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Abstract
Refrigerant 22, the most widely used in Refrigeration and Air Conditioning applications, is considered in the Ozone depleting substances. Since no pure refrigerant has properties close to R22 at this time, utilizing refrigerant blends is considered one of the suitable available alternatives. R407C is considered one of the strongest replacement candidates to R22, it is a ternary blend of refrigerants (R32/R125/R134a) with a composition (23/25/52) by mass.
The object of this research is divided into two parts. First, studying the behaviour of refrigerants R22 and R407C during condensation in the shell side of the condenser using simulation model that was compared with the experimental data from previous researches. The model results were agreed with the experimental data of condensation heat transfer coefficients and condenser capacities (Relative deviation less than 30 %) for mass flow rates greater than 260 gls.
The simulation results showed that the upper tubes in the bundle suffer from high degradation in the heat transfer coefficient that may reach 70 % when replacing R22 with R407C; however, the degradation decreases when raising the condensation temperature. Zeotropic refrigerant R407C behaves differently than pure refrigerant R22 during condensation where the heat transfer coefficient decreases at upper tubes then increases at bottom tubes contrary to that of R22, which continues to decrease to the end of condenser. The second part is to develop a theoretical model to elaborate how refrigerant behaviours affect the condenser sizing to remove a heat load. The results indicated that it is better to use R407C at higher cooling capacities and higher evaporating temperatures in order to keep the sizing ratio of a condenser that uses R407C to that uses R22 as minimum as possible