DENSO Corp. said this week it has developed the world’s first passenger vehicle air conditioning system that uses ejector technology. The ejector, which is a small refrigerant injector, contributes to an overall reduction in power consumption. The system will be installed on the new Prius, introduced by Toyota this month.
“With increasing demand for technologies to reduce carbon dioxide emissions and preserve the environment, DENSO has been accelerating its efforts to develop more efficient air conditioning systems,” said Akio Shikamura, managing officer responsible for DENSO’s Thermal Systems Business Group. “The new air conditioning system reduces the compressor’s power consumption by up to about 25 percent, compared to conventional car air conditioning systems, and thus contributes to fuel savings.”
Much of the energy consumed by a vehicle’s air conditioning system is used by the compressor to compress the refrigerant. In conventional air conditioning systems, an expansion valve is used to reduce the pressure of the refrigerant before passing it through the evaporator to cool the air. DENSO’s new system uses an ejector instead of an expansion valve. The ejector recovers expansion energy, which was previously lost in the expansion valve, and converts it into pressure energy. This, reduces the compressor’s workload and helps reduce the air conditioner’s overall power consumption.
DENSO has applied ejector technology to truck refrigeration units and household CO2 heat-pump water heaters. Previously, the conventional ejector was not small enough to be installed in vehicle air conditioning systems. DENSO overcame this challenge with its new air conditioning system by integrating the ejector into the evaporator tank, where refrigerant flows. This new design eliminates the need for the ejector to have a thicker structure to withstand external pressure and also eliminates pipe connection parts needed to connect the ejector with the evaporator, which helps reduce the size of the ejector. The ejector cycle system evaporator (ECS evaporator), which is equivalent to the size of a conventional evaporator, can also be applied to conventional air conditioning systems.
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