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No description available.

No description available.

Air-conditioning systems driven by solar energy have can save primary energy and reduce peak power consumption, which is particularly important for utility providers in the summer months. Additionally solar cooling is a promising application of solar thermal technology since the cooling load is well correlated to the overall solar availability. Liquid desiccant air-conditioning, which uses a salt solution to dehumidify air, can be used in a thermally driven air-conditioning system and offers many benefits for solar applications including the ability to store solar energy in the form of concentrated liquid desiccant. The current work focuses on the Queen’s University Solar Liquid Desiccant Cooling Demonstration Project. In previous work, a pre-commercial Liquid Desiccant Air Conditioner (LDAC) was installed and experimentally characterized using a gas-fired boiler to provide heat. As part of the current study a 95m2 solar array was added as a heat source. The Solar LDAC was tested for 20 days in the summer of 2012 to evaluate performance. The solar LDAC was found to provide between 9.2kW and 17.2kW of cooling power with an overall thermal Coefficient of Performance (COP) of 0.40 and electrical COP of 2.43. The collector efficiency was 53%, and 40% of the required thermal energy was provided by the solar array. A model was developed in TRNSYS to predict the performance of the solar LDAC and simulation results were compared to the experimental results with reasonable accuracy. The validated model was then used to simulate the annual performance of the solar LDAC in Toronto, Ontario; Vancouver, British Columbia; and Miami, Florida. The highest performance was achieved in Miami, where an overall thermal COP of 0.48 was predicted. It is proposed that additional improvements be made to the system by replacing inefficient pumps and fans, adding desiccant storage, and improving the control scheme. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-10-29 16:34:02.906

In modern, low emission, gas turbine combustion systems the amount of air available for cooling of the flame tube liner is limited. This has led to the development of more complex cooling systems such as cooling tiles i.e. a double skin system, as opposed to the use of more conventional cooling slots i.e. a single skin system. An isothennal experimental facility has been constructed which can incorporate 10 times full size single and double skin (cooling tile) test specimens. The specimens can be tested with or without effusion cooling and measurements have been made to characterise the flow through each cooling system along with the velocity field and cooling effectiveness distributions that subsequently develop along the length of each test section. The velocity field of the coolant film has been defined using pneumatic probes, hot-wire anemometry and PIV instrumentation, whilst gas tracing technique is used to indicate (i) the adiabatic film cooling effectiveness and (ii) mixing of the coolant film with the mainstream flow. Tests have been undertaken both with a datum low turbulence mainstream flow passing over the test section, along with various configurations in which large magnitudes and scales of turbulence were present in the mainstream flow. These high turbulence test cases simulate some of the flow conditions found within a gas turbine combustor. Results are presented relating to a variety of operating conditions for both types of cooling system. The nominal operating condition for the double skin system was at a coolant to mainstream blowing ratio of approximately 1.0. At this condition, mixing of the mainstream and coolant film was relatively small with low mainstream turbulence. However, at high mainstream turbulence levels there was rapid penetration of the mainstream flow into the coolant film. This break up of the coolant film leads to a significant reduction in the cooling effectiveness. In addition to the time-averaged characteristics, the time dependent behaviour of the .:coolantfilm was. also investigated. In particular, unsteadiness associated with large scale structures in the mainstream flow was observed within the coolant film and adjacent to the tile surface. Relative to a double skin system the single skin geometry requires a higher coolant flow rate that, along with other geometrical changes, results in typically higher coolant to mainstream velocity ratios. At low mainstream turbulence levels this difference in velocity between the coolant and mainstream promotes the generation of turbulence and mixing between the streams so leading to some reduction in cooling effectiveness. However, this higher momentum coolant fluid is more resistant to high mainstream turbulence levels and scales so that the coolant film break up is not as significant under these conditions as that observed for the double skin system. For all the configurations tested the use of effusion cooling helped restore the coolant film along the rear of the test section. For the same total coolant flow, the minimum value of cooling effectiveness observed along the test section was increased relative to the no effusion case. In addition the effectiveness of the effusion patch depends on the amount of coolant injected and the axial location of the patch. The overall experimental data suggested the importance of the initial cooling film conditions together with better understanding of the possible mechanisms that results in the rapid cooling film break-up, such as high turbulence mainstream flow and scales, and this will lead to a more effective cooling system design. This experimental data is also thought to be ideal for the validation of numerical predictions.

