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Volume 18 (2001)
- Issue 4 Pages 365-
- Issue 3 Pages 203-
- Issue 2 Pages 105-
- Issue 1 Pages 1-
Volume 18, Issue 1
Displaying 1-10 of 10 articles from this issue
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Review Article
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Bidyut Baran SAHA, K.C.Amanul ALAM, Yoshinori HAMAMOTO, Atsushi AKISAW ...2001 Volume 18 Issue 1 Pages 1-14
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSOver the past few decades there have been considerable efforts to use adsorption (solid/vapor) for cooling and heat pump applications, but intensified efforts were initiated only since the imposition of international restrictions on the production and use of CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons). Up to now, only the desiccant evaporative cooling system of the open type has achieved commercial use, predominantly in the United States. Closed-type adsorption refrigeration and heat pump systems are rarely seen in the market, or are still in the laboratory testing stage. Promising recent development have been made in Japan for the use of porous metal hydrides and composite adsorbents. In this paper, a short description of adsorption theories along with an overview of present status and future development trends of thermally powered adsorption refrigeration cycles are outlined putting emphasis on experimental achievements. This paper also addressed some advanced absorption cycles having relatively higher COP, and also summarizes fundamental concepts of GAX cycles and various GAX cycles developed for heat pump applications.View full abstractDownload PDF (743K)
Papers
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Yooko TSUCHIYA, Hiromi HASAGAWA, Tetsushiro IWATSUBO2001 Volume 18 Issue 1 Pages 15-20
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSAs regards the super cooling phenomena which is important matter in encapsulated ice system, the system efficient suffering from the super cooling release of water was estimated and the performance of release reagent was determined. The following conclusions were reached.
(1) It was clear that the COP of heat storing of the system fell by 3% with decreasing release temperature by 1 degree centigrade.
(2) As a result of determinations about release reagents, Xanthomonas campestris (ice nuclei bacteria) was very effective in release the super cooling state, and the performance was maintained in continuous application of freezing and melting.View full abstractDownload PDF (376K) -
Sigeo AOYAMA, Hideo INABA2001 Volume 18 Issue 1 Pages 21-30
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSThis paper has dealt with the direct contact heat exchange characteristics between ice particles (average ice particle diameter : 3.10mm) packed in the rectangular cold energy storage vessel and flowing hot air as a heat transfer medium. The hot air bubbles ascended in the fluidized ice particles layer, and they were cooled down directly by melting ice particles. The temperature efficiency increased as Reynolds number Re increased because the hot air flowing in the layer became active. The dehumidity efficiency increased with an increase in modified Stefan number and Re, since the heat capacity of inlet air and heat transfer coefficient increased. Finally, some empirical correlations for temperature efficiency, dehumidity efficiency and the completion time of cold energy release were derived in terms of various nondimensional parameters.View full abstractDownload PDF (724K) -
Tetsuo HIRATA, Masaaki ISHIKAWA, Nobuaki AKUTSU2001 Volume 18 Issue 1 Pages 31-38
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSExperimental and analytical studies for freezing phenomena of ethylene glycol solution around a vertical cooled polyvinyl-chloride cylinder have been performed. It is found that the crystal ice formed around the vertical cylinder is removed from the cylinder surface due to buoyancy force acting on the crystal ice. The crystal ice slides along the cylinder surface due to buoyancy force and grows in a shape of tube by joining with the neighbour ice. It is shown that the onset of ice removal condition is related to the heat flux at the cylinder surface when the latent heat of fusion is discharged with freezing, and that the heat flux ratio of 'from the cylinder surface into the cylinder' to 'from the cylinder surface to the solution' is an important parameter for the onset conditions. The ice removal occurs easily for short cylinders than for long ones.View full abstractDownload PDF (494K) -
(Direct Torque Measurement of Compressors Using the Strain Gauge)Masatoshi MATSUSHIMA, Tomohiro NOMURA, Nobuya NISHIMURA, Hiroyuki IYOT ...2001 Volume 18 Issue 1 Pages 39-50
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSThis research was conducted in order to better identify the torque loss of a hermetic rotary compressor for one revolution, and to directly obtain the actual shaft power of the compressor. A testing compressor and a gas cycle type simplified calorimeter were developed for direct measurement of the compressor torque.
A strain gauge was stuck on the shaft between a compressor and a motor. Thus, the compressor torque could be measured directly by the strain gauge and data were transmitted to out of the compressor's vessel through a slip ring. Rotational speed of the compressor was measured by using a gap sensor also. From these measurement results, actual shaft power was calculated experimentally.
