Abstract: An effective energy-saving heating system is equipped with appropriate control equipment, such as self-flow, pressure control valve. With the reform of heating metering and charging system, it is very important that the indoor heating system is equipped with the thermostat after the thermostat valve is properly equipped with control equipment. This article discusses the characteristics of the system before and after assembly of the thermostatic valve, and points out that the control equipment equipped with the thermostatic valve is instructive in the design and renovation. Keywords: Temperature control valve Self-flow control valve Self-operated pressure control valve Balance valve Introduction With the reform of the heat metering charging system, each radiator has begun to install temperature control valve. Therefore, heating operation with the constant adjustment of the user temperature control valve, heat network traffic constantly changing. This hot network as a variable flow operation, flow control initiative in the hands of users, and the heat company will be unable to predict and control the flow changes. In the case of variable flow operation of this thermostatic valve, the regulating control must be correctly installed in order to be effective. Otherwise, the system will not only meet the regulatory requirements, sometimes counter-productive. 1, regulating device 1.1, self-operated flow control valve The valve is characterized by the need for external power, depending on the characteristics of fluid flow, the upstream and / or downstream resistance within a certain range of changes, it can be through the pipeline pressure Changes to adjust their own opening, so that the basic flow remained unchanged. 1.2, balance valve From the adjustment of the basic principle point of view, the balance valve is actually a manual valve with opening instructions. In the balance valve upstream and downstream of each installed a pressure hole, used to measure the fluid pressure drop through the valve. When used, measured pressure drop and read the valve opening, you can count the flow through the valve. Its role is equivalent to the control valve and the equivalent orifice flow meter combination, so that each branch of the flow distribution to meet the requirements. When the total circulating pump variable speed operation, each branch of the flow distribution ratio remains unchanged. 1.3, Self-operated pressure control valve Self-operated pressure control valve features and self-flow control valve is similar, it does not require external power, only depends on the fluid flow characteristics, the upstream and / or downstream resistance within a certain range When the change occurs, it can adjust the opening degree by the change of the pressure in the pipeline, so that the change of the pressure drop of the fluid through the valve core can make up for the change of the pipeline resistance, so that the user's inlet pressure drop remains basically unchanged. Only three types of conditioning equipment discussed above are discussed, and these are not installed on the heating risers but at the heat entrance of the building. 2, not equipped with temperature control valve fixed-flow operation of the system control flow here said the constant flow refers to the entire heating network during the heat flow remain unchanged. 2.1, Straight network In general, the direct network to the thermal station for the sector is divided into the main network and branch network in two parts, from the heat source to the main heat station, from the heat station to the hot user for the network. 2.1.1 Main Network Regulation The main network control strategy is to adjust the opening of the water supply valve of the thermal power station so that the temperature of the return water of all the thermal power stations will be consistent. Main network should be equipped with microcomputer control, so you can guarantee the heating quality, while reducing operating costs. However, when the investment is limited or the heat network is smaller, the heat network is relatively stable in scale, the computer control may also be used instead of the simple adjustment method described in the following network. 2.1.2 Branch Network Adjustment Because of the high investment in thermal network computer control, it generally only controls the main network. For the network, there are many ways to adjust. 2.1.2.1, manual adjustment Manually adjust the relevant valves of each branch, so that each user's flow basically reaches the design flow. However, there is generally no flow measuring device on the branch, so the flow can not be directly observed to determine whether the regulation meets the requirement. There are two ways: by observing the backwater temperature of each branch, and constantly adjust the branch valve, the backwater temperature of each branch close to the same; or portable ultrasonic flowmeter to observe the flow of each branch to adjust, You can adjust the actual flow of each branch to the design requirements. The use of backwater temperature to adjust the need for longer regulatory cycles, because of thermal inertia of buildings larger; portable ultrasonic flowmeter adjustment is simple, but the need to purchase the appropriate equipment. 2.1.2.2 Self-operated Flow Control Valve Install a self-operated flow control valve on each branch or hot inlet and adjust the setting knob of the control valve so that its flow indicator meets the design flow requirements. In this way, each branch of the traffic flow can basically meet the design requirements. 