An experimental analysis on a Double Pipe Heat Exchanger Modified with Turbulators

Abstract

Abstract Heat exchangers find so many applications starting from domestic purposes to industries, automobiles, aviation and many more. The need of the hour is to maximize the efficiency of heat exchangers and at the same time, reduce the size of the heat exchanger. One of the methods to achieve this purpose is introduction of turbulators in the heat exchangers. Turbulators serve the purpose of heat transfer enhancement but they also cause drop in fluid pressure. A variety of turbulators have been proposed by various researchers in the past. Three common turbulators are spring insert, twisted tape insert and twisted wire mesh insert. The present study deals with comparative experimental analysis of a double pipe heat exchanger that has been modified by introduction of turbulators. Different sets of combinations have been used for carrying out experimental study. For spring inserts, pitch has been chosen as the variable. Three spring inserts having pitches 5 mm, 10 mm and 15 mm respectively have been used. For twisted tape inserts, the twist ratio has been taken as variable with twist ratios 5, 3.75 and 2.5 respectively. Similarly, for the twisted wire mesh inserts, twist ratio has been varied for carrying out the experimental analysis. Three twisted wire mesh inserts having twist ratios 5, 3.75 and 2.5 have been used in the heat exchanger. Experimental analysis was carried out for wide range of Reynolds number ranging from 5000 to 30000 for the hot fluid. Experiments have been performed for each set and the results for heat transfer characteristics and pressure drop characteristics have been compared. For the heat transfer characteristics, the comparison has been made between the Nusselt number values from Dittus Boelter equation, values obtained for plain pipe heat exchanger and the results obtained after introduction of various turbulators in the heat exchanger. Similar approach has been used for pressure drop characteristics by using the friction factor values obtained from Blasius Correlation. The whole experimental study is presented in condensed form in this thesis.