Mazda TC070-15-01H, Student Manual

Page: 14 / 71

AIR CONDITIONING
SG01 - Basic System
SG01-4
TC070-15-01H
Evaporator
• The figure below shows a double-tank drawn cup.
1. Separation part
2. Rejoining point
3. Separation part
4. Rejoining point
Expansion valve
• The liquid refrigerant of about 1.5 MPa is sprayed at the expansion valve. The
splayed refrigerant is, then, expanded its volume that causes its pressure decreased
to about 0.2 MPa. This makes the refrigerant to be vaporized causing reduction of
temperature. The expansion valve regulates the flow volume of the refrigerant.
• The amount of refrigerant delivered to the evaporator is adjusted by the opening
angle of the ball valve in the expansion valve.
• Opening angle is adjusted by a balance of the R-134a pressure ( Pd ) in the
diaphragm, and a composite force of evaporator discharge pressure ( PI ) against the
lower part of the diaphragm and spring force ( Fs ) pushing up the ball valve. When
PI increases, the temperature of the temperature sensor near the diaphragm rises
and the Pd heated by the R-134a in the diaphragm increases. When the Pd
increases more than PI + Fs , the diaphragm is pushed down, and the shaft attached
to end of the temperature sensor rod pushes down the ball valve, increasing the
amount of liquid refrigerant flow. When the evaporator discharge refrigerant
temperature decreases,
PI + Fs increases more than Pd , the ball valve is pushed
up, and the amount of liquid refrigerant flow decreases.