1、262,McQuay 中國(guó),By Nick Chan (陳萬里),262,By Nick Chan (陳萬里),Cooling tower 冷卻塔,Agenda,Training Agenda: Cooling Towers,Introduction 簡(jiǎn)介 Types of cooling towers 類型 Assessment of cooling towers 評(píng)估 Energy efficiency opportunities 節(jié)能方案,Introduction 冷卻塔簡(jiǎn)介,Main Features of Cooling Towers 整體結(jié)構(gòu),Introduction,Frame

2、and casing: support exterior enclosures 支架和塔體: 外部支撐 Fill: facilitate heat transfer by maximizing water / air contact 填料：為水和空氣提供盡可能大的換熱面積,Components of a cooling tower 冷卻塔組成部分,Introduction,Splash fill droplets of water splash over, prevent fouling 噴淋式將水呈水霧狀噴出，這樣的方式可以避免塔內(nèi)結(jié)垢。 Film fill layers of water

3、fall over (more efficient), but more expensive 水膜式水呈膜狀順填料表面流下，效率較高但是成本高昂。 Cold water basin: receives water at bottom of tower 冷卻水槽：位于冷卻塔底部，接收冷卻水,Introduction,噴淋式 水膜式,Introduction,Drift eliminators 收水器: capture droplets in air stream 回收空氣流帶走的水滴 Air inlet 進(jìn)風(fēng)口：entry point of air 冷卻塔空氣入口 Louvers冷卻塔百葉窗：

4、equalize air flow into the fill and retain water within tower 平均進(jìn)氣氣流；保留塔內(nèi)水分,Components of a cooling tower 冷卻塔組件,Introduction,Nozzles 淋水裝置： spray water to wet the fill 將冷卻水噴出 Fans 風(fēng)機(jī)： deliver air flow in the tower 向冷卻塔內(nèi)送風(fēng) Propeller fans used in induced draft towers 軸流風(fēng)扇用于誘導(dǎo)通風(fēng)冷卻塔 Propeller & centrifug

5、al fans used in forced draft towers 軸流/離心風(fēng)扇用于強(qiáng)制通風(fēng)冷卻塔,Training Agenda: Cooling Towers,Introduction 簡(jiǎn)介 Types of cooling towers 類型 Assessment of cooling towers 評(píng)估 Energy efficiency opportunities 節(jié)能方案,Types of Cooling Towers 冷卻塔種類,Hot air moves through tower 密度較小的熱空氣自冷卻塔頂部流出 Fresh cool air is drawn into

6、 the tower from bottom 密度較大的冷空氣自塔底部進(jìn)入冷卻塔填補(bǔ),Natural Draft Cooling Towers 自然通風(fēng)冷卻塔,Types of Cooling Towers 冷卻塔種類,No fan required 不需風(fēng)機(jī) Concrete tower 200 m 混凝土塔200 m Used for large heat duties 用于大熱量的冷卻,Natural Draft Cooling Towers 自然冷卻塔,Types of Cooling Towers 冷卻塔種類,Natural Draft Cooling Towers 自然冷卻塔,橫流

7、,對(duì)流,Types of Cooling Towers 冷卻塔類型,兩種冷卻塔,橫流,對(duì)流,Types of Cooling Towers 冷卻塔種類,Large fans to force air through circulated water 大功率風(fēng)機(jī)強(qiáng)制空氣與循環(huán)水的換熱 Water falls over fill surfaces: maximum heat transfer 填料表面的水膜可以最大限度地與空氣進(jìn)行換熱,Mechanical Draft Cooling Towers 機(jī)械通風(fēng)冷卻塔,Types of Cooling Towers 冷卻塔種類,Cooling rate

8、s depend on many parameters 冷卻效率的決定因素有很多 Large range of capacities 多種冷卻能力備選 Can be grouped, e.g. 8-cell tower 可以多冷卻塔同時(shí)工作，例如8塔聯(lián)控。,Types of Cooling Towers 冷卻塔種類,Three types 機(jī)械通風(fēng)冷卻塔分為三類： Forced draft 強(qiáng)制通風(fēng)冷卻塔 Induced draft cross flow 誘導(dǎo)通風(fēng)橫流冷卻塔 Induced draft counter flow 誘導(dǎo)通風(fēng)逆流冷卻塔,Mechanical Draft Coolin

