鋁管鋁套冷風機傳熱性能分析
發(fa)布(bu)時間：2022-7-8
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近年來有(you)不(bu)少生產廠家在生產鋁(lv)管(guan)鋁(lv)套片冷(leng)(leng)風機(ji)，生產這種冷(leng)(leng)風機(ji)究竟有(you)什么好處?本文主要想從傳熱效(xiao)果的角度來分析探(tan)討(tao)。
一、鋁管鋁套冷風機傳熱效果理論分析(xi)
不能簡單(dan)的(de)認為(wei)由于冷風(feng)(feng)機鋁(lv)合(he)金材料的(de)導(dao)(dao)熱(re)(re)系(xi)數(shu)(shu)較(jiao)(jiao)(jiao)(jiao)(jiao)鋼材料大(da)，使金屬壁熱(re)(re)阻(zu)力項減(jian)(jian)小而使傳(chuan)(chuan)(chuan)熱(re)(re)系(xi)數(shu)(shu)增大(da)。其(qi)實(shi)這個(ge)因(yin)素是微不足道的(de)。更重要(yao)的(de)原因(yin)之(zhi)一(yi)是鋁(lv)合(he)金大(da)的(de)導(dao)(dao)熱(re)(re)系(xi)數(shu)(shu)大(da)大(da)了(le)(le)翅(chi)片(pian)效(xiao)(xiao)率，減(jian)(jian)小了(le)(le)空氣側熱(re)(re)交換的(de)阻(zu)力，因(yin)此了(le)(le)傳(chuan)(chuan)(chuan)熱(re)(re)效(xiao)(xiao)率使傳(chuan)(chuan)(chuan)熱(re)(re)系(xi)數(shu)(shu)增大(da)。冷風(feng)(feng)機翅(chi)片(pian)效(xiao)(xiao)率η＝th(mL)/(mL)［1］，如果(mL)值(zhi)(zhi)大(da)時，當熱(re)(re)量由翅(chi)片(pian)基部(bu)向端(duan)部(bu)傳(chuan)(chuan)(chuan)遞時，翅(chi)片(pian)端(duan)部(bu)過余溫(wen)度較(jiao)(jiao)(jiao)(jiao)(jiao)小，這表(biao)明翅(chi)片(pian)表(biao)面平均溫(wen)度較(jiao)(jiao)(jiao)(jiao)(jiao)低，翅(chi)片(pian)的(de)效(xiao)(xiao)率也效(xiao)(xiao)低。反之(zhi)，如果(mL)值(zhi)(zhi)較(jiao)(jiao)(jiao)(jiao)(jiao)小時，翅(chi)片(pian)效(xiao)(xiao)率較(jiao)(jiao)(jiao)(jiao)(jiao)高。因(yin)此，在一(yi)定(ding)翅(chi)片(pian)高度(L)條件下，m值(zhi)(zhi)較(jiao)(jiao)(jiao)(jiao)(jiao)小是有利(li)的(de)。選用導(dao)(dao)熱(re)(re)系(xi)數(shu)(shu)大(da)的(de)材料，正好能使m值(zhi)(zhi)減(jian)(jian)小。所以選用鋁(lv)管鋁(lv)片(pian)較(jiao)(jiao)(jiao)(jiao)(jiao)之(zhi)鋼管鋼片(pian)更有利(li)于冷風(feng)(feng)機傳(chuan)(chuan)(chuan)熱(re)(re)效(xiao)(xiao)果使傳(chuan)(chuan)(chuan)熱(re)(re)系(xi)數(shu)(shu)增大(da)。
例如(ru)有(you)下列翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)(pian)盤管(guan)結構的(de)(de)冷(leng)風(feng)(feng)(feng)(feng)機：管(guan)子Φ20×1.0，等邊三角(jiao)形(xing)叉排，管(guan)子間距60mm，管(guan)子排距52mm，采用(yong)(yong)整體式平(ping)翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)(pian)，翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)(pian)厚0.23mm，翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)(pian)間距12mm。如(ru)果翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)(pian)管(guan)的(de)(de)材料采用(yong)(yong)鋼(gang)管(guan)鋼(gang)片(pian)(pian)(pian)(pian)(pian)(pian)或鋁(lv)(lv)管(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)(pian)(pian)，我們根據(ju)文(wen)獻［2］提供的(de)(de)方(fang)法作計(ji)算(suan)比(bi)(bi)較(jiao)。假設："冷(leng)風(feng)(feng)(feng)(feng)機在(zai)無霜(shuang)工(gong)況下運(yun)行；蒸發溫(wen)度(du)為(wei)-20℃；據(ju)某次實際(ji)測定(ding)，迎面風(feng)(feng)(feng)(feng)速(su)為(wei)2.8m/s、進風(feng)(feng)(feng)(feng)溫(wen)度(du)-6℃、進風(feng)(feng)(feng)(feng)相對濕(shi)度(du)63%；計(ji)算(suan)可(ke)得制冷(leng)劑(ji)側放熱系數為(wei)500W/(m２•K)［2］"。