دانلود رایگان مقاله بررسی رفتار جریان در پمپ حباب سیستم های انتشار تبرید جذبی

Abstract

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%.

4. Conclusions

An experimental set-up was built-up to test the performance of an NH3/H2O bubble pump of 1.6 m length and 6 mm inner tube diameter. The aqueous solution of ammonia was heated by a heat transfer fluid flowing in the annular space. Driving heat input was in the range of 20–200 W and the average cooling water temperature was 26 °C. Pressure and temperature at different points of the set-up were registered and stored by a data acquisition system. The experimental data showed the oscillation of pressure at different values of the submersion ratio. Pressures prevailing in the separator and the reservoir were similar at a submersion ration of 25% and increased for the submersion ratios of 35% and 45%. The average mass flow rate of the refrigerant (ammonia) increased linearly by increasing the heating power, whereas the poor and rich solution mass flow rates increase to achieve a maximum value and then decreased as heat input was increased due to the transition of flow regime. Experimental data of the mass flow rate of the poor solution was used to establish the optimal heating power for different values of the submersion ratio. This 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%.