Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers
Online ISSN : 2185-789X
Print ISSN : 1344-4905
ISSN-L : 1344-4905
Volume 7, Issue 2
Displaying 1-9 of 9 articles from this issue
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  • Hiroshi IWATA, Mitsuru NAKAMURA, Osami MATSUSITA, Masatsune SUTOU
    1990 Volume 7 Issue 2 Pages 105-118
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    New technology for improving comfort in air-conditioning has been developed recently. One of the most important technologies for comfort improvement in air-conditioners is to reduce the noise.
    So, many studies to reduce the noise in air-conditioners have been carried out for several years. The technology to reduce the noise in air-conditioners depends on not only arrengement of unit components and development of noise reduction thchnology for fans but also advances in the field of vibration and noise reduction thchnology of compressors.
    Therefore, we review the vibration and noise reduction thchnology with respect to small capacity positive displacement type compressors for room air-conditioners and packaged air-conditioners. And, we mention some recent technologies to the vibration and noise reduction.
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  • Takashi MATSUZAKA
    1990 Volume 7 Issue 2 Pages 119-130
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    Various kinds of sensor are used for control of air-conditioning equipments. In this paper, examples of control system using some kinks of sensor about improvement of amenity are introduced.
    Humidity control methods using ceramic humidity sonsor, temperature-radiation-air flow control methods using amenity sensor, zone control methods using human detecting sensor and IAQ control methods using gas sensor, are discussed.
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Paper
  • Effects of Parameters on Solidification Process
    Yoshio HIRASAWA, Akio SAITO, Isao TOMIZUKA, Eisyun TAKEGOSHI
    1990 Volume 7 Issue 2 Pages 131-138
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    The solidification process of a heterogeneous composite material which consists of coiled conductive solids and water is experimentally examined along with the numerical calculation by the model proposed by the authors. Several parameters such as the volume ratio of the conductive solids (Vd), the outer diameter (Dc) of the coil and the wire diameter(D) are varied in the study.
    Consequently, it was found that the solidification rate was promoted by increasing Vd, and in the case of constant Vd the rate became larger with increasing Dc and with decreasing D. It was also found through the numerical calculation that the solidification rate was considerably promoted by adding a little amount of conductive solids when the thermal conductivity ratio (k) of the conductive solid to the phase-change material was higher than 50. Comparing the experimental and the numerical results, the relation between the solidification rate and the above parameters showed a similar qualitative trend each other.
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  • Numerical Analysis by One-dimentional Difference Method
    Akira MATSUDA, Teruo KAWAMURA, Kunihiko HADA
    1990 Volume 7 Issue 2 Pages 139-150
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    Experiments on evaporation for lithium bromide aqueous solutions (0-55wt% LiBr) were made in a vertical falling film type of stainless steel generator under reduced pressure, 8kPa. A simple calculation method is proposed to analyze the heat and mass transfer in falling film of lithium bromide aqueous solutions. The method is to solve the one-dimensional differance equation driven using the previous equations for coefficients of heat transfer and mass transfer in falling film, and the unidirectional diffusion model.
    The results of the new calculation method agree with those of author's previous two-dimentional difference method, and the new method reduces computation time to one sixtyth. The calculated values for evaporation rate and falling film temperatures in the generator agree well with the observed values of them.
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  • Akira MATSUDA, Kunihiko HADA, Teruo KAWAMURA
    1990 Volume 7 Issue 2 Pages 151-160
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    Experiments on evaporation and absorption for lithium bromide aqueous solutions(0-60wt%LiBr) were made in a vertical falling film type of stainless steal columm under reduced pressure, 8.0kPa. The changes of concentration and temperature in the falling film columm and the rates of absorption and evaporation were equivalent in the absorber and generator. They agreed well with the values calculated by the one-dimentional difference method using heat transfer coefficient, mass transfer coeficient and the unidirectional diffusion model. Therefore, it is guessed that a falling film type of absorber and generator may be designed by the same method. Considering the relation between heat flux and degree of superheat at heat transfer surface, and the mixing condition of lithium bromide aqueous solution in a generator, it is found that a falling film type generator is superior to a pool boiling type for a generator in absorption-type refrigerator and heat pump driven by low temperature heat source.
