Heat-transfer characteristics of wet heat exchangers in parallel-flow and counter-flow arrangements

Abstract

Wet heat exchangers have many applications in the fields of air conditioning, refrigeration and power plants. They can achieve higher heat-transfer rates than dry heat exchangers. Heat transfer takes place from a hot fluid flowing inside the tubes to air, through the film which is formed by spraying water onto the heat- transfer surface. Both sensible and latent heats are transferred from the spray water to air; the latter makes the major contribution and causes a small amount of spray water to evaporate into the air stream. These heat exchangers are classified according to the flow arrangement of spray water and air, and the geometry of the tubes. Many researchers have studied the thermal characteristics of wet heat exchangers using different mathematical models. The effect of the wetted surface as the main factor of heat-transfer enhancement on the thermal performance of heat exchanger has been investigated extensively. In the present study, a mathematical model was applied to analyse the performance of the wet heat exchangers. Temperature distribution of three fluids flowing through the exchanger and the humidity distribution of the air for parallel and counter-current exchangers were obtained using the mathematical model. The effects of various operating conditions, such as mass flow rates of three fluids on the thermal performance of the exchanger were investigated. The results of the model were compared against reference experimental data.