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Heat pumps offer a great opportunity of heating buildings on renewable energy sources. A small, cost-efficient and environment-friendly implementation are ammoniawater absorption heat pumps. One of its critical components in terms of efficiency, size and cost is the absorber. In this thesis the physical processes inside an ammoniawater spray absorber chamber were analyzed, modeled and simulated with the objective of optimizing the absorber efficiency by determining the influence of spray and nozzle properties on the absorption process. Effects of drop diameter and velocity were estimated analytically by simple approximations and by calculations in LibreOffice spreadsheets. The joint distribution of drop diameter velocity in a spray produced by a certain nozzle was modeled using both empirical equations and abinitio methods like the maximum entropy formalism (MEF) by the current state of scientific and engineering knowledge. The model of a swirl nozzle thus obtained was implemented in C++ as a part of an OpenFOAM solver. Using an existing, specifically built absorption library, the author was provided with, several simulations were conducted varying the absorption chamber geometries and the nozzle types. The results of these simulation showed that the heat transfer from the drops to the ammonia vapor atmosphere in the absorption chamber and subsequently from the chamber atmosphere to the chamber walls is the crucial parameter determining the absorption rate and the final ammonia concentration. In literature, several approaches can be found to determine the absorption rate of a single, representative drop in a spray, either by analytical or numerical methods. However, so far no study considered the effects of the whole spray consisting of a huge number of drops with varying size and velocity. By the model and setup developed in this work, effects like heating up of the absorber chamber or flow induced by momentum transfer from the drops to the fluid, can be taken into account for the first time.