TB-9-2320-279-13-1

TB-9-2320-279-13-1 - Page 16 of 524

TB 9-2320-279-13-1

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GENERAL INFORMATION - Continued

DRAFT

PRINCIPLES OF OPERATION

The HEMTT AC kit is a Field Level Maintenance-installed cab air conditioning system for the HEMTT.

The kit

consists of an engine driven AC compressor, AC condenser, AC dryer, AC heater/evaporator, AC blower, and AC

hoses.

In the HEMTT AC system, the engine driven AC compressor pressurizes R-134a refrigerant gas. The pressurized

R-134a gas is then passed through the AC condenser, where it is cooled and converted to a high-pressure liquid.

The liquid R-134a is then passed through the AC dryer, where moisture is removed and the liquid R-134a is stored

until it is required by the system. When cooling is required, the high-pressure R-134a liquid is passed through the

AC expansion valve and AC evaporator, where it is converted to a low-pressure gas. This process cools the

R-134a refrigerant and AC evaporator coil. Cab air is then passed across the cooled AC evaporator coil by the AC

blower, which cools and dehumidifies the air. The cooled air is then passed back into the cab, cooling the cab. The

R-134a gas from the AC evaporator is then passed back to the AC compressor, to complete the refrigerant cycle.

END OF WORK PACKAGE

HEMAC123A