Hydrophilic materials have been widely used in heat exchangers. On the Secondary side of heat exchanger, water film generated on the plate wall could affect overall heat transfer performance of the heat exchanger. In this study, an experimental analysis of two different hydrophilic materials of indirect evaporative cooler (IEC) systems was carried out. The two plate heat exchangers were finished either with TiO2 coating or a novel hydrophilic Graphene coating. First, a three-dimensional mathematical model coupled with a Volume of Fluid (VOF) model and a continuum surface force (CSF) model for heat and mass transfer of IEC was developed. The surface tension was achieved by changing the contact angle and thermal conductivity. Simulation results obtained from the developed model with and without the hydrophilic coating were in good agreement with experimental results. The deviation is within ?10% which proved the good accuracy and reliability of the model. Second, the influence of hydrophilic coating on enthalpy efficiency, wet-bulb efficiency, enlargement coefficient and COP (coefficient of performance) of IEC was investigated under different boundary conditions. Compared with non-hydrophilic materials, the enthalpy efficiency, wet-bulb efficiency, enlargement coefficient and COP of IEC system coated with TiO2 increased by 5.33%, 9.91%, 0.25 and 3.22, respectively. The enthalpy efficiency, wet-bulb efficiency, enlargement coefficient and COP of the Graphene coated IEC system increased by 14.75%, 12.07%, 0.85 and 7.69, respectively, as compared to IEC without the hydrophilic coating. In addition, the enthalpy efficiency, wet-bulb efficiency, enlargement coefficient and COP of the Graphene coated IEC system increase by 11.67%, 7.76%, 0.76 and 6.08, respectively, as compared to the TiO2 coated IEC system.

» Author: Yuwen You, Guo Wang, Bin Yang, Chunmei Guo, Yiwei Ma, Baohua Cheng

» Publication Date: 15/02/2022

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