Both industrial refrigeration and air-conditioning are based on the same mechanism: a fluid, generally water or air, is cooled by evaporation of another fluid, called the refrigerant. The refrigerant circuit, comprising the compressor, evaporator, condenser and expansion device, is an integral part of both systems. Nonetheless, there are substantial differences between refrigeration and air-conditioning systems, for example as regards the components, the design methods, the commercial or industrial structures where they're installed and their operation, such as to justify the existence of two distinct market sectors.
Air-conditioning is that process used to create and maintain certain temperature, relative humidity and air purity conditions in indoor spaces. This process is typically applied to maintain a level of personal comfort.
It's also used in industrial applications to ensure correct operation of equipment or machinery that need to operate in specific environmental conditions or alternatively to be able to carry out certain industrial processes, such as welding, which produce considerable amounts of heat that needs to be disposed of in some manner.
An air-conditioning system must be effective regardless of outside climatic conditions and involves control over four fundamental variables: air temperature, humidity, movement and quality.
The distinction between industrial and personal comfort applications is not always clear cut. Industrial air-conditioning usually requires better precision as regards temperature and humidity control. Some application also demand a high degree of filtering and removal of contaminants.
Comfort air-conditioning on the other hand, as well as needing to satisfy personal temperature-humidity requirements, also involves other fields such as architectural design, weather forecasting, energy consumption and sound emissions to recreate the ideal conditions for human psychophysiological well-being.
The main process underlying air-conditioning is the exchange of heat and water vapour between the indoor and outdoor environments and the people inside the air-conditioned space.
The principal appliances used in home and industrial air-conditioning are:
- Packaged, split or multi-split air-conditioners for home use;
- Residential heat pumps;
- Air handling units for medium/large spaces;
- Rooftop units, air handling units for small spaces;
- Shelter units, air-conditioner for telephone exchanges;
- Industrial chillers and heat pumps, units that produce chilled or hot water that's then used air-condition the environment or equipment;
- Close control units, precision cooling units for servers or telecoms equipment;
- Fan coils and hydronic systems, systems using chilled water circuits and terminal units for air-conditioning buildings.
These differ significantly in terms of size, complexity and cooling capacity, which may range from several hundred watts into the megawatts, components and in general which of the main air-conditioning functions are implemented, i.e.:
- Cooling of air or water;
- Heating of air or water;
- Air dehumidification;
- Air humidification;
- Air filtering/purification;
- Mixing of air indoor/outside air;
Home air-conditioners, for example, mainly cool the air taken in from the air-conditioned space in a closed circuit. Such cooling also dehumidifies the air as some of the moisture this contains condenses inside the air-conditioner (in the form of droplets) and is then collected and discharged outside via a rubber hose.
Close control units, on the other hand, being designed for critical environments housing servers or telecoms equipment, need to manage air temperature and humidity over a very limited range, and therefore not only cool and dehumidify the air but also apply fine temperature and humidity control using electric heaters and humidifiers.
More complex air handling units include all the functions described above, usually housed in separate compartments.
Chillers handle water rather than air, which is cooled to a temperature around 0°C (or lower if mixed with antifreeze) or heated by reversing the refrigeration cycle.
The ventilation, filtering, mixing and often heating functions are managed using relatively simple dedicated components, respectively fans, filters, dampers and electric heaters or boilers, while the principle and more complex functions are managed by likewise complex systems such as refrigerant circuits and humidifiers (see "MAKING IT COLD (AND HOT)" and "HUMIDIFICATION").
Special mention also needs to be made of the solution commonly used to deliver cooling capacity that exploits the evaporation of a fluid inside a circuit placed in contact with the environment being cooled. The principles underlying this technology are again quite complex.
