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Published byTrevin Harpham Modified over 2 years ago

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New Plate Baffle Water Flow

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Quick Simulation Use triangular prism as rough estimate of a vane Uniform heat flux on each surface –600 kWm -2 on end face (highest flux at cutback… average would be much less!) –20 kWm -2 on side faces –Symmetry at other end, stagnant air convection on top surface See what temperature copper gets to (Next, use better vane shape and heat flux)

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Flow Estimates Total power, P, to be removed from 355mm long prism ≈ 2 kW Water mass flow rate,, per pipe = kgs -1 (assuming flow speed = 2 ms -1 = 9.42 L min -1 ) Estimated temperature rise, ΔT, of cooling water ≈ 3 °C Pipe length, L, within copper = 2.1 m Average water flow rate v av = 2 ms -1 Pipe diameter, D H = 10 mm Estimated pressure drop, Δp = 0.12 Bar Nusselt number, N u, of water flow = Thermal conductivity of water, k = 0.6 Wm -1 K -1 Estimated heat transfer coefficient = 8650 Wm -2 K -1

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Very crude approximation of vane shape and input heat flux, but overall temperature distribution is comparable to previous, more accurate simulations (small image above)

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Average Outlet Water Temperature = 18 °C Inlet Water Temperature = 15 °C Racetrack path of water flow repeatedly redistributes heat from primary heat input region on left to cooler region on right. Water absorbs a lot of heat Water becomes cooler again

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Average HTC = 9000 Wm -2 K -1 Higher HTCs on thinner channels where water flow is faster

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Sharp transitions between layers increase the water pressure significantly compared to estimate for smooth cooling channel

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Comparison of Results PropertyHand estimateANSYS CFD Result Mass flow rate0.157 kgs -1 (9.42 Lmin -1 ) kgs -1 (9.27 Lmin -1 ) Average water flow2 ms ms -1 Maximum water flow 5 ms -1 (desired upper limit) ms -1 Total Pressure0.12 Bar0.375 Bar Average HTC8650 Wm -2 K Wm -2 K -1 Water temperature rise 3 °C Simulation matches back-of-the-envelope calculations (again… well done ANSYS!) Copper temperature similar to previous simulations with different flow Good To do now: try a more accurate model and put in a squirt nozzle

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