Thus, utilization of the waste heat in refrigeration systems promotes mitigating the problems related to the environment, particularly by reduction of CO2 emission from combustion of fossil fuels in boilers of utility power plants. Although jet refrigeration systems seem to provide many advantages, further development is required to improve their performance and reduce the unit cost. The aim of this paper is to provide basic background knowledge and a review of existing literature on ejectors and their applications in refrigeration cycles.