Experimental investigation on the flow behaviour in a bubble pump of diffusion absorption refrigeration systems

An experimental investigation on the performance of a bubble pump for diffusion absorption refrigeration (DAR) systems was carried-out. The characteristics and operating conditions of the bubble pump determine the efficiency of the DAR systems. An experimental set-up operating in continuous mode was designed, built-up and successfully operated as a bubble pump. Experiments were performed by changing some of the parameters affecting the bubble pump performance. The experimental results showed that the performance of the bubble pump was mainly dependent on the driving heat input and the submersion ratio. Driving heat inputs applied were between 20 W and 200 W for a suitable size of the pump tubes. Three submersion ratios were tested, namely 25%, 35% and 45%. The results obtained showed that an oscillating flow was present in the operation of the bubble pump and the frequency of oscillation increased with the increase of the submersion ratio. The average mass flow rate of the refrigerant (ammonia) pumped increased with increase in the heating power; however, mass flow rates of the poor and rich solutions were function of the flow regime. In addition, experimental results were used to determine the optimal heating power for the different submersion ratios considered in this study. The optimal heating power ranged from 30 W to 130 W for a submersion ratio of 25% and from 30 W to 80 W for the submersion ratios of 35% and 45%.