Thermal Insulation Performance Test of the Temperature Control System above Grain Bulk in a Single-storey Warehouse under Different Operating Conditions
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Abstract:
A single-storey grain bulk warehouse was used as the research object, and a temperature control test system above the grain bulk was set up for a variety of thermal insulation experiments under different working conditions, to investigate the factors affecting the insulating effect of the system in hot climates. The results showed that the temperature rise of the grain bulk caused by external heat mainly occurred to the grains on the grain bulk surface 10 cm below the grain loading line. The surface temperature control system of grain bulk reduced effectively the impact of sudden high external temperature on the surface grain temperature. Under the optimal conditions, the surface temperature of the grain bulk was reduced by 1.67 ℃. Among the influencing factors such as inlet air temperature, inlet air speed, and interlayer height, the inlet air temperature exhibited a greater impact on the surface temperature rise of grain bulk, compared with inlet air speed and interlayer height. In the actual projects, low air speed and temperature were used to decrease the unit cost to 5.6 yuan/ton grain while reducing energy consumption. The Nusselt number (Nu=hl/λ) Nu was used to define the heat transfer performance of the system, with the dimensionless temperature θ in the range of 0.4~1. Nu increased (between 45 and 85) with Θ, but was not affected greatly by H (Nu in the range of 82~89 when H increased from 0.05 to 0.09). During the tests with an inlet air temperature of 22 ℃, the air humidity close to the upper surface of the system inside the warehouse was reduced by 13% compared to the initial value, which was 5% higher than the humidity outside, with no condensation occurring in the grain bulk.
