Experimental investigation on thermal performance and fluid flow characteristics in heat exchanger tube with solid hollow circular disk inserts

Enhancement in heat transfer by generating turbulence in the fluid stream inside the heat exchanger tube has become an innovative area of research for the researchers. Hence, many techniques have been investigated and adopted on enhancement of heat transfer rate to reduce the size and cost of the heat exchangers. In the present study the effect of solid hollow circular disk (SHCD) turbulators on heat transfer, friction factor and thermal performance factor of the heat exchanger is evaluated through experimentation. The different parameters used for the experimentation include fixed thickness ratio (t/D) of SHCD, i.e. 0.0075, diameter ratios (d/D = 0.6, 0.7 and 0.8) and pitch ratios (l/D = 1, 2, 3 and 4). The experiments are conducted in the range of Reynolds number from 6500 to 23,000. The test setup comprises of the test section (1.4 m long) with a hydraulic diameter (D) of 68 mm. Constant heat flux is provided in the test section with the help of a variable voltage transformer and coiled wire heater. On the basis of experimental investigation, there is around 4.45 times enhancement in heat transfer in case of PR = 1 and DR = 0.6, and around 1.4 times enhancement in thermal performance factor for PR = 1 and DR = 0.8 when compared to smooth tube heat exchangers. (C) 2016 Elsevier Ltd. All rights reserved.