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1、HVAC 基本知识培训（二）,Day2： 1、空调水系统 2、冷冻水系统控制原理 3、Honeywell 风阀和水阀介绍 4、水阀选型计算公式,培训内容,空调水系统形式,双管制： 冷热水共用同一套相同的管路。夏季供冷，冬季供热，大多数的空调都采用这种方式。它主要的优点是系统简单，造价低。但是对于全年空调的建筑，在过渡季节，会出现朝阳的房间需要的供冷而背阳的房间需要供热的情况，那么该系统就不能满足该要求。 四管制： 冷水和热水管路分开，可同时满足制冷和制热的要求；但结构复杂，造价高。 同程式： 同程式水系统除了供回水管路外，还有一根同程管。它具有：水力稳定性好，流量分配均匀的特点。 异程式,单泵
2、式定流量系统,SINGLE CHILLER SET WITH TWO WAY VALVES,MULTIPLE CHILLER SETS WITH TWO WAY VALVES,单式水泵冷冻机台数控制,压差旁通控制法 负荷侧由温度控制二通阀的开度，由供回水管上的压差信号控制旁通阀的开度，当用户负荷减少，水流量减少时，供回水总管之间压差增大，通过控制器将旁通阀开大，让部分水旁流，当开度小于10%时，增加一台机组运行；开度90%时，减掉一台机组运行。旁通管的管径以一台冷水机组的水流量确定。 回水温度控制法 旁通阀维持机组通过的水流量恒定，冷水机组的启停由回水温度来控制。,复式泵水系统（带二次泵系统）
3、,A,B,冷冻机组的控制 流量控制阀 旁通管上设流量开关和流量计。当负荷减少时，水流从AB（称“盈”）流动，当旁通管内的水流量超过一台水泵的流量时，关掉一台冷水机和冷冻水泵。反之，当负荷增加时，水流从BA（称“亏”）流动，当流量为单台流量的20%时，增加一台水泵和冷冻机组。 热量控制阀 在供回水主管上设温度变送器，在回水管上设流量变送器，根据公式计算负荷，来增加和减少冷冻机,复式水泵冷水系统的控制,负荷侧二次泵的控制 负荷侧二通阀，二次泵用定流量泵，通过压力来控制泵的台数 负荷侧二通阀，二次泵用变频泵，当在系统部分负荷的情况下，由于功率与流量的变化承三次方的关系，故节能显著,复式水泵冷水系统的
4、控制,水泵的压力和流量的关系,水系统的承压,水系统承受压力最大的地点是在水泵出口，水系统承压有以下三种： 系统停止运行时，压力P静水压力（P=gh ) 系统开始瞬间：压力PA= 静水压力水泵全压 系统正常运行：压力PA= 静水压力水泵静压,计算能量的公式,（KW x 860）/ 温差L/H （Kcal/h）/ 温差L/H （冷吨（美国）x 3024）/ 温差L/H,VALVE TERMINOLOGY,RANGEABILITY DEFINED AS THE RATIO OF MAXIMUM FLOW RATE TO MINIMUM CONTROLLABLE FLOW RATE FOR EXAMP
5、LE A VALVE WITH FLOW RATE OF 10 L/S WHEN FULLY OPEN AND A RANGEABILITY OF 50 : 1 WILL CONTROL DOWN TO A FLOW RATE OF 0.2 L/S TYPICAL HONEYWELL VALVES HAVE A RANGEABILITY OF 50:1 WHILE THE LARGER VALVES ARE 30:1,VALVE TERMINOLOGY,TIGHT CLOSE OFF / SHUT OFF ALSO KNOWN AS THE LEAKAGE RATE WHEN THE VALV
6、E IS IN THE FULLY CLOSED POSITION FOR HONEYWELL VALVES LESS THAN 65 mm THE LEAKAGE RATE IS TYPICALLY LESS THAN 0.05% OF VALVE KV RATING FOR HONEYWELL VALVES 80 mm AND LARGER THE LEAKAGE RATE IS TYPICALLY LESS THAN 0.1% OF VALVE KV RATING,VALVE STROKE DETAILS THE STEM TRAVEL AT WHICH THE VALVE IS AT
7、THE DESIGN KV RATING HONEYWELL VALVES LESS THAN 65 mm TYPICALLY HAVE A STROKE OF 20 mm WHILE 80 mm VALVES AND LARGER HAVE A STROKE OF 38 mm IT IS THEREFORE IMPORTANT THAT ACTUATORS WITH THE CORRECT STROKE ARE SELECTED FOR THE PARTICULAR VALVE,VALVE TERMINOLOGY,VALVE RATINGS,EACH VALVE HAS A SPECIFIC
8、 CAPACITY INDEX AND THIS IS DEFINED AS ITS VOLUMETRIC CAPACITY AT A SPECIFIED PRESSURE DIFFERENCE FOR IMPERIAL VALVES THIS IS EXPRESSED AS THE CV RATING FOR METRIC VALVES IT IS EXPRESSED AS THE KVs RATING THE CAPACITY INDICES FOR CV AND KVs VALVES ARE NUMERICALLY RELATED CV = KVs X 1.17 KVs = CV X 0
