Challenges in developing environmentally safe heat pumping systems

The advent of the global warming crisis has brought about a viewpoint, in many governments, that the halogen family of refrigerants should be replaced, in part or in toto, by the socalled natural refrigerants. For this proposal to be valid it is necessary to consider both the refrigerant's direct environmental impact and its life-long performance under field conditions. This is particularly true in the case of global warming because, for most applications, it is the heat pump's operating efficiency and its impact on the central power plant's emissions that is the dominating environmental factor. Any refrigerant must also meet a variety of other criteria that deal with durability, safety and costs. A simple comparison of basic fluid properties is conducted to indicate what system design considerations must be made if a refrigerant is to become an acceptable alternative. It is also reasoned that while computer models and laboratory prototypes are a necessary beginning, they are not sufficient to determine the true environmental impact of any system. Finally, the question is raised as to whether the refrigerant specification approach is the better path to an improved environment or if it is wiser to leave all options open for researchers and manufacturers to meet an environmental performance standard any way they choose.