Experimental and numerical analysis of the thermo-hydraulic performance of a cross-flow air-to-gas capsule-type plate heat exchanger

Abstract

Energy loss is a major problem in the petrochemical industry. One of the ways to save energy and reduce fuel consumption is to recover waste heat in thermodynamic cycles. One potential solution is to utilize an air-to-gas plate heat exchanger, The mechanism that conveys the thermal energy from the waste gases in the combustion chimney of the boilers to preheat the air required for the combustion process within the same system, known as a heat recovery system. As gasses have a low heat transfer coefficient, capsules with different patterns have been designed on the plates of this heat exchanger to increase the heat transfer rate. The initial configuration of the heat exchanger incorporates both analytical and numerical approaches in its design. In addition, to achieve an optimal hydrothermal performance of the exchanger, the pattern and placement of capsules and arrangement of plates have been numerically investigated. 4 novel models were studied (IC, IP, IIC, IIP), and results showed that theIICmodel had better performance in comparison with other models. The Nusselt and friction factor equations in capsule-type channels have been extracted by numerical simulations. By defining the performance evaluation criteria, it was demonstrated that the heat transfer improvement in the channel with capsules is more significant than the impact of increased pressure drop compared to a simple rectangular channel. Therefore, the use of the capsuled channel is justified. TheIICmodel illustrated the best performance compared to the simple channel, as indicated by the increase infandNuvalues by 35–44% and 28–55%, respectively, for gas side channels in the Reynolds number range of 3500–14000. Finally, the heat exchanger (with the selected capsule pattern) is constructed and installed in the relevant unit for applying experimental tests. The results of this study indicate that the maximum deviation among the calculated results and the corresponding experimental data is 13.9%.