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(rong)(rong)鹽(yan)(yan)儲能(neng)技術(shu)是目前的主流高溫儲能(neng)技術(shu)之一,具有成本低、熱(re)容高、安全性好等優點,已在西班牙等國的太陽(yang)能(neng)光(guang)熱(re)發電項目中(zhong)得到實際應用[1]。某熔(rong)(rong)鹽(yan)(yan)儲能(neng)供(gong)蒸汽項目利用夜間低谷(gu)(gu)電驅動熔(rong)(rong)鹽(yan)(yan)電加(jia)熱(re)器對熔(rong)(rong)鹽(yan)(yan)工質進(jin)行加(jia)熱(re)儲存(cun),峰電時段(duan)作為替代(dai)熱(re)源進(jin)行蒸汽供(gong)應。熔(rong)(rong)鹽(yan)(yan)儲能(neng)技術(shu)利用材料的潛(qian)熱(re)儲存(cun)熱(re)量,將低谷(gu)(gu)電以(yi)熱(re)能(neng)形(xing)式儲存(cun),實現“削峰填(tian)谷(gu)(gu)”、節約能(neng)源。
熔鹽(yan)(yan)(yan)(yan)儲能(neng)系統運行過(guo)程中,利(li)用(yong)(yong)熔鹽(yan)(yan)(yan)(yan)工質(zhi)的(de)顯(xian)熱(re)溫(wen)(wen)(wen)(wen)區(qu)(qu),低谷電(dian)(dian)驅動熔鹽(yan)(yan)(yan)(yan)電(dian)(dian)加(jia)(jia)熱(re)器(qi)加(jia)(jia)熱(re)低溫(wen)(wen)(wen)(wen)熔鹽(yan)(yan)(yan)(yan),使(shi)其(qi)升溫(wen)(wen)(wen)(wen)至設(she)計(ji)溫(wen)(wen)(wen)(wen)度后儲存于熔鹽(yan)(yan)(yan)(yan)儲罐(guan)內(nei);電(dian)(dian)力(li)尖(jian)峰時段,利(li)用(yong)(yong)熔鹽(yan)(yan)(yan)(yan)換(huan)熱(re)系統使(shi)熔鹽(yan)(yan)(yan)(yan)罐(guan)內(nei)的(de)高溫(wen)(wen)(wen)(wen)熔鹽(yan)(yan)(yan)(yan)進行熱(re)量轉移,替(ti)補峰段內(nei)的(de)部分熱(re)量,減少峰段能(neng)源消(xiao)耗。其(qi)中,融化溫(wen)(wen)(wen)(wen)區(qu)(qu)為140~210℃的(de)熔鹽(yan)(yan)(yan)(yan)工質(zhi)多(duo)應用(yong)(yong)于熔鹽(yan)(yan)(yan)(yan)儲能(neng)系統,使(shi)用(yong)(yong)特定溫(wen)(wen)(wen)(wen)區(qu)(qu)的(de)熔鹽(yan)(yan)(yan)(yan)工質(zhi)作為儲能(neng)材料時,需同步考(kao)慮系統核心設(she)備熔鹽(yan)(yan)(yan)(yan)電(dian)(dian)加(jia)(jia)熱(re)器(qi)的(de)設(she)計(ji)制造及安裝。受建設(she)場地(di)規模的(de)影響(xiang),熔鹽(yan)(yan)(yan)(yan)電(dian)(dian)加(jia)(jia)熱(re)器(qi)的(de)布(bu)置方(fang)案(an)包括臥(wo)式和(he)立式形式,布(bu)置方(fang)式直接影響(xiang)熔鹽(yan)(yan)(yan)(yan)電(dian)(dian)加(jia)(jia)熱(re)器(qi)的(de)壽(shou)命周期和(he)占(zhan)地(di)面積。
介紹熔鹽(yan)電(dian)加(jia)熱器在(zai)熔鹽(yan)儲能系(xi)統(tong)應用中的(de)優(you)化(hua)模(mo)(mo)(mo)擬(ni)分析,使用建(jian)模(mo)(mo)(mo)軟件SolidWorks和其綁定的(de)熱動力模(mo)(mo)(mo)擬(ni)軟件Flow Simulation對不同布(bu)置形式(shi)下熔鹽(yan)電(dian)加(jia)熱器的(de)運行工況進行模(mo)(mo)(mo)擬(ni)分析,以計算得到的(de)模(mo)(mo)(mo)擬(ni)數據為(wei)依據,為(wei)后續(xu)系(xi)統(tong)設計提供參考。
1、熔鹽儲能技術
1.1熔融鹽工質
