Simplified Correlation Equations of Heat Transfer Coefficient During Phase Change Flow Inside Tubes Filled with Porous Media

In this work an easy to use, simple and direct equations were formulated and tested. Heat transfer coefficients of phase change fluid flow were examined in this work. The considered fluid flow encountered convection heat flux inside rigid tubes filled with porous media. During the flow, phase change was assumed. Experimental work was conducted using Carbon dioxide as fluid. An analytical method using exponential non dimensional analysis was used. The Buckingham π theorem and method of indices was used to obtain simplified formula for the convection heat transfer coefficient and for the Nusselt number. Two different correlations can be extracted from this formula; one for the evaporation process and the other for the condensation process. As a case study, carbon dioxide was used. Resulted values were compared to the experimental values for validation purposes. Results also were compared to published values and found in the same range of uncertainty and exactness. The formulae obtained can be used to calculate the mean heat transfer coefficients, (h corr) and heat flux. Heat flux is the catalyst for phase change. Enhancement in heat transfer by increasing heat flux was due to the existence of the porous media inside the tube. Better heat exchanger design as well as better condensers and evaporators will result. Better energy use and higher effectiveness factors may result by using more simple and accurate equations.