冷却塔全接触.ppt

1、262,McQuay 中国,By Nick Chan (陈万里),262,By Nick Chan (陈万里),Cooling tower 冷却塔,Agenda,Training Agenda: Cooling Towers,Introduction 简介 Types of cooling towers 类型 Assessment of cooling towers 评估 Energy efficiency opportunities 节能方案,Introduction 冷却塔简介,Main Features of Cooling Towers 整体结构,Introduction,Frame

2、and casing: support exterior enclosures 支架和塔体: 外部支撑 Fill: facilitate heat transfer by maximizing water / air contact 填料：为水和空气提供尽可能大的换热面积,Components of a cooling tower 冷却塔组成部分,Introduction,Splash fill droplets of water splash over, prevent fouling 喷淋式将水呈水雾状喷出，这样的方式可以避免塔内结垢。 Film fill layers of water

3、fall over (more efficient), but more expensive 水膜式水呈膜状顺填料表面流下，效率较高但是成本高昂。 Cold water basin: receives water at bottom of tower 冷却水槽：位于冷却塔底部，接收冷却水,Introduction,喷淋式 水膜式,Introduction,Drift eliminators 收水器: capture droplets in air stream 回收空气流带走的水滴 Air inlet 进风口：entry point of air 冷却塔空气入口 Louvers冷却塔百叶窗：

4、equalize air flow into the fill and retain water within tower 平均进气气流；保留塔内水分,Components of a cooling tower 冷却塔组件,Introduction,Nozzles 淋水装置： spray water to wet the fill 将冷却水喷出 Fans 风机： deliver air flow in the tower 向冷却塔内送风 Propeller fans used in induced draft towers 轴流风扇用于诱导通风冷却塔 Propeller & centrifug

5、al fans used in forced draft towers 轴流/离心风扇用于强制通风冷却塔,Training Agenda: Cooling Towers,Introduction 简介 Types of cooling towers 类型 Assessment of cooling towers 评估 Energy efficiency opportunities 节能方案,Types of Cooling Towers 冷却塔种类,Hot air moves through tower 密度较小的热空气自冷却塔顶部流出 Fresh cool air is drawn into

6、 the tower from bottom 密度较大的冷空气自塔底部进入冷却塔填补,Natural Draft Cooling Towers 自然通风冷却塔,Types of Cooling Towers 冷却塔种类,No fan required 不需风机 Concrete tower 200 m 混凝土塔200 m Used for large heat duties 用于大热量的冷却,Natural Draft Cooling Towers 自然冷却塔,Types of Cooling Towers 冷却塔种类,Natural Draft Cooling Towers 自然冷却塔,横流

7、,对流,Types of Cooling Towers 冷却塔类型,两种冷却塔,横流,对流,Types of Cooling Towers 冷却塔种类,Large fans to force air through circulated water 大功率风机强制空气与循环水的换热 Water falls over fill surfaces: maximum heat transfer 填料表面的水膜可以最大限度地与空气进行换热,Mechanical Draft Cooling Towers 机械通风冷却塔,Types of Cooling Towers 冷却塔种类,Cooling rate

8、s depend on many parameters 冷却效率的决定因素有很多 Large range of capacities 多种冷却能力备选 Can be grouped, e.g. 8-cell tower 可以多冷却塔同时工作，例如8塔联控。,Types of Cooling Towers 冷却塔种类,Three types 机械通风冷却塔分为三类： Forced draft 强制通风冷却塔 Induced draft cross flow 诱导通风横流冷却塔 Induced draft counter flow 诱导通风逆流冷却塔,Mechanical Draft Coolin

9、g Towers,Types of Cooling Towers,Air blown through tower by centrifugal fan at air inlet 空气由离心风扇吹入通风口 Advantages: suited for high air resistance & fans are relatively quiet 优势：适用于气流阻力较大的塔体；离心风扇噪声相对较小,Forced Draft Cooling Towers,Disadvantages: recirculation due to high air-entry and low air-exit velo

10、cities 劣势：由于进气流速高于排气流速，会出现回流。,19,Cooling Tower Basics,Forced Draft 强制通风 Counter flow Tower 逆流冷却塔,Water is sprayed on to the fill and falls to the tower basin. 冷却水被喷淋在填料上，向下流入冷 却水槽,Air is blown up through the fill and evaporates some of the water and reduces the water temperature. 空气从底部强制吹入，在填料内与水接触蒸

