Evaluation of the column components size on the vapour enrichment and system performance in small power NH3–H2O absorption refrigeration machines

This paper presents an analysis of the influence of the distillation column components size on the vapour enrichment and system performance in small power NH3–H2O absorption machines with partial condensation. It is known that ammonia enrichment is required in this type of systems; otherwise water accumulates in the evaporator and strongly deteriorates the system performance and efficiency. The distillation column analysed consists of a stripping adiabatic section below the column feed point and an adiabatic rectifying packed section over it. The partial condensation of the vapour is produced at the top of the column by means of a heat integrated rectifier with the strong solution as coolant and a water cooled rectifier. Differential mathematical models based on mass and energy balances and heat and mass transfer equations have been developed for each one of the column sections and rectifiers, which allow defining their real dimensions. Results are shown for a given practical application. Specific geometric dimensions of the column components are considered. Different distillation column configurations are analysed by selecting and discarding the use of the possible components of the column and by changing their dimensions. The analysis and comparison of the different column arrangements has been based on the system COP and on the column dimensions.