鋁管鋁套冷風機傳熱性能分析
發布(bu)時間：2022-7-8
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近年來有不少生(sheng)產(chan)廠家在生(sheng)產(chan)鋁管鋁套片冷(leng)風(feng)機，生(sheng)產(chan)這種(zhong)冷(leng)風(feng)機究竟有什么好處?本(ben)文主要(yao)想(xiang)從傳熱(re)效果的角度來分析探討。
一、鋁管鋁套(tao)冷風機傳熱效果理(li)論分(fen)析(xi)
不(bu)能(neng)簡(jian)單的(de)(de)認為由于冷風(feng)機鋁合(he)金材(cai)(cai)料的(de)(de)導(dao)熱(re)(re)(re)系(xi)(xi)數較(jiao)鋼材(cai)(cai)料大(da)(da)(da)，使金屬壁熱(re)(re)(re)阻(zu)力項(xiang)減小(xiao)而使傳(chuan)(chuan)(chuan)熱(re)(re)(re)系(xi)(xi)數增大(da)(da)(da)。其實這個因素是微(wei)不(bu)足道的(de)(de)。更重要(yao)的(de)(de)原因之(zhi)一是鋁合(he)金大(da)(da)(da)的(de)(de)導(dao)熱(re)(re)(re)系(xi)(xi)數大(da)(da)(da)大(da)(da)(da)了翅(chi)(chi)(chi)片(pian)效(xiao)(xiao)率(lv)，減小(xiao)了空氣側熱(re)(re)(re)交換的(de)(de)阻(zu)力，因此(ci)了傳(chuan)(chuan)(chuan)熱(re)(re)(re)效(xiao)(xiao)率(lv)使傳(chuan)(chuan)(chuan)熱(re)(re)(re)系(xi)(xi)數增大(da)(da)(da)。冷風(feng)機翅(chi)(chi)(chi)片(pian)效(xiao)(xiao)率(lv)η＝th(mL)/(mL)［1］，如(ru)(ru)果(guo)(guo)(mL)值大(da)(da)(da)時，當熱(re)(re)(re)量由翅(chi)(chi)(chi)片(pian)基(ji)部(bu)向端部(bu)傳(chuan)(chuan)(chuan)遞(di)時，翅(chi)(chi)(chi)片(pian)端部(bu)過余(yu)溫度(du)較(jiao)小(xiao)，這表(biao)明翅(chi)(chi)(chi)片(pian)表(biao)面平均溫度(du)較(jiao)低，翅(chi)(chi)(chi)片(pian)的(de)(de)效(xiao)(xiao)率(lv)也效(xiao)(xiao)低。反之(zhi)，如(ru)(ru)果(guo)(guo)(mL)值較(jiao)小(xiao)時，翅(chi)(chi)(chi)片(pian)效(xiao)(xiao)率(lv)較(jiao)高。因此(ci)，在(zai)一定翅(chi)(chi)(chi)片(pian)高度(du)(L)條件下，m值較(jiao)小(xiao)是有利的(de)(de)。選用(yong)導(dao)熱(re)(re)(re)系(xi)(xi)數大(da)(da)(da)的(de)(de)材(cai)(cai)料，正好能(neng)使m值減小(xiao)。所以選用(yong)鋁管(guan)鋁片(pian)較(jiao)之(zhi)鋼管(guan)鋼片(pian)更有利于冷風(feng)機傳(chuan)(chuan)(chuan)熱(re)(re)(re)效(xiao)(xiao)果(guo)(guo)使傳(chuan)(chuan)(chuan)熱(re)(re)(re)系(xi)(xi)數增大(da)(da)(da)。
例(li)如有下(xia)列翅(chi)(chi)片(pian)(pian)(pian)(pian)盤管(guan)(guan)(guan)結構(gou)的冷(leng)風機：管(guan)(guan)(guan)子(zi)(zi)Φ20×1.0，等邊三角(jiao)形叉排，管(guan)(guan)(guan)子(zi)(zi)間(jian)距60mm，管(guan)(guan)(guan)子(zi)(zi)排距52mm，采用(yong)整(zheng)體(ti)式平翅(chi)(chi)片(pian)(pian)(pian)(pian)，翅(chi)(chi)片(pian)(pian)(pian)(pian)厚0.23mm，翅(chi)(chi)片(pian)(pian)(pian)(pian)間(jian)距12mm。如果翅(chi)(chi)片(pian)(pian)(pian)(pian)管(guan)(guan)(guan)的材(cai)料采用(yong)鋼(gang)管(guan)(guan)(guan)鋼(gang)片(pian)(pian)(pian)(pian)或鋁(lv)(lv)管(guan)(guan)(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)，我們根(gen)據文獻［2］提供的方法(fa)作計算(suan)比較。假設："冷(leng)風機在(zai)無霜工況下(xia)運行；蒸發溫度(du)為(wei)-20℃；據某次實際測定，迎面風速為(wei)2.8m/s、進風溫度(du)-6℃、進風相對濕(shi)度(du)63%；計算(suan)可得制冷(leng)劑側放熱(re)系數為(wei)500W/(m２•K)［2］"。計算(suan)結果如下(xia)，翅(chi)(chi)片(pian)(pian)(pian)(pian)效率(lv)：鋼(gang)管(guan)(guan)(guan)鋼(gang)片(pian)(pian)(pian)(pian)為(wei)0.35；鋁(lv)(lv)管(guan)(guan)(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)為(wei)0.58。翅(chi)(chi)片(pian)(pian)(pian)(pian)管(guan)(guan)(guan)總(zong)效率(lv)：鋼(gang)管(guan)(guan)(guan)鋼(gang)片(pian)(pian)(pian)(pian)為(wei)0.43；鋁(lv)(lv)管(guan)(guan)(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)0.63。對傳(chuan)熱(re)系數的影響；在(zai)上述相同條件下(xia)，鋁(lv)(lv)管(guan)(guan)(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)冷(leng)風機的傳(chuan)熱(re)系數比鋼(gang)管(guan)(guan)(guan)鋼(gang)片(pian)(pian)(pian)(pian)的高出27.8%。
