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Volume 9 (1992)
- Issue 3 Pages 203-
- Issue 2 Pages 101-
- Issue 1 Pages 1-
Volume 9, Issue 2
Displaying 1-9 of 9 articles from this issue
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Review Article
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Sadasuke Ito1992 Volume 9 Issue 2 Pages 101-116
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSIn this paper, the studies of heat pump systems using solar collectors as the evaporators, which have been done so far by reserchers, are reviwed.
Usually, a solar collector without any cover is preferable to one with ac over because of the necessity of absorbing heat from the ambient air when the intensity of the solar energy on the collector is not enough. The performance of the collector depends on its area and the intensity of the convective heat transfer on the surface. Fins are fixed on the backside of the collector-surface or on the tube in which the refrigerant flows in order to increase the convective heat transfer. For the purpose of using a heat pump efficiently throughout year, a compressor with variable capacity is applied. The solar assisted heat pump can be used for air conditioning at night during the summer. Only a few groups of people have studied cooling by using solar assisted heat pump systems. In Japan, a kind of system for hot water supply has been produced commercially in a company and a kind of system for air conditioning has been installed in buildings commercially by another company.View full abstractDownload PDF (883K)
Papers
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Hiromichi KAWABE, Teimi TANAKA, Shoichiro FUKUSAKO1992 Volume 9 Issue 2 Pages 117-126
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSAn experimental study has been performed to investigate the critical heat flux in a concentric-tube thermosyphon which has the straight shape of an inner tube. The outer tube was 27.4mm in diameter with 1080mm in height. Visual observations and measurments were carried out under the condition of uniform wall heat flux using R-11 and R-113 as the working liquid. The effects of inner tube diameter, insert length of inner tube into reservoir, and liquid subcooling on critical heat flux were extensively discussed. In addition, same experiments of single-tube thermosyphon were carried out for comparison. It was found that critical heat flux characteristics for concentric-tube thermosyphon were classified two regions. The correlation equations of both regions and transition condition were determined.View full abstractDownload PDF (558K) -
3rd Report : Theoretical Analysis Satisfied a Saturation Condition Between Temperature and Concentration of Water Vapor in the Case of Forced ConvecionIsao ISHIHARA1992 Volume 9 Issue 2 Pages 127-134
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSA set of boundary layer eqations - continuity, momentum, energy and diffusion equations - is solved numerically with satisfaction of a thermodynamic equilibrium between temperature and concentration of water vapor, when frost deposits on a flat plate under laminar forced convection.
The effects of frost surface temperature and ambient air condition - temperature and humidity - on the coefficients of heat and mass transfers are investigated. The relationships between Nusselt number and Reynolds number, and between Sherwood number and Reynolds number are maintained the similar tendency respectively whether the thermodynamic equilibrium is satisfied or not. When the eqlli1ibrillm is satisfied, the mass transfer coefficients are lower and the heat transfer coefficients are higher than ones without satisfaction of the equilibrium.View full abstractDownload PDF (328K) -
Cooling and Freezing Behaviors of Aqueous Sodium Chloride Solution in a Closed Rectangular Container1st Report, The Effect of Types of PartitionsAkira NARUMI, Takao KASHIWAGI, Ichirou NAKANE1992 Volume 9 Issue 2 Pages 135-146
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSThis paper investigates cooling and freezing behaviors of NaCl aqueous solution in a rectangular container equipped with horizontal partitions of micro porous film in order to determine the mechanisms of heat and mass transfer through cell wall for the purpose of freezing food. For comparison, experiments were performed using partitions of copper plate, no partition, and water. These processes were visualized and measured using real-time laser holographic interferometry.
It was found that there was very little difference in the cooling process due to partitions, but that there were significant differences in freezing process when NaCl aqueous solution is used.View full abstractDownload PDF (840K) -
Hiromu YASUDA, Kyuhei ISHIBANE, Susumu NAKAYAMA1992 Volume 9 Issue 2 Pages 147-156
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSAn evaporator superheat control system with an electrically driven expansion valve (EEV) is investigated theoretically and experimentally. Considerations between characteristic values and affecting factors of a refrigeration cycle gives a transfer function model of a prototype evaporator based on experimental results. The sampled-data PI algorism for EEV openings is employed to control the evaporator superheat.
