Analysis of heat transfer and pressure loss in heat exchangers with both helical and rotational inner pipe

In this study, to increase heat transfer in helical pipes which have different number of helices, rotation of helical pipes was investigated experimentally. An experimental set up was established to determine heat transfer and pressure loss in rotational helical pipes. Heat transfer and pressure loss were calculated with different rates of capacity, different flow rates and different number of rotations. In these experiments, which were done for every kind of pipe, the flow was turbulent. The calculations were performed for both internal pipe and the annular spaces between internal pipe and external pipe. All experiment results were compared with each other to get the best results. Nusselt numbers, pressure losses and effectives values of exchangers were obtained depending on experimental results and the results were plotted according to various Reynolds numbers. Besides, empirical formulas were derived for every kind of pipe. According to results of experiments, the best heat transfer was obtained in the pipe with five helices with rotating at 300 rpm. When the pipe with five helices was rotating with 300 rpm, heat transfer increased 211,63% and pressure loss increased 156,50% compared to straight pipe. Heat transfer is better in helical pipes compared to straight pipes, but pressure loss also increases with the effects of rotation and helices. However, this loss can be ignored due to the fact that it is very small compared to gaining of heat transfer. Keywords: Heat transfer, heat exchangers, flow in rotational helical pipes, turbulent flow, secondary flows