Water is very useful and important in many industrial areas, as well as for human life. Hence it is necessary to investigate the behavior of water, both in macro scale and in micro scale. In a case of water near the melting temperature, potential energy due to hydrogen bonding becomes very important. For example, water has a density inversion at 4 degree C, ice is lighter than liquid water, and soon. Thus, in this report, recent studies on molecular dynamics method for water and ice behavior were introduced. There are various kinds of models for water and various methods to calculate. Each model and each calculating method behave differently from one another. Hence, selection of model and calculating method are very important to study the behavior of water. In order to obtain molecular behavior as close to the one in nature as possible, models for water and calculating methods are introduced, briefly.

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Natural gas is used as the energy source to cope with the recent situation of increasing demand for electricity especially in summer. In this paper, the performance of a Rankine cycle air conditioning system driven by natural gas was studied. The following results were obtained : (1) Basic equations of performance, refrigerant mass flow rate and expander volume were developed by using the values of heating efficiency, regeneration efficiency, expander efficiency and compressor efficiency. (2) R134a refrigerant has been considered to be suitable for the Rankine cycle air conditioning system, compared with other refrigerants. (3)A Rankine cycle cooling system using R134a refrigerant as a single working fluid was developed. System COP of 0.47 was attained at typical operating condition.

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Changes of capacitance and temperature of ethyl alcohol, hamburger and dough with cheese filling were measured with specially-made measuring devices during the freezing and thawing. The results of measurement of capacitance and temperature suggest a linear correlation for ethyl alcohol as a single constituent substance. The adequate correlation is too estimated from the results of food samples, though the capacitance of food sample varies greatly at the start and end of freezing and thawing process. It has been demonstrated that the quality or physical condition of food sample can be determined easily by the measurement of capacitance using the specially-made devices. Also the quality or physical condition of food can be determined easily by the non-contact and non-destructive measurements of capacitance.
A variety application of the present technique is conceivable for the process control of the freezing and thawing foods.

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An experimental study on the boiling heat transfer characteristics of liquid films flowing downward along vertically positioned plane and constant curvature surface (CCS) with isolated fine cavities was conducted. The effects of structural surfaces were examined, comparing with the case of smooth plane. The main results of these experiments are summarized as follows; (1) In the case of structual plane surface, there are remarkable enhancements of heat transfer rate in the nucleate boiling region. (2) In the case of CCS, it takes large values of heatflux in the region which strongly governed by the surface evaporation. (3)CCS avoids effectively the occurrence of splitting of the liquid film into rivulets. This study aims to put practical use of the heat transfer enhancement for the evaporator of a two-phase closed thermosiphon.

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The MH refrigeration systems are regarded as important and compact ones for solving energy and environmental issues. Our purposes are to develop the compact refrigeration system for the vending machine and the show case using MH, and to attain a refrigeration temperature of 243K by using a heat source of 403∼423K.
The kinetics of MH hydriding and dehydriding reactions is of importance relative to their practical use as a refrigerator system. The kinetics of the reaction between hydrogen and MH_High (Ti_0.18Zr_0.84Cr_1.0Fe_O.7Mn_0.3Cu_O.057)has been followed in this paper. A relatively rapid absorption of hydrogen takes place for values of relative composition to about 0.3∼0.4. It is evident that a hydrogen diffusion plays a minor role during this stage, as that part of the metal not covered by hydride is always in contact with hydrogen. The direct chemical reaction between the hydrogen and the exposed metal surface is therefore postulated as the rate-controlling process. The rate of the reaction then decreases, and for values of relative composition above about 0.8, the reaction becomes slow. After the metal particles have been completely covered by a hydride layer, the transport of materials through the layer by diffusion becomes rate controlling process

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Scroll expander for room air conditioning system was developed. The performance characteristics of scroll expander using R134a refrigerant were investigated experimentally. The following results were obtained. (1) Shaft power index N_exp was proposed newly and effective to evaluate the shaft power of scroll expander. (2) Shaft power index N_exp and expander efficiency η _exp increased with the increase in the pressure ratio in the range of the pressure ratio over 2.6. (3) Mass flow rate difference between measured and theoretical values decreased with the increase in the rotational speed and the decrease in the pressure ratio of expander. Mass flow rate ratio ξ of 0.98 to 0.9 were obtained at these operating conditions. (4) Maximum shaft power index N_exp of 0.8 and maximum expander efficiency η _exp of 0.74 were obtained at the pressure ratio of 3.7 and rotational speed of 50 (1/s).