熔(rong)(rong)(rong)(rong)(rong)鹽儲(chu)能(neng)(neng)(neng)(neng)系統使用熔(rong)(rong)(rong)(rong)(rong)鹽作為(wei)儲(chu)能(neng)(neng)(neng)(neng)工質,將能(neng)(neng)(neng)(neng)源以熱(re)(re)(re)的形式儲(chu)存在熔(rong)(rong)(rong)(rong)(rong)鹽工質中(zhong)。熔(rong)(rong)(rong)(rong)(rong)鹽是鹽類(lei)熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)形成的熔(rong)(rong)(rong)(rong)(rong)融體(ti),具有(you)傳熱(re)(re)(re)效率高(gao)、儲(chu)熱(re)(re)(re)溫(wen)區(qu)大(da)及高(gao)穩定等性能(neng)(neng)(neng)(neng),被應用于大(da)規模儲(chu)能(neng)(neng)(neng)(neng)工藝。以不同(tong)的使用溫(wen)區(qu)劃(hua)分(fen)熔(rong)(rong)(rong)(rong)(rong)鹽工質,根據經驗將熔(rong)(rong)(rong)(rong)(rong)鹽工質大(da)致分(fen)為(wei)高(gao)溫(wen)(>600℃)、中(zhong)溫(wen)(350~600℃)、低溫(wen)(100~350℃)和室溫(wen)(<100℃)四大(da)體(ti)系,各體(ti)系之間無嚴格(ge)的溫(wen)度界限[2];可以按照熔(rong)(rong)(rong)(rong)(rong)鹽的不同(tong)組(zu)分(fen)進(jin)行命名分(fen)類(lei)。文中(zhong)的熔(rong)(rong)(rong)(rong)(rong)鹽儲(chu)能(neng)(neng)(neng)(neng)系統中(zhong),使用組(zu)分(fen)為(wei)7%NaNO3+53%KNO3+40%NaNO2的三(san)元熔(rong)(rong)(rong)(rong)(rong)鹽,初始熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)溫(wen)度為(wei)142℃,持(chi)續升溫(wen)至150℃完(wan)全熔(rong)(rong)(rong)(rong)(rong)融。
三元熔鹽的物性(xing)參數如表1所示(shi)。
1.2熔鹽電加熱器
熔(rong)鹽電加(jia)熱(re)(re)(re)(re)(re)(re)(re)器(qi)與(yu)傳(chuan)統(tong)槽(cao)式(shi)(shi)(shi)電加(jia)熱(re)(re)(re)(re)(re)(re)(re)的(de)(de)(de)原理相(xiang)同(tong),利用(yong)特殊(shu)管(guan)狀電熱(re)(re)(re)(re)(re)(re)(re)元(yuan)件結合(he)法蘭集(ji)束(shu)的(de)(de)(de)形(xing)式(shi)(shi)(shi)與(yu)壓力容器(qi)組成供熱(re)(re)(re)(re)(re)(re)(re)整體,主要由電加(jia)熱(re)(re)(re)(re)(re)(re)(re)芯、筒(tong)體、封(feng)頭和集(ji)線槽(cao)組成。熔(rong)鹽電加(jia)熱(re)(re)(re)(re)(re)(re)(re)器(qi)利用(yong)電能對(dui)槽(cao)內(nei)(nei)的(de)(de)(de)液態(tai)工質或氣態(tai)工質進行(xing)加(jia)熱(re)(re)(re)(re)(re)(re)(re)升溫[3],加(jia)熱(re)(re)(re)(re)(re)(re)(re)形(xing)式(shi)(shi)(shi)分為(wei)紅外線加(jia)熱(re)(re)(re)(re)(re)(re)(re)、電弧加(jia)熱(re)(re)(re)(re)(re)(re)(re)、電阻式(shi)(shi)(shi)加(jia)熱(re)(re)(re)(re)(re)(re)(re)等(deng)(deng),電阻式(shi)(shi)(shi)加(jia)熱(re)(re)(re)(re)(re)(re)(re)形(xing)式(shi)(shi)(shi)更適用(yong)于熔(rong)鹽儲能系統(tong)。