摘要:為了探究熔鹽儲能系統中熔鹽電加熱器不同布置形式的優劣問題,以某熔鹽儲能項目為研究對象,分析系統中熔鹽電加熱器的布置特點及其內部的熔鹽工質熱動力模擬,總結不同布置形式的利弊,為熔鹽儲能項目中熔鹽電加熱的布置設計提供參考。
引言:熔鹽儲(chu)(chu)能(neng)(neng)(neng)技(ji)術是目(mu)前的(de)主流高(gao)溫(wen)儲(chu)(chu)能(neng)(neng)(neng)技(ji)術之一,具有成本低、熱(re)容(rong)高(gao)、安全(quan)性好等優點,已在西(xi)班牙等國的(de)太陽(yang)能(neng)(neng)(neng)光(guang)熱(re)發電(dian)項目(mu)中得到實(shi)際應用[1]。某熔鹽儲(chu)(chu)能(neng)(neng)(neng)供(gong)蒸(zheng)汽項目(mu)利用夜間低谷電(dian)驅(qu)動熔鹽電(dian)加熱(re)器對熔鹽工質(zhi)進(jin)行(xing)加熱(re)儲(chu)(chu)存,峰電(dian)時(shi)段(duan)作為替代(dai)熱(re)源(yuan)進(jin)行(xing)蒸(zheng)汽供(gong)應。熔鹽儲(chu)(chu)能(neng)(neng)(neng)技(ji)術利用材料的(de)潛熱(re)儲(chu)(chu)存熱(re)量,將低谷電(dian)以熱(re)能(neng)(neng)(neng)形(xing)式儲(chu)(chu)存,實(shi)現(xian)“削(xue)峰填谷”、節約(yue)能(neng)(neng)(neng)源(yuan)。
熔(rong)(rong)鹽(yan)(yan)儲(chu)能系(xi)(xi)統(tong)運行過程中(zhong),利用熔(rong)(rong)鹽(yan)(yan)工質(zhi)的顯熱溫(wen)(wen)(wen)區,低谷電(dian)驅動熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)熱器(qi)加(jia)熱低溫(wen)(wen)(wen)熔(rong)(rong)鹽(yan)(yan),使(shi)其(qi)升(sheng)溫(wen)(wen)(wen)至設計溫(wen)(wen)(wen)度后儲(chu)存于(yu)熔(rong)(rong)鹽(yan)(yan)儲(chu)罐(guan)內(nei)(nei)(nei);電(dian)力尖(jian)峰(feng)時(shi)段,利用熔(rong)(rong)鹽(yan)(yan)換熱系(xi)(xi)統(tong)使(shi)熔(rong)(rong)鹽(yan)(yan)罐(guan)內(nei)(nei)(nei)的高(gao)溫(wen)(wen)(wen)熔(rong)(rong)鹽(yan)(yan)進行熱量轉移,替(ti)補峰(feng)段內(nei)(nei)(nei)的部分熱量,減(jian)少峰(feng)段能源消耗(hao)。其(qi)中(zhong),融(rong)化溫(wen)(wen)(wen)區為(wei)140~210℃的熔(rong)(rong)鹽(yan)(yan)工質(zhi)多應用于(yu)熔(rong)(rong)鹽(yan)(yan)儲(chu)能系(xi)(xi)統(tong),使(shi)用特定溫(wen)(wen)(wen)區的熔(rong)(rong)鹽(yan)(yan)工質(zhi)作為(wei)儲(chu)能材(cai)料時(shi),需(xu)同步考慮(lv)系(xi)(xi)統(tong)核心設備熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)熱器(qi)的設計制(zhi)造及安裝(zhuang)。受建設場地規(gui)模的影(ying)響,熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)熱器(qi)的布(bu)置方(fang)案包括臥式和立式形式,布(bu)置方(fang)式直接影(ying)響熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)熱器(qi)的壽命周期(qi)和占地面積。
介(jie)紹熔(rong)(rong)鹽電(dian)加(jia)熱器在熔(rong)(rong)鹽儲能系統(tong)應用(yong)中的(de)優化模擬(ni)分(fen)析,使用(yong)建模軟件SolidWorks和其(qi)綁定的(de)熱動力模擬(ni)軟件Flow Simulation對不同布置形式下熔(rong)(rong)鹽電(dian)加(jia)熱器的(de)運行工(gong)況進行模擬(ni)分(fen)析,以計(ji)算得到(dao)的(de)模擬(ni)數據為依據,為后續系統(tong)設計(ji)提(ti)供參(can)考。
