In this thesis, a Thermal Model Tool (TMT) is developed for standard Avionic Transport Rack (ATR) chassis and thermal design of a standard ATR chassis is done using developed TMT. This ATR chassis is a Digital Moving Map (DMAP) of a helicopter and the tool is used to determine the cooling channel details of DMAP. TMT decreases design process steps and eliminates the complexity of the design. Experimental studies are conducted on one of the existing chassis produced in Aselsan Inc. for different operating conditions. There are two different operating conditions for the chassis as 25 &ordm / C and 55 &ordm / C, which are given, in military standard MIL-STD-810F. Critical temperature values are measured, which are used in analytical calculations, and results are represented. At the first step, outputs of the experimental studies are used in analytical calculation in order to develop TMT. Secondly, heat dissipation rate of two different chassis are v calculated easily by using the TMT, and without making effort for CFD analysis, the necessary number of plate fins of the chassis are assessed considering given geometrical constraints and heat loads. Finally, cooling channels are generated using the results of TMT. In the next step the chassis, which are designed using the results of TMT, are analyzed numerically by using Icepak Computational Fluid Dynamics (CFD) tool and results of TMT are verified. The cooling capacities of the decided plate fins, which are obtained by TMT, are checked whether or not the required heat dissipation rates are ensured. Consequently, TMT is tested under for two different operating conditions on two different chassis. Analytical and numerical studies for both conditions are compared and discussed in detail. Comparisons show that, developed TMT results are meaningful and close to numerical results, therefore TMT can be used in forthcoming ATR chassis designs.

Doubling transistor count for every two years in a computer chip, transmitter and receiver (T/R) module of a phased-array antenna that demands higher power with smaller dimensions are all results of miniaturization in electronics packaging. These technologies nowadays depend on improvement of reliable high performance heat sink to perform in narrower volumes. Employing microchannels or open cell metal foam heat sinks are two recently developing promising methods of cooling high heat fluxes. Although recent studies especially on microchannels can give a rough estimate on performances of these two methods, since using metal foams as heat sinks is still needed further studies, a direct experimental comparison of heat exchanger performances of these two techniques is still needed especially for thermal design engineers to decide the method of cooling. For this study, microchannels with channel widths of 300 &micro / m, 420 &micro / m, 500 &micro / m and 900 &micro / m were produced. Also, 92% porous 10, 20 and 40 ppi 6101-T6 open cell aluminum metal foams with compression factors 1,2, and 3 that have the same finned volume of microchannels with exactly same dimensions were used to manufacture heat sinks with method of vacuum brazing. They all have tested under same conditions with volumetric flow rate ranging from 0,167 l/min to 1,33 l/min and 60 W of heat power. Channel height was 4 mm for all heat sinks and distilled water used as cooling fluid. After experiments, pressure drops and thermal resistances were compared with tabulated and graphical forms. Also, the use of metal foam and microchannel heat sinks were highlighted with their advantages and disadvantages for future projects.

E-bikes, often known as electric bicycles, are becoming more and more well-liked as green modes of mobility. High-capacity lithium-ion (Li-ion) batteries are utilised to power these e-bikes because of their extended cycle life, high energy density, and low self-discharge rate. The performance and longevity of these batteries may be impacted by temperature fluctuations, however. To guarantee the safe and dependable functioning of Li-ion batteries used in e-bikes, it is crucial to do temperature analysis on the batteries. In this dissertation, the thermal behaviour of a 48V 60AH Li-ion battery used in an e-bike will be studied under various cooling scenarios. The research specifically contrasts forced convection cooling using fans with broad and limited outlet ports to natural air convection cooling with large and reduced outlet ports. The study sheds light on the ideal cooling setups that might increase battery longevity and performance. The results of this study have important ramifications for e-bike producers and designers, battery producers, and energy storage system researchers. Simulations based on computational fluid dynamics (CFD) are used to simulate the thermal behaviour of the Li-ion battery under various cooling settings for the investigation. 25°C has been selected as the ambient temperature. For forced convection, the airflow rate is set at 3.5 m/s, whereas the airflow rate for natural convection is set at 0.1 m/s. The study's findings demonstrate that both natural and forced convection cooling methods may successfully lower the temperature of a Li-ion battery. However, forced air convection cooling using fans is more efficient than natural air convection at dispersing heat. These findings suggest that, owing to the higher air velocity, shrinking the outlet ports in both cooling approaches improves thermal performance.