Abstract This work presents experimental data for capillary tubes commonly used as expansion devices in household refrigerators and freezers, employing HC-600a, HFC-134a, and CFC-12 as working fluids. Capillary tubes of various lengths and diameters have been tested at different condensing pressures and with varying degrees of subcooling. Choked conditions prevailed in all runs. The test facility and the experimental procedures are described in detail. The operating conditions and the geometry of the capillary tubes (internal diameter, length and wall roughness) were evaluated with care. The effect of the pressure taps on the flow pattern was evaluated by measuring the mass flow rates and the temperature profiles along the same capillary tubes, with and without pressure taps. An appropriate set of data was obtained by measuring the pressure and temperature profiles in a suitable manner. This data set was then used to investigate the suitability of available equations to estimate the single-phase friction factor, the underpressure of vaporization, and also to calculate the entrance contraction loss factor.
Melo et al. (Sun,) studied this question.
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