The premise of the application of switching time area method is that each household must be an independent horizontal series system; Equipment selection and design load should be well matched; The capacity of cooling terminal equipment cannot be changed, that is, all residents in the whole building must adopt original radiators with uniform specifications, and personalized decoration changes are not allowed; There should be no obvious hydraulic imbalance between households; In particular, indoor heat dissipation terminals cannot be controlled in different rooms or zones, so as not to change the resistance of indoor circuits.
The shortcoming of the on-off time-area method is that it measures the total heat according to the on-off time of heating instead of the heat provided by the heating system, and there is a difference between them; If the radiator size matching is unreasonable, or the radiator is blocked, it will affect the measurement results and cause measurement errors.
I think the on-off time-area method can share the heat, but it can't realize the temperature control of the carriage; In fact, residents who are hot users can't set different temperatures for different rooms, so they can only choose an average value. This is the most fatal weakness of this heating metering and charging method.
As we all know, the goal of heating metering reform and the core idea of realizing the goal are "energy saving". The basic goal of heating reform is to convert heat energy into commodities, so as to establish a clear relationship between heating parties and consumers in the commodity market; The important policy goal of heating reform is to achieve the purpose of heating energy saving through reasonable heating price and charging system. For heat users, when the heat is measured, controlled and charged according to the user's heat consumption, energy saving depends largely on the user's behavior. To study and popularize household heat metering technology, users must be informed of necessary and feasible energy-saving behaviors without sacrificing their comfort. We shouldn't let residents' bedrooms, kitchens and bathrooms always set the same temperature. Therefore, indoor temperature control is a necessary prerequisite for residents to charge by volume, otherwise, charging by measuring heat will be unacceptable to users and will not promote energy conservation without means of saving energy for users.
4. Grasp the correct direction of research and development and application of heating metering technology.
Article 38 of the Energy Conservation Law of People's Republic of China (PRC) stipulates: "The State shall take measures to gradually implement the household heating metering charging system for buildings with central heating. New buildings or energy-saving renovation of existing buildings shall be equipped with heat metering devices in accordance with regulations. " Improving the energy efficiency of residential buildings and carrying out heating reform are still important policy objectives of China's next five-year plan. Heating metering and charging according to heat consumption are the main means to achieve the above two goals. The core idea of our research and application of household heating metering technology should be: heating metering reform is the focus of implementing building energy-saving tasks, and it is the most direct and effective measure to implement energy conservation and emission reduction; The correct direction is that the technical means of metering and charging serve the strategic goal of "energy saving".
Here, I quote a speech made by Vice Minister Chou Baoxing of the Ministry of Housing and Urban-Rural Development of China at the 20 10 conference on the reform of heating metering in northern heating areas, as the conclusion of this paper: The Technical Specification for Heating Metering points out in the paper that the mature technical route of heating metering at present includes household heat meters and heat distribution methods. Although two methods are mentioned in the description, namely, flow temperature method and on-off time area method, there is no supporting product standard for these two methods at present. Before the introduction of relevant product standards, only pilot projects and experiments should be carried out within a certain range, and it is not suitable for wide-scale popularization and application. However, due to the lack of guidance and supervision of relevant departments on heating metering technology, at present, not only the flow temperature method, the on-off time and area method, but also the temperature method that is not stipulated is also applied in various places. The large-scale application of these metering methods without product standards is bound to lay hidden dangers for metering and charging. "Minister Qiu will choose immature measurement methods in some places. "Some measurement technologies without product standards have been widely used in engineering, which has buried hidden dangers of disputes." As "one of the five obstacles to heating metering reform", it is thought-provoking; I hope the relevant departments can seriously think about it.
On-off time-area method is to share the total supply of buildings according to the water supply time of each heating system.
The specific method is: for indoor heating systems connected horizontally by households, room temperature on-off control valves are installed on the branches of each household to control the on-off of users' circulating water and realize the room temperature adjustment of households. At the same time, a room temperature controller is placed in the representative room of each household to measure the indoor temperature, set the temperature for the user, and transmit these two temperature values to the room temperature switch control valve. According to the difference between the measured room temperature and the set value, the room temperature on-off control valve determines the on-off ratio of the on-off valves in a control period, and controls the on-off of the on-off control valves according to this on-off ratio, so as to adjust the heat sent into the room, record and count the on-off time of each on-off control valve, and share the heat of the whole building according to the accumulated on-off time of each household combined with the heating area.
Figure 1: household regulation system of district heating terminal during switching period
When using the on-off time-area distribution method, we should pay attention to the following problems:
1) The quality and use of the temperature controller, switch actuator and other products should meet the requirements of relevant national product standards.
2) The on-off actuator should be installed on the domestic pipeline, and the temperature controller should be placed in the home room where it is not affected by sunlight and other heat sources.
3) Network connection control shall be realized between the switch actuator and the central processor.
4) The system supply, installation, debugging and post-service of on-off time and area allocation method shall be uniformly implemented by professional companies, and all parameters in the calculation process of user heat metering shall be well documented and the calculation method shall be clear.
5) Before the on-off period-area distribution method is implemented, the hydraulic balance between households should be adjusted to eliminate the vertical and horizontal imbalance of the system; In the process of implementation, the user's radiator cannot be replaced by itself.
2. Standard basis for "on-off time and area distribution method"
In some articles and reports introducing, popularizing and publicizing this method, the standard basis of this method is the technical specification for heating metering (JJ173-2009), an industry standard of the Ministry of Housing and Urban-Rural Development. The statement includes: "Technical Specification for Heating Metering" (hereinafter referred to as "Specification") stipulates a direct metering method and four allocation methods. The switching time area method belongs to the distribution method "; Switching time-area method is a kind of heat sharing measurement method selected in the Regulations. Among the four household heat measurement methods stipulated in the Regulations, "switching time-area method" is considered to be the most likely method to be popularized. It is the method recommended by the Regulations.
It must be pointed out that all the above statements are inaccurate. These statements are not the original intention of the Technical Specification for Heating Metering.
In Chapter 6 "Household Heat Metering" of Technical Specification for Heating Metering, except "6. 1 General Provisions", only "6.2 radiator heat distribution mode" and "6.3 household heat meter mode" are specified. It is pointed out that the mature technical route of heating metering only includes household heat meter and heat meter.
"Technical Specification for Heating Metering" only mentions the method of "switching time and area method" in the annex "Description of Provisions"; But it also points out the problems and shortcomings that should be paid attention to in this method. We must pay enough attention to these problems and deficiencies and study scientific and reasonable solutions. It should only be piloted and experimented in a certain range before, which is not suitable for large-scale popularization and application.