, a natural gas, heating oil, or wood-burning fireplace or central heating, which is used instead of or in addition to the heat pump during harsher winter temperatures. In this case, the heat pump is used efficiently during milder temperatures, and the system is switched to the conventional heat source when the outdoor temperature is lower.

Performance

[edit]

The coefficient of performance (COP) of an air conditioning system is a ratio of useful heating or cooling provided to the work required.[57][58] Higher COPs equate to lower operating costs. The COP usually exceeds 1; however, the exact value is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions.[59] Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration", with each approximately equal to the cooling power of one short ton (2,000 pounds (910 kg) of ice melting in a 24-hour period. The value is equal to 12,000 BTUIT per hour, or 3,517 watts.[60] Residential central air systems are usually from 1 to 5 tons (3.5 to 18 kW) in capacity.[citation needed]

The efficiency of air conditioners is often rated by the seasonal energy efficiency ratio (SEER), which is defined by the Air Conditioning, Heating and Refrigeration Institute in its 2008 standard AHRI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment.[61] A similar standard is the European seasonal energy efficiency ratio (ESEER).[citation needed]

Efficiency is strongly affected by the humidity of the air to be cooled. Dehumidifying the air before attempting to cool it can reduce subsequent cooling costs by as much as 90 percent. Thus, reducing dehumidifying costs can materially affect overall air conditioning costs.[62]

Control system

[edit]

Wireless remote control

[edit]
A wireless remote controller
The infrared transmitting LED on the remote
The infrared receiver on the air conditioner

This type of controller uses an infrared LED to relay commands from a remote control to the air conditioner. The output of the infrared LED (like that of any infrared remote) is invisible to the human eye because its wavelength is beyond the range of visible light (940 nm). This system is commonly used on mini-split air conditioners because it is simple and portable. Some window and ducted central air conditioners uses it as well.

Wired controller

[edit]
Several wired controllers (Indonesia, 2024)

A wired controller, also called a "wired thermostat," is a device that controls an air conditioner by switching heating or cooling on or off. It uses different sensors to measure temperatures and actuate control operations. Mechanical thermostats commonly use bimetallic strips, converting a temperature change into mechanical displacement, to actuate control of the air conditioner. Electronic thermostats, instead, use a thermistor or other semiconductor sensor, processing temperature change as electronic signals to control the air conditioner.

These controllers are usually used in hotel rooms because they are permanently installed into a wall and hard-wired directly into the air conditioner unit, eliminating the need for batteries.

Types

[edit]
 
Types Typical Capacity* Air supply Mounting Typical application
Mini-split small – large Direct Wall Residential
Window very small – small Direct Window Residential
Portable very small – small Direct / Ducted Floor Residential, remote areas
Ducted (individual) small – very large Ducted Ceiling Residential, commercial
Ducted (central) medium – very large Ducted Ceiling Residential, commercial
Ceiling suspended medium – large Direct Ceiling Commercial
Cassette medium – large Direct / Ducted Ceiling Commercial
Floor standing medium – large Direct / Ducted Floor Commercial
Packaged very large Direct / Ducted Floor Commercial
Packaged RTU (Rooftop Unit) very large Ducted Rooftop Commercial

* where the typical capacity is in kilowatt as follows:

  • very small: <1.5 kW
  • small: 1.5–3.5 kW
  • medium: 4.2–7.1 kW
  • large: 7.2–14 kW
  • very large: >14 kW

Mini-split and multi-split systems

[edit]
Evaporator, indoor unit, or terminal, side of a ductless split-type air conditioner

Ductless systems (often mini-split, though there are now ducted mini-split) typically supply conditioned and heated air to a single or a few rooms of a building, without ducts and in a decentralized manner.[63] Multi-zone or multi-split systems are a common application of ductless systems and allow up to eight rooms (zones or locations) to be conditioned independently from each other, each with its indoor unit and simultaneously from a single outdoor unit.

