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Akio SAITO, Seiji OKAWA, Hiroshi NISHIMURA
1993 Volume 10 Issue 3 Pages
367-375
Published: 1993
Released on J-STAGE: September 08, 2011
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Simulation study of phase change from ice to water was carried out using molecular dynamics technique. Starting from ice formation with 576water molecules,kinetic energy was added step by step to each molecule in order to increase its temperature. It was found that the ice formation was kept in order up to a certain energy level. It indicates that the model for water molecule which usually adopted to study the behavior of liquid phase can be extended to solid phase. Beyond that level,however,the molecular arrangement started to break and without adding any extra energy to the system,the formation became disordered. The time variation of the melting process was shown graphically in cartesian coordinate. Furthermore,the result was compared with the properties of water,and it was found that the increment of the potential energy due to the change information was almost equal to a latent heat of the system. It was also found that the temperature when the ice formation started to be disordered was almost equal to melting point of the ice for the specific volume.
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Hidemasa MIKI, Fuminori SETO, Motomi NISHIMOTO, Junichi NISHIMOTO
1993 Volume 10 Issue 3 Pages
377-382
Published: 1993
Released on J-STAGE: September 08, 2011
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Recently,new method of removing water from fish fillet at low temperature using dehydration sheet have been reported. The present study is concerned with the factors to affect the quality during dehydration of horse mackerel muscle at low temperature. The rate of dehydration at -3 °C was about two times faster than that at 0 °C. The rate of denaturation of fish muscle protein was kept less than about 10 % (ATPase activity) of the undenaturated initial values after removing free water content. Present results suggest the practical possibility of the dehydration at -3 °C for keeping quality of fish flesh.
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Yutaka OGAWA, Mitsuyo UNO
1993 Volume 10 Issue 3 Pages
383-392
Published: 1993
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The gape and heave produced on the surface of tuna fish during freezing were confirmed by rupture of cylindrical type ice model. The results of experiment were shown as summarized below; 1) in case of restraining the progress of ice formation of model during freezing,any rupture was produced at not only slow freezing but also quick freezing. It was the same as tuna fish; 2) in case of closing surface of ice model covered perfectly by outside shell ice during slow freezing,it was not ruptured at not only ice model but also tuna fish. On the contrary it was cracked at quick freezing not only ice model but also tuna fish; 3) therefore it was confirmed that the rupture of tuna fish during freezing had been easy to produce at quick freezing.
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Sadayuki JITSUHARA, Yasuyuki IKEGAMI, Tsutomu NAKAOKA, Takashi MISAGO, ...
1993 Volume 10 Issue 3 Pages
393-400
Published: 1993
Released on J-STAGE: September 08, 2011
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In order to build a high-performance OTEC (Ocean Thermal Energy Conversion) plant, it becomes essential to conduct more detailed research about the evaporator. This paper describes an analytical method of large scale shell and plate type evaporator for OTEC. Numerical results, such as heat transfer rate,heat flux,heat transfer coefficient,and overall heat transfer coefficient,are shown for a titanium plate of 1.9m
2 in heat transfer surface area. Ammonia is used as the working fluid.
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Numerical Simulation and Thermal Flow Visualization under Cooling Condition
Hisashi UMEKAWA, Mamoru OZAWA, Akira KAWAMOTO, Tomonori TAKIFUJI, Masa ...
1993 Volume 10 Issue 3 Pages
401-411
Published: 1993
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Numerical simulation of gas flow in a fin-tube type heat exchanger model has been conducted. The simulation model is two-dimensional and has three inlet ports at the lower boundary and one exit port at the upper boundary. The flow field is partitioned into several sub-channels by spacers. In order to realize the uniform temperature distribution at the exit port and relatively uniform heat transfer rate among the spacers,It is necessary to arrange so that the higher temperature fluid is injected from center port at lower velocity and the lower temperature fluid is injected from both side ports at higher velocity. The thermal flow visualization experiment with thermosensitive liquid-crystal sheet has confirmed the simulation results.
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Seiji INOUE, Masahiro NAKAYAMA, Fumio MATSUOKA
1993 Volume 10 Issue 3 Pages
413-422
Published: 1993
Released on J-STAGE: September 08, 2011
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A simulation model is proposed to analyze refrigerant properties in suction,compression and discharge process in rotary compressors,and compressor performance is analyzed by the calculations and the experiments in this paper. Heat transfer coefficients between the cylinder and refrigerant both in sucking two phase and superheated gas refrigerant have been evaluated by the calculations performed under the condition of the experiments since the validity of the simulation model has been proved by the agreement of the calculation results with the experimental ones. Linear relationship of discharge and cylinder temperature to compressor frequency and suction quality has been clarified by the experimental results. Mechanisms of the compressor performance have also analyzed by the refrigerant properties in the compression mechanism calculated every angle of the rolling piston in detail.
