The proton beam passing through the wall area of a liquid metal (LM) target container, called entrance window, is
causing deposition of maximum high heat flux amount 140 W/cm2.Previous experimental thermo-hydraulics investigations for the MEGAPIE LM-target at the SINQ facility of Heat-
Transfer-Coefficient (HTC) using InfraRed-Thermography (IRT) have been presented at Thermosense 2006 and 2007
[1], [2] and references therein. During these investigations the IRT active sensors with applied heat fluxes of the small
and low range from 2.5 to 15.2 W/cm2 are used. The heating shell foil of the sensor has been connected to steel dish enclosing
LM target container by using electrical insulation ceramic glue. A higher, then achieved 15 W/cm2, heat flux has
lead to delaminating of the heater.
Because of interest to determinate the HTC-chart under real heat flux conditions and investigate some positive effect
of heat flux buoyancy on cooling, the idea for the High Heat Flux (HHF) IRT Sensors, using of the Low Pressure Plasma
Spraying - Thin Film (LPPS-TF) technology of the Sulzer Metco Company has been created.
The paper presents the idea of multilayer thermal sprayed construction of HHF-IRT-Sensor, few realizations and some
results of the first pre-test performed at the PSI LBE Double Pump Loop using the new sensor and the 2DD IRT methodology
presented in [1].
During the MEGAPIE Integral Test (MIT) of the 1MW liquid metal (LM) target for a spallation neutron source, infrared thermography (IRT) has been used to investigate the liquid lead-bismuth eutectic (LBE) cooling of the proton beam entry window of the target. The IRT investigations have been performed on the real MEGAPIE target on the MIT stand (MITS) at Paul Scherrer Institute (PSI) in Switzerland, few months before of the proton irradiation period of the target. In meantime the target has been successfully irradiated (from August to December 2006) at the PSI Spallation Neutron Source (SINQ) facility; for more details see web page http://megapie.web.psi.ch/.
The Goals of the MIT thermo-hydraulics investigations of the liquid LBE "flow in flow" window cooling configuration (ca. 1.25 m/s speedy by-pass jet flow into the ca. 0.33 m/s main flow), have bifocal perspective.
On one hand the goal was visualization for an observation of changes of the target cooling field pattern of the by-pass jet flow, i.e. the qualitative investigation of cooling behavior in terms of the sufficient geometrical covering of the proton beam irradiation footprint area.
On second hand the goal was determination of local convection heat transfer coefficient (HTC) on the steel wall of the proton beam entry window area of the MEGAPIE target, i.e. the quantitative values and distribution of a cooling.
For the qualitative visualization of the real, "in situ", target window cooling we have take advantage of slightly higher temperature of the by-pass jet flow LBE streaming (ca. 4°K) and we have performed so called "MIT-Warm-Jet" experiment series. For the quantitative determination of HTC instead of the real target window we have used specimen sensor dish and performed so called "MIT-KILOPIE" experiment series using the two dimensional and dynamic infrared thermography (2DD-IRT) method, which has been developed and tested in 2005 at PSI; reported during Thermosense XVIII in 2006 [1].
The results of measurements are presented in form of IRT thermograms or thermogram sequences which are extracted from the raw temperature field measurements. The in December 2006 successfully finished irradiation period of MEGAPIE project and the integrity of the whole target have shown and proved the predicted sufficiency of the window cooling.
In the scope of the Megawatt Pilot Experiment MEGAPIE, i.e. the development of a liquid metal target for a spallation neutron source, an experimental thermo-hydraulics investigation of the target proton beam entry window cooling has been performed. Goal of this investigation concerned the measurement of the local convection heat transfer coefficient (HTC) inside of the proton beam entry window area of the MEGAPIE target, in particular: determination of HTC absolute values, distribution/visualization of HTC field shape and dynamic behavior of HTC field i.e. visualization of HTC field fluctuations. Within KILOPIE's experimental set-up the following conditions of MEGAPIE target have been fulfilled: Using of liquid metal (LM) lead-bismuth eutectic (LBE); this simultaneously serves as target material and coolant. Using of T91-steel; for the shell-dish of hemispherical mock-up of the proton beam entry window. Using of original geometry of piping insertions for the simulation of internal LBE coolant flow geometry. In KILOPIE the improved Two-Dimensional and Dynamic of Infrared Thermography (2DD-IRT) Method, presented on Thermosense XXII in year 2000, has been used. In this paper the improvements of 2DD-IRT method and some result of KILOPIE experimental investigations performed at PSI in Switzerland will be presented. A specially tailored Aluchrom-steel shell is used, which allows applying a uniform and known constant heat flux deposition on the outer surface of the T91-steel hemispherical mock-up of the target window. The optical non-contact IRT equipment measures the outer surface temperature of the Aluchrom-steel heater glued to the T91-steel mock-up dish. The determination of the local convection HTC is a result of ratio of the known local heat flux from the Aluchrom-steel heater to the difference between the local inner surface temperature of the T91-steel mock-up dish and the bulk temperature of the LBE coolant.
The paper presents the 2D and dynamic (2DD) method of using infrared (IR) thermography for the visualization of the cooling efficiency of a heated wall, as this method was applied in an experimental investigation. The 2DD method allows the outer surface temperature measured by the IR thermography device to be worked out relative to the bulk coolant-fluid temperature. In this way the 2DD method makes visible the qualitative and quantitative flow characteristics within the thin contact layers at the inner surface of the wall. This flow characteristics, and more specifically the pattern of stream lines (for the detection of dead zones) and the distribution of the temperature differences between the temperature on the window outer surface and the bulk temperature of the coolant, determine the cooling efficiency. Finally animated IR thermogram sequences could be generated, allowing the spatial and temporal behavior of the flow/cooling behind the wall to be observe.
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