Abstract
In the present work, for the first time, an experimental and theoretical study of the heat transfer characteristics of a bubble type three-phase direct contact condenser has been carried out. The experiments were conducted using a Perspex column of 70 cm in total height and 4 cm inner diameter, as a direct contact condenser. The active column height throughout the experiments was 48 cm. Pentane vapour at three different initial temperatures (40℃, 43.5℃ and 47.5℃), was used as the dispersed phase while tap water at a constant temperature (19℃) was used as the continuous phase. Seven different dispersed phase mass flow rates and five different continuous phase mass flow rates were tested. The experiments considered the transient temperature distribution along the direct contact condenser, the steady-state temperature distribution, the volumetric heat transfer coefficient, the heat transfer rate per unit volume and the holdup ratio. Also, the efficiency and capital cost of the direct contact condenser were estimated, and the heat transfer of the three-phase direct contact condenser during flooding was studied. Theoretical models describing the direct contact condenser were developed. These models included the transient temperature distribution, the steady-state temperature distribution and the volumetric heat transfer coefficient. These models implicitly involved new derivations for the surface heat transfer coefficient, the two-phase bubble size, the relative velocity of two-phase bubbles, the drag coefficient and the added mass of the two-phase bubble. All expressions were derived analytically except for the transient temperature distribution along the condenser which was found numerically, using MATLAB. The results showed that the mass flow rate ratio has a significant effect on the heat transfer characteristics of the condenser, while the initial temperature of the dispersed phase has only a slight effect. The models developed were fitted the experimental data well.