Experimental analysis of HFC-134a expansion through small-bore adiabatic capillary tubes

Abstract

This paper comes out with an experimental investigation of the expansion of refrigerant HFC-134a through adiabatic capillary tubes with internal diameters ranging from 0.23 mm to 0.53 mm aiming at the so-called mesocooling applications. To this end, an experimental apparatus was designed and constructed to emulate the operating conditions of mesoscale refrigerating devices, with condensing pressures ranging from 9 to 19 bar, and inlet refrigerant subcooling ranging from 5 to 10 K. The tube length was varied from 1 to 2 m. The tests were carried out following a factorial design. The experimental data were used to assess the mass flow rate prediction capabilities of an explicit, algebraic model for adiabatic capillary tubes devised in a prior work. The results revealed that the model is not suitable for small-bore capillary tubes. Correction factors were proposed, so that the model predictions for more than 90% of the experimental dataset fell within ±10% error bounds.