Experimental study on heat transfer coefficients of spray evaporation and pool boiling on plain tubes.

There is a great concern in our society in general, and in the refrigeration and air conditioning sectors in particular, about environmental and energetic issues. Reducing the charge of refrigerant in installations contributes to solve this problem and spray evaporators appear as interesting alternatives to pool boiling evaporators not only from this point of view, but also from safety, efficiency, cost and size points of view. We have determined experimentally both spray evaporation and pool boiling heat transfer coefficients (HTCs), using ammonia and titanium plain tubes, to compare both processes and to contribute to the existing database. In the paper we have detailed the experimental equipment used and the methodology followed. We have also exposed the data reduction process followed to obtain spray evaporation or pool boiling HTCs from the experimental data measured and we present and discuss the results obtained.