Experimental investigation on flow condensation in horizontal tubes filled with annular metal foam

This work studies the heat transfer and pressure drop of water vapor flow condensation in horizontal tubes filled with annular metal foam of three different sizes (10, 15 and 20 PPI). The range of vapor mass flow rate is 20-100 kg/h and cooling water flow rate is 1-3 m3/h. The flow condensation characteristic in metal foam tubes is presented and compared with corresponding micro-fin tubes by using unit mass efficiency coefficient method. The effects of metal foam size, inlet vapor pressure, vapor mass flow rate, and cooling water temperature on heat transfer and pressure drop are examined and analyzed. Heat transfer and pressure drop correlations for horizontal tubes with annular metal foam are obtained by curve-fitting of the experimental values. The results indicate that the introduction of metal foam enhances the heat transfer although resulting in a larger pressure drop. Metal foam of 10 PPI size exhibits the superior performance. The average heat transfer coefficient is also observed to increase with higher inlet vapor pressure, higher vapor mass flow rate and higher cooling water temperature.