日本冷凍空調学会論文集
Online ISSN : 2185-789X
Print ISSN : 1344-4905
ISSN-L : 1344-4905
23 巻, 1 号
選択された号の論文の10件中1~10を表示しています
研究レビュー
論文
  • - オフセット長さの影響 -
    井村 英昭, 小糸 康志
    2006 年 23 巻 1 号 p. 13-23
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    This paper describes the heat transfer characteristics in a two-phase crank-shape closed thermosyphon. Usually, the thermosyphon is composed of an evaporator, an adiabatic section and a condenser arranged on a straight tube. However, a bent geometry of the thermosyphon is sometimes needed to use because of the limited space for the straight thermosyphon to be installed. Therefore, in the present study, the crank-shape thermosyphon is investigated on the heat transfer coefficients and the critical heat fluxes. The evaporator and the condenser are positioned vertically and the adiabatic section horizontally. The inside diameter of thermosyphon is 16 mm and each length of the evaporator and condenser is 500 mm. As a working fluid, water is used. The inside temperature (the adiabatic wall temperature) is varied from 40 to 80 °C. The distance between the centers of the vertical evaporator and condenser, i. e. , the offset length is varied from 220 to 620 mm, and the effect of the offset length on the heat transfer characteristics is presented.
  • - 凍結回避のための限界流速と氷による管閉塞時間 -
    千葉 良一, 泉 正明
    2006 年 23 巻 1 号 p. 25-32
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    A freezing phenomenon in forced convectional flow inside a pipe is investigated numerically in this paper .The numerical analysis is carried out to assess the transient freezing behavior of flowing water inside a pipe cooled from surroundings in consideration of pressure drop caused by the freezing. The finite element technique is applied to solve the equations of motion and energy transport for laminar flow. The numerical model attempts to capture the solid-fluid interface on a fixed computational grid. The correlations among cooling conditions of pipe, velocity and temperature of water at the inlet, and location at which the freezing starts are examined to show the critical velocity to avoid freezing. In addition, under the condition that pressure remains constant at the inlet, the period in which the pipe is not blockaded by ice is calculated. The period is illustrated with some dimensionless parameters to predict the conditions under which blockage occurs within a given time.
  • - 室内潜熱負荷を考慮した装置規模, システム性能の推算-
    大蔵 将史, 児玉 昭雄
    2006 年 23 巻 1 号 p. 33-44
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    Solar assisted desiccant coo1ing process is an effective means to reduce a latent heat load of the ventilation air. This paper describes the influences of ambient humidity and sensible heat factor (SHF) of the indoor room on the performance and scale of the desiccant cooling system. Two process configurations termed “ambient air mode” and “mixed air mode” were assumed. At “ambient air mode”, only ambient air is dehumidified and cooled in the desiccant process. The dehumidified air stream is mixed with return air and further cooled in the cooling coil. At “mixed air mode”, ambient air is mixed with return air and this mixed air stream is dehumidified in the desiccant process and cooled at the cooling coil. At “ambient air mode”, ambient air humidity had a significant impact on required amount of dehumidification since humid ambient air entered the desiccant process directly. In this case, higher temperature level and quantity, which is impossible to be supplied from commonly commercialized flat panel solar collectors, was required. At “mixed air mode”, the influence of increase of ambient humidity was not significant since humidity of the air entering the desiccant process became low by mixing with return air. At this mode, it was expected that 70°C of the circulating water and 37m2 of surface area of solar collector could produce a sufficient dehumidifying performance even in high latent heat condition. The contributing ratio of the desiccant wheel was also estimated. The ratio increased in higher latent heat condition due to increase of required amount of dehumidification. The contributing ratio of the thermal wheel became lower due to increase of saturated air temperature in the evaporative cooler.
  • - 室内還気を再生空気とする全換気型プロセスの性能評価 -
    安藤 幸助, 児玉 昭雄, 岡野 浩志, 浅田 敏信
    2006 年 23 巻 1 号 p. 45-55
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    2-rotor desiccant cooling process consisting of a honeycomb rotor dehumidifier and a sensible heat exchanger is a mainstream of the desiccant cooling process which are practically applied to supermarket, hospital and so on. However, this process cannot produce a sufficient dehumidifying performance in high humidity region. In this study, 4-rotor desiccant cooling process equipped with a double stage dehumidification was proposed and investigated experimentally. In this process, regeneration temperature around 60°C could produce a sufficient dehumidifying performance even at high ambient humidity. “Serial heat supply” mode was considered to improve the heat efficiency by the cascade use of regeneration heat inside the cooling cycle. The dehumidifying performance of the “serial heat supply” mode was only slightly lower than that of a “parallel heat supply” mode at which the same temperature hot air was supplied to the both heaters. However, dehumidifying performance of this “serial heat supply” mode was much higher than that of conventional 2-rotor desiccant cooling process. Furthermore, the desiccant rotors of 0.1m in thickness were mounted to 4-rotor desiccant cooling process in place of the 0.2m desiccant rotors. It was found that the drop of dehumidifying performance of the process equipped with 0.1m desiccant rotors was only by 10 percents comparing with the 0.2m rotor process. Moreover, it was found that optimization of rotation speed of the desiccant rotor was needed to improve the energy efficiency. Regarding the supply point of return air, it was also found that return air should be supplied to the regeneration inlet of the second stage for higher dehumidifying performance.
