Automotive Air Conditioning System Principle
What is Air Conditioning?
•
Air conditioning is to adjust the indoor air (or air in a space)
and make its temperature, humidity, flow test and cleanness
reach the requirement of human comfort range.
•
Air conditioning has two basic working modes: cooling and
heating.
•
Air-conditioning system is widely used in various industries.
•
Automotive air conditioning system is a typical air-conditioner
structure.
Air conditioning Cooling/Dehumidification Principle
Air conditioning Heating Principle
The Classification of automotive air conditioning
•
Air conditioning is divided into two types: single function and combined
function, according to different functions.
a.
Single function means cooling and heating are separate and generally used for
large and middle-sized passengers cars.
b.
Combined function means cooling and heating use the same blower and control
mechanism, generally used for personal cars.
•
Air conditioning is divided into two types: non-independent system and
independent system, according to different drive mode.
a.
Non-independent auto air conditioning system: the compressor is driven by the
engine of
the car itself, this kind of auto air conditioning system is generally used for middl
e-sized
and small-sized cars which has relatively less cooling capacity.
Configuration of Automotive Air Conditioning System
1. Cooling system: reduce the temperature and humidity in the car
2. Heating system: increase the temperature inside the car
3. Ventilation system: realize the air flow inside and outside of the car
4. Air purification system: clean up the dust and smell in the car
5. Control system: control the operation of the whole air conditioning
system
Configuration of Automotive Air Conditioning System
1-Compressor
2-Condenser
3-Drier
4-Expansion valve
5-Blower
6-Air flow
7-Evaporator
Auto A/C Working Principle----Cooling
•
Compression process: the compressor absorb the low-temperature low-pressure
refrigerant gas at the outlet of evaporator and compress it into a high-temperature
high-pressure gas out of the compressor.
•
Exothermic process: the hot refrigerant gas of high temperature and high pressure
enter into the condenser, due to lower pressure and temperature, the refrigerant gas
condenses into liquid mixture and release considerable heat.
•
Throttling process: the volume of refrigerant liquid becomes larger through the
expansion device, then the pressure and temperature drops sharply and it excludes
from the expansion device in the state of mist (fine droplets).
•
Endothermic process: the mist of liquid refrigerant enter into the evaporator and
the liquid refrigerant evaporates into a gas since the refrigerant boiling point is much
lower than the temperature inside the evaporator. During the evaporation process it
absorbs heat around and then the low temperature and low pressure refrigerant
vapor enter into the compressor
Auto A/C Working Principle----Heating
• When we are driving in the snow or a cold environment, we can
still feel very warm thanks to the car heater system.
• In modern cars, car heater system can be divided into two kinds
according to the type of hear source: one is the engine coolant as
heat source (the vast majority of vehicles currently use), the other
is the fuel for the heat source ( small number of luxury cars used).
Auto A/C Working Principle----Heating
• The heater system with engine coolant as heat resource is widely used
due to its low cost and high heating efficiency. This kind of heater system
is combined with air conditioning system, so their operation are the same,
just need a thermostat switch.
• The system consists of a small heater water tank, blower, control device
and air channel. The working principle of heater system is: when the
engine coolant temperature is high, the cooling liquid will flow through the
heat exchanger of ventilation system (commonly known as a small heater
water tank), and the air sent by blower will exchange with engine cooling
liquid. After heating, the air is sent into the car by the blower. This heating
system is simple and reliable, without any additional fuel required, as long
as the engine works it can produce hot water. But it also has its obvious
shortcomings, the engine coolant temperature must be increased to a
certain temperature and then it can begin heating. Therefore, it’s better not
to immediately open the heater when start a car but wait till the engine idle
speed comes down. Otherwise, it does harm to the engine.