Abstract
Longitudinal heat conduction has a significant effect on the heat transfer performance of plate heat exchangers, but longitudinal heat conduction is usually neglected in numerical studies and the thermal design of a heat exchanger. In this paper, heat transfer models with and without longitudinal heat conduction are proposed to analyze the effect of small-scale longitudinal heat conduction in a plate heat exchanger. The performance of small-scale longitudinal heat conduction is illustrated by temperature and heat flux contours in the heat transfer models with and without longitudinal heat conduction. The results show that small-scale longitudinal heat conduction occurs in the plate and a more uniform temperature profile of the plate is obtained due to small-scale longitudinal heat conduction. In balanced flow, the contributions of longitudinal heat conduction for counter-flow, cross-flow and parallel-flow plate heat exchangers are −3.15%, −0.09% and 0, respectively, whereas, for the respective unbalanced flows they are evaluated to be −1.73%, 0.53% and 0.05%, respectively. Moreover, it is observed that small-scale longitudinal heat conduction in plates is influenced by the thermal conductivity of the plate. The higher the thermal conductivity, the larger is the reduction of thermal performance. The contribution of longitudinal heat conduction varies from −0.54% to −4.01%.
Highlights
In a surface heat exchanger, heat is transferred from the hot fluid to the cold fluid through a solid wall [1]
Balanced flow and unbalanced flow are always considered in the number of heat transfer unit (NTU) method for heat exchanger design [11]
The small-scale Longitudinal heat conduction (LHC) in the plate can be studied by the heat transfer models with and without
Summary
In a surface heat exchanger, heat is transferred from the hot fluid to the cold fluid through a solid wall [1]. The numerical model of CC unit cell was used to study the Energies 2018, 11, x FOR PEER REVIEW thermal performance including LHC They evaluated the effect of LHC by theoretical method and the and the theoretically results matched that of the numerical simulations. Small-scale LHC in the plate of cross-wavy (CW) primary surface heat exchangers They calculatedThey the calculated the contributionheat of longitudinal heat conduction by using two different contribution of longitudinal conduction by using two different heat transfer models.heat. Plate heat exchangers are always studied by CFD simulations and a good agreement with experimental results were obtained by using low Reynolds number k-ε model (LRKE) for both liquid [21] and gas [29]. Where ∆p is the pressure loss in the channel and L is the channel length in flow direction
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