The first mini-split system was sold in 1961 by Toshiba in Japan, and the first wall-mounted mini-split air conditioner was sold in 1968 in Japan by Mitsubishi Electric, where small home sizes motivated their development. The Mitsubishi model was the first air conditioner with a cross-flow fan.[64][65][66] In 1969, the first mini-split air conditioner was sold in the US.[67] Multi-zone ductless systems were invented by Daikin in 1973, and variable refrigerant flow systems (which can be thought of as larger multi-split systems) were also invented by Daikin in 1982. Both were first sold in Japan.[68] Variable refrigerant flow systems when compared with central plant cooling from an air handler, eliminate the need for large cool air ducts, air handlers, and chillers; instead cool refrigerant is transported through much smaller pipes to the indoor units in the spaces to be conditioned, thus allowing for less space above dropped ceilings and a lower structural impact, while also allowing for more individual and independent temperature control of spaces. The outdoor and indoor units can be spread across the building.[69] Variable refrigerant flow indoor units can also be turned off individually in unused spaces.[citation needed] The lower start-up power of VRF's DC inverter compressors and their inherent DC power requirements also allow VRF solar-powered heat pumps to be run using DC-providing solar panels.

Ducted central systems

[edit]

Split-system central air conditioners consist of two heat exchangers, an outside unit (the condenser) from which heat is rejected to the environment and an internal heat exchanger (the evaporator, or Fan Coil Unit, FCU) with the piped refrigerant being circulated between the two. The FCU is then connected to the spaces to be cooled by ventilation ducts.[70] Floor standing air conditioners are similar to this type of air conditioner but sit within spaces that need cooling.

Central plant cooling

[edit]
Industrial air conditioners on top of the shopping mall Passage in Linz, Austria

Large central cooling plants may use intermediate coolant such as chilled water pumped into air handlers or fan coil units near or in the spaces to be cooled which then duct or deliver cold air into the spaces to be conditioned, rather than ducting cold air directly to these spaces from the plant, which is not done due to the low density and heat capacity of air, which would require impractically large ducts. The chilled water is cooled by chillers in the plant, which uses a refrigeration cycle to cool water, often transferring its heat to the atmosphere even in liquid-cooled chillers through the use of cooling towers. Chillers may be air- or liquid-cooled.[71][72]

Portable units

[edit]

A portable system has an indoor unit on wheels connected to an outdoor unit via flexible pipes, similar to a permanently fixed installed unit (such as a ductless split air conditioner).

Hose systems, which can be monoblock or air-to-air, are vented to the outside via air ducts. The monoblock type collects the water in a bucket or tray and stops when full. The air-to-air type re-evaporates the water, discharges it through the ducted hose, and can run continuously. Many but not all portable units draw indoor air and expel it outdoors through a single duct, negatively impacting their overall cooling efficiency.

Many portable air conditioners come with heat as well as a dehumidification function.[73]

Window unit and packaged terminal

[edit]
Through-the-wall PTAC units, University Motor Inn, Philadelphia

The packaged terminal air conditioner (PTAC), through-the-wall, and window air conditioners are similar. These units are installed on a window frame or on a wall opening. The unit usually has an internal partition separating its indoor and outdoor sides, which contain the unit's condenser and evaporator, respectively. PTAC systems may be adapted to provide heating in cold weather, either directly by using an electric strip, gas, or other heaters, or by reversing the refrigerant flow to heat the interior and draw heat from the exterior air, converting the air conditioner into a heat pump. They may be installed in a wall opening with the help of a special sleeve on the wall and a custom grill that is flush with the wall and window air conditioners can also be installed in a window, but without a custom grill.[74]

Packaged air conditioner

[edit]

Packaged air conditioners (also known as self-contained units)[75][76] are central systems that integrate into a single housing all the components of a split central system, and deliver air, possibly through ducts, to the spaces to be cooled. Depending on their construction they may be outdoors or indoors, on roofs (rooftop units),[77][78] draw the air to be conditioned from inside or outside a building and be water or air-cooled. Often, outdoor units are air-cooled while indoor units are liquid-cooled using a cooling tower.[70][79][80][81][82][83]

