Cooling point

Fig. 6. Phase diagram showing the composition pathway traveled by the casting solution during precipitation by cooling. Point A represents the initial temperature and composition of the casting solution. The cloud point is the point of fast precipitation. In the two-phase region tie lines linking the...

Parallel flow, suction in center Series flow, one cooling point... 

Series flow, two cooling points Series flow, one cooling... 

The mixture has 20% 3He concentration. Only 6.7% is used in the cooling point, so that the dilution process extracts additional power in the return line until the J-T expansion (see Fig. 6.17). 

Loaded Chamber Heat Penetration Study — Load Cool Point... 

The intent of this study is to determine the coolest points within a specihed load and conhguration. Cool points originate because of the varied rate of heat transfer throughout the load. It is therefore imperative that heat penetration studies be conducted to determine cool points within a loading pattern and ensure that they are consistently exposed to sufficient heat lethality. 

Load cool points are dependent on load conhgurations and the types of items that comprise the load (liquid-hlled containers, process equipment, etc.). Prior to conducting heat penetration studies, maximum and minimum load conhgurations must be established. The penetration thermocouples are positioned within liquid-hlled containers at the cool point previously determined by container mapping studies. The probed containers should be distributed uniformly throughout the load. When the load consists of multiple layers or pallets, a sufficient number of thermo-couple-probed containers should be employed to provide an equal representation among layers. 

A heat penetration study dehning load cool points is not limited to load conhgurations composed of liquid-hlled vials. The same principles can be applied to process equipment loads (hlters, hoses, etc.) subject to steam sterilization. Penetration thermocouples are positioned at points within the process equipment suspected to be the most difficult for steam heat penetration. Temperature data are obtained from representative maximum and minimum loads in order to establish temperature prohles... 

Heat penetration studies are also employed to determine points within a load configuration that achieve higher temperatures and consequently greater Fq values. The temperature data obtained may be significant when heatable products are involved in the sterilization process and the potential for product degradation exists. The cool points established for a specified load and configuration will eventually be utilized to control the exposure time in subsequent routine production runs. The temperature sensors that control sterilization-cycle-exposure time at process temperature may be positioned within the load at the previously detected cool point. Consequently the entire load is exposed to sufficient heat lethality and achieves the desired Fq value. 

Perform microbiological challenge studies to determine the degree of process lethality provided by the sterilization cycle. The microorganisms most frequently utilized to challenge steam sterilizer cycles are Bacillus stearothermophilus and ATCC 7953. The Kaye validator equipped with 12 (minimum) thermocouples and biological indicators (10 ) shall be positioned in the detected cool points of the chamber and condenser. After the sterilization cycle is complete, the B.I s are recovered and subjected to microbiological test procedures. 

A closely related phenomenon is the volume retardation in the glassy condition. When, after rapid cooling, point A has been reached (Figure 3.6), the volume will, at a constant temperature, gradually decrease to e.g. A. Possibilities for motion of chain parts, though on a very limited scale, cause the free volume to decrease gradually, though, as we now know, an equilibrium will never be reached. The rate of volume retardation is, as a matter of fact, smaller as the temperature is lower. 

Fig. 4.8. Electrical resistivity of p-Cc. The solid points were measured under thermal equilibrium conditions and the open circles were taken on warming rapidly before /3-Ce transformed to a-Ce. The solid squares were measured on slow warming of a sample which had been rapidly cooled to 4 K (within 5 to 10 min). The solid circles were taken on slow cooling from 300 K. The insert shows p-Ce transforming to a-Ce on cooling (point A) and on warming (point B).

---