Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers
Online ISSN : 2185-789X
Print ISSN : 1344-4905
ISSN-L : 1344-4905
Volume 36, Issue 4
Displaying 1-15 of 15 articles from this issue
Original papers
  • Wataru IWATAKE, Raito KAWAMURA, Shin SEKIYA, Kei SASAKI, Yuji TAKAMURA
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 181-
    Published: 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    In order to suppress the discharge temperature rise of the scroll compressor at the high compression ratio operation in air conditioning systems, it is necessary to apply the injection for cooling gas refrigerant with liquid or two-phase refrigerant. However, the conventional injection has two problems, the ineffective compression loss due to the dead volume and the pressure pulsation at the injection pipe caused by the pressure propagation from the compression chamber. To solve these problems, we developed the new type of injection “Suction chamber injection” cooling the gas refrigerant before compression. In this paper, we report the features of suction chamber injection and the evaluation results of the prototype. The results are as follows: (1) Discharge temperature can be reduced without diluting oil. (2) The pressure pulsation in the injection pipe can be reduced by 77% compared to the compression chamber injection. (3) Compression efficiency is higher than compression chamber injection by suppressing the ineffective compression loss.

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  • Takashi MATSUMOTO, Yohei ARATA, Kai KUTSUNOYA, Kazushi MIYATA, Yoshin ...
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 189-
    Published: December 30, 2019
    Released on J-STAGE: December 31, 2020
    Advance online publication: November 15, 2019
    JOURNAL FREE ACCESS

    In this study, to clarify the fundamental characteristics of condensation heat transfer of refrigerant in a horizontal rectangular mini-channel at low mass fluxes down to 40 kg/(m2ꞏs), experiments were performed using a single rectangular small tube with a hydraulic diameter of 1.02 mm. HFC134a, HFC32 and HFO1234ze(E) are used as test refrigerants. The range of refrigerant mass flux condition was 40-400 kg/(m2ꞏs), and that of heat flux was 2-8 kW/m2. From the present data, it was clarified that the condensation heat transfer coefficient at a low mass flux 100 kg/(m2ꞏs) or less was noticeably high value compared with that at relatively high mass flux conditions. Besides, this tendency was different from that was seen in experimental studies using multiport tubes and tendency predicted by existing correlations applied by extension to the low mass flux condition.

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Translated paper
  • -1st Report: Analysis Modeling and Theory Construction-
    Tatsuya SASAKI, Yoshimi IKEDA, Fumihiko ISHIZONO, Katsunori SATO, Shin ...
    Article type: Translated Paper
    2019 Volume 36 Issue 4 Pages 199-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    There is a growing need to expand the upper limit of the operating range of compressors for air-conditioning and refrigeration systems. There are two design approaches to expand the upper limit. One is expansion of the stroke volume, but this increases the load of the sliding bearing as the compressive load of the refrigerant. The other is increasing maximum rotation speed, which increases the shear heat of the oil film; viscosity of the oil then decreases, and the load capacity of the sliding bearing decreases. Incidentally, the refrigerant is dissolved in the oil that lubricates the journal bearing, and the solubility and the dissolving viscosity change depending on the temperature and pressure conditions. The viscosity change of oil due to friction heat and refrigerant dissolving at high rotation speed and high load range cannot be ignored. So, we constructed a thermal elastrohydrodynamic lubrication analysis model that captures changes in viscosity due to oil film temperature and solubility, and clarified the influence of frictional heat generation, solubility and viscosity change on journal bearing characteristics.

