Fundamental analyses and some experiments regarding to water-vapor transfer by foced convection over a wetted leaf-shaped plane surface were made.
In general, for a leaf-shaped plate, local water-vapor transfer coefficient (D_x) which is a function of wind velocity (u) and distance (x) over the surface from the leading edge in the direction of air-flow is written as follows:
D_x=Bu^m₂x^-n₂,
where, B is a numerical coefficient affected by the shape of the plate, its relative position to wind, natures of air-flow and the boundary-layer, the vapor-concentration distribution over the surface, properties of air and so on; m₁ and n₁ are exponents related to the structure of the boundary-layer, respectively.
Water-vapor concentration departure (ΔC_x) of the surface from the air outside the boundary-layer is generally expressed as follows;
ΔC_x=C_o+bu-^m₂x^n₂,
where, b is a numerical coefficient and C_o is a constant. When the temperature of the leading edge of the plate is identical to the air temperature, C_o is the saturation deficit of air in vapor-concentration.
A local evaporation-rate is obtained as the product of the local values of vapor transfer coefficient and vapor-concentration departure.
Then, the relationships between a local and the average values of transfer coefficient, concentration departure and evaporation-rate were theoretically analysed and the effect of the surface-temperature distribution in the air-flow direction upon the convection vapor transfer coefficients was experimentally examined.
I. For the plane-surface with the above described transfer coefficient and the distribution of vapor-concentration departure, each correction factor for obtaining the average value of transfer coefficient, concentration departure or evaporation-rate from each local value was calculated. These results are shown in figures (Figs. 1, 2-A and 3). For example, the correction factor of vapor transfer coefficient at the point where the distance from the leading edge in the air-flow direction is 40% of the surface dimension are 1.26 and 1.04 for laminar and turbulent boundary-layer, respectively.
Further, the positions where a local value coincided with the average value for each quantity were derived. The distance of the position where a local vapor-concentration departure agrees with its average is about 40% of the surface dimension from the leading edge in the flow direction.
The position for evaporation-rate is complicated as it is related to air-temperature, humidity, wind velocity, surface dimension and temperature departure of the surface from air. However, under moderate air conditions local evaporation-rates at positions whose distance from the leading edge being between about 26 and 30% of the surface-dimension in the flow direction agrees with the average rate for a flat leaf.
II. Three representations of average evaporation-rate were shown in the cases of using (i) both local values of transfer coefficient and vapor-concentration departure, (ii) the average transfer coefficient and a local concentration departure, (iii) both average values of transfer coefficient and concentration departure.

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In order to estimate the magnitude of air infiltration of glass-covered greenhouses, an equation is derived as a function of outside wind speed and the temperature difference between inside and outside air. Two constants involved in this equation are determined from experimental data and the application of this equation to the other greenhouse is verified experimentally. Heat loss due to infiltration is also evaluated considering not only the sensible heat transfer but also the latent heat transfer. It is also shown that the latent heat transfer portion is significantly large.

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Fog and fan method, a new evaporative cooling method of greenhouse has been developed.
For evaporative cooling, not only the volume of water to evaporate but also the voiume of fresh air wihch is taken into the greenhouse is one of the most important factors to be consdered. In pad and fan method, water spray and resulting evaporation are occured at the pad installed at the greenhouse wall which forms a large resistance for the air flow through the pad. In the present method, fine water droplets are sprayed in the greenhouse directly and evaporation takes place simultaneously in the greenhouse. Therefore, there is no resistance for intake air flow and a fan with considerably smaller capacity will be able to produce the same flow rate. Furthermore, horizontal variation of air temperature will be smaller.
In the present method, droplets must de small enough to evaporate completely before they reach the floor, when nozzles are arranged at 3m height dry bulb temperature is 30.0°C and relative humidity is 80% in the greenhouse, droplets whose diameters are smaller than 88 microns can evaporate completely before they reach the floor. In order to generate fine droplets, the authors developed a new impaction nozzle. This nozzle is made of plastics and designed to be used at rather high pressures, 5-20kg/cm².
The generated droplet diameter becomes smaller as the pressure increases and a mode of diameter distribution exists in the range between 30 and 40 microns at the pressure of 10kg/cm². Relative frequency of droplet diameters at three different pressures is shown in Fig. 2.
A field experiment has been conducted using a seven-spanned greenhouse (49×42). Air space under the single span of the east end is separated by the polyethylene film from the other and is installed by 30 nozzles and 2 fans. The other is installed by six pairs of pad and fan system, although their capacities are too small to cool the rest greenhouse space. Results of cooling are shown in Figs. 4, 5 and 6. Air temperature in the fog and fan compartment is always lower than the outside air temperature, and is lower about 5°C than that of pad and fan compartment at noon. The horizontal variation of air temperature in the fog and fan compartment is within 1.1°C. It is remarkably small comparing with that of pad and fan compartment. Total volume of sprayed water is 3.0kg/min, and the floor area of the compartment is 280m². Then, the volume of sprayed water per unit floor area is 10.7g/m²min.
This fog and fan system can be installed easily and inexpensively at conventional greenhouses.

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A series of experiment was carried out to clarify the heating effect of a solid-fuel heater which has been developed for cold protection of citrus trees. The results obtained are as follows:
1) The heater is formed into a brick and its size is 8cm in width, 20cm in length, 12cm in height and 1.5kg in weight. They burn for approximately six to eight hours.
2) The air temperature rise of heated over unheated trees near the central part in canopy of Satsuma orange increases in proportion to the amount of combustion per ha as shown in following table:
The amount of combustion Temperature rise
(No. of heater per tree)
1, 500kg/ha (1-2) 0.5°C
1, 900 (2-3) 1.0
2, 800 (3-4) 2.0
3, 700 (4-5) 3.0
3) The temperature rise occured by burning the solid-fuel heaters is 1.6 to 4 times as great as compared with the return stack heater on the conditions that both heaters give off the same heat per ha.
4) The canopy and size of the tree has an effect on tthe heater performance. The tighter anp larger the canopy the more efficient the heaters are.
5) The concentrations of sulfurous anhydride and carbon monoxide contained in the combustion gas from the solid-fuel heater are 0.01 to 0.05ppm and 0.06 to 0.08%, respectively.
6) Distributing the solid-fuel heaters in the glove requires thrice as much time as supplying of oil to the return stack heaters per ha. The labor requirement for lighting the solid-fuel heaters takes 9 times as long as compared with the return stack heater.

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