與(yu)其他熔(rong)鹽工質加(jia)熱(re)(re)(re)(re)(re)(re)(re)方式(shi)(shi)(shi)相(xiang)比,熔(rong)鹽電加(jia)熱(re)(re)(re)(re)(re)(re)(re)具有快(kuai)捷且易于控制(zhi)等(deng)(deng)優點,直接式(shi)(shi)(shi)加(jia)熱(re)(re)(re)(re)(re)(re)(re)裝置加(jia)熱(re)(re)(re)(re)(re)(re)(re)運行(xing)過(guo)程(cheng)中,電加(jia)熱(re)(re)(re)(re)(re)(re)(re)器(qi)內(nei)(nei)的(de)(de)(de)電加(jia)熱(re)(re)(re)(re)(re)(re)(re)元(yuan)件產(chan)生(sheng)熱(re)(re)(re)(re)(re)(re)(re)量(liang),通(tong)過(guo)強制(zhi)對(dui)流的(de)(de)(de)方式(shi)(shi)(shi)加(jia)熱(re)(re)(re)(re)(re)(re)(re)介質[4]。電加(jia)熱(re)(re)(re)(re)(re)(re)(re)器(qi)通(tong)電發出熱(re)(re)(re)(re)(re)(re)(re)量(liang)為(wei)腔內(nei)(nei)熔(rong)鹽吸收熱(re)(re)(re)(re)(re)(re)(re)量(liang),極大地提升了電-熱(re)(re)(re)(re)(re)(re)(re)轉換效(xiao)率,減少(shao)了能源浪費。
1.3熔鹽儲能應用
目前,光伏、風(feng)電(dian)(dian)(dian)等(deng)新(xin)(xin)(xin)能(neng)(neng)(neng)源(yuan)項目大規模建設(she),但新(xin)(xin)(xin)能(neng)(neng)(neng)源(yuan)項目可能(neng)(neng)(neng)存在(zai)發電(dian)(dian)(dian)不(bu)平穩(wen)以及(ji)發電(dian)(dian)(dian)、用(yong)電(dian)(dian)(dian)的(de)時(shi)間、空間不(bu)匹配(pei)等(deng)特(te)性(xing),現(xian)(xian)階段(duan)(duan)存在(zai)棄風(feng)、棄光現(xian)(xian)象。需要調峰(feng)的(de)電(dian)(dian)(dian)廠(chang)陸續建設(she)了熔鹽(yan)建設(she)儲(chu)能(neng)(neng)(neng)項目,充分利(li)用(yong)新(xin)(xin)(xin)能(neng)(neng)(neng)源(yuan)及(ji)電(dian)(dian)(dian)廠(chang)的(de)零價、低(di)價電(dian)(dian)(dian)量,實現(xian)(xian)谷電(dian)(dian)(dian)時(shi)段(duan)(duan)儲(chu)能(neng)(neng)(neng),用(yong)電(dian)(dian)(dian)高(gao)峰(feng)時(shi)發電(dian)(dian)(dian);通過(guo)提(ti)供深度調峰(feng)等(deng)電(dian)(dian)(dian)力(li)(li)輔(fu)助服務,增加(jia)對外供汽(qi)、供熱(re)的(de)能(neng)(neng)(neng)力(li)(li)和(he)質(zhi)量,提(ti)高(gao)盈利(li)能(neng)(neng)(neng)力(li)(li)。熔鹽(yan)儲(chu)能(neng)(neng)(neng)技(ji)術在(zai)清潔(jie)供熱(re)領(ling)域(yu)、工業蒸汽(qi)領(ling)域(yu)和(he)電(dian)(dian)(dian)力(li)(li)調峰(feng)領(ling)域(yu)均(jun)具有推動作用(yong)。
(1)清潔供熱領(ling)域。
新型熔鹽(yan)儲能供(gong)蒸汽(qi)系統可以利(li)用(yong)(yong)清潔電力滿足用(yong)(yong)戶的不同供(gong)熱及供(gong)蒸汽(qi)需求。針對北京(jing)地區,國家給予了良好的谷電獎勵政策,擴大了熔鹽(yan)蓄(xu)熱的應用(yong)(yong)市場。
(2)工業(ye)蒸汽領(ling)域。
我國(guo)待(dai)改造在用(yong)燃煤(mei)工業(ye)鍋爐達46.7萬臺,總容(rong)量達125萬MW。工業(ye)鍋爐市場(chang)蒸汽年(nian)(nian)產量為23萬MW,工業(ye)蒸汽市場(chang)規模為每年(nian)(nian)3 000億元。隨著(zhu)城鎮化持續發展,預計2050年(nian)(nian)時,中國(guo)的建筑總面積將超過(guo)800億m2。供蒸汽領域(yu),熔鹽儲能(neng)技(ji)術(shu)將會被(bei)大規模推(tui)廣(guang)使(shi)用(yong)。
