Assessment of the optimum operation conditions on a heat pipe heat exchanger for waste heat recovery in steel industry

In order to investigate the characteristics of a heat pipe heat exchanger (HPHE) used for recovering the waste heat in a slag cooling process in steel industry, a waste heat recovery experimental system has been designed and established. Main parameters representing the HPHE are investigated experimentally and theoretically, the optimum operation conditions are determined by integrating the first and the second law of thermodynamics. The results indicate that the heat transfer ratio and heat transfer coefficient increase with waste water mass flow rates increasing at constant cold water mass flow rate. As the waste water mass flow rate varies between 0.8 and 1.9 m3/h, exergy destruction rate, exergy efficiency and effectiveness of the HPHE have the values from 0.277 to 0.510 kW; from 66.1% to 42.9% and from 0.085 to 0.192, respectively. The optimum waste water and cold water mass flow rate are deduced as 1.40 and 2.90 m3/h, respectively. In addition, the effect of on-line cleaning device on the heat transfer and fouling cleaning has been verified by experiments in this study. It is concluded that the heat transfer performance has been significantly improved after using the on-line cleaning device.