Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers
Online ISSN : 2185-789X
Print ISSN : 1344-4905
ISSN-L : 1344-4905
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Volume 16, Issue 2
Displaying 1-10 of 10 articles from this issue
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Review Article
  • Recent Study on Ice Melting and Water Freezing using Molecular Dynamics Method
    2nd report : Molecular Simulation on Ice Melting or Water Solidifying
    Chaedong KANG, Seiji OKAWA
    1999 Volume 16 Issue 2 Pages 105-114
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.105
    JOURNAL FREE ACCESS
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    Many researchers have observed phase changing mechanism of ice to water or water to ice using molecular simulation, especially molecular dynamics (MD) method. In order to investigate the related lots of studies, we introduced molecular level information for water and MD method using phase changing methodologies through about 70 studies. Although the number of referenced papers may not be representative perfectly to understand the address of the MD research, their researches were divided into three categories, i.e., melting, solidification, and interface. Melting simulations has been performed actively with several water models, heating conditions, and ice structures. However, solidifying simulations were performed rarely, because mechanism of supercooling is difficult to model with quasistable state. Also, we arranged researches about molecular correlation of interface in which ice crystal growth was observed. Finally, Some new fields were introduced with upgraded computational environment.
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Papers
  • Experimental Analysis on Centrifugal Chillersunder Cycling Operation Mode
    Ting MU-MIN
    1999 Volume 16 Issue 2 Pages 115-121
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.115
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    Duty cycling of centrifugal chillers has been considered an effective method for demand side management. Full scale experiments were performed to identify that unloading was a necessary step so that excessive mechanical wear would not occur due to cycling operation. On the other hand, reciprocating and screw compressors can adapt to cycling operation successfully.
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  • Scroll Expander
    2nd Report : Internal Losses of Expander
    Shigemi NAGATOMO, Toshio OOTAKA, Akira MORISHIMA
    1999 Volume 16 Issue 2 Pages 123-132
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.123
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    Loss analysis of scroll expanders using R134a refrigerant was investigated and the following results were obtained. A loss estimating method of scroll expanders was proposed by using indicated power calculated by measured P-V diagram and another values. Leakage gas loss in suction process was large, so tip seals of scroll clearance are very important to realize high efficient scroll expanders. A new suction port system was designed and by this new type scroll expanders gas leakage decreased about 10% and expander efficiency increased about 10%.
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  • A Thermodynamic Property Model for R-125/143a Mixtures Based on a New Cubic Equation of State
    Heng-Liang ZHANG, Satoru TADA, Koichi WARANABE
    1999 Volume 16 Issue 2 Pages 133-139
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.133
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    The binary mixture of two hydrofluorocarbons, R-125 and R-143a, behaves almost like an azeotrope and has been considered as a promising refrigerant to substitute R-502. In this paper, we present a thermodynamic property model for the R-125/143a system, which was developed on the basis of a new cubic equation of state proposed in our previous publications. The essential thermodynamic properties such as PVTx properties, vapor-liquid equilibrium, enthalpy, entropy, isobaric specific heat, and speed of sound are well represented simultaneously by the new model in the entire fluid-phase of theR-125/143a system including the pure components.The model is valid for any composition with thermodynamic consistency to cover a range broad enough for refrigeration engineering applications. A pressure-enthalpy diagram for the R-125/143a mixture with 50 mass% R-125 is also presented.
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  • Experimental Study on the Effect of the Ultrasonic Wave on the Freezing of the Supercooled Water
    Tsutomu HOZUMI, Akio SAITO, Seiji OKAWA, Tatsuyuki MATSUI
    1999 Volume 16 Issue 2 Pages 141-146
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.141
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    In order to confirm the effect of ultrasonic wave on the freezing of supercooled water, various level of ultrasonic waves were applied to the supercooled water. The frequencies of the waves applied were 28kHz, 40kHz, 45kHz, 50kHz, and 1MHz. In order to clarify the mechanism of the effect of the ultrasonic wave, several factors were examined changing the experimental conditions and the results were compared each other; the factors were the existence of a free surface or oil -water interface, the volume of water, the purity of water and the existence of metal bar inserted. Each test section was cooled at a constant cooling rate and the ultrasonic waves were applied to each test section continuously, varying the frequency and the intensity. The experiments were carried out until the water in the test section solidified. The degree of supercooling at the freezing is determined by measuring the temperature just before a rapid increment of temperature due to freezing. It was found that the existence of a free surface and insertion of a metal bar with an addition to the ultrasonic wave have effects on the freezing of supercooled water. On the other hand, if oil-water interface or no metal bar insertion was selected as the experimental condition, there was no influence of the ultrasonic wave on the freezing of the supercooled water even the frequency and the intensity were varied.
