Experimental investigation of the condensation of R134a and R404A refrigerants in a long, water-cooled, serpentine coils

• Published in: International journal of heat and mass transfer Vol. 67; pp. 602 - 612
• Main Authors: Charun, Henryk, Bohdal, Tadeusz, Czapp, Marian
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2013
• Subjects: Condensation; Heat transfer; Long serpentine coil; Pressure drop; Pressure drop; Condensation; Heat transfer; Long serpentine coil
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2013.08.020

The subject of the present analysis is the condensation of the environmentally friendly refrigerants R134a and R404A in long, serpentine pipe coils, for Lc/d>800–1000, where Lc is the total length of the coiled pipe, and d is its internal diameter. During condensation in a coiled-pipe condenser, heat exchange occurs in three regimes, i.e., the superheat removal regimes, the two-phase condensation regimes and the condensate subcooling regimes. The length L of the two-phase area significantly affects the values of the average heat transfer coefficient α and the flow resistance (Δp/L) in this area. On the basis of experimental investigations of the condensation process in a long, water-cooled serpentine coil with five pipe coils of differing dimensions, it was established that the condensation mechanism in a long coil pipe differs substantially from that in a horizontal pipe. New experimental correlations were developed to calculate the average heat transfer coefficient and flow resistance in the two-phase area. In these correlations, the dimensions of the two-phase area are characterized by the geometric index L/d. The correlations developed in this study may be useful in the design of water-cooled serpentine-coil condensers.