Theoretical Analysis of LMTD, Thermal Effectiveness, and Thermal Efficiency Methods Applied to Chevron Plate Heat Exchangers (CPHEs)

This article presents a practical and low-cost procedure for the preliminary prediction of the performance of chevron plate heat exchangers (CPHEs), also pointing to broader design and research topics—such as the relationship between pressure drop and heat transfer, geometric optimization, irreversibility, and advanced working fluids—that can be explored beyond the base case. Some solutions and discussions presented in the article are the result of challenge proposed to students completing a Mechanical Engineering course, in subjects related to Energy Efficiency. The article presents theoretical results for four chevron plate heat exchangers (CPHEs), with the objective of analysis, theoretical-experimental comparisons, and discussions. Experimental and numerical results from published literature are used as a reference. The authors of the reference work present theoretical results applying an analytical procedure, called the bisection method, to the four different types of compact heat exchangers. In the present article, the methods used for theoretical reproduction are the logarithmic mean temperature difference (LMTD) method, the thermal effectiveness (ε-NTU) method, and the efficiency thermal method, with emphasis on the latter. A more detailed theoretical analysis is applied to the first of the four heat exchangers, with graphical results for the outlet temperatures of the working fluids. In this first approach, theoretical-experimental comparisons show deviations ranging from 1% to 4%, with the heat exchanger area defined through the reference work. Graphical results for thermal effectiveness and heat transfer rate are obtained from data taken from the reference work, using temperature and mass flow rate ranges, and applying the thermal efficiency method. Additionally, tabulated values are used to present results obtained for the last 3 heat exchangers analyzed. In these cases, theoretical-experimental comparisons for outlet temperatures, with real heat transfer areas calculated from experimental data, range from 0.00% to 1.01%.