REFRIGERATION SYSTEM制冷系(xi)統
制冷系統的設計和組裝都是基于保證工藝操作穩定性，整個制冷系統組裝于同一個機架上，位于箱體/冷阱的后部。采用雙級半封閉螺桿式壓縮機，實現低溫并減少了泄漏的風險，特別是在當吸氣壓力低于常壓的低溫階段。
每一(yi)臺雙級壓縮機都(dou)有一(yi)個D立的循環系統，既可使用R404A制冷劑(ji)，也可以采用R507制冷劑(ji)
（本方案(an)采用R404A）。每個壓(ya)縮(suo)機循環系統都安裝有(you)必要的(de)控制(zhi)閥門、安全閥門、過濾(lv)器、濕度(du)指示器、儀表、油分離器、冷(leng)(leng)凝器、視鏡(jing)、熱氣旁通閥和溫度(du)調(diao)節裝置等以保(bao)證系統操作(zuo)的(de)穩定性，并能保(bao)證足夠的(de)制(zhi)冷(leng)(leng)能力。制(zhi)冷(leng)(leng)系統同時配有(you)聚合發泡材料(liao)的(de)保(bao)溫。
盡可能(neng)采用銅焊(han)以防止泄漏，系統(tong)的(de)泄漏率檢測是以氮氣打(da)壓方式進行的(de)，如有必要使用低濃度的(de)HFC 制冷(leng)劑。在安裝前系統(tong)內部進行徹(che)底清(qing)洗，并在使用前進行干燥處(chu)理(li)。
所有制(zhi)冷(leng)循環的配(pei)置(zhi)(zhi)均保(bao)證(zheng)在(zai)各個(ge)不同的工藝(yi)階(jie)段能夠滿足冷(leng)阱或(huo)擱板的冷(leng)量供應。這種配(pei)置(zhi)(zhi)也可(ke)以(yi)保(bao)證(zheng)當一套系統故(gu)障(zhang)，凍干程序仍然(ran)可(ke)以(yi)以(yi)較低的效(xiao)率繼續進(jin)行。通過制(zhi)冷(leng)劑冷(leng)卻器(qi)可(ke)以(yi)確保(bao)制(zhi)冷(leng)效(xiao)果，在(zai)一定(ding)條件(jian)下冷(leng)卻水(shui)溫(wen)可(ke)到(dao)32°C。水(shui)冷(leng)壓縮(suo)機上的熱量控制(zhi)閥(fa)（水(shui)量調節閥(fa)）安裝在(zai)制(zhi)冷(leng)劑冷(leng)凝器(qi)的入口處， 用于優化效(xiao)率及減少冷(leng)卻水(shui)用量。
The refrigeration system is designed and assembled to ensure the specified process performance is achieved reliably. The entire refrigeration group is mounted on a frame that is positioned to the rear of the chamber/condenser. The compressors are of screw type (see item 22) of two stage, semi-hermetic compressors, providing low temperature performance and minimising the risk of leakage, especially at low temperature when the suction pressure is below atmospheric pressure.
Each compressor has a discrete circuit employing either R404 or R507HFC refrigerants (R404 used as default). Each compressor circuit is equipped with the necessary control valves, safety valves, filters, moisture indicators, gauges, oil separator, suction accumulator, condenser/liquid receiver, sight glasses, hot gas bypass valve and thermostats to enable the system to operate reliably and deliver the required refrigeration performance. Where appropriate the refrigeration circuits are insulated with polymer foam.
As far as possible brazed connections are employed and fittings such as elbows are minimised to reduce the possibility for leakage. Systems are leak checked using Nitrogen at positive pressure and low concentrations of HFC refrigerants if necessary. The systems are Nitrogen purged during brazing and dehydrated prior to operation.
To ensure the most efficient use of the installed refrigeration capacity all refrigeration circuits are configured to be able to serve either condenser or shelf cooling duties. This configuration also ensures the freeze drying process can continue, albeit at a lower The refrigerant condensers are selected to ensure refrigeration performance can be maintained with a cooling water supply up to 32°C at the specified supply rate. Thermostatically controlled valves (water regulating valves) on the water cooled refrigerant compressors are provided at the inlet of the refrigerant condensers to optimise efficiency and minimise water usage.
