Automotive air conditioning systems
Nitin Gupta, Manish Jindgar and Ravinder Dasila, Freescale Semiconductor -December 21, 2012
Warming Ventilation and air-con (HVAC) could be the technology for indoor and automotive background convenience. HVAC facilitates in handling the pleasant environment inside the cabin by controlling the amount of hotness/coolness.
There have been times when having an air conditioning unit in a vehicle had been considered among the big functions, but these days air conditioners became standard equipment even yet in entry-level automobiles. The desire for even more comfort and luxury has led to the development of the climate control system inside an automobile. The main function of automated climate control should handle the heat of a given area when it comes to comfort of onboard passengers.
HVAC was initially introduced into automobiles during the early sixties, and it is available in almost all of the high-end cars these days. It's a complex system consisting of mechanical/electronic switches or knobs when you look at the frontend. The backend associated with system includes several blower motors, actuators (for oxygen blood circulation control, air-flow control and temperature control), and refrigeration product coupled with numerous ducts through which environment is utilized in the cabin.
The essential concept behind the operation of HVAC unit is conduction and convection. Heat is transferred from a low-temperature area to a high-temperature area in the vehicle, because of the pressure difference. This method of heat transfer is called Refrigeration. Figure 1 shows the period diagram of full refrigeration procedure.Figure 1: Refrigeration pattern drawing.
an air cooling system comprises five significant elements:
- Expansion device
The five significant elements tend to be divided in to two stress areas: the high-pressure side could be the condenser and receiver/drier device, and the low-pressure part may be the air-con evaporator. The dividing point between large and low pressure cuts through the compressor as well as the expansion device.
Here section considers at length each piece of the HVAC system (see Figure 2).Figure 2: an air conditioning system includes five significant elements.
An evaporator is a temperature change product in refrigeration pattern. The liquid refrigerant, appearing out of expansion worth and getting into the evaporator, are at lower heat and reduced pressure.
On driving through the evaporator coils refrigerant digests the heat from the air that is blown through the coils and gets transformed into low temperature, low pressure vapor. The fluid refrigerant was created to move through the base towards the the surface of the evaporator coils to make sure that fluid refrigerant boils before it makes the evaporator coils.
The jobs carried out because of the evaporator may be summarized below:
- Consumption of temperature
- Boiling of the many refrigerant to vapors
Air blown because of the blower subsequently gets cooler, on transferring the warmth, and is passed away into the cabin through the ports.
Since air cooling evaporator offers the cooling by absorbing the heat through the surrounding method, it might offer dual-purpose whenever put really near dashboard of automobile. It absorbs heat from the atmosphere that's passed away through it as well as absorbs heat from inside the car to maintain the mandatory temperature.
The air conditioning compressor is known as the center associated with the main air conditioners. The compressor absorbs vapor refrigerant through the suction line and compresses the vapors to high superheat vapor. The temperature associated with vapor is normally two-and-a-half times higher than the temperature for the outside environment.
Since heat always flows from hot to cold, the refrigerant must be a lot hotter as compared to outdoors atmosphere to move temperature from the system. Due to the fact refrigerant flows across the compressor, additionally eliminates heat of compression, motor winding heat, technical friction, alongside heat consumed into the suction line. Another crucial task regarding the ac compressor is produce the flow of refrigerant in system.
The tasks carried out by compressor can be summarized below:
- Remove latent temperature or (condense)
- Pull more sensable temperature or (subcooled)