Weak current College】 【HVAC water balance analysis.

<br> In building HVAC engineering, hydraulic balance of regulation is an important issue. This article proposes a static hydraulic balance and dynamic hydraulic balance of concepts, combined with two hydraulic balance of features, analysis of the constant flow system and variable flow system several .typical ways of hydraulic balancing equipment selection and implementation of the hydraulic balance. <br> 1. hydraulic imbalance and hydraulic balancing concepts: in hot water heating system and air conditioning frozen water system of the thermal (cold) the user's actual flow and design requirements .flow between consistency is referred to as the user of the hydraulic failure. <br> The extent of hydraulic offset can be used for actual flow and design requirements flow ratio X, hydraulic offset X said. <br> X = QS / QJ (QS .: user's actual flow, QJ: users of design flow) <br> The hydraulic balance refers to the Internet in various heat users in other hot user flow changes keep itself flows unchanged, usually heat hydraulic stability coefficient of user r. <br> r .= 1/XMAX = QJ / QMAX <br> (QJ: users of design requirements for flow, QMAX: users of maximum flow) <br> 2. hydraulic imbalance and the hydraulic balance of classification: <br> 1. static hydraulic imbalance .and static hydraulic balance: <br> Due to the design, construction, equipment, materials, and other causes of system pipe characteristic resistance ratio and design requirements for pipe characteristic resistance ratio is not consistent, allowing the system to user's actual flow and design flow .is not consistent, causes the hydraulic failure, the system is called static hydraulic imbalance. <br> Static hydraulic imbalance is steady, fundamental, is inherent in the system itself, is currently China's HVAC water system hydraulic imbalance. <br> Through the pipeline .system, an additional static hydraulic balancing equipment (hydraulic balance valve) on system pipeline features resistance ratio into <br> Line regulation, with the design requirements of pipeline features resistance ratio consistent, this time when system throughput reached the design flow, the flow of .the terminal equipment are at the same time meet the design flow, realization of static hydraulic balance. <br> 2. dynamic hydraulic imbalance and dynamic hydraulic balance: <br> When the user changes the valve to open degree water changes, other user's flow .is consequential changes, deviations from the design flow, causing the hydraulic imbalance, called dynamic hydraulic imbalance. <br> Dynamic hydraulic imbalance is dynamic, changing, it is not inherent in the system itself is in the system is running. <br> Through .the addition of the pipeline system dynamic hydraulic balancing device (flow regulator or pressure regulator), when other users of the valve to open degree change, through dynamic hydraulic balancing equipment shield to make their own traffic and not consequential changes to terminal equipment flow does not .interfere with each other, to achieve dynamic hydraulic balance. <br> 3. constant flow system hydraulic balance analysis: constant flow hydraulic balance system is common in HVAC design of hydraulic systems, each running process in the system of flow has remained virtually unchanged. .Commonly used mainly in the following three forms: <br> 1. full set flow system: <br> Fully fixed flow system means the system does not include any dynamic valve, system in preliminary debugging completes the valve to open degree is not required to .make any changes, the system always remain constant throughout the flow. Fully fixed flow system mainly apply to terminal equipment shall be regulated by traffic to the system, such as fan coil units at the end of a three-speed switch control speed and uses the .VAV air handling unit of air conditioning systems and system requirements are low, simply adjust the climate heating water compensators to meet the basic needs of the heating system, etc. <br> Fully fixed flow system hydraulic offset only static, dynamic hydraulic offset does not .exist, so you only need to install the relevant parts of the static hydraulic balancing device. Usually set in the system House water hydraulic balance valve installed on (as shown in Figure 1); for chilled water system, you can structure the layer level back .to the main hydraulic balance valve installed on. <br> For some systems, although it does not contain any dynamic valve, but will it be available through other non-regulated discharge means, so in actual operation users because the room too cold or too .hot but change the valve to open degree thus changing the flow, so you can think of this system is between fixed and variable flow. <br> 2. single-pipe-line (with by-pass pipe) heating systems: <br> .Single pipe-line heating system including vertical double horizontal single pipe-line systems and vertical single-pipe system, etc. This system of traffic is essentially the same, so it is a constant flow system. Previously, for example, to illustrate the implementation .of the hydraulic balance of the system. <br> This system mainly static hydraulic imbalance exists, in the horizontal branch pipe as the tee or two-way regulation of the temperature control valve and there is a certain dynamic hydraulic imbalance. So just add in .the relevant parts of the hydraulic balance device can cause the system to maintain the hydraulic balance. As follows: <br> ⑴, in water system room set hydraulic balance valve installed on; <br> ⑵, in standpipe return pipe hydraulic valves on the .provided; <br> ⑶, horizontal branch pipe installation flow regulator guarantees a constant flow of all branch loops (either in this branch loop internal pipeline properties to maintain a constant flow, you can also change other loop flow from its interference). <br .> 3. terminal equipment with three-way valves for air conditioning systems: <br> 4. variable-flow hydraulic balance analysis: as people on the requirements of the quality system and energy conservation consciousness, variable flow hydraulic system in occupies HVAC engineering is .becoming more and more important position. <br> Variable flow system for running branch loop flow is with the external environment load changes. As a result of HVAC engineering in the year running for most of the time at the part-load operating condition, so .the variable flow system for most of the time system flow is lower than the design flow. Therefore this system is a real-time, sensitive, high efficient and energy saving. <br> Variable flow system normally static hydraulic imbalance exists, there is a .dynamic hydraulicDisorders, so you must take the appropriate measures to achieve the hydraulic balance system for the hydraulic balance. <br> 1. static hydraulic balance of realization: <br> By installing the appropriate sites static hydraulic balance device, allowing the system to achieve .static hydraulic balance. <br> Implements static hydraulic balance of judgement is based on: when the system all dynamic hydraulic balancing devices are set to the position of