恒溫恒濕試驗箱中(zhong)單級制(zhi)冷(leng)循環(huan)(huan)基本上采用(yong)的(de)中(zhong)溫制(zhi)冷(leng)劑(ji)是(shi)(shi)R404A，在(zai)一(yi)個大(da)氣(qi)壓(ya)下(xia)其蒸(zheng)發溫度(du)(du)是(shi)(shi)-46.5℃(R22/-40.7℃)，但(dan)空氣(qi)冷(leng)卻式冷(leng)凝器(qi)傳(chuan)熱溫差(cha)通常取10℃左右(you)(在(zai)強制(zhi)送風(feng)散熱循環(huan)(huan)下(xia)，蒸(zheng)發器(qi)和內箱(xiang)的(de)溫差(cha))，就是(shi)(shi)說箱(xiang)內只能制(zhi)取-36.5℃的(de)低(di)(di)溫，當然，通過調低(di)(di)壓(ya)縮機的(de)蒸(zheng)發壓(ya)力，可以(yi)(yi)將R404A制(zhi)冷(leng)劑(ji)的(de)最低(di)(di)蒸(zheng)發溫度(du)(du)降低(di)(di)到-50℃;所以(yi)(yi)要獲取-50℃及以(yi)(yi)下(xia)的(de)低(di)(di)溫時必須采用(yong)中(zhong)溫制(zhi)冷(leng)劑(ji)與低(di)(di)溫制(zhi)冷(leng)劑(ji)復疊式的(de)制(zhi)冷(leng)循環(huan)(huan)，制(zhi)取-50℃～-80℃的(de)低(di)(di)溫，低(di)(di)溫制(zhi)冷(leng)劑(ji)一(yi)般選(xuan)用(yong)R23它在(zai)一(yi)個大(da)氣(qi)壓(ya)下(xia)的(de)蒸(zheng)發溫度(du)(du)是(shi)(shi)-81.7℃.
恒(heng)溫(wen)恒(heng)濕試(shi)驗箱單(dan)級蒸(zheng)氣(qi)(qi)壓(ya)(ya)(ya)(ya)縮(suo)式制(zhi)(zhi)冷(leng)(leng)機(ji)的(de)(de)最低蒸(zheng)發(fa)(fa)溫(wen)度(du),主要取決于(yu)它的(de)(de)冷(leng)(leng)凝壓(ya)(ya)(ya)(ya)力(li)及壓(ya)(ya)(ya)(ya)縮(suo)比(bi),制(zhi)(zhi)冷(leng)(leng)劑的(de)(de)冷(leng)(leng)凝壓(ya)(ya)(ya)(ya)力(li)由(you)制(zhi)(zhi)冷(leng)(leng)劑的(de)(de)類(lei)別和(he)環境介質(如空氣(qi)(qi)或(huo)水)的(de)(de)溫(wen)度(du)決定(ding)(ding),在通(tong)常情況下(xia),它處于(yu)0.7~1.8Mpa范圍內,壓(ya)(ya)(ya)(ya)縮(suo)比(bi)與(yu)冷(leng)(leng)凝壓(ya)(ya)(ya)(ya)力(li)和(he)蒸(zheng)發(fa)(fa)壓(ya)(ya)(ya)(ya)力(li)有關,當冷(leng)(leng)凝壓(ya)(ya)(ya)(ya)力(li)一定(ding)(ding)時,隨(sui)著(zhu)蒸(zheng)發(fa)(fa)溫(wen)度(du)的(de)(de)降(jiang)低,蒸(zheng)發(fa)(fa)壓(ya)(ya)(ya)(ya)力(li)也相應下(xia)降(jiang),因(yin)而使壓(ya)(ya)(ya)(ya)縮(suo)比(bi)上升,它將引起壓(ya)(ya)(ya)(ya)縮(suo)機(ji)排氣(qi)(qi)溫(wen)度(du)的(de)(de)升高，潤(run)滑(hua)油(you)變稀,使潤(run)滑(hua)條件(jian)變壞,嚴(yan)重時甚至會(hui)出現結炭和(he)拉缸現象(xiang).另一方(fang)面,壓(ya)(ya)(ya)(ya)縮(suo)比(bi)的(de)(de)增大(da)將導(dao)致壓(ya)(ya)(ya)(ya)縮(suo)機(ji)的(de)(de)輸(shu)氣(qi)(qi)系數降(jiang)低,制(zhi)(zhi)冷(leng)(leng)量減少,實際壓(ya)(ya)(ya)(ya)縮(suo)過程偏離等熵過程越遠,壓(ya)(ya)(ya)(ya)縮(suo)機(ji)功耗增加,制(zhi)(zhi)冷(leng)(leng)系數下(xia)降(jiang),經濟性降(jiang)低.
恒(heng)溫(wen)恒(heng)濕試(shi)(shi)驗箱適(shi)用于儀(yi)器(qi)儀(yi)表材料,電工,電子(zi)(zi)產(chan)(chan)品,家(jia)用電器(qi),汽摩配(pei)件(jian)(jian)、化(hua)工涂(tu)料,各種(zhong)電子(zi)(zi)元器(qi)件(jian)(jian)及(ji)其他(ta)相關(guan)產(chan)(chan)品零部件(jian)(jian)在高溫(wen)、低溫(wen)、濕度的環(huan)(huan)境下(xia)貯存(cun),運輸,使(shi)用時的適(shi)應(ying)性(xing)試(shi)(shi)驗.本試(shi)(shi)驗設備主要(yao)用于對產(chan)(chan)品按(an)照(zhao)國家(jia)標(biao)準要(yao)求或用戶自定(ding)要(yao)求,在低溫(wen)、高溫(wen)條件(jian)(jian)下(xia),對產(chan)(chan)品的物理以(yi)及(ji)其他(ta)相關(guan)特性(xing)進行環(huan)(huan)境模擬(ni)測試(shi)(shi),測試(shi)(shi)后(hou),通過檢測,來判斷產(chan)(chan)品的性(xing)能,是否仍然能夠(gou)符合預定(ding)要(yao)求,以(yi)便于產(chan)(chan)品設計,改進、鑒(jian)定(ding)及(ji)出廠檢驗用.