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LiBr-H₂0 absorption chiller is widely used in Japan, and many research have been made for absorption characteristic in terms of enhancing heat transfer. Another study have been performed for widening working range with higher crystallization limits, and it was reported that adding LiI salt to LiBr-H₂0 working fluid provide about 5 [mass%] higher crystallization limit under the condition of absorption pressure range.
It is necessary to reveal absorption heat transfer performance to utilize this working fluid pair for absorption chiller. In this study absorption heat transfer characteristic was investigated for horizontal and vertical tube. As a result, it was found that heat transfer coefficient increased as mass flow rate of solution increased and mass concentration of solution decrease and that these characteristic were almost the same as LiBr solution, though this solution gave slightly less heat transfer coefficient than LiBr solution.

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This paper deals with ice melting characteristics of an ice thermal storage container filled up with harvest ice. The change in outlet water temperature and its stability over time are examined when the position of the inlet pipe in the ice thermal storage container, the time taken for the water in the container to be replaced once, and the method of spraying water into the container are changed. The following results were obtained for the harvest ice thermal storage container : (1) Outlet water temperature in the ice thermal storage container is influenced by the position of the inlet pipe; that is, when the water from the inlet pipe flows slowly through the ice packed bed, the lower outlet water temperature is able to be supplied to a heat exchanger for a longer time. (2) When water is sprayed from above the container, the outlet water temperature change against the nondimensional time is represented by one correlation curve even when the water replacing once in the container is changed, and the outlet temperature stays under 2°C up to a nondimensional time of about 0.8. (3) When water is sprayed from above the container, total heat release rate is also represented by one line. (4) Period of time during which the outlet temperature remains under 2°C is proportional to the time taken for the water in the container to be replaced once for three types of ice thermal storage in this experiment are used. (5) Heat transfer coefficient and modified Stanton number defined by volume flow rate are useful parameter for representation of ice melting characteristics.

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This paper proposes a procedure on the thermodynamically consistent determination of virial coefficients from speed-of-sound measurements. Using the speed-of-sound values for gaseous Difluoromethane (R-32) +Pentafluoroethane (R-125), R -32+ 1, 1, 1, 2 - tetrafluoroethane (R-134a), R125/134a and R-32/125/134a which have already been reported in the previous paper, the second virial coefficients of R-32/125, R -32/134a, R-125/134a and R-32/125/134a were determined by means of thermodynamic relation among the virial coefficients of two different virial equations of state with respect to pressure and density. The present virial equation of state regarding density expansion can represent not only the speed-of-sound values but also the PρT-data for R-32/125, R -32/134a, R -125/134a and R-32/125/134a. The deviation of the speed-of-sound data from the virial equation of state is about±100ppm.And the deviation of the PρT-measurements by Kleemiss and Tillner-Roth (1997) from the virial equation of state against density is about ±0.l%. The behavior of the second virial coefficient is shown at the available compositions.

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A water-fine particle suspension with a uniform initial temperature and concentration in a rectangular cell is heated from a center part of the horizontal bottom wall and cooled from the opposite vertical walls which are kept at the initial temperature. Such a transient natural convection is experimentally studied with various temperature differences between the hot and cold walls. Two kinds of particle with different distribution of particle size are used. During sedimentation of particles, the suspension forms layers. In each layer, concentration of particle, mean diameter of particles, and temperature are measured and time-dependent heat transfer coefficient on the hot wall is also measured. Effects of the temperature difference and the particle size distribution on the natural convection with particle sedimentation are clarified.

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