2.1.2.3 Counterbalance valve Install counterbalance valve on each branch or hot inlet. Adjust the opening of counterbalance valve to meet the design requirements according to the adjustment method of counterbalance valve according to the designed flow of branch. In this way, the traffic of each branch can reach the design requirements during operation. 2.1.2.4 Self-operated differential pressure control valve Install a self-operated differential pressure control valve on each branch or hot inlet and adjust the setting knob of the differential pressure control valve so that the indicated value of differential pressure reaches the design pressure head requirements. In general, the design flow given by the designer and the actual required flow should be relatively close, so the two adjustment methods more accurate; and the capital pressure head not only with the design flow, but also with the pipe resistance coefficient, but The actual resistance coefficient of the branch may be different from the design value so that even if the actual pressure difference is adjusted to the design pressure head, the actual flow may not reach the design flow due to the difference of the resistance coefficient, thus resulting in uneven heating and cooling . 2.1.2.5 Comparison of Adjustment Methods For a heating network with a fixed flow in the whole heating season, several adjustment methods can be used. Manual adjustment and balance valve adjustment belong to the same type of adjustment method, in fact, are the first adjustment, that is, after the adjustment is completed to maintain the distribution of the flow rate of each branch to meet the requirements, but when the heating network to add new users or former users Changes in the situation, the flow distribution ratio has changed, and therefore need to be re-adjusted. At the same time, due to the coupling relationship between users in the adjustment process, for example, the user A traffic is adjusted to the design requirement value. However, when the user B is adjusted, the traffic of the user A changes due to the coupling effect, Also need to re-adjust A users. Therefore, the use of this adjustment method, in all serious coupling users must make decoupling. Self-operated flow control valve and self-operated differential pressure control valve with the two control methods are different, its role is not to ensure that the flow distribution ratio, but to ensure that the valve branch in charge of the flow (pressure) remained unchanged. Therefore, when a new user is added to the heating network, the traffic of the original branch is automatically adjusted to adapt to this change, so as to keep the traffic of the branch unchanged. The self-operated traffic of the original branch The control valve does not need to be adjusted again. Of course, all the adjustment methods must add some resistance to the system, and require the system to have sufficient adjustment margin. 2.2, networking and mixed networks From the control point of view, mixed network and the difference between networks is that the thermal power station on the second network water temperature control methods are different. For inter-networking, regulating the thermal station a network of valves to control the secondary network backwater temperature, regulating the secondary network circulating pump flow to control the secondary network of water temperature; for mixed network, also adjust the heat Station a network of valves to control the secondary network backwater temperature, but the secondary network of water temperature is controlled by adjusting the mixed pump flow. In a network or mixed network of a network, each thermal station is equivalent to a hot user, so a net is equivalent to a direct connection network, the direct connection network adjustment method is also applicable; for the second network, heat Station equivalent to the heat source, the network is equivalent to a direct network, the straight network regulation method is fully applicable. Therefore, the method of direct network adjustment can be extended to the network and network. 3, not equipped with temperature control valve phased variable flow regulation of the operation of the system variable flow control is the entire heating season is divided into several phases, in each stage of the flow remained unchanged, but the transition from one stage to another Phase, the flow changes. For example, the entire heating season is divided into the initial heating - cold period - the last three stages of heating, heat flow for the small flow network - large flow - small flow of three traffic values. Throughout the heating season, traffic is no longer completely fixed. Therefore, the adjustment method described in the previous section may not be all suitable for this mode of operation. As can be seen from the last section, as long as the regulation of direct connection is clearly stated, the adjustment of the interlinked network and the mixed network can be summed up one by one. Therefore, here only direct network analysis as an example. 3.1, self-operated control valve In this mode of operation, self-flow control valve is no longer applicable. Because self-operated flow control valve set flow rate are generally the system design conditions flow, which applies to the heating network throughout the heating season have remained the same mode of operation. For example, when the operating conditions are not in the design flow conditions, self-operated flow control valve will automatically adjust the function, so that the flow of the road as close to the design flow conditions. During the initial and late heating phases of the heating operation, the flow rate of the entire heating network becomes smaller, for example at 75% of the designed flow rate, the flow rate of each user should also be as small as 75%. In the case of users close to the heat source, the self-operated flow control valve senses that the actual flow rate (75%) is less than the set flow rate (100%), the self-operated flow control valve will automatically open to make the flow as close as possible to the set flow rate. As a result, the near-end user's actual traffic is greater than required and overheating, and far-end traffic is necessarily less than desired and too cold. Of course, in the cold period of 100% flow, self-flow control valve to ensure that each user's flow to meet the requirements, so that all users heating evenly. The self-operated differential pressure control valve has the same adjustment characteristics as the self-operated flow control valve, so the same happens in this mode of operation. In other words, self-operated differential pressure control valves are not suitable for this mode of operation. 