We have carried out detailed thermometric and cooling history studies of several LL-, L- and H-chondrites of petrologic types 5 and 6. Among the selected samples, the low-temperature cooling of St. Severin (LL6) has been constrained in an earlier study by thermochronological data to an average rate of similar to 2.6 degrees C/My below 500 degrees C. However, numerical simulations of the development of Fe-Mg profiles in Opx-Cpx pairs using this cooling rate grossly misfit the measured compositional profiles. Satisfactory simulation of the latter and low temperature thermochronological constraints requires a two-stage cooling model with a cooling rate of similar to 50-200 degrees C/ky from the peak metamorphic temperature of similar to 875 degrees C down to 450 degrees C, and then transitioning to very slow cooling with an average rate of similar to 2.6 degrees C/My. Similar rapid high temperature cooling rates (200-600 degrees C/ky) are also required to successfully model the compositional profiles in the Opx-Cpx pairs in the other samples of L5, L6 chondrites. For the H-chondrite samples, the low temperature cooling rates were determined earlier to be 10-20 degrees C/My by metallographic method. As in St. Severin, these cooling rates grossly misfit the compositional profiles in the Opx-Cpx pairs. Modeling of these profiles requires very rapid cooling, similar to 200-400 degrees C/ky, from the peak temperatures (similar to 810-830 degrees C), transitioning to the metallographic rates at similar to 450-500 degrees C. We interpret the rapid high temperature cooling rates to the exposure of the samples to surface or near surface conditions as a result of fragmentation of the parent body by asteroidal impacts. Using the thermochronological data, the timing of the presumed impact is constrained to be similar to 4555-4560 My before present for St. Severin. We also deduced similar two stage cooling models in earlier studies of H-chondrites and mesosiderites that could be explained, using the available geochronological data, by impact induced fragmentation at around the same time. Diffusion kinetic analysis shows that if a lower petrological type got transformed by the thermal effect of shock impacts to reflect higher metamorphic temperature, as has been suggested as a possibility, then the peak temperatures would have had to be sustained for at least 10 ky and 80 ky, respectively, for transformation to the petrologic types 6 and 4. Finally, we present a model that reconciles textural data supporting an onion-shell parent body of H-chondrites with rapid cooling rate at high temperature caused by impact induced disturbance, and also discuss alternatives to the onion shell parent body model. (C) 2016 Elsevier Ltd. All rights reserved.

The contributions to knowledge documented in this doctoral thesis are two-fold. The first contribution is in the application of a new biomimetic design tool called BioTRIZ. Its creators claim it can be used to facilitate the transfer of biological principles to solve engineering problems. The core case-study of this thesis documents how this tool was used to frame and systematically explore low-energy solutions to a key technical problem in the underdeveloped field of radiative cooling. Radiative cooling is a passive mechanism through which heat from a building can be rejected to the sky – an abundant but underused natural heat sink. Published in the Journal of Bionic Engineering, the study was the first independent application of BioTRIZ in the academic literature. The second contribution to knowledge is in the design, development and testing of the most promising biomimetic concept to come out of the BioTRIZ radiative cooling study. ‘Heat-selective’ insulation gives a roof mass a cool view of the sky because integrated pathways focus and channel longwave thermal radiation through it. It is biomimetic because it achieves infrared transparency by adding structural hierarchy to the component, rather than manipulating the properties of the material itself. Test panels on a rooftop in central London cooled to between 6 and 13 degrees below ambient temperature on May and April nights. Radiative cooling powers of between 25 and 70 W/m2 were measured when plates were at ambient temperature. Daytime radiative cooling below ambient temperature occurred when clouds blocked direct sunlight. Radiative cooling power was increased by 37% using reflective ‘funnels’. Two additional BioTRIZ analyses are presented as minor case studies. They each attend to a key technical problem in the field of passive thermal energy storage in buildings. They serve to illustrate the type of results that can be expected from using BioTRIZ during low-energy building design.

Recent studies have shown that thermophotovoltaic (TPV) technology is a promising source of high power density generation. Enhanced TPV systems can theoretically provide power densities of up to 100 W/cm2. The inherent ineffiencies in the system dictate that up to 90% of that energy is not converted to electrical power, and must be removed as waste heat to ensure that the components are maintained at a reasonable operating temperature. The present study addresses this issue by investigating the suitability of using spray cooling techniques to remove heat generated by power densities of up to 100 W/cm2. A simple, scaleable experiment was designed using low-cost commercially available components to study the effects that spray mass flux and droplet size have on the heat removal capacity of the system. A series of nozzles were used so that mass flux and droplet size could be studied independently, giving high resolution to the data so that predictive correlations could be developed over the range of parameters varied in the study. / US Naval Reserve (USNR) author.

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Este trabalho apresenta a analise do efeito da concentração da mistura etilenoglicol / água, pressão do sistema, rotação da bomba e temperatura, sobre o fenômeno cavitação em sistemas de arrefecimento, tendo dois principais objetivos: 1 Explorar as principais características do fenômeno cavitação, através da analise crítica e citação de publicações existentes; 2 Mapear as condições de trabalho de um sistema de arrefecimento, para então simular em bancada as interações da variação dos fatores citados acima, comparando os resultados com publicações já existentes, contribuindo então com um banco de dados que possibilite a otimização do dimensionamento de novos sistemas de arrefecimento. / This work presents the effect analysis of the water / ethyleneglycol mixture, system pressure, pump speed and temperature upon the cavitation phenomenon in cooling systems. Moreover, it has two main targets which are: 1 To explore the main features of the cavitation phenomenon through a critical analysis and citation of available publications; 2 To monitor the cooling system work conditions in order to simulate in a test rig the variation of the parameters described above, understanding its interaction, for than to provide a database that make possible the design optimization of new cooling systems.