Numerical investigation on the thermal performance of cross‐cocurrent and countercurrent three fluid heat exchanger with flow maldistribution at the inlet

Abstract

AbstractFlow maldistribution at the inlet of a heat exchanger (HX) is a significant parameter that needs to be considered to judge the performance of the same. In this paper, four arrangements of three‐fluid cross‐flow heat exchanger (3FCFHX) with different flow conditions are considered as shown in Figure 1 in which is the performance of cross‐countercurrent and cross‐cocurrent arrangements for uniform and flow maldistribution at the inlet. In addition, the effect of different inlet fluid flow models on the HX performance are investigated numerically. Among the three fluids in these arrangements, the central fluid is considered to be the hot fluid. From the principles of conservation of energy, the governing equations for three fluids are generated and solved using the finite element method. Four different inlet fluid‐flow models are considered for the analysis. Performance is judged using hot fluid effectiveness and the number of transfer units for a different range of governing parameters. The effects of inlet flow maldistribution (IFM) are measured using degradation factors. The results show that the performance of cross‐cocurrent arrangement is found to be superior to the cross‐countercurrent arrangement. In addition, the IFM enhances thermal performance. Further, it is determined that the flow maldistribution at the inlet will enhance the hot fluid effectiveness by 4%–4.5% and 1.8%–2% in cross‐cocurrent and countercurrent arrangements, respectively. The results give a thorough insight into the significant concerns involved in the design of such HXs. Application of the finite element method proves the ease of determining the exit temperatures of the fluids in the HX. This approach is indeed time‐saving and gives insights when compared to the CFD approach.