Hongzhan Technology Co., Ltd.'s heat metering and temperature control topics - Database & Sql Blog Articles

Heat metering and temperature control

With the development of the market economy, household heating uses thermal energy as a consumer product that needs to be purchased, and has been recognized by consumers. In recent years, the Ministry of Construction and the local construction commissions have also promulgated relevant promotion policies, requiring the implementation of heating households. However, heating household metering charges is still a new topic in China. It involves many issues such as policy, management, charging methods, related products, and technology. We set up this topic to discuss with our peers, aiming to promote the exchange of households in terms of heating and households, and to improve together. Here we first introduce some articles on the measurement of heating households published by major foreign and domestic related websites (if you infringe on your copyright, please write to me, thank you!), I thought it would be a good idea.
one. The significance of heat metering and temperature control
China has a vast territory, a large population, and a large scale of housing construction. Among them, residential construction accounts for 92% of residential buildings. The amount of residential construction is large and wide, and it is still on the rise, and this upward trend will continue for 20-30 years. But we must be soberly aware that the rapid growth of such a huge housing and residential construction in our country is at the expense of high consumption of resources and energy. In addition to using the most direct resource, land, the growth of residential energy consumption is A major limiting factor in the development of residential construction. At present, due to the poor thermal insulation and airtight performance of buildings in China, the heating system has low thermal efficiency, and the heating energy consumption per unit of residential building area is three times that of developed countries under the same climatic conditions. By the year 2000, the energy consumption of urban buildings in the country will account for 14% of the total energy production, which means that only the energy-saving measures can be taken to maintain the sustainable development of the building.
Foreign experience in heat metering shows that the system of charging according to heat is the most effective means to encourage users to consciously save energy. According to statistics, the "big pot" type heating package fee system is charged to the user according to the actual heat used, which can save 20% energy. -30%. In China, welfare heating has been implemented for a long time, and the energy consumption has nothing to do with the interests of users. This is a major drawback left by the big pot rice system, and it is also the biggest obstacle to the energy-saving work of the heating system. According to the requirements of the National Energy Conservation Law, the energy used for living must be metered to the user. This is a major reform that meets the requirements of the socialist market economy. It is an important measure for heating enterprises to change their operational mechanisms and is a fundamental measure to promote building energy conservation. We only follow the laws of the market economy, and use heat as a commodity. The user can adjust and control the use of the heat, and charge according to the practical heat, in order to mobilize the enthusiasm of heat and heat, and thus promote energy conservation.
The ultimate goal of the heating system to charge the heat is to save energy in the building. In addition to strengthening the building insulation and reducing the design energy consumption, the indoor heating system must have a temperature control device. Temperature control is one of the preconditions for achieving heat metering. Only the metering and charging device without the temperature control method of the indoor system can not achieve the purpose of energy saving, but only for the purpose of charging, which actually deviates from the fundamental purpose of building energy saving. Therefore, heat metering and temperature control are often inseparable. Although the large-scale promotion of heat metering must be carried out under the premise of temperature control, in addition to energy saving and capital saving, temperature control has another function of improving indoor comfort and improving heating network heating quality. Therefore, the heat metering must be used in conjunction with the temperature control to complement each other and achieve the best results.
two. Foreign application and China's development status
Foreign countries, especially in the Nordic countries, have attached great importance to building energy conservation since the energy crisis of the 1970s, and have formulated relevant policies, regulations and supporting technical measures. The centralized heating system in developed countries is a dynamic variable flow system with advanced regulation and control technology, perfect control means and high equipment quality. Usually the heat provided by the primary pipe network is exchanged at the heat station for secondary heating hot water and domestic domestic hot water. In the secondary water system of the heat station, the water pump with variable frequency speed regulation, differential pressure controller, electric regulating valve, temperature compensator and return water temperature limiter are installed. There is a complete set of mature heating system operating modes. Central heating is charged by the heat of the world, and it is also a basic measure for energy conservation and environmental protection in various countries. At present, in addition to the Western developed countries have adopted this measure, Eastern European countries and countries in the former Soviet Union are gradually promoting. At the same time, the corresponding technologies for centralized heating and calorie charging have been further developed. The dynamic adjustment of the heating system is more advanced, the billing technology is more reliable and accurate, and the entire heating and heating billing device is becoming smaller and computerized. Since the current heating charging system in China is charged by area, it has suppressed the realization of heating and energy saving, and at the same time caused problems such as difficulty in collecting heat charges. At present, with the deepening of research on heating energy conservation, heat metering and temperature control have become the focus of attention and research in China's HVAC industry. As China's research on heat metering and temperature control is in its infancy, there is a certain degree of blindness and exploratoryness. Some problems and controversies have emerged in the research. For example, is the foreign thermal measurement method and promotion experience suitable for China's national conditions? Can foreign temperature control and heat metering products be fully applicable in China? What kind of system can apply metering and temperature control? In the face of such a large market demand in China, what products can be developed and what system methods can be adopted to be economical, simple and reliable, and to meet the comfort needs while achieving energy-saving purposes? Wait, these need us to conduct more in-depth research and discussion. In recent years, many domestic departments have done a lot of effective work, and have done some demonstration projects in the establishment of heating systems and heat measurement methods suitable for heat measurement in residential buildings, and conducted useful explorations and achieved certain results. For example, the heat distribution type heat metering of Tianjin Kaili Garden and the energy metering of Longtan Road energy-saving residential ones provide valuable experience for the next step of research. In addition, in terms of temperature control and heat metering products, on the one hand, large foreign companies such as Danfoss, Honeywell, Siemens, Schlumberger, etc. entered the Chinese market on the one hand, on the other hand, domestic production enterprises entered the initial stage, temperature control and heat. The research and development of metering products has developed rapidly, and many companies have developed similar products.

