鋁管鋁套冷風機傳熱性能分析
發布時間：2022-7-8
瀏(liu)覽量710
近年(nian)來(lai)有不少生(sheng)產(chan)廠家在生(sheng)產(chan)鋁管鋁套片冷風(feng)機(ji)，生(sheng)產(chan)這種冷風(feng)機(ji)究竟有什么好處?本文主要想從傳(chuan)熱效(xiao)果的角度(du)來(lai)分析探討(tao)。
一、鋁管(guan)鋁套冷(leng)風機傳熱效果(guo)理論分(fen)析(xi)
不能簡單的(de)認為由于(yu)冷風(feng)(feng)機(ji)(ji)鋁合(he)金(jin)材(cai)料的(de)導(dao)(dao)熱(re)系數較(jiao)鋼(gang)材(cai)料大(da)(da)，使(shi)(shi)金(jin)屬(shu)壁(bi)熱(re)阻力項減小(xiao)而使(shi)(shi)傳(chuan)熱(re)系數增大(da)(da)。其實這個因素是(shi)(shi)微不足道的(de)。更(geng)重要的(de)原因之一是(shi)(shi)鋁合(he)金(jin)大(da)(da)的(de)導(dao)(dao)熱(re)系數大(da)(da)大(da)(da)了(le)翅(chi)片(pian)效(xiao)(xiao)率(lv)(lv)，減小(xiao)了(le)空氣側(ce)熱(re)交換(huan)的(de)阻力，因此了(le)傳(chuan)熱(re)效(xiao)(xiao)率(lv)(lv)使(shi)(shi)傳(chuan)熱(re)系數增大(da)(da)。冷風(feng)(feng)機(ji)(ji)翅(chi)片(pian)效(xiao)(xiao)率(lv)(lv)η＝th(mL)/(mL)［1］，如果(mL)值(zhi)(zhi)大(da)(da)時，當(dang)熱(re)量由翅(chi)片(pian)基(ji)部(bu)向端部(bu)傳(chuan)遞(di)時，翅(chi)片(pian)端部(bu)過余溫(wen)度(du)較(jiao)小(xiao)，這表明翅(chi)片(pian)表面平均溫(wen)度(du)較(jiao)低(di)，翅(chi)片(pian)的(de)效(xiao)(xiao)率(lv)(lv)也效(xiao)(xiao)低(di)。反之，如果(mL)值(zhi)(zhi)較(jiao)小(xiao)時，翅(chi)片(pian)效(xiao)(xiao)率(lv)(lv)較(jiao)高。因此，在一定(ding)翅(chi)片(pian)高度(du)(L)條件下，m值(zhi)(zhi)較(jiao)小(xiao)是(shi)(shi)有利的(de)。選用(yong)導(dao)(dao)熱(re)系數大(da)(da)的(de)材(cai)料，正(zheng)好能使(shi)(shi)m值(zhi)(zhi)減小(xiao)。所以(yi)選用(yong)鋁管鋁片(pian)較(jiao)之鋼(gang)管鋼(gang)片(pian)更(geng)有利于(yu)冷風(feng)(feng)機(ji)(ji)傳(chuan)熱(re)效(xiao)(xiao)果使(shi)(shi)傳(chuan)熱(re)系數增大(da)(da)。
例如(ru)(ru)有下(xia)列翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)盤管(guan)(guan)結構(gou)的(de)(de)(de)(de)冷(leng)風(feng)機(ji)(ji)：管(guan)(guan)子(zi)Φ20×1.0，等邊三(san)角形(xing)叉(cha)排，管(guan)(guan)子(zi)間距60mm，管(guan)(guan)子(zi)排距52mm，采用整體式平翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)，翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)厚(hou)0.23mm，翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)間距12mm。如(ru)(ru)果翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)管(guan)(guan)的(de)(de)(de)(de)材料(liao)采用鋼(gang)(gang)(gang)(gang)管(guan)(guan)鋼(gang)(gang)(gang)(gang)片(pian)(pian)(pian)(pian)(pian)或鋁(lv)管(guan)(guan)鋁(lv)片(pian)(pian)(pian)(pian)(pian)，我們根據文獻［2］提(ti)供的(de)(de)(de)(de)方(fang)法作計算(suan)比較。假設："冷(leng)風(feng)機(ji)(ji)在無霜工況下(xia)運行；蒸發(fa)溫度為(wei)-20℃；據某次(ci)實際測定，迎面風(feng)速為(wei)2.8m/s、進(jin)(jin)風(feng)溫度-6℃、進(jin)(jin)風(feng)相對(dui)濕(shi)度63%；計算(suan)可得制(zhi)冷(leng)劑側放(fang)熱(re)(re)系(xi)數為(wei)500W/(m２•K)［2］"。計算(suan)結果如(ru)(ru)下(xia)，翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)效率：鋼(gang)(gang)(gang)(gang)管(guan)(guan)鋼(gang)(gang)(gang)(gang)片(pian)(pian)(pian)(pian)(pian)為(wei)0.35；鋁(lv)管(guan)(guan)鋁(lv)片(pian)(pian)(pian)(pian)(pian)為(wei)0.58。翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)管(guan)(guan)總效率：鋼(gang)(gang)(gang)(gang)管(guan)(guan)鋼(gang)(gang)(gang)(gang)片(pian)(pian)(pian)(pian)(pian)為(wei)0.43；鋁(lv)管(guan)(guan)鋁(lv)片(pian)(pian)(pian)(pian)(pian)0.63。對(dui)傳熱(re)(re)系(xi)數的(de)(de)(de)(de)影響；在上述相同(tong)條件下(xia)，鋁(lv)管(guan)(guan)鋁(lv)片(pian)(pian)(pian)(pian)(pian)冷(leng)風(feng)機(ji)(ji)的(de)(de)(de)(de)傳熱(re)(re)系(xi)數比鋼(gang)(gang)(gang)(gang)管(guan)(guan)鋼(gang)(gang)(gang)(gang)片(pian)(pian)(pian)(pian)(pian)的(de)(de)(de)(de)高(gao)出27.8%。
二、冷風機傳熱性能結果
我(wo)們(men)可以(yi)從冷(leng)(leng)風(feng)機(ji)(ji)傳熱(re)系(xi)數k與(yu)單位(wei)面積(ji)冷(leng)(leng)風(feng)機(ji)(ji)熱(re)負荷Q來(lai)進行分析，比(bi)較的(de)條(tiao)件是(shi)，冷(leng)(leng)風(feng)機(ji)(ji)基本上是(shi)在(zai)無霜條(tiao)件下運行。以(yi)某(mou)生(sheng)產廠家(jia)生(sheng)產的(de)結(jie)構相(xiang)(xiang)同，冷(leng)(leng)卻面積(ji)、配風(feng)量相(xiang)(xiang)似(si)的(de)冷(leng)(leng)風(feng)機(ji)(ji)作比(bi)較，通(tong)過低溫試(shi)驗(yan)室實際測(ce)試(shi)的(de)結(jie)果(guo)，冷(leng)(leng)風(feng)機(ji)(ji)的(de)傳熱(re)系(xi)數。蒸(zheng)發(fa)溫度(du)-10℃時(shi)，鋁(lv)(lv)管(guan)(guan)(guan)鋁(lv)(lv)片冷(leng)(leng)風(feng)機(ji)(ji)的(de)傳熱(re)系(xi)數比(bi)鋼管(guan)(guan)(guan)鋼片冷(leng)(leng)風(feng)機(ji)(ji)高(gao)出約(yue)20～35%，顯示(shi)了鋁(lv)(lv)管(guan)(guan)(guan)鋁(lv)(lv)片的(de)優勢(shi)。但(dan)隨著蒸(zheng)發(fa)溫度(du)，這種優勢(shi)趨小(xiao)。在(zai)實際中(zhong)還發(fa)現(xian)，當翅(chi)片管(guan)(guan)(guan)結(jie)霜后(hou)，并未顯示(shi)這種優勢(shi)。
但是，由于生產工藝、制造水平及(ji)冷風機(ji)結構的差(cha)異(yi)，不(bu)同廠生產的冷風機(ji)，其傳熱(re)系(xi)數的差(cha)別(bie)也較大。
另一方面(mian)，從(cong)單位面(mian)積熱負荷來看(kan)，對同(tong)一廠生(sheng)產(chan)(chan)(chan)的結構(gou)類(lei)同(tong)、冷(leng)(leng)(leng)卻(que)面(mian)積、配風(feng)量相(xiang)似的冷(leng)(leng)(leng)風(feng)機(ji)，通過低(di)溫試驗室進行性(xing)能(neng)測(ce)定的實際(ji)結果表明："鋁(lv)(lv)管(guan)鋁(lv)(lv)片冷(leng)(leng)(leng)風(feng)機(ji)的Q值(zhi)(zhi)比鋼管(guan)鋼片冷(leng)(leng)(leng)風(feng)機(ji)的Q值(zhi)(zhi)高(gao)出(chu)約(yue)40%左右(you)"。但是，產(chan)(chan)(chan)品(pin)生(sheng)產(chan)(chan)(chan)質量水平(ping)較(jiao)低(di)廠家(jia)生(sheng)產(chan)(chan)(chan)的鋁(lv)(lv)管(guan)鋁(lv)(lv)片冷(leng)(leng)(leng)風(feng)機(ji)Q值(zhi)(zhi)僅比鋼管(guan)鋼片冷(leng)(leng)(leng)風(feng)機(ji)Q值(zhi)(zhi)高(gao)出(chu)大約(yue)為14～27%。我們從(cong)某生(sheng)產(chan)(chan)(chan)水平(ping)比較(jiao)高(gao)的廠提供的產(chan)(chan)(chan)品(pin)樣本數(shu)據，對結構(gou)類(lei)同(tong)、冷(leng)(leng)(leng)卻(que)面(mian)積、配風(feng)量相(xiang)似的冷(leng)(leng)(leng)風(feng)機(ji)產(chan)(chan)(chan)品(pin)作比較(jiao)可以得(de)到："每平(ping)方米(mi)冷(leng)(leng)(leng)卻(que)面(mian)積的熱負荷Q(kW/m2)，鋁(lv)(lv)管(guan)鋁(lv)(lv)片比鋼管(guan)鋼片的值(zhi)(zhi)高(gao)出(chu)約(yue)18～43%"。這一數(shu)值(zhi)(zhi)與低(di)溫試驗室實際(ji)測(ce)定結果相(xiang)當吻合。
結論：從傳(chuan)熱(re)效果(guo)分析可見(jian)，用(yong)導熱(re)系數大的(de)(de)材料制(zhi)作冷風機(ji)的(de)(de)翅片(pian)盤管，在(zai)相同結構參數條(tiao)件下可以得(de)到較好(hao)的(de)(de)傳(chuan)熱(re)效果(guo)。
