New Plate Baffle Water Flow

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)

Flow Estimates

pcm

PT

2504.1

7513.1

1419.5H

av

D

vLp

H

u

D

kNHTC

Total power, P, to be removed from 355mm long prism ≈ 2 kW

Water mass flow rate, , per pipe = 0.157 kgs-1 (assuming flow speed = 2 ms-1 = 9.42 L min-1)

Estimated temperature rise, ΔT, of cooling water ≈ 3 °CPipe length, L, within copper = 2.1 mAverage water flow rate vav = 2 ms-1

Pipe diameter, DH = 10 mmEstimated pressure drop, Δp = 0.12 Bar

m

Nusselt number, Nu, of water flow = 144.2Thermal conductivity of water, k = 0.6 Wm-1K-1

Estimated heat transfer coefficient = 8650 Wm-2K-1

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

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

Average HTC = 9000 Wm-2K-1

Higher HTCs on thinner channels where water flow is faster

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

Comparison of ResultsProperty Hand estimate ANSYS CFD Result

Mass flow rate 0.157 kgs-1 (9.42 Lmin-1)

0.1545 kgs-1 (9.27 Lmin-1)

Average water flow 2 ms-1 1.914 ms-1

Maximum water flow 5 ms-1 (desired upper limit)

4.227 ms-1

Total Pressure 0.12 Bar 0.375 Bar

Average HTC 8650 Wm-2K-1 9000 Wm-2K-1

Water temperature rise

3 °C 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