Experimental and Numerical Investigation of the Effect of Rotational Flow on Heat Transfer in a Concentric Double Pipe Heat Exchanger

In this study, the effect of the formation of rotational flow in the axial clearance of a concentric double pipe-type heat exchanger on the convective heat transfer coefficient of inner fluid (cool fluid) was experimentally investigated. In addition, the effect of rotational flow, the temperature, and flow rate of the outer (hot) fluid on the amount of heat absorbed by the inner fluid was examined. These parameters were examined for five flow rates of the inner fluid against three flow rates of the outer fluid. It was observed in the experimental study that the convective heat transfer coefficient of the inner fluid in both rotational and irrotational flow increased with the flow rate and temperature of the outer fluid and that the highest increase occurred with the formation of rotational flow at the interface. When the convective heat transfer coefficient increase rate of the inner fluid was compared for the case at 1 LPM for the empty pipe in the axial cavity and for the case at 1, 2, and 3 LPM for the rotary pipe, the increase rate was found to increase by approximately 182%, 242%, and 291%. It was concluded that forming rotational flow in the axial clearance was more effective than increasing the flow rate. Additionally, the amount of heat transferred to the cool fluid and the convective heat transfer coefficient increased when the temperature increased. In addition, the laminar flow and the heat transfer in the concentric pipes were investigated numerically and experimentally in this study.