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関, 平和 ; 小森, 友明
概要:
For the purpose of utilization of heat generated in composting process to the protected cultivation as a supplementary energy source for agriculture, the mechanism of heat transfer in composting process of mixed organic materials
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mainly consist of livestock wastes and farmyard wastes was investigated and the rate of heat generation within a compost bed was estimated based on the experimental results of composting process performed in a styrofoam container. Main results obtained in this paper were as follows. 1) The method for estimation of the rate of heat generation presented here would be convenient to investigate physically the mechanism of heat transfer in a compost bed. 2) In these experiments, it has become known that heat was generated almost in the aerobic region between the surface of the compost bed contacting to the atmosphere and the position 0.4m below the surface, and that the average value of the apparent rate of heat generation in the above region would be about 200kcal/m3hr and the true value of the rate of heat generation would be 300kcal/m3hr. 3) Oxygen concentration distributions in the gaseous phase of the compost bed were estimated, and it was shown that the aerobic region would be varied with the dry density (or the porosity) and the volumetric air content (or the volumetric moisture content) of the compost bed. Hereafter, it will be needed to investigate the availability of the above stated method in detail by relating to the amount of consumption of the substrate.
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| 2.
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関, 平和 ; 小森, 友明
概要:
Having had imagined the heat recovery from exhaust air out of a compost bed, experiments for rising the temperature of w
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ater (medium fluid) by a packed column heating tower of counter flow-type were conducted. There was a considerably larger temperature rise of water (30°C of the maximun), and a higher value of the heat recovery efficiency (72% in average), as compared with those for the buried-tube-type heat extractor. Therefore, the proposed heat recovery system seemed likely to be valid. An overall volumetric coefficient of enthalpy transfer of the tower Ka depended only on the mass velocity of dry air G, and it was arranged by the experimental equation Ka=27G0.76 within the error of±20%. Assuming the linearity between the enthalpy and temperature of saturated air, approximate solutions of the temperature of water and the enthalpy of moist air in the tower were derived. It was illustrated that the volume of compost bed and the mass velocity of water in the tower which would be required to get the desired water temperature at the outlet of the tower could be graphically determined by the approximate solutions.
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| 3.
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関, 平和
概要:
Targeting resource management and the effective utilization of waste of plant origin, experiments involving NO (nitrogen monoxide) adsorption by charcoal filter were conducted. The charcoal filter used is made from driftwood into dams
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and from waste lumber. According to the experimental results, the amount of equilibrium NO adsorption of the charcoal filter was 40-1300 times as much as that of the soil filter used in the previous paper. Based on the experimental results of the NO breakthrough curve from the charcoal filter and the theoretical analysis of the mass transfer process, the NO adsorption characteristics of the charcoal filter were recognized. It was experimentally and theoretically shown that the fundamental main mechanism of the adsorption by the charcoal filter is the surface diffusion into the micro-pores except in the short early stage, during which the Knudsen diffusion in the meso-pores is the main mechanism. A practical equation that properly shows the stepwise change in the adsorption rate was proposed, and the physical meaning of parameters in the equation was explained through interpretation of the adsorption mechanism. The adsorption ability would differ based on the kind of materials involved, and that was left for future work examining the details of the charcoal filter structures.
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| 4.
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関, 平和 ; 小森, 友明
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| 5.
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小森, 友明 ; 関, 平和
概要:
Heating and thermal insulation characteristics of a falling hot water film on the roof or the screen sheet of a greenhou
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se may be analysed by evaluating the temperature profile of the thin water film. The temperature profile of the falling water film can be obtained by solving the conduction equation with several suitable boundary conditions, based on the concept of “Transfer and Rate of Processes”. The generalized analytical solution of the temperature profile of the water film was given by Eq. (15) and the average temperature at an arbitrary distance along the direction of water flow, ζ=ζ was given by Eq. (18). From the calculated results of illustrative examples by the analytical solutions, the temperature of the water film at the water film-roof interface, ξ=1 could be approximated by the average temperature of the water film, an effective distance for heating the air in the greenhouse, ζR was determined from the relation between Φav(ζ) and the dimensionless temperature of the greenhouse ΦR and the most suitable thickness of the water film δ could be estimated by plotting Φav (1) against δ with a parameter ΦR, as shown in Fig. 6. The relationship between Φav(1) and δ in Fig. 6 will be also applicable to estimate the suitable flow rate of water. According to the calculated results, the water film performs broadly the task of thermal insulation at the water-roof interface. The corresponding amount of heat to the thermal insulation effect of the water film was given by Eq. (21), theoretically. Figs. 10, 11 and 12 show the over-all heat balance of the water film obtained by Eq. (21) and the amount of heat calculated from Eq. (21) is evaluated quantitatively by the rate of reduction of heating load for heating the greenhouse. Therefore, the analytical solutions and procedures described here are useful for the calculation of actual heat requirement for heating a greenhouse, the design and operations of the practical water curtain system.
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| 6.