three. Heat metering method and instrument
3.1 Thermal measurement method
At present, the methods for measuring calorie use by households in Europe and the United States are basically the following three types:
(1) Directly measure the user's use of heat from the heating system.
The method needs to measure the flow rate of the household system and the temperature of the return water. The meter used is a heat meter. The method is characterized in that it is accurate in principle, but the price is relatively expensive, the installation is complicated, and the metering error is large at a small flow rate. Currently used in France, Sweden and other countries.
(2) Determine the user's heat by measuring the amount of heat dissipated by the user's heat sink.
The method is to determine the heat dissipation of the heat sink by using a function of the difference between the average temperature of the heat sink and the temperature of the room. The instrument used in this method is a heat distribution table, and the commonly used ones are evaporative and electronic. Among them, the evaporative heat distribution table is characterized by low price and convenient installation, but the measurement accuracy is poor. Currently widely used in Denmark and Germany. The characteristics of the electronic heat distribution meter are: the measurement is more accurate and convenient, the price is lower than the heat meter, and the value can be read outdoors. Currently popular in Europe and America.
(3) Determine the user's heat consumption by measuring the user's thermal load.
The method measures the indoor and outdoor temperatures and cumulatively sums the indoor and outdoor temperature differences in the heating season, and then multiplies the room constant (such as the volumetric heat index) to determine the charge. The instrument used in this method is a temperature measuring instrument. However, sometimes the set temperature of the memory radiator temperature control valve is used as a typical indoor temperature and a certain reference temperature is used as an outdoor temperature. The method is characterized by easy installation and low price. However, due to the principle of paying the same heat fee for the same comfort, the user's heat fee is only related to the set or measured room temperature, and the phenomenon of wasting energy such as window opening is not restricted, which is not conducive to energy saving. At present, Germany is not allowed to be used, and it is used in the United States and France. 3.2 heat metering
(1) Heat meter
The heat meter consists of a hot water flow meter, a pair of temperature sensors and an integrated calculator. The meter is installed on the water supply pipe of the system, and the temperature sensors are installed on the supply and return pipes respectively. The heat consumed by the user for a period of time is the integral of the product of the flow rate of the supplied hot water and the enthalpy of the return water. The heat meter uses this principle to measure the hourly flow rate with a hot water flow meter and measure with a temperature sensor. The hourly supply and return water temperature, the data is input into the integrated calculator to calculate the heat used by the user.
The heat meter can be divided into electromagnetic and ultrasonic, mechanical and differential pressure according to the different measurement methods of the flowmeter. Among them, the mechanical type has the advantages of low power consumption, good anti-interference, convenient installation and maintenance, and low price. Therefore, it is now applied more, such as France and Germany, the proportion of mechanical flowmeter is as high as 90%, but the mechanical type is Accuracy is greatly affected when there are many impurities in the water. The ultrasonic type is characterized by large measuring range, high measuring precision and less pressure loss, but it is susceptible to the degree of corrosion of the pipe wall, the content of foam or impurities in the water, and the vibration of the pipeline. The price is much more expensive than the mechanical type.
(2) Heat distribution table
The heat distribution meter is a meter that determines the user's heat by measuring the amount of heat dissipated by the user's heat sink. Its use is: in the central heating system, install a heat distribution table on each radiator, measure and calculate the heat ratio of each household, calculate the heat through the master meter; after the end of each heating season, work The person reads the meter and calculates the actual heat consumption based on the calculation. According to the measurement principle, the heat distribution meter has two types of evaporation type and electronic type.
a. Evaporative heat distribution table
The evaporative heat distribution meter consists of a heat conducting plate and a measuring liquid. The heat conducting plate is clamped or welded to the heat sink, and the glass tube containing the measuring liquid is placed in a sealed container, and the scale is engraved on the antifogging transparent film on the surface of the container. Measuring the evaporation rate of the liquid is closely related to the surface temperature of the heat sink. The higher the surface temperature of the heat sink, the faster the liquid evaporates. The amount of evaporation of the measured liquid during a certain period of time characterizes the integral value of the surface temperature of the heat sink to time, and actually reflects the heat dissipation of the heat sink.
b. Electronic heat distribution table
The electronic heat distribution meter uses sensors to obtain the hourly value of the surface temperature of the radiator and the temperature of the room, and then the measuring device is digitized by the A/D converter, and then the result is obtained by the calculation unit.
Compared with the electronic heat distribution meter, the evaporative heat distribution table has a simple structure, low cost, and no electricity. But correspondingly, its measurement accuracy is not as good as electronic.
Compared with the above two metering devices, the heat meter measurement is relatively accurate and convenient to manage, but the price is relatively expensive and the maintenance amount is large. The indoor system must be divided into households, and the single-tube downstream and double-tube type used for the old buildings. Not applicable, the original indoor system transformation is difficult. The heat distribution table is cheap and has no special requirements for the system. The old system modification is more suitable, but the result is affected by many factors, the test workload is large, and the calculation is complicated.

