Performance of a packed bed absorber for aqua ammonia absorption refrigeration system

A mathematical model of a packed bed absorber for aqua-ammonia absorption r efrigeration system is presented. The model is used to predict the performa nce of the bed at various design and operating conditions. The governing eq uations and the boundary conditions are derived to predict the bed performa nce. A numerical integral method and an iteration scheme are used to solve the governing one dimensional, non-linear simultaneous differential equatio ns which are subjected to three point boundary value problem. A computer pr ogram is prepared and carefully debugged to solve the governing equations w ith the help of some supporting equations to describe the properties of the working fluids and the heat and mass transfer coefficients in the bed. The analysis show that the absorption process is affected by the following par ameters: the volumetric heat rejection model, bed height, vapor and solutio n flow rates to the bed and the inlet conditions; and packing material type . The effect of changing each of those parameters on the performance of the bed is studied after suggesting a model for the volumetric heat rejection from the bed. The results showed that changing the bed pressure and/or the vapor inlet temperature have negligible effect on the performance of the be d. Changing other parameters are found to affect the performance of the bed by different degrees. Also, the results show that within the present range of parameters, a bed height less than 0.7 m guarantees an absorption effic iency better than 91%. (C) 1999 Elsevier Science Ltd and IIR. All rights re served.