installation of an ejector or its refrigeration system also can improve the thermal efficiency of the ordinary vapour compression refrigerator. Tomasek and Radermacher propose the use of ejector in the domestic fridge-freezer. Usually, a standard household fridge-freezer is equipped with two evaporators (fresh food and freezer compartment) and only one compressor. The required electricity used to compress the refrigerant from the freezer evaporator to the condenser level is high. In Fig. 12a, the installation of ejector reduces this pressure different, thus, less specific work and the system COP is improved. The calculated performance of ejector- combined system was compared to that of single-compressor (original) and two-compressor (dual-loop) system. Even though the ejector-combined system claimed 12.4% performance improvement from the single-compressor system, the dual-loop system has the highest COP improvement. It is known that the increasing of sub-cooling level before entering the expansion device can increase COP of the conventional vapour compression system. Moreover, a plenty amount or heat is rejected as wasted from the very high temperature refrigerant of the compressor outlet. The combined ejector-compression machine of Huang et al. allows the wasted heat from the superheated vapour refrigerant in the compression sub-cycle to drive the ejector sub-cycle (Fig. 12b). The cooling effect obtained from the ejector-cooling device is used to cool the liquid condensate of compression sub-cycle to a sub-cooled state to increase the COP of the system. Their analytic and experimental results verified the feasibility of the system. The COP of the system was, on average, 10% improved and a maximum of 24% improvement was claimed.