高低溫試驗箱容積的選擇及變溫速率的選擇

高低溫試驗箱容積的選擇 
   將被(bei)(bei)(bei)(bei)試(shi)(shi)(shi)產(chan)(chan)品(pin)(pin)（元器件(jian)、組(zu)件(jian)、部件(jian)或整機）置入(ru)氣(qi)候(hou)環境箱(xiang)(xiang)進行試(shi)(shi)(shi)驗(yan)時，為(wei)了保(bao)證被(bei)(bei)(bei)(bei)試(shi)(shi)(shi)產(chan)(chan)品(pin)(pin)周圍氣(qi)氛能(neng)滿足試(shi)(shi)(shi)驗(yan)規(gui)(gui)范(fan)所規(gui)(gui)定(ding)(ding)的(de)環境試(shi)(shi)(shi)驗(yan)條件(jian)，氣(qi)候(hou)箱(xiang)(xiang)工(gong)作(zuo)尺寸與被(bei)(bei)(bei)(bei)試(shi)(shi)(shi)產(chan)(chan)品(pin)(pin)外(wai)廓(kuo)尺寸之(zhi)(zhi)間應遵循以下幾點(dian)規(gui)(gui)定(ding)(ding)： a） 被(bei)(bei)(bei)(bei)試(shi)(shi)(shi)產(chan)(chan)品(pin)(pin)的(de)體(ti)(ti)積(ji)（W×D×H）不(bu)得超過試(shi)(shi)(shi)驗(yan)箱(xiang)(xiang)有(you)效(xiao)工(gong)作(zuo)空間的(de)（20～35）％（推薦選用20％）。對于(yu)在試(shi)(shi)(shi)驗(yan)中發(fa)熱的(de)產(chan)(chan)品(pin)(pin)推薦選用不(bu)大于(yu)10％。 b） 被(bei)(bei)(bei)(bei)試(shi)(shi)(shi)產(chan)(chan)品(pin)(pin)的(de)迎風斷(duan)面積(ji)與該斷(duan)面上(shang)(shang)試(shi)(shi)(shi)驗(yan)箱(xiang)(xiang)工(gong)作(zuo)室總(zong)面積(ji)之(zhi)(zhi)比不(bu)大于(yu)（35～50）％（推薦選用35％）。 c） 被(bei)(bei)(bei)(bei)試(shi)(shi)(shi)產(chan)(chan)品(pin)(pin)外(wai)廓(kuo)表面距(ju)試(shi)(shi)(shi)驗(yan)箱(xiang)(xiang)壁的(de)距(ju)離至(zhi)少保(bao)持100～150mm，（推薦選用150mm）。 上(shang)(shang)述三(san)點(dian)規(gui)(gui)定(ding)(ding)實際上(shang)(shang)是(shi)相互依存和統一的(de)。以1立方米正方體(ti)(ti)箱(xiang)(xiang)子為(wei)例，面積(ji)比為(wei)1：(0.35～0.5）相當于(yu)體(ti)(ti)積(ji)之(zhi)(zhi)比為(wei)1：（0.207～0.354）。距(ju)箱(xiang)(xiang)壁100～150mm相當于(yu)體(ti)(ti)積(ji)之(zhi)(zhi)比為(wei)1：（0.343～0.512）。總(zong)括上(shang)(shang)述三(san)點(dian)規(gui)(gui)定(ding)(ding)，氣(qi)候(hou)環境試(shi)(shi)(shi)驗(yan)箱(xiang)(xiang)的(de)工(gong)作(zuo)腔容積(ji)至(zhi)少應是(shi)被(bei)(bei)(bei)(bei)試(shi)(shi)(shi)產(chan)(chan)品(pin)(pin)外(wai)廓(kuo)體(ti)(ti)積(ji)的(de)3～5倍(bei)。作(zuo)出這種規(gui)(gui)定(ding)(ding)的(de)理由有(you)以下幾點(dian)：
被試驗(yan)(yan)(yan)件(jian)(jian)置入箱體(ti)后擠占了流暢(chang)的(de)通道，通道變窄將導(dao)致氣(qi)流流速的(de)增加。加速氣(qi)流與被試驗(yan)(yan)(yan)件(jian)(jian)之間的(de)熱(re)交換。這與環境條(tiao)件(jian)(jian)的(de)再(zai)現不(bu)符，因(yin)為在有(you)關標準中對涉(she)及溫(wen)度(du)環境試驗(yan)(yan)(yan)都規定試驗(yan)(yan)(yan)箱內試驗(yan)(yan)(yan)樣(yang)件(jian)(jian)周圍(wei)的(de)空氣(qi)流速不(bu)應超過(guo)1.7m/s，以防(fang)止試驗(yan)(yan)(yan)樣(yang)件(jian)(jian)和(he)周圍(wei)氣(qi)氛產生不(bu)符合實際的(de)熱(re)傳導(dao)。在空載(zai)時試驗(yan)(yan)(yan)箱內平均(jun)風速為0.6～0.8m/s，不(bu)超過(guo)1m/s，滿足a)、
1、 兩點(dian)要求所(suo)規定的(de)空間及面積(ji)(ji)比時，流場的(de)風(feng)速可能增(zeng)大（50～100）％，平均最(zui)高風(feng)速為（1～1.7）m/s。滿足標準(zhun)規定的(de)要求。如(ru)果在試(shi)(shi)(shi)驗中不(bu)加限制地加大試(shi)(shi)(shi)驗件的(de)體積(ji)(ji)或迎風(feng)斷(duan)面積(ji)(ji)，則實際試(shi)(shi)(shi)驗時氣流風(feng)速將增(zeng)大到超出試(shi)(shi)(shi)驗標準(zhun)所(suo)規定的(de)最(zui)高風(feng)速，其試(shi)(shi)(shi)驗結果的(de)有效性將受到懷(huai)疑。
高低(di)溫試驗(yan)箱(xiang)變溫速率的(de)選擇 
    普通(tong)的(de)(de)(de)高低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)沒(mei)有降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)的(de)(de)(de)指標(biao)，從環(huan)境(jing)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)到(dao)標(biao)稱(cheng)的(de)(de)(de)最低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)的(de)(de)(de)時間一(yi)般(ban)為90～120min。高低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)交(jiao)變(bian)(bian)(bian)(bian)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)、高低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)交(jiao)變(bian)(bian)(bian)(bian)濕(shi)熱試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)都有變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)的(de)(de)(de)要求，其變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)一(yi)般(ban)要求1℃/min，在此速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)的(de)(de)(de)范(fan)圍(wei)內(nei)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)可(ke)調。而快(kuai)速(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)的(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)較快(kuai)，升(sheng)(sheng)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)、降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)可(ke)以(yi)達(da)(da)到(dao)3℃/min～15℃/min，在某(mou)(mou)些溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)段(duan)升(sheng)(sheng)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)、降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)甚至可(ke)以(yi)達(da)(da)到(dao)30℃/min以(yi)上。 