Speaker
Description
ISIS Neutron and Muon source houses a solid methane moderator in the Target station 2, operational since 2009, includes pure aluminium foam to enhance cooling performance and neutron moderation efficiency. Pure Aluminium offers high thermal conductivity at cryogenic temperatures (Woodcraft, 2005) and a porous structure that increases methane contact area. The new moderator assembly consists of a plate heat exchanger sandwiched between aluminium foam and enclosed within a welded aluminium alloy shell. This study investigates three key aspects thermal performance and structural design:
(1) The impact of mechanical contact between the foam and the heat exchanger on thermal performance
2) The cooling improvements provided by the foam compared with an empty moderator volume
(3) The mechanical behaviour of the foam and shell under operating pressures.
Experimental tests will measure thermal behaviour with and without foam under varying internal gas conditions (evacuated, nitrogen filled) supported by controlled heating via a heating element. The Structural performance will be assessed through pressurisation cycles and burst testing. Finite element simulations have been conducted internally at ISIS for the strength of the moderator. Thermal ANSYS simulations will also be carried out on the moderator to assess the temperature variations across the various components of the moderator, time taken to achieve steady state heat flow, the temperature upon achieving this. All simulations will be compared to the physical tests.
The proposed experiments will inform us of the importance of contact between the heat exchanger and aluminium foam, and whether the introduction of poor thermally conducting material between these two components has an impact on the heat transfer. The mechanical tests will inform us on the failure pressure and mode in the heat exchanger and whether the foam provides any structural rigidity.