无管换热器的稳态换热特性

对无管换热器中颗粒帘换热单元的稳态换热特性进行了研究,为目前空气预热器的研究提供新的指导方向.通过传热数学模型构建、详细数学计算和定量分析,研究了颗粒质量流量对换热单元以及无管换热器出口温度的影响.研究结果发现,在颗粒帘换热单元中,当颗粒质量流量足够时,冷流体加热后的出口平均温度可无限接近热流体初始温度,冷热流体之间实现深度换热,换热效果明显;在满足颗粒帘空隙率大于0.98的条件下,颗粒质量流量越小,气固颗粒在换热通道中越容易达到换热平衡;由于换热单元中间冷热源-气固颗粒之间的温差小,换热单元的换热效率低,使得由换热单元组成的无管换热器冷热气体之间的整体换热效率较低.

Heat transfer characteristics of the units based on a curtain falling through a horizontally-flowing gas stream and the tubeless heat tansfer

The static heat transfer characteristics of units with particle curtains in the tube- less heat exchanger were studied to provide a new direction for the research of the air pre- heater. Through the detailed calculation and quantitative analysis of the influence of the particles mass flow rate on the heat transfer characteristics of the units,it can be concluded when the particle mass flow is sufficient, the outlet average temperature of the cold fluid af- ter heating can be infinitely close to the initial temperature of the hot fluid, the particle-cur- tain based unit can make good performance in heat transferring between the failing particle curtain and horizontally-flowing gas stream. Under the condition that the particle voidage is greater than 0.98, gas and particles in the units with smaller particles mass flow can reach thermal equilibrium more easily. The results also show that the overall heat exchanger effi- ciency of the tubeless heat exchanger composed of two heat transfer units is low due to thesmall temperature difference between the particles and gas in the heat transferring units.