1、熔鹽儲能技術
1.1熔融鹽工質
熔(rong)(rong)鹽(yan)(yan)(yan)儲(chu)能系(xi)統使(shi)用(yong)熔(rong)(rong)鹽(yan)(yan)(yan)作為(wei)儲(chu)能工(gong)(gong)質(zhi),將(jiang)能源以(yi)(yi)熱的(de)(de)形式儲(chu)存在熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質(zhi)中。熔(rong)(rong)鹽(yan)(yan)(yan)是鹽(yan)(yan)(yan)類熔(rong)(rong)化形成(cheng)的(de)(de)熔(rong)(rong)融體(ti),具有傳熱效率高、儲(chu)熱溫區(qu)大及高穩定等(deng)性(xing)能,被應(ying)用(yong)于大規模儲(chu)能工(gong)(gong)藝。以(yi)(yi)不同的(de)(de)使(shi)用(yong)溫區(qu)劃分(fen)(fen)熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質(zhi),根據經驗(yan)將(jiang)熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質(zhi)大致分(fen)(fen)為(wei)高溫(>600℃)、中溫(350~600℃)、低溫(100~350℃)和室溫(<100℃)四大體(ti)系(xi),各體(ti)系(xi)之(zhi)間(jian)無嚴格的(de)(de)溫度界限[2];可以(yi)(yi)按照(zhao)熔(rong)(rong)鹽(yan)(yan)(yan)的(de)(de)不同組分(fen)(fen)進行命名分(fen)(fen)類。文(wen)中的(de)(de)熔(rong)(rong)鹽(yan)(yan)(yan)儲(chu)能系(xi)統中,使(shi)用(yong)組分(fen)(fen)為(wei)7%NaNO3+53%KNO3+40%NaNO2的(de)(de)三元熔(rong)(rong)鹽(yan)(yan)(yan),初始(shi)熔(rong)(rong)化溫度為(wei)142℃,持續升(sheng)溫至150℃完全(quan)熔(rong)(rong)融。
三元(yuan)熔鹽(yan)的(de)物性參(can)數如表1所(suo)示。
1.2熔鹽電加熱器
熔(rong)(rong)鹽(yan)(yan)電加(jia)(jia)(jia)(jia)熱(re)(re)(re)器(qi)與傳統(tong)槽(cao)式(shi)(shi)(shi)電加(jia)(jia)(jia)(jia)熱(re)(re)(re)的(de)原理相同(tong),利用特殊管狀電熱(re)(re)(re)元件結合法(fa)蘭集(ji)束的(de)形式(shi)(shi)(shi)與壓力容器(qi)組成(cheng)供熱(re)(re)(re)整體,主要由(you)電加(jia)(jia)(jia)(jia)熱(re)(re)(re)芯、筒體、封頭和集(ji)線槽(cao)組成(cheng)。熔(rong)(rong)鹽(yan)(yan)電加(jia)(jia)(jia)(jia)熱(re)(re)(re)器(qi)利用電能對槽(cao)內的(de)液態(tai)工(gong)質或氣(qi)態(tai)工(gong)質進行加(jia)(jia)(jia)(jia)熱(re)(re)(re)升(sheng)溫[3],加(jia)(jia)(jia)(jia)熱(re)(re)(re)形式(shi)(shi)(shi)分為(wei)紅外線加(jia)(jia)(jia)(jia)熱(re)(re)(re)、電弧加(jia)(jia)(jia)(jia)熱(re)(re)(re)、電阻式(shi)(shi)(shi)加(jia)(jia)(jia)(jia)熱(re)(re)(re)等(deng),電阻式(shi)(shi)(shi)加(jia)(jia)(jia)(jia)熱(re)(re)(re)形式(shi)(shi)(shi)更適用于熔(rong)(rong)鹽(yan)(yan)儲(chu)能系(xi)統(tong)。