Retrofits and options for the alternatives to HCFC-22

HCFC-22, widely used in variety of refrigerating/heating equipment, has been scheduled to be phased out by Montreal Protocol. This decision will result in significant reduction of ozone depletion and global warming, holding on the climate benefits accrued so far. In this paper, significant focuses were paid on the HCFC-22 elimination policies, advanced technologies, feasibility substitutes, revolutionary innovations, assessment strategy and developing tendency. The latest developing situation of R744, R717, HC-290, RE170, HFC-32, HFC-161, HFC-152a, HFO-1234yf, HFO-1234ze (E) and their blends were summarized and evaluated technically. Currently there has been no such kind of fluids which can replace HCFC-22 perfectly in most of existing equipment. Many factors must be taken into consideration when selecting an alternative, such as thermodynamic property, environmental impact, system efficiency, technology, flammability, toxicity, cost, policy etc., which can be regarded as a multi-objective decision problem. It is predicted to be increasingly important to research the flammable characteristics of refrigerants, including flammable limits, ignition energy, heat and product of combustion. Special security arrangements were suggested when operating with the flammable refrigerants, covering the whole lifetime. In consideration of current situations, the diversified solutions are the inevitable trends on the basic of comprehensive comparison.