Design and experimental investigations of a cylindrical microjet heat exchanger for waste heat recovery systems

Abstract

Compact heat exchangers have more and more applications in many areas, including the HVAC, food and petrochemical industry. This paper describes the development of heat exchanger technology for waste heat recovery (WHR) from a range of processes. Case-study testing shows that the proposed heat exchanger can successfully enhance heat transfer and recover waste heat in a range of applications making them economically, environmentally and technically feasible. The heat exchanger is based on multiple jet impingement on the cylindrical heat transfer surface. It comprises four coaxial pipes (a supply channel and a return channel for two fluids). The design of the heat is based on available on the market standardized materials. The study of heat transfer in water-water flow allows determining the heat transfer efficiency and the heat transfer coefficient values. Data were collected for the pressure drops in heat exchanger not exceeding 15 kPa, i.e. such as in conventional heat exchangers. Hydraulic characteristics of a prototype heat exchanger were obtained. Experimental values of heat transfer for jet impingement were calculated. Obtained values of heat transfer coefficient were compared with literature correlations. A comparison of results of thermal-flow performance with double pipe heat exchanger indicated that the tested device in low flow rates obtains higher heat transfer coefficients, heat transfer increased 50%. The pressure losses of the novel heat exchanger are lower than standard double pipe heat exchanger.