A series of study has been performed on the metal hydride particle beds of Ti 0.15 Zr 0.85 Cr 0.9 Fe 0.6 Ni 0.2 Mn 0.3 Cu 0.05 (MH-1, using for heat source), Ti 0.73 Zr 0.27 Cr 1.2 Fe 0.3 Ni 0.1 Mn 0.4 Cu 0.05 (MH-2, using for cooling load) to measure the effective thermal conductivities. The effective thermal conductivities of activated and oxidized MH particle bed in helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range (<0.5 MPa). And that influence decreases rapidly with increase of gas pressure. The reason of pressure dependence at low pressure range is that the mean free path of gas becomes greater than effective thickness of gas film which is important to the heat transfer mechanism of particle bed. In order to enhance the poor thermal conductivity of metal hydride particle bed, carbon fiber mixing method has been used in this study. Three types, two insert methods and five mass percentages of carbon fiber have been examined and compared. The highest effective thermal conductivity of MH particle bed has been reached with Type B carbon fiber which has second higher thermal conductivity, and 2 weight percentage. This method has acquired 5-6 times higher thermal conductivity than pure metal hydride particle beds with quite low quantity of additives, only 2 mass% of carbon fiber. This is a good result comparing to other method which can reach higher effective thermal conductivity but needs much higher percentage of additives too.

Act of exchange from conventional refrigerant like 1,1,1,2-tetrafluoroethane to moderate molecular showing low global warming potential (GWP) is going on. Substituted refrigerants with low GWP are designed to readily decompose in atmosphere. It is, therefore, feared that the life shortening of the refrigerant is accelerated in the presence of mechanical parts of vehicle air conditioner including metal(s). In order to evaluate the stability in the short term, refrigerants including 2,3,3,3-tetrafluoropropylene with low GWP was contacted many times with highly dispersed metal on carrier in the closed circulating system. Finally, the evaluation of relative stability of refrigerants was successfully achieved within ca. 1.5 hours. Thus the evaluation term was able to shorten dramatically compared to the conventional method.

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In previous research, we have been focusing on the performance of the each element heat transfer and hydraulic performance of refrigeration cycle. Experimental investigations have been repeated several times, and finally, we have substantial database including the effect of lubricant oil. Moreover, the maldistribution of two-phase in an evaporator can be also predicted from the experimental database. Under these circumstances, this study is intended to effectively put the construction of an automotive CO2 air conditioning system into practical design use through the simulation using the above-mentioned database. This paper describes the refrigeration cycle performance prediction of each element (e.g., an evaporator, a gas-cooler, and so on) by a simulation using substantial database and various available correlations proposed by us and several other researchers. In the performance prediction model of heat exchangers, local heat transfer and flow characteristics are considered and, in addition, the effects of lubricant oil on heat transfer and pressure drop are duly considered. The comparison is also made between simulation results and bench test results using a real automotive air conditioning system. Finally, the developed simulation method can predict the cooling capacity successfully within ±10% for A/C system simulation. By incorporating the lubricant oil effect, the simulation results are improved to ±5% and ±15% for the cooling capacity and pressure drop for evaporator simulation, respectively.

In this study, we aim at developing the heat driven type water cooler using metal hydride (abbr., MH) alloy. Heat driven type MH water cooler is one of the chemical heat pumps, and the endothermic reaction on the cooling part MH (to put it simply, MH2) is used for the cooling. Because MH is too expensive (200∼300 $ per 1kg) and has an unfavorable activation characteristic, this cooler has not been used generally yet. In order to increase the system performance, we use a new TiFe alloy, which has been developed by co-researcher, to the heat source part MH (to put it simply, MH1). Moreover, to improve the cooling load per MH mass, we mix the brush type carbon fiber, 2 mass% into MH beds. By this method, the cooling load per MH mass is been increased to 0.078 kW/kg (MH2).