For rational design of evaporators and for developing correlations for the same, it is necessary to have detailed test data. The test data should give heat transfer and pressure drop rates as a function of pertinent parameters ( such as mass flow rate, vapor quality, pressure, heat flux). Information on visual observations ( for example flow patterns, extent of pipe surface wetted, behavior of oil) are also very useful.

Many such studies have been carried out for halocarbon refrigerants and a wide variety of experimental data are available in published papers, reports, doctorate theses, etc. The situation for ammonia evaporators is very different. Much of the experimental work was done long ago when the parameters affecting heat transfer and pressure drop were not known fully. Consequently, the published data from those studies do not contain important parameters such as mass flow rate and vapor quality, thus making it impossible to analyze and generalize them. Examples of such work are those of Cleis and Schwind. To the author's knowledge, the only analyzable data for ammonia evaporators containing oil, which are accesible to the general pUblic, are those shown graphically in a paper by Shah. Some analyzable data for oil-free ammonia are to be found in a paper by Noel but their range is confined to subcooled boiling region.