11、发部分冷却水，从而降低水温,Types of Cooling Towers,Two types 诱导通风冷却塔分两类： Cross flow 横流式诱导通风冷却塔 Counter flow 逆流式诱导通风冷却塔,Induced Draft Cooling Towers 诱导通风冷却塔,Types of Cooling Towers,Advantage: less recirculation than forced draft towers & lower motor running cost 优势：回流程度低于强制通风冷却塔；风机运 行费用小于强制通风冷却塔。 Disadvantage: fa

12、ns and motor drive mechanism require weather-proofing 劣势：风扇与电机的机械传动需要防水设计,Types of Cooling Towers,Hot water enters at the top 热水从顶部进入冷却塔 Air enters at bottom and exits at top 空气通过风扇强制诱导，从底部进入冷却塔 Uses induced draft fans 使用强制诱导风扇,Induced Draft Counter Flow CT,23,Cooling Tower Basics,Induced Draft 诱导通风

13、 Counter flow Tower 逆流式,Water is sprayed on to the Fill and falls to the tower Basin 冷却水从顶部喷入，流经填料层进入冷却水槽,Air is drawn through the Fill and evaporates some Of the water and reduces The remaining water temperature. 空气由诱导风机引入冷却塔从底部，在填料内与水接触蒸发部分冷却水，从而降低水温,Cooling Tower Basics,Due to their pressurized s

14、pray water distribution system 因为此类冷却塔内的加压配水喷淋装置： Advantages 优势: Increased tower height accommodates longer ranges and closer approaches 通过增加塔的高度来获得更长的换热流程与更小的冷幅 More efficient use of air due to finer droplet size from pressure sprays 由于加压喷淋装置可以喷出更小的水滴，因此换热效率较高,Induced draft counter flow 逆流式诱导通风冷却塔,

15、Cooling Tower Basics,Disadvantages 劣势： Increased system pumping head requirements 系统水泵压头增加 Increased energy consumption and operating costs 能量需求增大，运行费用增加 Distribution nozzles difficult to inspect and clean 冷却水喷头不易维护和清洁 Requires extra distributor and external piping costs 需要配水系统以及相关管路，因此初投资增加,Types o

16、f Cooling Towers,Water enters top and passes over fill 冷却水从顶部进入，流经填料层 Air enters on one side or opposite sides 空气从一侧或两侧进入 Induced draft fan draws air across fill 诱导风机使空气横向流过填料层,Induced Draft Cross Flow CT 横流式诱导通风冷却塔,27,Cooling Tower Basics,Induced Draft Cross Flow Tower,Water is sprayed on to the Fi

17、ll and falls to the tower Basin. Fill is deeper larger Surface area. 冷却水喷淋至填料层，从顶部 流至底部的冷却水槽,Air is drawn through the Fill and evaporates some Of the water and reduces The water temperature. Less air required 空气由诱导风机引入冷却塔侧面，在填料内横向流动与水接触蒸发部分冷却水，从而降低水温,Cooling Tower Basics,Due to their gravity flow ho

18、t water distribution system 由于此类冷却塔的水属于自然流配水系统： Advantages 优势： Low pumping head 低水泵压头 Lower first cost pumping systems 较低的水泵初投资 Lower annual energy consumption and operating costs 较低的年运行能耗和费用 Accepts larger variation in water flow without adverse effect on the water distribution pattern 流量变化较大时不会对配水

19、系统造成不利的影响,Induced draft cross flow 横流式诱导通风冷却塔,Cooling Tower Basics,Disadvantages 劣势： Low pressure head on the distribution pan may encourage orifice clogging and less water breakup at spray nozzle 低压头会导致喷头易于堵塞以及冷却水喷出时不能很好的分散成细密水雾 Exposure to air in the hot water basin may accelerate algae growth 热水水

20、槽直接暴露于空气中会导致藻类的滋生 Larger footprint 占地面积较大,Training Agenda: Cooling Towers,Introduction 简介 Types of cooling towers 类型 Assessment of cooling towers 评估 Energy efficiency opportunities 节能方案,Assessment of Cooling Towers,Measured Parameters 应测量的参数,Wet bulb temperature of air 空气湿球温度 Dry bulb temperature of

21、 air 空气干球温度 Cooling tower inlet water temperature 冷却塔进水温度 Cooling tower outlet water temperature 冷却塔出水温度 Electrical readings of pump and fan motors 水泵和电机运行参数 Water flow rate 水流速度 Air flow rate 空气流速,Performance Parameters 运行参数,Range 冷却水温差 Approach 冷幅 Effectiveness 效率 Cooling capacity 冷却塔容量 Evaporatio

