Power electronics are used for a wide variety of purposes, including in electric vehicles and e-VTOL aircraft. Nonetheless, thermal oscillation of the junction temperature due to transient load conditions remains a significant problem. In this study, an intermittent jet impingement was applied, along with transient heat flux boundary conditions of 100W, 200W, and 300W, to a thermal test chip at a frequency of 0.5 Hz (70% duty) to examine whether such an approach can successfully minimize junction temperature fluctuations, and thus, increase the durability of the Si chips. The findings of the experiments combining intermittent pulsation with varying heat fluxes show reduced hot spot temperature oscillations of 10%, 12.5%, and 16.7% at 100W, 200W, and 300W, respectively, at a Reynolds number of 8850. Hence, the use of pulsating jets provides better control over temperature fluctuation compared to steady jets. An enhancement factor is employed to characterize the merits of using pulsating jets. Compared to steady jets, the temperature oscillation coefficient shows that the use of pulsating jets enables a higher reduction in temperature oscillation at the same time averaged Re number. A correlation is proposed to calculate the enhancement factor for pulsating jets. Then, a transient numerical model is developed to estimate the frequency effect of the intermittent jet impingement to minimize temperature fluctuations due to transient heat-flux boundary conditions. To this end, pulsating-jet-velocity and heat-flux frequencies ranging between 1 Hz and 25 Hz are examined. Compared to the steady jet, the use of the intermittent jet provides excellent control of the maximum temperature limit across the studied frequencies. In addition, the vorticity rings introduced during the jet’s off period enable lower minimum temperature limit values compared to the steady jet approach, reaching as low as 5 Hz. However, below 5 Hz, the minimum temperature becomes higher than that obtained in the steady jet approach. Furthermore, 19.2 Hz is the threshold frequency below which the intermittent jet effect can be exploited to reduce temperature oscillation. No noticeable reduction in temperature fluctuation occurs above 19.2 Hz due to the higher time constant of the studied chip than the periodic times of the studied frequencies above 19.2 Hz. A temperature oscillation coefficient (ƞ) is then introduced to demonstrate the intermittent jet approach’s effectiveness for reducing temperature oscillation in isolation from the maximum temperature limitation effect. The results further reveal 8.2 Hz as the critical frequency below which the reduction in temperature oscillation is much more pronounced for the intermittent jet approach compared to the steady jet approach. A transient heat-transfer coefficient (HTC) study is also conducted to understand the role played by the vorticity rings in enhancing the HTC during the off period of the jets in the intermittent pulsation approach. To this end, a reduced model is generated to calculate the transient HTC during the decay of temperature during the off period of the pulsation. Direct jet impingement on silicon-based chips results in variations in spatial temperature between the center of the jet and the jet outlet location. This study introduces a jet outlet design that facilitates a more uniform spatial temperature distribution. To this end, the steady state numerical model is used to study the outlet configuration effect on spatial temperature reduction. The resultant data show that reducing the outlet size by 30% results in a 31% decrease in the spatial temperature variance between the stagnation point and hot spot locations. Five outlet configurations are also investigated: eight circular top outlets; eight circular side outlets; four square top outlets; eight square top outlets; and eight square side outlets. Analysis of the temperature profiles of these designs reveals that the configuration featuring eight top circular outlets produces the highest spatial temperature difference, while the configuration featuring four top circular outlets (1.4 mm diameter) produces the smallest difference. Specifically, the four top circular outlet design enables a 42% reduction in the spatial temperature difference, with a 3.8% decrease in the pressure drop between the main inlet and outlet. Additionally, the findings show that this configuration produces a higher increase in the hot spot heat-transfer coefficient compared to the eight top circular outlet configurations (from 18500 W/m2 0C to 22300 W/m2 0C, an increase of 20.5%), thus flattening the spatial heat-transfer coefficient radially. / Thesis / Doctor of Philosophy (PhD)