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-The effect of projection on flat-tube inner wall and lubrication oil on heat transfer-
Masafumi KATSUTA , Ryo SATO, Akira YAMASHITA, Toru KUROIWA
2014 Volume 31 Issue 3 Pages
257-264
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
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After the phase out of R12, R134a has been used successfully for car air-conditioners. However the refrigerant having more than 150 GWP like R134a is prohibited to use by the MAC regulation. As the alternative R134a, the low GWP (GWP=4) refrigerant HFO-1234yf was developed, and its thermo-physical properties are similar to that of R134a. This refrigerant might be expected as taking the place of R134a. Therefore we have been investigating the condensation heat transfer in a flat multiple-hole aluminum tube. This research was especially focused on the influence of inner wall projection and lubrication oil on condensation heat transfer performance. The experimental apparatus was general refrigerating cycle which consisted of compressor, condenser, expansion valve, and evaporator. Test section of the condenser was double tube of counter-flow type, and the refrigerant flowing in the inner tube was condensed by heat exchange with cooling water flowing in the annular section. Finally, comparison of heat transfer and pressure drop was made under various experimental conditions taking into account the effect of inner wall projection and lubrication oil concentration level.
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－3rd Report: Evaluation of Refrigerant Flow Characteristics using a Single-Row Staggered Arrangement Model, and Various Two-Row Models －
Katsunori HORII, Keishi KARIYA, Yuki NAKASHIMA, Syunsuke MATSUMOTO, ...
2014 Volume 31 Issue 3 Pages
265-276
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
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This study focuses on characteristics of refrigerant flow and heat transfer inside the evaporator tube to improve performance of defrosting for refrigerator. In the first report, evaluation of refrigerant vapor-liquid two-phase flow using the test sections of single-row model simulating the refrigerator evaporator was examined under heating condition, and basic flow characteristics were clarified. In this report, evaluation of refrigerant flow under heating condition was carried out using test sections of a single-row staggered arrangement, and various two-row models. It was found, in the staggered arrangement model, that refrigerant flow had the same characteristics as those in the simple single-row model reported in the first report, but the process time of the change became short. It was furthermore found, for the two-row models, that refrigerant flow pattern was generally different in the rows connected and not connected to an accumulator, but, in the two-row fin-tube model, the change of tube wall temperature in both rows was not different from or similar to each other due to heat conduction through the fin, regardless of the different refrigerant flow pattern.
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－4th Report: Evaluation During Defrosting Process using a Two-Row Fin-Tube Model－
Katsunori HORII, Keishi KARIYA, Yuki NAKASHIMA, Syunsuke MATSUMOTO , ...
2014 Volume 31 Issue 3 Pages
277-288
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
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This study focuses on characteristics of refrigerant flow and heat transfer inside the evaporator tube to improve performance of defrosting for refrigerator. In the second report, refrigerant flow and heat transfer under defrosting condition were evaluated and clarified using the test section of single-row fin-tube model. In this report, evaluation for the test section of two-row fin-tube model was carried out. It was made clear,refrigerant flow in the row connected to an accumulator was the same characteristics as those in the single-row model. But in the other row, refrigerant vapor generated in the lower part of the test section went up to the upper part without lifting liquid, and then condensed at the upper part with releasing heat. In both rows, heat released due to vapor condensation inside the tube contributed to the frost melting. This heat transport by refrigerant vapor from lower part to upper part was significantly effective in the frost melting at the upper part of the test section far from the heater. As the results, the defrosting finishing time was reduced.
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Ryota IIJIMA, Masaki KOYAMA
2014 Volume 31 Issue 3 Pages
289-296
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
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To achieve high efficiency of scroll compressors in wide capacity range, a pulse width modulation(PWM) bypass capacity control system for air conditioners has been developed and the fundamental characteristics of the system was investigated in this study. Pressures and power inputs were measured to clarify the dynamic characteristics. Then the PWM period was determined by means of a numerical simulation, where calculated pressures were in good agreement with these of the measurement. Using this period, the performance tests of the compressor with PWM bypass capacity control were carried out. In the results, the capacity reached 30% of the load corresponding to the lower limit of rotational speed, and the calculated efficiencies were shown to agree well with these of the experiments.