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Katsuaki TAKAHASHI, Norio INOUE, Haruo SHINANO
1993 Volume 10 Issue 3 Pages
423-428
Published: 1993
Released on J-STAGE: September 08, 2011
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The apparent rate constants of freeze inactivation (KF) at different storage temperatures for various salts were calculated. Comparisons were then made among salts with relation to storage temperature and ionic strength of unfrozen salt solutions. For three kinds of sulfates with high eutectic points,hardly any change occured in relation to the storage temperature and ionic strength. The reason was thought to be the weaker action of sulfates to protein denaturation. The K
F values of six kinds of salts (namely NH
4Cl, NaNO
3, Mg(NO
3)
3, BaCl
2, CaCl
2 and MgCl
2 ) were highest in the temperature range of - 6~-14 °C. The extent of denaturation in the K
F value differed for each salt,although,no relationship was found between maximum KF value and eutectic point. A possible explanation for the above results relates to the amount and ionic strength of unfrozen salt solution. The log K
F increased with an increase in ionic strength,and reached a maximum at about 0.9 due to the effect of salt concentration. However,above an ionic strength of 0.9, the log K
F decreased with an increase in ionic strength due to the decrease of unfrozen salt solution.
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Takahide ITO, Hiroyuki KOBAYASHI, Makoto FUJITANI, Nobuo MURATA
1993 Volume 10 Issue 3 Pages
429-436
Published: 1993
Released on J-STAGE: September 08, 2011
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Research has been undertaken to clarify the shaft oil pump mechanisms and oil supply network systems for rotary compressors. Numerical expressions were developed for each part of the rotary compressor,(such as drive shaft,oil pump and journal bearing grooves)in order to confirm that the calculated values agree with the experimental results. Finally,a computer program has been developed to evaluate the oil supply system performance under steady conditions for rotary compressors.
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Kunikazu TORIKOSHI, Takeshi EBISU
1993 Volume 10 Issue 3 Pages
437-444
Published: 1993
Released on J-STAGE: September 08, 2011
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The evaporation and condensation heat transfer and pressure drop characteristics for HFC-134a in a horizontal tube have been studied experimentally. During the courses of both the evaporation and condensation experiments,the saturation temperature of the refrigerant,refrigerant mass flux and oil concentration in the refrigerant were varied parametrically. A smooth tube and an inner finned tube respectively were used as the tube to be tested in the present study. In addition to the oil free experiments, other experiments were performed to investigate the effect of oil-refrigerant mixture on the heat transfer and pressure drop characteristics. The present evaporation and condensation heat transfer coefficients for HFC-134a without oil in the smooth tube were found to be about 25% higher than those for CFC-12 at similar mass fluxes. Furthermore,it was found that the pressure drop through the smooth tube for HFC-134a became about 10% larger than those for CFC-12 in evaporation experiments. In the oil-refrigerant mixture experiments,the results indicated that both evaporation and condensation heat transfer coefficients for HFC-134a were influenced by the oil concentration at the large mass fluxes.
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Etsuo MORISHITA, Yoshihisa KITORA, Mitsuhiro NISHIDA
1993 Volume 10 Issue 3 Pages
445-452
Published: 1993
Released on J-STAGE: September 08, 2011
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Scroll compressors are becoming popular in air conditioning and refrigeration. This is primarily due to their higher efficiency and low noise/vibration characteristics. The scroll principle can be applied also to the steam expander and the Brayton cycle engine,as shown in the past literature. The Otto cycle spark-ignition engine with a scroll compressor and expander is studied in this report. The principle and basic structure of the scroll engine are explained,and the engine characteristic are calculated based on the idealized cycles and processes. A prototype model has been proposed and constructed. The rotary type engine has always had a problem with sealing. The scroll engine might overcome this shortcoming with its much lower rubbing speed compared to its previous counterparts,and is therefore worth investigating.
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Shigehiro UEMURA, Masahiro NOGUCHI, Sadayasu INAGAKI, Takuya TERAOKA
1993 Volume 10 Issue 3 Pages
453-460
Published: 1993
Released on J-STAGE: September 08, 2011
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Production restriction of CFCs which are used for refrigerators and air conditioners has been implemented through the international mutual agreement approved by the Montreal Protocol. Due to the less impact on the ozone layer dep1etion, alternative refrigerants for CFCs had included HCFC-123 and HCFC-22. However, H CFC-123 and HCFC-22 do not completely prevent the ozone layer depletion. This paper presents the investigation results of HFC-125, H FC-143a, HFC-152a, and HFC-32 which prevent the ozone layer depletion and are candidates for alternatives of CFCs and HCFCs.
The test results of thermal stability of these refrigerants are similar to those of CFC-12 and HCFC-22. The test results show that each refrigerant has different material compatibility. The test results of lubricant solubility show that synthetic oi1s are soluble in these refrigerants, but the mineral oils currently in use for CFCs and HCFCs are not. The refrigeration performance based on the calculated thermodynamic properties corresponds with that of the experimental results.
