NANO

HVAC 839 HVAC (a) Condenser: It is the heat exchanger where heat dissipation takes place. It consists of aluminium tubes and series of fins to provide the maximum heat transfer. Air flow across the condenser is induced by vehicle movement and assisted by electric fan attached to the frame of the condenser. The high pressure refrigerant vapour enters the condenser inlet. As the vapour passes through the condenser tubes, the air flow, assisted by the fan, carries the latent heat away from the condenser. This induces a change of state resulting in the refrigerant condensing into a high pressure warm liquid. From the condenser, the refrigerant continues to the receiver/ dryer. (b) Integrated Receiver Dryer (IRD): This component acts as a reservoir and is used to hold extra refrigerant until it is needed by the (a) Evaporator unit It is the last component in the cycle and serves as heat absorption unit. As the refrigerant flows through the evaporator it picks up heat from the cabin and gets vaporized. As this change of state occurs, a large amount of latent heat is absorbed. The evaporator is therefore cooled and as a result heat is extracted from the air flowing across the evaporator. The refrigerant leaves the evaporator, on its way to the compressor, as a low pressure gas. An evaporator sensor (thermistor) measures the air temperature at the evaporator outlet and sends signal to engine ECU for engaging/disengaging of compressor to prevent icing of the evaporator. (b) Expansion valve This small valve controls the flow of refrigerant into the evaporator. It is controlled by a temperature sensor at the evaporator outlet. If the outlet temperature is too high, it means not enough refrigerant is flowing into the evaporator and poor passenger cooling will result. If the outlet temperature is too cool, it means too much refrigerant is flowing and the evaporator fins will probably load up with ice. In either case, the feedback temperature sensor opens or closes the expansion valve opening to achieve the correct flow rate and evaporator outlet temperature. Condenser and Receiver Dryer (R.D.) evaporator. The drier within the receiver unit contains a filter and desiccant (drying material) which absorb moisture and prevent desiccant dust from being carried with the refrigerant into the system. The receiver drier is integrated into the condenser and is seperately serviceable. Evaporator unit and Expansion valve a b