  • 高橋 宏行, 佐伯 主税, 小山 繁
    2006 年 23 巻 1 号 p. 57-65
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    This paper presents the experimental results on the outside condensation heat tral1sfer coefficient of horizontal enhanced filmed tubes. Three different fin geometry types of three-dimensional enhanced finned tubes were tested. A low-fin-tube (LFT) 19 fin-per-inch (fpi) was also tested for reference. Experimental refrigerant used was R134a. The heat tral1sfer coefficient test was carried out at a condensing temperature of 40°C, at a cooling water velocity of 1.5 m/s, and the heat flux of 10 to 110 kW/m2K. The outside condensation heat transfer coefficient of all three dimensional enhanced finned tubes were approximately 1.9 times higher than that of LFTl9fpi at high heat flux range. In low heat flux range, the enhanced finned tube of small circumferential segmentation pitches at the fin tip was shown the highest outside heat transfer coefficient for all tubes tested.
  • 藤井 康彦, 木村 繁男, 齋藤 隆之, 木綿 隆弘, 松村 和彦
    2006 年 23 巻 1 号 p. 67-78
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    Recently, the noise caused by the refrigerant fluid is spotlighted due to the demand of low noise home and office air conditioners. Especially, reduction of refrigerant fluid noise and vibration noise generated from throttle in the expansion valve is becoming important. Therefore in this study it is intended to resolve fluctuating phenomena of fluid, which may be the cause of noise, by flow visualization and measurement of fluid pressure and temperature at throttle valves, focusing on two-phase flow of refrigerant fluid. A test equipment suitable for flow visualization of R410a refrigerant was developed by epoch making design and manufacturing method. Visualization was realized by laser beam irradiated on the visualization equipment and by high-speed video camera. Test conditions are set of combinations of 4 different conditions of compressor revolution and 4 different conditions of valve opening of expansion valve. As results of the following conclusions are drawn. (1)A visualization technique of throttle of expansion valve has been developed by manufacturing visualization equipment, which is most suitable to the test. (2)It has been confirmed that refrigerants is liquid and two-phase condition in the upstream of throttle, where a needle is inserted and that refrigerant fluid flow in two-phase in the downstream of throttle.
  • Mongkol CHEEVAPORANAPIVAT, Hisaharu SAKAI, Yuuji MINE, Manabu WATANABE ...
    2006 年 23 巻 1 号 p. 79-84
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    Application of ORP as a rapid indicator for grading tuna's freshness on the ship was studied. The long line trawling process was used for catching the sample tuna in the South Pacific Ocean. All captured sample tuna were weighed, gender identified and investigated for their mortality, then measured ORP and K value. Three species of tuna were caught: blue marlin (Makaira mazara), yellow fin tuna (Thunnus albacares), and swordfish (Xiphia gladius). Most of the fish captured were male and they had been dead after picking onboard. The measured ORP values of blue marlin varied in the range of 0.295-0.362 Volt, with pH between 5.35-5.84. Both ORP and pH of swordfish was similar to that of blue marlin. But for yellow fin tuna, the ORP value was about the same as blue marlin while its pH was significantly higher. ORP value in all species tended to increase with pH of the fish meat decrease. It is interesting that ORP value of tuna increased in correlation with K value. These results suggested that ORP and pH change, which are measured in the short time, are the effective indicators for grading tuna's freshness on-board.
  • 赤木 智, 党 超鋲, 飛原 英治
    2006 年 23 巻 1 号 p. 85-95
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    Recovery of expansion work in vapor compression heat pump cycle has gained much attention as a means of improving COP of carbon dioxide heat pump. Instal1ation of a two-phase ejector is one of the most promising ways of recovering expansion work. This paper is aimed at clarifying the characteristics of COP of ejector-equipped vapor compression heat pump cycle. Firstly, the ejector efficiency is defined as an isentropic efficiency of the ejector, and then the COP is compared with the conventional cycle and the expander-equipped cycle, which is another expansion-work-recovering cycle. The effects of internal heat exchange and compressor efficiency on expansion-work recovering cycle is clarified. After that, optimum design of the ejector is shown based on one-dimensional calculation of the fluid flows in the ejector. The efficiency of the ejector shows optimum when the suction flow is choked if the efficiencies at convergent mixing cone and diffuser are unity respectively. Finally, the performance of part load operation is clarified based on the fluid analysis in the ejector
  • 赤木 智, 党 超鋲, 飛原 英治
    2006 年 23 巻 1 号 p. 97-104
    発行日: 2006年
    公開日: 2011/10/11
    ジャーナル フリー
    An experimental investigation was performed to analyze the characteristics of a two-phase ejector in carbon dioxide operated heat pumps. Firstly, this paper shows the way how the ejector behaves in the heat pump cycle. The influence of the diameter and the length of mixing tube on ejector performance is studied. Mixing tube diameter has a great influence on pressure recovery according to the conservation of momentum. Mixing tube diameter also has an influence on the acceleration of suction flow before mixing tube entrance, which changes pressure recovery, too. When the mixing tube is too long, the ejector performance slightly becomes worse because of frictional loss. When the mixing tube is too short, the ejector performance drastically deteriorates, because the driving and suction flows pass the mixing section before they are mixed sufficiently. The highest ejector efficiency shown in this paper is 0.46, which corresponds to 23-24% of COP improvement.
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