235 Unit 1.2

Compressor

The dual purpose of a compressor is: - Increase the temperature and pressure of refrigerant gas from the evaporator - Circulate the refrigerant throughout the system The compressor has reed valves to control the entrance and exit of refrigerant gas during the pumping operation. The compressor pressurizes the gas increasing the intensity of the heat.

Compressor and high pressure flask tank

As a liquid refrigerant boils, the vapor is drawn through a hose into the compressor. The compressor increases the pressure of the vapor and the intensity of the heat (temperature increases). The high pressure, high temperature flows into the high pressure flask. The temperature of the high pressure vapor is higher than the surrounding area. Therefore, heat flows from the high pressure vapor to the surrounding area. The high pressure vapor cools and changes into a high pressure liquid.

Compressor, High pressure flask, and connecting hose

Complete the system by adding a hose to connect the flask of high liquid to the flask of low pressure liquid. An orifice is inserted in the hose to maintain a pressure difference between the high pressure liquid and the low pressure liquid. When the flask of low pressure liquid refrigerant boils, the boiling process collects heat from the surrounding area. The low pressure refrigerant vapor is drawn through a hose into the compressor. The compressor raises the pressure and temperature of the vapor and stores it and stores it in the high pressure flask. The high pressure, high temperature vapor gives up heat to the cooler surrounding area, causing the high pressure vapor to cool and condense into a high a high pressure liquid. The high pressure liquid refrigerant flows through a hose and orifice to the flask for low pressure liquid refrigerant. The low pressure liquid refrigerant boils, and repeats the cycle.

H-block expansion valve system

In the "H" Block expansion valve system the thermostatic expansion valve is replaced with the "H" Block expansion valve. When the "H" Block expansion valve opens, liquid refrigerant is metered to the bottom of the evaporator. The low pressure refrigerant begins to boil as it flows through the evaporator coil. The refrigerant vapor attracts the heat from the warmer air circulated by the evaporator fan. The compressor draws refrigerant vapor out of the top of the evaporator and past the temperature sensor. As the temperature sensor cools, the gas in the sensor condenses and decreases y the pressure on the top of the temperature sensor diagrahm

Thermostatic Expansion valve system

Many earlier model machines are equipped with the thermostatic expansion valve system. The purpose of the Thermostatic expansion valve system is: -Restrict refrigerant flow and allow the compressor to increase the pressure on the high side of the A/C system -Control the amount of refrigerant entering the evaporator The part of the air conditioning system from the compressor outlet the expansion valve inlet is called the "high side." The thermostatic expansion valve causes a restriction to refrigerant flow that increases the pressure between the expansion valve (restriction) and the compressor. The increase in pressure allows the refrigerant to change from gas to liquid. Just as the compressor increases the temperature of the refridgerant by concentrating the refriderent into a smaller space, the expansion valve decreases the temperature by allowing the refridgerent to spread out as it leaves the orifice in the expansion valve. Because the pressure is greatly decreased, the refriderant is coldest as the refridgeration leaves the expansion valve. Because the pressure is greatly decreased, the refridgerant leaves the expansion valve and enters the evaporator. The part of the air conditioning system from the expansion valve outlet to the compressor inlet is called the "low side." The thermostatic expansion valve system is equipped with a receiver-dryer.

In-Line dryer and orifice tube

The In-line dryer contains a desiccant bag and two quick disconnects. The disconnects allows the in-line dryer to be changed without re-claiming the refrigerant. Some in-line dryers have a moisture indicator. On most orifice tube systems, the orifice tube is installed in the in-line dryer. The orifice tube consist of a small tube through the center of a plastic body, two O-rings, two screens and two tabs. The two screens (one on each end) filter the refrigerant that flows through the small tube. The two O-rings are positioned to seal against leakage past the outside of the orfice tube. The two tabs engage the tooling when installing and removing the orifice tube. The orifice tube seperates the A/C high side from the low side. High pressure liquid refrigerant enters the orifice tube and low pressure liquid refrigerant exits the orifice tube. The orifice tube has a fixed diameter and does not have the regulating capability of the expansion valve. The refrigerant flows from the orifice tube to the evaporator. The amount of liquid refridgerant entering the evaporator is usually more than the evaporator can boil off, therefore, some refridgerant will leave the evaporator in the liquid form. On some orfice tube systems, the orifice tube is installed in the evaporator inlet line.

Receiver-Dryer

The Receiver-Dryer has three functions: Dry, Store, and filter liquid refrigerant. As the high pressure liquid refrigerant flows into the receiver-dryer, the refrigerant is filtered through a desiccant that removes any moisture that may have entered the refrigerant. The refrigerant is stored until needed by the system. When the system calls for refrigerant, high pressure liquid flows through the fine mesh screen fitted on the pickup tube. High pressure liquid flows from the receiver-dryer to the thermostatic expansion valve.

