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超临界水流化床反应器可以有效气化湿生物质并且高效产氢。超临界水流化床反应器工作的表观流速比较低,颗粒与流体之间的自然对流换热是主要的传热方式.本文通过Boussiesq模型和真实物性流体模型模拟研究了层流条件下单颗粒与超临界水在拟临界点附近的自然对流换热.由于物性变化的影响,颗粒表面附近呈现高速度梯度、高表面涡量和高温度梯度的现象。临界水导热系数和比热的变化对拟临界区的自然对流传热起主导作用,Grashof数和平均Nusselt数在对数坐标下为线性关系。
Supercritical water fluidized bed reactor can effectively vaporize wet biomass and efficiently generate hydrogen. Supercritical water fluidized bed reactors work low in apparent velocity and natural convection heat transfer between particles and fluid is the main heat transfer mode.Based on Boussiesq model and real physical fluid model, The natural convection heat transfer between particles and supercritical water near the pseudo-critical point.Due to the change of physical property, the phenomena of high velocity gradient, high surface vorticity and high temperature gradient appear near the particle surface. The change of critical water heat transfer coefficient and specific heat plays a leading role in the natural convective heat transfer in the quasi-critical region. The Grashof number and the average Nusselt number are linear in logarithmic scale.