Overall Heat Transfer Coefficients and Axial Temperature Distribution of Fluids in a Triple Tube Heat Exchanger

Abstract

Computation of overall heat transfer coefficients in a triple tube heat exchanger (TTHE) is complicated when compared to a double tube heat exchanger (DTHE) since the two overall heat transfer coefficients are not independent of each other and must be solved for simultaneously. Previous methods established towards calculation of these parameters either include assumptions that are not valid for all flow conditions and fluid flow rates or use empirical correlations which may cause significant deviations from actual values of these parameters. A more generic technique was developed for calculation of overall heat transfer coefficients and axial temperature distribution of fluids in a triple tube heat exchanger. The developed procedure has been used for calculation of these parameters at various fluid flow rates and product inlet temperatures. Theoretical double tube heat exchanger results were also tabulated for comparison purposes. The advantages of using a TTHE over a DTHE has been both conceptually explained and demonstrated using the results obtained. However, it was also shown that design of TTHE experiments is critical, especially in the co-current flow arrangement, since the relative flow rates of the fluids may result in a decrease in the effectiveness. The effect of fluid flow rates, product inlet temperature, and flow arrangement on values of overall heat transfer coefficients, total amount of heat transferred, and effectiveness were also investigated. These results were analyzed using SAS and interpreted for the consistency of the obtained results with the literature.