Heating, ventilation and air conditioning are the technologies of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor quality. HVAC system design is a sub-discipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics and heat transfer.
Air conditioning is the control of the humidity and temperature of the environment and makes it comfortable and suitable for humans. And also, it changes these physical quantities as the industry specifications listed below.
- Comfortable humidity for human – 30% – 50%
- Comfortable temperature for human – 180C – 220C
Humidity Control – Regulation of the degree of saturation or quantity of water vapour in a mixture of air. Humidity is commonly mistaken as a quality of air.
Mainly there are two main categories of air conditioning as human comfort air conditioning and industrial air conditioning system.
- Human Comfort Air Conditioning Systems
The primary purpose of this air conditioning system is to bring surround air temperature of a specific area to favourable manner for humans.
Eg:- Hotels, Auditoriums, Vehicles
- Industrial Air Conditioning Systems
The applications of this type of systems are almost without limit in number and variety. Control of moisture content by controlling the recommended temperature for machinery equipment to keep them at optimum state, hygroscopic materials and govern the rate of chemical and biochemical reactions are some of the main functions of industrial air conditioning systems.
In an air conditioner, it converts the temperature of the air in a system to a favourable manner. This is done by taking the external air into the air conditioner, passing it through a heated or cooled coil and releasing the changed temperature air.
In countries close to the equator, which are not highly affected by seasonal changes, the temperature is slightly higher. So they use air conditioners for cooling. Other countries use air conditioners for both heating and cooling for respected seasonal changes.
- If the outside temperature is more than 220C air conditioners are used as coolers.
- If the outside temperature is less than 160C air conditioners are used as heaters.
Air Conditioning Cycle
All air conditioners use the same cycle of compression, condensation, expansion, and evaporation. The refrigerant comes into the condenser as a low-pressure gas. It is compressed and then moves out of the compressors at high pressure. In condenser, it is condensed and turns the gas into the liquid state of the refrigerant. Then expand in the expansion valve as it turns into the gas form of refrigerant, in the evaporator.
It is a big electric pump that works with the condenser to turn the refrigerant back to liquid. It pumps the liquid through a pipe and increases the pressure of the gas by reducing its volume (that leaves the evaporator coil) and transfers to the condenser.
It is located on the heating side of the air conditioner. It brings hot, condensed refrigerant gas back outside to vent the heat and turn the refrigerant back into liquid form. It takes heat released by the compressor and transfers to the outside.
Works with the evaporator and located between Production Planning Control and Industrial Management the evaporator and the condenser. It controls the amount of refrigerant released into the evaporator by keeping superheat.
It is the outlet of the condensed air. It takes the liquid of gas refrigerant and turns into gaseous state.
Refrigerant is a compound that is found in either fluid or gaseous state used in Production Planning Control and Industrial Management the refrigeration cycle (air conditioning cycle). In most cycles, it undergoes phase transitions from a liquid to a gas and vice-versa.
- In Condenser
- In Evaporator
There are 3 most common refrigerants used in the world for air condition systems. Because of environmental issues made by refrigerants like Global Warming potential and depletion of the Ozone layer, refrigerants were replaced by time to time.
This is a compound made with atoms of Chlorine, Fluorine and Carbon. This was used as a refrigerant in the early ‘90s and the beginning of 90’s it was banned due to environmental damage is made.
Eg:- R11, R12, R113, R114, R115.
This is the compound which was the substitute for CFC and replaced after ‘90s because it does slightly less damage to Ozone than CFC. Presence of Chlorine molecules in the HCFC it is directly affected to Ozone depletion and various other environmental issues. As a result of the Clean Air Act of 2010 EPA (Environmental Protection Agency) has mandated phase-out of HCFC and it would be phase out completely in 2020.
Eg:- R21, R22, R123
HFC contain only molecules of Chlorine, Fluorine and Carbon. No chlorine in HFC it is not harmful to the Ozone layer and safer for the environment. Air conditioners run R410A are more efficient, offer better air quality, increase comfort and improve reliability. So HFC is now being used in place of HCFC.
Eg:- R134A, R404A, R407C, R410A.
Properties of refrigerants
Generally, refrigerants have, moderate density in liquid form, the high heat of vaporisation, high density in the gaseous state and very high critical temperature.
Devices used to regulate and circulate as a part of air conditioning units.
- Domestic air coolers
- Air handlings units
- Central automotive devices
- For storage purposes.
- Eg:- Pharmaceuticals, Food, Beverages.
- To maintain the recommended temperature for machinery.
- Eg:- Printing Industry, Textile industry
- To maintain spatial temperatures.
- Eg:- Conference halls, Office rooms, Auditoriums.
- For commercial purposes.
- Eg:- Restaurants, Hotels, Cinemas.
- To make the proper atmosphere of working zones.
- Eg:- LASER Operated CNC Machining, CAD/CAM Offices and working zones.
- G.F., H., A.R., T. & T.C., W., 2016;. Refrigeration, Air Conditioning and Heat Pumps;. 5th Edition; ed. Oxford;: Butterworth-Heinemann;.
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