Assessment of Propane in North American Residential Air Conditioning

Three unitary split systems were evaluated for use with propane as the refrigerant. These three systems were then compared to systems using hydrochlorofluorocarbon (HCFC) R-22 and hydrofluorocarbon (HFC) R-410A for environmental effectiveness. The propane systems included one using safety measures, another using propane with flame suppressant, and one using a secondary heat transfer loop to isolate propane from residences. The performance for all the systems was evaluated through computer simulation. The system environmental effects were assessed using the Total Equivalent Warming Impact (TEWI) concept, by considering the refrigerant leakage and the energy use in North American applications. The system cost was estimated in order to evaluate the TEWI reduction per unit of investment. Other manufacturing issues are discussed also. Of the three unitary propane split systems, the system with safety features has the best performance and the lowest TEWL However, adding the safety features raises the initial unit cost about 30 percent. If this cost adder is used to increase the efficiency of an R-410A system, this will result in a significant reduction in TEWI. In other words, a high efficiency R-410A system has the best TEWI reduction per unit of investment in the unitary split system application within North American region. Extensive revision of the manufacturing process is necessary to handle propane safely in the plant. Besides good environmental properties, propane has good thermodynamic and heat transfer properties. For these reasons, propane should continue to be evaluated for those markets and applications where it provides the best environmental solution. In this study, propane does not provide the optimum environmental solution for unitary split systems in the North American market. Since the system performance was derived from computer modeling, more experimental work is required for further evaluation. INTRODUCTION Due to the ozone depletion problem, 39 countries of the world met in 1987 and established the Montreal ProtocoL According to this and the subsequent protocols, the production of HCFC is going to be limited and eventually will be phased out in year 2020. EPA is calling for a phase-out of R22 for new equipment application by the year 2010. Significant effort has been put into the search for R-22 alternatives, including HFCs, Hydrocarbons, C02, Ammonia, etc .. While different "green" products with new refrigerants have been introduced in many countries, the search for other new refrigerants continues. Propane (R290), one of the Hydrocarbons, has many advantages as a refrigerant, such as, it is a natural substance, has zero ozone depletion, has negligible Global Warming Potential (GWP), is compatible with mineral lubricant oils, and has good heat transfer characteristics. The major disadvantage of propane is that it is flammable. In Europe, some development is occurring and products are available with propane as the refrigerant. Those products use very little refrigerant.