Neelkanth S. Gupte

Shell-Side Boiling in Flooded Refrigerant Evaporators Part I: Integral Finned Tubes

Convective vaporization data were obtained on a staggered tube bank made of 18.9 mm (0.75 inch) outside diameter integral fin tubes (1024 fins/m; 26 fins/inch) with an equilateral pitch-to-diameter ratio of 1.25. Data are presented for pure Refrigerant-11 with saturation temperatures of 4.4°C (40°F) and 26.7°C (80°F). The data span vapor qualities of 0 to 0.9, mass velocities (based on minimum flow cross section area) of 7 to 18 kg/m2·s (5,200 to 13,300 lb/h·ft2), and heat fluxes of 15 to 45 kW/m2 (4,800 to 14,300 Btu/h·ft2). The data were taken in an apparatus that allows independent control of vapor quality, mass velocity, and heat flux. In contrast to the data presented on enhanced tubes in Part 2, the convective effects strongly influence the integral finned tube performance. The Chen superposition model (with or without using a suppression factor) largely under-predicted the data. The data were correlated in the form of an asymptotic model. The correlations fit 92% of the data within ±20%.

Convective Vaporization Data for Pure Refrigerants in Tube Banks Part II: Enhanced Tubes

Convective vaporization data were obtained for two different enhanced tube geometries in a staggered tube bank made of 18.9 mm (0.75 inch) outside diameter tubes having an equilateral pitch-to-diameter ratio of 1.25. Data are presented for pure refrigerants R-11, R-123, and R-134a at saturation temperatures of 4.4°C (40°F) and 26.7°C (80°F). The data span vapor qualities of 0.0 to 0.9, mass velocities (based on minimum flow cross section area) of 10 to 30 kg/(m2· s) (7,400 to 22,000 lb/h·ft2), and heat fluxes of 15 to 45 kW/m2 (4,760 to 14,300 Btu/h·ft2). The apparatus allowed independent control of vapor quality, mass velocity, and heat flux. The data were correlated in the form of an asymptotic model with a root mean squared error of less than 15%. A modified superposition model with a suppression factor of unity correlated all the Tu-B (R-11 and R-123) data and approximately 90% of the W-SE (R-134a) data within ±20%. The experimental results for the two enhanced tube geometries tested show that the tub...