A generalized performance prediction method for adiabatic capillary tubes

Conference · Thu Dec 31 04:00:00 EST 1998

OSTI ID:687575

Bittle, R R ^[1]; Wolf, D A ^[2]; Pate, M B ^[3]

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1. Texas Christian Univ., Fort Worth, TX (United States). Dept. of Engineering
2. J.L. Hall Engineering Services, Ames, IA (United States)
3. Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering

Generalized dimensionless correlations were developed to predict refrigerant mass flow rate in an adiabatic capillary tube, for both subcooled and quality inlet conditions. Dimensionless parameters were created using the Buckingham Pi Theorem. These parameters were based on the effects of tube geometry, inlet conditions, and fluid properties. The correlations were based on experimental performance data with refrigerants R-134a, R-22, and R-410A that encompass an extensive range of operating conditions, including: condensing temperatures from 79 F to 127 F (26C to 53 C), capillary tube inner diameters from 0.026 to 0.090 in (0.66 to 2.29 mm), capillary tube lengths from 20 to 200 in (508 to 5080 mm), and inlet conditions from 30 F (16.7 C) subcooled to 35% quality. Corresponding to this range of refrigerants, capillary tube geometry, and operating conditions, the experimental mass flow rate range was between 3 and 375 lb{sub m}/h (1.4 to 170 kg/h). Independent assessments of both correlations were made by comparing predictions to measured performance with R-152a. These data fell within the {+-}6% and {+-}13% prediction intervals for the subcooled inlet and quality inlet correlations, respectively. The accuracy of the subcooled inlet correlation was further assessed by comparing predicted performance to measured data reported by other investigators with refrigerants R-12, R-134a, and R-22. It was shown that the subcooled inlet correlation predicted the bulk of these flow data to within {+-}10%. However, when compared to reported data with R600a (isobutane), however, the subcooled inlet correlation over-predicted mass flow rate by 0 to 20%.

• OSTI ID: 687575
• Report Number(s): CONF-980650--
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
CAPILLARY FLOW
COMPARATIVE EVALUATIONS
CORRELATIONS
MASS TRANSFER
PERFORMANCE
REFRIGERANTS
SUBCOOLING