Veterans with different Gulf War syndromes have biochemical evidence of neuronal damage in different distributions in the basal ganglia and brainstem.

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We have measured the pressure drop on various cablein-conduit conductors with different void fractions, number of suands and flow areas. To carry out these measurements, supercritical helium is circulated through a loop containing several conductor sections instrumented with cold pressure transducers. A cold centrifugal pump is used to force the helium through the loop at flow rates of up to several grams per second. The modular design of the flow loop allows for relatively easy insertion of different test sections. Pressure drops, measured at different temperatures and mass flow rates, are correlated using classical friction factor analysis. Some variation in friction factor appears to result from temperature or helium property changes. PUMP HOUSINGIntmduc tion Figure 1. Liquid Helium Flow Facility schematic. The present work reports pressure drop measurements and friction factor data on five Merent cable-in-conduit conductor sections tested with faced flow supercritical helium in the 1.8 K to 5 K temperature range. In applications of cable-inconduit conductors the inlet and outlet conditions of the refrigeration plant, the pumping power requirements, and the mechanical design of the conductor itself are all strongly influenced by the pressure drop. This work indicates that while classical friction factor analysis produces a fair correlation of the data there is still room for improvement in the correlations with regard to variations in both conductor geometry and helium properties. ExDerimental Ap~a~atusThe experiments were carried out in the Liquid Helium Flow Facility (LHFF) which consists of a five meter long 20 cm inside diameter horizontal dewar with a cold centrifugal pump mounted on one end and a coiled copper heat exchanger in a helium bath on the other end. The LHFF, shown schematically in Fig. 1, has two cooled shields: the outer shield is cooled by liquid nitrogen and the inner shield is cooled by two phase helium (He) at 4.2 K from a helium liquefier operating in closed cycle refrigeration mode.During operation the average temperature of the central inner shield is estimated to be near 5 K. The temperature of the end boxes is estimated to be around 25 K due to the conduction Manuscript received September 24, 1990. resistance of the stainless steel expansion bellows located between the cooled inner shield and the end boxes. Wiring feedthroughs for instrumentation pass through removable flanges at the pump end of the LHFF and are heat sunk to the inner end box flange. A detailed description of the facility is provided in references 1, 2 and 3. The removable test loop is connected between the pump and the heat exchanger. The upper loop consists of an inlet expansion bellows. a venturi flowmeter, three test sections and an outlet expansion bellows. All components are connected with indium seals to facilitate the installation of different test sections in the loop. Test section temperatures are measured at the inlet and outlet of each section using Scientific Instrumentsgermanium resistance thermometers ...