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An increasing in world population and climate changes including increasing the import of agricultural products in some countries as well resulted in increased demand for food and quality. Therefore, growing plants inside the greenhouse becomes increasing popular. The main advantages are high-energy efficiency of greenhouse and high-quality products. One key target to achieve the high-energy efficiency and product quality is the ability to control environmental conditions inside greenhouse. In all of the reviewed greenhouse, weather control system is air-conditioners. However, if the greenhouse space is huge, there is a great demand for air conditioner systems. Therefore, novel techniques that can control air temperature and reduce energy consumption are interesting. This research focused on microclimate weather control system for plantation. This aim to create suitable microclimate just around each plant while surrounding space inside greenhouse may have different weather conditions. Since the volume of the air to be controlled is smaller, both air conditioner system and energy consumption will be reduced.The first objective was to study and research an energy analysis of an experimental greenhouse and determine how to control environmental conditions around plantation. Under this objective, a field experiment was performed in a small walk-in tunnel with a passive solar greenhouse for strawberry cultivation in a temperate area in central Japan. The energy required to maintain the optimum temperature for strawberry growth in the greenhouse was calculated. Furthermore, the impact of environmental factors on the strawberries was evaluated. The findings showed that the greenhouse can provide favorable environmental conditions for strawberry plants. Generally, supplemental heating is not required during the daytime because solar radiation is sufficient to maintain the temperature inside the greenhouse high enough for strawberry cultivation even in winter. The measured weather data indicated that the inside temperature was rather low during nighttime in winter; therefore, the use of a heating system is recommended during in this period. The calculated maximum heating requirement was from November 2020 to April 2021. The heat energy requirement was found to be maximum in January (327.6 MJ/m²⋅month and 281.9 MJ/m²⋅month when T dℯ= 10 and 8 °C, respectively). A 2°C reduction in heating temperature could reduce energy demand by up to 31%. The difference in air temperature between day and night may improve the sweetness and weight of strawberries.The second objective was to control the local air temperature around plantation area. Under this objective, a cooling serpentine copper pipe heat exchanger is established for cooling in a laboratory-scale room. The experiments were carried out under various operating conditions, in which the inlet water temperature, water volume flow rate, and heat transfer surface area were controlled. Following the second objective, the last objective was to investigate the thermal performance and local air temperature distributions around a cooling serpentine copper pipe heat exchanger. The local air temperatures above and below the serpentine panel as well as the relative humidity were measured. Local air temperature contour graphs were also presented. The calculation and measurements showed that a cooling serpentine copper pipe heat exchanger can reduce local air temperatures. When room air temperature was 25°C, local air temperature was lower than room air temperature approximately 5 to 9°C under different inlet water temperatures and water flow rates. Based on the results, it can be seen that the temperature of inlet water and volume flow rate greatly influenced on total heat flux, condensation heat transfer and convective heat transfer. Increasing water volume flow rate and reducing inlet water temperature led to increase in rate of heat transfer. In addition, heat transfer rate is directly proportional to the inlet water temperature and heat transfer rate is related with droplets size, number of droplets as well as film thickness. Thermal resistance increases with increasing film thickness and number of droplets on copper pipe. Condensation or the frozen ice around copper pipe could increase the reduction in local air temperature and increase rate of heat transfer. In conclusion, a serpentine copper pipe heat exchanger can help to control local air temperature and can be used to control the temperature in a small area as well as use less energy than conventional air conditioning.
本文/Division of System Engineering Graduate School of Engineering Mie University, Japan
124p
Collection (particular)国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
Date Accepted (W3CDTF)2023-07-08T03:42:25+09:00
Data Provider (Database)国立国会図書館 : 国立国会図書館デジタルコレクション