Abstract—The author introduces and analyses the twophase
pressure drop correlation for refrigerant R134a in the
condenser of a heat pump heating-cooling system. The
following correlation will be included: the Lockhart and
Martinelli, Friedel, Chrishom, Tran et al, Wang et al. and
the Wilson et al. The previously mentioned correlations
were analyzed numerically depending on mass velocity and
vapor quality. The aim of the analysis is to choose the
optimum model from the tested ones. The applied method of
analysis is numeric-graphic.