Accumulator

The accumulator stores the refrigerant gas/liquid mixture and allows only the gas refrigerant to flow to the compressor. The refrigerant gas flows through the opening at the top of the vapor line. Earlier accumulators contain a diverter cap to keep a liquid away from the opening vapor line. The oil bleed hole allows oil to flow back to the compressor. Some accumulators contain a desiccant bag to remove moisture from the refrigerant. On systems with a in-line-dryer, the desiccant is removed from the accumulator and placed in the in-line dryer.

Basic air conditioning system

The heat in the room causes refrigerant to boil. As refrigerant boils, heat is drawn away from the surrounding area. The absence of heat makes the surrounding area cooler.

Condenser

The purpose of the condenser is to transfer the heat in refrigerant gas to the to the atmosphere and convert the refrigerant gas into a liquid. High pressure, high temperature refrigerant gas flows from the compressor into the condenser. As the hot, high pressure gas flows through the condenser, heat flows from the hot gas to the cooler air through the condenser coils. The high pressure refrigerant gas cools and condenses into high pressure liquid. The high pressure liquid flows from the condenser to the in-line dryer. Two basic types of condensers are commonly used: -Ram Air, used in automotive applications The Ram air condenser depends on machine movement to force large volumes of air through the condenser coils. -Forced Air, used on construction equipment The forced air condenser uses fans to move large volumes of air through the condenser coils. The air is cooler than the refrigerant gas inside the condenser. Heat flows from the hot refrigerant gas to the cooler air.

Evaporator unit

The purpose of the evaporator unit is to transfer the heat in the operators compartment to the refrigerant in the air conditioner. A blower fan is a necessary part of the evaporator unit in the air conditioning system. The blower fan draws heat laden air from the operators compartment over the evaporator fins and coils where the air surrenders heat to the refrigerant. When the low pressure liquid refrigerant enters the evaporator, the refrigerant is cooler than the air from the blower fan. The heat in the air causes most of the low pressure liquid refrigerant to boil and change into refrigerant gas The heat laden low pressure refrigerant gas/liquid combination flows to the accumulator. The cooler air flows back into the operators compartment.

Orifice Tube System

The standard Orifice tube A/C system contains five different components. -Compressor, Increases pressure and temperature of refrigerant vapor. -Condenser, Removes the heat from the high pressure/high temperature refrigerant vapor causing the vapor to change into high pressure liquid refrigerant. -In-line dryer, Contains the desiccant and the orifice tube. Quick disconnects allow the in-line dryer to be easily changed when needed. -Evaporator, Low pressure liquid refrigerant boils collecting heat from the surrounding area. -Accumulator, Acts as a liquid/vapor separator and ensures that only vapor will reach the compressor. On an orifice tube system, the liquid refridgerent leaving the evaporator can damage the compressor. Therefore, the accumulator is located in the suction line after the evaporator. The accumulator acts as a liquid/vapor separator and ensures that only vapor will reach the compressor.

Thermostatic expansion valve

Two types of expansion valves are used on machines: internally equalized and externally equalized. Both Internally equalized and externally equalized expansion valves have a thermal bulb connected to a diagram by a small tube. The thermal bulb contains a refrigerant. A clamp holds the thermal bulb securely to the evaporator exhaust line. The thermal bulb is sensitive to exhaust temperature. If the exhaust temperature increases, the refrigerant inside the bulb expands. The expanding refrigerant exerts pressure against the diagram in the top of the valve. The diagram is connected through a pin to the valve seat. Pressure exerted against the diagram causes the diagram pin and valve seat to move. As the seat moves away from the orifice, more refrigerant flows into the evaporator. An increase in the flow of refrigerant causes the evaporator exhaust to become cooler. the cooler exhaust temperature causes the refrigerant to condense in the thermal bulb, reducing the pressure against the diagram, pin and valve seat. The valve seat moves to reduce flow through the orifice. In the internally equalized valve, the pressure of the refrigerant entering the evaporator is fed to the bottom of the diagram through the internal equalizing passage. Gas expansion in the thermal bulb must overcome the internal balancing pressure and the spring before the valve will open to increase refrigerant flow. On the external equalizer valve, the pressure fed to the bottom of the diagram is taken from the evaporator exhaust line by an equalizer tube. The equalizer tube tube balances the evaporator exhaust pressure against the pressure caused by the expansion of the gas in the thermal bulb. The superheat spring prevents surges of excessive liquid from entering the evaporator. "superheat" is an increase in temperature of the refrigerant gas above the temperature at which the refrigerant evaporated.