與其他熔(rong)(rong)鹽(yan)(yan)工(gong)質加(jia)(jia)(jia)(jia)熱(re)(re)(re)方式(shi)(shi)(shi)相比,熔(rong)(rong)鹽(yan)(yan)電加(jia)(jia)(jia)(jia)熱(re)(re)(re)具有快捷且易(yi)于控制(zhi)等(deng)優(you)點,直接(jie)式(shi)(shi)(shi)加(jia)(jia)(jia)(jia)熱(re)(re)(re)裝置加(jia)(jia)(jia)(jia)熱(re)(re)(re)運行過程中,電加(jia)(jia)(jia)(jia)熱(re)(re)(re)器(qi)內的(de)電加(jia)(jia)(jia)(jia)熱(re)(re)(re)元件產生熱(re)(re)(re)量(liang),通過強制(zhi)對流的(de)方式(shi)(shi)(shi)加(jia)(jia)(jia)(jia)熱(re)(re)(re)介質[4]。電加(jia)(jia)(jia)(jia)熱(re)(re)(re)器(qi)通電發出熱(re)(re)(re)量(liang)為(wei)腔內熔(rong)(rong)鹽(yan)(yan)吸收(shou)熱(re)(re)(re)量(liang),極大地提升(sheng)了(le)電-熱(re)(re)(re)轉換效率,減少了(le)能源浪費。
1.3熔鹽儲能應用
目(mu)前,光伏(fu)、風電(dian)(dian)(dian)等新能(neng)源項目(mu)大規模建(jian)設,但新能(neng)源項目(mu)可能(neng)存(cun)在(zai)發電(dian)(dian)(dian)不(bu)平穩以及發電(dian)(dian)(dian)、用(yong)電(dian)(dian)(dian)的(de)(de)時間(jian)、空(kong)間(jian)不(bu)匹配等特性(xing),現(xian)階段(duan)存(cun)在(zai)棄風、棄光現(xian)象。需要(yao)調(diao)峰的(de)(de)電(dian)(dian)(dian)廠陸續(xu)建(jian)設了熔鹽建(jian)設儲(chu)能(neng)項目(mu),充(chong)分利用(yong)新能(neng)源及電(dian)(dian)(dian)廠的(de)(de)零價(jia)、低價(jia)電(dian)(dian)(dian)量,實現(xian)谷電(dian)(dian)(dian)時段(duan)儲(chu)能(neng),用(yong)電(dian)(dian)(dian)高(gao)峰時發電(dian)(dian)(dian);通過提(ti)供(gong)深度調(diao)峰等電(dian)(dian)(dian)力輔助(zhu)服務,增加對外供(gong)汽(qi)、供(gong)熱(re)的(de)(de)能(neng)力和質量,提(ti)高(gao)盈利能(neng)力。熔鹽儲(chu)能(neng)技術在(zai)清潔供(gong)熱(re)領(ling)(ling)域(yu)、工業蒸(zheng)汽(qi)領(ling)(ling)域(yu)和電(dian)(dian)(dian)力調(diao)峰領(ling)(ling)域(yu)均具有推動作用(yong)。
(1)清(qing)潔(jie)供熱領域。
新(xin)型(xing)熔(rong)鹽儲能供蒸汽系統可以利(li)用(yong)清潔電力滿足用(yong)戶的(de)(de)不同供熱(re)及供蒸汽需(xu)求。針對北京地區,國(guo)家給予了(le)(le)良好的(de)(de)谷電獎勵政(zheng)策,擴(kuo)大(da)了(le)(le)熔(rong)鹽蓄熱(re)的(de)(de)應(ying)用(yong)市場。
(2)工業蒸(zheng)汽領域。
我國待改造(zao)在用燃煤(mei)工業鍋爐(lu)達46.7萬臺,總容量達125萬MW。工業鍋爐(lu)市場蒸(zheng)汽(qi)年(nian)產量為23萬MW,工業蒸(zheng)汽(qi)市場規(gui)模為每年(nian)3 000億(yi)元。隨(sui)著城鎮(zhen)化持(chi)續發展(zhan),預計2050年(nian)時(shi),中(zhong)國的建筑總面積將(jiang)(jiang)超過800億(yi)m2。供蒸(zheng)汽(qi)領域,熔鹽儲能技術將(jiang)(jiang)會被大規(gui)模推廣(guang)使(shi)用。
(3)電力調峰領域。
