Small-Sized Pulsating Heat Pipes/Oscillating Heat Pipes with Low Thermal Resistance and High Heat Transport Capability

Abstract

Electronics (particularly power electronics) are the core element in many energy-related applications. Due to the increasing power density of electronic parts, the demands on thermal management solutions have risen considerably. As a novel passive and highly efficient cooling technology, pulsating heat pipes (PHPs) can transfer heat away from critical hotspots. In this work, we present two types of small and compact PHPs with footprints of 50 × 100 mm2, thicknesses of 2 and 2.5 mm and with high fluid channel density, optimized for cooling electronic parts with high power densities. The characterization of these PHPs was carried out with a strong relation to practical applications, revealing excellent thermal properties. The thermal resistance was found to be up to 90% lower than that of a comparable solid copper plate. Thus, a hot part with defined heating power would remain at a much lower temperature level and, for the same heater temperature, a much larger heating power could be applied. Moreover, the dependence of PHP operation and thermal properties on water and air cooling, condenser area size and orientation is examined. Under some test configurations, dryout conditions are observed which could be avoided by choosing an appropriate size for the fluid channels, heater and condenser.

Thermodynamic Analysis of the Dryout Limit of Oscillating Heat Pipes

“…In the following, the results of our compact analytical model are additionally validated with the data from Winkler et al [24]. They tested an OHP made of copper with a 1.5 × 1.5 mm 2 cross section.…”

“…Winkler et al [24] tested a 20 channel OHP made of copper with a 1.5 × 1.5 mm 2 cross section filled with acetone. They measured a constant filling ratio of 50% and increased the heat input from 0 W to 180 W and investigated the influence of the condenser sizes.…”

“…At the optimal operation point, there is a maximum heat transfer and a minimal thermal resistance. Due to different heat inputs, geometries and working fluids in previous studies [8,23,24] it is not possible to predict the dryout limit and to find an optimal filling ratio. When a dryout takes place, the flow pattern changes to annular flow and the heat transfer deteriorates rapidly.…”

“…The dryout limit also depends on the orientation position. Our experiments were conducted horizontally since the dryout takes places at a lower heat input compared to a vertical orientation [24]. For applied power electronics, it is important to consider the worst-case orientation to avoid a burnout of the electronics components.…”

Experimental Analysis of an Innovative Electrical Battery Thermal Management System

“…During these tests, a staircase function heating input was supplied to the evaporator from 1 W to 90 W. At first the thermal performance of the proposed device was evaluated in terms of average thermal resistance R eq as reported by several authors in the literature [27][28][29][30]:…”