基于传热系数的高温循环流率测量方法研究

循环物料流率是循环流化床锅炉中重要的设计和运行参数,但其热态在线测量一直是难点。基于换热原理进一步改进和完善了在线测量循环流率的方法,通过热态试验研究了影响高温颗粒与管壁之间传热系数的因素,并且利用热态试验数据和Borodulya等提出的对流传热系数预测模型进行了关联式推导,从而将传热系数和颗粒流率相关联。结果发现,传热系数的影响因素包括颗粒流率、颗粒温度、颗粒粒径等;热态试验测量得到的物料流率值与预设值的误差在±25%内;在实际流率工况下,该方法可以将物料流率和传热系数一一对应,在较宽的流率变化范围内都具有良好的预测能力。根据研究结果,测量中传热系数确定后,由计算模型可以获得物料流率,即实现高温物料流率的测量。换热法测量循环流率的原理简单,成本低廉,通过研究进一步提升了其实用性,在循环流化床锅炉的循环流率测量领域具有广阔的应用前景。

Study on the measuring method of high-temperature circulatingflow rate based on heat transfer coefficient

Circulating material flow rate is an important parameter for the design and operation of circulating fluidized bed(CFB)boilers,but the hot-state in-situ measurements of it is still difficult.In the present study,the measurement method of circulating flow rate based on the heat transfer process was further improved.The effects on heat transfer coefficient between the high temperature solids and the tube surface were studied in hot state tests.The high temperature test data and the prediction model of the convective heat transfer coefficient proposed by Borodulya et al were used to establish the correlation between heat transfer coefficient and solid circulation rate.The results show that the influencing factors of the heat transfer coefficient include the solid circulation rate,particle temperature and the particle size.The error between the measured material flow rate and the preset value is within±25%.The method can match the circulating material flow rate and heat transfer coefficient in pairs,and has good prediction in a wide range of flow rate.According to the research results,once the heat transfer coefficient is determined in the measurement,the solid circulation rate can be obtained by using the proposed model,and thereby the measurement of high temperature solid circulation rate is achieved.The heat transfer method is simple and has the advantages of low manufacturing cost.Based on the research,it has further improved practicability.It is a promising method of the measurement of circulating flow rate in CFB boilers.