Boiling Heat Transfer in a Horizontal Small-Diameter Tube

Abstract

Results of a study on boiling heat transfer of refrigerant R-113 in a small-diameter (2.92 mm) tube are reported. Local heat transfer coefficients are measured for a range of heat flux (8.8–90.75 kW/m2), mass flux (50–300 kg/m2s), and equilibrium mass quality (0–0.9). The measured coefficients are used to evaluate 10 different heat transfer correlations, some of which have been developed specifically for refrigerants. High heat fluxes and low mass fluxes are inherent in small channels, and this combination results in high boiling numbers. In addition, based on a flow pattern map developed from adiabatic experiments with air-water mixtures, it has been shown that small-diameter channels produce a slug flow pattern over a large range of parameters when compared with larger-diameter channels. The effects of high boiling number and slug flow pattern lead to domination by a nucleation mechanism. As a result, the two-phase correlations that predicted this dominance also predicted the data the best when they properly modeled the physical parameters. The correlation of Lazarek and Black (1982) predicted the data very well. It is also shown that a simple form, suggested by Stephan and Abdelsalam (1980) for nucleate pool boiling, correlates the data equally well; both correlations are within a mean deviation of less than 13 percent. Results are applicable to boiling in compact heat exchangers.

Boiling heat transfer with three fluids in small circular and rectangular channels

“…3, 4, 7, 8, and 12 lead one to conclude that over a broad range of heat flux, and in channels of two different geometries with three different fluids, nucleation is the dominant heat transfer mechanism for flow boiling in the small passages considered in this study. This agrees with previous investigations of flow boiling in small channels (Lazarek and Black 1982;Wambsganss et al 1993;Tran et al 1993;Peng and Wang 1993). The results shown in Figs.…”

“…Identification of a convection-dominant region in small channel boiling heat transfer allows one to reconcile an apparent disagreement between the results of this investigation and the results of others who found a nucleation-dominant mechanism (Lazarek and Black 1982;Wambsganss et al 1993;Tran et al 1993;Peng and Wang 1993), and the results of Robertson and coworkers (Robertson 1979(Robertson , 1983Robertson and Wadekar 1988;Wadekar 1992) who concluded from their tests with multichannel arrangements that nucleation is not an important mechanism. The finding of Robertson and coworkers that convection dominates was based on data obtained for very low values of wall superheat (<2.5*C), and indeed the results presented in this paper for very low wall superheats, also lead to this conclusion.…”

“…They can convenier ly be grouped as exchangers with offset strip fin passages (Panitsidis et al 1975;Galezha et al 1976;Yung et al 1980;Chen and Westwater 1984), exchangers with perforated fin passages (Panchal 1984(Panchal , 1989, multichannel arrangements with offset strip fins (Robertson, 1979(Robertson, , 1983Carey and Mandrusiak 1986;Mandrusiak et al 1988;Mandrusiak and Carey 1989), and multichannel arrangements with perforated fins (Robertson and Wadekar 1988;Wadekar 1992). Single-channel studies of flow boiling of refrigerant-113 (R-113) in a small-diameter circular tube (approximately 3 mm) have been reported by Lazarek and Black (1982) and Wambsganss et al (1993). Boiling in single, small rectangular passages has been reported by and Peng and Wang (1993).…”

“…The test apparatus and test procedure have already been described in some detail by Wambsganss et al (1993) and Tran et al (1993). Consequently, they are only summarized here for completeness.…”

“…As with the test apparatus and instrumentation discussed in the preceding section, the test procedure and data reduction methodology have already been described in detail by Wambsganss et al (1993) and Tran et al (1993) and are only summarized here for completeness.…”