In increasing urban construction, high-rise buildings account for a large proportion. The heating system of high-rise buildings, from the calculation of thermal load to the choice of system form, has many differences compared to ordinary multi-story buildings. To sum up, there are the following points: The calculation of heating load of high-rise buildings must consider both thermal pressure and wind The impact of pressure; high-rise building heating system should pay special attention to the impact of hydrostatic pressure; high-rise building heating system vertical misadjustment is more serious.
Therefore, the above factors must be taken into consideration when selecting the form of heating system for high-rise buildings and the connection to external networks.
1 High-rise building heating system forms The system types commonly used in actual projects are as follows: As shown, the system is indirectly connected and is applicable when the water temperature of the heating network is higher than the user-designed water temperature. According to the height of the building, it can be divided into upper and lower zones. The lower zone (low zone) can be directly connected to the external network, and the upper (upper zone) is exchanged with the water-water heat exchanger for heat exchange and isolated from the external network. Its advantage is that it can avoid the hydrostatic pressure in the high-level area. As shown, the system is directly connected, and it is suitable for the situation where the heating network and the thermal user design the same water temperature. Its function is the same as that of the heat exchanger insulation layered system, but the isolation mode is realized by the partial flow of the low tank overflow tube. Compared with heat exchanger insulation layered system, its cost is lower. However, because the tank is open, it may increase the corrosion of the system.
Valve isolation layered system As shown in the figure, the user's high area and external network are isolated from the valve provided by the supply and return pipes. The water supply pipe is generally added with a check valve, and the back water pipe is isolated by a pressure regulator before the valve or a pressure reducing valve with a closing performance, and an automatic shut-off valve linked with the circulating water pump may also be adopted.
As shown, the system has a set of ascending and descending risers in the same room in the vertical direction, so the average temperature of the radiators in each layer is approximately equal, so that vertical misalignment can be avoided. Because the heat sink of the two-wire system adopts a serpentine tube or a radiant plate structure, its own pressure bearing capacity is high, but the system itself has no insulation measures, and the influence of high hydrostatic pressure on the radiator in the low zone still exists.
As shown, the system is similar to the vertical two-wire system except that the average temperature of the radiators in the rooms in the horizontal direction is approximately equal. Because each layer is separately provided with a regulating valve for layered adjustment, vertical misalignment can be improved.
As shown, the system is similar to the horizontal two-wire system in that all layers of regulating valves are used to improve the vertical misalignment. The difference is that the number of horizontal pipes is different, and the horizontal double lines must be two. The system can be used for 1 meter. root.
As shown, the main role of this system is to improve the vertical misalignment, which is the same as the system 4 and still cannot eliminate the influence of hydrostatic pressure in high areas.
2 Selection principles of heating system form The determination of high-rise building heating system should mainly consider two factors, such as improving vertical misalignment and resolving low-zone overpressure phenomenon.
Improve the vertical misadjustment can be solved by the characteristics of the system itself, and can also be solved by the adjustment function of the system.
For the former, the heating system itself is required to have the function of improving vertical misalignment without the need for additional adjustment measures. Strictly speaking, only the vertical two-line system has such a function, and the hierarchical system can only guarantee that the two (or more) partition systems can avoid misalignment between the upper and lower partition systems, and between the floors inside each partition. , there may still be different degrees of disorder.
single. For the latter, the dual-tube hybrid system is realized by some adjustment means and equipment due to its function of improving vertical misalignment. Therefore, under the premise of better operation and management, this kind of effect of improving misalignment is better. Both the horizontal two-line system and the hierarchical horizontal series system meet the regulatory requirements by adjusting the adjustment valves of each floor or installing the orifice plate to achieve the flow distribution between each layer. The single-double hybrid system, because each layer radiator is a double-pipe system from a local point of view, can adjust the valve of each branch pipe to change the flow distribution. Of course, these adjustment methods are more complex.
Solving the low-zone overpressure can be divided into two aspects: overpressure and system overpressure.
If the heating system is an independent system, it is only necessary to solve the system without overpressure in the low zone. If the heating system is connected to the entire residential heating network, in addition to ensuring that it is not overpressured, it is also necessary to consider that other buildings in the community cannot overpressure, that is, to isolate the high-rise building heating system from the external network.
For an independent high-rise heating system, since there is no need to be “insulated†from the external network, the overpressure problem is generally not considered when the building does not exceed 40 n. For buildings over 40 n in height, consider setting up steel in the lower layers. Radiator or two-line system, the use of high pressure pipe features. Of course, the best way is to layer heating, high and low areas do not interfere with each other. For the high-level heating system connected to the community outside the network, to solve the problem of overpressure Therefore, it is necessary to adopt different measures of "insulation" to avoid the influence of hydrostatic pressure in high areas on the low-lying areas. Since most high-rise buildings have been built in recent years, more ordinary buildings (especially those with some low-lying buildings) have been formed before. Therefore, it is not possible to use the individual high-rise buildings in a residential area to build the original buildings. Some building radiators are replaced in whole or in part.
