Local Bundle Boiling Heat Transfer Coefficients on a Turbo-BII HP Tube Bundle (RP-1089)

Abstract

Experiments have been performed for evaporation of refrigerants R-134a, R-410A, and R-507A on the outside of a horizontal bundle composed of enhanced boiling Turbo-BII HP tubes. Hot water flowing through the tubes was used as the heat source. Water temperature measurements were made at numerous axial locations within the tubes to obtain the water's temperature profile and, thus, measure twelve local heat transfer coefficients in the bundle. Pool boiling tests to measure the corresponding nucleate boiling curves were also obtained. Tests were conducted with a 20-tube bundle over ranges of heat flux (8-64 kW/m 2 ), mass flux (4-38 kg/[m 2 s]), and vapor quality (8-78%). The bundle test results showed a significant contribution of convection from rising bubbles to the heat transfer process with local heat transfer coefficients as large as 1.6 times those of nucleate pool boiling in the case of R-134a. Refrigerants R-507A and R-410A also showed bundle enhancement effects but less so than R-134a.

Local heat transfer coefficient for pool boiling of R-134a and R-123 on smooth and enhanced tubes

“…respectively. R-134a on TBIIHP data were compared with Robinson and Thome (2004), Ribatski and Thome (2006), Chen and Tuzla (1996), and Tatara and Payvar (2000). Data showed a good agreement with both Robinson and Thome (2004), and Ribatski and Thome (2006).…”

“…Test tubes were heated using a cartridge heater. The current data was also compared with Robinson and Thome (2004), where they had used water heated test tubes (similar to the current study). Data agreed with Kim and Choi's data better than with Pais and Webb, and Robinson and Thome.…”

“…Notice that for the high heat flux range, the heat flux exponent was close to zero, which agrees with the nearly flat trend of both curves beyond 50 kW/m² heat flux. Robinson and Thome (2004) presented a model for the TBIIHP tube with R-134a; this model was compared to the current study. Their model (presented in Equation (23) where heat flux is in W/m²) is also a power law model based on experimental data which presented good prediction to the current experimental data as shown in …”

“…The second study presented nucleate pool boiling of R-11, R-123, and R-134a on structured enhanced tubes having pores with connecting gaps. Pool boiling studies that utilized water-heated test sections are Robinson and Thome (2004) and Ribatski and Thome (2006). The two studies reported average heat transfer coefficients but no local measurements were reported.…”

“…The two studies reported average heat transfer coefficients but no local measurements were reported. The work done by Robinson and Thome (2004) involved measurement of the water temperature drop, which was used for determining the local heat transfer coefficient of bundle boiling. …”