9、g Towers,Types of Cooling Towers,Air blown through tower by centrifugal fan at air inlet 空氣由離心風(fēng)扇吹入通風(fēng)口 Advantages: suited for high air resistance & fans are relatively quiet 優(yōu)勢(shì)：適用于氣流阻力較大的塔體；離心風(fēng)扇噪聲相對(duì)較小,Forced Draft Cooling Towers,Disadvantages: recirculation due to high air-entry and low air-exit velo

10、cities 劣勢(shì)：由于進(jìn)氣流速高于排氣流速，會(huì)出現(xiàn)回流。,19,Cooling Tower Basics,Forced Draft 強(qiáng)制通風(fēng) Counter flow Tower 逆流冷卻塔,Water is sprayed on to the fill and falls to the tower basin. 冷卻水被噴淋在填料上，向下流入冷 卻水槽,Air is blown up through the fill and evaporates some of the water and reduces the water temperature. 空氣從底部強(qiáng)制吹入，在填料內(nèi)與水接觸蒸

11、發(fā)部分冷卻水，從而降低水溫,Types of Cooling Towers,Two types 誘導(dǎo)通風(fēng)冷卻塔分兩類： Cross flow 橫流式誘導(dǎo)通風(fēng)冷卻塔 Counter flow 逆流式誘導(dǎo)通風(fēng)冷卻塔,Induced Draft Cooling Towers 誘導(dǎo)通風(fēng)冷卻塔,Types of Cooling Towers,Advantage: less recirculation than forced draft towers & lower motor running cost 優(yōu)勢(shì)：回流程度低于強(qiáng)制通風(fēng)冷卻塔；風(fēng)機(jī)運(yùn) 行費(fèi)用小于強(qiáng)制通風(fēng)冷卻塔。 Disadvantage: fa

12、ns and motor drive mechanism require weather-proofing 劣勢(shì)：風(fēng)扇與電機(jī)的機(jī)械傳動(dòng)需要防水設(shè)計(jì),Types of Cooling Towers,Hot water enters at the top 熱水從頂部進(jìn)入冷卻塔 Air enters at bottom and exits at top 空氣通過風(fēng)扇強(qiáng)制誘導(dǎo)，從底部進(jìn)入冷卻塔 Uses induced draft fans 使用強(qiáng)制誘導(dǎo)風(fēng)扇,Induced Draft Counter Flow CT,23,Cooling Tower Basics,Induced Draft 誘導(dǎo)通風(fēng)

13、 Counter flow Tower 逆流式,Water is sprayed on to the Fill and falls to the tower Basin 冷卻水從頂部噴入，流經(jīng)填料層進(jìn)入冷卻水槽,Air is drawn through the Fill and evaporates some Of the water and reduces The remaining water temperature. 空氣由誘導(dǎo)風(fēng)機(jī)引入冷卻塔從底部，在填料內(nèi)與水接觸蒸發(fā)部分冷卻水，從而降低水溫,Cooling Tower Basics,Due to their pressurized s

14、pray water distribution system 因?yàn)榇祟惱鋮s塔內(nèi)的加壓配水噴淋裝置： Advantages 優(yōu)勢(shì): Increased tower height accommodates longer ranges and closer approaches 通過增加塔的高度來獲得更長(zhǎng)的換熱流程與更小的冷幅 More efficient use of air due to finer droplet size from pressure sprays 由于加壓噴淋裝置可以噴出更小的水滴，因此換熱效率較高,Induced draft counter flow 逆流式誘導(dǎo)通風(fēng)冷卻塔,