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  • Shoichiro FUKUSAKO, Masahiko YAMADA, Hisashi MORIZANE
    1990 Volume 7 Issue 2 Pages 161-170
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    An experimental study has been performed to investigate the effect of a number of parameters on the characteristics of the frozen layer of solution which formed on the vertical cooled plate being immersed in the forced convection flow. A transparent lucite channel, which has a cross sectional area of 50 mm x 70 mm, and has a length of 500 mm, was utilized for the test section. One side of the test section was made of copper plate as a cooled surface. Ethylene-glycol solution was adopted as a testing liquid. Measurements and visual observations were extensively carried out under a variety of initial concentration, initial temperature, flow velocity of solution, and cooling temperature as parameters. It was found that the characteristics of the frozen layer at the onset and steady state were well classified by both Reynolds Number and the cooling temperature ratio. The correlation equation of the averaged frozen layer thickness was determined.
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  • Masao SHIIBAYASHI, Yasushi IZUNAGA, Shintaro SADO
    1990 Volume 7 Issue 2 Pages 171-180
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    In recent years there arises growing demand of helium liquefaction refrigerators for the magnetic resonance imaging systems, magnetically levitated vehicles and other systems using superconducting magnet. From this background, a small size, scroll type of hermetic helium compressor capable of compressing helium gas to the pressure ratio of 20 in a single stage is developed. Main features of this compressor are as follows.
    1) Discharge capacity can be varied from 7 to 20 Nm3/h by changing driving motor frequency from 30 to 80 Hz.
    2) The overall adiabatic efficiency showed 72%∼79% under the pressure ratio range of 11∼20 at 60 Hz using oil injection cooling device.
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  • Experimental Discussion on Melting Process
    Yoshio HIRASAWA, Eisyun TAKEGOSHI, Eiji TAKESHITA, Akio SAITO
    1990 Volume 7 Issue 2 Pages 181-188
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    Authors have studied the solidification process of heterogeneous composite materials which consist of coiled conductive solid and water.
    The present study examined experimentally the melting process of these heterogeneous composite materials. Experiments were performed varying factors such as the volume ratio of conductive solid (Vd), the outer diameter (Dc) and wire diameter (D). As simple examples of these composite materials, lattice and right-angled coils were employed for measuring the temperature distribution of the materials and for observing the flow pattern.
    As a result, the melting process was increased considerably with increasing Vd, and in the case of constant Vd the melting rate was promoted by increasing Dc and by decreasing D. It was observed that the natural convection based on the density inversion of the water was reduced by the lattice and right-angled coils.
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  • Masato FUKUSHIMA, Naohiro WATANABE, Toru KAMIMURA
    1990 Volume 7 Issue 2 Pages 189-200
    Published: 1990
    Released on J-STAGE: October 11, 2011
    JOURNAL FREE ACCESS
    The critical parameters and vapor-liquid coexistence curves in the critical region of two environmentally acceptable hydrogen-containing halocarbons (HCFC123 and HFC134a) were determined experimentally. The measurements of vapor-liquid coexistence curves were made through visual observation of the disappearance of meniscus at the vapor-liquid interface within the optical cell. Thirty eight saturated densities in the range of 209 to 1176 kg/m3 were obtained between the temperature of 392 K and the critical temperature for HCFC123. And seventeen saturated densities in the range of 322 to 746 kg/m3 were obtained between the temperature of 370 K and the critical temperature for HFC134a. On the basis of these results, the critical temperature and critical density of HCFC123 were determined to be 456.94 K and 553 kg/m3, respectively. And these parameters of HFC134a were determined to be 374.18 K and 507 kg/m3. In addition, the critical exponents were determined and the correlation of vapor-liquid coexistence curves were developed.
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