First, energy conservation and consumption reduction have been listed as the top priorities of the “Eleventh Five-Year Plan”.

Over the past ten years, China’s economic development has been developing rapidly. The annual growth rate of GDP is above 10%. However, this is at the expense of high energy consumption. The energy consumption per million US dollars of product output in China reaches 1,274 tons of standard coal, which is an international standard. 2.4 times that of the United States; 2.5 times that of the United States; 4.9 times that of the European Union; and 8.7 times that of Japan. China's annual coal consumption has reached 1.42 billion tons. If the "Eleventh Five-Year Plan" plans to double GDP, according to the current level of energy consumption, annual demand The production of nearly 3 billion tons of standard coal is difficult to sustain in terms of resources, production, environmental protection, safety, and transportation. During the “10th Five-Year Plan” period, the central government has proposed that under the premise of a slight increase in total energy consumption, the energy consumption per unit of output value should decrease by 15 to 17%. However, the implementation result is that the total energy consumption increases by 10%; however, the energy consumption per unit of output does not decrease. At 7%, the Central Government was in a hurry, and local governments and enterprises turned a deaf ear. If we do not pay close attention to energy saving and consumption reduction, excessive energy consumption will certainly become a bottleneck restricting the further development of China's economy. During the “Eleventh Five-Year Plan” period, the Central Government will make the greatest determination to regard energy conservation and consumption reduction as the top priority in economic construction. While ensuring that GDP is doubled, energy consumption per unit of output value should drop by 20% within five years. China's industrial energy consumption accounts for 68% of total energy, and people's life consumes only 11.4%. Therefore, the focus of energy conservation should be on industry, especially high-energy-consuming industries such as electricity, metallurgy, steel, petrochemicals, building materials, transportation, etc. .

Second, the important role of flow meters in energy conservation monitoring Past facts show that it is not enough to publicize energy conservation and consumption reduction from top to bottom. It is necessary to implement energy saving indicators to the main leaders of local governments and enterprises and include them in their achievements. It may only be taken seriously. Whether or not the index has been reached must adopt a scientific change of state, and the effect of energy conservation should be evaluated through digital monitoring of the instrument. To this end, the central authorities instructed the relevant departments to formulate the national standard GB17167-2006, which is the “General Principles for the Equipping and Management of Energy Measuring Instruments for Energy-using Units”, which was announced on January 1, 2007. The five articles in GB17167-2006 (4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.3.8) are mandatory articles, and the core content is: All units and equipment capable of reaching a certain size must install energy monitoring. Instrumentation, but also on the use of energy, the type of monitoring instruments and accuracy grades have made clear provisions.

In energy monitoring instruments, in addition to electricity meters and solid-state coal weighing meters, other gaseous and liquid energy sources (such as crude oil, refined oil, heavy oil, residual oil, natural gas, liquefied gas, and gas...) and energy carriers Quality (water, steam) must use flow meters. Even for solid-state energy coal, a flush-plate flowmeter or a gas-solid two-phase microwave flowmeter can be used in the continuous operation in the process industry. Therefore, the flow meter plays an important and irreplaceable role in energy monitoring instruments.

Third, for energy monitoring The characteristics of the flow meter affect the flow meter many factors, in order to meet these requirements, the type of flow meter also up to 200 or so, how to use reasonable, not a lot of effort. This article is limited by space, omitting the general selection principle, focusing on two issues that should be noted in energy monitoring:

1. Accuracy: In the energy monitoring, the accuracy of the flow meter should be placed in an important position, and GB17167 also made reasonable and explicit provisions for this purpose. Since it is required to quantify the effect of energy conservation and consumption reduction, and to quantify the problem accurately, the flow meter should have the necessary accuracy. Otherwise, if the accuracy is low, the knowledge is poor, and the energy conservation effect is not well understood, how can it be properly assessed? How to "prescribe the right medicine" to improve energy-saving measures? Of course, it is not the more accurate the better, the high accuracy of the price of the instrument are more expensive, or should be targeted at the object of monitoring, realistic and reasonable selection, such as measuring the accuracy of the instrument should not be less than 0.5~1 grade; gas energy measurement is 2~2.5 grades; test load energy (water, water vapor) can also be as low as 2~2.5 grade.

2. Permanent pressure loss: The flow meter is an important tool for assessing energy conservation and consumption reduction, and it is not only not energy-efficient, it will also consume energy. This is because when the fluid flows through the resistance element in the instrument, it will generate eddies, like the friction in the mechanical motion, to consume energy in the form of reduced fluid pressure. Some instruments such as Venturi, ultrasonic, electromagnetic, etc. Although there is no resistance, the fluid will also produce friction with the instrument surface, resulting in a smaller pressure loss. In order to maintain the normal operation of the process, it is necessary to increase the power of the pump (or fan). This is due to installation of flow meters caused by the additional operating costs, the cost of the instrument structure will vary greatly, select the flow meter for energy-saving assessment, of course, should choose those with low pressure loss, energy consumption, low annual operating costs Instrumentation, clear-sounding behavior, and counterproductiveness are certainly not what people expect.

Fourth, several energy monitoring flow meter comparison 1, throttling device: Based on the throttling differential pressure, measuring the square root of differential pressure can be found in the size of the flow. For a long time, these instruments have been able to withstand harsh working conditions and have been based on international standards. They used to occupy 60 to 70% of the market for flow meters, with up to two to 30 types.