二(er)、冷風機傳熱性(xing)能結果(guo)
我(wo)們(men)可以從(cong)冷(leng)(leng)(leng)風(feng)(feng)機傳(chuan)熱系數k與單位面積冷(leng)(leng)(leng)風(feng)(feng)機熱負荷Q來進(jin)行分(fen)析，比較的(de)條(tiao)件是(shi)，冷(leng)(leng)(leng)風(feng)(feng)機基本上是(shi)在無霜條(tiao)件下(xia)運行。以某(mou)生(sheng)產廠家生(sheng)產的(de)結(jie)構(gou)相同，冷(leng)(leng)(leng)卻面積、配風(feng)(feng)量(liang)相似的(de)冷(leng)(leng)(leng)風(feng)(feng)機作(zuo)比較，通過低溫(wen)(wen)試驗室實(shi)際(ji)測試的(de)結(jie)果，冷(leng)(leng)(leng)風(feng)(feng)機的(de)傳(chuan)熱系數。蒸(zheng)發(fa)(fa)溫(wen)(wen)度(du)-10℃時(shi)，鋁(lv)管(guan)鋁(lv)片(pian)冷(leng)(leng)(leng)風(feng)(feng)機的(de)傳(chuan)熱系數比鋼管(guan)鋼片(pian)冷(leng)(leng)(leng)風(feng)(feng)機高出約20～35%，顯示了鋁(lv)管(guan)鋁(lv)片(pian)的(de)優(you)勢。但隨(sui)著蒸(zheng)發(fa)(fa)溫(wen)(wen)度(du)，這種優(you)勢趨(qu)小。在實(shi)際(ji)中(zhong)還發(fa)(fa)現，當翅片(pian)管(guan)結(jie)霜后(hou)，并未(wei)顯示這種優(you)勢。
但是，由(you)于生(sheng)(sheng)產(chan)(chan)工藝、制造(zao)水平及冷風(feng)機結構的(de)(de)差(cha)(cha)異，不同廠生(sheng)(sheng)產(chan)(chan)的(de)(de)冷風(feng)機，其(qi)傳(chuan)熱系(xi)數的(de)(de)差(cha)(cha)別也較大。
另(ling)一(yi)方(fang)面(mian)(mian)，從單(dan)位(wei)面(mian)(mian)積(ji)(ji)熱(re)負荷來看(kan)，對同(tong)一(yi)廠生(sheng)產(chan)的(de)結構類(lei)(lei)同(tong)、冷(leng)卻面(mian)(mian)積(ji)(ji)、配(pei)(pei)風(feng)量(liang)相似的(de)冷(leng)風(feng)機，通過低(di)(di)溫試驗(yan)室(shi)進行性(xing)能(neng)測定(ding)的(de)實際結果(guo)表明："鋁(lv)(lv)管(guan)鋁(lv)(lv)片(pian)冷(leng)風(feng)機的(de)Q值(zhi)(zhi)比(bi)鋼(gang)(gang)管(guan)鋼(gang)(gang)片(pian)冷(leng)風(feng)機的(de)Q值(zhi)(zhi)高(gao)(gao)出(chu)(chu)約(yue)40%左右"。但(dan)是，產(chan)品生(sheng)產(chan)質量(liang)水(shui)平(ping)較低(di)(di)廠家(jia)生(sheng)產(chan)的(de)鋁(lv)(lv)管(guan)鋁(lv)(lv)片(pian)冷(leng)風(feng)機Q值(zhi)(zhi)僅比(bi)鋼(gang)(gang)管(guan)鋼(gang)(gang)片(pian)冷(leng)風(feng)機Q值(zhi)(zhi)高(gao)(gao)出(chu)(chu)大約(yue)為14～27%。我(wo)們(men)從某生(sheng)產(chan)水(shui)平(ping)比(bi)較高(gao)(gao)的(de)廠提供的(de)產(chan)品樣本(ben)數據，對結構類(lei)(lei)同(tong)、冷(leng)卻面(mian)(mian)積(ji)(ji)、配(pei)(pei)風(feng)量(liang)相似的(de)冷(leng)風(feng)機產(chan)品作比(bi)較可(ke)以得(de)到："每平(ping)方(fang)米(mi)冷(leng)卻面(mian)(mian)積(ji)(ji)的(de)熱(re)負荷Q(kW/m2)，鋁(lv)(lv)管(guan)鋁(lv)(lv)片(pian)比(bi)鋼(gang)(gang)管(guan)鋼(gang)(gang)片(pian)的(de)值(zhi)(zhi)高(gao)(gao)出(chu)(chu)約(yue)18～43%"。這一(yi)數值(zhi)(zhi)與低(di)(di)溫試驗(yan)室(shi)實際測定(ding)結果(guo)相當吻合(he)。
結論：從傳(chuan)熱(re)(re)效果(guo)分析可(ke)見(jian)，用(yong)導熱(re)(re)系數大的(de)材料制作(zuo)冷(leng)風(feng)機的(de)翅片盤管，在相同結構參數條件下可(ke)以得(de)到較好的(de)傳(chuan)熱(re)(re)效果(guo)。