(3)電力調峰領域。
清潔能(neng)源的利(li)用將大規模(mo)增長,提高火(huo)電運(yun)行(xing)(xing)靈活(huo)性是(shi)火(huo)電行(xing)(xing)業(ye)轉型(xing)發展的重(zhong)要方向,選(xuan)擇(ze)合適的技術路線是(shi)火(huo)電廠靈活(huo)性改造的關鍵(jian),需要從調峰效果、改造成(cheng)本和(he)運(yun)行(xing)(xing)成(cheng)本等方面進(jin)行(xing)(xing)對比分析。新(xin)型(xing)熔(rong)鹽儲(chu)(chu)能(neng)技術能(neng)夠增加(jia)機組低負荷(he)(he)運(yun)行(xing)(xing)能(neng)力和(he)頂負荷(he)(he)能(neng)力,具有儲(chu)(chu)能(neng)密度(du)大、儲(chu)(chu)能(neng)溫區廣的特點(dian),在調峰領域具有明(ming)顯優勢。
2、熔鹽電加熱器模擬及分析
以某熔(rong)(rong)(rong)鹽儲能項(xiang)目為例,利用SolidWorks軟件創建熔(rong)(rong)(rong)鹽電(dian)加(jia)熱器的有限元模型,控制某一邊界條件進行(xing)(xing)熱動(dong)力(li)運(yun)(yun)行(xing)(xing)模擬(ni)分(fen)析,得到熔(rong)(rong)(rong)鹽電(dian)加(jia)熱器在(zai)熔(rong)(rong)(rong)鹽儲能系統(tong)中(zhong)的最優布置形式,利用Flow Simulation功能得到熱動(dong)力(li)模擬(ni)分(fen)析數(shu)據,并將其(qi)合理地應(ying)用于其(qi)他熔(rong)(rong)(rong)鹽儲能系統(tong),可以有效(xiao)提高熔(rong)(rong)(rong)鹽加(jia)熱器的加(jia)熱效(xiao)率(lv)及(ji)運(yun)(yun)行(xing)(xing)安全(quan)性。
2.1熔鹽電加熱(re)器(qi)有限元(yuan)模型的(de)建(jian)立
對熔(rong)(rong)鹽(yan)(yan)(yan)電(dian)加(jia)熱(re)(re)(re)器(qi)(qi)結構(gou)進行逐一拆分(fen),便于對各個零部件(jian)(jian)單獨(du)建模(mo)。為了(le)給予不同零件(jian)(jian)不同的邊界條(tiao)件(jian)(jian),以(yi)實(shi)現更顯著(zhu)的模(mo)擬效果,將熔(rong)(rong)鹽(yan)(yan)(yan)電(dian)加(jia)熱(re)(re)(re)器(qi)(qi)細(xi)分(fen)為熔(rong)(rong)鹽(yan)(yan)(yan)電(dian)加(jia)熱(re)(re)(re)器(qi)(qi)纜線端頭、加(jia)熱(re)(re)(re)芯(xin)、熔(rong)(rong)鹽(yan)(yan)(yan)電(dian)加(jia)熱(re)(re)(re)器(qi)(qi)外殼及折流板等四大零部件(jian)(jian),利用SolidWorks軟件(jian)(jian)分(fen)別建立有限元(yuan)模(mo)型。
(1)纜線端頭。
熔鹽電(dian)(dian)(dian)加(jia)(jia)(jia)熱(re)器的(de)纜(lan)(lan)線(xian)端(duan)頭主要由圓形筒體、配對法蘭及螺栓等零件組(zu)成,主要作用是匯(hui)總熔鹽電(dian)(dian)(dian)加(jia)(jia)(jia)熱(re)器加(jia)(jia)(jia)熱(re)芯(xin)(xin)端(duan)部的(de)接電(dian)(dian)(dian)線(xian)纜(lan)(lan)。所(suo)(suo)有加(jia)(jia)(jia)熱(re)芯(xin)(xin)的(de)接電(dian)(dian)(dian)端(duan)均置(zhi)于熔鹽電(dian)(dian)(dian)加(jia)(jia)(jia)熱(re)器纜(lan)(lan)線(xian)端(duan)頭內部,方便加(jia)(jia)(jia)熱(re)芯(xin)(xin)接線(xian)端(duan)的(de)檢修(xiu)維護,對加(jia)(jia)(jia)熱(re)芯(xin)(xin)線(xian)纜(lan)(lan)端(duan)進行封(feng)閉式保護。熔鹽電(dian)(dian)(dian)加(jia)(jia)(jia)熱(re)器纜(lan)(lan)線(xian)端(duan)頭模型前視基準面如圖1所(suo)(suo)示。