four. Temperature control equipment
Temperature control in the user's room is achieved by the radiator thermostatic control valve. The radiator thermostatic control valve is composed of a thermostat controller, a flow regulating valve and a pair of connecting members, wherein the core component of the thermostat controller is a sensor unit, that is, a warm pack. The temperature pack can sense the change of the ambient temperature and produce a volume change, which drives the valve spool to generate displacement, and then adjusts the amount of water in the radiator to change the heat dissipation of the radiator. The temperature setting of the thermostatic valve can be artificially adjusted, and the thermostatic valve will automatically control and adjust the water volume of the radiator according to the setting requirements, so as to achieve the purpose of controlling the indoor temperature.

Fives. Suitable for heat metering in the form of residential heating systems
5.1 Conditions for heating and heating systems suitable for heat metering
(1) The adjustment function means that the system must be adjustable, and the user can control the temperature according to the needs of the compartment. Whether manual or thermostat, the adjustable system is a prerequisite for heat metering.
(2) Control device corresponding to the adjustment function. This is a necessary condition to ensure the implementation of the adjustment function. Due to the adjustment of the indoor system, the original constant flow system becomes a variable flow system, and the system operating conditions vary greatly. If the corresponding control measures are not taken, the user's needs will not be met.
(3) Each household is charged according to the heat metering function. The heat consumption of each household should be measurable, and the user should charge and charge according to the heat, and mobilize the user's own energy-saving awareness.
5.2 Heating heating system form suitable for heat metering
In accordance with the above several conditions, the form of indoor heating system suitable for heat metering is roughly divided into two types: one is to use the traditional vertical up and down through the "single-tube" or "double-tube" system; the other It is a new form that combines the common supply and return water riser formed by the household heat meter and the independent household system.
1. Vertical single tube system
Renovation of the old downstream single-tube system is a spanning single-tube system, an adjustable system with a temperature-controlled valve, which is a very easy way to make the old system transformation. There are generally two forms: a two-way temperature control valve, and a three-way temperature control valve. The heat metering device of such a system is provided with a floor heat meter at the main entrance of a building or a community, and an evaporative or electronic heat distribution table is arranged on each radiator.
2. Vertical double pipe system
Due to the vertical thermal imbalance in the double pipe system, it used to be applied only to heating systems with 4 floors or less. Since the twin-tube system itself is adjustable, it is sufficient to install a thermostatic valve only at the inlet of each set of radiators. The heat metering device of this system is the same as the vertical single pipe system, that is, a building heat meter is installed at the main entrance of a building or a community, and an evaporative or electronic heat distribution table is arranged on each radiator. It should be pointed out that due to the large resistance of the temperature control valve, the vertical thermal imbalance can be well overcome after the temperature control valve is installed, and the application of the double pipe system is no longer limited by the number of layers.
3. A combination of a shared return water riser and a separate household system adapted to the household setting heat meter
The combination of the shared water supply and return riser and the separate household system means that each household is a relatively independent system, and each household's supply and return water pipes are connected with a shared water supply and return pipe, and the total supply at each household entrance is A household heat pipe is used for heat metering. The indoor heating system is in the form of floor radiant heating and radiator heating. The radiator heating forms are mainly horizontal parallel and horizontal series.

