Обеспечение температурного режима в культивационных сооружениях
Аннотация
The purpose of this Research Work is to assess the effect of plant life on the required microclimate parameters in the greenhouse and on the heat flows needed to ensure them in the building.
Often, design engineers do not take into account the vital activity of plants during calculating heat losses of cultivation facilities, counting them according to the standard engineering methodology for calculating heat losses. As a result, the actual values of thermal losses of greenhouses are underestimated. In the issue, during the operation of such objects, the temperature of the internal air is below the optimum temperature, which negatively affects the growth of plants.
Due to the literature sources lack, one of the objectives of this work was to find a real functioning object, on the basis of which analysis could be carried out. The object of research is the greenhouse block № 3 in The Greenhouse Complex with a production area about 12 ha in the village of Sadovy, Ordzhonikidze District, Ekaterinburg.
In this work, the following tasks were set:
• calculate the capacity of the heating system of the greenhouse taking into account the equations of heat and mass transfer on the surfaces of soil, plants and covering constructions to maintain the optimum temperature inside the structure;
• calculate the capacity of the heating system of the greenhouse, taking into account heat fluxes only on the covering constructions and soil;
• calculate the capacity of the heating system of the greenhouse, taking into account only transmission heat losses;
• analyze the calculation results.
The master's thesis includes: an explanatory note on 76 pages, 3 tables, 21 figures, 20 titles of the bibliographic list, a presentation of 22 slides.
The first chapter describes the existing types of cultivation structures, their structural and technological characteristics and types of enclosing structures. The vital activity of plants, the external factors influencing it, and the microclimate of greenhouses are considered. The heat balance for greenhouses, in general, is presented.
The second chapter describes the object of study and its engineering and technological systems. The heat flows on the leaf surface in various zones are considered. The thermal balance of the greenhouse was compiled for the night regime of the structure.
In the third chapter, the power of the heating system is calculated taking into account and without taking into account the vital activity of plants and taking into account only transmission heat losses.
For this, the thermal engineering calculation of the external covering constructions was carried out, the temperatures on the inner surface of the covering constructions were determined. The heat flows by convection and radiation, heat flows characterizing the release of heat during steam condensation on the inner surfaces of the covering constructions and the heat consumption for the evaporation of moisture from the soil and plants are considered. Heat losses through the soil mass and infiltration are calculated.
Based on the results of the calculations, the following conclusions are made:
1. The calculated heat loss, taking into account the vital activity of plants, is 17.4 MW, excluding plants - 16.9 MW, while the value of transmission heat loss is 15.9 MW.
2. During the operation of greenhouses, the heat losses of which were calculated without taking into account the vital activity of plants or according to standard engineering methods, the temperature of the internal air drops below optimal temperatures and is equal to 13.7°C and 11.2°C, respectively, which negatively affects the growth of plants.
3. The calculation of heat loss taking into account the vital activity of plants establishes an analytical relationship between the required parameters microclimate in the greenhouse and the heat fluxes necessary for their provision in the structure, therefore they must be taken into account when calculating and further designing.
Often, design engineers do not take into account the vital activity of plants during calculating heat losses of cultivation facilities, counting them according to the standard engineering methodology for calculating heat losses. As a result, the actual values of thermal losses of greenhouses are underestimated. In the issue, during the operation of such objects, the temperature of the internal air is below the optimum temperature, which negatively affects the growth of plants.
Due to the literature sources lack, one of the objectives of this work was to find a real functioning object, on the basis of which analysis could be carried out. The object of research is the greenhouse block № 3 in The Greenhouse Complex with a production area about 12 ha in the village of Sadovy, Ordzhonikidze District, Ekaterinburg.
In this work, the following tasks were set:
• calculate the capacity of the heating system of the greenhouse taking into account the equations of heat and mass transfer on the surfaces of soil, plants and covering constructions to maintain the optimum temperature inside the structure;
• calculate the capacity of the heating system of the greenhouse, taking into account heat fluxes only on the covering constructions and soil;
• calculate the capacity of the heating system of the greenhouse, taking into account only transmission heat losses;
• analyze the calculation results.
The master's thesis includes: an explanatory note on 76 pages, 3 tables, 21 figures, 20 titles of the bibliographic list, a presentation of 22 slides.
The first chapter describes the existing types of cultivation structures, their structural and technological characteristics and types of enclosing structures. The vital activity of plants, the external factors influencing it, and the microclimate of greenhouses are considered. The heat balance for greenhouses, in general, is presented.
The second chapter describes the object of study and its engineering and technological systems. The heat flows on the leaf surface in various zones are considered. The thermal balance of the greenhouse was compiled for the night regime of the structure.
In the third chapter, the power of the heating system is calculated taking into account and without taking into account the vital activity of plants and taking into account only transmission heat losses.
For this, the thermal engineering calculation of the external covering constructions was carried out, the temperatures on the inner surface of the covering constructions were determined. The heat flows by convection and radiation, heat flows characterizing the release of heat during steam condensation on the inner surfaces of the covering constructions and the heat consumption for the evaporation of moisture from the soil and plants are considered. Heat losses through the soil mass and infiltration are calculated.
Based on the results of the calculations, the following conclusions are made:
1. The calculated heat loss, taking into account the vital activity of plants, is 17.4 MW, excluding plants - 16.9 MW, while the value of transmission heat loss is 15.9 MW.
2. During the operation of greenhouses, the heat losses of which were calculated without taking into account the vital activity of plants or according to standard engineering methods, the temperature of the internal air drops below optimal temperatures and is equal to 13.7°C and 11.2°C, respectively, which negatively affects the growth of plants.
3. The calculation of heat loss taking into account the vital activity of plants establishes an analytical relationship between the required parameters microclimate in the greenhouse and the heat fluxes necessary for their provision in the structure, therefore they must be taken into account when calculating and further designing.