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设计与控制逻辑案列分析(直接压力控制系统)
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实验室设计参数:实验室布局如下图所示,实验室布置有11524型通风柜,实验室的具体信息参数如下:

实验室体积Laboratory size = 12’ x 14’ x 10’ (1,680 ft3)=3.658m*4.267m*3.048m=47.57m3

1524型通风柜(1)=300CMHmin* 1500 CFM max*

补偿风量Flow offset = 150-475CMH

通风换气量= 475CMH* (ACPH = 10/按照换气次数10/小时设计)

满足实验室制冷所需的送风量 = 680CMH*

设计压差 = -0.001 “ H2O*=-0.25Pa

设计温度= 72F=22.2

 

房间压力控制系统Room Pressure Control System:

(1) TSI 8636直接压力控制系统安装于实验室内/Model 8636 Direct Pressure Control System mounted in the laboratory.

(2) 同时,实验室安装房间压差传感器用于检测实验室(受控环境)与走廊(压力参照环境)间的压力差/A through-the-wall pressure sensor mounted between the corridor(referenced space) and laboratory (controlled space).

(3) 蝶阀、压力相关型VAV box或文丘里阀安装于新风送风管道/Damper, pressure dependent VAV box or venturi valve with actuator assembly mounted in supply air duct(s).

(4) 蝶阀、压力相关型VAV box或文丘里阀安装于房间综合排风管道/ Damper, pressure dependent VAV box or venturi valve with actuator assembly mounted in exhaust air duct.

(5) 流量监测站安装于新风送风管道(使用文丘里阀系统除外) /Flow station mounted in supply air duct. (Required for non-venturi valve applications only).

 

温度控制系统Temperature Control System:

(1)温度传感器(1000Platinum RTD)安装于实验室内/ Temperature Sensor (1000Platinum RTD) mounted in the laboratory.

(2) 再热盘管安装于新风送风管道上/Reheat coil mounted in supply air duct(s).

 

通风柜控制系统Fume Hood Control System:

(1) 独立的通风柜变风量控制系统/Independent VAV Face Velocity Control system.

 

送风管道截面积0.0929 m2/SUP DCT AREA 1.0 ft2 (12”* 12”) Supply duct area

 

10/小时通风换气次数设置风量475CMH/VENT MIN SET 475CMH 10 air changes per hour

满足实验室制冷所需的送风量680CMH*/COOLING FLOW 680CMH Required flow to cool laboratory.

设计温度= 72F=22.2/ TEMP SETP 72F Laboratory temperature set point.

设计压差 = -0.001 “ H2O*=-0.25Pa/ SET POINT –0.001 in. H2O Pressure differential set point.

 

运行顺序/Sequence Of Operation

开始场景:实验室保持微负压-0.25Pa ,实验室的温度满足舒适度要求;Beginning scenario: Laboratory is maintaining pressure control; -0.001” H2O, Temperature requirement is satisfied.

场景一,通风柜移门关闭,此时通风柜排风量为300CMH/ Fume hood sashes are down; Total hood exhaust is 300CMH.送风量475CMH(保持通风换气要求,ACPH=10)/Supply air is 475CMH (maintain ventilation).

实验室综合排风风量不测量,但通过调节综合排风来维持房间压差稳定/General exhaust flow is not measured. The general exhaust flow is modulated to maintain the pressure differential.

 

场景二,实验室工作人员开始实验,通风柜打开,面风速保持0.5m/s,此时通风柜排风量1500CMH./ The fume hood is opened so that the chemists can load experiments into the hood. The face velocity (100 ft/min) is maintained by the fume hood face velocity controllers by modulating the fume hood dampers. The total fume hood flow is now 1500CMH.

 

首先,实验室综合排风阀门调节至关闭以维持房间压差稳定。一旦综合排风阀门完全关闭,随之送风量将增加以维持房间压差稳定,送风量将名义上增加至1350CMH.

The general exhaust damper will first be modulated closed in order to maintain the pressure differential. Once the general exhaust damper is fully closed, the supply air volume will then be increased to maintain the pressure differential. The supply air volume will nominally be increased to 1350CMH.

 

当实验完成后通风柜移门关闭,此时通风柜的排风量将跌至300CMH。随之,首先送风量将减小至满足通风换气(10/小时换气次数)要求的最小风量。一旦送风量达到满足通风换气(10/小时换气次数)要求的最小风量,控制器将通过调节综合排风来维持房间压力。

The hood is shut after the experiments are loaded so the fume hood exhaust flow decreases to 300 CMH. The supply flow will first be reduced to its minimum flow (VENT MIN SET). Once the supply flow reaches is minimum, the general exhaust will be modulated to maintain pressure.

 

此时,实验室的一个烘箱开始工作实验室温度随之不断升高。房间温度的上升通过温度传感器来测量。首先,控制器将关闭再热盘管的阀门,开始一个为期3分钟的温度调节期。如果三分钟后实验室温度仍然过高,控制器将逐步增大送风量直至满足实验室制冷所需的送风量680CMH。与此同时,房间的综合排风也必须增加阀门开度来维持房间压差稳定。

 

An oven is turned on and the laboratory is getting warm. The rise in space temperature is measured by the space temperature sensor. The controller will first close the reheat valve, and begin a 3-minute time period. If, after the 3-minute time period the space temperature is still too warm, the controller will gradually increase the supply flow to the COOLING FLOW set point. This increases the supply air to 680CMH. The general exhaust air must also increase (damper opens) to maintain the pressure differential.

 

控制环路将持续保持房间压力和温度控制满足要求。

The control loop continuously keeps the room pressure, and temperature control satisfied.

 


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