對熔鹽電加(jia)熱(re)器纜(lan)線端(duan)頭(tou)進行(xing)數據化建模,通過平面配合控(kong)制纜(lan)線端(duan)頭(tou)與其他零部件的(de)位置關(guan)系,減(jian)少不必(bi)要的(de)外(wai)部參(can)考,突顯(xian)纜(lan)線端(duan)頭(tou)的(de)空間形(xing)態及裝配位置。
(2)加熱芯。
熔(rong)鹽(yan)電加熱(re)(re)(re)器加熱(re)(re)(re)芯(xin)設(she)(she)計(ji)及建模為(wei)研究重點,需要(yao)提前設(she)(she)計(ji)布置根(gen)(gen)數、與熔(rong)鹽(yan)工質接觸面積等參數。文中加熱(re)(re)(re)芯(xin)為(wei)四層(ceng)圓周形(xing)環繞布置,單根(gen)(gen)加熱(re)(re)(re)芯(xin)采用(yong)直(zhi)徑為(wei)12 mm的U形(xing)插入式(shi)加熱(re)(re)(re)芯(xin),位于熔(rong)鹽(yan)加熱(re)(re)(re)器殼腔內的有效加熱(re)(re)(re)長度為(wei)3 895 mm,有效加熱(re)(re)(re)面積為(wei)0.295 m2。加熱(re)(re)(re)芯(xin)呈側傾(qing)斜(xie)25°裝配布置。中間層(ceng)為(wei)15根(gen)(gen),其次分別(bie)為(wei)35根(gen)(gen)、60根(gen)(gen)、70根(gen)(gen),總(zong)(zong)計(ji)布置180根(gen)(gen)U形(xing)插入式(shi)加熱(re)(re)(re)芯(xin),總(zong)(zong)有效加熱(re)(re)(re)面積為(wei)53.1 m2。
在SolidWorks軟件中使用圓周陣(zhen)列快速將其(qi)裝配至加熱芯固定端(duan)側。熔鹽電加熱器加熱芯模型雙(shuang)端(duan)基(ji)準面如圖2所示(shi)。
(3)外殼。
熔鹽(yan)電加(jia)熱(re)(re)(re)器(qi)外殼具(ju)有控制(zhi)(zhi)腔內與加(jia)熱(re)(re)(re)芯(xin)接觸(chu)流(liu)量及(ji)散熱(re)(re)(re)阻斷(duan)作用,考慮熔鹽(yan)電加(jia)熱(re)(re)(re)器(qi)的整體布局,通過(guo)設計模(mo)擬電加(jia)熱(re)(re)(re)器(qi)外殼控制(zhi)(zhi)尺寸,實現折流(liu)板、加(jia)熱(re)(re)(re)芯(xin)、進(jin)出(chu)管口及(ji)鞍座的空(kong)間(jian)位置配合。
利用SolidWorks軟件(jian)的(de)旋轉、拉(la)伸等功能(neng)直接(jie)創建(jian)(jian)外(wai)(wai)徑620 mm、壁厚10 mm的(de)帶(dai)(dai)橢圓形封頭(tou)的(de)熔(rong)(rong)鹽(yan)(yan)(yan)電(dian)(dian)加熱(re)(re)(re)器外(wai)(wai)殼(ke)模型,通過拉(la)伸、切除創建(jian)(jian)水平y軸方向的(de)熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質進(jin)出(chu)管口(kou)(kou),近纜線(xian)端(duan)頭(tou)處(chu)為(wei)入口(kou)(kou),近封頭(tou)處(chu)為(wei)出(chu)口(kou)(kou)。熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質進(jin)出(chu)管口(kou)(kou)為(wei)模擬(ni)熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質流動(dong)(dong)腔(qiang)(qiang)的(de)邊(bian)界(jie)條件(jian),熱(re)(re)(re)動(dong)(dong)力模擬(ni)需要(yao)完全(quan)密閉的(de)內(nei)部(bu)腔(qiang)(qiang)體,實現熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質邊(bian)界(jie)條件(jian)的(de)設定。