清潔能(neng)(neng)源(yuan)的(de)(de)利(li)用將大規模(mo)增長,提高(gao)火電運(yun)行(xing)靈活性是火電行(xing)業轉(zhuan)型發(fa)展的(de)(de)重要方向,選(xuan)擇合適的(de)(de)技術路(lu)線是火電廠靈活性改造的(de)(de)關鍵,需要從(cong)調峰(feng)效果、改造成本(ben)和運(yun)行(xing)成本(ben)等方面進行(xing)對(dui)比分析。新(xin)型熔鹽儲能(neng)(neng)技術能(neng)(neng)夠(gou)增加機組低(di)負荷(he)(he)運(yun)行(xing)能(neng)(neng)力(li)和頂(ding)負荷(he)(he)能(neng)(neng)力(li),具有儲能(neng)(neng)密度大、儲能(neng)(neng)溫區廣(guang)的(de)(de)特點,在調峰(feng)領域具有明顯優勢。
2、熔鹽電加熱器模擬及分析
以某熔(rong)(rong)鹽(yan)儲能(neng)(neng)項(xiang)目(mu)為例,利用(yong)SolidWorks軟件(jian)創(chuang)建(jian)熔(rong)(rong)鹽(yan)電(dian)加(jia)熱(re)器的(de)有限(xian)元模(mo)型,控制某一(yi)邊界(jie)條件(jian)進行(xing)熱(re)動力(li)運(yun)(yun)行(xing)模(mo)擬(ni)分(fen)析(xi),得(de)到熔(rong)(rong)鹽(yan)電(dian)加(jia)熱(re)器在熔(rong)(rong)鹽(yan)儲能(neng)(neng)系統中的(de)最優布置形(xing)式,利用(yong)Flow Simulation功(gong)能(neng)(neng)得(de)到熱(re)動力(li)模(mo)擬(ni)分(fen)析(xi)數據,并將其合理地應用(yong)于其他熔(rong)(rong)鹽(yan)儲能(neng)(neng)系統,可(ke)以有效提高熔(rong)(rong)鹽(yan)加(jia)熱(re)器的(de)加(jia)熱(re)效率及運(yun)(yun)行(xing)安全性(xing)。
2.1熔鹽電(dian)加熱器有限元模型的建立
對(dui)熔鹽電(dian)加(jia)熱(re)(re)(re)器(qi)結構進行(xing)逐一拆分(fen)(fen),便于對(dui)各(ge)個零(ling)部件單獨建模。為(wei)了給予不同零(ling)件不同的(de)邊界條件,以實現更顯著的(de)模擬(ni)效果,將熔鹽電(dian)加(jia)熱(re)(re)(re)器(qi)細分(fen)(fen)為(wei)熔鹽電(dian)加(jia)熱(re)(re)(re)器(qi)纜(lan)線端頭、加(jia)熱(re)(re)(re)芯、熔鹽電(dian)加(jia)熱(re)(re)(re)器(qi)外殼及折(zhe)流板等四大零(ling)部件,利用(yong)SolidWorks軟件分(fen)(fen)別建立有限(xian)元模型。
(1)纜線端頭。
熔(rong)鹽(yan)電(dian)加(jia)熱器(qi)的(de)纜(lan)(lan)線(xian)(xian)端頭(tou)主(zhu)要由(you)圓(yuan)形筒(tong)體、配(pei)對法蘭及螺栓等零(ling)件(jian)組成,主(zhu)要作(zuo)用(yong)是匯總熔(rong)鹽(yan)電(dian)加(jia)熱器(qi)加(jia)熱芯(xin)端部的(de)接電(dian)線(xian)(xian)纜(lan)(lan)。所(suo)有加(jia)熱芯(xin)的(de)接電(dian)端均置于熔(rong)鹽(yan)電(dian)加(jia)熱器(qi)纜(lan)(lan)線(xian)(xian)端頭(tou)內部,方便加(jia)熱芯(xin)接線(xian)(xian)端的(de)檢修維護(hu),對加(jia)熱芯(xin)線(xian)(xian)纜(lan)(lan)端進行封(feng)閉式保護(hu)。熔(rong)鹽(yan)電(dian)加(jia)熱器(qi)纜(lan)(lan)線(xian)(xian)端頭(tou)模型前視(shi)基準面(mian)如(ru)圖1所(suo)示。
對熔鹽電加熱器纜(lan)線(xian)(xian)端(duan)頭進(jin)行數(shu)據(ju)化建模,通過平面配(pei)合(he)控(kong)制纜(lan)線(xian)(xian)端(duan)頭與其他(ta)零部(bu)件的(de)位置關系,減少不必要的(de)外部(bu)參考,突(tu)顯纜(lan)線(xian)(xian)端(duan)頭的(de)空間形(xing)態及裝配(pei)位置。
(2)加熱芯。
