Retrofitting of a R-12 based domestic refrigerator to run on R-134a

Abstract

With the discovery of R134a, which has a negligible Ozone depletion potential, ODP (R11 is listed as 1.0 on the scale) and at least hundred orders of magnitude less Global warming potential (GWP) compared to CFCs, resulted the phasing out of the use of Freon-12 refrigerant in domestic refrigerators. As a result, continuing use of large number of domestic refrigerators run on Freon-12 and purchased prior to the introduction of phasing out mechanisms by the Montreal Protocol could be difficult if not impossible. Because, due to the differences in thermo-physical properties of R134a and Freon-12, modifications or replacement of main devices such as the compressor, condenser, capillary tube of the refrigeration cycle and the use of a compatible lubricant are required.

In the present study modifications to the capillary tube length is suggested as the possible modification to the existing system. This choice of modification was based on the cost effectiveness and the convenience. In short it is cheaper and convenient.

First a safe procedure of recovering the Freon-12 and the lubricant from the existing refrigerator and cleaning and preparing the system for recharging with the new refrigerant R134a was established. Performance tests were carried out to ensure that the refrigerator could function properly with the new refrigerant and the new lubricant, which is ployol ester and to compare the energy consumption & Coefficient of Performance (COP). Upon ensuring the proper function of the refrigerator with the new refrigerant R134a and the new lubricant, tests were carried out to compare the energy consumption and COP of the refrigerator with different capillary tube lengths namely, 25%, 30% and 35% length increments. The test results suggests that the domestic refrigerator designed to run with Freon-12 can be retrofitted to run with R134a successfully, with 30% increase in capillary tube length.