WO2008069874A2 - Régulation de pression statique dans un conduit - Google Patents

Régulation de pression statique dans un conduit Download PDF

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Publication number
WO2008069874A2
WO2008069874A2 PCT/US2007/022575 US2007022575W WO2008069874A2 WO 2008069874 A2 WO2008069874 A2 WO 2008069874A2 US 2007022575 W US2007022575 W US 2007022575W WO 2008069874 A2 WO2008069874 A2 WO 2008069874A2
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WO
WIPO (PCT)
Prior art keywords
speed
static pressure
fan
duct
variable frequency
Prior art date
Application number
PCT/US2007/022575
Other languages
English (en)
Other versions
WO2008069874A3 (fr
Inventor
Alan Stewart Kuentz
Original Assignee
Mcquay International
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mcquay International filed Critical Mcquay International
Publication of WO2008069874A2 publication Critical patent/WO2008069874A2/fr
Publication of WO2008069874A3 publication Critical patent/WO2008069874A3/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/72—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure
    • F24F11/74—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure for controlling air flow rate or air velocity
    • F24F11/77—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure for controlling air flow rate or air velocity by controlling the speed of ventilators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F2110/00—Control inputs relating to air properties
    • F24F2110/30—Velocity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F2110/00—Control inputs relating to air properties
    • F24F2110/40—Pressure, e.g. wind pressure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Definitions

