关键词: 相变材料, 强化传热, 自然对流, 优化, 数值模拟

Abstract:

The melting process of paraffin wax in rectangular unit is simulated by using FLUENT software. The effects of different upper geometry sizes and different wall temperatures on the melting process of different rectangular units are studied separately. The criterion relations between the liquid fraction β and the dimensionless number Fo, Ste, and Ra are obtained by nonlinear fitting. The scheme and basis are provided for optimizing the overall melting rate of PCM (phase change material) in the rectangular unit. The results show that, during the paraffin melting process, the time proportion of natural convection as the dominant heat transfer method increases first and then decreases as the size of the upper part of the rectangular unit increases. The enhancement of heat transfer by natural convection increases with the increase of the unit upper size. However, the average heat storage rate first increases and then decreases with the increase of the upper size of the unit until it tends to be stable, and there is an optimal value. During the paraffin melting process, the time proportion of natural convection as the dominant heat transfer method increases first and then decreases as the size of the upper part of the rectangular unit increases. The temperature difference is one of the key factors affecting the melting of PCM. The temperature difference is increased from 43 °C to 53 °C, and then from 53 °C to 63 °C, as a consequence of this, the melting time is shortened by 14.63% and 24.26% respectively.

Key words: PCM, heat transfer enhancement, natural convection, optimization, numerical simulation