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  • Study on the Mechanism of the Freezing of the Supercooled Water under the Effect of the Ultrasonic Wave
    Tsutomu HOZUMI, Akio SAITO, Seiji OKAWA
    1999 Volume 16 Issue 2 Pages 147-156
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.147
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    In the previous paper, it was found that the ultrasonic wave has an effect on the freezing of supercooled water under the conditions of the existence of a free surface and insertion of a metal bar. On the other hand, if oil-water interface or no metal bar insertion was selected as experimental condition, there was no influence of the ultrasonic wave on the freezing of the supercooled water even the frequency and the power of the wave were varied. In order to clarify the mechanism of the effect of the ultrasonic wave on the freezing of the supercooled water, authors tried the several experiments. Through the available considerations, it is found that during the application of the ultrasonic wave, the supercooled fog and/or the fine supercooled water drops are produced from the free surface of the supercooled water by the capillary wave and the surface tension wave. It is possible that the high speed supercooled drops clash with the metal bar and/or the floating drops, inducing the freezing of the Supercooled water.
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  • Evaluation of Refrigerating and Air Conditioning Devices in Energy Cascade Systems under the Restriction of Carbon Dioxide Emissions
    Yoichi SHIMAZAKI, Atsushi AKISAWA, Takao KASHIWAGI
    1999 Volume 16 Issue 2 Pages 157-166
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.157
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    It is necessary to introduce energy cascade systems into the industrial sector in Japan to reduce carbon dioxide emissions. The aim of this study is to evaluate the refrigerating and air conditioning devices in cases of introducing both energy cascade systems and thermal recycling systems in industries located around urban areas. The authors have developed an energy cascade model based on linear programming so as to minimize the total system costs with carbon taxes. Five cases are investigated. Limitation of carbon dioxide emissions results in the enhancement of heat cascading, where high temperature heat is supplied for process heating while low temperature one is shifted to refrigeration. It was found that increasing the amount of garbage combustor waste heat can reduce electric power for the turbo refrigerator by promoting waste heat driven ammonia absorption refrigerator.
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  • Fundamental Study on Enhancement of Liquid-Liquid Direct Contact Heat Transfer of Descending Water Insoluble High Density Liquid Droplets in a Heat Source Water Layer by Using Wire Mesh as Dispersion Material
    Hideo INABA, Akihiko HORIBE, Naoki YOKOYAMA, Naoto HARUKI
    1999 Volume 16 Issue 2 Pages 167-176
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.167
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    This paper has dealt with liquid-liquid direct contact heat transfer characteristics by means of water insoluble heat transfer medium. In the present study, Perfluorocarbon(PFC, density of 1830kg/m3)was injected from above into a hot water layer, which was mounted by stainless steel wire net in order to make PFC droplets finer. The measuring result of the drop let diameter revealed that the droplet size distribution exerted an influence on the temperature effectiveness between PFC droplets and the hot water layer. It was observed that PFC droplets were dispersed by collision with stainless steel wire nets during falling in the hot water layer. Finally correlations equations of the temperature effectiveness and average diameter of PFC droplets had been derived as a function of some parameters.
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  • Reform of the Correlation for the Prediction of Heat Transfer Coefficient for Refrigerants Flowing in Horizontal Evaporator Tubes
    Hideo MORI, Suguru YOSHIDA, Yasushi KAKIMOTO, Katsumi OHISHI
    1999 Volume 16 Issue 2 Pages 177-187
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.177
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    The authors had previously proposed a prediction method of the local heat transfer coefficient for pure refrigerants flowing in horizontal smooth evaporator tubes. This method was compared with new experimental data, and found not to be accurately applicable to refrigerants of a large vapor density and/or flow in a tube of small diameter, particularly in the separated flow regime1nthis prediction method, the separation angle is a primary factor, and correlation of this angle is used not only to classify the flow regime into the annular flow and the separated flow, but also to determine the ratio of the wet perimeter to the whole perimeter f the tube for the separated flow. Based on the new experimental data of the separation angle obtained for refrigerants of a large vapor density and in a small diameter tube, the correlation for the separation angle was reformed so that the predicted heat transfer coefficient agrees well also with the new experimental values.
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  • Using a Cross -grooved Inner Surface for Enhancement of Heat Transfer Characteristics Inside Horizontal Tubes for Zeotropic Refrigerant
    First Report : Condensation Test
    Mari UCHIDA, Masaaki ITOH, Naoki SIKAZONO, Toshio HATADA, Mitsuo KUDOH ...
    1999 Volume 16 Issue 2 Pages 189-194
    Published: 1999
    Released on J-STAGE: October 11, 2011
    DOIhttps://doi.org/10.11322/tjsrae.16.189
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    The condensation characteristics of zeotropic refrigerant(R407C) inside horizontal tubes has been investigated experimentally using two types of new cross -grooved tube which are formed by varying the helix angle of second set of grooves at the same fin height. The performance of the two types of cross-grooved surface are compared to that of single -grooved surface. The improved cross-grooved tube(second helix angle β2=0°) has provided with higher condensation heat transfer coefficients than the single grooved tube at a low mass flow velocity. However, at a high mass flow velocity, the difference between condensation heat transfer coefficients for single and cross -grooved tube is not evident. The pressure drop of improved cross-grooved tube is slightly higher than that of the single grooved tube.
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