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Original papers
  • Ryunosuke MAEKAWA, Yuto NAKAJIMA, Lochan Rajib POUDYAL, Toru SUZUKI, M ...
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 211-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    Recently, it is often heard that the quality of fishery produces has been improved by using ice slurry for cooling, but there are few examples of scientific verification on the advantage of ice slurry. In this article, we measured the heat transfer coefficient by using metal balls under the condition that are considered to be used in cooling and thawing of fishery produces. As a result, ice slurry enabled very large heat transfer coefficient for the first 5 seconds both in cooling and thawing, but after 10 seconds it was about the value of ordinary forced convection of the liquid. On the other hand, when the ice slurry was forced to flow, the extremely high heat transfer was maintained even after 10 seconds in cooing, but in thawing condition, there was a little heat transfer enhancement after 10 seconds. Consequently, basic heat transfer characteristics during cooling and thawing by using ice slurry was revealed, including the effect of fluidizing.

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  • -Effect of the Thickness of Membrane, Location and its Orientation of Pore Processed to a Sheet of Membrane on the Performance of the Device -
    Seiji OKAWA, Sho MURATA, Takayuki HACHIYA, Tsutomu HOZUMI
    Article type: original paper
    2019 Volume 36 Issue 4 Pages 223-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    As one of supercooling cancellation devices for refrigerant PCM, authors have proposed a capsule type of the device which have an elasticized membrane with a pore at one side and water is enclosed inside. Water in the capsule solidifies first because the melting point is higher than that of the refrigerant PCM. When a membrane expands by solidification, a pore opens, and the ice in the capsule is exposed to PCM. When PCM is in a supercooling state, the exposure becomes an ice nucleus, and solidification propagates. However, the concentration in the capsule rises when the exposure is too big. In this study, the influence of the difference in thickness of the membrane and the location and the orientation of the pore on the membrane on the performance of suppressing the supercooling of PCM was examined.

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  • -Adsorption Properties of Ethanol Solution by Silica Gel-
    [in Japanese], [in Japanese], [in Japanese]
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 235-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    We propose adsorption ice slurry generator to utilize low-temperature waste heat. Ethanol solution is used as a refrigerant of the adsorption cycle, and ice slurry is produced in the evaporator of the cycle. The adsorption ice slurry generator will expand the use of low-temperature waste heat, because we can transport cooling heat to a long distance by transporting ice slurry. In this study, we investigated the adsorption properties of silica gel against ethanol solution. Based on the results, we estimate the theoretical efficiency of the adsorption cycle using ethanol solution as refrigerant. It was concluded that ethanol solution is suitable for the refrigerant of the cycle because the estimated COP and exergy efficiency of the cycle using ethanol solution is higher than that using water or ethanol. It was confirmed that the adsorption cycle using 10 mass% ethanol solution is suitable for ice slurry production, because exergy efficiency is almost same even when the evaporation temperature decreases to freezing temperature of 10 mass% ethanol solution.

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  • Shigeki HIRANO, Tsuyoshi KAWANAMI
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 247-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    Heat supply technologies such as a solar heat utilization or a low exergy waste heat are receiving attention as an alternative heat source to fossil fuels. For the effective utilization of such energy resources, development of a latent heat storage system is expected. The purpose of this study is to represent an unsteady melting phenomenon in a latent heat storage tank and to establish an effective numerical analysis for evaluating the thermal characteristics in the heat storage tank. A numerical analysis was conducted on the effects of the arrangement of phase change materials in the heat storage tank and the flow conditions of the heat exchange medium on the heat transfer behavior. An algorithm based on MPS (Moving Particle Semi-implicit) method, which is a kind of particle method, was adopted for the building the numerical analysis model. As a result of this study, melting analysis model based on the MPS method, consistently calculated the melting behavior in the heat storage tank, and it is also found that the influence of the flow rate condition of the ambient fluid is small on the melting behavior of the phase change material.

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  • Toshie KOYAMA, Fubito WAJIMA, Takeya YOSHIOKA, Hiroshi NAGAISHI, Takaa ...
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 261-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    Advance online publication: November 15, 2019
    JOURNAL FREE ACCESS

    Dehydrated ice slurry produced from sea water is effective in maintaining freshness of marine products, and are therefore expected to be utilized as cooling media during long-distance transport of marine products. Because the temperature history of dehydrated ice slurry during melting strongly depends on the initial water content, detailed knowledge of the water content of dehydrated ice slurry is required. In this study, ice slurry produced from NaCl aqueous solution was dehydrated by gravity, and the water content in the dehydrated ice slurry was measured. The results showed that the water content decreases with increasing the diameter of ice particles and has a unique distribution in the vertical direction. We compared the present results with existing data of water permeation in snow, and then found that dehydration of ice slurry can be elucidated based on the physical model of water permeation in snow, despite the difference in the diameter of ice particles and type of liquid phase between ice slurry and snow.

