基于太阳能颗粒集热的超临界CO2流化床换热器模拟研究

Numerical study on heat exchanger of supercritical CO2 Brayton cycle fluidized bed boiler based on solar particle-receiver

基于太阳能颗粒集热的超临界CO2布雷顿循环系统效率高,发展潜力巨大。本文应用更加精确的颗粒侧传热模型,构建了超临界CO2流化床换热器模型,以100 kW换热功率的换热器工况参数为基础,对传热管外径尺寸、管束数量、颗粒粒径和流化气体温度进行优化。结果表明:在满足CO2流动压损为0.01MPa的条件下,优化后换热器的管束参数为管外径10 mm,壁厚2.9 mm,管束数量97根;选择小粒径颗粒时,临界流化速度较低、流量较小,可以有效降低气体热损失,提高换热器热效率和降低风机能耗,优化管束参数条件下,当颗粒粒径从100μm增至500μm时,气体热损失从70.32 W增至1 176.00 W,热效率从99.93%降至98.84%,风机能耗从21.60 W增至405.97 W;流化气体入口温度从570℃提高到630℃,换热器热效率从98.52%提升至99.64%。

With high thermal efficiency, the supercritical CO2 Brayton cycle system based on solar particle-receiver has great development potential. By applying a more accurate particle-side heat transfer model, the supercritical CO2 fluidized bed heat exchanger model is established. On the basis of the operating parameters of the heat exchanger with 100 kW heat transfer power, the external diameter, tube bundle number, particle size and fluidized gas temperature of the heat transfer pipes are optimized. The results show that, under the condition that the flow pressure loss of CO2 is 0.01 MPa, the optimized tube bundle parameters of the heat exchanger are as follows: the outer diameter of the tube is 10 mm, the thickness of the tube is 2.9 mm, the number of the tubes is 97. When the small particle size particles are selected, the critical fluidization velocity is low, the flow rate is small, so the heat loss of the gas can be effectively reduced, the heat efficiency of the heat exchanger can be improved, and the energy consumption of the fan can be decreased. With the optimized tube bundle parameters, when the particle size increases from 100 μm to 500 μm, the heat loss increases from 70.32 W to 1 176.00 W, the thermal efficiency declines from 99.93% to 98.84%, the fan power consumption increases from 21.60 W to 405.97 W, the inlet temperature of the fluidized gas rises from 570 ℃to 630 ℃, and the thermal efficiency of the heat exchanger increases from 98.52% to 99.64%.