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Volume 37, Issue 3
Displaying 1-11 of 11 articles from this issue
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1. A Steady State Analysis by Means of One Dimensional ModelsTadashi TAKAKURA, Kenichi YAMAKAWA1981 Volume 37 Issue 3 Pages 187-196
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA simple steady-state and one-dimensional model has been developed in order to analyse the performance of a greenhouse solar collection with underground heat storage system which is being predominantly adopted in Japanese protected cultivation. The objective of this system is to store solar heat during the daytime by circulating the warm greenhouse air through the pipes buried in the greenhouse soil, and to gain heat from the soil through the pipes during the nighttime.
However, the problem is that the frequent attack of energy crisis on Japanese protected cultivation has forced the farmers to adopt this system without any quantitative analysis. Of course, some experimental results are available but theoretical analysis has not been conducted as far as the authors know.
The purpose of the present study is, therefore, to check the performance of the system as well as to evaluate the parameters involved in the system. The effectiveness of the temperature increase in the greenhouse is found to be evaluated by the ratio of the overall heat transfer coefficient around pipes times the total pipe surface area plus the overall heat transfer coefficient through the greenhouse soil surface times the greenhouse floor surface area to the overall heat transfer coefficient at the greenhouse cover times the greenhouse surface area (see Fig. 3). It is also apparent from this ratio that the heat release from the greenhouse soil surface is rather significant in this system and in general it would be 20-30% of the heat gain through the buried pipes.
The effect of the material difference of the pipes has been examined and it is concluded that the effect on the greenhouse air temperature is within 0.2°C among PVC, polyethylene and steel (Table 3). From the evaluation of the pipe dimensions, it is concluded that the difference of thickness is not significant and the optimum diameter is 11cm as far as the greenhouse air temperature is concerned (Table 4).
In order to select an adequate fan for the system, the friction loss due to the plenum duct made of concrete can not be neglected. It is found that the adoption of smooth ducts could reduce the friction loss of this part significantly and the consumption of electricity, consequently the greenhouse air temperature is increased (Fig. 4). The same tendency is clear in the case of two way air flow direction system against one way (Fig. 5).View full abstractDownload PDF (1099K) -
(3) Horizontal and Vertical Turbulent Characteristics Influenced by Two Kinds of Windbreak Nets in a Paddy Rice FieldTaichi MAKI1981 Volume 37 Issue 3 Pages 197-210
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe horizontal variations and vertical profiles of various turbulent characteristics for two kinds of windbreak nets were obtained by the use of an ultrasonic anemometer from -20H windward (distance expressed as a multiple of the net height, H=2m, and negative signal denoting the windward) to 40H leeward at 50 to 250cm heights in the paddy rice field.
The turbulent intensity increased slightly at an immediate windward from the net (-0.25H), took respectively the minimum and the maximum around an immediate leeward (1 to 2H) and at 10H, and gradually decreased for farther distances. The magnitude of turbulent intensity in the leeward for the net was much smaller than that for the pine windbreak forest and other fences, which expresses the characteristic of the net. The horizontal variation of the dissipation rate of turbulent energy was similar to that of turbulent intensity. However, the largest and smallest eddies, the characteristic time scales of autocorrelation coefficients and their ratios were almost contrary in relation to turbulent intensity. The turbulent characteristics at a height of 100cm returned to the windward ones by 30H for cheese cloth net and by 20 to 25H for polyethylene russell net, but at a height of 50cm the recovery took longer distances.
The vertical profiles of turbulent characteristics were generally smooth at -20H, but rather irregular at 2 and 5H. This paper made clear the turbulent characteristics of air flow over the net at a height of 250cm at 2 and 5H, of the wind passed through the net at heights of 100 and 150cm, and of the upward wind passed through the open space under the net at a 50cm height at 2H. The turbulent intensity and energy dissipation rate were larger at the upper levels, but the largest and smallest eddies, and the characteristic time scales of autocorrelation and their ratios became smaller at those levels.View full abstractDownload PDF (1849K) -
(2) Heat Transmission in the Greenhouse with Pipe Heating SystemsMasumi OKADA, Tadashi TAKAKURA1981 Volume 37 Issue 3 Pages 211-219
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe heat transmission through greenhouse cover surface relates to the position of heating pipes. This paper describes quantitatively this relationship. The experiment has been conducted to understand the common behavior of heat transfer at the inside cover surface of a greenhouse. The results show predominance of radiative heat transfer from pipe surface to glass surface in the crop free greenhouse. Parameters to determine the radiative heat transfer from a pipe such as the view factor and the surface emissivity are estimated to have an effect on the total heat consumption. To evaluate their effects an analytical approach based on energy balance has been developed. The calculations exhibit that the piled pipes positioned by the greenhouse side wall increase both radiative and convective heat fluxes at the inside glass surface in comparison with the lower pipes positioned under crops. For piled pipes a 15-30% larger value of the heat transmission coefficient depending on the surface emissivity is observed than for low pipes under crops. The lower emissivity of pipe surface is predicted to minimize the contribution of radiation exchange between pipes and glass to heat transmission for each position of a pipe.View full abstractDownload PDF (936K) -
1981 Volume 37 Issue 3 Pages 220-220,238
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
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Masumi OKADA1981 Volume 37 Issue 3 Pages 221-230
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA steady one-dimensional heat flow model was developed to determine the thermal effectiveness of internal curtains in unheated greenhouses. The model consisted of only sensible heat balance, but it included convective and conductive heat transfer from soil to outside air as well as radiation balance on external covering and internal curtains. Using this model the temperature regime in an unheated greenhouse was predicted. The results showed the large dependence of the temperature regime on radiative characteristics of curtains.