熔鹽電加(jia)熱(re)(re)(re)器加(jia)熱(re)(re)(re)芯(xin)(xin)(xin)設計(ji)及建(jian)模為(wei)研究重點,需(xu)要提前(qian)設計(ji)布置(zhi)根(gen)數、與熔鹽工質接觸面(mian)(mian)積(ji)等參數。文中加(jia)熱(re)(re)(re)芯(xin)(xin)(xin)為(wei)四層圓周形(xing)環繞布置(zhi),單(dan)根(gen)加(jia)熱(re)(re)(re)芯(xin)(xin)(xin)采用直徑(jing)為(wei)12 mm的U形(xing)插入(ru)式(shi)加(jia)熱(re)(re)(re)芯(xin)(xin)(xin),位(wei)于熔鹽加(jia)熱(re)(re)(re)器殼腔內的有(you)效(xiao)加(jia)熱(re)(re)(re)長度(du)為(wei)3 895 mm,有(you)效(xiao)加(jia)熱(re)(re)(re)面(mian)(mian)積(ji)為(wei)0.295 m2。加(jia)熱(re)(re)(re)芯(xin)(xin)(xin)呈(cheng)側傾斜25°裝配布置(zhi)。中間層為(wei)15根(gen),其次(ci)分別為(wei)35根(gen)、60根(gen)、70根(gen),總計(ji)布置(zhi)180根(gen)U形(xing)插入(ru)式(shi)加(jia)熱(re)(re)(re)芯(xin)(xin)(xin),總有(you)效(xiao)加(jia)熱(re)(re)(re)面(mian)(mian)積(ji)為(wei)53.1 m2。
在SolidWorks軟件(jian)中使用圓(yuan)周(zhou)陣列快速將其裝配至加熱芯固定端側。熔鹽電加熱器加熱芯模型(xing)雙端基準面如圖2所示。
(3)外殼。
熔(rong)鹽電(dian)加(jia)熱(re)(re)器(qi)外殼具有(you)控(kong)(kong)制(zhi)腔內與加(jia)熱(re)(re)芯(xin)接觸流(liu)量(liang)及散熱(re)(re)阻斷作用,考(kao)慮熔(rong)鹽電(dian)加(jia)熱(re)(re)器(qi)的整體布局,通(tong)過(guo)設計模(mo)擬電(dian)加(jia)熱(re)(re)器(qi)外殼控(kong)(kong)制(zhi)尺寸(cun),實現折流(liu)板(ban)、加(jia)熱(re)(re)芯(xin)、進出管口及鞍(an)座的空間(jian)位置(zhi)配合。
利用SolidWorks軟件的旋(xuan)轉(zhuan)、拉伸等功能直接創(chuang)建(jian)外(wai)(wai)徑620 mm、壁厚(hou)10 mm的帶(dai)(dai)橢圓形(xing)封頭(tou)(tou)(tou)的熔(rong)鹽(yan)(yan)(yan)(yan)電(dian)(dian)加(jia)(jia)熱器(qi)外(wai)(wai)殼模(mo)(mo)型,通過拉伸、切除創(chuang)建(jian)水(shui)平y軸方向的熔(rong)鹽(yan)(yan)(yan)(yan)工質(zhi)進(jin)出(chu)管口(kou)(kou),近纜(lan)線端頭(tou)(tou)(tou)處為(wei)入(ru)口(kou)(kou),近封頭(tou)(tou)(tou)處為(wei)出(chu)口(kou)(kou)。熔(rong)鹽(yan)(yan)(yan)(yan)工質(zhi)進(jin)出(chu)管口(kou)(kou)為(wei)模(mo)(mo)擬(ni)熔(rong)鹽(yan)(yan)(yan)(yan)工質(zhi)流動腔(qiang)(qiang)的邊(bian)界條件,熱動力模(mo)(mo)擬(ni)需(xu)要完全密閉的內部腔(qiang)(qiang)體(ti),實(shi)現(xian)熔(rong)鹽(yan)(yan)(yan)(yan)工質(zhi)邊(bian)界條件的設定。在(zai)熔(rong)鹽(yan)(yan)(yan)(yan)電(dian)(dian)加(jia)(jia)熱器(qi)外(wai)(wai)殼的熔(rong)鹽(yan)(yan)(yan)(yan)工質(zhi)進(jin)出(chu)口(kou)(kou)管口(kou)(kou)處使用便(bian)捷(jie)端蓋功能,直接以管口(kou)(kou)外(wai)(wai)端面(mian)為(wei)契合面(mian)裝(zhuang)配端蓋。熔(rong)鹽(yan)(yan)(yan)(yan)電(dian)(dian)加(jia)(jia)熱器(qi)外(wai)(wai)殼前(qian)視基(ji)準面(mian)剖面(mian)(帶(dai)(dai)端蓋)如圖3所示(shi)。
(4)折流板。
