高低溫試驗箱容積的選擇及變溫速率的選擇

高(gao)低溫試驗箱(xiang)容積的選擇(ze) 
   將(jiang)被(bei)(bei)(bei)試(shi)產(chan)(chan)品(pin)（元器(qi)件(jian)、組件(jian)、部件(jian)或整機）置(zhi)入氣候環(huan)(huan)境(jing)箱進行試(shi)驗(yan)時(shi)，為了保(bao)證被(bei)(bei)(bei)試(shi)產(chan)(chan)品(pin)周圍氣氛(fen)能滿足試(shi)驗(yan)規(gui)(gui)范所規(gui)(gui)定(ding)的(de)(de)環(huan)(huan)境(jing)試(shi)驗(yan)條件(jian)，氣候箱工作(zuo)尺寸(cun)與被(bei)(bei)(bei)試(shi)產(chan)(chan)品(pin)外(wai)(wai)廓尺寸(cun)之間(jian)應遵循以下幾點規(gui)(gui)定(ding)： a） 被(bei)(bei)(bei)試(shi)產(chan)(chan)品(pin)的(de)(de)體(ti)積(ji)（W×D×H）不得超過試(shi)驗(yan)箱有效工作(zuo)空間(jian)的(de)(de)（20～35）％（推(tui)薦(jian)選用20％）。對于(yu)在試(shi)驗(yan)中(zhong)發熱的(de)(de)產(chan)(chan)品(pin)推(tui)薦(jian)選用不大于(yu)10％。 b） 被(bei)(bei)(bei)試(shi)產(chan)(chan)品(pin)的(de)(de)迎風(feng)斷面(mian)積(ji)與該斷面(mian)上試(shi)驗(yan)箱工作(zuo)室總面(mian)積(ji)之比(bi)不大于(yu)（35～50）％（推(tui)薦(jian)選用35％）。 c） 被(bei)(bei)(bei)試(shi)產(chan)(chan)品(pin)外(wai)(wai)廓表面(mian)距(ju)(ju)試(shi)驗(yan)箱壁的(de)(de)距(ju)(ju)離至少保(bao)持100～150mm，（推(tui)薦(jian)選用150mm）。 上述三點規(gui)(gui)定(ding)實際上是相(xiang)互依存和統(tong)一的(de)(de)。以1立方(fang)米(mi)正(zheng)方(fang)體(ti)箱子為例，面(mian)積(ji)比(bi)為1：(0.35～0.5）相(xiang)當于(yu)體(ti)積(ji)之比(bi)為1：（0.207～0.354）。距(ju)(ju)箱壁100～150mm相(xiang)當于(yu)體(ti)積(ji)之比(bi)為1：（0.343～0.512）。總括上述三點規(gui)(gui)定(ding)，氣候環(huan)(huan)境(jing)試(shi)驗(yan)箱的(de)(de)工作(zuo)腔容(rong)積(ji)至少應是被(bei)(bei)(bei)試(shi)產(chan)(chan)品(pin)外(wai)(wai)廓體(ti)積(ji)的(de)(de)3～5倍。作(zuo)出這種規(gui)(gui)定(ding)的(de)(de)理(li)由有以下幾點：
被(bei)試(shi)驗(yan)件(jian)置入箱(xiang)體后擠占了流(liu)暢的(de)通(tong)道，通(tong)道變(bian)窄將導致氣(qi)流(liu)流(liu)速(su)的(de)增加。加速(su)氣(qi)流(liu)與被(bei)試(shi)驗(yan)件(jian)之間的(de)熱交換。這與環(huan)境條(tiao)件(jian)的(de)再現不符，因為在有關標準(zhun)中對涉及溫度環(huan)境試(shi)驗(yan)都規定(ding)試(shi)驗(yan)箱(xiang)內試(shi)驗(yan)樣(yang)件(jian)周圍的(de)空(kong)氣(qi)流(liu)速(su)不應超(chao)過1.7m/s，以防止(zhi)試(shi)驗(yan)樣(yang)件(jian)和周圍氣(qi)氛產(chan)生不符合實際的(de)熱傳導。在空(kong)載時(shi)試(shi)驗(yan)箱(xiang)內平均風(feng)速(su)為0.6～0.8m/s，不超(chao)過1m/s，滿(man)足a)、
1、 兩點要(yao)求所規(gui)定(ding)的空間及面(mian)積(ji)比時(shi)，流場的風(feng)(feng)(feng)速可(ke)能增(zeng)大（50～100）％，平均最(zui)高(gao)風(feng)(feng)(feng)速為（1～1.7）m/s。滿足(zu)標準(zhun)(zhun)規(gui)定(ding)的要(yao)求。如果在試驗中(zhong)不加限制(zhi)地加大試驗件(jian)的體積(ji)或迎風(feng)(feng)(feng)斷面(mian)積(ji)，則(ze)實際試驗時(shi)氣流風(feng)(feng)(feng)速將增(zeng)大到超出(chu)試驗標準(zhun)(zhun)所規(gui)定(ding)的最(zui)高(gao)風(feng)(feng)(feng)速，其試驗結果的有效(xiao)性將受到懷疑(yi)。
高低溫試驗箱變溫速率的選(xuan)擇 
    普通的(de)(de)(de)(de)(de)(de)高低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)沒有降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)指(zhi)標，從環境溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)到(dao)標稱的(de)(de)(de)(de)(de)(de)最(zui)(zui)低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)時(shi)(shi)間一(yi)(yi)般為90～120min。高低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)交(jiao)變(bian)(bian)(bian)(bian)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)、高低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)交(jiao)變(bian)(bian)(bian)(bian)濕(shi)熱試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)都(dou)有變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)要(yao)(yao)求，其變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)一(yi)(yi)般要(yao)(yao)求1℃/min，在(zai)(zai)此速(su)(su)(su)(su)(su)(su)(su)率(lv)的(de)(de)(de)(de)(de)(de)范(fan)(fan)圍(wei)(wei)內速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)可(ke)(ke)調。而快(kuai)速(su)(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)的(de)(de)(de)(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)較快(kuai)，升溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)、降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)可(ke)(ke)以達(da)到(dao)3℃/min～15℃/min，在(zai)(zai)某(mou)些溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)段(duan)(duan)(duan)升溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)、降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)甚(shen)至(zhi)可(ke)(ke)以達(da)到(dao)30℃/min以上。 