Experiments on pressure drop of MHD flows in manifolds

J. Reimann¹ - I. Bucenieks² - A. Flerov² - L. Heller¹ - I. Platnieks²

¹ Association KfK-EURATOM, Kernforschungszentrum Karlsruhe GmbH, IATF, Postfach 3640. 76021 Karlsruhe, Germany
² Institute of Physics, Latvian University, Salaspils-1, LV-2169, Latvia

Abstract
The design of a recently proposed self-cooled Pbl7Li blanket for a fusion reactor includes manifolds consisting, of a large "poloidal" duct and many perpendicular "radial" ducts. Although the magnetic field is perpendicular to all axes, additional pressure drops due to 3d electric currents are expected to occur because the duct dimensions differ in the magnetic field direction. Experiments with mercury were performed investigating both combining and dividing manifold flow. A test section was used with a cross section of 125 X 725 mm^2 of the poloidal duct and five radial ducts with 25 X 25 mm^2 each. The poloidal duct cross section could be reduced by inserts to 25 X 125 mm^2. Three configurations were considered: a) no insert; b) B parallel to the large side of the insert (3d flow); c) B parallel to the small side (2d flow). Additionally, the wall conductance ratio C of the channels was varied: C = 0; 0.022; 0.047: Maximum Hartmann numbers and interaction parameters were Hamax = 360, Nmax = 40. Pressure drop measurements were performed for equal flow rates in up to five radial ducts. For large N it proved that i) the results no longer differ between dividing and combining manifold flow, ii) the pressure drop becomes negligible for 2dflow, and Hi) a value larger than zero is obtained for configurations a and b. The pressure drop extrapolation to blanket relevant conditions resulted in a lower value than previously estimated.