熔(rong)鹽電加熱(re)(re)(re)器(qi)折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban)與熱(re)(re)(re)交換器(qi)中的折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban)作(zuo)用相同,固(gu)定支承加熱(re)(re)(re)芯管束,增大其(qi)內部熔(rong)鹽工質流(liu)(liu)(liu)(liu)動范圍,提高(gao)熱(re)(re)(re)傳遞效率。設計裝配6塊直徑600 mm的折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban),分別為3塊上切(qie)口(kou)(kou)折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban)及3塊下切(qie)口(kou)(kou)折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban),每塊折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban)限位尺(chi)寸530 mm。折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban)中孔(kong)位依(yi)照(zhao)加熱(re)(re)(re)芯的排(pai)布進行拉伸切(qie)除。熔(rong)鹽加熱(re)(re)(re)器(qi)折(zhe)(zhe)(zhe)(zhe)流(liu)(liu)(liu)(liu)板(ban)(ban)(ban)模型右視基(ji)準面如(ru)圖4所示(shi)。
(5)整體裝配建模。
完(wan)成四大零部件(jian)的設(she)計建模后,新(xin)建零件(jian)裝(zhuang)配(pei)圖,對熔鹽(yan)電加(jia)熱(re)器纜線端(duan)頭、加(jia)熱(re)芯、外(wai)殼及折流板(ban)(ban)進行統一配(pei)合。以熔鹽(yan)電加(jia)熱(re)器纜線端(duan)頭為(wei)(wei)有限(xian)元固定(ding)位置(zhi),將加(jia)熱(re)芯、折流板(ban)(ban)及外(wai)殼依(yi)次面面配(pei)合,其中較為(wei)(wei)關(guan)鍵的為(wei)(wei)折流板(ban)(ban)的配(pei)合參數,將上切口折流板(ban)(ban)與下切口折流板(ban)(ban)限(xian)位530 mm依(yi)次排布。熔鹽(yan)電加(jia)熱(re)器整體裝(zhuang)配(pei)方式如圖5所示(shi)。
2.2熱動力模擬分析
SolidWorks軟(ruan)件中(zhong)的(de)(de)(de)Flow Simulation熱流體仿真模(mo)(mo)(mo)擬(ni)插件可以(yi)在SolidWorks的(de)(de)(de)建模(mo)(mo)(mo)設計環境下(xia)提供比較完善(shan)的(de)(de)(de)熱動力(li)分(fen)析(xi)功(gong)能。Flow Simulation與SolidWorks共享(xiang)同一個(ge)模(mo)(mo)(mo)型數據(ju)庫中(zhong)的(de)(de)(de)工質材(cai)料設計數據(ju),節省了(le)建模(mo)(mo)(mo)設計及模(mo)(mo)(mo)擬(ni)分(fen)析(xi)的(de)(de)(de)數據(ju)重復轉換過程。熱動力(li)模(mo)(mo)(mo)擬(ni)分(fen)析(xi)中(zhong)時刻(ke)根據(ju)原始建模(mo)(mo)(mo)數據(ju)進行邊界條件和有計算(suan)域網(wang)格的(de)(de)(de)實時更新及自動運算(suan)。
熔鹽(yan)電加熱器內流體工(gong)質選用三元熔鹽(yan),軟件(jian)內并(bing)未自帶熔鹽(yan)液體工(gong)質,需提前錄入設計(ji)溫區的相關物性(xing)參數,以便后續求(qiu)解計(ji)算使(shi)用。
2.2.1臥式(shi)熔鹽電加(jia)熱器熱動力(li)模擬(ni)
(1)模擬基礎(chu)條(tiao)件:設(she)定(ding)內(nei)部分(fen)析類型(xing),排除不(bu)具備流(liu)(liu)體(ti)條(tiao)件的腔;設(she)定(ding)固體(ti)內(nei)部熱傳(chuan)導,固體(ti)材料為(wei)(wei)不(bu)銹鋼(gang)321;設(she)定(ding)臥式重力,重力方(fang)向y軸,方(fang)向分(fen)量(liang)-9.81 m/s2;設(she)定(ding)默認(ren)流(liu)(liu)體(ti)為(wei)(wei)用戶自定(ding)義的熔(rong)鹽工質,流(liu)(liu)動特征為(wei)(wei)層流(liu)(liu)和湍(tuan)流(liu)(liu);設(she)定(ding)壁面為(wei)(wei)絕熱條(tiao)件。
