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REFRIGERATION SYSTEM制冷系統(tǒng)

制冷系統(tǒng)的設(shè)計和組裝都是基于保證工藝操作穩(wěn)定性，整個制冷系統(tǒng)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(xiàn)低溫并減少了泄漏的風(fēng)險，特別是在當(dāng)吸氣壓力低于常壓的低溫階段。

每一臺雙級壓縮機都有一個D立的循環(huán)系統(tǒng)，既可使用R404A制冷劑，也可以采用R507制冷劑

（本方案采用R404A）。每個壓縮機循環(huán)系統(tǒng)都安裝有必要的控制閥門、安全閥門、過濾器、濕度指示器、儀表、油分離器、冷凝器、視鏡、熱氣旁通閥和溫度調(diào)節(jié)裝置等以保證系統(tǒng)操作的穩(wěn)定性，并能保證足夠的制冷能力。制冷系統(tǒng)同時配有聚合發(fā)泡材料的保溫。

盡可能采用銅焊以防止泄漏，系統(tǒng)的泄漏率檢測是以氮氣打壓方式進行的，如有必要使用低濃度的HFC 制冷劑。在安裝前系統(tǒng)內(nèi)部進行清洗，并在使用前進行干燥處理。

所有制冷循環(huán)的配置均保證在各個不同的工藝階段能夠滿足冷阱或擱板的冷量供應(yīng)。這種配置也可以保證當(dāng)一套系統(tǒng)故障，凍干程序仍然可以以較低的效率繼續(xù)進行。通過制冷劑冷卻器可以確保制冷效果，在一定條件下冷卻水溫可到32°C。水冷壓縮機上的熱量控制閥（水量調(diào)節(jié)閥）安裝在制冷劑冷凝器的入口處， 用于優(yōu)化效率及減少冷卻水用量。

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.