1Classical formula: International and domestic standards have been established, represented by orifices, nozzles, and venturis. The orifices are shown in Table 1. The pressure loss is relatively large. The nozzles are used to measure steam and the pressure loss is second only to the orifices. Board (see Figure 1). When the pipe diameter is more than 0.3 meters, it is recommended not to choose. Venturi pipes have small pressure loss, but they are bulky and consume a lot of high-energy-consuming steel. It is not easy to manufacture and transport, and the selection should be cautious.

2 Inner Cone: Propaganda is very large in the past 3 to 5 years. It is considered to be a meter with small pressure loss, high accuracy, and almost no straight pipe section. Its pressure loss is under different β (Figure 1), second only to Orifice, slightly higher than the nozzle, not energy-saving instruments; its accuracy was calibrated *1, under the large diameter (D> 300mm); the dispersion coefficient of the outflow coefficient is about 5%. Its main advantage is that it adopts an annular passage and has a rectifying effect. Therefore, it requires that the length of the straight pipe section is much smaller than other throttling devices. In the case where the pipe diameter is increasing day by day, it is difficult to meet the straight pipe length required by the flow meter. Outstanding advantages.

3 Loss-related information (lo-loss) has been published for 30 years. Similar to the shortened Venturi tube, the main feature is a permanent pressure loss.

4 shuttle *2: take the inner cone, low pressure loss tube both the length, with an annular channel can shorten the advantages of the length of the former straight pipe; also has the lo-loss tube pressure function after throttling, a patented product.

2. Plug-in: Simple structure, easy installation, low cost, and continuous flow and fold, but its accuracy is low. It is only suitable for large pipeline flow detection. It can be used in energy monitoring for occasions with low accuracy requirements.

1 measuring speed: measuring the flow rate of a point in the pipeline instrument, such as double venturi; plug-in vortex, turbine, electromagnetic, pitot tube. According to ISO7145, the accuracy is ±3%. If the straight pipe is less than 30D, the accuracy will be less than ±5%*3.

Recently introduced in the market a test tube similar to the deformation of the skin, the biggest advantage is not easy to block, put three in the top of the pipeline, each need to use a differential pressure transmitter, the price is more expensive. Allegedly designed according to ISO 3966, but did not meet the requirements of the standard required to arrange 20 test points in the cross-section. The relevant article did an error analysis on it*4, but did not consider that when the velocity distribution is not ideal, the interference coefficient γ*5 that affects the accuracy is the greatest. Therefore, the measurement error will exceed ±3%.

2 measured radial multi-point flow rate: A typical instrument for the average speed tube, due to many measuring points, the accuracy can be better than the plug speed meter measuring speed. Usually only measuring the multi-point flow velocity in the cross-sectional diameter direction, in the need to improve the accuracy, can also be inserted into each other into the two average velocity tube 900, it is more in line with ISO3966 measuring point requirements.

3, no resistance flow meter. This type of instrument is characterized by a simple mechanical structure, no resistance within the pipeline, small pressure loss, accurate and high, is the most potential development of flow meters, such as ultrasound, Coriolis, electromagnetic, the annual growth rate of the market in the past five years respectively 10.4%, 6.9%, 2.4%.

1 Electromagnetic: Although it ranks first in the flow meter market, it can only measure fluids with a conductivity greater than 10-5 S/cm, and cannot measure oil and natural gas, but can only measure energy-carrying water.

2 Coriolis: Although there is no resistance in the tube, but the flow is required to flow through the instrument to 1800, so the pressure loss is greater, the accuracy can be as high as ± 0.5%, the diameter is currently less than 0.25 meters, can be used for trade accounting requirements for accurate measurement Occasions.

3 Ultrasound: can be used for a variety of fluids, the accuracy can be as high as ± 0.5%, pressure loss is small, the ratio of the range is large, the relevant standards have been established at home and abroad, is the best energy monitoring instrument. Currently, in addition to the selection of more expensive effects, according to users, in-site applications and anti-noise performance have yet to be further improved.

V. Summary 1. The instrument selection should be comprehensive and rational. From the perspective of energy monitoring, this article emphasizes that the flow meter has several features such as high accuracy, low permanent pressure loss, and low price. From the above, there is currently no perfect instrument, some instruments such as orifices, Coriolis, positive displacement, although the pressure loss is large, but there are also characteristics, or there are standards to follow (such as orifice plate), or accurately higher When the pipe diameter is not large, the problem of pressure loss is not prominent, and it is not necessary to waste food. Therefore, the selection should be comprehensive, comprehensive consideration, excessive exaggeration or devaluation of a certain kind of instrument is one-sided and undesirable.

2. Development trend: Currently, there are many types of flow meters and they are in a state of “Spring and Autumn and Warring States Period”. However, with the rapid development of science and technology, new types of instruments such as electromagnetic, ultrasonic and Coriolis have become increasingly user-friendly due to their simple structure and improved functions. The favor. The classic type (orifice, nozzle, venturi) or large pressure loss, requiring long straight pipe lengths are difficult to meet and other shortcomings, the market development is declining, the annual growth rate is -2.3%. New throttling devices are also emerging, so the replacement of classic traditional instruments with new flow meters will be a long process and not a one-time event.