Thermal-hydrodynamic analysis for internally interrupted-finned tubes: Experimental, numerical and performance study

Abstract

The characteristics of fluid flow and heat transfer in an internally interrupted-finned tube were studied, experimentally and numerically, and a performance evaluation study was conducted in the present research. The numerical results were validated with the current experimental data as well as other published data, with a maximum deviation of 8.93 %. The effect of different key parameters like fin height, number of fin-rows, fin thickness and number of fins in each row on the thermal-hydrodynamic performance was explored. This study reveals that increasing both fin height and number of fin-rows raises the heat transfer coefficient and friction factor values, but fin thickness negligibly affects the performance. Notably, the average heat transfer coefficient value rises by 25.03 % if the fin height to diameter ratio is increased from 0.1786 to 0.4018, and by 21.4 % if the number of fins is increased from 2 to 6, compared to finless tubes under a mass flow rate of 0.39 kg/s, for three number of fins per row. Compared to the continuously finned tubes, the interrupted-finned tubes have higher heat transfer coefficient values if the interruption length is equal to or less than the fin length, while these values are reduced below that of the continuously finned if the interruption length is larger than the fin length. Clearly, when the interruption length is 3 times the fin length, the heat transfer coefficient value of the continuously finned tube is higher than that of the interrupted-finned one by 3.1 %, while the heat transfer coefficient value of the interrupted-finned tube is higher than that of the continuously finned one by 13.59 %, when the interruption length is reduced to one-third of the fin length. It is recommended using the interrupted-finned tubes over the smooth ones if the amount of mass flow rate flowing through both tubes is the same, but the use of interrupted-finned tubes is not recommended as opposed to smooth ones if both tubes are subjected to the same pressure drop across them.