Abstract
The quasi local heat transfer coefficients of R22 and R407C in the coaxial counterflow condenser (20 mm ID) of a
refrigerating vapour compression plant have been experimentally measured. The experimental conditions under which
the heat transfer coefficients were determined reflect a typical working situation for small scale refrigeration systems.
The plant runs with low mass fluxes of refrigerant within the range of 45.5–120 kg/m2/s. During the experimental tests
the pressure at the inlet of the test condenser varies within a fixed range between 15.2 and 14.3 bar. The results illustrate
that the R22 heat transfer coefficient is always greater than that of R407C. Furthermore, comparisons between the
experimental data and the values predicted by means of the most credited literature relationships for gravity-driven
condensation are reported.