Prediction of heat transfer coefficients of shell and coiled tube heat exchangers using numerical method and experimental validation

In this work, the heat transfer of shell and helically coiled tube heat exchangers was investigated. Numerical and experimental methods were used to investigate the effect of physical properties of fluid (i.e. viscosity, thermal conductivity, specific heat capacity and density), operational parameters (i.e. the velocity and temperature of fluid) and geometrical parameters (i.e. pitch, diameter of the tube, diameter of shell's inlet, diameters of coil and shell, heights of coil and shell, and the distance between the inlet and outlet of the shell) on Nusselt numbers of both sides. Totally 42 cases and 15 tests were investigated in the numerical analysis and experimental work, respectively. Measurements and analysis were performed, when the steady state was attained. The working fluid of both sides is water, which its viscosity and thermal conductivity were assumed to be dependent on temperature, in the numerical analysis. Results indicate that if the pitch size is doubled, the shell side Nusselt number increases by 10%, while the coil side Nusselt numbers increases by only 0.8%. Also it was found that an increase of 50% in the height and diameter of the shell causes a decrease of 34.1% and 28.3% in the Nusselt number of the shell side, respectively. Based on the results, two correlations were developed to predict Nusselt numbers of coil side and shell side for wide ranges of Reynolds and Prandtl numbers (1000 < Rec < 27,000, 2000 < Resh < 49,000 and 1.9 < Prc and Prsh < 7.1). These correlations were compared with the experimental data of the present study and previous works. It was found that these correlations are in good agreement with the experimental data for wide ranges of operational and geometrical parameters.