計(ji)算(suan)結果如(ru)下，翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)(pian)效率(lv)：鋼(gang)管(guan)鋼(gang)片(pian)(pian)(pian)(pian)(pian)(pian)為(wei)0.35；鋁(lv)(lv)管(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)(pian)(pian)為(wei)0.58。翅(chi)(chi)片(pian)(pian)(pian)(pian)(pian)(pian)管(guan)總效率(lv)：鋼(gang)管(guan)鋼(gang)片(pian)(pian)(pian)(pian)(pian)(pian)為(wei)0.43；鋁(lv)(lv)管(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)(pian)(pian)0.63。對傳(chuan)熱系數的(de)(de)影響(xiang)；在(zai)上述相同條件下，鋁(lv)(lv)管(guan)鋁(lv)(lv)片(pian)(pian)(pian)(pian)(pian)(pian)冷(leng)風(feng)(feng)(feng)(feng)機的(de)(de)傳(chuan)熱系數比(bi)(bi)鋼(gang)管(guan)鋼(gang)片(pian)(pian)(pian)(pian)(pian)(pian)的(de)(de)高出27.8%。
二、冷風機傳(chuan)熱性能結果(guo)
我們(men)可以從冷(leng)風(feng)機(ji)(ji)(ji)傳熱(re)系數k與單位面(mian)積冷(leng)風(feng)機(ji)(ji)(ji)熱(re)負荷(he)Q來進(jin)行分析，比較的(de)條件是(shi)，冷(leng)風(feng)機(ji)(ji)(ji)基本上(shang)是(shi)在無霜(shuang)條件下運行。以某生產(chan)廠家生產(chan)的(de)結構相同，冷(leng)卻面(mian)積、配風(feng)量相似(si)的(de)冷(leng)風(feng)機(ji)(ji)(ji)作比較，通過低溫(wen)試(shi)(shi)驗室實際測試(shi)(shi)的(de)結果，冷(leng)風(feng)機(ji)(ji)(ji)的(de)傳熱(re)系數。蒸發(fa)(fa)溫(wen)度(du)-10℃時，鋁管鋁片冷(leng)風(feng)機(ji)(ji)(ji)的(de)傳熱(re)系數比鋼管鋼片冷(leng)風(feng)機(ji)(ji)(ji)高出約20～35%，顯(xian)(xian)示了鋁管鋁片的(de)優勢(shi)。但隨著蒸發(fa)(fa)溫(wen)度(du)，這(zhe)種優勢(shi)趨小。在實際中還發(fa)(fa)現，當翅片管結霜(shuang)后，并未顯(xian)(xian)示這(zhe)種優勢(shi)。
但是，由(you)于生(sheng)產工(gong)藝、制造水平及冷風(feng)機結構的(de)差異(yi)，不(bu)同廠(chang)生(sheng)產的(de)冷風(feng)機，其傳熱(re)系數的(de)差別也較大。
另一(yi)方面，從(cong)單(dan)位面積(ji)(ji)熱(re)(re)負荷來看，對同(tong)一(yi)廠生(sheng)產(chan)的(de)(de)(de)結(jie)構類(lei)同(tong)、冷(leng)(leng)卻面積(ji)(ji)、配風量(liang)相似的(de)(de)(de)冷(leng)(leng)風機(ji)，通過低溫(wen)試驗室進行性(xing)能測定的(de)(de)(de)實際結(jie)果表明："鋁(lv)(lv)管(guan)(guan)鋁(lv)(lv)片冷(leng)(leng)風機(ji)的(de)(de)(de)Q值(zhi)(zhi)(zhi)比(bi)鋼(gang)管(guan)(guan)鋼(gang)片冷(leng)(leng)風機(ji)的(de)(de)(de)Q值(zhi)(zhi)(zhi)高出約40%左(zuo)右"。但是，產(chan)品生(sheng)產(chan)質量(liang)水平(ping)較(jiao)低廠家生(sheng)產(chan)的(de)(de)(de)鋁(lv)(lv)管(guan)(guan)鋁(lv)(lv)片冷(leng)(leng)風機(ji)Q值(zhi)(zhi)(zhi)僅(jin)比(bi)鋼(gang)管(guan)(guan)鋼(gang)片冷(leng)(leng)風機(ji)Q值(zhi)(zhi)(zhi)高出大約為14～27%。我們從(cong)某生(sheng)產(chan)水平(ping)比(bi)較(jiao)高的(de)(de)(de)廠提供的(de)(de)(de)產(chan)品樣本數(shu)據，對結(jie)構類(lei)同(tong)、冷(leng)(leng)卻面積(ji)(ji)、配風量(liang)相似的(de)(de)(de)冷(leng)(leng)風機(ji)產(chan)品作比(bi)較(jiao)可以(yi)得到(dao)："每平(ping)方米冷(leng)(leng)卻面積(ji)(ji)的(de)(de)(de)熱(re)(re)負荷Q(kW/m2)，鋁(lv)(lv)管(guan)(guan)鋁(lv)(lv)片比(bi)鋼(gang)管(guan)(guan)鋼(gang)片的(de)(de)(de)值(zhi)(zhi)(zhi)高出約18～43%"。這(zhe)一(yi)數(shu)值(zhi)(zhi)(zhi)與低溫(wen)試驗室實際測定結(jie)果相當(dang)吻合。
結(jie)論：從傳(chuan)熱效果(guo)分析可(ke)見，用導(dao)熱系(xi)數大的材(cai)料制作冷風機的翅片盤管，在相同結(jie)構參數條(tiao)件下可(ke)以(yi)得到較(jiao)好的傳(chuan)熱效果(guo)。