On the other hand, effective compressive torque for compressing refrigerant gas was predicted theoretically. From both experimental and theoretical results, torque loss of the compressor was determined as the difference of the compressor torque from the effective compressive torque. Consequently, a loss of over-compression could be revealed from the torque loss experimentally. Furthermore, overall adiabatic efficiencies of compressors obtained by the actual shaft power were 1.1∼3.5% higher than former overall adiabatic efficiencies obtained by the motor output.View full abstractDownload PDF (686K) -
-Effect of Wall Material and Cooling rate to Ice Adhesion on Cooling Wall-Chaedong KANG, Masashi OKADA, Shinsuke ODA, Koji MATSUMOTO, Tetsuo KAW ...2001 Volume 18 Issue 1 Pages 51-59
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSAn emulsion which was a mixture of silanol-aqueous solution and silicone oil was examined as a thermal storage material for dynamic-type ice thermal storage. It was cooled and frozen under stirring in various vessels which were immersed in a controlled temperature bath. The vessels were made of stainless steel (SUS304), Pyrex glass, polycarbonate, or Teflon (PFA). The ice formation process was examined under different cooling conditions until a predetermined amount of ice was formed. The heat transfer rate and overall heat transfer coefficient were measured and the condition under which ice did not adhere on the vessel wall was examined. For all vessels, ice adhered on the wall when the heat transfer rate through the vessel wall was high. Conversely, by decreasing the heat transfer rate, a slurry ice formed without adhesion. SUS304 vessel coated with PFA material was also examined. It was shown that ice adhesion on SUS304 wall was restrained by PFA coating even though the overall heat transfer coefficient was larger than that of PFA vessel.View full abstractDownload PDF (650K) -
-Effects of the condition of supplying ice-slurry for Application to District Cooling and Heating System-Naoki AIZAWA, Masayuki TANINO, Yoshiyuki KOZAWA2001 Volume 18 Issue 1 Pages 61-72
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSFor an application of the Dynamic-type Ice Storage System to the District Cooling and Heating System, the effects of ice content (IPF) and mass flow rate of supplying ice-slurry on the ice storing characteristics in a tank were investigated by experiments and analyses. In the analytical model, we considered that the ice-rich layer would be ununiform by raising of IPF and the water permeability in the ice-rich layer increases. By raising of IPF and reducing of mass flow rate of supplying ice-slurry, ice-rich layer could not spread in a tank. The porosity of ice-rich layer was contracting to the value of 0.8-0.9 in the ice storing process. The stored ice quantity depends on distribution and porosity of ice-rich layer in a tank decreased to 10% by raising IPF from 2.5wt% to 10wt% and reducing mass flow rate as constant ice flow rate. The analytical results could express the experimental results about stored ice quantity. Our analytical model is considered to be applicable to prediction of the ice storing characteristics and to design of an ice storage tank.View full abstractDownload PDF (836K) -
-In the case of cooling mode-Shigeharu TAIRA, Ryuzaburo YAZIMA, Isamu TARUTANI, Shigeru KOYAMA2001 Volume 18 Issue 1 Pages 73-83
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSThis paper deals with an experimental study on the performance evaluation of heat pump systems using HFC alternative refrigerants. The tested heat pump systems are modified from the R22 use to alternative refrigerants. Refrigerant mixtures of R410A, R407C. R32/125 and R32/134a are tested. where R410A and R407C launched into global market recently. Pure refrigerants of R22, R32, R125 and R134a are also tested.
The experimental results of alternative refrigerants are evaluated in comparison with the result of R22, and the following are confirmed : (1) the performance of R32 is the highest. (2) adding R125 to R32 and R32/134a results into the deterioration of the performance, (3) the use of counter flow-like heat exchangers for a zeotropic refrigerant mixtures are effective, and (4) in case of R410A. the modification of the compressor to fit operating pressure heightens the performance. The effects of the performance of components on the COP are also analyzed based on the measured thermodynamic states at both ends of components in the system. Then, it is clarified that the most effective factor is irreversibility of compressors and the following is the pressure drop in low pressure side including the evaporator and the suction pipe.View full abstractDownload PDF (698K) -
Fu-jen WANG, Jeng-shing CHIOU2001 Volume 18 Issue 1 Pages 85-94
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSThe concept of finite-time thermodynamics is employed to investigate the optimal refrigeration rate for an irreversible refrigeration cycle. The heat transfer between the system (internal) fluid and cooling (external) fluid takes place at the actual heat exchanger, which has the finite-size heat transfer area and the realistic heat transfer effectiveness. The internal irreversibility results from the compression process and the expansion process are also considered. The optimal refrigeration rate is calculated and expressed in terms of the irreversibility parameter (Ir), coefficient of performance (COP), the time ratio(γ) of heat transfer processes and the effectiveness of heat exchanger. The derived COP which consider both the external and internal irreversibility can thus be considered as the benchmark value for a practical refrigeration cycle, and the parametric study can provide the basis for both determination of optimal operating conditions and design of a practical refrigeration cycle.View full abstractDownload PDF (510K) -
(Study on Fluidized Bed Heat Exchanger at Low Temperature)Yoshiyuki TAKEUCHI, Atsushi FUJIWARA2001 Volume 18 Issue 1 Pages 95-103
Published: 2001
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSIn conventional natural gas combustion power plants, vaporization heat of liquefied natural gas (LNG) has been supplied by sea water and/or air.
In the plants, cold vaporization energy has been lost without any effective utilization. An advanced technology has been developed in which carbon dioxide in the flue gas is solidified and separated as dry-ice. Carbon dioxide in the flue gas of a LNG combined cycle is cooled and solidified by the evaporation of LNG.
Fundamental studies on fluidized bed heat exchanger were carried out to analyze heat transfer phenomena at low temperature. And the fluidized bed type heat exchanger was confirmed that they had high efficiency by striping off frost solidified on the surface of heat exchanger tube. The heat transfer coefficient at -135°C was calculated about 330-370 (W/m2•K) at the condition where C02 gas was solidified.View full abstractDownload PDF (617K)
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