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  • Koji MATSUMOTO, Kohei EHARA, Kazuomi MAEZAWA, Kakeru SATO, Yuri UMEHAR ...
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 271-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    It is well known ice adhesion force to a metal surface is so strong. Thus, most of studies have been done for suppression of the ice adhesion force. In this paper, contrary to conventional studies, to effectively use the strong ice adhesion force to the metal surface the authors group noticed “freezing chuck“ for strong fixation of a workpiece to a work table. And to realize more strong ice adhesion force use of an anionic surfactant-pure water mixture was investigated. In this paper, a shearing stress defined by (ice adhesion force)/(ice adhesion area) was used to estimate the ice adhesion force. A voltage was applied to a copper surface consisting of DC condenser, after which shearing stresses were measured, varying magnitudes and polarities of the applied voltage. Simultaneously, adsorbed amounts of surfactant molecules to the Ni surface and surface energies of ice with surfactant molecules were measured, varying applied voltages and those polarities. And from the results of the adsorbed amount and the ice surface energy with surfactant molecules, validity of the measured shearing stresses was verified.

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  • Hidetoshi OHKUBO, Toshiki HIROTANI, Takayuki MOROKUMA, Haruka AGUI
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 283-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    Advance online publication: November 30, 2019
    JOURNAL FREE ACCESS

    In this study, we investigated the influence of thermal conductance of a boiling surface on the pool boiling heat transfer to saturated liquid nitrogen at atmospheric pressure. A cooled sample was a copper sphere, 25 mm in diameter. The thermal conductance of the copper surface was changed by the ice layer and the frost layer coated on it. The experimental results show that the effects of ice layers on the copper surfaces on cooling curves and boiling heat transfer characteristics are remarkable. When a frost layer is used as a thermal insulation layer on the cooling surface, the heat flux in the transition boiling region increased markedly and both the critical heat flux and heat flux in the nucleate boiling region increased.

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  • -Construction of acoustic phase diagram-
    Hideaki YOSHIOKA, Tomoaki KYODEN, Tadashi HACHIGA
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 291-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    Correlation between ultrasonic behavior and solidification process of aqueous solution is studied with the aim to develop an ultrasonic technique for detecting various state quantities in the field of thermal-hydraulics with phase change. First, a simple ultrasonic measurement system was constructed, and then the solidification experiments were conducted by varying temperature and initial concentration of sodium chloride solution from 0 wt.% to almost eutectic composition, 23 wt.%. From the experiment, it was found that sound velocity was changed by ice crystal growth and/or salt-ice eutectic reaction. Next, the variation of sound velocity at each initial concentration was discussed in relation to the solidification process, on a temperature-sound velocity coordinate plane. Summarizing these results, we presented a novel three-dimensional acoustic phase diagram, in which information of sound velocity was added to temperature and composition as intensive variables. Thus sound velocities in each region of a liquid region, a mush region, and a solid region were characterized on the acoustic phase diagram. Finally, it was clarified that, based on the acoustic phase diagram, our noninvasive sound velocity measurement is able to detect various state quantities such as temperature, composition, and ice packing factor.

