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Nowadays, an increasing attention in environmental issues including the global warming effect and ozone layer depletion has been attracted. R22 is urged to be ruled out until 2020 and 2030 for developed and developing countries. R290 (propane) has been regarded as a promising alternative refrigerant for the air-conditionings. Comparing to other alternatives, R290 has zero ozone depletion potential and negligible GWP. However, R290 has different thermo-physical properties than conventional refrigerants and it would influence the application in tubes such as shear forces, gravity and surface tension. The condensation and evaporation behavior of R290 would has a great effect in designing suitable heat exchanger for R290. In recent years, researchers have made great efforts in studying different working fluids behaviors and multiple semi-empirical correlations have been established to predict the heat transfer and pressure drop. However, the study about R290 behavior is very limited. According to the past experiences in condensation and evaporation studies, the semi-empirical models may be not very accurate in the working conditions outside the range where they are established. This paper presents a detailed review of research work done on the condensation and evaporation of R290. It also gives a comparison between R290 and other working fluid behavior and makes a summarization on predicting correlations for R290 heat transfer and pressure drop. This paper is a starting point for future R290 studies and R290 applications in air conditioning systems. Â

The climate control load is the most significant auxiliary loads present in vehicles today. The peak climate control load of an AC system in sedan can be as large as the engine input power. As the attention on vehicle energy economy is rising worldwide, the energy-saving of mobile air conditioning is becoming more and more important. Most mobile AC systems nowadays draw air from outside the vehicle and cool it to the desired comfort level inside the vehicle. Lots of energy is wasted during this process due to continuously cooling the hotter outside air instead of cooling the “cooler” inside air. Compared to that, defaulting to recirculated cabin air will certainly be energy-saving. Though some studies have revealed the energy saving effectiveness under bench test conditions, it is still unclear how much energy can be saved when mobile AC systems are operated in different climates and driving patterns. The GREEN-MAC-LCCP tool is modelled to evaluate the life cycle climate performance of mobile AC system, and it is well-accepted. This tool is capable of analysing the full cycle of greenhouse gas emissions (GHG) of alternative refrigerant systems and different system structures. In this article, the energy-saving effect of defaulting to recirculated cabin air is evaluated using GREEN-MAC-LCCP. It is found that 7%-48% of energy saving can be achieved under the calculated climate conditions.