Dynamic behaviour of a plate heat exchanger: Influence of temperature disturbances and flow configurations

Abstract

Understanding the dynamic properties of a plate heat exchanger plays an essential role when developing smart control algorithms for modern energy-efficient district heating and cooling applications. In this work, the dynamic behaviour of a counterflow plate heat exchanger is studied in order to understand its transient responses due to inlet temperature disturbances at different fluid flow configurations. For this purpose, a suitable theoretical model has been proposed. The temperature transients are evaluated numerically by solving a lumped-parameter system representing the derived 1D model of the studied plate heat exchanger. The numerical results revealed that different fluid flow configurations considerably influence the transient temperature responses as well as the overall temperature drop and heat transfer rate when following the cold down process of a fluid travelling from the inlet to the outlet of the plate heat exchanger hot fluid side. The predicted transients are experimentally verified by conducting a series of systematic tests using infrared thermography technology. The analysis shows that the proposed model is in good agreement with the experiments. The results of the thermal imaging measurements also provide a more in-depth insight into the temperature distribution and its transient front propagation along the fluid flow channels. In future studies, such an experimental approach is valuable to identify the critical temperature zones when predicting the thermal fatigue life-time of brazed plate heat exchangers and as well to extend the proposed theoretical model to include the 2D local heat transfer coefficient distribution obtained by the IR thermography.