Using an inverter-driven compressor in variable capacity heat pump systems has a main drawback, which is the extra loss in the inverter. The present experimental study aims to recover the inverter losses by using brine-cooled and water-cooled inverters, thereby improving the total efficiency of the heat pump system. In order to achieve this goal, a test rig with the air-cooled, water-cooled and brine-cooled inverters is designed and built, and a comparative analysis of the recovered heat, inverter losses and system performance is conducted when the compressor is driven by the water-cooled, brine-cooled and air-cooled inverters at three different switching frequencies for each inverter. The experimental results show that the inverter losses as a magnitude and as a ratio of the total consumed power are lowest in the brine-cooled inverter and highest in the air-cooled one at all the compressor speeds and all the inverter switching frequencies. Moreover, the recovered energy varies between 45 and 125 (W) in the water-cooled inverter, which corresponds to 63 and 69 (%) of the inverter losses; while it varies between 61 and 139 (W) in the brine-cooled inverter, which corresponds to 79 and 90 (%) of the inverter losses. It is also proved that the improvement of the system coefficient of performance (COPsys) is almost the same when the water-cooled or the brine-cooled inverter is used and varies between 0.54 and 3 (%) in comparison with using the air-cooled one. Indeed, the total isentropic efficiency of the compressor is improved slightly when using the water-cooled inverter and little more when using the brine-cooled one at the same running conditions. In addition, the total isentropic efficiency of the compressor is improved by increasing the inverter switching frequency when any of the inverters is used. The experimental results also show that cooling the inverter by the water, which comes out from the condenser, increases the maximum temperature of the base plate of the inverter about 10 °C which could cause a two-fold deterioration in the inverter median life in comparison with cooling the inverter by air. On the contrary, using the brine for cooling the inverter decreases the maximum temperature of the base plate of the inverter about 30 °C which could cause about a six-fold improvement in the inverter median life. / Capacity-controlled Ground Source Heat Pump single-family dwellings

With the advent of terrestrial digital broadcasting, new and improved digital transmitter technologies are required since existing analog transmitter technology is, for the most part, unable to adequately transmit a decodable digital television signal. This study focuses on the design and construction of a solid-state, liquid-cooled UHF digital television transmitter. Emphasis is placed on the design of the amplifier module including the amplifier card, Wilkinson splitter and combiner, input and output matching circuits, DC bias network and the system mask filter. The results of this research are also presented for two television transmitters that are installed and continue to be in use today, including analyses of specific failures that have occurred while in the field. The overall objective of this study is not only to document the research that is behind the design of this system, but also to document the construction of the transmitter for reference in system maintenance and repair as well as a basis for future design.

The need for energy is growing in the world and the market of nuclear power is now once more expanding. Some issues of the current light-water reactors can be solved by the next generation of nuclear power, Generation IV, where sodium-cooled reactors are one of the candidates. Phénix was a French prototype sodium-cooled reactor, which is seen as a success. Although it did encounter an earlier unexperienced phenomenon, A.U.R.N., in which a negative reactivity transient followed by an oscillating behavior forced an automatic emergency shutdown of the reactor. This phenomenon lead to a lot of downtime of the reactor and is still unsolved. However, the most probable cause of the transients is radial movements of the core, referred to as core-flowering. This study has investigated the available documentation of the A.U.R.N. events. A simplified model of core-flowering was also created in order to simulate how radial expansion affects the reactivity of a sodium-cooled core. Serpent, which is a Monte-Carlo based simulation code, was chosen as calculation tool. Furthermore, a model of the Phénix core was successfully created and partly validated. The model of the core has a k_eff = 1.00298 and a neutron flux of (8.43+-0.02)!10^15 neutrons/cm^2 at normal state. The result obtained from the simulations shows that an expansion of the core radius decreases the reactivity. A linear approximation of the result gave the relation: change in k_eff/core extension = - 60 pcm/mm. This value corresponds remarkably well to the around - 60 pcm/mm that was obtained from the dedicated core-flowering experiments in Phénix made by the CEA. Core-flowering can recreate similar signals to those registered during the A.U.R.N. events, though the absence of trace of core movements in Phénix speaks against this. However, if core-flowering is the sought answer, it can be avoided by design. The equipment that registered the A.U.R.N. events have proved to be insensitive to noise. Though, the high amplitude of the transients and their rapidness have made some researcher believe that the events are a combination of interference in the equipment of Phénix and a mechanical phenomenon. Regardless, the origin of A.U.R.N. seems to be bound to some specific parameter of Phénix due to the fact that the transients only have occurred in this reactor. A safety analysis made by an expert committee, appointed by CEA, showed that the A.U.R.N. events are not a threat to the safety of Phénix. However, the origin of these negative transients has to be found before any construction of a commercial size sodium-cooled fast reactor can begin. Thus, further research is needed.

Aggressive demands for high power density and low-cost power modules in the automotive sector pose significant challenges to the thermal management systems. These challenges necessitate adopting highly effective cooling technologies in power modules to remain competitive in the semiconductor industry. Furthermore, the thermal management strategy must be simple, easy to integrate, compact, effective, efficient, reliable, and economical. This thesis is an effort to investigate the impact of fin geometry on the overall performance of finned-type liquid-cooled power electronic modules in electrified transportation. The cooling system's performance metrics, including thermal resistance, pressure drop, pumping power, and mass, are discussed in depth. Various cooling technologies are benchmarked. The finned-type cooling technique is chosen over other methods due to simplicity and low pressure drop. Integrated cooling or direct cooling of the module’s baseplate is selected due to considerable thermal resistance reduction because of thermal grease elimination. Potential fabrication techniques are thoroughly explored and compared in terms of mass production and prototyping suitability. Four different fin shapes, including circular (baseline), drop-shaped, symmetric convex lens, and offset strip in the staggered arrangement, are studied herein. The cooling agent is Water and Ethylene Glycol 50% volumetric mixture (WEG 50%). Typical operating conditions in electrified vehicles (EVs) such as flow rate and inlet temperature are assumed for the numerical analysis. A grid convergence study is carried out to ensure numerical solutions are within an acceptable error band. The thermal performance evaluation results showed that, on average, offset strip, drop-shaped, and the convex lens performed 39%, 20%, and 6% better than the baseline design, respectively. Additionally, the design candidates are compared in terms of mass and estimated machining cost. The results of the baseline case are verified against empirical correlations from the literature. The maximum deviation is less than 1% and 1.2% for finned-surface temperature and pressure drop, respectively. The difference is attributed to the end-wall effects. / Thesis / Master of Applied Science (MASc)