Types of compressors

[edit]
 
Compressor types Common applications Typical capacity Efficiency Durability Repairability
Reciprocating Refrigerator, Walk-in freezer, portable air conditioners small – large very low (small capacity)

medium (large capacity)

very low medium
Rotary vane Residential mini splits small low low easy
Scroll Commercial and central systems, VRF medium medium medium easy
Rotary screw Commercial chiller medium – large medium medium hard
Centrifugal Commercial chiller very large medium high hard
Maglev Centrifugal Commercial chiller very large high very high very hard

Reciprocating

[edit]

This compressor consists of a crankcase, crankshaft, piston rod, piston, piston ring, cylinder head and valves. [citation needed]

Scroll

[edit]

This compressor uses two interleaving scrolls to compress the refrigerant.[84] it consists of one fixed and one orbiting scrolls. This type of compressor is more efficient because it has 70 percent less moving parts than a reciprocating compressor. [citation needed]

Screw

[edit]

This compressor use two very closely meshing spiral rotors to compress the gas. The gas enters at the suction side and moves through the threads as the screws rotate. The meshing rotors force the gas through the compressor, and the gas exits at the end of the screws. The working area is the inter-lobe volume between the male and female rotors. It is larger at the intake end, and decreases along the length of the rotors until the exhaust port. This change in volume is the compression. [citation needed]

Capacity modulation technologies

[edit]

There are several ways to modulate the cooling capacity in refrigeration or air conditioning and heating systems. The most common in air conditioning are: on-off cycling, hot gas bypass, use or not of liquid injection, manifold configurations of multiple compressors, mechanical modulation (also called digital), and inverter technology. [citation needed]

Hot gas bypass

[edit]

Hot gas bypass involves injecting a quantity of gas from discharge to the suction side. The compressor will keep operating at the same speed, but due to the bypass, the refrigerant mass flow circulating with the system is reduced, and thus the cooling capacity. This naturally causes the compressor to run uselessly during the periods when the bypass is operating. The turn down capacity varies between 0 and 100%.[85]

Manifold configurations

[edit]

Several compressors can be installed in the system to provide the peak cooling capacity. Each compressor can run or not in order to stage the cooling capacity of the unit. The turn down capacity is either 0/33/66 or 100% for a trio configuration and either 0/50 or 100% for a tandem.[citation needed]

Mechanically modulated compressor

[edit]

This internal mechanical capacity modulation is based on periodic compression process with a control valve, the two scroll set move apart stopping the compression for a given time period. This method varies refrigerant flow by changing the average time of compression, but not the actual speed of the motor. Despite an excellent turndown ratio – from 10 to 100% of the cooling capacity, mechanically modulated scrolls have high energy consumption as the motor continuously runs.[citation needed]

Variable-speed compressor

[edit]

This system uses a variable-frequency drive (also called an Inverter) to control the speed of the compressor. The refrigerant flow rate is changed by the change in the speed of the compressor. The turn down ratio depends on the system configuration and manufacturer. It modulates from 15 or 25% up to 100% at full capacity with a single inverter from 12 to 100% with a hybrid tandem. This method is the most efficient way to modulate an air conditioner's capacity. It is up to 58% more efficient than a fixed speed system.[citation needed]

Impact

[edit]

Health effects

[edit]
Rooftop condenser unit fitted on top of an Osaka Municipal Subway 10 series subway carriage. Air conditioning has become increasingly prevalent on public transport vehicles as a form of climate control, and to ensure passenger comfort and drivers' occupational safety and health.