15、Cooling Tower Basics,Disadvantages 劣勢(shì)： Increased system pumping head requirements 系統(tǒng)水泵壓頭增加 Increased energy consumption and operating costs 能量需求增大，運(yùn)行費(fèi)用增加 Distribution nozzles difficult to inspect and clean 冷卻水噴頭不易維護(hù)和清潔 Requires extra distributor and external piping costs 需要配水系統(tǒng)以及相關(guān)管路，因此初投資增加,Types o

16、f Cooling Towers,Water enters top and passes over fill 冷卻水從頂部進(jìn)入，流經(jīng)填料層 Air enters on one side or opposite sides 空氣從一側(cè)或兩側(cè)進(jìn)入 Induced draft fan draws air across fill 誘導(dǎo)風(fēng)機(jī)使空氣橫向流過填料層,Induced Draft Cross Flow CT 橫流式誘導(dǎo)通風(fēng)冷卻塔,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. 冷卻水噴淋至填料層，從頂部 流至底部的冷卻水槽,Air is drawn through the Fill and evaporates some Of the water and reduces The water temperature. Less air required 空氣由誘導(dǎo)風(fēng)機(jī)引入冷卻塔側(cè)面，在填料內(nèi)橫向流動(dòng)與水接觸蒸發(fā)部分冷卻水，從而降低水溫,Cooling Tower Basics,Due to their gravity flow ho

18、t water distribution system 由于此類冷卻塔的水屬于自然流配水系統(tǒng)： Advantages 優(yōu)勢(shì)： Low pumping head 低水泵壓頭 Lower first cost pumping systems 較低的水泵初投資 Lower annual energy consumption and operating costs 較低的年運(yùn)行能耗和費(fèi)用 Accepts larger variation in water flow without adverse effect on the water distribution pattern 流量變化較大時(shí)不會(huì)對(duì)配水

19、系統(tǒng)造成不利的影響,Induced draft cross flow 橫流式誘導(dǎo)通風(fēng)冷卻塔,Cooling Tower Basics,Disadvantages 劣勢(shì)： Low pressure head on the distribution pan may encourage orifice clogging and less water breakup at spray nozzle 低壓頭會(huì)導(dǎo)致噴頭易于堵塞以及冷卻水噴出時(shí)不能很好的分散成細(xì)密水霧 Exposure to air in the hot water basin may accelerate algae growth 熱水水

20、槽直接暴露于空氣中會(huì)導(dǎo)致藻類的滋生 Larger footprint 占地面積較大,Training Agenda: Cooling Towers,Introduction 簡(jiǎn)介 Types of cooling towers 類型 Assessment of cooling towers 評(píng)估 Energy efficiency opportunities 節(jié)能方案,Assessment of Cooling Towers,Measured Parameters 應(yīng)測(cè)量的參數(shù),Wet bulb temperature of air 空氣濕球溫度 Dry bulb temperature of

21、 air 空氣干球溫度 Cooling tower inlet water temperature 冷卻塔進(jìn)水溫度 Cooling tower outlet water temperature 冷卻塔出水溫度 Electrical readings of pump and fan motors 水泵和電機(jī)運(yùn)行參數(shù) Water flow rate 水流速度 Air flow rate 空氣流速,Performance Parameters 運(yùn)行參數(shù),Range 冷卻水溫差 Approach 冷幅 Effectiveness 效率 Cooling capacity 冷卻塔容量 Evaporatio

22、n loss 蒸發(fā)損失 Cycles of concentration 濃縮倍數(shù) Blow down losses 排污損失 Liquid / Gas ratio 液體/氣體比,Assessment of Cooling Towers,1. Range 冷卻水溫差,Difference between cooling water inlet and outlet temperature: 冷卻水進(jìn)出水溫差： Range (C) = CW inlet temp CW outlet temp High range = good performance 大溫差 = 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: 冷卻塔出水溫度與入口空氣濕球溫度的差值： 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=冷卻水溫差/（冷卻水溫差+冷幅） High effectiveness = good performance 高效率=高性能,Assessment of Cooling Towers,4. Cooling Capacity 冷卻塔容量,Heat rejected in kCal/hr or tons of refrigeration (TR) = mass flow rate of water X specific heat X temperature difference 冷卻塔容量單位為“千卡每小時(shí)”或者“冷噸” 冷卻塔

