Abstract
The period operation of power electronic acts as switching element, where the power dissipated consists of pulses at certain duty cycle, the semiconductor temperature oscillates and varies as a waveform. In the present study, an experimental investigation was carried out for a loop thermosyphon order to evaluate the effect of pulsate surface heat flux on the single-phase buoyancy driven convection of ethylene glycol flow through a minichannels heat sink with hydraulic diameter 1.5 mm. An electric heater block is used to supply the heat flux to minichannels heat sink in a rectangle waveform. The study is done at different heat flux frequencies of 2.777×10-3 Hz, 8.333×10-4 Hz, 5.555×10-4 Hz and 4.166×10-4 Hz, while the heat flux amplitude (2 watt), Rayleigh number (1864) and duty cycle (50 %) are kept constant. The results revealed that for a range of the measured frequency for the complete power cycle and due to unsteady state operation conditions, the pulse heat flux pattern is close to a rectangle-wave, this generates the fluid outlet temperature pattern close to a triangle-wave. The fluid outlet temperature increases with the decreases of heat flux frequency and tends to reach to the fluid outlet temperature for a constant and continuous heat flux case. Due to closed-loop of thermosyphon, the fluid inlet temperature is changed in pattern like that the fluid outlet temperature change.
Highlights
Natural convection is an important mechanism for heat transfer equipment used in various cooling systems for electronic devices
The electronic components are continuously producing heat when they are running with load or noload operation conditions, but the heat produced with load condition is greater than that produced with no-load condition, so the temperature of electronic components with load condition is greater than at no-load condition [4]
For the complete power cycle, and at high operation frequency, less time is available for heating the fluid during the on-cycle time, as seen from Table 2
Summary
Natural convection is an important mechanism for heat transfer equipment used in various cooling systems for electronic devices. The period operation of semiconductors or power electronic acts as switching element (on-off: switch) or switching frequency, i.e. they are either fully conducting or fully blocking, where the power dissipated (heat generation) in the semiconductor consists of pulses at certain duty cycle, the semiconductors temperature oscillates and varies as a waveform. This temperature oscillation causes additional mechanical stress to the soldering and welding joints inside a semiconductor module and may cause a thermal shock. Four types of working fluids were used in testing process
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