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Isao KAWABE, Tsutomu ICHIKAWA, Masayuki HIBI, Masayoshi NAKAMURA
1993 Volume 10 Issue 3 Pages
461-466
Published: 1993
Released on J-STAGE: September 08, 2011
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The 2in1 type scroll compressor has been developed to cope with needs for mounting it in multisystem air conditioners for buildings,in which two scroll compressor units of different capacities are housed in a casing and one unit is controlled by the inverter. The development of the 2inl type scroll compressor brought about the following merits : 1)Having a variable capacity range of 2.9 KW to 29 KW,the air-conditioners can apply to various loading conditions including multi-system air conditioners for buildings. 2) The wider capacity range results in a higher efficiency and realized the multi-system air conditioners in higher efficiencies. 3) Reliability of the new system became satisfactory for the cycle of long piping and high refrigerant charge.
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Kiyoharu KUTSUNA, Teiichi NABETA, Akio WADA
1993 Volume 10 Issue 3 Pages
467-474
Published: 1993
Released on J-STAGE: September 08, 2011
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A new instrument has been developed for an on-line real-time measurement of oil circulating rate in refrigeration system utilizing a ultra-violet light absorption behavior of oil. A dual optical path configuration is introduced to the flow cell of this instrument,and it allows the instrument to perform dual beam absorbance measurement which contributes to provide quite stable and precise result. This instrument is applied on OCR measurement on several refrigeration system in transient state.
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Helical Blade Compression Mechanism
Toshikatu IIDA, Takayoshi FUJIWARA, Masayuki OKUDA, Hirotsugu SAKATA, ...
1993 Volume 10 Issue 3 Pages
475-482
Published: 1993
Released on J-STAGE: September 08, 2011
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A new compression mechanism named "helical blade" has demonstrated a good performance essential for a quiet and high efficient compressor which can be used in both users and environment friendly systems the compressor is basically a rotary and positive displacement type machine which consists of a rotating cylinder and a rotating rotor piston with spiral blade. This paper presents a compression mechanism,a theoretical analysis on the performance and a prototype model design and performance. Testing results have indicated that the performance of the prototype model remains nearly the same as that of current models of our rolling piston rotary compressors.
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Takao YOSHIMURA, Takashi KOYAMA, Ichiro MORITA, Masanori KOBAYASHI, To ...
1993 Volume 10 Issue 3 Pages
483-491
Published: 1993
Released on J-STAGE: September 08, 2011
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In general,the vibration of rolling piston type rotary compressors is greater than that of reciprocating compressors because the compressor-motor unit is fixed to the shell. It is therefore necessary that refrigerators utilizing rotary compressors incorporated a vibration-proof design. This paper refers to the experimental vibration reduction study of rotary compressors (horizontally installed) for household refrigerators and other appliances. The vibration of rotary compressors consists of the rotational vibration caused by the speed variation of the shaft and of the imbalance vibration caused by the mass imbalance in the rotation system. There are various methods for reducing the rotational vibration. This study researched the dynamic damper. It will be shown that the dynamic damper,using a helical extension spring applied to the outside of the shell,is effective in reducing vibration. In regards to the imbalance vibration,this paper researched the influence of the number of correction planes and the accuracy of the balancing.
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Shinobu SATO, Tadao MACHIDA, Kenji KOMINE
1993 Volume 10 Issue 3 Pages
493-501
Published: 1993
Released on J-STAGE: September 08, 2011
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In view of a wide range of its speed and a long operation period,attempts have been made to develop high reliability of an inverter controlled compressor designed for a residential heat pump unit. A significant improvement in the long term reliability has been demonstrated by employing a ion-nitrided crankshaft which would help minimizing wear of the bearing. This paper presents the dependency of breaking-in phenomena in hermetic rotary compressors on material combination and discusses the relationship between chemical reaction and wear progressiveness of sliding surface.
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Tadashi IIZUKA, Hiroaki HATA
1993 Volume 10 Issue 3 Pages
503-509
Published: 1993
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In concerning with the trend for the phase out of CFC's,we have developed the technology for the rolling piston type rotary compressors for refrigerators using HFC134a. It is known that the reliability of compressors is less when using HFC134a for conventional compressors without any modifications than that when using CFC12. We have estimated some kinds of refrigerating oil,materials for motors,mechanical parts, and their compatibility for HFC134a. The life test using the compressors with the new oil,motor materials,and modified mechanical parts was carried out and it has been found that the reliability equivalent to that of CFC12 system can be maintained. However,this test only could estimate there liability of compressors under a certain limited condition. So we are now continuing extend examination to adapt the above-mentioned technology to various actual use.
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Kiyoshi SAWAI, Michio YAMAMURA, Yoshinori KOJIMA, Shuichi YAMAMOTO, Sa ...
1993 Volume 10 Issue 3 Pages
511-517
Published: 1993
Released on J-STAGE: September 08, 2011
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This paper presents the construction,newly developed design technologies and performance characteristics of a compact horizontal scroll-type compressor for room air conditioners. The authors were able to develop a compact variable speed horizontal scroll-type compressor with a cooling capacity of 1.8 kW,which necessitated the development of new mechanisms,namely,an axial compliance mechanism for compensating liquid compression,an oil pump mechanism for lubrication and a suppression mechanism for oil discharge. Use of the new compressor in room air conditioners made it possible to reduce the external unit of the air conditioner by about 25 %. The new compressor possesses a high efficiency : about 10% higher especially at low speed operation.
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