The control system stability is analyzed and influence of the control parameters are studied. Control experimental results show that the proposed simulation model is confirmed effective to find proper control parameters.View full abstractDownload PDF (503K) -
Numerical Simulation and Flow Visualization under Isothermal ConditionMamoru OZAWA, Akira KAWAMOTO, Hisashi UMEKAWA, Isao ISHIHARA1992 Volume 9 Issue 2 Pages 157-168
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSNumerical simulation of air flow in a fin-tube type heat exchanger model has been conducted with particular reference to the flow pattern and flow distribution. The simulation model is two dimensional, and has three inlet ports and one exit port at the lower and upper boundaries, respectively. The flow field is partitioned into several sub-channels by spacers. The insertion of such spacers results in the reduction of recirculation zone, while the flow distribution in each sub-channel between the spacers mainly depends on the inflow rate through the inlet port just upstream the sub-channel. The flow visualization experiment has confirmed the simulation results.View full abstractDownload PDF (821K) -
Takashi CHIBA, Masashi OKADA, Koji MATSUMOTO1992 Volume 9 Issue 2 Pages 169-180
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSIn order to clarify the mechanism of heat transfer during melting of a clathrate in rectangular cells, two melting processes, namely, two-dimensional melting process with natural convection from a vertical wall and one-dimensional melting process by heat conduction from an upper horizontal wall, are studied experimentally.
The R-141b was used for generating clathrate. One experiment was carried out by melting the clathrate filled into a 150mm high and 100mm wide rectangular cell from a vertical wall. And in the other experiment, the clathrate was melted from the upper horizontal wall of a rectangular cell with 88mm height and 180mm width. The temperature distributions in cells were measured. The melting front was measured by pictures taken on fixed times. The concentration of freon in the melt was measured by gas-chromatography.
The following results are obtained.
(1) In the melting process, the clathrate decomposes into an emulsion region which is a water-freon mixture and a liquid freon region under the emulsion.
(2) Concentration gradient of freon in the emulsion plyas an important role in the natural convection in the melt. The Nusselt number on the heated vertical wall is depressed by the concentration gradients.View full abstractDownload PDF (4139K) -
1st Report : Apparatus and Preliminary Experiments for CFC-12, HCFC-22, and CFC-113Yukihiro HIGASHI, Masaaki OKADA1992 Volume 9 Issue 2 Pages 181-190
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSOn the basis of the differential capillary rise method and the vertical plate method, two kinds of experimental apparatus for measuring the surface tension of CFC alternatives have been constructed. In order to confirm the performance of these experimental apparatus, measurements of the surface tension for CFC-12, HCFC-22 and CFC-113 have been made in the range of temperatures between 273 and 343 K. The uncertainty of temperature measurement for the differential capillary rise method is estimated within ±20mK, whereas that for the vertical plate method is estimated within ±30mK. As the results of the comparisons between the present work and other investigations, the uncertainties of these measurements are estimated within ±0.1mN/m with the apparatus for the differential capillary rise method and within ±0.2mN/m with that for the vertical plate method.View full abstractDownload PDF (536K) -
2nd Report : Surface Tension for HCFC-123 and HFC-134aYukihiro HIGASHI, Tadamitsu IKEDA, Takeaki KUWANA, Masaaki OKADA1992 Volume 9 Issue 2 Pages 191-198
Published: 1992
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSMeasurements of the surface tension for two kinds of CFC alternatives, i.e., HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane), and HFC-134a (1,1,1,2-tetrafluoroethane), have been made by the differential capillary rise method (DCRM) and the vertical plate method (VPM). For HCFC-123, 15 data have been obtained by DCRM in the temperature range between 273 and 333 K within the uncertainty of ±0.1mN/m, and 21 data have been obtained by VPM in the temperature range between 273 and 290 K within the uncertainty of ±0.2mN/m. For HFC-134a, 17 data have been obtained by DCRM in the temperature range between 276 and 329 K within the uncertainty of ±0.1mN/m. The uncertainty of temperature measurement by DCRM is estimated within ±20mK, whereas that by VPM within ±30mK. New correlations of the surface tension for HCFC-123 and HFC-134a have been also proposed.View full abstractDownload PDF (380K)
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