Test Report on ISR Double-Loop, Spray-Cooled Inverter
- ORNL
The Isothermal Systems Research, Inc. (ISR) double-loop, two-phase spray cooling system was designed to use 85 C transmission oil to cool a heat exchanger via a second cooling loop. The heat exchanger condenses the working fluid vapor back to liquid inside a sealed enclosure to allow for continuous spray cooling of electronics. In the ORNL tests, 85 C water/ethylene/glycol (WEG), which has better thermal properties than transmission oil, was substituted for the transmission oil. Because the ISR spray-cooling system requires a second cooling loop, the final inverter might be inherently larger than inverters that do not require a second-loop cooling system. The ISR test setup did not include a dc bus capacitor. Because the insulated gate bipolar transistor (IGBT) conduction test indicated that the ISR test setup could not be properly loaded thermally, no switching tests were conducted. Therefore it was not necessary to attach external capacitors outside the test setup. During load situations not exceeding 400A, the WEG inlet temperature was higher than the WEG outlet temperature. This meant that the 85 C WEG heat exchanger was not cooling the inverter and became a thermal load to the inverter. Only when the load was higher than 400A with a higher coolant temperature and the release valve actuated did the WEG heat exchanger start to cool the 2-phase coolant. The inverter relied strongly on the cooling of the huge aluminum enclosure located inside the ventilation chamber. In a hybrid vehicle, the inverter is situated under the hood, where the dependency on cooling provided by the enclosure may become a problem. The IGBT power dissipation with both sides being spray cooled was around 34 W/cm{sup 2} at 403A, with 995W total IGBT loss at 113.5 C projected junction temperature before the release valve was actuated. The current loading could rise higher than 403 A before reaching the 125 C junction temperature limit if the pressure buildup inside the enclosure could be prevented by improving the secondary cooling loop. This 34 w/cm{sup 2} was an average across all dies. There is no doubt that the cooling capability of the ISR spray-cooling test setup can be improved by (1) lowering the WEG inlet temperature from 85 C to say 70 C, this would condense the vapor better and lower the container pressure, (2) modification of the vapor condenser inside the container to cool both the vapor and the liquid of the 2-phase coolant, in the present setup only the vapor is cooled by the condenser inside the container, and (3) lower the liquid temperature through (1) and (2) to avoid the vaporization that causes cavitations in the pump for ensuring the pump's life expectance.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Power Electronics and Electric Machinery Research Facility
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 931316
- Report Number(s):
- ORNL/TM-2006/622; VT0302000; CEVT022; TRN: US200813%%300
- Country of Publication:
- United States
- Language:
- English
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