The pulse tube refrigerator is one of the regenerative cycle refrigerators such as Stirling cycle or Gifford-McMahon cycle which gives the cooling temperature below 150 K down to liquid helium temperature. In 1963, W. E. Gifford invented a simple refrigeration cycle which is composed of compressor, regenerator and simple tube named as pulse tube which gives a similar function of the expander in Stirling or Gifford-McMahon cycle. The thermodynamically performance of this pulse tube refrigerator is inferior to that of other regenerative cycles. In 1984, however, Mikulin and coworkers made a significant advance in pulse tube configuration called as orifice pulse tube. After this, several modifications of the pulse tube hot end configuration have been developed. With those modifications, the thermodynamic performance of the pulse tube refrigerator became the same order to that of Stirling and Gifford-McMahon refrigerator. This article reviews the brief history of the pulse tube refrigerator development in the view point of its thermodynamically efficiency. Simplified theories of the energy flow in the pulse tube have also been described.

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Ice nucleation-active bacteria act as nuclei and are able to freeze water without supercooling to a great degree. They are known as a major cause of the frost damage to crops. We have been trying with success to positively apply these bacteria to freeze texturing of food materials, freeze concentration of fresh liquid foods, formation of new physical properties of foods by freezing, and so forth. The most useful species for these applications is Xanthomonas campestris which has recently been designated as a food additive by the Japan Ministry of Health and Welfare and produced on an industrial scale. This paper reviews these topics, with some practical examples quoted primarily from our studies.

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The dynamics characteristics and refrigerant and lubricating oil in the high-pressure hermeti compressor has been studied. The compressor is 1 HP for the air conditioner of home use. The experiment and the analytic simulation have been researched.
As a result, the theoretic compressor model was proposed. This model has three processes inside of compressor. They are the suction process, the compression process, and the discharge process. In each process, mass equations and energy equations are considered. Also, the inlet refrigerant conditions (2-phase refrigerant) were simulated and the dynamic characteristics of refrigerant and refrigerant and lubricating oil at starting was obtaied.

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The evaporation heat transfer performance on six kinds of grooved surface with 0.15 mm to 0.34 mm of the groove pitch was obtained using a rectangular channel. The upper and lower surfaces inside a horizontal rectangular channel, 10 mm in width, 5 mm in height, and 500 mm in length, were heated electrically by Nichrome heaters. HCFC 22 was used as a working fluid. Evaporating pressure was 0.49 MPa, heat flux was 4.65 kW/m², vapor quality was varied from 0.1 to 0.9, and mass velocity was varied from 86 to 345 kg/(m²s). The empirical correlations to predict the heat transfer coefficients on upper and lower surfaces were proposed. The maximum heat transfer coefficient on upper surface is obtained on the grooved surface with 2 × 10^-8 of the modified bond number. Heat transfer coefficient on lower surface isn't influenced by the groove geometries except for lead angle.

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The evaporation heat heat transfer and pressure drop inside seven kinds of grooved horizontal tubes with 7.0 mm outside diameter and 60 to 100 grooves with 0.15 to 0.21 mm in height and 3 to 18 degree of lead angle, were obtained. The test section, 300 mm in length, was heated by condensing CFC 114 vapor on the outside of tube. HCFC 22 was used as a working fluid. Evaporating pressure was 0.49MPa, heat flux was 9.3 kW/ m², vapor quality was varied from 0.1 to 0.9, and mass velocity was varied from 86 to 345 kg/(m²s). The empirical correlations to predict heat transfer coefficient and pressure drop were proposed. Increasing the modified bond number, the heat transfer coefficient decreases in the range of the modified bond number experimented. Pressure drop isn't influenced by the groove geometries except for lead angle.

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The empirical correlation to predict the evaporation heat transfer coefficient inside an internally grooved horizontal tube was proposed using previous experimental data studied by other researchers. Parameters in the correlation were selected by refering to the correlation for rectangular channnel. The correlation for rectangular channnel was proposed by taking weighted average of heat transfer coefficients on upper and lower grooved surfaces inside a rectangular channnel to applicate to the internally grooved tube. Effects of parameters in the correlation for grooved tube are corresponding to those in the correlation for rectangular chaannel, and increasing the modified bond number, the heat transfer coefficient decreases. For rectangular channel, the maximum heat transfer coefficient is obtained on the grooved surface with 2 × 10^-3 of the modified bond number.

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This paper deals with flow and cold heat storage characteristics of the oil (tetradecane, C₁₄H₃₀, freezing point 278.9 K, Latent heat 229 kJ/kg)/water emulsion as a latent heat storage material having a low melting point. The test emulsion includes a water-urea solution as a continuum phase. The freezing point depression of the continuum phase permits enhancement of the heat transfer rate of the emulison, due to the large temperature difference between the latent heat storage material and water-urea solution. The velocity of emulsion flow and the inlet temperature of coolant in a coiled double tube heat exchanger are chosen as the experimental parameters. The pressure drop, the heat transfer coefficient of the emulsion in the coiled tube are measured in the temperture region over solid and liquid phase of the latent heat storage material. The finishing time of the cold heat storage is defined experimentally in the range of sensible and latent heat storage. It is clarified that the flow behavior of the emulsion as a non-Newtonian fluid has an important role in cold heat storage. The useful nondimentional correlation equations for the additional pressure loss coefficient, the heat transfer coefficient and the finishing time of the cold heat storage are derived in terms of Dean number and heat capacity ratio.

