Falling Films on Arrays of Horizontal Tubes with R-134a, Part I: Boiling Heat Transfer Results for Four Types of Tubes

A new falling film heat transfer test facility has been built for the measurement of local heat transfer coefficients on a vertical array of horizontal tubes, including flow visualization capabilities, for use with refrigerants. Presently, the facility has been used for evaporation tests on four types of tubes at three tube pitches and three nominal heat flux levels for R-134a at 5°C. A new method for determining local heat transfer coefficients using hot water heating has been applied, and test results for a wide range of liquid film Reynolds numbers have been measured for arrays made of plain, Turbo-BII HP, Gewa-B, and High-Flux tubes. The results show that there is a transition to partial dryout as the film Reynolds number is reduced, marked by a sharp falloff in heat transfer. Above this transition, the heat transfer coefficients are nearly insensitive to the film Reynolds number, apparently because vigorous nucleate boiling is always seen in the liquid film. The corresponding nucleate pool boiling data for the four types of tubes were also measured for direct comparison purposes. Overall, about 15,000 local heat transfer data points were obtained in this study as a function of heat flux, film Reynolds number, tube spacing, and type.

[1]  Hsieh Shou-Shing,et al.  Nucleate boiling characteristics of R-114, distilled water (H2O) and R-134a on plain and rib-roughened tube geometries , 1994 .

[2]  P. J. Marto,et al.  Nucleate pool boiling of R-114 and R-114-oil mixtures from smooth and enhanced surfaces—I. Single tubes , 1995 .

[3]  John R. Thome,et al.  Falling Film Evaporation: State-of-the-Art Review of Recent Work , 1999 .

[4]  John R. Thome,et al.  Local Bundle Boiling Heat Transfer Coefficients on a Plain Tube Bundle (RP-1089) , 2004 .

[5]  M. Pate,et al.  Heat transfer of R-134a in single-tube spray evaporation including lubricant effects and enhanced surface results , 1995 .

[6]  M. Pate,et al.  The effects of nozzle height and orifice size on spray evaporation heat transfer performance for a low-finned, triangular-pitch tube bundle with R-134a , 1995 .

[7]  F. Mayinger,et al.  ENHANCEMENT OF HORIZONTAL TUBE SPRAY FILM EVAPORATORS , 1982 .

[8]  Chi-Chuan Wang,et al.  Pool boiling of R-22, R-124 and R-134a on a plain tube , 1997 .

[9]  R. Webb,et al.  Nucleate pool boiling data for five refrigerants on plain, integral-fin and enhanced tube geometries , 1992 .

[10]  J. Thome,et al.  Evaporation of Ammonia in a Smooth Horizontal Tube: Heat Transfer Measurements and Predictions , 1999 .

[11]  K. Stephan,et al.  Heat-transfer correlations for natural convection boiling , 1980 .

[12]  M. Cooper.  Heat Flow Rates in Saturated Nucleate Pool Boiling-A Wide-Ranging Examination Using Reduced Properties , 1984 .

[13]  J. Kelly,et al.  Spray evaporation heat transfer performance in R-123 in tube bundles , 1996 .

[14]  V. Gnielinski.  New equations for heat and mass transfer in turbulent pipe and channel flow , 1976 .

[15]  M. Pate,et al.  Effect of lubricant on spray evaporation heat transfer performance of R-134a and R-22 in tube bundles , 1996 .

[16]  A. Bergles,et al.  Horizontal-tube falling-film evaporation with structured surfaces , 1989 .

[17]  J. Thome,et al.  Convective Boiling and Condensation , 1972 .

[18]  B. M. Burnside,et al.  A comparison between HIGHFLUX and plain tubes, boiling pentane in a horizontal kettle reboiler , 2002 .

[19]  Anthony M. Jacobi,et al.  Falling-film evaporation on horizontal tubes—a critical review , 2005 .

[20]  X. Zeng,et al.  Evaporation heat transfer performance of nozzle-sprayed ammonia on a horizontal tube , 2000 .

[21]  P. Payvar,et al.  Pool boiling of pure R134a from a single Turbo-BII-HP tube , 2000 .