Condensation heat transfer coefficients of R22, R407C, and R410A on a horizontal plain, low fin, and turbo-C tubes

Condensation heat transfer coefficients of flammable refrigerants

“…In fact, however, the condensate film is wavy even at low Reynolds numbers causing a convection current and also reducing the film thickness, which was observed through the sight glass. This phenomenon that measured HTCs were higher than those calculated by Nusselt's equation was also observed for other fluids as well [9,10,14]. This comparison showed that the present data for the flammable refrigerants are quite reasonable.…”

“…2, HTCs of HCFC22 and HFC134a from Refs. [9,10] are included for reference. Data of various flammable refrigerants of different vapor pressures exhibited a typical trend that external condensation HTCs decrease as the wall subcooling increases.…”

“…So far, data for eleven refrigerants have been measured including CFC11, CFC12, HCFC22, HCFC123, HFC134a [9,10] and six fluids covered in this study. A regression analysis showed that increasing the constant in Nusselt's equation by 9%, as in Eq.…”

“…This work is designed mainly to provide reliable data to the refrigeration industry for the design and manufacture of high efficiency condensers with those fluids. In fact, this is a sequel paper to our previous reports on the external condensation HTCs of CFC11 and CFC12 and their alternative refrigerants on horizontal tubes [9] and HCFC22 and R407C and R410A [10].…”

Theoretical and experimental investigations of a two-phase thermosyphon solar water heater

“…The heat transfer coefficient given by Holman [18] and Jung et al [19] and considered the tilt angle (q), the inner diameter of fin tube (D i ) and the fin tube length (L c ). Therefore, the film-condensation thermal resistance can be expressed as:…”