  • the following invention relates to controls for variable-air-volume (VAV) heating, ventilating, and air-conditioning (HVAC) systems, specifically to control the speed of a supply fan in VAV HVAC systems.
  • VAV variable-air-volume
  • HVAC air-conditioning
  • variable-air-volume Key components of a variable-air- volume system are a supply fan and terminal units.
  • the supply fan is a prime mover that causes air to move.
  • a terminal unit contains a throttling device that regulates an amount of air supplied to a space in a building that it controls in order to regulate temperature and ventilation in that space.
  • the supply fan is typically in communication with a plurality of terminal units.
  • variable-air-volume system the flow rate of conditioned air supplied to a building is adjusted so that no more air than necessary is used.
  • Variable flow is achieved by means of the use of controls on or near the supply fan and by use of controls on the terminal units.
  • the supply fan controls vary the speed of the supply fan to provide efficient airflow modulation.
  • the controls on the terminal units determine how much air flows through each terminal.
  • the most common control strategy for the supply fan of variable-air- volume systems is to regulate a static pressure in a supply duct at a point downstream of the supply fan before the terminal unit(s), although static pressure measurement may be made downstream of one or more of the terminal ducts.
  • a rule of thumb is to locate the pressure sensor two-thirds of the distance from the supply fan to the end of the supply duct.
  • the airflow is varied so that the static pressure is maintained at a setpoint that may be constant or reset based on airflow.
  • Control strategies based on a constant static pressure in the supply duct have been proposed in U.S. Pat. No. 4,437,608 to Smith (1984) and U.S. Pat. No. 6,227,961 to Moore et al. (2001).
  • Control strategies that reset the static pressure based on the position of the terminal unit that is most open have been proposed in U.S. Pat. No. 5,863,246 to Bujak (1999).
  • An objective of these strategies is to keep the terminal unit damper nearly open or completely open. Doing this reduces the throttling losses at part-load conditions.
  • a control strategy that adjusts the static pressure setpoint based on measured airflow was proposed as the preferred embodiment in U.S. Pat. No. 6,719,625.
  • PID Proportional-Integral-Derivative
  • a PFD algorithm changes the airflow as needed to minimize the Error. These periodic changes are based on this Error and how the Error is changing.
  • the supply fan may be driven by a Variable Frequency Drive.
  • the calculated speed change is the same regardless of the fan speed for any set of conditions.
  • Fan laws dictate that the duct static pressure varies with the square of the fan speed. A speed change at low speeds results in a bigger change in the duct static pressure than the same speed change at a higher speed. As a result, a PID loop tuned to provide a good response at low speeds will be more sluggish at high speeds and a PID loop tuned to provide a good response at high speed may hunt at low speeds.
  • PID parameters must be adjusted, or tuned, for the algorithm to provide acceptable operation. Such tuning can be difficult with any implementation of a PDD loop. The problem of tuning is made more difficult because of the multiple forms that PID algorithms may take. For example, a loop may respond more quickly when the Integral parameter is increased in one implementation and it may respond more slowly when the Integral parameter is increased in another implementation.
  • a control algorithm is used to control the speed of the supply fan of a variable-air-volume heating, ventilating, and air-conditioning system comprised of the supply fan, a variable frequency drive, a static pressure sensor, and a controller coupled to the static pressure sensor and variable frequency drive.
  • the controller causes the static pressure downstream of the fan to be maintained at a desired static pressure by causing the speed of the variable frequency drive to vary when necessary in proportion to the square root of the ratio of the desired duct static pressure setpoint to the measured duct static pressure.
  • the algorithm of the present invention changes the speed of a variable frequency drive more at higher speeds for a given set of circumstances so that the pressure change is nearly the same at all speeds for a given set of circumstances.
  • the algorithm of the present invention does not require tuning of control parameters of any certain variable frequency drive to maintain a desired duct static pressure.
  • a primary object of the current invention is to provide more accurate and quicker responding control of the duct pressure at a desired duct static pressure in a variable-air- volume system in which a variable frequency drive is used to set the speed of the supply fan.
  • Another object of the current invention is to reduce or eliminate the need to tune parameters to control a variable frequency drive to maintain the duct pressure at a desired duct static pressure in a variable-air-volume system.
  • present invention is a method of controlling a variable-air-volume heating, ventilating, and air-conditioning system and includes causing the static pressure in a duct to be maintained at a desired static pressure by controlling the speed of a fan in proportion to the square root of the ratio of a desired duct static pressure setpoint to a measured duct static pressure.
  • the present invention is further a HVAC system employing the above method.
  • FIG. 1 is a schematic diagram of a portion of a variable-air-volume (VAV) heating, ventilating, and air-conditioning (HVAC) system.
  • VAV variable-air-volume
  • HVAC air-conditioning
  • FIG. 2 is a block diagram of the control method for changing the speed of the supply fan to maintain the measured duct static pressure close to the desired duct static pressure setpoint.
  • FIG. 1 and FIG. 2 The embodiment of the method of adjusting the speed of a variable frequency drive to maintain a desired duct static pressure is shown in FIG. 1 and FIG. 2.
  • Physical components of the system in which this method is used include the supply fan 1 , a supply duct 2, two or more terminal ducts 3, two or more terminal units 4, a static pressure sensor 5, a supply fan controller 6, and a variable frequency drive 7.
  • the system also contains other components such as heat exchangers, cooling coils, and filters not shown in figure 1 that are used for other functions such as heating, cooling, and cleaning air.
  • the supply fan 1 could be either a centrifugal fan or an axial fan.
  • the supply fan duct 2 is an elongate sheet metal structure typically with rectangular cross-section used to transport air.
  • Each terminal duct 3 is an elongate structure made of sheet metal or other material that transports air to a terminal unit 4.
  • the static pressure sensor 5 is located downstream of the supply fan 1.
  • the static pressure sensor 5 indicates the static pressure in the supply duct 2.
  • the supply fan controller 6 is an electronic device with microprocessor and memory.
  • the controller 6 may be integrated with the variable frequency drive 7.
  • a unique feature of the present invention is the algorithm used by the supply fan speed calculator 9 to determine the speed of the variable frequency drive 7 by comparing the output of the static pressure sensor 5 to the desired static pressure setpoint 8.
  • a signal from the static pressure sensor 5 and a static pressure setpoint 8 are inputs to the supply fan speed calculator 9.
  • the setpoint 8 may be a fixed value manually entered into the controller 6 or it may be automatically varied as airflow requirements change by means either internal or external to the supply fan controller 6.
  • the output of the supply fan controller 6 is the input to the variable frequency drive 7.
  • the calculated speed at which the supply fan 1 should operate for any given conditions is determined by using the known non-linear fan law relationship between pressure and fan speed to provide improved control.
  • Fan laws that relate performance variables are described in the ASHRAE Systems and
  • fan law #2b relates speed, N, to pressure, P, in the following manner.
  • N 2 N 1 X (P 2 ZP 1 ) 172
  • the current Speed, Ni provided through a variable frequency drive 7 is multiplied by an estimate of the square root of the ratio of the duct static pressure setpoint, P 2 , divided by the current duct static pressure, Pi, as indicated in Table 1.
  • the speed, N is changed to the new calculated speed, N 2 whenever the duct static pressure, Pi differs from the duct static pressure setpoint, P 2 , by more than a fixed amount, and the variable frequency drive speed has not been changed for longer than the current sample time.
  • the fan laws apply to steady state situations so the current sample time is adjusted when each speed change calculation is made so that the duct static pressure is close to its steady state value when the next calculation is made.
  • One way to accomplish this is by first multiplying the change in speed expressed as a percent of the maximum variable frequency drive speed by the acceleration/deceleration time for the variable frequency drive and then adding an additional time period to allow the unit time to stabilize after the speed change.
  • the absolute value of the speed change is limited to a maximum value so that timely speed changes can be made when the duct static pressure is relatively far from the desired setpoint that would result in large calculated speed changes and sample times.
  • the speed is also set to this maximum value to provide a positive fan speed when the current fan speed is zero.
  • Ace/Dec Time Time required for VFD to change speed of fan from 0 to 100% or 100% to 0.
  • DSP_Deadband Static Pressure range above and below setpoint when no changes are made.
  • Timer is reset to zero whenever the speed is actually changed
  • the method of Table 1 requires no changes to existing VFD 's and no additional wiring to what is standard in VAV units.
  • An advantage to this approach is that existing components are usable and that existing VAV units can be updated with the algorithm of Table 1.
  • Table 2 describes an alternate way of deciding when to change the speed that could be implemented if the actual speed at which the fan is being driven were known. It should be noted that the speed change is calculated as noted above in Table 1. This requires the use of another analog input and wiring between the VFD and the controller. See line 10 of Fig. 1. This algorithm may be implemented within a VFD by a VFD manufacturer.
  • VFD Feedback signal from VFD to Controller indicating actual speed at which Fan is being driven. This value will increase or decrease to the Fan Speed signal sent to VFD after Speed is changed.
  • VFD Feedback Speed for longer than Stabilize Time