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Rika KOBAYASHI, Naohiro KANESAKA, Manabu WATANABE, SUZUKI Toru
2014 Volume 31 Issue 3 Pages
297-303
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
Advance online publication: August 29, 2014
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Since the quality of frozen food depends on the size of ice crystals, many studies have investigated the growth mechanisms of ice crystals in frozen foods. Recently, it was found that in the typical freezing process, the finer ice crystals formed in soybean gels with large-scaled supercooling incidentally occurred during the cooling process (we called it “supercooled freezing method”)as compared with that formed by freezing without supercooling at the same cooling rate. In order qualify the mechanism of the ice crystal growth in supercooled freezing method,the effect of breaking temperature of supercooling on the ice characteristics of soy bean gels, including their effects on drip loss , was investigated. The results revealed that a lower breaking temperature of supercooling provided the finer ice crystals and large number of ice crystals. Further, a lower breaking temperature of supercooling produced the lower volume of drip loss. It was suggested that these results were related to the higher degree of ice nucleation at low breaking temperature of supercooling.
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Katsuyuki TANAKA
2014 Volume 31 Issue 3 Pages
305-310
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
Advance online publication: July 30, 2014
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apor pressure and saturated liquid density for R 347mcc (CF
3CF
2CF
2OCH
3, 1-methoxyheptafluoropropane) were measured in the temperature range from 300 K to 400 K at intervals of 10 K. The apparatus is consist of a large cell and a small cell with a pressure sensor on the princi
-p
3 le of the extraction method. Experimental uncertainties are 0.028 K for temperature, 0.4 kPa for pressure and 0.7 kg
‧m for density. On a basis of the present data, correlations of vapor pressure and saturated
-liq
3 uid density were formulated. The standard deviations from correlations were 0.4 kPa for vapor pressure and 0.5 kg
‧m for saturated liquid density. In addition, the calculations from correlations are compared with the literature values.
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－Air-conditioning of Artificial Light Type Plant Factory－
Toshiro INOU, Ryozo INADA
2014 Volume 31 Issue 3 Pages
311-316
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
Advance online publication: August 29, 2014
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In the third booming of the plant factory in Japan, the number of plant factory increases with the increase of the number of enterprises that participate into this business in the last several years. The environmental control technology, which mainly consists of lighting and air-conditioning, is very important for the plant factory. However, in many plant factories the package type air-conditioner was adopted mainly due to the initial cost reduction. This study will show the current situations, such as the requirements to the air-conditioning, and the load profile of the air-conditioning system in the plant factory. Also, by analyzing the measured temperature and humidity data, to identify the problems and suggest the solutions.
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－Feasibility Study of Solar Thermal Energy Utilization to Plant Factory－
Nobuya NISHIMURA, Tametoshi MATSUBARA, Hiroyuki IYOTA, Yosuke SHIRAYAN ...
2014 Volume 31 Issue 3 Pages
317-329
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
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This paper presents the feasibility of solar thermal energy utilization to plant factory. Performance and operationcharacteristics of the solar driven absorption chiller heater of 352 kilowatt refrigeration capacity were investigated byusing long term demonstration test data of June 2009 to October 2013. Effects of solar insolation to the absorption chillerheater performance were examined by changes of air conditioning load ratio and solar position. As a result, it wasdemonstrated that the COP in case of parallel operation by solar energy and town gas becomes 20 to 50 percent higher thanthat case of another operation modes. Also, Seasonal performance of the system is calculated based on the appearancefrequency (weight) of the outdoor temperature. The air-conditioning load ratio was sorted out for every outdoortemperature based on the data measured during 5 seasons from 2009 to 2013 to obtain the averaged COP value. COP takesthe maximum value at the air-conditioning load ratio of 30% and decreased at both higher and lower ratios than that.
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Mami SUZUKI, Seiji MATSUO, Hiroki UMEDA, Yasunaga IWASAKI
2014 Volume 31 Issue 3 Pages
331-337
Published: December 31, 2014
Released on J-STAGE: September 30, 2015
Advance online publication: August 15, 2014
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To identify an effective method of CO
2 supply for greenhouse production (plant factory), the effect of increased relative humidity levels (level 1; an average of RH 74.5%; level 2; an average of 86%, and level 3; an average of 97.8%) in growth chambers with cucumber seedlings was investigated under elevated CO
2 concentrations. The photosynthetic rate of seedling growth under CO
2 levels at 1000 ppm was higher than that under CO
2 levels at 500 ppm. In addition, the leaf area of seedlings was larger under level 2 than under level 1. Thus, dry matter production and relative growth rate (RGR) were largest when seedlings were grown in the level 2 chamber. These results indicate that dry matter production increased because of the photosynthetic rate and expansion of leaf areas due to higher humidity. In contrast, dry matter production decreased under level 3 because it was influenced by reduction of photosynthetic rate and in expansion of leaf areas. These results indicate that there is an optimal humidity level for CO
2 supply. Humidity levels should be evaluated according to the photosynthetic rate, leaf area, transpiration, and nutrient uptake, for the production of greenhouse vegetables.
