HEAT TRANSFER AND PRESSURE DROP IN TURBULENT FLOW THROUGH A TUBE WITH LONGITUDINAL PERFORATED STAR-SHAPED INSERTS

An experimental investigation has been carried out for turbulent flow convection heat transfer in a circular tube with perforated star-shaped inserts. Inserts were fabricated using a mild steel sheet with perforations of 0.0%, 1.52%, 6.1%, 13.71%, and 24.37%. Air velocities, temperatures, tube wall temperatures, and pressure drops were collected to analyze the Nusselt numbers, heat transfer coefficients, heat transfer rate, friction factor, blower power, and heat transfer effectiveness for the plain tube as well as for the tube with inserts. The results indicated that as much as a two-fold improvement might be obtained in the turbulent flow heat transfer coefficient and the heat transfer effectiveness for the tube with the perforated star-shaped inserts than for the plain tube. With the experimental data, a correlation was also developed for prediction of the heat transfer coefficient and Nusselt number in turbulent flow for tubes with star-shaped inserts.