![Page 1: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/1.jpg)
Effectiveness of Linear Spray Cooling in Microgravity
Presented by
Ben Conrad, John Springmann, Lisa McGill
Undergraduates, Engineering Mechanics & Astronautics
1
![Page 2: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/2.jpg)
Heat dissipation requirements
• Remove heat fluxes of 100-1000 W/cm2
• Applicable to laser diodes, computer processors, etc.
Laser Diode Array(Silk et al, 2008)
2
![Page 3: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/3.jpg)
Heat dissipation requirements
• Current Solutions– Flow boiling– Microchannel boiling– Jet impingement– Spray cooling
Spray cooling is the most promising because it achieves high heat transfer coefficients at low flow rates.
3
![Page 4: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/4.jpg)
Limited previous microgravity research
• Yoshida, et al. (2001): single spray perpendicular to heated surface (100 mm away)
Microgravity significantly effects critical heat flux
14% variation in the critical heat flux from 0 to 1.8 Gs
• Sone et al. (1996): single spray perpendicular to heated surface (100 mm away)
• Golliher, et al. (2005): single spray angled 55⁰ in 2.2 sec. drop tower Significant pooling on the heated surface due largely to surface tension
4
Noted a decrease in Nusselt number with acceleration
• Yerkes et al. (2004): single spray in micro- and enhanced-gravity.
![Page 5: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/5.jpg)
Spray cooling – linear array
• Single-spray systems do not cover a large area (> 1 cm2)• Regner and Shedd investigated a linear array of sprays
directed 45o onto a heated surface
• Directs fluid flow towards a defined exit to avoid fluid management issues
5
(Shedd, 2007)
![Page 6: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/6.jpg)
Experiment basis & hypothesis
(Regner, B. M., and Shedd, T. A., 2007)
6
Linear spray research showed performance independent of orientation
![Page 7: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/7.jpg)
Experiment basis & hypothesis
Predict that with similar spray array, spray cooling will function independent of gravity
7
![Page 8: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/8.jpg)
Experiment design
Goal: determine variation of heat transfer coefficient h with gravity
q’’: heat flux measured from heater powerTs: Temperature of heated surfaceTin: Temperature of spray
8
![Page 9: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/9.jpg)
Closed-loop systemPump Flow Meter
Pressure SensorBladder
Filter 3 Axis Accelerometer
Spray Box
Heat Exchanger
Pressure Sensor
Differential Pressure Sensor
Therm.
Therm.
Therm.
Therm.
Liquid coolant: FC-72
9
![Page 10: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/10.jpg)
Heater design
• Ohmite TGHG 1 Ω precision current sense resistor • Four T-type thermocouples embedded in heater
25.4 mm
8.0 mm
10
![Page 11: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/11.jpg)
Spray array design
Shedd, 2007
Made from microbore tubing:
11
3.2 cm
![Page 12: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/12.jpg)
Spray array & spray box
12
Top half: spray array
Bottom half: heater
G
Z-direction
Fluid inlet & outlet
![Page 13: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/13.jpg)
Microgravity environment
• 30 microgravity (nominally 0 g) parabolas lasting 20-25s each
• 1.8 g is experienced between microgravity
13
![Page 14: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/14.jpg)
Microgravity environment
14
![Page 15: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/15.jpg)
Procedure: Flow rate Q & heat flux q”
Q (L/min):0.672.673.81
15
q” (W/cm2):24.9 25.8 26.6
Very conservative heat fluxes used due to experimental nature
![Page 16: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/16.jpg)
Epoxy seal failure
Epoxy cracked due to fluid pressure in pre-flight testing
Spray Array
Drain
Epoxy Failure
3.2 cm
16
![Page 17: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/17.jpg)
Epoxy seal failure
17
![Page 18: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/18.jpg)
Visualization shows fluid behavior
Heater
Drain
18
Camera
![Page 19: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/19.jpg)
Complex fluid behavior
19
![Page 20: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/20.jpg)
Flight data: flow rate dominates performance
20
![Page 21: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/21.jpg)
Δh is consistent with Δg for each flow rate
• h increases with microgravity• Decreases with enhanced gravity
21
![Page 22: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/22.jpg)
h vs. jerk
Increasing variability with flow rate:
Flow rate: 0.67 L/min 2.67 L/min 3.81 L/min22
Possible Relationships
![Page 23: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/23.jpg)
Shedd model for +/- 1 g
Shedd (2007) found a correlation of the form:
where the heat transfer coefficient, h, is a function of • the average spray droplet flux, Q”, and constants: • the fluid’s density, ρ,• specific heat, cp,
• Prandtl number, Pr, • an arbitrary constant, C in [m.5s-.5], for a linear spray array,• and a constant power, a.
23
![Page 24: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/24.jpg)
Microgravity results fit trend
• Q” is believed to be 10-20% high due to the broken epoxy on the spray array
24
![Page 25: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/25.jpg)
Future steps
• Effect of spray characteristics– Spray hole diameter and length– Hole entrance and exit design
• Enhanced surfaces with linear spray cooling?
Fluid Inlet
Nozzle diameter Nozzle
length
Nozzle edge type
25
(Kim, J. 2007)
![Page 26: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/26.jpg)
Conclusion
• Flow rate Q largely determines h– 2.61 % standard deviation of h
• Support for a simple relation between h and Q– Ability to predict microgravity performance with a
1g test
• Unforeseen correspondence with jerk and Q
• Further microgravity studies are needed
26
![Page 27: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/27.jpg)
Thanks
The authors are thankful to:
• the University of Wisconsin ZeroG Team
• the Multiphase Flow Visualization and Analysis Laboratory
• the UW Space, Science, and Engineering Center
• the UW Department of Engineering Physics
• the Wisconsin Space Grant Consortium
• NASA Reduced Gravity Student Flight Opportunities Program
27
![Page 28: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/28.jpg)
Questions
28
![Page 29: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/29.jpg)
29
![Page 30: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/30.jpg)
FEA confirms broken array & uneven cooling
FEA confirms the rupture caused uneven temperatures:
Cross-section:
Side with rupture, Side with spray cooling less cooling
Top down:
30
![Page 31: Effectiveness of Linear Spray Cooling in Microgravity Presented by Ben Conrad, John Springmann, Lisa McGill Undergraduates, Engineering Mechanics & Astronautics](https://reader030.vdocument.in/reader030/viewer/2022032801/56649de55503460f94adcd21/html5/thumbnails/31.jpg)
31