Experimental investigation of thermal performance and entropy analysis of sphere turbulators

Abstract

In this study, the effects of different numbers of sphere turbulators placed in a circular-shaped test pipe under turbulent flow conditions on heat transfer, friction factor, thermal performance factor and entropy production were experimentally investigated. Water was used as the working fluid in the experiments carried out in the number range Re=8379-16701. Initially, plain pipe and supported plain pipe experiments were carried out by keeping the fluid inlet temperature and test pipe surface temperature constant. Then, 1, 2 and 3 sphere turbulator experiments were carried out under the same conditions, respectively. According to the findings, the maximum Nusselt number increase compared to the supported plain pipe was 83.34% for the test pipe with 3 sphere turbulators. The minimum and maximum Nu number increase rates of 3 sphere turbulators compared to 1 and 2 sphere turbulators were obtained as 42.61%-46.93% and 13.99%-17.11%, respectively. The increase rates of maximum friction factors of 1, 2 and 3 sphere turbulators compared to the supported plain pipe were 174.42%, 226.70% and 306.53%, respectively. In addition, the maximum total entropy rate for sphere turbulators was obtained as 0.058 W.m-1.K-1 for 1 sphere turbulator at Re = 8379. In terms of the second law, the maximum entropy generation of sphere turbulators compared to the supported plain pipe decreased by 79.39% for 3 sphere turbulators at Re = 8379. As a result, it was concluded that the optimum number of sphere turbulators is 3 sphere turbulators with the lowest entropy production number and the highest TPF value (1.28).