A eudiometer is commonly used to measure gas volumes over a liquid. It is well-known that the height of the liquid column is proportional to the difference between atmospheric pressure and the pressure of the trapped gas. It is therefore also well-known that changes in atmospheric pressure can be detected through changes in the height of the liquid column (1, 2). We demonstrate, perhaps for the first time, that absolute atmospheric pressure can be determined simply by moving the eudiometer up and down to vary the height of the liquid column. The analysis is simplest when the vapor pressure of the liquid is negligible. For this reason, we choose to use glycerol as our liquid.Suppose that a volume of air, V, is trapped in a eudiometer containing glycerol, as shown in Figure 1. The pressure of the trapped air, P, and the height of the glycerol column, h, are related to atmospheric pressure, P atm , according to

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THTF system with instrumented spool pieces labeled 3 2 Identification of THTF heater rods, subchannel location, and inactive rods in THTF heater bundle 4 3 Cross section of a typical fuel rod simulator 4 4 Axial location of spacer-grid and fuel rod simulator thermocouples ^ 5 Diagram of THTF 6 Positions of differential pressure and pressure instrumentation for THTF Test 3.07.9 7 THTF instrumentation diagram 8 D.l Amplifier D.2 Generalized form for a large system D.3 Error due to turbine linearity: characteristic curve .... D.4 Typical densitometer calibration D.5 Sensitivity calibration D.6 Zero offset calibration D.7 PDE-200 output from test 101 (after 28-Hz notch. original data) D.8 Rod power schematic 0.9 Instrument reading as a function of response time assuming first-order lag D.IO Instrument error as a function of DAS sampling assuming first-order lag E.l vii ACKNOWLEDGMENTS In the conduct of a large experimental and analytical program, there are always a great many individuals whose contributions should be recognized. The dedicated efforts of the entire Slowdown Heat Transfer Program staff are reflected in this report. The authors express sincere appreciation to the following personnel:

NOTICE PORTIOMS OF THIS REPORT ARE tUEBiBlP It has been reprodiised from the best available cofiy to permit the broadest possible availability.

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