22、n loss 蒸发损失 Cycles of concentration 浓缩倍数 Blow down losses 排污损失 Liquid / Gas ratio 液体/气体比,Assessment of Cooling Towers,1. Range 冷却水温差,Difference between cooling water inlet and outlet temperature: 冷却水进出水温差： Range (C) = CW inlet temp CW outlet temp High range = good performance 大温差 = 高性能,Assessment of

23、 Cooling Towers,2. Approach 冷幅,Difference between cooling tower outlet cold water temperature and ambient wet bulb temperature: 冷却塔出水温度与入口空气湿球温度的差值： Approach (C) = CW outlet temp Wet bulb temp Low approach = good performance 小冷幅 = 高性能,Assessment of Cooling Towers,3. Effectiveness 效率,Effectiveness in

24、 % = Range / (Range + Approach) 效率=冷却水温差/（冷却水温差+冷幅） High effectiveness = good performance 高效率=高性能,Assessment of Cooling Towers,4. Cooling Capacity 冷却塔容量,Heat rejected in kCal/hr or tons of refrigeration (TR) = mass flow rate of water X specific heat X temperature difference 冷却塔容量单位为“千卡每小时”或者“冷吨” 冷却塔

25、容量=冷却水质量流量X水的比热容X温差 High cooling capacity = good performance 大容量=高性能,Assessment of Cooling Towers,5. Evaporation Loss 蒸发损失,Water quantity (m3/hr) evaporated for cooling duty 蒸发损失的单位为(m3/hr) ，表示每小时因为冷却而损失的水量 = theoretically, 1.8 m3 for every 10,000,000 kCal heat rejected 理论上蒸发损失为1.8立方米/1千万千卡 = 0.0008

26、5 x 1.8 x 流量 (m3/hr) x 冷却水温差,Assessment of Cooling Towers,Assessment of Cooling Towers,5. Evaporation Loss 蒸发损失,Cooling Tower Industry (CTI) Rates Towers At ARI Condenser Water 工业冷却塔的ARI工况： Water flow rate across cooling tower = 0.054 (L/s) / Kw 冷却塔流量 = 0.054 (L/s) / Kw Cooling tower capacity = 3500

27、kW 冷却塔容量 = 3500kW 29.4 Leaving Fluid 出水温度29.4 35 Entering Fluid 进水温度35 Use the formula from previous page 应用前一页的公式: = 0.00085 x 1.8 x 流量 (m3/hr) x 冷却水温差 = 0.00085 x 1.8 x 680.4 x (35 29.4) = 5.82 m3/hr A 3500 kW Tower Can Consume 5820 Liters Per Hour of Make up Water Due To Evaporation 一个3500kW冷却塔的冷

28、却水蒸发量为5820升每小时,Assessment of Cooling Towers,6. Cycles of concentration 浓缩倍数,Ratio of dissolved solids in circulating water to the dissolved solids in make up water 循环水中固态溶解物含量与补充水中固态溶解物的含量之比 Increase this to reduce water loss 增加此比例可减小蒸发损失,7. Blow-down 排污量,Depend on cycles of concentration and the ev

29、aporation losses 决定于循环水浓度与蒸发损失 Blow-down = circulating water removed amount to maintain the amount of dissolved solids and other impurities at an acceptable level = Evaporation Loss / (C.O.C. 1) 排污量 = 为将固态溶解物和其他杂质浓度维持在可接受范围内而排出的循环水量 = 蒸发损失/（ C.O.C. 1）,8. Liquid Gas (L/G) Ratio 液气比,Ratio between wate

30、r and air mass flow rates 水与空气的质量流量之比 Heat removed from the water must be equal to the heat absorbed by the surrounding air 冷却水散发的热量等于空气吸收的热量 L(T1 T2) = G(h2 h1) L/G = (h2 h1) / (T1 T2) T1 = hot water temp (oC) 热水温度（冷却塔进水） T2 = cold water temp (oC) 冷水温度（冷却塔出水） Enthalpy of air water vapor mixture at

31、inlet wet bulb temp (h1) and outlet wet bulb temp (h2) 冷却塔进口（空气与水蒸气混合）温度对应的焓值(h1)与出口温度（湿球温度）的焓值(h2),Assessment of Cooling Towers,41,Cooling Tower Process 冷却塔工作流程,1. Air Enters at 35 DB 26 WB 空气35 DB 26 WB 2. Air Leaves Saturated at 30.8 2. 30.8 饱和空气离开冷却塔 3. Entering Air Enthalpy is 78.5 kJ/kg 3. 进口空

