In recent years, most accurate equations of state for alternative refrigerants and their mixtures can easily be used via convenient software package, e.g., REFPROP. In the present paper, we described the current state-of-the-art equations of state for refrigerant mixtures including hydrocarbons as components. Throughout our discussion, the limitation of the available experimental data and the necessity of the improvement against the arbitrary fitting of recent modeling were confirmed. The enough number of reliable experimental data, especially for properties in the higher pressures and temperatures and for derived properties, should be accumulated in the near future for the development of the physically-sound theoretical background. The present review argued about the possibility of the progress for the future thermodynamic property modeling throughout the detailed discussion regarding the several types of the equations of state as well as the recent innovative measurement technique.

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Hydrogen piping, the electric power line, and exhaust heat recovery piping of the distributed fuel cells are connected with network, and operational planning is carried out. Reduction of the efficiency in partial load is improved by operation of the geo-thermal heat pump linked to the fuel cell network. The energy demand pattern of the individual houses in Sapporo was introduced. And the analysis method aiming at minimization of the fuel rate by the genetic algorithm was described. The fuel cell network system of an analysis example assumed connecting the fuel cell co-generation of five houses. When geo-thermal heat pump was introduced into fuel cell network system stated in this paper, fuel consumption was reduced 6% rather than the conventional method

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The present study has proven a new dehumidifying system that aimed to reduce the sensible heat factor(SHF) of cooling process without using additional heat to relieve the internationally indicated conflict between energy saving and dehumidification necessary for keeping adequate indoor air quality (IAQ). In this system, we used intermediate pressure refrigerant in a vapor compression refrigerating cycle as heat transfer medium of a characteristic heat exchanger to precool the process air entering into an evaporator as well as to reheat the process air leaving from the evaporator. By this system, the present results achieved higher moisture removal and consequently higher efficiency of dehumidifying process. In addition to this fact, since this system has capability of integration into air-conditioning apparatus(HVAC system), it will be able to work for wide range of cooling load by variable SHF function. In the present paper, technical information, experimental results, and simulation results which assumed to apply this system into HVAC system are reported.

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Simulation analysis was carried out to study the partial load characteristics of three different types of double-effect LiBr-water absorption cycle, namely series flow, parallel flow and reverse flow. A computer program was developed for this study to simulate the behavior of the absorption cycles equipped with flow rate control of absorbent, cooling water and chilling water on partial load. The effects of the flow rate control on the coefficient of performance (COP), the maximum temperature and maximum pressure were studied. The results show that not only flow rate control of absorbent is essential for high COP on the partial load, but also flow rate control of cooling water and chilling water is recommendable to save the power of pumping.

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In case of the high humidity, mist particles occur near the cooling surface located in the moist air, so that the vapor concentration decreases and the temperature increase due to phase change of vapor i.e. condensation. Therefore the mist generation affects on both heat and mass transfer. In this present study, the diameter and velocity of the mist particles were measured simultaneously by using PDPA. The mist layer thickness was also optically measured. In addition, a set of boundary layer equations -continuity, momentum, energy and diffusion equation- was solved with satisfaction of the saturated condition, and were obtained analytically temperature and vapor concentration profile. As a result, the mist layer thickness is represented as a function of the Grashof number. And, the velocity of mist particle obtained experimentally agrees wel1 with the analytical velocity of natural convection without the mist formation. The mist particles with a large diameter exist near the frost surface, and the small mist particles distributes apart from the frost surface.

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Ammonia vapor absorption has been investigated experimentally by allowing superheated ammonia vapor to flow into a test cell to be absorbed into stagnant pool of al11monia water mixtures of different ammonia initial mass fraction Ci. The temperatures in the liquid and vapor and pressure in the cell are measured during absorption to estimate mass diffusion flux, which has been estimated by two ways where the first one is the Tillner-Roth and Friend actual state equation, and the second one is the interface heat flux that has been estimated by inverse heat conduction solution. They show strong dependency upon Ci in that the mass diffusion flux decreases dramatically with increasing Ci. Absorption process has been visualized by Mach-Zehnder interferometer and the obtained fringes have been analyzed to get the concentration distribution together with that obtained by theoretical solution in which ammonia concentration at the interface changes with time. The obtained optical images allowed us to distinguish between two layers with different speeds of fringes propagation. The layer with fast fringe propagation represents pure thermal diffusion where mass does not penetrate it, while the layer with slow fringe propagation is characterized with a superposition of heat and mass diffusion where heat has a large effect at short times from starting the absorption and this effect gets smaller with the elapse of time.

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Absorption chiller-heaters which can supply both chilled water and hot water at the same time, are used for cooling and heating air conditioning systems. In this paper, we classified absorption cold and hot water generating cycles and control methods, studied these absorption cycles by cycle simulation. In economizer cycle, condensed refrigerant which heats hot water is transported to cooling cycle and used effectively for cooling chilled water, Concerning with transported condensed refrigerant, there are two methods, all condensed refrigerant or required refrigerant for cooling are transported to cooling cycle, and required refrigerant method is better for energy saving. Adding improvement of solution control to this economizer cycle, simultaneous cold and hot water supplying chiller-heaters have good characteristics of energy saving in the all region.

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A two-phase closed thermosyphon is applied to gas-to-gas heat exchangers, the cooling of heat generation devices, the melting of snow, the prevention from icing of water on roads and so on. Generally, straight tubes are used as the thermosyphon. However, because of the limited space for the straight thermosyphon to be installed, it is considered that a bent thermosyphon is enforced to employ. In response to this, fundamental experiments are conducted on the heat transfer characteristics in a two-phase crank shape closed thermosyphon, in which an evaporator and a condenser are vertically positioned, and a connecting adiabatic section is horizontal. Ethylene glycol aqueous solutions which have lower freezing points and hydrofluoroether 7100 and 7200 which do not contain chloride are used as the working fluids Heat transfer coefficients and critical heat fluxes in the thermosyphon are measured by changing the amount of charged working fluid (0.30,0.40,0.50 and 0.60 of the evaporator volume),the temperature of the adiabatic section (40,50,60,70 and 80°C) and heat flux (from 4.0 kW /m² to critical). The experimental results are shown and compared with those taken using water as the working fluid.

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In order to develop Stirling cycle machines with high efficiency, suitable regenerator for each machine must be designed. To realize the flexibility of design and to improve the performance of regenerator, a new matrix, mesh sheet was proposed. It is a plate type with electrically etched holes. Each small hole is connected with neighboring holes by grooves on the plate. The performance test of cooling mode was carried out with a 3-kW Stirling engine in order to measure its cooling performance. Three types of the mesh sheet were developed and two of them were respectively stacked to install in the machine. Also, the pressure and regenerator losses were compared with conventional stacked wire gauzes and the mesh sheets. From the results, it was clarified that the performance of the cooling mode was improved about 5 to 40 % by the mesh sheet. In this paper, the relation between the dimensions of the mesh sheet, the pressure and regenerator losses were also clarified.

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Because of the destructions of ozone layers and global warming, it is urgently necessary to abolish fluorocarbon refrigerants of HFCs and substitute them with natural refrigerants. Among several choices of natural refrigerants, CO₂, which has an excellent thermal property, has the advantage for practical application. However, heat transfer coefficient and pressure drop of evaporator have not studied enough. No available correlation has been established. The refrigerant of CO₂ is extremely sensitive to oil. Therefore, the research on the refrigerant under the circumstances that it is mixed with oil is very limited. It is the purpose of this research to examine the oil mixing effects on thermal and fluid dynamic behaviors and establish correlation.

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