3-DIMENSIONAL EVAPORATION PROCESS IN AQUA-AMMONIA ABSORPTION REFRIGERATORS USING HELIUM AS INERT-GAS

Helium is proposed as a hydrogen substitute in inert gas absorption re frigerators, in order to eliminate the danger of a possible explosion. Attention is focused on the evaporator of such units and a solution i s obtained for the three-dimensional evaporation process of a liquid a mmonia stream of circular meniscus cross-section flowing parallel to a n ammonia-helium gas mixture. The analysis is based on a finite-differ ence solution of the three-dimensional momentum, heat and mass transfe r differential equations within a nearly horizontal evaporation tube. Calculations are also performed using hydrogen instead of helium in or der to compare their behaviour as inert gases in aqua-ammonia absorpti on refrigerators. Under corresponding conditions, higher entropy incre ase and cooling capacity are observed in the case of helium. Generally , the behaviour of the latter is deemed satisfactory and therefore hel ium may replace hydrogen.