Performance Study And Unsteady Numerical Simulation Of Ultrasonic Heat Meter

In response to the energy shortage and environmental pollution, in addition to the development of new energy, energy conservation and emissions reduction is a powerful measures. Heating is large energy consumption and environmental pollution, the heat metering can effectively improve the disadvantages of the existing charging per square. Firstly,for household heating metering, heat meter must have the good performance. This paper studies several problems that affect measurement accuracy of ultrasonic heat meter, and put forward the corresponding optimization advice.Now the flow measure precision of the ultrasonic heat meter is the key and difficult. Factors affecting the accuracy of flow of the heat meter measurement have three aspects:one is the heat meter for flow measurement signal collection circuit;Secondly, the velocity distribution of water in the basic meter. Third is reliability of the ultrasonic heat meter testing device. The methods of the study in this paper include theory analysis and numerical simulation which is tested and verified by the experiment research., from the three aspects, this paper unsteady numerical simulate basic meter of the ultrasonic heat meter and analysis the several problems that affect the measuring precision.In order to improve the accuracy of ultrasonic heat meter flow measurement, in terms of measuring principle, the operating mode of heat meter is wide temperature range, by introducing the related correction formula to reduce the influence of temperature to the flow viscosity and ultrasonic wave velocity in the fluid, so as to improve the accuracy of signal collection and the rationality of selecting the modification coefficient of flow.About the basic meter structure, using software FLUENT to simulate DN25type ultrasonic heat meter with the RNGk-ε model, verify the accuracy of numerical simulation by contrast with the result of the experiment, according to the results of simulation, analysis the profile-liner average velocity in the basic meter and the status of the flow field. For reducing the disturbance of reflectors to the flow field in the basic meter, the basic meter of poor flow field and large pressure loss can be optimized by adding rectifier. After adding rectifier reflectors, the vortex on the center of the surface is decreased, the flow field in the basic meter becomes uniform, pressure loss of different flow point of are reduced. To improve the production efficiency of heat meter,on the evaluation basis of experimental measurement error and k coefficient, found that the bend and variable cross-section pipe of ultrasonic heat meter test device effect the measurement accuracy of the first meter largely, adding deflector in the bend can eliminate obviously the secondary flow, improve the accuracy of measurement. Installing screen pack in the entrance of the heat meter reduces the effection of variable cross-section pipe.In addition, the method of unsteady numerical simulation is used to research the flow conditions in the process of the ultrasonic heat meter pipeline valve opening, and compare with steady flow of heat meter, analyses the influence of open valve on the internal flow field and the change of the k coefficient. It provides a theoretical basis to improve the measure precision of the ultrasonic heat meter under different working condition.The methods in this paper is right, and is equipped with a large number of experiments and analysis of simulation data and charts, the results of analysis are clear and correctly, it has a certain guiding significance and theory value to study the ultrasonic heat meter flow measurement precision and improve the reliability of heat meter detection device and detection efficiency.