On the pressure drop in Plate Heat Exchangers used as desorbers in absorption chillers

The influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr–H2O and NH3–H2O solutions is studied. For the NH3–H2O solution, the pressure drop-temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr–H2O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposed.