Research On Fouling Resistance Of Pipeline Based On Measurement Of Fouling Thickness

Heat exchanger is widely used in industrial production.Fouling is a solid material accumulated continuously on the heat exchanger surface of heat exchanger.It is usually a poor conductor of heat.The existence of fouling leads to the increase of heat transfer resistance of heat transfer equipment,the decrease of heat transfer performance and the increasing resistance of medium flow,resulting in huge economic loss.At present,the measurement of fouling resistance is mostly based on the operation parameter measurement and the heat transfer theory.It involves many indirect parameters,and introduces various errors.The accuracy of measurement is difficult to guarantee.From the basic fouling model,this paper carried out theoretical and experimental research,the accurate measurement of the fouling resistance and reasonable descaling,scale and suppression strategies,increase in the thermal efficiency and system efficiency has important theoretical and practical significance.This paper is based on the Kern-Seaton fouling model,according to the assumption that composition and characteristics of fouling on the inner wall of pipe are distributed evenly along the radial and fouling thickness.The relation between fouling thickness and fouling resistance is deduced from the net fouling growth rate.Two key parameters of fouling thermal resistance detection were determined—fouling layer thickness and fouling thermal conductivity,and the fouling thermal resistance model was established.The thickness of the fouling layer is detected by the ultrasonic time domain reflection method,and the thermal conductivity is detected by the transient plane source method.According to the large noise of the echo signal in the actual measurement,and the echo of the fouling layer is difficult to recognize,put forward the energy ratio as the noise signal identification parameters,design CEEMD-wavelet entropy thresholding method processing echo noise signal.Taking typical calcium carbonate fouling as an experimental object,select the commonly used diameter of 100 mm,thickness of 4mm stainless steel pipe for simulation heat pipe to detect fouling layer thickness.Comparing this method with wavelet soft threshold and hard threshold,the test results show that,the CEEMD-wavelet entropy thresholding method used in this paper has good noise treatment effect.According to the input noise intensity,the SNR increased by 8.3 dB on average,the MSE increased by 0.3 on average.Then several groups of fouling thickness test experiments were carried out and the detection accuracy was verified,and the reliability analysis was carried out after the fouling thermal conductivity detection.Finally,the average fouling resistance of the heat transfer pipe is obtained by calculating the fouling resistance of the internal equidistant points in the pipe.The experimental results show that the ultrasonic time domain reflection method is adopted to fouling in the 0 and 1 mm thickness detection error within 14%,the thickness of scale within 1 to 2 mm layer detection error within 12%,the thickness of scale within 2-3 mm layer detection error within 8%.The mean square error of the detection of fouling thermal conductivity is ten to the power of minus four,and the reliability of the test results is reliable.The fouling resistance detection method proposed in this paper can achieve fast detection of fouling resistance,greatly reduce the detection complexity of fouling resistance,and has high detection accuracy and repeatability.On the basis of ensuring the safe operation of the system,it provides reliable data reference for reducing the design of redundant heat exchanger area and formulating a reasonable fouling cleaning cycle.It provides a theoretical basis for maximally increasing the efficiency and economy of the heat exchanger system.