Precooler Design

The use of mixed gases is designed to equalize the heat capacities of the two counterflow gas streams and thereby make the exchange process much more efficient. However, the expanded fluid is a mixture of liquid and gas hence a liquid-vapour separator is needed to allow the expanding liquid to precool the vapour. Figure 5.13 shows the cycle as modified by MMR Technologies [53]... 

Figure 6. Rate curves of argon on diamond at designated precooling times before...

Fluorine [Matheson] is pretreated to remove HF and SiF4 impurities and is handled in a passivated copper vacuum line designed for fluorine use. Approximately I g of NaF and four stainless steel balls are placed in a 200-mL high-pressure stainless steel Hoke cylinder [Koch Associates] and a high-pressure stainless steel needle valve [Koch Associates] is attached to the cylinder. The cylinder is evacuated on the copper line and cooled to — 196°. A total of 50 mmol of fluorine is carefully condensed into the cylinder. The cylinder valve is closed. The cylinder is allowed to warm slowly to ambient temperature in an empty, precooled Dewar flask (- 196°). It is removed from the vacuum line, shaken to loosen and spread the NaF, placed on its side for 2 days, and shaken periodically. The cylinder is reattached to the vacuum line, and the space between the valves (interspace) is evacuated. A stainless steel infrared cell (8.0 cm) with AgCl windows is attached to the vacuum line and evacuated. A high-pressure infrared spectrum (2 atm) indicates that traces of CF4 are present, but HF and SiF4 are absent. ... 

The major difficulty to limit the higher thermal efficiency of the indirect cycle is the lower core inlet temperature. For the direct cycle, the cold gas leaving the precooler can be extracted to cool the reactor pressure vessel (RPV) and the other steel structures. Therefore the core inlet temperature can be as higher as 500- 600°C. For the indirect cycles proposed before, such as MGR-GTI proposed by Yan and Lidskyl, the core inlet temperature is kept as lower as 310°C in order to cool RPV The plant busbar efficiency of MGR-GTI is about 42.1%. In order to achieve higher power plant efficiency, it seems special designs of RPV cooling should be provided for the indirect gas turbine cycle. 

A. Dynamic mechanical measurements A resonantly driven instrument, the Dupont 981 DMA was used for wide temperature scans. It is used in conjunction with a Hewlett Packard 9825S desk top computer with 6940 interface. A Hewlett Packard 9872 multicolor plotter was the output device. Design principle and operation of the DMA were described elsewhere and will not be repeated (5,6,7). Samples of approximately 1.5mm thick by 12mm in length were used. Since the adhesive samples were tacky and difficult to handle at room temperature, all samples were first molded in a hot compression molder and cooled to dry ice temperature ( 78 C), cut and mounted on precooled DMA fixtures. 

---