在熔(rong)(rong)鹽(yan)(yan)(yan)電(dian)(dian)加熱(re)(re)(re)器外(wai)(wai)殼(ke)的(de)熔(rong)(rong)鹽(yan)(yan)(yan)工(gong)(gong)質進(jin)出(chu)口(kou)(kou)管口(kou)(kou)處(chu)使用便捷端(duan)蓋功能(neng),直接(jie)以管口(kou)(kou)外(wai)(wai)端(duan)面為(wei)契合面裝配端(duan)蓋。熔(rong)(rong)鹽(yan)(yan)(yan)電(dian)(dian)加熱(re)(re)(re)器外(wai)(wai)殼(ke)前視基(ji)準面剖(pou)面(帶(dai)(dai)端(duan)蓋)如(ru)圖(tu)3所示。
(4)折流板。
熔(rong)(rong)鹽(yan)電加熱(re)器折流(liu)板(ban)(ban)與(yu)熱(re)交換器中的(de)折流(liu)板(ban)(ban)作用相同,固定支承加熱(re)芯管束,增大其(qi)內(nei)部熔(rong)(rong)鹽(yan)工質流(liu)動范圍,提高熱(re)傳遞效率。設計裝配6塊(kuai)直徑(jing)600 mm的(de)折流(liu)板(ban)(ban),分別為(wei)3塊(kuai)上切口折流(liu)板(ban)(ban)及3塊(kuai)下切口折流(liu)板(ban)(ban),每塊(kuai)折流(liu)板(ban)(ban)限(xian)位尺寸530 mm。折流(liu)板(ban)(ban)中孔(kong)位依照加熱(re)芯的(de)排(pai)布進(jin)行拉(la)伸切除。熔(rong)(rong)鹽(yan)加熱(re)器折流(liu)板(ban)(ban)模型(xing)右(you)視(shi)基(ji)準面如圖4所示。
(5)整體裝(zhuang)配(pei)建模(mo)。
完成四(si)大(da)零(ling)部件的(de)設計建模(mo)后,新建零(ling)件裝(zhuang)配(pei)圖(tu),對(dui)熔鹽電加熱器(qi)纜(lan)線端(duan)頭(tou)、加熱芯、外殼及(ji)折(zhe)流(liu)板(ban)進行統(tong)一配(pei)合(he)。以熔鹽電加熱器(qi)纜(lan)線端(duan)頭(tou)為有(you)限元固(gu)定(ding)位置,將加熱芯、折(zhe)流(liu)板(ban)及(ji)外殼依次面(mian)面(mian)配(pei)合(he),其中較為關鍵的(de)為折(zhe)流(liu)板(ban)的(de)配(pei)合(he)參數,將上(shang)切(qie)口折(zhe)流(liu)板(ban)與下切(qie)口折(zhe)流(liu)板(ban)限位530 mm依次排(pai)布。熔鹽電加熱器(qi)整體(ti)裝(zhuang)配(pei)方式如圖(tu)5所示。
2.2熱動力模擬分(fen)析
SolidWorks軟件中的(de)(de)Flow Simulation熱流體仿(fang)真(zhen)模(mo)擬(ni)插件可以在SolidWorks的(de)(de)建模(mo)設(she)計環(huan)境下提供(gong)比較完善的(de)(de)熱動(dong)力分(fen)析功能。Flow Simulation與(yu)SolidWorks共享同一個模(mo)型(xing)數據(ju)庫中的(de)(de)工質(zhi)材料設(she)計數據(ju),節省了建模(mo)設(she)計及模(mo)擬(ni)分(fen)析的(de)(de)數據(ju)重復轉換(huan)過程。熱動(dong)力模(mo)擬(ni)分(fen)析中時刻(ke)根據(ju)原始建模(mo)數據(ju)進行邊界條(tiao)件和有計算域網格的(de)(de)實時更新及自動(dong)運算。
熔鹽(yan)電加熱器內流(liu)體工質選(xuan)用三元熔鹽(yan),軟(ruan)件內并未(wei)自帶熔鹽(yan)液體工質,需提前錄入(ru)設計溫區的相關物性參數,以便后續求解計算(suan)使用。
2.2.1臥(wo)式熔(rong)鹽電加熱(re)器(qi)熱(re)動力模擬
(1)模(mo)擬基礎條(tiao)件(jian):設(she)定(ding)(ding)(ding)內(nei)部分析類型,排除不具備流(liu)(liu)體條(tiao)件(jian)的(de)腔;設(she)定(ding)(ding)(ding)固(gu)體內(nei)部熱傳導,固(gu)體材料為(wei)(wei)不銹鋼(gang)321;設(she)定(ding)(ding)(ding)臥式重力(li),重力(li)方向y軸,方向分量(liang)-9.81 m/s2;設(she)定(ding)(ding)(ding)默認(ren)流(liu)(liu)體為(wei)(wei)用戶自(zi)定(ding)(ding)(ding)義的(de)熔鹽工質,流(liu)(liu)動特征(zheng)為(wei)(wei)層流(liu)(liu)和湍流(liu)(liu);設(she)定(ding)(ding)(ding)壁面(mian)為(wei)(wei)絕熱條(tiao)件(jian)。
