循环系统由一系列冷却和加热换热器组成，导热介质由循环泵提供动力，部件通过AISI304 不锈钢管道连接，导热介质通过搁板与产品间实现热交换。

The circuit comprises a series of cooling and heating exchangers in series through which a heat exchange medium is circulated by a pump. The components are interconnected by 304 stainless steel pipe work. The medium is circulated through the shelves to effect heat transfer to/from the product.

导热介质为低粘度硅油(5cSt)，保证了在搁板J限低温情况下温度的均匀性。

The heat exchange medium is a low viscosity 5cSt silicone oil ensuring optimum shelf temperature uniformity at the ultimate shelf temperature.

冷却换热器是钎焊的不锈钢板式换热器，减少了导热介质的流量，提高了热传导的效率，也降低了泄漏的风险。冷却换热器由来自专用压缩机的制冷剂直接膨胀制冷，由聚合发泡物保温。

The cooling exchangers are a brazed stainless steel plate construction, which minimises the volume of heat transfer fluid and heat exchanger mass to maximise heat transfer efficiency, leakage risks are also minimised. Each one is cooled by direct expansion of refrigerant from a dedicated compressor. The cooling exchangers are insulated externally with a polymer foam.

电加热器由一个带有多根加热组件的圆柱形AISI304 不锈钢容器组成，加热组件是不锈钢管式加热器。提供2 个温度调节安全装置，以避免硅油过热。一个外附在加热器的外部和一个在加热器的内部。加热器采用聚合发泡材料保温。

The electrically heated heat exchanger comprises a cylindrical stainless steel vessel fitted with multiple heating elements with stainless steel external protection.  Two thermostatic safety switches are provided to minimise the risk of over heating the silicone oil, one attached to the external surface of the heater and one embedded within the heater elements. The heat exchanger is insulated externally with a polymer material.

硅油通过泵循环。采用屏蔽泵。泵体采用聚合发泡材料保温。循环泵提供的高流速确保搁板温度均匀。一个压力开关可反馈信号可到PLC，控制泵的操作，与加热器连锁。在泵的入口及出口装有指针式压力表，用来监测泵及系统的运行。

The silicone oil is circulated by means of a centrifugal pumping system. A single motor canned pump is used for the Lyomax 1, a twin impeller/motor pump is used for machines from Lyomax 3 to and a single impeller/motor pump for  or larger. The pump body is externally insulated with a polymer foam. The pump provides a high rate of flow through the system to ensure a high degree of shelf temperature uniformity. A differential pressure switch provides feedback, to the PLC, that the pump is operating and is also electrically interlocked with the heater to prevent fluid over temperature. Dual pressure gauges are installed on the inlet and outlet of the pump to monitor the pump and system performance.

循环系统管路上还装有一个膨胀罐，以补偿不同冻干阶段时硅油的容积的变化。膨胀罐装有除湿过滤器防止水分进入导热介质。膨胀罐液位指示计（视镜形式）包括在供货范围内。

The heat exchange circuit is equipped with an expansion tank to accommodate volume changes between the various stages of the freeze drying process. The expansion tank is fitted with a silica gel moisture trap to prevent water being absorbed by the heat exchange medium. A fluid level indicator (sight glass) is provided.

加热和冷却系统可以将导热流体的温度控制在-55°C 到+80°C 之间。在稳定状态下，空载，板层温度在-40°C 到+40°C 之间时，板层温度均匀性为板层之间的温差为2°C；板层降温速率为从+20°C 到-40°C 在 60 分钟之内；加热速率为从-40°C 到20°C 在60 分钟之内。搁板Z低温度可达到-55°C。

The heating and cooling systems are automatically controlled to enable the heat exchange fluid to be controlled between -55°C and +80°C. Under steady state, unloaded, conditions the uniformity of temperature across and between shelves is 2°C within the shelf temperature range of -40°C to +40°C. Unloaded, the shelves may be cooled from +20°C to -40°C within 60 minutes for LYOMAX 40 equipped with 2 screw compressors. The ultimate minimum shelf temperature is -55°C