In the several system forms described above, only the heat exchanger insulation layering system is indirectly connected, and the rest of the systems are directly connected. As far as the actual situation is concerned, the use of heat exchangers to isolate layered systems is more common. In addition to the aforementioned advantages, the system uses indirect connections and is relatively easy to operate and manage, especially for thermal power plants or large-scale district heating systems. The leakage of water by the user will not affect the primary heat network.
During the renovation and construction, especially the high-rise buildings added in the original residential quarters are limited by the water temperature of the original heating system, and the indirect connection using heat exchangers is not economical. At this time, the use of double-tank insulation is more common. This kind of system operation management is simple and low cost, but must leave a suitable space to arrange the water tank in the system.
In addition, in recent years, due to the appearance of pre-valve pressure regulators and proportional pressure reducing valves, some places have begun to try to use the above two valves to isolate and achieve better results. However, these two types of valve isolation have some technical problems that require attention in design and operation.
In order to improve the vertical misalignment, hierarchical horizontal series and single and double tube hybrid systems have also been adopted, but some problems in the operation management and design calculations in some places have affected the operational effects of these two systems.
As for the two-wire system, it is still rare.
The problem of several types of valve isolation systems has been paid more and more attention due to the simple structure of the valve isolation system, convenient construction and low cost. In recent years, the pre-valve pressure regulator and other types of pressure reducing valves have appeared. The application of this system brings a broader perspective.
Pre-valve pressure regulator The function of pre-valve pressure regulator is that when the system is running, the valve is open, and when the system stops running, the valve is closed to achieve the requirement of insulating the static pressure. The valve closing is achieved by the spring in the regulator. The pulling force should be greater than the hydrostatic pressure of 3-5mH0. When the network circulation pump stops running, the spring tension exceeds the hydrostatic pressure of the system, so that the valve flap is pulled down and the valve hole is closed.
When the circulating pump is running, the dynamic pressure of the return pipe exceeds the spring tension so that the valve flap is opened and the valve hole is opened. Obviously, the pre-valve pressure regulator is used under the condition that the pressure of the return pipe at the installation position must be greater than its hydrostatic pressure of 3-5 mH2. Therefore, a suitable constant pressure must be used when this type of isolation is adopted. For the constant pressure of the steam drum and the constant pressure of the water supply pipe in any way (the static pressure line is higher than the dynamic pressure line), this type of insulation cannot be adopted.
For a “buck-operated†system where the constant pressure point is set on the bypass pipe to make up the water and pressurize the constant pressure, this isolation mode cannot be used when the dynamic pressure line of the return pipe is lower than the static pressure line.
3 Currently used high-level heating systems and connection methods are used to control dynamic pressure and set high-voltage lines. However, it still requires bookmark1 for the near-heat source end. When using the general circulation pump suction inlet water supply and constant pressure, back to the nuclear return pipe dynamic pressure lines and static pressure lines Height difference, when the height difference is less than 3-5mH2, it still cannot operate normally.
It is very important to check whether the pre-valve pressure regulator can be used for the above-mentioned several different pressure regulators. It should be specifically mentioned that the backwater at the branch pipe where the pre-valve pressure regulator is installed should be used in the calibration. Pressure check.
The pressure relief valve used for "isolation" should be equipped with the feature of automatic shutdown during outage in addition to decompression during operation. There is a proportional pressure reducing valve, assuming that the outlet end piston area is A2, the outlet pressure is P2; the inlet end piston area is Ai inlet pressure is Pi. the outlet end piston area A2 is larger than the inlet end area Ai, and the system stops running. The water is stopped at the outlet and the pressure P2 at the outlet increases. When P2 is in PrAi, the valve closes immediately to achieve isolation.
Specific implementation of closed off the valve can be used normally open solenoid valve, when installed with the circulating pump CHAIN, circulating water pump solenoid valve is always open, back to the external network through the solenoid valve, when the circulating pump stops running, the solenoid valve Linked shut down, user backwater and external network cut off.
5 Suggestions for Insulating the Valve Several high-level heating systems are isolated from the valve. All of the above valves are installed in the user's water return branch pipe, while the check valve is installed on the water supply branch pipe; Sexuality, before the valve pressure regulator, must be limited to the applicable constant pressure mode can be applied.
Isolated from the pressure relief valve, note that not all pressure reducing valves can act as isolation, and some pressure reducing valves and throttle valves are throttled during operation to reduce pressure, but there is no water flow to stop the shutdown performance. Very important.
Some manufacturer's instructions that a valve can reduce dynamic pressure, can also reduce static pressure; some information even describes the use of a certain valve to reduce the static pressure to how many meters of water column. In the heating engineering, so-called static pressure generally refers to the pressure when the circulating water pump stops running. At this time, as long as the water in the network is connected, the entire network hydrostatic head is equal. Therefore, unless the valve is closed off, any valve cannot reduce the static pressure when the upper and lower layers of water are connected. Therefore, the so-called reduction of static pressure is inappropriate, and the user must understand the working principle of the valve when selecting.
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