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Volume 21 (1990 - 199･･･
- Issue 3 Pages 149-
- Issue 2 Pages 79-
- Issue 1 Pages 7-
Volume 21, Issue 2
Displaying 1-3 of 3 articles from this issue
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Transmissivity of Solar Radiation, Air Change Rate and Heat Loss CoefficientQingyun CHEN, Yoshiyasu AIHARA, Masumi OKADA, Yui HUANG1990 Volume 21 Issue 2 Pages 79-84
Published: November 30, 1990
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSTransmissivities of solar radiation, air change rates and heat loss coefficients of five types of row covers were measured. Transmissivities of solar radiation were almost the same within 0-40° of incident angle, but dropped over 40°. Airchange rates were linearly increased with increase of porosities of row covers. Heat loss coefficients were increased with an exponential function of wind speed as well as porosities.View full abstractDownload PDF (612K) -
Takahisa MATSUOKA1990 Volume 21 Issue 2 Pages 85-93
Published: November 30, 1990
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSThe relation between the heating-radiating characteristics of a far-infrared radiation heateruand the drying characteristics of rough rice was investigated to establish basic data requied for utilization of far-infrared rays for the drying of rough rice. The following results were obtained.
(1) The ratio of radiating energy from the heater to input energy into the heater increases with an increase in surface temperature of the heater.
(2) The total emissivity of the heater is not affected by the surface temperature of the heater.
(3) The far-infrared radiation heater has a higher heating efficiency compared to a sheath heater. However, the thermal radiation is not almost transmitted into solid bodys.
(4) Far-infrared radiation heating is more effective when the distance between heating material and the heat source is shorter.
(5) In heating of rough rice by far-infrared radiation heating, approximately 400[°C] was estimated to be an appropriate surface temperature of the heater as evaluated from the aspects of the monochromatic absorptivity of rough rice and the efficiency of radiating energy from the heat source.
(6) The drying constant of rough rice in far-infrared radiation heating is expressed by the equation of Arrhenius as suggested by existing data on heated-air drying. It was also found that the higher the temperature is, the more the effect of radiation increases and the larger the drying constant of rough rice becomes rapidly.View full abstractDownload PDF (1019K) -
Drying Efficiency and Effect of GreenhouseShoji TAHARAZAKO, Kazuo MORITA, Chang La WEI, Sumio HAYASHI1990 Volume 21 Issue 2 Pages 95-101
Published: November 30, 1990
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSIn order to develop a circulatory dehumidifying drying system in the greenhouse, some fundamental drying characteristics of radish were investigated. The results are summarized as follows:
(1) The time required to reduce the moisture content of the radish from 94.0%w.b. to 9.3%w.b. was observed to be 67 hours and the average drying rate was 1.46%w.b./h. On comparing the experiment in the greenhouse to that of the indoors, the drying time inside the greenhouse was 30 hours shorter, and the drying rate was 1.8 times faster than the indoors.
(2) The average temperature of air in the greenhouse was higher by 11.5°C and 4.0°C in the day and night time respectively, as compared to the average temperature of the open air. The rise of the temperature by solar energy inside the greenhouse could be utilized for radish drying.
(3) The relative humidity of air inside the greenhouse was initially about 100%, but it was reduced finally up to 56%. The relative humidity of dehumidifying drying air was reduced from initial 78% to 30% at the final stage. The average relative humidity of dehumidifying drying air was 18% lower than that of air in the greenhouse.
(4) When the air temperature in the greenhouse was dropped bellow 5°C, the evaporator of heat pump dehumidifier began to be frosted. Therefore, it would be essential to discuss about effective measures inorder to improve the dehumidifying device.
(5) The consumption of electric power was 19kWh (6.9kWh at heat pump dehumidifier and 12.1kWh at fan) per kg of dehydrated radish. It was fixed at 380 yen in terms of the drying cost.View full abstractDownload PDF (3958K)
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