【 Weak current College 】 air-conditioning end active variable flow hydraulic balance analysis---Power By 【 China power house network 】

1. heat source Active variable flow and terminal active variable flow

Heating and air conditioning system circulating water as htm media, its flow is consequential to the changes in the load changes. In General if the load is always consistent growth, flow changes should be consistent and other than at any time. To save the circulation pump power consumption and heat source Active variable flow measures:

Multiple pumps, small pumps, pump configuration changes, such as variable speed measures. But its variable flow is with the outdoor temperature parameters continuously changing or dispute phase changes by date.

Another variable flow conditions are the main issues discussed today. When the end of the load out of proportion, random changes, then the system must be in the end of a traffic control measure. Residents on the requirements of the indoor parameters through control (heating temperature control valves, hand valve, air conditioned indoor parameter control of electric control valve) flow requirements, the sum of the flow requirements at the end of the formation of heat flow. This variable flow condition is the end of the main variable flow.

Terminal active variable flow in the following hierarchy of concepts:

1. flow change depending on the end needs, heat circulating pump control facilities cannot predict the flow of change, but be aware of changes in the flow.

2. a period at the end of the load without significant changes, the period of circulation of variable speed measures for constant flow variable head. That is, each instantaneous flow may be changing, but this change decided to end requirements. Circulation pump speed is in the end decided on the basis of flow, the smallest possible lift to move the line to save energy.

2. terminal active variable flow engineering significance

Heating projects in the past by building area to receive heat, heat the user does not have the initiative to change the load and traffic demands, some large heating a ride to achieve energy-saving purpose take heat source flow control measure, with typical characteristics of the active flow heat source. In terms of thermal charge, water system has a terminal active variable flow characteristics. For metering and charging to improve the quality, energy-saving heating discourse, Dario will not repeat them. For metering and charging, maximum thermal load does not occur at the same time, if you take a valid end active variable flow measures can effectively scheduling flow requirements, improve the heat source for heating capacity. This is the charge for heating enterprise's best interests.

Air conditioning in every room cooling load not possible consistent growth. But air conditioning Terminal output load larger depending on the wind. Instead of water, many are not demanding a ride to air conditioning cooling load, heat pump, single pump operation, and in winter the two sets of circulation pump, heat source Active variable flow measures. Here, in effect, energy saving, cold source scale to the end of the stream of significance:

1. air conditioning effects

For hospitals and pharmaceutical factories, clean air conditioning a range, to ensure the purifying effect of air flow almost are immutable and can only use Terminal active variable flow measures to change the end of the load.

For a general load comfort air conditioning, low airflow caused during necessarily lower cooler surface temperature is too low due to excessive dehumidifying, indoor environment is too dry, reduces comfort. Secondly, the reduction of air flow while leading export temperature low, Jet air buoyancy reduces, rather, to reduce and buoyancy can lead to Jet landing to occupants ahead of the space, resulting in low temperature and high velocity cause uncomfortable feeling. And terminal active variable flow can be a good solution to this problem. In the past in a process uses high-grade tee-regulation, despite the resolution of the issue of comfort, but gave up energy-saving and reduce the size of the cold source.

2. energy-saving

First of all, on the one hand, excessive moisture on the one hand, reducing comfort causes unnecessary cooling load increment.

Second, the cooler uninstalls automatically is in low temperature conditions, the actual not cooler maximum efficiency.

Thirdly, regardless of whether or not to take variable pump, also run always energy-low flow rate. If you use a variable measures its energy-saving effect is very significant.

3. cold source scale

Only a valid Terminal active flow measures, to achieve effective scheduling of load. On this basis, in order to fully take into account cooling loads and incidents effectively reduce cold source machine sizes, including chillers and circulation pump.

3. terminal active dynamic variable-flow hydraulic balancing and application of pressure control valve

Terminal active variable flow of active control means, of course, is a two-way electric control valve, electric regulating valve can only achieve variable flow purposes cannot rely on it for far different hydraulic balance. Otherwise, it means that the proximal electric regulating valve in the design flow is not under full opening of the State, while the small flow is uncontrollable State. Secondly when powered on, and cooling load increase appeared at room temperature for a time series of near and far, the sequential process also can be very long. Second, should greatly improve the stability, avoid hydraulic regime an impact load adjustment at the end of the near end of flow, thereby causing load does not change the passive adjustment at the end of the action. Third, the circulation pump of variable speed control does not change the speed at the end of the flow direction. procedure

To achieve these three objectives with balance device, only self-operated pressure control valve. Distance imbalances are static balance problems, its solution means a lot, such as reduced diameter, using static balance valve. But these purely static balance means, affect the dynamic adjustment of performance: such as reducing valve power of electric control valve adjustment characteristic deterioration; you cannot improve or even reduce hydraulic a condition stability; pump speed control and electric control valve interaction, not a one-way transmission process.

Pressure balance valve adjustment process: close some branch lines allow circulation pump flow meet was transferred branch lines of design flow. Allows the transfer of branch electrically adjustable over manual full open state. Test Terminal traffic, by adjusting the control pressure value so that at the end of the flow reaches design flow value. Cycle step-by-branch completed balance adjustment.

This balance debugging results means that each terminal device regardless of the distanceNear maximum realization of design flow. But at the end of a small flow requirements by electric regulating valve automatic control. This means that the control pressure adjusing is adjustable differential pressure required. Each warm-engineers are clearly understand that we cannot inform terminal device design flow of the actual resistance of true value. And pressure adjustable minimum should be adjusted from 10kPa 100kPa.
In addition to a description of the collateral is in the end a self-operated pressure control valve, to reduce the diameter of the proximal extension to save the tubing. In a pressure control valve, the unnecessary in any pipeline deliberately constructed reverse return system.

4. terminal active variable flow pump speed control when

Terminal active variable flow pump process is not a variable flow but variable head. Its variable speed signal value can only be a distal pressure differential signal, if the system does not have the absolute most negative loop when using secondary adverse desirable loop of far turbulent pressure as variable speed signal. The control logic for all distal pressure difference is greater than the set value either pump spin down, the pressure difference is less than the set value water pump. In the Nordic's heating technical literature in 3-8 distal pressure differential signal, in the little red school law on air conditioning circulation pump speed control and elaboration.

Use remote pressure differential signal for two reasons: one is the differential rate of change of proximal end. The second is much pressure control point of the line flow decreases, the control point of the actual needs of differential pressure is less than the control point control point of the set pressure differential. Also this is not the case there are further reduced also pumps. The most distant point pressure control variable so that the energy-saving pump spin may reach the maximum.