Experimental investigation on thermal performance and fluid flow characteristics in circular cylindrical tube with circular perforated ring inserts

Heat transfer enhancement by creating turbulence in the physical behavior of fluid flow inside the heat exchanger tube has become a really interesting area for the researchers in order to reduce the size and cost of the involving equipment especially in heat exchangers. Though very significant results are achieved lower range of Reynolds number, but still research is being carried out for the higher range. In this experimental study the effect of circular perforated ring (CPR) insert on heat transfer, friction factor and thermal performance of the heat exchanger tube is evaluated. The different parameters used for the experimentation include, fixed thickness ratio (t/D) of PCD i.e. 0.0075, diameter ratios (d/D = 0.6, 0.7 & 0.8), pitch ratios (l/D = 1) and perforation index (P-A/T-A = 8%, 16% & 24%). The experiments are conducted in the range of flow varying between 6500 and 23,000 Reynolds numbers. The experimentation is carried out in the test section of 1.4 m length with a hydraulic diameter (D) of 68 mm. The test section was heated with constant heat flux of 1000 W/m(2) with the help of a variable voltage transformer. On experimentation, it is found that, there is about 4 times augmentation in heat transfer in case of PI = 8% & DR = 0.6 and 1.47 times improvement in thermal performance factor for PI = 24% and DR = 0.8 as compared to smooth tube heat exchangers. (C) 2016 Elsevier Inc. All rights reserved.