Plate heat exchanger, numerical modeling, validation
Finite volume modeling of plate heat exchangers is challenging in terms of computation time and robustness, especially in two-phase flow due to the coupling of pressure drop and heat transfer equations. Usually the entire heat exchanger is divided into segments and solved iteratively. Many thermophysical property calculations are required for each channel in each segment which is computationally expensive, especially with a high number of iterations. This led some models to employ pre-defined databases with many correction factors to overcome slow and unstable computation. In order to overcome this, an improved approach is developed for the analysis of plate heat exchangers with multi-fluid, multi-stream, and multi-pass configurations. The model is capable of handling simultaneous phase change in all channels. In the proposed approach, the fluid properties are propagated in one flow direction, while the fluid properties in the opposite direction are calculated in a given iteration. These operations are switched in the next iteration. The convergence of this approach is verified numerically. This approach shows significant improvement in computation speed and robustness compared to current models. This approach solves 6-12 times faster in terms of number of iterations required to solve a plate heat exchanger and more stable especially with a lower number of slices compared to existing model. The model is validated against 150 in-house experimental data points for single phase water, two-phase ammonia, and R22 boiling, and two-phase R134a, and R410A condensation. Overall, the model predicts heat capacity within 5%.