An evaporative condenser is a device which facilitates the condensation, or return to a liquid state, of a hot gas or vapor in a tube system using the evaporation of water flowing over the tubes. In simple terms, an evaporative condenser uses a system of tubes exposed to a constant flow of water to cool and condense a hot gas. The cooling and subsequent condensation of the gas is caused by a process of heat transfer that takes place when the water flowing over the gas-filled tubes evaporates. This process is used extensively in the air conditioning industry as a means of condensing refrigerant gas.
All refrigeration and air conditioning processes use a gas to facilitate the transfer of heat between the air-conditioned area and the outside atmosphere. This process relies on the use of a compressor to increase the pressure in the evaporator section, or air conditioned area, of the system which in turn allows the absorption of heat from that area. This absorbed heat and any heat generated by the compression process needs to be rapidly removed from the refrigerant in the outside, or condenser, part of the system so that the cycle of heat transfer can be repeated. This is typically done by allowing the hot refrigerant to circulate through a series of tubes exposed to a fan induced airflow.
Although effective, this method of cooling or condensation of the refrigerant is not particularly efficient, particularly in large commercial systems. This lack of efficiency becomes pronounced when the ambient, or outside, temperature rises above 100 degrees Fahrenheit (37 degrees Celsius). In these conditions, a conventional air-cooled system may loose up to 25% of its operational efficiency. The evaporative condenser is a far more efficient condensation mechanism in larger systems losing only a fraction of its effective capacity in all ambient conditions.
The evaporative condenser system typically consists of a series of pipes or tubes that carry the hot refrigerant gas. These tubes are simultaneously exposed to a spray of water and fan facilitated airflow. A portion of the water flowing over the gas filled tubes evaporates due to a combination of being heated by the tubes and the flow of air. This evaporation is the mechanism that allows the rapid cooling of the refrigerant gas which is then pumped back into the building to resume the air conditioning process. The remaining water is then collected and re-circulated over the condenser coils.
Although a common feature in large commercial air-conditioning systems, the evaporative condenser is seeing an increase in use in smaller domestic air conditioners. These systems use approximately 5-8 gallons (19-30 liters) of water which is circulated over the condenser for eight hours before being purged from the system completely and replaced with fresh water. The excellent efficiency characteristics of an evaporative condenser system translates into considerable financial savings and this type of system is sure to see increased use in residential air conditioning applications.