In hot weather, air conditioning can prevent heat stroke, dehydration due to excessive sweating, electrolyte imbalance, kidney failure, and other issues due to hyperthermia.[8][86] Heat waves are the most lethal type of weather phenomenon in the United States.[87][88] A 2020 study found that areas with lower use of air conditioning correlated with higher rates of heat-related mortality and hospitalizations.[89] The August 2003 France heatwave resulted in approximately 15,000 deaths, where 80% of the victims were over 75 years old. In response, the French government required all retirement homes to have at least one air-conditioned room at 25 °C (77 °F) per floor during heatwaves.[8]

Air conditioning (including filtration, humidification, cooling and disinfection) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where proper atmosphere is critical to patient safety and well-being. It is sometimes recommended for home use by people with allergies, especially mold.[90][91] However, poorly maintained water cooling towers can promote the growth and spread of microorganisms such as Legionella pneumophila, the infectious agent responsible for Legionnaires' disease. As long as the cooling tower is kept clean (usually by means of a chlorine treatment), these health hazards can be avoided or reduced. The state of New York has codified requirements for registration, maintenance, and testing of cooling towers to protect against Legionella.[92]

Economic effects

[edit]

First designed to benefit targeted industries such as the press as well as large factories, the invention quickly spread to public agencies and administrations with studies with claims of increased productivity close to 24% in places equipped with air conditioning.[93]

Air conditioning caused various shifts in demography, notably that of the United States starting from the 1970s. In the US, the birth rate was lower in the spring than during other seasons until the 1970s but this difference then declined since then.[94] As of 2007, the Sun Belt contained 30% of the total US population while it was inhabited by 24% of Americans at the beginning of the 20th century.[95] Moreover, the summer mortality rate in the US, which had been higher in regions subject to a heat wave during the summer, also evened out.[7]

The spread of the use of air conditioning acts as a main driver for the growth of global demand of electricity.[96] According to a 2018 report from the International Energy Agency (IEA), it was revealed that the energy consumption for cooling in the United States, involving 328 million Americans, surpasses the combined energy consumption of 4.4 billion people in Africa, Latin America, the Middle East, and Asia (excluding China).[8] A 2020 survey found that an estimated 88% of all US households use AC, increasing to 93% when solely looking at homes built between 2010 and 2020.[97]

Environmental effects

[edit]
Air conditioner farm in the facade of a building in Singapore

Space cooling including air conditioning accounted globally for 2021 terawatt-hours of energy usage in 2016 with around 99% in the form of electricity, according to a 2018 report on air-conditioning efficiency by the International Energy Agency.[8] The report predicts an increase of electricity usage due to space cooling to around 6200 TWh by 2050,[8][98] and that with the progress currently seen, greenhouse gas emissions attributable to space cooling will double: 1,135 million tons (2016) to 2,070 million tons.[8] There is some push to increase the energy efficiency of air conditioners. United Nations Environment Programme (UNEP) and the IEA found that if air conditioners could be twice as effective as now, 460 billion tons of GHG could be cut over 40 years.[99] The UNEP and IEA also recommended legislation to decrease the use of hydrofluorocarbons, better building insulation, and more sustainable temperature-controlled food supply chains going forward.[99]

Refrigerants have also caused and continue to cause serious environmental issues, including ozone depletion and climate change, as several countries have not yet ratified the Kigali Amendment to reduce the consumption and production of hydrofluorocarbons.[100] CFCs and HCFCs refrigerants such as R-12 and R-22, respectively, used within air conditioners have caused damage to the ozone layer,[101] and hydrofluorocarbon refrigerants such as R-410A and R-404A, which were designed to replace CFCs and HCFCs, are instead exacerbating climate change.[102] Both issues happen due to the venting of refrigerant to the atmosphere, such as during repairs. HFO refrigerants, used in some if not most new equipment, solve both issues with an ozone damage potential (ODP) of zero and a much lower global warming potential (GWP) in the single or double digits vs. the three or four digits of hydrofluorocarbons.[103]

Hydrofluorocarbons would have raised global temperatures by around 0.3–0.5 °C (0.5–0.9 °F) by 2100 without the Kigali Amendment. With the Kigali Amendment, the increase of global temperatures by 2100 due to hydrofluorocarbons is predicted to be around 0.06 °C (0.1 °F).[104]

