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Volume 12 (1995)
- Issue 3 Pages 225-
- Issue 2 Pages 135-
- Issue 1 Pages 1-
Volume 12, Issue 2
Displaying 1-10 of 10 articles from this issue
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Review Article
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Masaaki OKADA1995 Volume 12 Issue 2 Pages 135-145
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSIn this paper, current researches for surface tension of alternative refrigerants are reviewed. The refrigerants of interests are seven HCFCs: namely R-123, R-123a, R-124, R -141b, R-142b, R-225ca and R-225cb, and six HFCs; namely R-23, R-32, R-125, R-134, R- 134a and R-152a. The available data and correlations of experimental surface tension for HCFCs and HFCs are summarized. Most of experimental data were obtained by using capillary rise method. With regard to R-123 and R-134a, new surface tension correlations have been developed and are accepted as the international standard. For other refrigerants, the author selected one correlation for each refrigerant as a recommended correlation. In addition, graphical estimation method of surface tension for binary mixture is introduced. In particular, more research is expected on the surface tension of mixture in the future.View full abstractDownload PDF (516K)
Paper
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Yoh MATSUZAKI, Yutaka OGAWA1995 Volume 12 Issue 2 Pages 147-155
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSThe freshness and meat colour of fresh skipjack can be retained only 2 or 3 days by ordinary cold storage.
This paper deals with a new method, "suprchilling", which was developed by the authers, i. e., immediately after catch live skipjacks were immersed and killed instantly in NaCl brine at -10°C to -15°C for 30 to 40 minuites and thereafter in refrigerated sea water the center of the skipjack muscle was rapidly cooled to -0.5°C within 40 minuites.
Form the results of apperance, organoleptic ratings, pH value, K value, metmyoglobin %, salt concentration and microscopic observation, "superchilling" could prolong the shelflife of skipjack 3 days longer than ordinary cold storage.View full abstractDownload PDF (429K) -
Yao Xing HU, Tomoo MIHORI, Hisahiko WATANABE1995 Volume 12 Issue 2 Pages 157-164
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSMost of the published methods for estimating the freezing time require thermal properties of the product and any relevant heat transfer coefficients between the product and the cooling medium. However, the difficulty of obtaining thermal data for use in industrial freezing system of food has been pointed out. We have developed a new procedure for estimating the time to freeze a food of a slab by using the inverse method, which does not require the knowledge of thermal properties of the food being frozen. The method of applying inverse method to estimation of freezing time depends on the shape of the body to be frozen. In this paper, we explored the method of applying inverse method to the food body of cylindrical shape, using selected explicit expressions to describe the temperature profile. The temperature profile was found to be successfully approximated by a logarithmic function, with which an approximate equation to describe the freezing time was derived. An inversion procedure of estimating freezing time associated with the approximate equation, was validated via a numerical experiment.View full abstractDownload PDF (388K) -
Experimental Study on Effects of Frequency and Mean Pressure on Heat Pumping by Acoustic OscillationAkira KAWAMOTO, Mamoru OZAWA, Masaki KATAOKA, Tomonari TAKIFUJI1995 Volume 12 Issue 2 Pages 165-176
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSExperimental studies were conducted for the fundamental understanding of the thermoacoustic behavior in the simulated resonance-tube refrigerator with special reference to the effect of imposed frequency and mean pressure. The resonance frequency in the case of helium was lower by about 20% than the theoretical prediction, while the experimental value in the case of air was almost the same as the theoretical one. The temperature difference observed along the stack increased with the increase in the amplitude of acoustic pressure, and decreased with the increase in the mean pressure, Based on the simplified model of heat pumping process, the relationship between the temperature variation and the acoustic pressure field was formulated, and thus the characteristic parameter which represents overall heat transfer between gas and stack plates or heat exchangers was obtained.View full abstractDownload PDF (663K) -
Satoru MOMOKI, Jian YU, Shigeru KOYAMA, Tetsu FUJII, Hiroshi HONDA1995 Volume 12 Issue 2 Pages 177-184
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSThe experimental study is reported on the forced convective boiling of pure refrigerants HCFC22, HFC134a and HCFC123 flowing in a horizontal microfin tube. The local heat transfer coefficient defined based on the actual inside surface area is measured in the ranges of mass velocity of 200 to 400 kg/m2s, heat flux of 5 to 64 kW/m2 and reduced pressure of 0.07 to 0.24. Using the Chen-type model, a new correlation for microfin tubes is proposed considering the enhancement effect of microfins on both the convective heat transfer and the nucleate boiling components. In the convective heat transfer component, the correlation to predict the heat transfer coefficient of liquid-only flow is determined from preliminary experiments on single-phase flow in microfin tubes, and the two-phase flow enhancement factor is determined from the present experimental data. For the nucleate boiling component, the correlation of Takamatsu et al. for smooth tube is modified. The prediction of the present correlation agrees well with present experimental data, and is available for several microfin tubes which were tested by other researchers.View full abstractDownload PDF (359K) -
Development of Heat Exchangers for Air-conditioners Capable of Supplying High-temperature (80°C) AirMasaaki ITOH, Kazumoto URATA, Hiroaki MATSUSHIMA, Yoshifumi KUNUGI, Hi ...1995 Volume 12 Issue 2 Pages 185-190
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSA new kind of heat exchanger for air conditioners was studied analytically and experimentally and the following results were obtained.
