ACT’s oscillating liquid cooling technology incorporates a mechanical actuator to generate an oscillatory motion of the liquid. The oscillating liquid absorbs heat with very high efficiency, thanks to the disrupted liquid-wall boundary layers. The fluid oscillation effectively “relays” the heat from the heat input area to the heat dissipation area. The heat transfer performance can be controlled by adjusting the amplitude and frequency of the actuator output.
The figure below shows the test results of oscillating water in a 1/8″ OD copper tube. The heat source and sink were attached to the two ends of this 12″ long tube. The oscillation was generated by a mechanical assembly capable of producing fluid oscillations at frequencies of 0 to 20Hz and amplitudes of 0 to 12″. As shown, the oscillating flow heat transfer, with a proper combination of oscillating frequency and stroke, can remove heat fluxes in excess of 1,300W/cm2 at an equivalent thermal conductivity close to 250,000W/m-K. For comparison, a 1/8″ OD and 12″ long copper/water heat pipe can only handle heat fluxes up to 40W/cm2. The thermal conductivities of copper and diamond materials are on the order of 380 and 1,200W/m-K, respectively.
Oscillating Liquid Heat
Transfer Test Results
(click for larger version)
Power Electronic Module with Integral Oscillating
Liquid Cooling Solution
(click for larger version)
Test Results of Power Electronic Module with Integral
Oscillating Liquid Cooling Solution (click for larger version)
The following conclusions can be drawn from the test results:
- Maximum deviations between test results and model predictions are within a few percent.
- Hot spot temperature is reduced by 6%.
- Temperature non uniformity is reduced by 75%.