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関, 平和 ; 小森, 友明
概要:
A theoretical analysis of an operation of extraction and accumulation of the heat generated in composting process by water circulation was made. The calculated results of the average temperature in a compost bed and the water
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temperature in an accumulator were compared with the experimental results obtained previously. 1) For the case of the intermittent water-circulation, there were slight differences between the calculated results and the experimental results of the average temperature in the bed during temperature recovering periods after the end of water-circulation. However, the calculated results of the water temperature in the accumulator, the available time for heat extraction and the recovery time of temperature in the bed agreed relatively well with the experimental results. The theoretical model was fairly fit for this case. 2) For the case of the continuous water-circulation, the calculated results of the average temperature in the bed were in fair agreement with the experimental results. The calculated results of the water temperature in the accumulator were however 3 to 7 degrees higher than the experimental results. It could be due to the heat loss through the pipes connecting the container for the compost with the accumulator, which was not allowed for in the theoretical model. It is necessary to modify the analytical model by taking account of this kind of heat loss.
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| 7.
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関, 平和 ; 木村, 達郎 ; 宮本, 暁人 ; 菅谷, 博 ; 佐々木, 華織 ; 猪之奥, 康治
概要:
A mathematical model was developed for predicting air temperature, humidity and velocity fields in a closed-type sloped greenhouse. Calculated results of air temperature profile along the slope agreed well with the experimental results
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except in the daytime when the air temperature was high, and it seemed that the model would be useful for environment analysis in the sloped greenhouse. This model would be better if three-dimensional heat flow had been taken into account in the daytime. Both the calculated and experimental results showed that air temperature was higher in the upper part of the slope than that in the lower part for the greenhouse with a double-film-cover. For the greenhouse with a single-film-cover, however, air temperature in the upper part was not necessarily higher than that in the lower part especially in the nighttime. Provided that floor and cover temperatures were uniform, respectively, air temperature and velocity fields were simulated. The simulated results showed an appearance of air temperature difference between the upper and lower parts. Both the higher and lower temperature regions extend as inclined angle increases. However, this temperature difference between the upper and lower parts in the case of 10 degrees of inclined angle is not so different from that in the case of 30 degrees. In addition, an increase in the inclined angle makes air velocity larger, so that its increase over a certain critical value inhibits the development of air temperature difference between the upper and lower parts rather than promotes it.
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| 8.
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関, 平和 ; 奥村, 綱雄
概要:
In this paper, NO (nitrogen monooxide) adsorption ability of a soil filter was considered both experimentally and theore
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tically as the first step in developing a new nitrogen recovery system using the soil filter and plants. In this proposed system, a gas component NO that is discharged from fixed sources such as incineration plants will be trapped by a soil filter and transformed into NO3-, and then absorbed by the plants. At first, by comparing the O2 breakthrough curve obtained experimentally with that calculated from the analytical solution of O2 concentration, the apparent gas diffusivity in the soil filter was obtained. Next, assuming that the rate of adsorption follows a linear driving force (LDF) model, two parameters a (equilibrium constant) and Θ (time constant) of the LDF model were evaluated for each experiment, and a solution of NO concentration was numerically derived. The validity of the solution was proved by comparing the NO breakthrough curve obtained experimentally with that calculated numerically. The value of Θ greatly differs according to soil texture, and the value of a is large under moderate moisture content conditions. Since the adsorption ability of the soil filter is small, however, it seems insufficient to use the soil alone as a filter to trap NO from fixed sources.
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| 9.
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小森, 友明 ; 関, 平和
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| 10.
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関, 平和 ; 小森, 友明
概要:
Several experiments for heat generation in composting process with livestock and farmyard wastes had been made by using a compost container in laboratory scale. Following the previously proposed procedure for estimation, the apparent rate of
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heat generation was calculated by applying the observed value of temperature in a compost bed to the analytical solution of temperature derived from a three dimensional model for heat conduction problem. The true (or total) rate of heat generation was also calculated by adding the latent heat loss due to vaporization of water to the apparent rate of heat generation. The following results were obtained. 1) Since the initial moisture content was relatively small, the increasing rate of temperature became large and the attainable maximum temperature was high in the early stage of the composting process. Because of the leakage of heat from the side walls of the compost container to the atmosphere, however, temperature decreased within a comparatively short period. 2) During the composting process, the effective region of heat generation moved gradually downward from the surface of the compost bed, so that the apparent rate of heat generation was varied remarkably with both the time and the vertical location in the compost bed. 3) As for some results of the experiments used relatively large contents of rice bran and chicken manure (Runs 3, 4), the steady high-temperature period became longer and the local maximum value of the apparent rate of heat generation was larger than the results of the other experiments (Runs 1, 2). Even in the latter experiments, in the limited region of the effective duration of heat generation, the average value of the apparent rate of heat generation in the compost bed was approximately 150kcal/m3hr, and this value was not so different from the results of the former experiments. 4) The above-mentioned results on the average value of the apparent rate of heat generation were also similar to the results of the previous experiments under the considerably larger moisture conditions. As for a natural composting process, the average of the apparent rate of heat generation in the effective region of heat generation seemed to be almost independent of the moisture content and to fall within the range from 150 to 200kcal/m3hr. 5) The calculated results of the true (or total) rate of heat generation agreed well with the values estimated from the consumption rate of carbon in the compost bed, and were almost equal to the results which had been obtained previously.
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