(2)模擬邊界條件:計算域(yu)為(wei)(wei)熔(rong)鹽(yan)電(dian)(dian)加(jia)(jia)熱(re)(re)(re)器整體(ti)有限元(yuan)立(li)體(ti)區域(yu);熱(re)(re)(re)源為(wei)(wei)熔(rong)鹽(yan)電(dian)(dian)加(jia)(jia)熱(re)(re)(re)器加(jia)(jia)熱(re)(re)(re)芯,單位面(mian)積熱(re)(re)(re)功耗26 000 W/m2;熔(rong)鹽(yan)電(dian)(dian)加(jia)(jia)熱(re)(re)(re)器熔(rong)鹽(yan)工(gong)質流入管口(kou)質量流量為(wei)(wei)3 kg/s,溫(wen)度(du)180℃,壓(ya)力(li)0.401 MPa;熔(rong)鹽(yan)電(dian)(dian)加(jia)(jia)熱(re)(re)(re)器熔(rong)鹽(yan)工(gong)質流出管口(kou)為(wei)(wei)總壓(ya)為(wei)(wei)0.301 MPa的壓(ya)力(li)開口(kou),設定出口(kou)溫(wen)度(du)為(wei)(wei)390℃。
(3)求(qiu)解目標:求(qiu)解熔鹽工質(zhi)進出口的運行溫度平均值,用于控制(zhi)目標收斂。
(4)全局(ju)求(qiu)解:通過模(mo)型基礎條(tiao)件及邊界目標等條(tiao)件的(de)設計控制,利用Flow Simulation功能進行全局(ju)求(qiu)解,得到熔(rong)(rong)鹽(yan)電加熱(re)器在臥式布置情況下的(de)內部熔(rong)(rong)鹽(yan)工(gong)質(zhi)的(de)熱(re)流(liu)動數據。
臥式熔(rong)鹽(yan)電加(jia)熱器(qi)前視基準面等高線溫區切面如(ru)圖6所示,臥式熔(rong)鹽(yan)電加(jia)熱器(qi)流動軌跡如(ru)圖7所示。
2.2.2立式熔鹽電加熱器熱動力模(mo)擬
(1)模擬(ni)(ni)基礎條件(jian):設定立式重力,重力方向x軸,方向分量-9.81 m/s2;其余條件(jian)與臥(wo)式熔鹽電加熱(re)器熱(re)動力模擬(ni)(ni)過(guo)程(cheng)相同。
(2)模擬邊界條(tiao)件和求解目標與臥式熔鹽電(dian)加熱(re)器熱(re)動力模擬過程相同(tong)。
(3)全局求解:立式熔鹽電加熱器前視基準面等高線溫區切面如(ru)圖8所示,立式熔鹽電加熱器流動(dong)軌(gui)跡如(ru)圖9所示。
2.3熱動力模擬分析
分析熔(rong)(rong)鹽電(dian)(dian)加熱(re)(re)器熱(re)(re)動力模擬的流動軌跡,臥(wo)式布(bu)置情況(kuang)下(xia),電(dian)(dian)加熱(re)(re)器下(xia)切口折(zhe)流板(ban)的內角側(ce)(ce)出現(xian)(xian)明顯的流動不均(jun)勻現(xian)(xian)象(xiang),線性(xing)軌跡明顯大(da)量(liang)空缺,死區溫(wen)度(du)過熱(re)(re),達528℃;立式布(bu)置的熔(rong)(rong)鹽電(dian)(dian)加熱(re)(re)器內部(bu)熔(rong)(rong)鹽工質溫(wen)度(du)上升均(jun)勻,雖折(zhe)流板(ban)內角側(ce)(ce)也出現(xian)(xian)流動不均(jun)勻現(xian)(xian)象(xiang),但受重力影(ying)響,內角側(ce)(ce)未出現(xian)(xian)局部(bu)過熱(re)(re)現(xian)(xian)象(xiang)。