To supply high-temperature air, it is effective to use "Pair Heat Exchangers" where fins are separated between pipe rows and the refrigerant flows counter-crosswise to the air flow.
These heat exchangers enabled air at 80°C to be supplied by HCFC-22 air-conditioners when the discharge pressure was 3.0 MPa and refrigerant temperature at the inlet of heat exchanger was 120°C.
The main effect of dividing fins is to prevent heat conduction between pipe rows through the fins.View full abstractDownload PDF (260K) -
1st Report, Experimental ResultsMasahiro FURUKAWA, Masao KAJI, Takeharu NISHIZUMI, Shinji OZAKI, Kotoh ...1995 Volume 12 Issue 2 Pages 191-200
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSTo improve the thermal performance of high temperature generator of absorption chiller/heater, heat transfer characteristics of flow boiling of lithium bromide aqueous solution in the subcooled region were experimentally investigated. Experiments were made for water and lithium bromide aqueous solution flowing in a rectangular channel (5 mm × 20 mm cross section) with one side wall heated. Boiling onset quality of lithium bromide aqueous solution is greater than that of water. The heat transfer coefficient of lithium bromide aqueous solution is about a half of that of water under the same experimental conditions of inlet velocity and heat flux. The experimental data of heat transfer coefficient for water are compared with the empirical correlation of Thom et al.11) and a fairly good agreement is obtained. The predictive calculations by the method of Sekoguchi et al.12) are compared with the data for water and lithium bromide aqueous solution. Agreement between them is good for water, while the results for lithium bromide aqueous solution are not satisfactory.View full abstractDownload PDF (471K) -
2nd Report, Theoretical Prediction of Heat Transfer CoefficientMasao KAJI, Masahiro FURUKAWA, Takeharu NISHIZUMI, Shinji OZAKI, Kotoh ...1995 Volume 12 Issue 2 Pages 201-210
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSA theoretical prediction model of the boiling heat transfer coefficient in the subcooled region for water and lithium bromide aqueous solution flowing in a rectangular channel is proposed. In the present heat transfer model, a heat flux is assumed to consist of both the forced convective and the boiling effect components. The forced convective component is evaluated from the empirical correlation of convective heat transfer coefficient for single-phase flow considering the effect of increase of liquid velocity due to net vapor generation. Empirical correlations for determining the heat flux due to the boiling effect and the quality at the onset point of net vapor generation are obtained from the data presented in the first report1). Agreement between the present theoretical prediction and the experimental data is satisfactorily good both for water and lithium bromide aqueous solution.View full abstractDownload PDF (465K) -
Yoshimu YAZAKI, Hideaki YOSHIOKA1995 Volume 12 Issue 2 Pages 211-217
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSIn the experimental analysis of cooling towers, it is not necessarily easy to obtain the values of air and water phase film volumetric coefficients, because the experimental conditions are limited to which the Mickley's graphical method is applicable.
The purpose of this study is to predict the individual coefficients using more practical method based on the penetration theory for water film. The tower used in this study is of a commercial induced draft counterflow type. Water-cooling experiments were made with constantly designed air and water flow rates and with varied water temperatures. Then, we attempted to predict the individual coefficients from these over-all results by means of the reported procedure.
Finally, applying our method to the similar experimental date of other workers, we obtained nearly equal results compared with the Mickley's method.View full abstractDownload PDF (398K) -
Masaaki ITOH, Hiroshi KOGURE, Masahiro MIYAGI, Sadanari MOCHIZUKI, Yos ...1995 Volume 12 Issue 2 Pages 219-224
Published: 1995
Released on J-STAGE: October 11, 2011
JOURNAL FREE ACCESSTo reduce the depth of the indoor heat exchanger in room air-conditioners, we studied fin and tube heat exchangers, and found that we could make the heat transfer coefficient of fins 30% higher than of conventional fins by reducing louver width and fin pitch.
We also improved water drainage on the surface of the fins by adopting accordion-type offset-fin heat exchangers.
We found that the material cost of a heat exchanger was minimized when the heat exchanger had a tube 7 mm in diameter, and we could increase the heat transter coefficient of the refrigerant side by developing a new grooved tube 7 mm in diameter.
We succeeded in making the heat exchanger 40% thinner than conventional types.View full abstractDownload PDF (275K)
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