3.2, Balance Valve Balance valve is very suitable for this mode of operation. Because when the balance valve is adjusted, it does not have its own flow, such as self-flow, pressure control valve according to changes in conditions for self-regulation function. Therefore, when the total flow changes, the balance valve can maintain a proportional change in the flow of each user. For example, when the total traffic is 75% of the design traffic, the traffic allocated to each user is 75%. Therefore, in this mode of operation, the balancing valve ensures that the flow distribution meets the requirements of use in each phase. 4, after the installation of temperature control valve system regulation and control After the implementation of the heat metering and charging, the indoor system can be divided into two categories: one is a shared riser and indoors double pipe system, the other is with a cross-tube Vertical single-tube systems either have common risers and indoor single-tube systems with straddles. After the thermostatic valve is adjusted, the impact of these two types of systems on the total flow is not the same. Figure 1 shows the control principle of the system. Figure A, B, N user thermal inlet control valve can be self-operated flow control valve can also be self-pressure control valve or balance valve, the thermostatic valve indicates that all or part of the thermal user internal temperature control valve, Not drawn radiator. The indoor system can be any of the two types of systems described above. 4.1, there is a shared vertical pipe and indoor double pipe system With the indoor load changes, the thermostatic valve will automatically change. This flow through the radiator also will change, which means that the heat network flow changes at any time. 4.1.1 Hot inlet control valve is a self-operated flow control valve Self-operated flow control valve is the function of maintaining the flow of the pipeline as much as possible when the conditions change. Temperature control valve installed pipeline flow is constantly changing, it is clear contradictions with the role of self-operated flow control valve. If installed in the pipeline valve temperature control valve and then self-contained flow control valve on the regulatory role of harmful and no benefit. Figure 1, when the indoor load decreases, the temperature control valve automatically off small, the corresponding pipe flow should be reduced; but if the pipeline has a self-flow control valve, the self-flow control valve reduces the flow of perception will automatically open Large, so that the increase in the flow of the pipeline to maintain its flow of the same purpose. At this moment, the relative increase of the pipeline flow (actually keeping the original flow unchanged) will lead to the further closing of the thermostatic valve, thus forming a cycle, finally leading to the thermostatic valve closing to the minimum, while the indoor temperature may still be higher than the requirement ,vice versa. Therefore, the installation of temperature control valve has a common riser and indoors as a double tube system can no longer be loaded with self-flow control valve. 4.1.2 Hot Inlet Control Valves Balance Valves Balance Valves actually act as a primary regulator. The initial adjustment of the balancing valve is based on the flow rate of each pipeline under the design conditions. When the initial adjustment of all balance valves is completed, and the pipe resistance coefficient will not change, the flow distribution ratio of each pipe will remain unchanged. When the pipe resistance coefficient changes, then the flow distribution ratio also changes. Thermostatic valve action, in essence, is the temperature control valve resistance coefficient has changed, then the corresponding pipeline traffic also changed. Therefore, the role of temperature control valve and balance valve does not conflict. Temperature control valve installed, the actual opening of the temperature control valve changes with the load changes. If the user load on the B pipe in FIG. 1 is increased, the corresponding temperature control valve on the pipe opens large, resulting in an increase in the flow of the pipe. However, if there is no change in the load of all users except for the B pipeline, the thermostatic valves corresponding to them and the required flow should not change. However, due to the change of the flow of pipe B, it is bound to affect the increase of the total flow, which in turn causes the flow of other pipelines such as A and N to change. It has been assumed in front of the user load except B have not changed, so A, N pipeline temperature control valve should not be action. However, due to the influence of the change of the flow of the B pipeline, the thermostatic valves on the A and N pipes must also be operated to make the necessary adjustments. In other words, installed counterbalance valve still exists after the interaction between the pipeline, prompting balancing valve constantly adjusted action. On the other hand, if users other than N-pipe require traffic increase, there is a possibility that the total flow will be too large to cause insufficient capital pressure at N-users, even if the temperature control valve on N-pipe is open to the maximum, It may also not meet the requirements. In short, the balance valve installed at the beginning of the adjustment than the blind manual initial energy saving better to maintain the temperature control valve to play a normal role. However, the balance valve can not eliminate the mutual coupling between the branches, and sometimes can not meet the regulatory requirements of the temperature control valve. 