Design and optimization of a novel high temperature heat exchanger for waste heat cascade recovery from exhaust flue gases

Abstract

The waste heat of high temperature exhaust flue gases is widely distributed in many industrial processes. Recovery of waste heat is of great significance to energy saving and sustainability. In this paper, a novel high temperature heat exchanger with hybrid enhancement technologies is proposed to improve waste heat recovery efficiency based on the cascade recovery and utilization method. Algorithm for HTHE structural design and optimization is developed and verified according to the experimental results. Heat transfer and pressure drop performance of the proposed HTHE are estimated by using the algorithm. The results show that the effectiveness of the proposed HTHE increases as the gas temperature increases and mass flow rate decreases. Average effectiveness of the proposed HTHE and temperature of preheated air are 12.5% and 85.8 °C higher than those of traditional HTHE with additional 70.0% and 22.0% pressure drop on air and gas sides, respectively. The structural optimization of the proposed HTHE is carried out and it shows that the optimized HTHE has better heat transfer capacity and comprehensive performance under identical pressure drop, increasing effectiveness by 12.6% without enlarging pressure drop compared with the non-optimized HTHE.