The full form of HVAC system is “ Heating Ventilation and air conditioning or HVAC stand for Heating ventilation and air conditioning.
HAC System control the indoor environment which include temperature ,humidity ,air flow and air filtering. Basic function of HVAC system is mechanical intervention to condition the air to a preferred temperature and humidity.
Human comfort is the condition at which most people are likely feel comfortable most of the time. The standard temperature in summer is 25 C (78 F) and in winter it is 20C (68F).Relative humidity should be 30 to 60 %.Normally heat transfer occur by conduction ,convection and radiation.
Conduction; It is transfer of heat through solid matter
Convection: It is transfer of heat through liquid
Radiation: It is transfer of heat through air or gas.
Temperature will be measure in degree centigrade C in SI system and degree Fahrenheit F in IP system
Co =(Fo -32)x5/9
Fo=(Co x5/9) +32
HVAC basic components
Compressor is the heart of HVAC system .It pump the refrigerant and oil through the system. It separate the high pressure side of system from the low pressure side. If the compressor fail ,then no cooling is takes place.
The main purpose of condenser is the received the high pressure gas from the compressor and convert this gas in to liquid .In other word it cool down the incoming refrigerant gas in to liquid.The condenser can be water cooled or air cooled
The function of evaporator os covert the refrigerant in to gas by absorbing heat from the air in the compartment. When the liquid refrigerant reach in to the evaporator ,its pressure has been reduced ,dissipate heat content and make too much cooler than the fan air flowing around it. The evaporator located after the air filter in the system. Its remove moisture from air.
Evaporator fan is located in front or behind the evaporator coil. It draw ambient or mixed air across the evaporator coil.
Thermal Expansion Valve
The thermal expansion valve is located at the evaporator coil. It provide suitable amount of refrigerant to the evaporator coil for proper cooling .It separate high pressure side of the system from the low pressure side of the system.
Unit of Refrigeration
TR is the unit of refrigeration .One TR is the amount of heat extracted from the atmosphere for melting one metric ton of ice in 24 hours
1 TR=12000 BTU/Hrs
1 TR =3000 KCAl/HRS
Advantage of HVAC system
1-Temerature can be raised or lower
2-Humidity can be raised or lower
3-Maintain proper filtration of air
4-Proper air movement
5-outside air can be added and removed
6-To hold the air contamination within limits
HVAC system Application
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