Heating hot water supply system is the hydraulic balance necessary calculation, but if the lack of quantitative regulation there will still be the hydraulic imbalance, resulting in room temperature uneven overheating of proximal end of cold, this phenomenon is quite common in the district heating network. "Heilongjiang Province residential building energy-saving 65% of the design standards" 5.2.19 "to the mandatory provisions of outdoor pipe network should calculate the hydraulic balance, pressure loss between the parallel loop values should not be greater than 15%, but the calculation of hydraulic balance outdoor pipe network is not up to the requirements, should be manual hydraulic balance valve is arranged in the thermal power station thermodynamic entrance and buildings". So in the design will often use hydraulic balance valve.
Hydraulic balance valve setting
Circulating pump according to the most disadvantaged loop configuration, relatively small down the rest of the loop pressure, called "favorable loop". Because of the different loop pressure drop, at run time, the system will automatically assign flow pressure drop of each loop, resulting in the same parallel "loop outside the most disadvantaged loop" of the flow, so that the water system in the large flow and small temperature difference in operation. In order to achieve the loop static hydraulic balance, maximize favorable loop flow velocity in the economic specific frictional resistance range, the pressure drop and the most disadvantaged loop pressure drop decrease difference to outdoor pipe network balance. Loop pressure drop exceeds 15%, provisions should be set of hydraulic balancing device. In recent years, as the hydraulic balance valve hydraulic balancing device is widely used. Hydraulic balance valve is divided into static, dynamic two.
(1) the static balancing valve is a manual control valve with opening reading vernier locking device and flow characteristics are known, has shut off valve function. Install this valve can no longer be set to traditional cut-off valve. Early in the system adjustment, according to the design of controlled object the required flow, pressure drop, the valve core of the manual accurately adjusted to the needs of opening and locking, so that the pressure drop of the parallel loop is adjusted to drop the most disadvantaged loop values make water flow distribution to parallel the loop device. According to the design requirements of rating.
In the project, because the heating water system design theory calculation value often has certain error between the actual value of pressure drop and pressure drop, and equipment to design equipment on-site installation are not the same, and the installation is often based on field modifications of pipeline. To adjust the valve according to the design flow rate and pressure drop provides, its accuracy has deviation, hydraulic balance which requires lots of tedious repetitive debugging can cause the system to the coupling, which is more difficult in engineering practice. Set the static balance valve and set flow valve, the traditional characteristics of good throttle valve compared with the obvious advantage in the debugging process.
(2) the dynamic balance valve. Can be divided into self-operated flow balance valve, self-operated pressure balance valve. Self-operated flow balancing valve is an area of the flow with the valve at both ends of the pressure difference change of self-power adjusting device. As long as the pressure difference across the valve in its working pressure range, the valve opening degree will change with the change in the role of differential pressure across the valve, the valve flow constant. If the pressure is less than the minimum working pressure or greater than the maximum working pressure, each component has no dynamic valve action. The valve is equivalent to a throttle orifice, flow with pressure increasing. Self-operated flow balancing valve can be loop, in need of vertical pipe flow, the level of pipeline system and equipment, pipes shall not be located in variable flow.
Self-operated pressure balance valve should be set in the variable flow system. When the external or object flow change can change the spool position independent adjustment object for the return pressure constant depends on the spring force the valve. Through the pre-tightening force regulating valve spring can change the pressure difference value. Between the variable flow system of differential pressure balance valve often in district heating the building water supply and return pipes, sub-catchment.
Although the self-operated pressure balance valve and electric control valve arranged on the end of the equipment load regulation is an ideal balance measures, but the current differential pressure balance valve price is still too high, so set the hydraulic balance device and the adjusting scheme should be based on project investment and the room temperature is allowed to fluctuate requires reasonable selection, which not only to meet the comfort requirements both energy saving and economic rationality.
As long as the water system design is reasonable, automatic adjusting device is configured properly and carefully debugging, practice has proved, heating system can meet the design requirements.
The parameters of hydraulic balance valve adjustment
Installed in the water system of the static or dynamic balance valve, must carry on the debugging can realize static and dynamic hydraulic balance. Debugging should be based on the installed system (not the design drawings on the actual parameters).
(1) the static balance valve, is arranged in the most disadvantaged loop, through the design flow is fully open, the rest of the static balance valve loop (diameter and pipe diameter of the same debugging) according to the design flow and pressure required to determine the spool opening required to be controlled object, all through the design flow pressure difference is the same, the entire system is in static equilibrium state.
(2) the self-operated flow balance valve, in order to achieve the object constant flow, debugging should be according to the controlled object required to determine valve differential pressure range constant flow, the valve in the pressure difference between the minimum and maximum differential pressure flow constant, to ensure that the dynamic flow balance.
(3) the self-operated pressure balance valve. In order to ensure that the object constant pressure difference, if the valve is located in the most disadvantaged loop, through the design flow when the valve is fully open. But in the rest of the loop, debugging should be based on the loop through the design flow when the valve opening required to ensure that the loop pressure difference constant desired value. Favorable loop for when necessary, in order to improve the performance of the valve, can also according to the requirements of design flow and pressure difference, the valve is in full open or close to the fully open state. The right valve caliber choice accordingly.
In the setting of hydraulic balancing device, designers in order to meet the system debugging except in the drawings that should also put forward the adjustment parameters. However, these parameters are calculated value, is theoretical, practical installation according to the construction site of the pipeline, equipment position often to modify. The pressure drop and the design of equipment value often also have differences, which may cause the design theory, parameter changes. If only according to the theory of value of water system debugging completed, it is very difficult to realize the true hydraulic balance. This is the current number of water system was installed in many expensive of all kinds of static, dynamic balancing valve and hydraulic system balance is still not ideal is one of the important reasons.
Water system design of heating, should be reasonable and uniform layout loop, position appropriate hydraulic balance, strict calculation, lay the foundation for the hydraulic balance system. According to the hydraulic balance valve function, the characteristics of water system, heating comfort, cost and energy requirements selection function and model, price reasonable balance valve. Manual hydraulic balancing valve should be based on the valve flow capacity and the pressure difference across the selection of balance valve and the opening diameter. Self-balancing valve shall be carried out according to the flow of selection. Self-operated pressure control valve should be according to the required pressure difference control valve selection and pipe of the same size, and should ensure that no less than the maximum flow design. Hydraulic balance valve must be according to the required parameter system of scientific installation, repeated debugging, can realize the static, dynamic balance of water system.
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