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The vortex flow meter is a type of instrument used for measuring fluid flow in pipelines, and it is widely employed in water supply and heating systems. In the past, these meters did not have high precision, but technological advancements have led to improvements in their production and development. As modern cities develop further, industries that relied on steam for operations and were environmentally harmful have been moved out of the city centers. In northern cities, only residential, commercial users, as well as those in the heating industry, remain; they use gas solely for heating in winter. As a result, the existing steam-based heating systems can be replaced by hot water heating systems. 1. Advantages and disadvantages of heating media The temperature difference between the inside and outside of the pipes in steam heating systems is quite large; transferring heat over long distances results in significant pressure losses. High insulation requirements are necessary, and once the steam is converted into hot water, its efficiency is quite low. Heating users then use heat exchangers to convert the steam back into hot water for distribution to individual households, which results in some loss of thermal efficiency. In addition, there are costs associated with the heat exchange equipment. Of course, steam produced by power plants is used for electricity generation as well as to supply industries that require steam – something that hot water cannot replace. Hot water heating networks require two pipes, which increases costs, but the hot water supplied can be reused. Such systems are typically provided by hot water boilers and large heat exchange stations. The temperature of the supplied hot water is low, resulting in minimal heat loss; it can be delivered directly to households or through water-to-water heat exchange. 2. Hot water heat metering: Heat metering is generally used for hot water pipelines; in some cases, mass metering is also employed. When heat metering is used: Q = M(C_in – C_out). In the formula, Q represents heat energy, M denotes the mass of hot water, C_in is the heat value at the water inlet, and C_out is the heat value at the water outlet. It can be seen from this formula that the amount of heat supplied depends on the mass of hot water as well as the heat values at the inlet and outlet; when the temperature difference between the inlet and outlet is large, the difference in heat values is also large, resulting in more heat being used. 3. Heat metering scheme (1) Single-meter metering: One flow meter, two platinum resistors, and one heat integrator are used. Applicable scenarios: Hot water users do not consume hot water, and the supplied hot water has no leaks; the quality of the inlet and outlet water is equal. Calculation formula: Q = M(C_in – C_out). (2) Dual-meter measurement: Two flowmeters, two platinum resistors, and one heat integrator are used. Applicable scenarios: hot water consumption by end users, with varying quality of water at the supply and discharge points. Calculation formula: Q = M_in (C_in – C_out). Here, M_in is the mass value measured by the flow meter at the water inlet. The water loss is calculated using a heat integrator (M_in – M_out). To identify hot water losses and economic compensation. 4. Application of vortex flow meters in hot water metering (1) Range: Compared to steam, hot water has a higher medium density, which results in greater forces acting on the sensor element and a larger amplitude of the signals generated. The signal processing range is wide; high-quality sensors can achieve a range ratio of 50–60:1, thereby providing a broader range for measurement and selection and enabling them to serve more hot water users. (2) The single-phase medium remains unchanged: In a steam medium, depending on the temperature and the transmission distance, its states can be superheated steam, saturated steam, wet saturated steam, steam-water mixture, and water. Flowmeters are highly inaccurate in the latter three states, whereas for measuring hot water as a single-phase fluid, vortex flowmeters can ensure greater accuracy. (3) Calibration and operation are more similar: When calibrating vortex flowmeters for measuring steam, air is generally used. Due to the difference between the calibration medium and the operating medium, there is a discrepancy in measurement accuracy. When using hot water for calibration, the same medium is employed as for actual measurement, resulting in a smaller error between calibration and actual readings. (4) Accurate measurement at flow rate limits: For steam measurement, due to the properties of the medium itself and the design of the heat exchange units, the steam flow velocity can exceed 90 meters per second, which causes the vortex flow meter to lose pulses and result in inaccurate measurements. When measuring hot water, owing to the properties of the medium and limitations of the equipment, the flow velocity rarely exceeds 9 meters per second, thus avoiding the problem of lost pulses at the upper limit for vortex flow meters. (5) Installation of vortex flow meters: Unlike when measuring steam, when measuring hot water, the installation of vortex flow meters must ensure that the pipe is fully filled with fluid and free of air. Horizontal installation is suitable at lower levels, while vertical installation requires that the hot water flow from bottom to top; if the pipe is not fully filled at the flow meter location, accurate measurement will not be possible. (6) Factors affecting the accurate measurement of vortex flowmeters: Unlike steam metering, since the compressibility coefficient of water is very low, factors such as pressure, temperature, and the nature of the medium that affect steam metering have little impact on hot water metering. Nevertheless, attention should still be paid to the effect of vibrations on vortex flowmeter performance. (7) Losses: The water supply network is primarily used to control the amount of water lost, and this represents a key indicator of losses; the extent of these losses can be determined through water replenishment. It is necessary to eliminate leaks in one’s own pipeline system, as well as to control the non-heating use by heat customers.