Alternatives to continual air conditioning include passive cooling, passive solar cooling, natural ventilation, operating shades to reduce solar gain, using trees, architectural shades, windows (and using window coatings) to reduce solar gain.[citation needed]

Social effects

[edit]

Socioeconomic groups with a household income below around $10,000 tend to have a low air conditioning adoption,[42] which worsens heat-related mortality.[7] The lack of cooling can be hazardous, as areas with lower use of air conditioning correlate with higher rates of heat-related mortality and hospitalizations.[89] Premature mortality in NYC is projected to grow between 47% and 95% in 30 years, with lower-income and vulnerable populations most at risk.[89] Studies on the correlation between heat-related mortality and hospitalizations and living in low socioeconomic locations can be traced in Phoenix, Arizona,[105] Hong Kong,[106] China,[106] Japan,[107] and Italy.[108][109] Additionally, costs concerning health care can act as another barrier, as the lack of private health insurance during a 2009 heat wave in Australia, was associated with heat-related hospitalization.[109]

Disparities in socioeconomic status and access to air conditioning are connected by some to institutionalized racism, which leads to the association of specific marginalized communities with lower economic status, poorer health, residing in hotter neighborhoods, engaging in physically demanding labor, and experiencing limited access to cooling technologies such as air conditioning.[109] A study overlooking Chicago, Illinois, Detroit, and Michigan found that black households were half as likely to have central air conditioning units when compared to their white counterparts.[110] Especially in cities, Redlining creates heat islands, increasing temperatures in certain parts of the city.[109] This is due to materials heat-absorbing building materials and pavements and lack of vegetation and shade coverage.[111] There have been initiatives that provide cooling solutions to low-income communities, such as public cooling spaces.[8][111]

Other techniques

[edit]

Buildings designed with passive air conditioning are generally less expensive to construct and maintain than buildings with conventional HVAC systems with lower energy demands.[112] While tens of air changes per hour, and cooling of tens of degrees, can be achieved with passive methods, site-specific microclimate must be taken into account, complicating building design.[12]

Many techniques can be used to increase comfort and reduce the temperature in buildings. These include evaporative cooling, selective shading, wind, thermal convection, and heat storage.[113]

Passive ventilation

[edit]
The ventilation system of a regular earthship
Dogtrot houses are designed to maximise natural ventilation.
A roof turbine ventilator, colloquially known as a 'Whirly Bird' is an application of wind driven ventilation.

Passive ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural forces.

There are two types of natural ventilation occurring in buildings: wind driven ventilation and buoyancy-driven ventilation. Wind driven ventilation arises from the different pressures created by wind around a building or structure, and openings being formed on the perimeter which then permit flow through the building. Buoyancy-driven ventilation occurs as a result of the directional buoyancy force that results from temperature differences between the interior and exterior.[114]

Since the internal heat gains which create temperature differences between the interior and exterior are created by natural processes, including the heat from people, and wind effects are variable, naturally ventilated buildings are sometimes called "breathing buildings".

Passive cooling

[edit]
 
A traditional Iranian solar cooling design using a wind tower

Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption.[115][116] This approach works either by preventing heat from entering the interior (heat gain prevention) or by removing heat from the building (natural cooling).[117]

Natural cooling utilizes on-site energy, available from the natural environment, combined with the architectural design of building components (e.g. building envelope), rather than mechanical systems to dissipate heat.[118] Therefore, natural cooling depends not only on the architectural design of the building but on how the site's natural resources are used as heat sinks (i.e. everything that absorbs or dissipates heat). Examples of on-site heat sinks are the upper atmosphere (night sky), the outdoor air (wind), and the earth/soil.