(2)模擬邊界條件:計(ji)算域為(wei)(wei)熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)(jia)熱(re)(re)器整體有(you)限元立(li)體區域;熱(re)(re)源為(wei)(wei)熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)(jia)熱(re)(re)器加(jia)(jia)熱(re)(re)芯,單位面積熱(re)(re)功耗26 000 W/m2;熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)(jia)熱(re)(re)器熔(rong)(rong)鹽(yan)(yan)工(gong)質流入管(guan)口質量流量為(wei)(wei)3 kg/s,溫度180℃,壓(ya)力0.401 MPa;熔(rong)(rong)鹽(yan)(yan)電(dian)加(jia)(jia)熱(re)(re)器熔(rong)(rong)鹽(yan)(yan)工(gong)質流出管(guan)口為(wei)(wei)總壓(ya)為(wei)(wei)0.301 MPa的壓(ya)力開口,設定出口溫度為(wei)(wei)390℃。
(3)求解(jie)目標:求解(jie)熔(rong)鹽工質進出口的運行溫度平均值(zhi),用于控制目標收斂。
(4)全(quan)局求解:通(tong)過模型(xing)基(ji)礎條(tiao)件(jian)及邊界目標等條(tiao)件(jian)的設(she)計控制,利用Flow Simulation功能進(jin)行(xing)全(quan)局求解,得到熔鹽電加熱(re)器在臥(wo)式(shi)布置情況(kuang)下的內部熔鹽工(gong)質的熱(re)流動數據(ju)。
臥式熔(rong)鹽(yan)電(dian)(dian)加(jia)熱(re)器前視基準面等高線溫區切面如圖(tu)6所示,臥式熔(rong)鹽(yan)電(dian)(dian)加(jia)熱(re)器流(liu)動軌跡如圖(tu)7所示。
2.2.2立式熔(rong)鹽電加熱(re)器熱(re)動力模擬
(1)模擬基礎條(tiao)件:設定立式(shi)重力(li),重力(li)方向x軸,方向分量-9.81 m/s2;其(qi)余(yu)條(tiao)件與臥式(shi)熔鹽電加熱器熱動力(li)模擬過(guo)程相(xiang)同。
(2)模擬邊界條(tiao)件和(he)求解目(mu)標與臥式熔(rong)鹽電加熱(re)器熱(re)動力模擬過(guo)程相同。
(3)全局(ju)求解:立式熔(rong)鹽(yan)電加(jia)熱器前視基準面等高線(xian)溫區切面如(ru)圖8所示(shi),立式熔(rong)鹽(yan)電加(jia)熱器流動軌(gui)跡如(ru)圖9所示(shi)。
2.3熱動力模擬分析
分析熔鹽電(dian)加熱(re)器(qi)熱(re)動(dong)力模擬的流(liu)(liu)動(dong)軌(gui)跡(ji),臥式(shi)布(bu)置(zhi)情況下(xia),電(dian)加熱(re)器(qi)下(xia)切口折流(liu)(liu)板的內角側(ce)出現(xian)明顯的流(liu)(liu)動(dong)不均(jun)(jun)(jun)勻現(xian)象,線性軌(gui)跡(ji)明顯大(da)量(liang)空缺,死區溫度過(guo)熱(re),達528℃;立式(shi)布(bu)置(zhi)的熔鹽電(dian)加熱(re)器(qi)內部(bu)(bu)熔鹽工質溫度上(shang)升均(jun)(jun)(jun)勻,雖折流(liu)(liu)板內角側(ce)也出現(xian)流(liu)(liu)動(dong)不均(jun)(jun)(jun)勻現(xian)象,但受重力影響(xiang),內角側(ce)未(wei)出現(xian)局部(bu)(bu)過(guo)熱(re)現(xian)象。