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  • Makoto KATO, Takashi MORIMOTO, Hiroyuki KUMANO
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 303-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    When the ice slurry is transported by pipe, blockage in the pipe may occur depending on the flow conditions and the surrounding environment. One of the causes is freezing of ice slurry in the pipe caused by chilled from outside, but the mechanism has not been fully elucidated. In this study, ice slurry generated from ethanol aqueous solution was flowed into a rectangular channel and cooled from upper and lower side of the channel to observe the freezing behavior of ice slurry. IPF, Reynolds number and temperature difference between ice slurry and brine were chosen as the experimental parameters. As a result of comparison with the Stefan solution, which is an exact solution to the freezing problem, the thickness of the frozen layer tends to be slightly higher than the Stefan solution. Furthermore, when ice particles are contained or Reynolds number is low, the growth rate of the frozen layer at upper side of the rectangular channel was found to be slightly faster than other conditions.

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  • Takashi MORIMOTO, Toshiki IKEDA, Yuto TANAKA, Hiroyuki KUMANO
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 315-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    In this study, flow and heat transfer characteristics of emulsion type thermal storage material which a phase change material is emulsified and dispersed inside a water in a microchannel was investigated experimentally and numerically. It was found that mass fraction and state of dispersoild affected the rheology characteristics of emulsions and they tended to show pseudoplastic fluid behavior. Furthermore, the Nusselt number of emulsions reasonably agreed with that of single phase fluid when its dispersoid keep solid or liquid phase during heating, and was higher than the value when its dispersoid is melting because the apparent specific heat increased due to latent heat absorption of phase change materials. It was expected that an effect of existence of dispersoid on flow and heat transfer of emulsions in the microchannel because the relative size of dispersoid relative to flow path is comparatively large. However, obvious effects of dispersoid on flow and heat transfer of emulsions in the microchannel were not observed.

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  • -Effect of Flow Pattern and Solid Fraction on Heat Transfer coefficient-
    Hiroshi MIZUMOTO, Shunsuke ABE, Hiroyuki INAGAKI, Tatsunori ASAOKA
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 327-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    We propose erythritol slurry, which is the mixture of erythritol solution and erythritol crystal, as a slurry heat medium for medium-low temperature (200 °C or less) such as industrial exhaust heat and solar heat. The purpose of this study is to understand the heat transfer characteristics of erythritol slurry. In the experiment, erythritol slurry was flowed through a stainless steel tube heated with a uniform heat flux, and the local heat transfer coefficient was measured with changing the solid fraction and Reynolds number as parameters. The local heat transfer coefficient of a cross section of the tube was investigated. In laminar flow, the local heat transfer coefficient at the side of the tube and that at the bottom of the tube are higher than the theoretical values of single phase flow. In turbulent flow, the difference of heat transfer coefficient between experimental values and theoretical values of single phase flow is small. It means the influence of the solid fraction on the heat transfer coefficient is small in the turbulent flow. From the results, it was confirmed that the influence of the solid fraction and the flow pattern on the local heat transfer coefficient in the laminar flow is large. We suggested that the flow pattern should be considered in design of the system using the erythritol slurry.

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  • -Influence of Flow Pattern and Solid Fraction on Flow Characteristics-
    Kenta INATSU, Shunsuke ABE, Tatsunori ASAOKA
    Article type: Original paper
    2019 Volume 36 Issue 4 Pages 339-
    Published: December 31, 2019
    Released on J-STAGE: December 31, 2020
    JOURNAL FREE ACCESS

    We proposed erythritol slurry, which is mixture of the erythritol solution and erythritol crystal, as a heat medium for the utilization of unused heat at medium/low temperature. The influence of flow pattern and solid fraction on the flow characteristics were investigated experimentally. In the experiment, erythritol slurry was flowed through a horizontal stainless steel tube and the pressure drop was measured. Although a power-law equation was used to describe the flow characteristics of the slurry, the cause of the difference between the pipe friction coefficient and the theoretical value cannot be clarified. Also, a new model, the sedimentary layer of the solid crystals considered, was applied in the laminar flow. As a result, the difference between the pipe friction coefficient and the theoretical value became smaller. It suggested that the influence of the flow pattern on the flow characteristics of the slurry is not negligible, and it was found that the evaluation of the flow characteristics using a model, the sedimentary layer considered, was effective.

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