Vifaa vya baridi na vyenye hewa ya kawaida hutegemea utaratibu uleule: kioevu, kwa kawaida maji au hewa, hufanyiwa baridi kwa kuvumilia kwa kioevu kingine, kinachoitwa kichocheo. Mzunguko wa baridi, unaojumuisha compressor, evaporator, condenser na kifaa cha upanuzi, ni sehemu muhimu ya mifumo yote miwili. Hata hivyo, kuna tofauti kubwa kati ya mifumo ya baridi na hali ya hewa, kwa mfano, kwa upande wa vipengele, mbinu za kubuni, miundo ya kibiashara au viwanda ambapo zimewekwa na utendaji wao, kama vile kuhalalisha kuwepo kwa sekta mbili tofauti za soko. Uingizaji hewa ni mchakato unaotumiwa kuunda na kudumisha hali fulani ya joto, unyevu wa jamaa na usafi wa hewa katika nafasi za ndani. Utaratibu huu ni kawaida kutumika kudumisha kiwango cha starehe ya kibinafsi. Pia hutumiwa katika matumizi ya viwanda kuhakikisha uendeshaji sahihi wa vifaa au mashine ambazo zinahitaji kufanya kazi katika hali maalum za mazingira au mbadala kuweza kutekeleza michakato fulani ya viwanda, kama vile kulehemu, ambayo hutengeneza kiasi kikubwa cha joto ambalo linahitaji kuondolewa kwa njia fulani. Mfumo wa hali ya hewa lazima uwe na ufanisi bila kujali hali ya hewa ya nje na inahusisha udhibiti wa vigezo vinne vya msingi: joto la hewa, unyevu, mwendo na ubora. Tofauti kati ya maombi ya viwanda na faraja ya kibinafsi si mara zote wazi. Viwanda vya kusafisha hewa kwa kawaida huhitaji usahihi bora kuhusiana na kudhibiti joto na unyevu. Baadhi ya maombi pia kudai kiwango cha juu cha kuchuja na kuondoa uchafuzi. Kwa upande mwingine, hali ya hewa ya starehe, pamoja na kuhitaji kuridhisha mahitaji ya kibinafsi ya joto na unyevu, pia inahusisha nyanja zingine kama vile muundo wa usanifu, utabiri wa hali ya hewa, matumizi ya nishati na uzalishaji wa sauti ili kuunda hali bora kwa ustawi wa kisaikolojia wa binadamu. Mchakato wa msingi wa hali ya hewa ni kubadilishana joto na mvuke wa maji kati ya mazingira ya ndani na nje na watu ndani ya nafasi ya hali ya hewa. - Vifaa vya msingi kutumika katika nyumba na viwanda air-conditioning ni: - Packaged, kugawanyika au multi-kugawanyika air-conditioners kwa ajili ya matumizi ya nyumbani; - Residential pampu za joto; - Air matibabu vitengo kwa ajili ya nafasi ya kati au kubwa; - paa vitengo, vifaa vya hewa matibabu kwa ajili ya nafasi ndogo; - Shelter vitengo, air-conditioners kwa ajili ya vituo vya simu; - viwanda chillers na pampu za joto, vitengo kwamba kuzalisha maji baridi au moto ambayo ni kisha kutumika air-conditioning mazingira au vifaa; - karibu kudhibiti vitengo vya baridi kwa ajili ya vifaa au vifaa vya mawasiliano. Hii ni tofauti kubwa katika suala la ukubwa, utata na uwezo wa baridi, ambayo inaweza kuanzia mia kadhaa ya watts hadi megawatts, vipengele na kwa ujumla ambayo ya kazi kuu ya hali ya hewa ni kutekelezwa. - Kupumzika hewa au maji; - Kupumzika hewa au maji; - Dehumidification hewa; - Humidification hewa; - Uchujaji hewa; - Mchanganyiko wa hewa ya ndani na nje; Nyumba air-conditioners, kwa mfano, hasa baridi hewa kuchukuliwa katika kutoka nafasi air-conditioned katika mzunguko uliofungwa. Baridi kama hiyo pia huondoa unyevu wa hewa kwani baadhi ya unyevu unao ndani ya kiyoyozi (kwa namna ya matone) na kisha hukusanywa na kutolewa nje kupitia mfereji wa mpira. Vifaa vya kudhibiti karibu, kwa upande mwingine, vinavyoundwa kwa mazingira muhimu ya nyumba, seva au vifaa vya mawasiliano ya simu, zinahitaji kusimamia joto la hewa na unyevu katika safu ndogo sana, na kwa hivyo sio tu baridi na dehumidify hewa, lakini pia kutumia joto la hali ya juu na unyevu wa joto kwa kutumia heater za umeme na humidifiers. Vifaa vya utunzaji wa hewa tata zaidi ni pamoja na kazi zote zilizoelezwa hapo juu, kwa kawaida ziko katika sehemu tofauti. Chillers kushughulikia maji badala ya hewa, ambayo ni baridi kwa joto karibu 0 ° C (au chini kama mchanganyiko na antifreeze) au joto kwa kugeuka mzunguko baridi. Ventilation, filtration, na kuchanganya kazi ni kusimamiwa kwa kutumia vipengele vya kawaida, kama vile mashabiki, filters, dampers na boilers umeme, wakati kanuni na kazi ngumu zaidi ni kusimamiwa na mifumo kama vile mifumo ya baridi na humidifiers (tazama "KUFANYA COLD (NA HOT) na HUMIDIFICATION"). Maelezo maalum pia yanahitaji kufanywa ya ufumbuzi kawaida kutumika kutoa uwezo baridi ambayo exploits evaporation ya kioevu ndani ya mzunguko kuwekwa katika kuwasiliana na mazingira kuwa baridi. Kanuni zinazotokana na teknolojia hii ni ngumu sana.