six. Outdoor heating system suitable for heat metering and its control
Due to the charge according to the heat, actively adjusting the temperature control valve to save heat will become the conscious behavior of the hot user, and the resulting change of the indoor system makes the heating system become the variable flow system from the original constant flow system. If the external network still adopts the original fixed flow control mode, it obviously cannot meet the needs and must be improved accordingly. 1. Outdoor heating system for heat metering
Because the heating system in China used to be a constant flow system, traditional conventional outdoor heating systems mostly use centralized heat stations. Sometimes, only one thermal station and one district heat station in a community can range from 50,000 to 400,000 m2. In the Nordic region where central heating is developed, the form of a small assembled heat station is often used in the entrance of the building. Compared with the two forms, the centralized heat station has low initial investment and is convenient for centralized management. However, when the user flow varies greatly, although the mutual interference between users can be eliminated by the inlet plus differential pressure controller, the pressure difference of the most remote user can be maintained by the speed regulation of the main circulation pump, but the pump is maintained. The operating point will vary over a wide range, resulting in a significant reduction in pump efficiency. The form of a small assembled heat station at the entrance of the building has a high initial investment, but the operating cost is low and the adjustment is flexible. At the same time, the stability of the system is increased, and the mutual influence between users, such as water leakage at the end and mutual interference, is reduced. Therefore, when determining the heating scheme, the economical and investment functions of investment and operation should be considered comprehensively to select the optimal solution.
2. Outdoor heating control method suitable for heat metering
Because the characteristics of different system forms are different, so what kind of control method should be adopted to analyze the specific problems. After implementing the heat metering charge, the indoor system can be divided into two categories: one is a shared riser and the indoor is a double pipe system, and the other is a vertical single pipe system with a spanning pipe or a shared riser and household The inside is a horizontal single pipe system with a spanning pipe. After the temperature control valve is adjusted, the impact of these two types of systems on the total flow is different. For the first type of system, in the case of constant pressure difference at the inlet, it is an ideal variable flow system. The external network should adopt the corresponding variable flow control mode. That is, while the quality adjustment is adopted, the method of controlling the speed of the water pump should be used to make the supply The thermal system achieves stepless variable flow operation. There are many ways to control the frequency conversion of the water pump. There are two suitable methods: one is to control the most unfavorable loop and the return pressure difference is constant; the other is to control the constant pressure difference between the inlet and outlet of the heat station. When the flow rate changes greatly, the former speed regulation energy saving effect is better than the latter, and the latter is easier to implement. In the second type of system, the total flow of the system is basically the same, so the fixed flow is required, and only the quality adjustment is performed. Generally, a flow limiter can be added at the user inlet to ensure the system's flow rate to meet the user's requirements. For a small distributed heat station, because the system is small, the user's requirements can be guaranteed as long as the secondary circulation pump is operated at a constant flow rate.

Seven. Heat metering method
The determination of the price of heat should take into account various aspects, including boiler coal consumption, pump power consumption, softening and deaeration of water, water consumption, wage income of heating personnel, equipment investment, depreciation and many other items. Also consider the heat exchange, secondary heat transfer and even three heat exchange quality pricing issues. The effect of different heating modes and fuel types on the price of hot water, etc. Urban heating is a large, closed and complex circulation system consisting of heat source, heat network and thermal users (indoor heating system). As long as it enters the heating period and is put into operation, it must run continuously without interruption. However, according to the laws of market economy In order to meet the requirements, it is necessary to conduct fair trade according to the actual heat consumption of the user to ensure heating. Taking into account these two factors, the hot fee pricing method should be divided into two parts: fixed expenses and floating expenses.
The fixed expenditure is not directly proportional to the energy production, that is, the cost that the user must pay when it is completely unused, mainly consists of the fixed assets investment for the normal operation of the heating network and the management cost of the heating enterprise. Such as land use, equipment investment, maintenance management, employee wages, etc. These fixed expenses provide users with corresponding usage features and are not subject to change depending on how they are used or disabled. This part of the investment should be concentrated according to the user's share of the building area or the price. Floating expenses are heat and heat charges, which are part of the change in energy production, that is, the more energy production, the greater the floating expenses. Such as fuel consumption, operating power consumption, system water, waste disposal, staff overtime pay, etc. This part of the cost must be allocated according to the actual energy that each user should measure through the cold heat meter.