Calculation Examples by Using the Predictive Formulae on Heat Transfer

Abstract

The predictive formulae on heat transfer developed in the previous Chapter are applied in the present calculation examples to evaluate heat transfer of Al₂O₃-water nanofluid’s natural convection. Their theoretical and practical value in heat transfer application is attributed to that they are developed based on the comprehensive consideration of the effects of nanofluid’s variable thermophysical properties, nanoparticle’s shape factor and concentration, and fluid’s boundary temperature. It demonstrates that it is feasible to conduct theoretical study on convection heat transfer with actual nanofluids. In this theoretical study, two key works are performed. The first one is to develop advanced theory and method for the challenging research, and the second one is to develop advanced model for comprehensive consideration of various physical variables and parameters, including the variable thermophysical properties. By using the present correlations, four calculation Examples are provided to evaluate heat transfer rate with respective physical conditions. It is found that the present correlation on heat transfer can be used to rigorously evaluate heat transfer rate of Al₂O₃-water nanofluid’s natural convection. It is seen from the calculation results that with same fluid’s average temperature level, different fluid’s boundary temperatures still lead to different evaluated results on heat transfer coefficient. The calculation results also show that with increase of the fluid average temperature level, the heat transfer coefficient will increase. It reveals the charm of the present correlations developed based on the various physical variables and parameters including nanofluid’s variable thermophysical properties.