25、容量=冷卻水質(zhì)量流量X水的比熱容X溫差 High cooling capacity = good performance 大容量=高性能,Assessment of Cooling Towers,5. Evaporation Loss 蒸發(fā)損失,Water quantity (m3/hr) evaporated for cooling duty 蒸發(fā)損失的單位為(m3/hr) ，表示每小時(shí)因?yàn)槔鋮s而損失的水量 = theoretically, 1.8 m3 for every 10,000,000 kCal heat rejected 理論上蒸發(fā)損失為1.8立方米/1千萬千卡 = 0.0008

26、5 x 1.8 x 流量 (m3/hr) x 冷卻水溫差,Assessment of Cooling Towers,Assessment of Cooling Towers,5. Evaporation Loss 蒸發(fā)損失,Cooling Tower Industry (CTI) Rates Towers At ARI Condenser Water 工業(yè)冷卻塔的ARI工況： Water flow rate across cooling tower = 0.054 (L/s) / Kw 冷卻塔流量 = 0.054 (L/s) / Kw Cooling tower capacity = 3500

27、kW 冷卻塔容量 = 3500kW 29.4 Leaving Fluid 出水溫度29.4 35 Entering Fluid 進(jìn)水溫度35 Use the formula from previous page 應(yīng)用前一頁的公式: = 0.00085 x 1.8 x 流量 (m3/hr) x 冷卻水溫差 = 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 一個(gè)3500kW冷卻塔的冷

28、卻水蒸發(fā)量為5820升每小時(shí),Assessment of Cooling Towers,6. Cycles of concentration 濃縮倍數(shù),Ratio of dissolved solids in circulating water to the dissolved solids in make up water 循環(huán)水中固態(tài)溶解物含量與補(bǔ)充水中固態(tài)溶解物的含量之比 Increase this to reduce water loss 增加此比例可減小蒸發(fā)損失,7. Blow-down 排污量,Depend on cycles of concentration and the ev

29、aporation losses 決定于循環(huán)水濃度與蒸發(fā)損失 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 = 為將固態(tài)溶解物和其他雜質(zhì)濃度維持在可接受范圍內(nèi)而排出的循環(huán)水量 = 蒸發(fā)損失/（ C.O.C. 1）,8. Liquid Gas (L/G) Ratio 液氣比,Ratio between wate

30、r and air mass flow rates 水與空氣的質(zhì)量流量之比 Heat removed from the water must be equal to the heat absorbed by the surrounding air 冷卻水散發(fā)的熱量等于空氣吸收的熱量 L(T1 T2) = G(h2 h1) L/G = (h2 h1) / (T1 T2) T1 = hot water temp (oC) 熱水溫度（冷卻塔進(jìn)水） T2 = cold water temp (oC) 冷水溫度（冷卻塔出水） Enthalpy of air water vapor mixture at

31、inlet wet bulb temp (h1) and outlet wet bulb temp (h2) 冷卻塔進(jìn)口（空氣與水蒸氣混合）溫度對(duì)應(yīng)的焓值(h1)與出口溫度（濕球溫度）的焓值(h2),Assessment of Cooling Towers,41,Cooling Tower Process 冷卻塔工作流程,1. Air Enters at 35 DB 26 WB 空氣35 DB 26 WB 2. Air Leaves Saturated at 30.8 2. 30.8 飽和空氣離開冷卻塔 3. Entering Air Enthalpy is 78.5 kJ/kg 3. 進(jìn)口空

32、氣的焓值是78.5kJ/kg 4. Leaving Air Enthalpy is 103.9 kJ/kg 出口空氣的焓值是103.9kJ/kg 5. Water Vaporized Latent Heat is 2430 kJ/kg 11 g water absorbs 26.7 kJ heat during evaporating 5. 蒸汽的潛伏熱值是2430 kJ/kg，11g的水吸取26.7kJ的熱量 6. Air Sensible heat is 26.7 25.4 = 1.3 kJ 6. 空氣的感熱為 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 簡(jiǎn)介 Types of cooling towers 類型 Assessment of cooling towers 評(píng)估 Energy efficiency opportunities 節(jié)能方案,Energy Efficiency Opportunities,Selecting a cooling tower 選擇冷卻塔 Fills 填料 Pumps a

