Purpose of Condensers

Purpose of Condensers Points : purpose of condensers The purpose of the condenser is to condense superheated gas coming out from the compressor, the temperature of which is sufficiently higher than the cooling medium or sink which may be atmosphere or environment for domestic machines or tap water for large ones. In a condenser, before the gas can be condensed into liquid, the temperature of the superheated gas is to be brought down to saturation temperature. The first few tubes to the condenser to this job of “superheating” the gas. During desuperheating, the pressure remains the same.

Water cooled cylinder heads are used to check over-heating of valve reeds, they limit superheating. These cylinder heads cannot reduce head pressure or condensing temperature of the system. It only keeps down tie superheating of discharge gas and the temperature of compressor parts. Shows air cooled condenser.

In the condenser, once the gas has been cooled, desuperheated and brought down to the condensing temperature the vapour begins to condense, to saturated liquid. During condensation, the pressure and condensing temperature remains constant. If the temperature of the cooling medium is lower than the saturation temperature. The saturated liquid further cools or subcools or undercools. Shows horizontal shell- and-tube condenser. Shows tube-in-tube type condenser. The liquid can also be subcooled by liquid suction heat exchanger, which comprise of’ lagging together a sort length of pipe at the evaporator outlet, carrying low pressure refrigerant to the compressor inlet to a length of pipe before the expansion valve carrying high pressure liquid refrigerant. Due to heat exchange low temperature vapour at low pressure receives additional heat due to subcooling of high pressure refrigerant before expansion valve. This causes slight superheating at the compressor inlet. Too much superheating at the compressor effects compressor capacity hence the heat exchanger is used only where it is absolutely essential. Since with lagging if the compressor work to he supplied is more than the cooling effect produces, the C.O.P. decreases. it is to be noted that with superheating, volume of the vapour increases, the compressor has to do additional work to cope this volume increase. In general sub-cooling improves C.O.P. The other way of improving C.O.P. is to use flash chamber.