Effect of concentration of falling film absorption heat and mass transfer of LiBr solution on horizontal enhanced heat transfer tube.

This paper presents the experimental results of falling film absorption heat and mass transfer on horizontal enhanced heat transfer tubes. The enhanced tube on the external surface has square frustum projection and this pitch of 26 projections lines-per-inch (ppi). A smooth tube is also tested for reference. The solution in the present tests used is lithium-bromide solution. The heat and mass transfer coefficient test is carried out absorption pressure of 0.8 kPa, the concentration at LiBr solution inlet of 63, 62 and 60 wt. %, the inlet cooling water temperature of 32°C, and film Reynolds number range of 7 to 20. For LiBr solution concentration inlet was 63 wt. %, the heat transfer coefficient of the enhanced tube is approximately 1.3 times higher than that of the smooth tube at low film Reynolds number. In addition, the heat transfer coefficient of enhanced tube at LiBr solution of 60 wt. % is approximately 2.0 times higher than that of the enhanced tube at LiBr solution of 63 wt. % in low film Reynolds number. However, that of enhanced tube at LiBr solution of 62 wt. % lower than that of the enhanced tube at LiBr solution of 63 wt. %. The mass transfer coefficient for the enhanced tubes increases with an increase solution concentration in this study.