Effect of thermal boundary conditions and thermal conductivity on conjugate heat transfer performance in pin fin arrays

摘要

The present work experimentally investigates the conjugate heat transfer performance for pin fin arrays. The geometry of pin fin arrays is typical of x/D = y/D = 2.5 and H/D = 1. The effect of two main factors: material thermal conductivity and thermal boundary conditions, i.e. conjugate and convective boundary conditions, are quantified by comparing the nondimensional temperature and Nusselt number. For conjugate heat transfer, models are constructed with materials with thermal conductivity ranging from 0.23 W m~(-1) K~(-1) to 16 W m~(-1) K~(-1). Uniform heat flux is imposed along the external wall of pin fin arrays and highly resolved temperature distributions of internal wall is obtained with steady liquid crystal, meanwhile external wall temperature is measured through thermocouples. For convective heat transfer, model is constructed with low thermal conductivity material to ensure the usage of transient liquid crystal to obtain heat transfer coefficients of the internal wall on the same configuration. Experimental data of temperature and heat transfer coefficient distribution is used as boundary conditions to conduct FEM calculations of pin fin array. Internal and external wall non-dimensional temperature distributions, as well as iso-thermal line distributions of the whole domain, are compared. Results indicate that thermal conductivity can significantly impact the heat transfer capacity, i.e. Nusselt number; meanwhile, the necessity of taking conjugate heat transfer effect is demonstrated by comparison with purely convective results.