Heat transfer and fluid flow characteristics of air-water heat exchanger inserting metal wire

Abstract

There are various methods for heat transfer enhancement. For example, one can attach various fins on the heat transfer surface, process the surface roughly, insert twisted tape, and so on. These methods increase the heat transfer coefficient or area by manufacturing changes to the heat transfer surface. In this study, heat transfer performance of air-water heat exchanger was evaluated under the condition inserting metallic wire. Moreover, heat transfer performance of heat exchanger attaching fins was compared with that inserting porous material. Experimental apparatus consists of a heat exchanger, a blower, a heater and a cooling water system. The heat exchanger has horizontal rectangular channel and it’s inside region of heat exchanger is separated with eight small channels. Air is used as working fluid. The air is supplied to the heater using the blower as a forced convection. After being heated by heater, the air is supplied to heat exchanger. During experiments, the temperature of the water is kept constant. The water is supplied to the channel of cooling water of heat exchanger from the isothermal bath. The temperature of air was set to the range from 200°C to 450°C. The temperature of cooling water was kept 70°C constantly. The fine cooper wire diameter of 0.5 mm was used as porous material. The heat transfer performance of the heat exchanger was evaluated by the amount of heat removal and pressure drop. The results of experiments show that the amount of removed heat was increased slightly by increasing the amount of inserting metallic wire. However, the pressure drop by increasing them was significant. It shows that it is necessary to improve the heat removal increases due to radiation. It is assumed that amount of heat removal increases by increasing the porosity of metallic wire and increasing the temperature of the air.