Waste Heat Recovery Analysis: An Overview of Reversed Heat Pump Systems

Heat recovery systems are usually assembled by combining a number of systems towards achieving the desired objective. To achieve waste heat recovery, heat pumps incorporate appropriate changeover or reversing valves to achieve cooling, thereby recovering the expected end product of heat. This paper presents an overview of reversed heat pump systems used for waste heat recovery. The review identifies the core components of reversed heat engines as compressor, condenser, expansion device evaporator and drying chamber. Also, the study identified the four basic types of heat pumps and they include air-to-air heat pumps, water-to-air heat pumps, water-to-water heat pumps and ground source heat pumps. Furthermore, the study identified the available waste heat recovery equipment and their classification. The common classification include steam generators, recuperators, shell and tube heat exchangers, fin tube heat exchangers, heat pipes and run-around-coils. Typical schematics of these systems, showing their component parts, are also presented. Finally, a study of the benefits of waste heat recovery systems is presented and the work identifies both direct and indirect benefits. Direct benefits include improved efficiency of a system while indirect benefits include reduction in pollution, reduction in equipment sizes, and reduction in auxiliary energy consumption. This findings presents a thorough knowledge base on reversed heat pumps for waste heat recovery.