The goals of MFMG-Thermal were:
1) To determine if a stream of honey in water will migrate in a temperature gradient.
2) To determine if a drop of water in honey will migrate in a temperature gradient.
To create a temperature gradient, the CGBA was heated to its maximum temperature, 37 ęC, and removed from its rack. It was placed on the Microgravity Work Area (MWA). Duxseal was placed on the heated surface, and the syringe was affixed. Duxseal was placed on the opposite side of the syringe to aid heat transfer. The temperature on each side was measured with a thermal probe. During Increment 9 astronaut Mike Fincke performed two runs.
Run 1: a stream of pure honey was injected into pure water.
The ambient temperature was 24.2 ęC. The temperature difference across the syringe immediately before the injection of the honey was 30.4 ęC – 28.4 ęC. After 10 minutes, it had relaxed to 29.5 ęC – 28.5 ęC. Fig. 9 shows the stream of honey bent toward the Duxseal, which is at the higher temperature. This could reflect some migration of the stream or buoyancy-driven convection. What is clear is that the stream did not break up into drops.
Real Time: A stream of honey 7 minutes after being injected into pure water in a temperature gradient. High temperature (30.4 ęC) is on the left while the temperature of the Duxseal on the right is 28.4 ęC.
Time lapse movie: total time is 10 minutes.
Run 2: a stream of diluted honey (50:50) was injected into pure water.
This was an interesting run. Mike Fincke improved the procedures by putting the Duxseal near the injector so that the honey stream would definitely be in the temperature gradient. He also obtained superb images of the syringe after injection and was able to achieve a large temperature difference (5 ęC) across the syringe.
Fig. 10 shows how the honey-water stream comes out of the injector and is close against the heated surface of the syringe. Notice the bubble near the plunger that is also near the wall. If its position were only because of residual buoyancy-driven convection, then the honey, which is denser than water, would be on the opposite side of the syringe. Instead, it is more likely that the bubble has migrated toward the warmer surface. However, careful examination of the video revealed that the injector tube was slightly tilted such that the honey was injected toward the surface of the CGBA and so the honey was injected toward the higher temperature side of the tube. Thus, the migration was only an artifact.
A real-time movie of a stream of honey-water (50:50) High temperature (31.5 ęC) is on the bottom while the temperature of the Duxseal on the top is 25.5 ęC. The straw inserted into the observation syringe was pushed toward the surface of the CGBA as the honey was injected, and so the honey was squirted toward the hot surface.
Realizing that the CGBA was very difficult to use, we abandoned its use and repeated isothermal experiments. Leroy Chiao on Increment 10 injected tinted water into a 20:80 honey-water mix. Dr. John Phillips on Increment 11 performed another isothermal run with pure water injected into pure honey with longer period of observation. Neither of these runs provided any additional useful information.