Tube side condensation is important in air conditioning, automobile and various process industries applications. The phasing out of traditional CFC refrigerants due to their high Ozone depletion potential (ODP) has led to the use of blended Zeotropic refrigerants. Some of these blended refrigerants with almost negligible ODP exhibit heat transfer degradation in tubes during in-tube condensation due to additional thermal resistance of mass transfer and nonlinear property effects. The modern condensers are expected to be compact, with low refrigerant hold up and weight, implying smaller and thinner tubes. Enhanced tube geometries are the key to move in this direction. Micro fin tubes with different geometrical parameters are now widely being used in condensers, evaporators and coolers of various unitary air conditioning systems. These tubes give significant increase in heat transfer with relatively less pressure drop penalty. This paper provides a comprehensive review of various heat transfer correlations proposed by different authors for the condensation of pure and blended refrigerants in smooth and micro fin tubes. A new empirical correlation based on two phase multiplier approach using the experimental data of various researchers has been proposed. The correlation includes dimensionless parameters which closely reflect the physics of actual condensation flow conditions. The experimental data of Dobson& Chato (1994), Tang (1997), Liebenberg (2002) for smooth tubes and that of Kedzierski &Gonclaves (1997) and Tang (2002) for micro fin tubes was fitted on the proposed correlation. The correlation predicts the local heat transfer coefficient for pure and blended refrigerants in horizontal micro fin tubes with in ±15% range.
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