各種(zhong)(zhong)規格、速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)快(kuai)速(su)(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)的(de)(de)(de)(de)(de)(de)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)范(fan)(fan)圍(wei)(wei)一(yi)(yi)般都(dou)是(shi)(shi)相(xiang)同的(de)(de)(de)(de)(de)(de)，即－60～＋130℃，但考核降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)范(fan)(fan)圍(wei)(wei)卻不(bu)盡相(xiang)同，根據試(shi)(shi)驗(yan)(yan)(yan)(yan)不(bu)同的(de)(de)(de)(de)(de)(de)試(shi)(shi)驗(yan)(yan)(yan)(yan)要(yao)(yao)求，快(kuai)速(su)(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)范(fan)(fan)圍(wei)(wei)有的(de)(de)(de)(de)(de)(de)是(shi)(shi)－55～＋80℃，而有的(de)(de)(de)(de)(de)(de)是(shi)(shi)－40～＋80℃。 關于快(kuai)速(su)(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)的(de)(de)(de)(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)有兩種(zhong)(zhong)提(ti)法，一(yi)(yi)種(zhong)(zhong)是(shi)(shi)全程(cheng)(cheng)平均(jun)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)，一(yi)(yi)種(zhong)(zhong)是(shi)(shi)線(xian)形(xing)(xing)(xing)(xing)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)（實(shi)際(ji)(ji)上是(shi)(shi)每(mei)5 min平均(jun)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)）。全程(cheng)(cheng)平均(jun)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)是(shi)(shi)指(zhi)在(zai)(zai)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)的(de)(de)(de)(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)范(fan)(fan)圍(wei)(wei)內，最(zui)(zui)高溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)與最(zui)(zui)低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)之(zhi)差值與時(shi)(shi)間之(zhi)比。目(mu)前國外各環境試(shi)(shi)驗(yan)(yan)(yan)(yan)設備(bei)生產廠家提(ti)供的(de)(de)(de)(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)的(de)(de)(de)(de)(de)(de)技術參數都(dou)是(shi)(shi)指(zhi)的(de)(de)(de)(de)(de)(de)全程(cheng)(cheng)平均(jun)速(su)(su)(su)(su)(su)(su)(su)率(lv)。線(xian)形(xing)(xing)(xing)(xing)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)指(zhi)在(zai)(zai)任意的(de)(de)(de)(de)(de)(de)每(mei)5 min時(shi)(shi)間段(duan)(duan)(duan)內，能夠保(bao)(bao)證的(de)(de)(de)(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)。而實(shi)際(ji)(ji)上對于快(kuai)速(su)(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)來說，保(bao)(bao)證線(xian)形(xing)(xing)(xing)(xing)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)難度(du)(du)(du)(du)(du)(du)最(zui)(zui)大、最(zui)(zui)關鍵的(de)(de)(de)(de)(de)(de)一(yi)(yi)段(duan)(duan)(duan)是(shi)(shi)，在(zai)(zai)降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)段(duan)(duan)(duan)最(zui)(zui)后的(de)(de)(de)(de)(de)(de)一(yi)(yi)個5 min的(de)(de)(de)(de)(de)(de)時(shi)(shi)間段(duan)(duan)(duan)內，試(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)可(ke)(ke)以達(da)到(dao)的(de)(de)(de)(de)(de)(de)降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)率(lv)。從某(mou)種(zhong)(zhong)角度(du)(du)(du)(du)(du)(du)講，線(xian)形(xing)(xing)(xing)(xing)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)（每(mei)5 min平均(jun)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)）更科學(xue)。因此試(shi)(shi)驗(yan)(yan)(yan)(yan)設備(bei)最(zui)(zui)好具有全程(cheng)(cheng)平均(jun)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)和線(xian)形(xing)(xing)(xing)(xing)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)（每(mei)5 min平均(jun)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)）這兩個參數。一(yi)(yi)般來說，線(xian)形(xing)(xing)(xing)(xing)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)（每(mei)5 min平均(jun)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)）是(shi)(shi)全程(cheng)(cheng)平均(jun)升降(jiang)(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)1/2。