Effect of Property Variation on Thermo-Hydraulic Details in A Three-Stream Heat Exchanger: A Numerical Approach

In presence of variation of thermo-physical properties, some thermal phenomena could be significant in multi-stream heat exchangers which may be unimportant in conventional two-stream ones, e.g., formation of temperature cross or longitudinal heat conduction through solid body. in this paper the effect of property-variation is addressed in such thermal details of a multi-stream heat exchanger. numerical data from a three-dimensional finite volume solution for heat transfer between three fluid streams and also between solid parts and the fluid is utilized. a maximum number of thermo-physical properties of both fluid and solid parts are supposed changing. the considered details are longitudinal heat conduction, temperature distribution through fins and formation of temperature crosses. also the maximum heat exchange and its corresponding stream are studied. it was observed that the effect of property-variation on the longitudinal conduction could be increasing up to 9%. by taking the properties variable, the position of temperature-cross point is changed. for some flow arrangements, the variation of properties causes both quantitative and qualitative changes thermal phenomena. in one of the cases, the longitudinal heat conduction and the temperature cross are captured only by the more realistic variable-property analysis. by changing the properties one by one, it is concluded that the variation of density and thermal conductivity of fluids have the most significant influence, due to their coupling effect on momentum and energy transfer.