design parameters (design flow or pressure), all terminal devices for temperature control valves (temperature control .valve, electric 2-way valve and electric control valves, etc) are in the fully open position (when the system is completely fixed flow system, all traffic is unchanged), the system all terminal equipment flow reached the design flow. <br> .As can be seen from the top, enabling static hydraulic balance aims to ensure that terminal equipment at the same time meet the design flow, ie the equipment required for maximum flow. Avoid a general part hydraulic offset system equipment has not reached the design flow, .while another part is much higher than the design flow. Therefore it is a static balance and system capacity issues, ensure the system is balanced transport enough to terminal equipment of water. <br> Variable flow system static hydraulic balance device of choice you can reference .a description of the constant flow system, it will not repeat them here. <br> However, the terminal equipment in most of the time is not required so much traffic. Therefore, the system must not only implement static hydraulic balance, but also achieve .dynamic hydraulic balance. <br> 2, dynamic hydraulic balance of realization: <br> Install the appropriate parts of dynamic hydraulic balancing equipment, allowing the system to achieve dynamic hydraulic balance. It contains two elements: <br> ①, when other loop .changes its own loop point differential pressure and not consequential changes, when their own dynamic valve (such as temperature control valve, electric control valve) opening does not change, the flow remains unchanged, as shown in Figure 4, when C, D point pressure .change, through dynamic hydraulic balancing equipment (pressure regulator PV) of the A, B second point pressure does not change, if the second valve road electric VM1 and VM2 ... Opening remains unchanged, it flows through the fan coil FP1, FP2 flow .remains unchanged; <br> ②, while environmental load changes cause the system to their own loops change, through the dynamic role of hydraulic balancing device, so that critical point pressure differential is not changed, this time its other parallel branches of flow does not .change. When the fan coil FP1 is located room load changes lead to electric 2-way valve to close by opening FM1, due to the pressure regulator PV1, A, B the second point of pressure and not consequential changes so that the air blower plate .Tube FP2 flow remains unchanged. <br> From the variable flow system dynamic hydraulic balance typically by dynamic hydraulic balance device will double parallel system critical point pressure constant pressure difference in design. Therefore variable flow dynamic hydraulic balancing system can also be called a variable flow .pressure differential system. Pressure regulator is the main variable flow system adjustment mode. In fact, dynamic hydraulic balance of another key equipment flow regulator is through body internal key point constant pressure differential (key points of the throttling device turn on degree is it unchanged) .to maintain the flow constant (fixed valve bile-excluded). <br> The following variable flow system several typical dynamic hydraulic balance for analysis: <br> ⑴, HVAC room three main variable flow dynamic hydraulic balance mode: <br> ①, .self-supported pressure regulator: <br> ②, electric control valve: <br> Electric control valve can be divided into electric 2-way valve and electric three-in-(sub) flow control valve means three to electric second valve mode, .for example: <br> ③, FM pumps: <br> ⑵, heating system, a typical variable flow hydraulic balance mode: <br> Through the variable flow heating system critical point differential pressure setting of the layer, so that the system of .flow of each radiator only because their load changes and through the regulation of temperature control valve to change, and not because the system other radiator flux and change. This system really enables dynamic hydraulic balance. <br> Vertical double-tube, with a diversity .of water radiator and floor heating system with household set ring is variable flow system, its hydraulic balance characteristics are consistent with the above. <br> For single-, double-tube combo system, the branch pipe for single-pipe-line on- .set flow system for analysis, the branch pipe for double parallel and competent, room parts according to variable flow system for analysis. <br> ⑶, air-conditioning system typical variable flow hydraulic balance mode: <br> ①, belt electric two- .way valve air blower plate Tube variable flow hydraulic balance mode: <br> The system of analysis refer to the four hydraulic balance. <br> 2 (dynamic hydraulic balance of implementation). <br> It is worth noting that the current market has .an automatic balance electric regulating valve, its functionality and the way is the same, and are able to guarantee each fan coil achieve dynamic hydraulic balance. It combines the above function and electric 2-way valve is integrated into a valve, installed on each fan .coil tributary, the drawback is the price higher. <br> ②, belt electric regulating valve of the air handling units (or Cabinet type exchanger unit) variable flow hydraulic balance mode: <br> ③, belt of dynamic balance electric regulating valve of .the air handling units (Cabinet type exchanger unit) variable flow hydraulic balance mode: <br> Dynamic balance electric regulating valve is a novel and efficient, tuning performance excellent electric regulating valve, it is essentially pressure regulator integrated with electric control valve. When the .system properties of other pipeline changes because of dynamic balance electric regulating valve built-in pressure differential regulators, allowing A, B second point differential pressure remains unchanged. VM if electric regulating valve to open degree, then through the air handling unit with water flow remains .unchanged. When the air handling unit return air temperature T is changed, the input to the regulator gauges measuring return air temperature and air temperature setting, 4-20mA output a control signal to control electric control valve to open degree, to regulate water flow, .ensuring the return air temperature and the temperature setting. In electric control valve action, due to the pressure regulator roleThe electric control valve b-side pressure (A, B II) remain unchanged, so this is a sensitive and effective regulation and control valve flow .characteristic curve and ideal flow characteristic curve consistent, no deformation. This electric regulating valve than ordinary electric regulating valve with better regulation. <br> 5. closing: <br> Constant flow system with variable flow systems are diverse, here simply analyze several typical .forms. It should be noted that, in the actual engineering design, project investment and system accuracy requirement reasonably use hydraulic balance device, it is necessary to meet the project design and technical specifications, while the programme should be used rationally, saves money for the .party. <br> <br> <br> <br> <br> <br> <br>.