Abstract:

The temperature uniformity and entropy generation due to heat transfer inside a thermal cycling test chamber are investigated numerically under various operating parameters. Boussinesq approximation and k-ω model are used in the simulation and the result is validated by previous experiment. The result shows that in the range of 4.3×10³ ≤ Re ≤ 8.6×10⁵ and 4.62×10¹³ ≤ Gr ≤ 1.38×10¹⁴, both forced convection and natural convection contribute to the fluid flow and heat transfer. Fluid close to the walls gets heated and rises along the walls due to the buoyancy force while that near the center line accelerates downward to the exit. The temperature at the given height always increases from the center line to the walls. From the top to bottom of the cycling chamber, the temperature increases around the center line while decreases near the walls. The dimensionless standard temperature deviation increases with Reynolds number and changes little with Grashof number. During the mixed convection, the entropy generation due to fluid friction is much smaller than that by heat transfer, and the latter increases with both Reynolds number and Grashof number. In addition, the expressions of wall Nusselt number, dimensionless average temperature, dimensionless temperature standard deviation and dimensionless entropy generation by heat transfer are also provided.

Key words: numerical simulation, convection, heat transfer, temperature uniformity, entropy generation

摘要：

以数值模拟的方法研究了不同运行参数下航天器热循环试验箱内温度均匀度与熵产的变化规律。结果表明，在4.3×10³≤Re≤8.6×10⁵、4.62×10¹³≤Gr≤1.38×10¹⁴范围内，由于强浮升力的作用，壁面附近出现回流区，温度由上往下降低，中轴线附近气体加速下沉，温度由上往下升高。箱内量纲1温度标准偏差随Reynolds数增大而增大，随Grashof数变化不明显；混合对流过程中流动熵产远小于传热熵产，熵产数值随Reynolds数、Grashof数的增大而增大。提出了壁面Nusselt数、试验箱内量纲1平均温度、量纲1温度标准偏差及量纲1传热熵产随Reynolds数、Grashof数变化的关联式。

关键词: 数值模拟, 对流, 传热, 温度均匀度, 熵产