An innovative charge optimization process for capillary tube based cooling systems.

• Methodology to minimize the energy consumption of household refrigerators. • Convertion of the pair needle valve-capillary tube into an equivalent tube diameter. • Empirical correlation to estimate the EC based on the restriction and charge. In the first part of this work an experimental apparatus was designed and constructed to map the energy consumption of a household refrigerator subjected to several combinations of refrigerant charge and expansion restriction. In the second part, the expansion restriction imposed by the pair metering valve-capillary tube was converted into an equivalent tube diameter applying two different procedures: dry nitrogen flow and mathematical modeling. An empirical correlation to estimate the energy consumption based on the capillary tube inner diameter and refrigerant charge was also developed and used during the minimization process. Different strategies were also explored in order to reduce the amount of experiments to a minimum. It was found that at least 14 data points, collected with three different refrigerant charges, are required to ensure the convergence of the energy consumption minimization process. [ABSTRACT FROM AUTHOR]