Abstract
Heat transfer performances and flow structures of laminar impinging slot jets with power-law non-Newtonian fluids and corresponding typical industrial fluids (Carboxyl Methyl Cellulose (CMC) solutions and Xanthangum (XG) solutions) have been studied in this work. Investigations are performed for Reynolds number Re less than 200, power-law index n ranging from 0.5 to 1.5 and consistency index K varying from 0.001 to 0.5 to explore heat transfer and flow structure of shear-thinning fluid and shear-thickening fluid. Results indicate that with the increase of n, K for a given Re, wall Nusselt number increases mainly attributing to the increase of inlet velocity U. For a given inlet velocity, wall Nusselt number decreases with the increase of n and K, which mainly attributes to the increase of apparent viscosity and the reduction of momentum diffusion. For the same Re, U and Pr, wall Nusselt number decreases with the increase of n. Among the study of industrial power-law shear-thinning fluid, CMC solution with 100 ppm shows the best heat transfer performance at a given velocity. Moreover, new correlation of Nusselt number about industrial fluid is proposed. In general, for the heat transfer of laminar confined impinging jet, it is best to use the working fluid with low viscosity.
Highlights
Heat transfer enhancement technologies have drawn much more attentions in recent years for the intense demand in the industrial fields
4, Nu ave is influenced by Reynolds number Re, power-law index n and consistency scale in order to simulate extensive fluid in nature, the associated results show large variable ranges
For a fixed Reynolds number, Nuave increases with corresponding inlet velocity U calculated via Equation (6)
Summary
Heat transfer enhancement technologies have drawn much more attentions in recent years for the intense demand in the industrial fields. While the active methods such as forced channel flow, impinging jets, mechanical vibration and electromagnetic field consume extra energy. Among these heat transfer enhancement methods, impinging jets have the highest known single phase local heat transfer rate but low drop pressure, which is attractive for electronic thermal management [1]. Basic parameters such as Reynolds number and jet-to-surface spacing significantly influence flow fields and heat transfer performances [2,3,4].
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