Abstract

L'invention concerne un procédé de régulation d'un système de chauffage, de ventilation et de climatisation (CVC) à volume d'air variable, comportant les étapes consistant à faire en sorte de maintenir la pression statique dans un conduit à une pression statique souhaitée en régulant la vitesse d'un ventilateur en proportion de la racine carrée du rapport d'une consigne de pression statique souhaitée dans le conduit à une pression statique mesurée dans le conduit. L'invention concerne en outre un système de CVC employant ledit procédé.
PCT/US2007/022575 2006-12-06 2007-10-25 Régulation de pression statique dans un conduit WO2008069874A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US87330606P 2006-12-06 2006-12-06
US60/873,306 2006-12-06
US11/677,370 US20080139105A1 (en) 2006-12-06 2007-02-21 Duct static pressure control
US11/677,370 2007-02-21

Publications (2)

Publication Number Publication Date
WO2008069874A2 true WO2008069874A2 (fr) 2008-06-12
WO2008069874A3 WO2008069874A3 (fr) 2008-09-25

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Application Number Title Priority Date Filing Date
PCT/US2007/022575 WO2008069874A2 (fr) 2006-12-06 2007-10-25 Régulation de pression statique dans un conduit

Country Status (2)

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US (1) US20080139105A1 (fr)
WO (1) WO2008069874A2 (fr)

Cited By (3)

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Publication number Priority date Publication date Assignee Title
US9657958B2 (en) 2013-07-22 2017-05-23 Ecogate, Inc. Industrial on-demand exhaust ventilation system with closed-loop regulation of duct air velocities
EP2431678A4 (fr) * 2009-05-13 2018-09-05 Mitsubishi Electric Corporation Dispositif de conditionnement d'air
US10634377B2 (en) 2013-07-22 2020-04-28 Ecogate, Inc. Industrial on-demand exhaust ventilation system with closed-loop regulation of duct air velocities

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US20070032187A1 (en) * 2005-08-03 2007-02-08 Mingsheng Liu Air handling unit fan control systems and methods
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US8326464B2 (en) * 2008-08-29 2012-12-04 Trane International Inc. Return fan control system and method
ES2343161B1 (es) * 2009-01-22 2011-06-15 SOLER & PALAU VENTILATION GROUP, S.L. Sistema de ajuste automatico de la presion de un ventilador en funcion del caudal requerido.
US8483883B1 (en) * 2009-06-16 2013-07-09 David Stanley Watson System and method for controlling supply fan speed within a variable air volume system
CN102472514B (zh) * 2009-07-01 2015-02-18 Lg电子株式会社 通风系统
CN101975434B (zh) * 2010-10-15 2012-08-29 杭州源牌环境科技有限公司 一种变风量空调系统的变静压控制方法
US9175872B2 (en) * 2011-10-06 2015-11-03 Lennox Industries Inc. ERV global pressure demand control ventilation mode
CN103292416B (zh) * 2012-03-05 2015-06-24 珠海格力电器股份有限公司 空调器及其风速控制方法和装置
US20150354845A1 (en) * 2013-01-10 2015-12-10 Environmental Construction Services, Inc. Optimized airflow distribution system
TWI531152B (zh) * 2013-04-23 2016-04-21 廣達電腦股份有限公司 風扇控制裝置及其方法
US9692347B2 (en) * 2014-06-13 2017-06-27 Lennox Industries Inc. Airflow-confirming HVAC systems and methods with variable speed blower
US10473349B2 (en) * 2015-03-17 2019-11-12 Systemair Mfg. Inc. Adaptive makeup air system and method for tight enclosures
CN104949202B (zh) * 2015-06-09 2017-04-12 广东美的暖通设备有限公司 一种风管机自适用静压调节方法、调节装置及风管机
CN105066209B (zh) * 2015-08-17 2017-06-20 广东美的厨房电器制造有限公司 烟机系统及其控制方法
CN109540410A (zh) * 2018-10-31 2019-03-29 天津大学 建筑物换气次数测试方法

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EP2431678A4 (fr) * 2009-05-13 2018-09-05 Mitsubishi Electric Corporation Dispositif de conditionnement d'air
US9657958B2 (en) 2013-07-22 2017-05-23 Ecogate, Inc. Industrial on-demand exhaust ventilation system with closed-loop regulation of duct air velocities
US10634377B2 (en) 2013-07-22 2020-04-28 Ecogate, Inc. Industrial on-demand exhaust ventilation system with closed-loop regulation of duct air velocities

Also Published As

Publication number Publication date
WO2008069874A3 (fr) 2008-09-25
US20080139105A1 (en) 2008-06-12

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