Travelling-wave thermoacoustic high-temperature heat pump for industrial waste heat recovery

Many industrial processes need steam at temperatures from 100 to 200 degrees C, normally produced by directly heating water via coal, natural gas or oil combustion. Nevertheless, large amounts of unused heat below 100 degrees C are wasted in other industrial processes. In principle, a high-temperature heat pump capable of using the industrial waste heat can provide steam above 100 degrees C. However, until now, efficient and reliable heat pump technology for the application is not available. In this paper, a novel TWTAHP (travelling-wave thermoacoustic heat pump) is presented to meet this requirement, which can potentially solve the problems occurring in conventional vapour-compression heat pump such as high discharge temperatures, high pressure ratio, and low efficiency. This system comprises three linear pressure wave generators which are coupled with three heat pumps into one single closed loop. Theoretically, this system is able to complete the thermoacoustic conversion with a much higher efficiency. The theoretical simulations were performed at varied waste-heat temperatures (40-70 degrees C) and different hot-end temperatures (120-150 degrees C). The computing results show that this new heat pump system has a high relative Carnot efficiency of about 50%-60%. In using a reliable linear compressor and a thermoacoustic heat pump with no-moving parts, this technology has an inherent potential for high reliability. Therefore, it is believed that the travelling-wave thermoacoustic heat pump is an enabling technology with good prospects in efficiently harvesting industrial waste heat. (C) 2014 Elsevier Ltd. All rights reserved.