Passive cooling is an important tool for design of buildings for climate change adaptation – reducing dependency on energy-intensive air conditioning in warming environments.[119][120]
A pair of short windcatchers (malqaf) used in traditional architecture; wind is forced down on the windward side and leaves on the leeward side (cross-ventilation). In the absence of wind, the circulation can be driven with evaporative cooling in the inlet (which is also designed to catch dust). In the center, a shuksheika (roof lantern vent), used to shade the qa'a below while allowing hot air rise out of it (stack effect).[11]

Daytime radiative cooling

[edit]
Passive daytime radiative cooling (PDRC) surfaces are high in solar reflectance and heat emittance, cooling with zero energy use or pollution.[121]

Passive daytime radiative cooling (PDRC) surfaces reflect incoming solar radiation and heat back into outer space through the infrared window for cooling during the daytime. Daytime radiative cooling became possible with the ability to suppress solar heating using photonic structures, which emerged through a study by Raman et al. (2014).[122] PDRCs can come in a variety of forms, including paint coatings and films, that are designed to be high in solar reflectance and thermal emittance.[121][123]

PDRC applications on building roofs and envelopes have demonstrated significant decreases in energy consumption and costs.[123] In suburban single-family residential areas, PDRC application on roofs can potentially lower energy costs by 26% to 46%.[124] PDRCs are predicted to show a market size of ~$27 billion for indoor space cooling by 2025 and have undergone a surge in research and development since the 2010s.[125][126]

Fans

[edit]

Hand fans have existed since prehistory. Large human-powered fans built into buildings include the punkah.

The 2nd-century Chinese inventor Ding Huan of the Han dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered by prisoners.[127]: 99, 151, 233  In 747, Emperor Xuanzong (r. 712–762) of the Tang dynasty (618–907) had the Cool Hall (Liang Dian 涼殿) built in the imperial palace, which the Tang Yulin describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song dynasty (960–1279), written sources mentioned the air conditioning rotary fan as even more widely used.[127]: 134, 151 

Thermal buffering

[edit]

In areas that are cold at night or in winter, heat storage is used. Heat may be stored in earth or masonry; air is drawn past the masonry to heat or cool it.[13]

In areas that are below freezing at night in winter, snow and ice can be collected and stored in ice houses for later use in cooling.[13] This technique is over 3,700 years old in the Middle East.[128] Harvesting outdoor ice during winter and transporting and storing for use in summer was practiced by wealthy Europeans in the early 1600s,[15] and became popular in Europe and the Americas towards the end of the 1600s.[129] This practice was replaced by mechanical compression-cycle icemakers.

Evaporative cooling

[edit]
An evaporative cooler

In dry, hot climates, the evaporative cooling effect may be used by placing water at the air intake, such that the draft draws air over water and then into the house. For this reason, it is sometimes said that the fountain, in the architecture of hot, arid climates, is like the fireplace in the architecture of cold climates.[11] Evaporative cooling also makes the air more humid, which can be beneficial in a dry desert climate.[130]

Evaporative coolers tend to feel as if they are not working during times of high humidity, when there is not much dry air with which the coolers can work to make the air as cool as possible for dwelling occupants. Unlike other types of air conditioners, evaporative coolers rely on the outside air to be channeled through cooler pads that cool the air before it reaches the inside of a house through its air duct system; this cooled outside air must be allowed to push the warmer air within the house out through an exhaust opening such as an open door or window.[131]

See also

[edit]

References

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Frequently Asked Questions

Poor ventilation restricts airflow, causing the AC system to work harder to circulate air throughout a space. This can lead to increased energy consumption and reduced efficiency as the unit struggles to maintain desired temperatures.
Common signs include uneven cooling or heating, increased energy bills, frequent cycling on and off of the AC unit, and hot or cold spots in different areas of your home.
Restricted airflow forces the AC components, particularly the blower motor and compressor, to operate under stress. Over time, this extra strain can lead to overheating, component failure, and costly repairs or replacements.
To improve ventilation, ensure air vents are open and unblocked by furniture or debris. Regularly replace air filters, schedule routine maintenance checks for ductwork leaks or obstructions, and consider installing exhaust fans or additional vents if needed.