34、nd water distribution 水泵與配水設(shè)備 Fans and motors 風(fēng)扇與電機(jī),Energy Efficiency Opportunities,1. Selecting a cooling tower 選擇冷卻塔,Capacity 冷卻塔容量 Heat dissipation (kCal/hour) 散熱量 (kCal/hour) Circulated flow rate (m3/hr) 循環(huán)水流量 (m3/hr) Other factors 其它因素,Energy Efficiency Opportunities,Range 冷卻水溫差 Range determine

35、d by process, not by system 冷卻水溫差取決于換熱過程而不是設(shè)備 Approach 冷幅 Closer to the wet bulb temperature = Bigger size cooling tower = More expensive 越接近濕球溫度 = 更大的冷卻塔 = 更多的投資,1. Selecting a cooling tower,Energy Efficiency Opportunities,Heat Load 熱負(fù)荷 Determined by process 決定于換熱過程 Required cooling is controlled b

36、y the desired operating temperature 合適的工況下才能保證需要的冷量 High heat load = large size and cost of cooling tower 熱負(fù)荷大 = 更大的冷卻塔與更多的設(shè)備費(fèi)用,1. Selecting a cooling tower,Energy Efficiency Opportunities,Wet bulb temperature considerations: 關(guān)于濕球溫度 Water is cooled to temp higher than wet bulb temp 冷卻水出水溫度高于空氣濕球溫度 C

37、onditions at tower site 冷卻塔坐落位置的具體情況 Not to exceed 5% of design wet bulb temp 濕球溫度不可高于設(shè)計(jì)濕球溫度的5%及以上 The designed wet bulb temp is refer to ambient WB (preferred) or inlet 此濕球溫度指的是環(huán)境濕球溫度（推薦）或者空氣入口處濕球溫度 Can tower deal with increased wet bulb temp? 冷卻塔能否適應(yīng)較高的濕球溫度,Relationship range, flow and heat load 溫

38、差，流量與熱負(fù)荷的關(guān)系,Range increases with increased： 以下兩項(xiàng)增加的情況下溫差會(huì)增大： Amount circulated water (flow) 循環(huán)水量（流量） Heat load 熱負(fù)荷 Causes of range increase 溫差增大的原因如下： Inlet water temperature increases 進(jìn)水溫度升高 Exit water temperature decreases 出水溫度降低 Consequence = larger tower 冷卻水溫差增大 = 更大的冷卻塔,Wet bulb temperature inf

39、luence on chiller performance 濕球溫度對(duì)機(jī)組運(yùn)行的影響,Lowering condenser water impact on chiller improvement 冷卻水溫下降對(duì)機(jī)組性能的影響,0.56 Deg C,Lowering condenser water impact on cooling tower 冷卻水溫下降對(duì)機(jī)組性能的影響,3.9 Deg C,Get temperature data from customer 用戶提供的濕球溫度變化圖,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 熱水經(jīng)過配水設(shè)備流經(jīng)填料介質(zhì)，蒸發(fā)降溫 Fill media impacts electricity use 填料介質(zhì)影響冷卻塔用電量 Efficiently designed fill media reduces pumping costs 高效填料介質(zhì)可以節(jié)約管路投資 Fill media influences heat exchange: surface area, duration of contact, turbulence 填料介質(zhì)影響換熱效率：表面積，接觸時(shí)間與湍流,2. Fill media 填料,Energy Efficiency Opportunities,Comparing 3 fill media: film fill more efficient 比較三種填料介質(zhì) ：水膜填料效率最高,2. Fill media 填料介質(zhì),Energy Efficiency Opportunities,Pumps: see pumps session 水泵：見水泵部