Effect of surface roughness on the performance of heat exchanger

In this research work, double-pipe counter flow heat exchanger has been analyzed with various roughnesses of steel, aluminum and copper pipes and also with two different cold fluids: water and ammonia at same flow rates. Dimensions of the heat exchanger are inner and outer diameters of inner pipe being 0.034 and 0.042 m, whereas diameters of outer pipe are 0.054 and 0.06 m, respectively, and length of heat exchanger is 1.8 m. In K-ℇ modeling, computational fluid dynamics tool has been used for performance analyses and this computational work has been validated by entropy, exergy and entransy analyses. After computational numerical analyses, this investigation has concluded that maximum rate of heat transfer through heat exchanger has been found with copper–ammonia combination with smooth surface. Minimum rates of entropy generation, exergy destruction, entransy dissipation-based thermal resistance and entransy dissipation number have been obtained with copper–water combination, and minimum entropy generation number and maximum effectiveness have been obtained with copper–ammonia combination. Percentage changes in the parameters/properties have also been calculated at different operating conditions. Copper as inner pipe material with smooth surface and ammonia as cold fluid have been recommended for counter flow double-pipe heat exchanger. Computer software has been developed for hassle-free analyses of heat exchanger.