| 1. |
- Oseen-Senda, K. M., et al.
(författare)
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Cooling of PEMFC with pentane boiling in minichannels : A study of flow instabilities using neutron radiography visualization
- 2006
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Ingår i: 16th World Hydrogen Energy Conference 2006. - 9781622765409 ; , s. 2885-2894
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Konferensbidrag (refereegranskat)abstract
- Compared to other heat transfer systems, Polymer Electrolyte Fuel Cells are characterized by very low heat flux. In order to analyse two-phase pentane cooling of bipolar plates, high speed neutron visualizations have been performed in a circular steel tube (Di=1.1 mm, Do=2 mm) at the Institut Laue-Langevin in Grenoble, France. The flow pattern is clearly visible and can be synchronized with time resolved temperature measurements. At low mass flow rates, the pipe wall is high above the saturation temperature and the pipe filled with vapour and liquid slugs. At higher flow rates, the wall is superheated when filled with liquid and at saturation temperature when exposed to a liquid-vapour mixture. An irregular switching between these two states was observed. Superheated liquid exists in both stable and time dependent states. The ?-radiation produced by the neutrons is shown to have an important effect on the boiling process. Simplified steady and time dependent models are proposed to explain the measured wall temperature instabilities and superheat.
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| 2. |
- Oseen-Senda, K. M., et al.
(författare)
-
The cooling of PEFC with pentane boiling in minichannels : A study of flow instabilities using neutron radiography visualization
- 2007
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Ingår i: Heat Transfer Engineering. - : Informa UK Limited. - 0145-7632 .- 1521-0537. ; 28:1, s. 49-57
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Tidskriftsartikel (refereegranskat)abstract
- Polymer electrolyte fuel cells (PEFC) operate best at a steady temperature of about 80 degrees C and have a very low heat flux compared to other heat transfer applications. Two-phase pentane cooling of bipolar plates is studied in order to optimize fuel cell cooling in transport applications. High-speed visualizations of boiling pentane in a circular steel tube (D-i = 1.1 mm, D-o = 2 mm) have been performed in a Neutrograph instrument at the Institut Laue-Langevin in Grenoble, France. The heat and mass flux were both very low and appropriate for cooling of PEFC. The spatial resolution of the images is approximately 0.15 mm and the maximum frequency is 154 Hz. In the images, the liquid-vapor differentiation is clearly visible. Time resolved measurements of the outer pipe wall temperature, synchronized with the images, show that at low mass flow rates, the pipe wall is high above the saturation temperature and the pipe filled with vapor and liquid slugs. At higher flow rates, the wall is superheated when filled with liquid, and at saturation temperature during boiling when exposed to a liquid-vapor mixture. An irregular switch between these two states was observed. The superheated wall is shown to be consistent with the superheated liquid in the pipe in both stable and time-dependent states. Unfortunately, the strong gamma-radiation produced by the neutrons has a substantial effect on the onset of boiling, which is why comparisons with non-irradiated systems might be difficult. Simplified steady and time-dependent models are proposed to explain the measured wall temperature instabilities and superheat.
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