32、气的焓值是78.5kJ/kg 4. Leaving Air Enthalpy is 103.9 kJ/kg 出口空气的焓值是103.9kJ/kg 5. Water Vaporized Latent Heat is 2430 kJ/kg 11 g water absorbs 26.7 kJ heat during evaporating 5. 蒸汽的潜伏热值是2430 kJ/kg，11g的水吸取26.7kJ的热量 6. Air Sensible heat is 26.7 25.4 = 1.3 kJ 6. 空气的感热为 26.7 25.4 = 1.3 kJ,17.3g,28.3g,L/G = (h

33、2 h1) / (T1 T2) L/G = (103.9 78.5) / (35 30.8) L/G = 25.4 / 11 = 6.05,(g/g),Training Agenda: Cooling Towers,Introduction 简介 Types of cooling towers 类型 Assessment of cooling towers 评估 Energy efficiency opportunities 节能方案,Energy Efficiency Opportunities,Selecting a cooling tower 选择冷却塔 Fills 填料 Pumps a

34、nd water distribution 水泵与配水设备 Fans and motors 风扇与电机,Energy Efficiency Opportunities,1. Selecting a cooling tower 选择冷却塔,Capacity 冷却塔容量 Heat dissipation (kCal/hour) 散热量 (kCal/hour) Circulated flow rate (m3/hr) 循环水流量 (m3/hr) Other factors 其它因素,Energy Efficiency Opportunities,Range 冷却水温差 Range determine

35、d by process, not by system 冷却水温差取决于换热过程而不是设备 Approach 冷幅 Closer to the wet bulb temperature = Bigger size cooling tower = More expensive 越接近湿球温度 = 更大的冷却塔 = 更多的投资,1. Selecting a cooling tower,Energy Efficiency Opportunities,Heat Load 热负荷 Determined by process 决定于换热过程 Required cooling is controlled b

36、y the desired operating temperature 合适的工况下才能保证需要的冷量 High heat load = large size and cost of cooling tower 热负荷大 = 更大的冷却塔与更多的设备费用,1. Selecting a cooling tower,Energy Efficiency Opportunities,Wet bulb temperature considerations: 关于湿球温度 Water is cooled to temp higher than wet bulb temp 冷却水出水温度高于空气湿球温度 C

37、onditions at tower site 冷却塔坐落位置的具体情况 Not to exceed 5% of design wet bulb temp 湿球温度不可高于设计湿球温度的5%及以上 The designed wet bulb temp is refer to ambient WB (preferred) or inlet 此湿球温度指的是环境湿球温度（推荐）或者空气入口处湿球温度 Can tower deal with increased wet bulb temp? 冷却塔能否适应较高的湿球温度,Relationship range, flow and heat load 温

38、差，流量与热负荷的关系,Range increases with increased： 以下两项增加的情况下温差会增大： Amount circulated water (flow) 循环水量（流量） Heat load 热负荷 Causes of range increase 温差增大的原因如下： Inlet water temperature increases 进水温度升高 Exit water temperature decreases 出水温度降低 Consequence = larger tower 冷却水温差增大 = 更大的冷却塔,Wet bulb temperature inf

39、luence on chiller performance 湿球温度对机组运行的影响,Lowering condenser water impact on chiller improvement 冷却水温下降对机组性能的影响,0.56 Deg C,Lowering condenser water impact on cooling tower 冷却水温下降对机组性能的影响,3.9 Deg C,Get temperature data from customer 用户提供的湿球温度变化图,WB 26 Deg C = 337 Days WB 26 Deg C = 27 Days,Energy Ef

40、ficiency Opportunities,Hot water distributed over fill media and cools down through evaporation 热水经过配水设备流经填料介质，蒸发降温 Fill media impacts electricity use 填料介质影响冷却塔用电量 Efficiently designed fill media reduces pumping costs 高效填料介质可以节约管路投资 Fill media influences heat exchange: surface area, duration of contact, turbulence 填料介质影响换热效率：表面积，接触时间与湍流,2. Fill media 填料,Energy Efficiency Opportunities,Comparing 3 fill media: film fill more efficient 比较三种填料介质 ：水膜填料效率最高,2. Fill media 填料介质,Energy Efficiency Opportunities,Pumps: see pumps session 水泵：见水泵部