各(ge)種(zhong)規(gui)格、速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)的(de)(de)(de)快(kuai)速(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)的(de)(de)(de)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)范(fan)圍(wei)一(yi)般(ban)都是(shi)(shi)相同(tong)的(de)(de)(de)，即－60～＋130℃，但(dan)考(kao)核降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)的(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)范(fan)圍(wei)卻不盡相同(tong)，根(gen)據試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)不同(tong)的(de)(de)(de)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)要求，快(kuai)速(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)范(fan)圍(wei)有的(de)(de)(de)是(shi)(shi)－55～＋80℃，而有的(de)(de)(de)是(shi)(shi)－40～＋80℃。 關于(yu)快(kuai)速(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)的(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)有兩種(zhong)提法，一(yi)種(zhong)是(shi)(shi)全(quan)程(cheng)(cheng)(cheng)平(ping)(ping)(ping)均(jun)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)，一(yi)種(zhong)是(shi)(shi)線形(xing)(xing)(xing)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)（實際(ji)上是(shi)(shi)每(mei)5 min平(ping)(ping)(ping)均(jun)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)）。全(quan)程(cheng)(cheng)(cheng)平(ping)(ping)(ping)均(jun)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)是(shi)(shi)指在試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)的(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)范(fan)圍(wei)內(nei)，最高溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)與(yu)最低(di)(di)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)之差值與(yu)時間之比。目前國外各(ge)環(huan)境(jing)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)設備(bei)生產(chan)廠家提供的(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)的(de)(de)(de)技術(shu)參(can)數都是(shi)(shi)指的(de)(de)(de)全(quan)程(cheng)(cheng)(cheng)平(ping)(ping)(ping)均(jun)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)。線形(xing)(xing)(xing)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)指在任意的(de)(de)(de)每(mei)5 min時間段(duan)內(nei)，能夠保證(zheng)的(de)(de)(de)變(bian)(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)。而實際(ji)上對于(yu)快(kuai)速(su)(su)(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)(du)變(bian)(bian)(bian)(bian)化(hua)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)來說(shuo)，保證(zheng)線形(xing)(xing)(xing)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)的(de)(de)(de)難(nan)度(du)(du)(du)(du)(du)(du)(du)最大、最關鍵的(de)(de)(de)一(yi)段(duan)是(shi)(shi)，在降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)段(duan)最后的(de)(de)(de)一(yi)個(ge)5 min的(de)(de)(de)時間段(duan)內(nei)，試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)可(ke)以(yi)達(da)(da)到(dao)的(de)(de)(de)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)率(lv)(lv)(lv)。從某(mou)(mou)種(zhong)角度(du)(du)(du)(du)(du)(du)(du)講，線形(xing)(xing)(xing)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)（每(mei)5 min平(ping)(ping)(ping)均(jun)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)）更科(ke)學。因此試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)設備(bei)最好具有全(quan)程(cheng)(cheng)(cheng)平(ping)(ping)(ping)均(jun)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)和線形(xing)(xing)(xing)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)（每(mei)5 min平(ping)(ping)(ping)均(jun)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)）這兩個(ge)參(can)數。一(yi)般(ban)來說(shuo)，線形(xing)(xing)(xing)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)（每(mei)5 min平(ping)(ping)(ping)均(jun)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)）是(shi)(shi)全(quan)程(cheng)(cheng)(cheng)平(ping)(ping)(ping)均(jun)升(sheng)(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)(wen)速(su)(su)(su)(su)(su)(su)度(du)(du)(du)(du)(du)(du)(du)的(de)(de)(de)1/2。