Heat transfer coefficients in two-phase flow for mixtures used in solar absorption refrigeration systems

This paper describes the experimental results obtained on the heat transfer in saturated nucleate boiling of refrigerant mixtures used in solar absorp tion refrigeration systems flowing upward in a uniformly heated vertical tu be. The mixtures analysed were water/ammonia, ammonia/lithium nitrate and w ater/lithium bromide. The concentration range for the water/ammonia was fro m 38 to 48wt%, for the ammonia/lithium nitrate was from 38 to 48wt% and for the water/lithium bromide was from 48 to 58 wt%. It was observed that the average heat transfer coefficients increased for the mixtures with an incre ase in the quality, the heat flux and the solution concentration. Comparing the values of the average heat transfer coefficients for the three mixture s, it was observed that the highest values were obtained for the ammonia/wa ter mixture. (C) 2000 Elsevier Science B.V. All rights reserved.