9、.86 HONEYWELL CONTROL VALVES, WHETHER CV OR KVs INCREASE IN STEPS OF 60%,VALVE BODY PRESSURE RATING,DEFINED AS THE “THEORETICAL” BODY PRESSURE RATING OF THE VALVE WHEN INSTALLED IN A SYSTEM THIS RATING IS STAMPED ON THE VALVE BODY AS THE “PN” NUMBER AND IS EXPRESSED AS “BARS” THE MAJORITY OF HONEYWE
10、LL VALVES HAVE A “PN” RATING OF 16 (1600 kPa) ALTHOUGH SOME ARE LOWER AND OTHERS HIGHER A VALVE WITH A “PN” RATING OF 16 CAN BE INSTALLED IN A SYSTEM WHERE THE STATIC PLUS OPERATING PRESSURE DOES NOT EXCEED 1600 kPa,VALVE / ACTUATOR CLOSE OFF RATING,FOR TWO WAY VALVES IT IS DEFINED AS :- MAXIMUM DIF
11、FERENTIAL PRESSURE THAT THE VALVE / ACTUATOR CAN WITHSTAND WITH OUT LEAKAGE WHILE IN THE FULLY CLOSED POSITION FOR THREE WAY VALVES IT IS DEFINED AS :- MAXIMUM DIFFERENTIAL PRESSURE THAT IS APPLIED ACROSS EITHER OF THE TWO INLET PORTS AND THE COMMON OUTLET PORT AND WHICH THE ACTUATOR WILL STILL DRIV
12、E THE VALVE PLUG CLOSED TO THE REQUIRED PORT,Honeywell 二通阀的结构,VALVE TYPES - 3 WAY VALVES,VALVE TYPES - 2 WAY VALVES,VALVE TYPES - BUTTERFLY VALVES,VALVE SEAT AND PLUG ARRANGEMENTS,HONEYWELL VALVES HAVE VARIOUS TYPES OF PLUG AND SEATS OLD AUSTRALIAN MADE V5011A2XXX VALVES HAD A BRASS PLUG WITH COMPOS
13、ITION DISC TO ENSURE TIGHT CLOSE OFF THE GERMAN V5011R HAVE METAL TO METAL SEATS WITH A LEAKAGE RATE OF LESS THAN 0.05% OF THE KVs RATING LARGER V5328A AND V5049A VALVES HAVE METAL TO METAL SEATS AND HAVE A LEAKAGE RATE OF LESS THAN 0.1% OF THE KV RATING FOR SIZES UP TO 150 mm THE V5011S RANGE OF VA
14、LVES HAVE STAINLESS STEEL PLUG AND SEATS AND ARE USED IN MODULATING STEAM APPLICATIONS THE V176A/B HIGH DIFFERENTIAL PRESSURE VALVES ARE PRESSURE BALANCED UNITS WITH CONTOURED PLUGS AND ARE TYPICALLY USED IN HIGH DIFFERENTIAL PRESSURE APPLICATIONS SUCH AS SYSTEM BYPASS VALVES,QUICK OPENING VALVES,BU
15、TTERFLY VALVES ARE QUICK OPENING DEVICES WHEN CONTROLLED THROUGH THE FULL 90 OF TRAVEL WHEN USED IN LOW DIFFERENTIAL PRESSURE APPLICATIONS THEY EXHIBIT AN APPROXIMATE LINEAR CHARACTERISTIC WHEN THE STROKE OF THE VALVE IS LIMITED TO 60 OPENING RUBBER LINED VALVES PROVIDE TIGHT SHUT OFF BUT AN ACTUATO
16、R WITH ENOUGH TORQUE TO DRIVE THE DISC INTO AND OUT OF THE LINER IS REQUIRED IN LOW DIFFERENTIAL PRESSURE APPLICATIONS “UNDERCUT” DISCS MAY BE USED TO REDUCE ACTUATOR SIZE AND COST,VALVE CHARACTERISTICS,THE RELATIONSHIP BETWEEN STEM TRAVEL AND FLOW RATE IS DEPICTED IN THE FOLLOWING DIAGRAM,LINEAR VALVES,GENERALLY USED FOR STEAM SERVICE,CAN ALSO BE USED ON CHILLED WATER SYSTEMS,MAJORITY OF HONEYWELL VALVES ARE EQUAL % FOR PORTS “A - AB” AND LINEAR FOR PORTS “B - AB”,EQUAL PERCENTAGE VALVES,EQ
