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

With variable thermo-physical properties, some thermal phenomena could be significant in multi-stream heat exchangers, which may be unimportant in conventional two-stream ones. For example, the formation of temperature cross or longitudinal heat conduction through the solid body can be mentioned. In this paper, the effect of property-variation is addressed in a multistream heat exchanger. Numerical data from a threedimensionalfinite volume solution for heat transfer between three fluid streams, and between solid parts and the fluid, is utilized. Most of the thermo-physicalproperties of both fluid and solid parts are considered temperature-dependent, and longitudinal heat conduction, temperature distribution through fins, and formation of temperature crosses are studied. It is found that the longitudinal conduction increases by ۹%, and the position of the temperature-cross point is changed due to the property variations. For some flow arrangements, the variation of properties causes both quantitative and qualitative changes in thermal phenomena. Results show that variation of density and thermal conductivity of fluids have the highest impact on the temperature field due to their effects on momentum and energy transfer.

Keywords:

Multi-Stream Heat Exchanger , Internal Heat Leakage , Property Variation , Longitudinal Heat Conduction , Temperature Cross.