An experimental study of falling film evaporation in vertical channels with perforated fins of a plate-fin heat exchanger

In this paper, the heat transfer characteristics of falling film evaporation of pure refrigerant HCFC123 were experimentally investigated in a pilot scale plate-fin heat exchanger with perforated fins. The experiments have been carried out under the conditions that the mass flux is in the range of 23 to 49 kg/m²s, the corresponding inlet Reynolds number from 200 to 500, the heat flux from 3.2 to 9.5 kW/m², and the evaporation pressure about 0.3 MPa. The variation laws of the local heat transfer coefficient versus the main parameters, including the inlet Reynolds number, heat flux and vapor quality were discussed. By introducing the two-phase convective multiplier F as a function of Lockhart-Martinelli parameter, a correlation for the two-phase forced convective component of the local boiling heat transfer coefficient was developed, and compared with correlations in open literature. By using a superposition method, the local boiling heat transfer coefficient that includes the contributions of forced convective boiling and nucleate boiling was analyzed. The predictions of local heat transfer coefficients were found to be in good agreement with experimental data.