Kengo Tanaka, Yuki Iwano, Yasushi Kihara, Masato Sorimachi, Hisashi Ayuzawa


We have been developing a system in which waste heat from an automotive engine is stored during driving to warm up the engine oil, the transmission oil and others with the stored heat at a cold start. With the early warming up, the fuel efficiency can be improved because not only the combustion efficiency at a starting-up is improved but also because the friction loss of oil is reduced. Calcium oxide is typical as a heat storage material to make use of the heat in the temperature range of the exhaust heat. But, there is a problem that the device becomes large in size, because it is necessary to widen the surface area of the material to accelerate its reaction with the water vapor to gain a larger output. This is a barrier detrimental to the automotive use. We have been examining a compact heat storage system but with a high output and a high density which are realized with a combination of the heat-pipe technology and the heat storage material to make the material react directly with water (liquid) not with water vapor (gas). In our preliminary evaluation with a theoretical mock-up model, we have already got the data that shows that the heat output density was as high as double or more than that of the present heat storages.

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