分析(xi)臥式(shi)及立式(shi)熔鹽(yan)電(dian)加熱(re)器(qi)的(de)(de)等高線溫(wen)(wen)區(qu)切(qie)面(mian),臥式(shi)布(bu)置時(shi)(shi)出(chu)現(xian)(xian)明顯(xian)的(de)(de)局部(bu)溫(wen)(wen)度過高現(xian)(xian)象(xiang)(xiang),溫(wen)(wen)度達528℃,重(zhong)力為y軸(zhou)負(fu)(fu)方向(xiang),所(suo)有(you)腔(qiang)內熔鹽(yan)工(gong)質均受到向(xiang)y軸(zhou)負(fu)(fu)方向(xiang)的(de)(de)重(zhong)力加速度,腔(qiang)體上端易出(chu)現(xian)(xian)流(liu)動死區(qu)。立式(shi)布(bu)置時(shi)(shi)出(chu)現(xian)(xian)輕微(wei)局部(bu)溫(wen)(wen)度過高現(xian)(xian)象(xiang)(xiang),溫(wen)(wen)度約440℃,死區(qu)的(de)(de)折(zhe)流(liu)板內角側因x軸(zhou)負(fu)(fu)方向(xiang)的(de)(de)重(zhong)力因素(su)易出(chu)現(xian)(xian)強(qiang)制下流(liu)現(xian)(xian)象(xiang)(xiang),不(bu)易形成流(liu)動死區(qu),產生局部(bu)高溫(wen)(wen)現(xian)(xian)象(xiang)(xiang)。
電(dian)加熱器中,出現(xian)(xian)流動(dong)死區極容易(yi)造成腔內局部(bu)高溫(wen),模擬過(guo)程易(yi)出現(xian)(xian)全(quan)局計(ji)算問(wen)題,推(tui)斷(duan)存在(zai)融(rong)化(hua)腔體的可能(neng)。熔鹽(yan)儲能(neng)系統的實際運行過(guo)程中,內部(bu)環境為非可視狀態(tai),只能(neng)在(zai)熔鹽(yan)電(dian)加熱器出廠前(qian)確定折(zhe)流板安裝位置(zhi)及數量,在(zai)易(yi)出現(xian)(xian)死區位置(zhi)增設多點位的高溫(wen)溫(wen)度(du)探頭,以確保運行過(guo)程中的溫(wen)度(du)數據采(cai)集和實時(shi)監控。
3、結語
熔(rong)鹽(yan)電(dian)加熱(re)器加熱(re)芯的有效加熱(re)面積(ji)為56.11 m2,單位(wei)面積(ji)熱(re)功耗(hao)為26 000 W/m2。相同邊界(jie)條件下,臥式(shi)布(bu)(bu)置(zhi)和立式(shi)布(bu)(bu)置(zhi)的熔(rong)鹽(yan)電(dian)加熱(re)器在熱(re)動力(li)模擬方面具有較(jiao)為明顯(xian)的差別。與立式(shi)布(bu)(bu)置(zhi)相比,臥式(shi)布(bu)(bu)置(zhi)出現(xian)較(jiao)為明顯(xian)的熔(rong)鹽(yan)死區,出現(xian)局部高溫(wen)528℃,立式(shi)布(bu)(bu)置(zhi)未(wei)出現(xian)局部高溫(wen),腔內最高溫(wen)度約440℃。熔(rong)鹽(yan)儲能系(xi)統中應優(you)先選取(qu)立式(shi)安裝(zhuang)布(bu)(bu)置(zhi)形式(shi)。
使用Flow Simulation對某熔鹽(yan)儲能系統中熔鹽(yan)電加(jia)熱(re)(re)器的(de)臥、立(li)式布(bu)置形(xing)式進(jin)行(xing)(xing)數據化運(yun)(yun)行(xing)(xing)分析,探(tan)求最(zui)優布(bu)置形(xing)式。以(yi)(yi)熱(re)(re)動力模擬的(de)數據結(jie)果進(jin)行(xing)(xing)分析,立(li)式布(bu)置可(ke)以(yi)(yi)在節省占地面積的(de)同時,有效提高電加(jia)熱(re)(re)的(de)加(jia)熱(re)(re)效果,降低(di)(di)運(yun)(yun)行(xing)(xing)風險,在對應運(yun)(yun)行(xing)(xing)模擬數據佐證的(de)情況(kuang)下,可(ke)以(yi)(yi)在設計初期降低(di)(di)其設計及投資成本。
熔(rong)鹽儲(chu)能(neng)技(ji)術作為新興的(de)清潔能(neng)源技(ji)術,具(ju)有廣(guang)泛(fan)的(de)應(ying)用前景,隨(sui)著熔(rong)鹽儲(chu)能(neng)系統不斷成熟和(he)(he)優(you)化完善,儲(chu)能(neng)效(xiao)率和(he)(he)換(huan)熱效(xiao)率逐步(bu)提高,熔(rong)鹽儲(chu)能(neng)系統將得到廣(guang)泛(fan)普及。
注:本文轉自《節能基礎科學》期刊,聯合作者為北京熱力市政工程建設有限公司鄭策、曾祥靜、閆碩,北京民利儲能技術有限公司穆世慧、于思源等。轉載此文是出于傳遞更多信息之目的,若有來源標注錯誤或侵犯了您的合法權益,請作者與本網聯系。