Development of On-Line Monitoring Device for Fouling in A Tube

从理论上提出了一种同时测量管内流量和污垢系数的方法，并进行了实验验证。其测量原理是基于受热长度、流量和污垢因子决定的换热特性，将外表面均匀热流密度局部加热的污垢管作为导热和对流的耦合问题进行了数值分析。由数值结果得出了受热段管壁温度、流量和污垢因子之间的无量纲关系及其与流体温度的关系。由数值结果估计，该方法在流量和污垢因子方面的精度约为3%。对一根钛管和一根带有两个不同长度加热器的铝黄铜管进行了测试。流速和污垢系数的测试范围分别为1~2.5m/S和0~2×10~(-4)m~(-2)K/W。加热功率控制、数据采集和数据分析由个人计算机自动完成。试验中流速Delta U和污垢系数Delta R的最大误差分别为：清洁管流Delta U=5%，给定流速Delta R=1.2x10^-5；m&lt；@12&lt；@D1K/W，同时测量Delta R=2x10&lt；@d1-5@&gt；d1 m&lt；@D12@&gt；D1K/W和Delta U=25%。

A method for simultaneous measurement of flow rate and fouling factor inside a tube is proposed theoretically and verified experimentally. The principle of the measurement is based on heat transfer characteristics which depend on the heated length, flow rate and fouling factor of the tube.A numerical analysis is carried out as a conjugate problem of thermal conduction and convection for a fouled tube which is locally heated with uniform heat flux density from the outer surface. Dimensionless relationship among tube wall temperature at the heated part, flow rate and fouling factor along with its dependence on fluid temperature is derived from the numerical results. The accuracy of this method which is estimated from the numerical results is about three precent in both flow rate and fouling factor.A titanium tube and an aluminum brass tube with two heaters of different length are tested. The test ranges for flow velocity and fouling factor are 1-2.5m/s and 0-2x10^<-4> m^2K/W, respectively. Heating power control, data acquisition and data analysis are automatically carried out with a personal computer. The maximum errors for flow velocity Delta U and fouling factor Delta R in the test are as follows: Delta U= 5% for clean tubes, Delta R= 1.2x10^<-5> m<@12<@D1K/W for given velocity, and Delta R= 2x10<@D1-5@>D1 m<@D12@>D1K/W and Delta U= 25% for the simultaneous measurement.