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The effect of the amount of refrigerant on automotive air conditioning system behavior was clarified through simulations and experiments. It has been revealed that the best way to measure the amount of refrigerant in an air-conditioning system is to measure the liquid-gas flow ratio in the liquid line. In order to measure the liquid-gas flow ratio, a mechanical sensor for fluids was developed and applied to a refrigerant monitoring system which can identify when the amount of refrigerant drops to 60% of the regular level.

When truck drivers rest in the truck sleeper cabin in the summer, air conditioning for the sleeper is highly desirable. Current practice is to run the engine for air conditioning, however, this practice wastes fuel and is environmentally unsound. This “Cold storage type cooling system” can cool the truck sleeper cabin without running the engine when the truck is parked and thus would be preferable from the view-point of fuel savings and environmental protection. The system we developed can be added to existing air conditioning systems and essentially consists of “cold storage cells” containing water as the cold storage material. The cold storage cells are fitted between evaporator tubes. By making the refrigerant alternately flow between the main evaporator and cold storage evaporator, the cold storage cells are charged while the truck is driving. When the truck is stopped, the sleeper cabin can be cooled by allowing the “cold storage cells” to discharge.

The important problems to be tackled from the point of view of preventing global warming are to save the power consumption of car air conditioning systems and reducing the refrigerant used in those systems. Our approach to the task is to enhance system efficiency by utilizing sub-cooling at the outlet of the condenser and also to reduce the amount of refrigerant through a refrigerant behavior pattern analysis. This approach has created a simple system construction using an integrated condenser/receiver device.