4.1.3 Hot inlet control valve for the self-pressure control valve Self-operated pressure control valve and temperature control valve can be well coordinated to ensure the normal operation of the thermostatic valve. Figure 1 corresponds to the user A load decreases when the temperature control valve is closed, the corresponding pipe flow decreases, resulting in a decrease of the total flow, the system pressure chart changes. As shown in the solid line in Figure 2 does not adjust the temperature control valve before the pressure distribution, △ P for the user required capital pressure head; dotted line indicates the temperature control valve after the adjustment of the water pressure distribution. Due to the reduction of total flow, the pressure loss on the mains also decreases, and the external pressure provided to users A by the external network increases to ΔP '. If user A does not install a self-operated pressure differential control valve, the temperature control valve will be further closed due to the increase of the pressure head provided by the external network, thus repeatedly forming a positive feedback so that the temperature control valve can not function normally. However, if equipped with self-operated pressure control valve, self-operated pressure control valve can be automatically adjusted according to the pressure drop off, the pressure control valve consumes 2 times △ P ", so that the external network to provide users with funding Indenter (△ P'-2 × △ P ") remained basically unchanged, still equal to △ P, so there will be no positive feedback on the temperature control valve. 4.2. Vertical single-pipe systems with cross-over pipes or horizontal single-pipe systems with common risers and indoor cross-over pipes Vertical pipe systems with straddle pipes due to thermostatic valves allow flow through the heat sink Indoor load changes and changes, but the diversion effect across the pipe makes the total flow of the riser remained essentially unchanged. Therefore, at this time the heat network is basically running at a constant flow. In this way, the system for the use of regulating valve requirements, as previously described constant flow operation system, the use of self-operated flow control valve is the most suitable. 5 Conclusion 5.1, in order to make the heating network to ensure that users meet the heating requirements, the heating network should have the correct regulation system. This includes two meanings, on the one hand the heat network should be equipped with the appropriate regulatory equipment; the other hand, the heat network should also be equipped with the correct regulatory strategy, both indispensable. 5.2, the user is equipped with temperature control valve, the heat network operating mode has a great impact and significantly different requirements, and this difference is transformative. 5.3, not equipped with temperature control valve constant flow operation system Although you can use self-flow, pressure control valve or balance valve, but relatively speaking, self-flow control valve is more appropriate. Because the balance valve in the initial adjustment than the self-flow control valve easy to understand, and in the use of self-operated pressure control valve, because there is no accurate pipe resistance coefficient, the lack of accurate pressure adjustment settings. 5.4, ​​not equipped with temperature control valve phased variable flow operation system can only use the balance valve, if the use of self-flow or pressure control valve, when the system after the variable flow will appear near the end user overheating, remote users not hot The phenomenon. 5.5, temperature control valve installed double pipe system should be equipped with self-operated pressure control valve, and can not be installed self-operated flow control valve or balance valve. Such as the use of balancing valve, easily lead to the interaction between the thermostatic valves; and if the use of self-flow control valve will form a near-subcooling heating uneven. However, it is more appropriate to use a self-operated flow control valve to install a temperature control valve with a single pipe system that crosses the pipe. 5.6, regardless of which of the above systems can be applied to computer control, but for different systems, control strategies should be different. Taking into account the investment and management, the best system should be a network of computer control and secondary network reasonable use of the combination of the above adjustment equipment. References 1. He Ping, Sun Gang, ed., Heating engineering, China Building Industry Press, 1993 2. Zou Yu, Xu Wei, suitable for heat metering outdoor heating system control methods and analysis, HVAC, 2000, 30 (1): 57 ~ 59 3. Zhang Xihu, Huang Tao, residential central heating system of household heat metering and charging a number of issues, HVAC, 2000,30 (1): 2 ~ After the measurement of heating pipe heating pipelines, HVAC, 2000,30 (5), 83 ~ 76
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