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Teruo WADA
2014 Volume 31 Issue 3 Pages
339-343
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
Advance online publication: August 15, 2014
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June-bearing strawberries cannot be produced in summer because they require low temperatures and short days for flower bud formation, and because high air temperatures decrease fruit yield and quality. I tried to produce fruits of June-bearing strawberry in summer by controlling day length and air temperature. Seedlings of three cultivars, ‘Sachinoka’, ‘Benihoppe’, and ‘Marihime’, were transplanted to a greenhouse in autumn 2012 and grown in rockwool culture. In late spring 2014 the growing area was covered with shade cloth having heat-insulating properties. Day length was controlled to 12 h and the air was cooled initially to 28/15°C (initially) and then to 28/10°C in summer. In the control, air temperature was not cooled. In the air-conditioned area, the vapor pressure deficit was always lower and the CO
2 concentration in the dark period was higher than in the control. In control plants, fruit yield after May was very low, and no fruit was harvested in September, while the air-conditioned plants produced similar yield as in winter. Soluble solids content and firmness of fruits in the air-conditioned area in summer were higher than in fruit harvested in winter.
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Sayoko KOMATSU, Yasushi UEDA, Nobuya OKAMURA, Toshirou INOU, Atsumasa ...
2014 Volume 31 Issue 3 Pages
345-357
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
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A plant factory generally refers to a plant cultivation facility having a cultivation environment control system. It is capable of producing plants all year around owing to optimized control of lighting, air temperature, humidity, and airflow. Adjustments to CO2 concentration and lighting enable shorter cultivation periods. Plant factories are required to reduce cost of air-conditioning. Also, optimal air-conditioning system for plant factories are required to increase harvests of plants. The purpose of this study is to develop an optimal air-conditioning system for plant factories. In that regard, an air-conditioning simulation method with cultivated plants is proposed. A unique feature of this method is that it takes the living activities of plants into account. This method takes into account effect of transpiration on air temperature, humidity and effect of photosynthesis on CO2 concentration. By analyzing photosynthesis, the fresh weight of plants can be estimated. This paper describes about the simulation method, and describes the growing tests of plant characteristic values which are taken into the simulation. Simulation accuracy is also evaluated by comparing it with experimental results.
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Ryuta UDO, Shogo MORIYUKI, Kazuya UKAI, Hirokazu FUKUDA
2014 Volume 31 Issue 3 Pages
359-365
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
Advance online publication: August 29, 2014
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Enlarging plant factory increases the risk of inhomogeneous distribution and fluctuation in temperature. This is why a research about quantification of the effect of temperature fluctuation is required focusing on high temperature-sensitivity of plant. In this study we quantified temperature-sensitivity of lettuce in the germination using synchronization index of circadian rhythms as an index. We used transgenic Greenwave lettuce (
AtCCA1 :LUC) and analyzed the synchronization rate of circadian rhythms among individuals by measuring circadian rhythm of the lettuce in germination. It was revealed that circadian rhythms synchronized among individuals by temperature changes with diurnal fluctuation and rapidly decreasing. These results indicate that plant circadian clock has high temperature-sensitivity. Therefore plant factory is required accurate temperature control when we perform monitoring and selection of seedling based on measurement of circadian clock.
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Chiho MYOJIN, Ken OHFUSA, Satoshi AWATA, Touichi Ogura, Shinichi KIN ...
2014 Volume 31 Issue 3 Pages
367-373
Published: September 30, 2014
Released on J-STAGE: September 30, 2015
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In this study, antioxidant activity and deliciousness of frill-lettuce produced in plant factory of Osaka Prefecture University and their changes during cold storage were analyzed. Frill-lettuce produced in the plant factory, sunlight-lettuce and head lettuce were stored at 4
℃ for 4 days. The time-dependent changes in DPPH radical scavenging activity, ORAC, total polyphenol and ascorbic acid content were analyzed. The lettuce produced in the plant factory showed significantly high antioxidant activity. DPPH radical scavenging activity and total polyphenol in the plant factory-produced lettuce significantly increased during 4 days storage (p<0.05,p<0.01), but ascorbic acid content significantly decreased during storage (p<0.01).
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