As a measure of thermal effectiveness in an unheated greenhouse, the k-value, a percentage ratio of the inside minus outside air temperature difference to the soil minus outside air temperature difference, was introduced and used for comparison.
In the case of a single curtain a use of the upper-side reflective curtain (URC) exhibited the highest k-value which increased as the reflectivity increased. With the reflectivity being more than 0.6, the k-value became remarkably large. When the same curtain was placed upside down (lower-side reflective curtain), the k-value decreased as low as the emissive or transmissive curtain even if its reflectivity was high. Both-side reflective curtain (BRC) showed a slightly smaller k-value than URC, but it caused the least heat loss. This suggests that there is little difference in the thermal effectiveness between URC and BRC.
In the case of double curtains the combination of BRC at an upper position and URC at a lower position produced the largest k-value. Nearly the same value was also obtained in the combination of BRC at an upper position and the high emissive curtain such as PVC at a lower position. From economic and cultural points of view, the latter combination can be recommended. When increasing the number of curtain layers from single to triple, a linear increase of the k-value was observed for the emissive or transmissive curtains. For the high reflective curtains, however, the difference in the k-value between double and triple layers was not significant.
At the reflective surface of a curtain a smaller value of convective heat transfer coefficient was predicted to improve to a certain degree the thermal effectiveness, but not at the emissive or transmissive surface.View full abstractDownload PDF (1326K) -
(II) Effect of Mist Treatment on Dry Matter Production on Sunny DaysKazuyoshi KIMURA, Shigemi TANAKAMARU1981 Volume 37 Issue 3 Pages 231-237
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe effect of mist treatment on dry matter production in some crop leaves was investigated on sunny days in the greenhouse and in the phytotron. Kidney bean (Phaseolus vulgaris L.), pea (Pisum sativus L.), soybean (Glycine max Merr.), sweet potato (Ipoemea batatas Lam.), Chinese mustard (Brassica chinensis L.) and maize (Zea mays L.) were used as the materials. The rate of dry matter production was measured by using the improved half-leaf method. The results were as follows:
1) On sunny days, water mist treatment decreased the rate of dry matter accumulation in these crop leaves in the greenhouse. The rates under mist treatment were about 50% of those under no mist condition in soybean, Chinese mustard and maize leaves, and 70-80% in pea, kidney bean and sweet potato leaves (Figs. 1 and 3).
2) Deionized water mist treatment also decreased the rate of dry matter accumulation of maize leaves in the phytotron (Fig. 4).
3) In maize leaves, the ratio of accumulation rate under mist to that under no mist decreased with increasing solar radiation from 133W/m2 to 465W/m2 (Table 1). This tends to show that the greatest decrease of dry matter accumulation occurred at the highest intensity of radiation.
4) The inhibitory effect of mist on dry matter accumulation differed with the ratio of stomata number on the upper surface of leaves to that on the lower surface. The accumulation of leaves with the higher ratio was more strongly inhibited than that with the lower ratio.
5) In the greenhouse on sunny days, mist treatment decreased air- and leaf-temperatures markedly (Table 2 and Fig. 2). Under mist condition, the leaf temperatures showed somewhat higher values than the air temperatures. Differences between the air and leaf temperatures were larger under mist condition than under no mist condition.View full abstractDownload PDF (854K) -
Part 1. Strong Wind Damage of Roadside Trees by the Typhoon 7920 in SapporoHidenori TAKAHASHI, Hiroshi TANI1981 Volume 37 Issue 3 Pages 239-243
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
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Shin'ichi KOTAKA, Nobuyuki ABE1981 Volume 37 Issue 3 Pages 245-248
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (436K) -
Ritsuo MURAKAMI1981 Volume 37 Issue 3 Pages 249-253
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (620K) -
Nobuteru Tani1981 Volume 37 Issue 3 Pages 255-256
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (286K) -
Tetsuo Sekiyama1981 Volume 37 Issue 3 Pages 257-259
Published: December 10, 1981
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (1615K)
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