College】 【weak form of energy measured in the field of air conditioning --- Power By 【China】 weak home network.

First, an overview

With the rapid development of the social economy, national building energy consumption accounts for the proportion of the total energy consumption in the community is currently up to 30%, and continue to increase. The data suggest that the central air conditioning energy consumption accounted for building energy consumption of 40% to 50%, is an important part of building energy consumption. Therefore, the central air conditioner to take the necessary measures to help reduce social total energy consumption. And reduce the energy consumption of central air conditioner is to establish practical measures in fair, reasonable and scientific system of charging for air conditioning. While large public buildings, especially large shopping, entertainment venues, the regional functionally different, yet comprehensive cold indicator, you cannot press the area assessed air-conditioning costs, but there is an urgent need to adopt measures to resolve the issue.

With the national energy policy and regulation of a series, central cooling of public buildings and more widespread application of central air-conditioning household metering technology, on the one hand through the measurement of fair use advocates user, active air conditioning, avoid wasting energy saving; on the other hand, through reasonable measures cost-sharing, the solution property management company toll difficult problem, the user "more more, less and less out" so that the fees charged according to follow. Deeper meaning through energy table reading assessment refrigeration unit of the actual cooling capacity, based on historical data for the establishment of databases, by actual data analysis on large public building energy-saving potential, thereby implementing on large public buildings to implement energy saving.

II. application of energy table

Although the "cold" with water, electricity and gas in the market economy have the same commercial property, but in measurement, than already entered the market and the success of the water, electricity, gas metering and charging a complex and difficult. Large space (same owners) air conditioning energy metering mainly in the primary table, the principle of measurement is to assume a measurement range of air conditioning for, return pipe on each of the installation of a temperature sensor (paired), temperature measurement for, backwater, the return pipe on the installation of a flowmeter, respectively measured refrigerant-water temperature and flow rate of the export and import, and then through the density and enthalpy of compensation and integral calculation, the consumption of "cold" measure. At present, in energy terms, according to the table using a flow meter selection, there are three different types, to mechanical, electromagnetic, ultrasonic type. Their main differences flow sensor principle and structure.

First of all from the technology and the application of the actual situation of angle on mechanical, ultrasonic, electro-magnetic products for a comprehensive analysis and comparison, and then, from the point of view of economic investment for life cycle cost analysis, selection of air conditioning equipment solutions.

2.1 mechanical flowmeter in household energy application table

Mechanical energy table through the impeller speed to measure freezing water flow, mechanical energy table flow sensor internal structure and is divided into single-stream and multiple-beam-type streams, in accordance with its counter is hot water contact and divided into dry and wet. Dry-type sensor of the impeller speed usually by magnetic coupling delivered to counter, and import the table part of mechanical energy uses inductive transmission, that is, non-magnetic, can reduce water rust on the table.

Due to the technical and price reasons, my early majority use a variety of mechanical energy meter, including imports and domestic brands. But in recent years use andresearch practice shows that the use of mechanical energy meter air conditioning cooling capacity, there is a range of issues, such as narrow and start the flow range is too large, frozen water flow coefficient differences. Due to the pervasiveness of chilled water impurities, scale and flow patterns are not smooth, very easy to produce measurement error or not quantifiable phenomenon produces metering disputes to property management. At the same time, the amount of mechanical energy table maintenance, usually less than one month need air conditioning system outage on the water, cleaning flowmeter, wear larger to replace the flowmeter. In addition, the country's air conditioning system running status on energy table also raised more than foreign heat metering demanding requirements, such as circulating water is poor; many causes water not only contains a lot of harmful chemical substances, there are a variety of flow sensor destructive small particle impurities. These issues will also be a long time in memory. Therefore, for mechanical energy meter, because of its structure and principle aspects inherent limitations, the possibility of a rating period (five years) in normal and accurate operation, is a very serious challenge.

2.2 ultrasonic technology in household energy application table

Measurement of the air conditioner, have some project uses ultrasonic energy table. Ultrasonic-energy table is measured using ultrasonic in hot media of the time difference (acoustic propagation in fluid, smooth flow direction acoustic propagation velocity increases, counter current direction is reduced, the same range has different propagation time). The difference between using propagation velocity and measured fluid velocity of strike to infer the flow velocity. Because of its internal measuring Chamber does not have any moving parts, so on media elements or impurities not strict requirements. Therefore, from a life cycle cost, reliability and accuracy, the ultrasonic energy table are superior mechanical energy meter. However, in 2000, due to the price, in the field of household-energy table or mechanical energy meter domination. Now with the mechanical energy meter is aware of the defects, has been largely eliminated.

But in practice, some people come into a misunderstanding, namely simple import of ultrasonic heat meter to measure the amount of cold and air conditioning. From an engineering practice, the effects of unsatisfactory, even a system running a bad situation. The reason for a heat meter is imported (mostly European brand) abroad mainly apply to heating hot household metering, heating of the condition is "large temperature difference (the difference is 15 ° c) small flow," but for "the cold conditions is a small difference in temperature (maximum temperature is 5 ° c) and large flow." In heating environment, application of ultrasonic heat meter has been very popular, very mature technology, and applied to cooling, condensation water will report in the report body, ultrasonic heat meter integrated structure allows condensation water infiltration into the table easily, damage to electronic components, a great deal of strain on the battery, halfYears when you are finished using the battery case (ultrasonic heat meter is generally available with battery, 6-10 years). Ultrasonic energy table diameter, the greater the price higher, sometimes energy table diameter size, its price will be much higher, so the cost of the investment is to consider using an ultrasonic energy table. In addition, the ultrasonic energy table selection is more complex, selection of key parameters of energy table is a system flow rather than system pipe diameter size according to flow to determine energy table model (the selected energy table minimum flow is less than the system piping of minimum flow, energy table of maximum flow is greater than the maximum system pipe flow rate), allows the installation of complex, the need to take measures of a reducer.

2.3 Electromagnetic induction technology in household energy application table

Mechanical energy meter is generally considered unsuitable for air-conditioning application metering, in ultrasonic energy table at the same time, the electromagnetic energy table appears. Electromagnetic energy table mainly adopts Electromagnetic Flowmeter. Its working principle is based on the Faraday, when conducting liquid flows through the siege in the magnetic field of the survey, both in flow direction and magnetic field perpendicular direction will produce and average velocity V proportional to the EMF E. Electromagnetic Flowmeter includes the pipeline and add-in.

Electromagnetic flow meter, temperature sensor and energy integrating instruments using fission installation, temperature sensor, using four-wire pair of PT1000 with high precision, wiring length can reach 100m, energy integrating instruments adopted Chinese display, consistent with domestic usage, you can display the measurement of individual parameters.