The superior performance of the systems with water-cooled and evaporative condensers stems from better heat transfer on the heat-rejected-medium side of the condenser. The latent heat transfer to the air stream passing through the cooling tower and the evaporative condenser increases not only heat rejection rate but also refrigeration capacity. This also lowers the condensing pressure, thus decreasing work of compression per unit refrigeration and increasing compressor life.
The COP values based on electric power were determined by taking into account only the power input to the compressor motor. Since the fan consumed a considerable amount of energy for sending air at high flow rates to keep the condensing temperature at the required level, the system employing air-cooled condenser would give even lower COP values based on electric power if fan power were also taken into account.