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Simulation on phase change from ice to water was presented using molecular dynamics method. 576molecules were placed in a cell at ice forming arrangement. The volume of the cell was fixed so that the density of ice was kept at 923 kg/m³. Periodic boundary condition was used. According to the phase diagram of water, melting point of ice at the density of 923 kg/m³ is about 400 K. In order to perform melting process from surface, only the molecules near the boundary were scaled at each time step to keep its average temperature at 420 K, and the average temperature of other molecules were set to 350 K as initial condition. By observing time variation of the change in molecular arrangement, it was found that the hydrogen bond network near the boundary surface started to break its configuration and the melting surface moved towards the center until no more ice forming configuration was observed. This phenomenon was also discussed in a form of temperature and energy variation. The total energy increased and reached to a steady state at the time around 6.5 ps. This increment was due to the energy supplied from the boundary at a constant temperature. The temperature in the cell kept almost constant at 380 K during the period between 0.6 and 5.5 ps. This period coincides with melting process observed in molecular arrangement. Hence, it can be said that 380 K corresponds to the melting point. The total energy stored in the cell consisted of sensible and latent heat. Specific heat of water and ice were calculated, and they were found to be 5.6 kJ/kg·K and 3.7 kJ/kg·K, respectively. Hence, latent heat was found to be 316kJ/kg. These values agreed quite well to the physical properties of water.

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NH₃-H₂O absorption refrigeration plant is attractive from each standpoint of electric power saving, non-fluorocarbon and energy saving.
The plant can be the economic alternative of power compression refrigeration for evaporation temperature range from 0°C to -60°C, using suitable waste heat (co-generation system, waste incinerator), oil and natural gas.
In the application of the plant, the equipment cost and the COP must be reasonable from economical standpoint. Therefore, the paper shows the following.
1) Necessary heating temparature analysis for absorption plant
2) Equipment cost analysis for heating temperature
3) Equipment cost analysis for COP
4) Number of trays in the rectifying column for COP
5) Equipment cost analysis and COP in two-stage absorption

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A two-phase loop thermosyphon transports thermal energy from a heat source to a heat sink by natural convective circulation under a body force field without any external power supply such as a pump. It is, therefore, thought that this could be applied to an energy-saving heat transportation system, and so forth. In practical use, an evaporator has several heated tubes and also the heat supplied to each of the heated tubes is not always equal. Therefore, the present study was performed both experimentally and theoretically on the flow and heat transfer characteristics in the two-phase loop thermosyphon installed with the evaporator with three heated tubes as a comparatively simple multi-tube evaporator in the lower part of the loop. The circulation mass flow rate, pressure and temperature distributions along the loop, as well as the heat transfer coefficients in the heated tubes were measured using water, ethanol and benzene, on which the effects of subcooling at the evaporator inlet and a heat input ratio of the three heated tubes were examined, and the experimental data were compared with the theoretically calculated results.

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The heat transfer performance of forced convective boiling was tested using a high temperature generator of absorption chiller/heater, the rear furnace wall of which was composed of two different surfaces; i. e., plain and sprayed heated surfaces. These two surfaces were bisymmetrically set. Wall surface temperatures of both the fire and fluid sides were measured at three locations along the upward flow direction in each heated surface for determining the heat flux and heat transfer coefficient. Nickel-chromium and alumina were employed as the spray materials.
The test results show that the sprayed surface can yield a marked elevation in the heat transfer performance due to boiling on the plain surface. Therefore the level of heated surface temperature is largely reduced by means of the spraying surface treatment. This implies that the spraying would much improve a corrosive condition of the heated surface.

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A two-phase loop thermosyphon is used as a heat transfer device in an energy-saving heat transportation system and so forth, because it transports thermal energy without any external power supply such as a pump under a body force field. We previously performed a fundamental study on the flow and heat transfer characteristics in a two-phase loop thermosyphon installed with a single heated tube evaporator both experimentally and theoretically which was made under the condition of near saturation temperature of liquid in a reservoir. In the present study, the effects of liquid subcooling and the heat input on the circulation mass flow rates, pressure and temperature distributions, and heat transfer coefficients in the evaporator were examined experimentally using water, ethanol, benzene and Freon 113 as the working fluids. On the other hand, the circulation mass flow rates, pressure and temperature distributions were theoretically calculated and compared with the experimental results.

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The absorption heat pump system has been developed to utilized treated sewage water from the view point of environmental protection and energy conservation.
The development has two step. Conventional LiBr solution is used at the first step, the new working fluid with higher solubility and lower viscosity is used to imprve the efficiency of absorption heat pump at the second step.
The first report says the search for the new working fluid and the performance of absorption heat pump concerned with the second step. LiBr, LiI, LiCl, LiNO₃, solution was selected as the new working fluid. The absorption heat pump using the new working fluid was tested and better results were obtained by comparision with LiBr solution.

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A wall cavity with two open slits at top and bottom is expected to regulate overheating of the exterior walls by solar irradiation. This study focuses on estimating the effect with the simulation in steady-state. For a cavity wall which has 3000 mm height, 50 mm thickness and 40% aperture ratio of openings, scores of calculations were excuted. With the condition of 200 W/ m 2 solar irradiation, 15°C temperature difference between interior and exterior and 5 m 2 K/W heat resistance value of the solid part wall, the excution results indicated that the increasing rate of heat resistance by cavity was 21%, more temperature difference provided less efficiency, and more solar irradiation generated more effeciency. To define the ability of the cavity, apparant thermal conductivity of the cavity was estimated. The thermal conductivity of cavity (0.022 W /mK) can be smaller than good insulation materials under the condition of large solar irradiation value (600W/m2). Results proved that the cavity wall had enough performance for reduction of cooling load.

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