In this master thesis experimental analysis of a heat pump in a tumble dryer was carried out. We described theoretical background of vapor compressor cycle and presented calculation procedure for finned tube heat exchanger based on ɛ-NTU method. Experimental system where the measurements were taking place was shown in detail, including every single measuring point, used equipment and test steps. The main goal of this thesis was to develope a numerical model of finned tube heat exchanger - a condenser. The numerical model was used to help us find an optimal condenser size, depending on given input data. Measured data and data analysis was presented with aim to use experimental results for numerical model validation. Depending on the numerically determined outlet temperatures of air and refrigerant, we found out that decreasing condenser area for 1/7 of its initial size, reduces heat power for less than 10%. With this the superheated area of the condenser, which originally presented 1/3 of overall condenser size, was reduced for one half.