分(fen)析臥式及立式熔鹽(yan)電加熱(re)器的等高(gao)線溫(wen)區(qu)切面,臥式布置時出(chu)現(xian)(xian)明顯的局部(bu)(bu)溫(wen)度過(guo)高(gao)現(xian)(xian)象,溫(wen)度達528℃,重(zhong)(zhong)力為y軸負方向(xiang),所有(you)腔(qiang)內熔鹽(yan)工質均(jun)受到向(xiang)y軸負方向(xiang)的重(zhong)(zhong)力加速度,腔(qiang)體上端易出(chu)現(xian)(xian)流動(dong)死(si)區(qu)。立式布置時出(chu)現(xian)(xian)輕微局部(bu)(bu)溫(wen)度過(guo)高(gao)現(xian)(xian)象,溫(wen)度約(yue)440℃,死(si)區(qu)的折(zhe)流板內角側因x軸負方向(xiang)的重(zhong)(zhong)力因素易出(chu)現(xian)(xian)強制下流現(xian)(xian)象,不易形(xing)成流動(dong)死(si)區(qu),產生局部(bu)(bu)高(gao)溫(wen)現(xian)(xian)象。
電加熱器中,出(chu)(chu)現(xian)流動死(si)區(qu)(qu)極容(rong)易(yi)造成(cheng)腔(qiang)(qiang)內局(ju)部高溫(wen)(wen),模擬過(guo)(guo)程(cheng)易(yi)出(chu)(chu)現(xian)全局(ju)計算問題,推斷存在融化(hua)腔(qiang)(qiang)體的可能。熔鹽(yan)儲能系統的實際運(yun)行(xing)過(guo)(guo)程(cheng)中,內部環境(jing)為非可視(shi)狀態,只能在熔鹽(yan)電加熱器出(chu)(chu)廠前確(que)定折(zhe)流板安裝位(wei)置及數(shu)量,在易(yi)出(chu)(chu)現(xian)死(si)區(qu)(qu)位(wei)置增設(she)多(duo)點位(wei)的高溫(wen)(wen)溫(wen)(wen)度探頭,以(yi)確(que)保運(yun)行(xing)過(guo)(guo)程(cheng)中的溫(wen)(wen)度數(shu)據采集和(he)實時監控。
3、結語
熔(rong)鹽電加(jia)(jia)(jia)熱(re)(re)器加(jia)(jia)(jia)熱(re)(re)芯的有效加(jia)(jia)(jia)熱(re)(re)面(mian)積為56.11 m2,單位面(mian)積熱(re)(re)功(gong)耗為26 000 W/m2。相同邊界(jie)條件(jian)下,臥式布(bu)置(zhi)(zhi)(zhi)和立(li)式布(bu)置(zhi)(zhi)(zhi)的熔(rong)鹽電加(jia)(jia)(jia)熱(re)(re)器在熱(re)(re)動力模擬方(fang)面(mian)具有較(jiao)為明(ming)顯(xian)的差別。與(yu)立(li)式布(bu)置(zhi)(zhi)(zhi)相比,臥式布(bu)置(zhi)(zhi)(zhi)出(chu)現(xian)較(jiao)為明(ming)顯(xian)的熔(rong)鹽死區,出(chu)現(xian)局部(bu)高溫(wen)528℃,立(li)式布(bu)置(zhi)(zhi)(zhi)未出(chu)現(xian)局部(bu)高溫(wen),腔內(nei)最高溫(wen)度約440℃。熔(rong)鹽儲(chu)能系統中應優先選取立(li)式安(an)裝(zhuang)布(bu)置(zhi)(zhi)(zhi)形式。
使用(yong)Flow Simulation對某熔鹽儲能系(xi)統中(zhong)熔鹽電加(jia)熱器的(de)臥、立(li)式(shi)布置(zhi)形式(shi)進行數據化(hua)運(yun)(yun)行分析(xi),探求(qiu)最優布置(zhi)形式(shi)。以(yi)熱動力模擬(ni)的(de)數據結果進行分析(xi),立(li)式(shi)布置(zhi)可(ke)以(yi)在節省占地面積(ji)的(de)同時(shi),有效提高電加(jia)熱的(de)加(jia)熱效果,降(jiang)低運(yun)(yun)行風險(xian),在對應運(yun)(yun)行模擬(ni)數據佐證的(de)情況下(xia),可(ke)以(yi)在設計(ji)(ji)初期降(jiang)低其設計(ji)(ji)及投資成本。
熔鹽儲能(neng)(neng)技(ji)術作為新(xin)興的清潔能(neng)(neng)源技(ji)術,具有(you)廣泛的應用前(qian)景,隨著熔鹽儲能(neng)(neng)系統不斷(duan)成熟(shu)和(he)優化完善,儲能(neng)(neng)效率(lv)和(he)換熱效率(lv)逐(zhu)步提高,熔鹽儲能(neng)(neng)系統將得(de)到廣泛普及。
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。