Heat transfer enhancement and pressure drop reduction due to mixed convection between two vertical parallel plates

Purpose: This paper's aim is to examine flow and heat transfer through vertical channels between parallel plates, which is of prime importance in the design of cooling systems for electronic equipment such as that of finned cold plates in general, plate-and-frame heat exchangers, etc. Design/methodology/ approach: Numerical and analytical solutions are presented to investigate the heat transfer enhancement and the pressure drop reduction due to buoyancy effects (for buoyancy-aided flow) for the developing laminar mixed convection in vertical channel between parallel plates in the vicinity of the critical values of the buoyancy parameter (Gr/Re)crt that are obtained analytically. The numerical solutions are presented for a wide range of the buoyancy parameters Gr/Re that cover both of buoyancy-opposed and buoyancy-aided flow situations under each of the isothermal boundary conditions under investigation. Findings: Buoyancy parameters greater than the critical values result in building-up the pressure downstream of the entrance such that the vertical channel might act as a thermal diffuser with possible incipient flow reversal. Locations at which the pressure gradient vanishes and the locations at which the pressure-buildup starts have been numerically obtained and presented for all the investigated cases. Research limitations/implications: The study is limited to the laminar flow situation. Practical implications: The results clearly show that for buoyancy-aided flow, the increase of the buoyancy parameter enhances the heat transfer and reduces the pressure drop across the vertical channel. These findings are very useful for cooling channel or chimney designs. Originality/value: The study is original and presents new findings, since none of the previous studies reported the conditions for which pressure buildup might take place due to mixed convection in vertical channels between parallel plates.