Parametric investigation of thermal-hydrodynamic performance in the innovative helically coiled heat exchangers in the heat pump system

Abstract

This work aims to study the thermal-hydrodynamic performance of innovative multi tubes in tube helically coiled (MTTHC) heat exchanger used in the heat pump system. The 3D finite volume method and realizable k-ε turbulence model is considered to investigate the mechanism of flow and heat transfer in this MTTHC heat exchanger with the different coiled diameter and coiled pitch. Predicted values of pressure drop and outlet temperature are compared with our previous experimental results. The comparison shows the numerical method can be well to use for evaluating the performance of this novel MTTHC. The distributions of velocity, temperature and pressure along the flow direction for the certain cross-sections are presented. The effects of structural parameters of MTTHC and flow rates of inner and outer tube on the overall heat transfer coefficient, effectiveness and NTU, pumping power and pressure drop, thermal and hydrodynamic performance index (ξ) and inner and outer tube Nusselt number are investigated. It is found that decreasing the coiled diameter or increasing the coiled pitch can improve thermal performance. In addition, increasing the flow rate leads to an increase in pressure drop and pumping power. However, ξ enhances with increasing mw, and it worsens with increasing mref.