This investigation addresses the thermal characteristics of the major oceanic frontal systems in the Southern Ocean south of Africa based on data collected to a depth of 500 m on forty-three cruises during a fifteen year period. The width of the Agulhas Front has been shown to vary considerably in both its sea surface and sub-surface thermal manifestation as a result of mesoscale turbulence. Its mean sea surface width of 84 km has a standard deviation of 53 km, and the mean subsurface width of 37 km has a standard deviation of 33 km. The Agulhas Front. has been found to be a separate front north of the Subtropical Convergence in 56 % of the cruises investigated. It has only been observed from 18,2°E to 24,7°E, with a mean sea and subsurface temperature gradient across the Agulhas Front of 0,05 °C/km and 0, 13 °C/km respectively. It has a mean sea surface middle temperature of 17, 8° C and a mean subsurface middle temperature of 12,6° C. The mean sea and sub-surface geographic positions of the thermal expression of the Agulhas Front are 39,3° S; 22,7° E aild 39,1° S; 22,7° E. The Subtropical Convergence at surface has been found to be a single, broad frontal zone across the Central/South East Atlantic Ocean, that does not bifurcate. It has a mean sea surface middle temperature of ·14,3° C and a mean sub-surface middle temperature of 8,4° C. The mean sea and sub-surface temperature gradients across the Subtropical Convergence are O, 03 °C/km and O, 05 °C/km respectively. The mean sea and sub-surface geographic positions of the· thermal expression of the Subtropical Convergence are 41, 8° S; 21, 9° E and 41, 7° S; 22, 0° E. The Subtropical Convergence has a mean sea surface width of 146 km and a mean sub-surface width of 79 km. The Sub-antarctic Front is pressed northward from 45° S to 43° S by the Mid-Ocean Ridge in the South West Indian Ocean sector, after which it converges · with the Subtropical Convergence at approximately 60° E to form a united STC/SAF at subsurface. This united STC/SAF does not however form a "Crozet Front" by joining the Agulhas Front between 52° E and 65° E. It has a mean sea surface middle temperature of 4,4° C and a mean sub-surface middle temperature of 4,0° C. The mean sea and subsurface temperature gradients across the Sub-antarctic Front are 0,02 °C/km. The mean sea and sub-surface geographic positions of the thermal expression of the Sub-antarctic Front are 48,7° S; 18,9° E and 46,8° S; 19,9° E. The Sub-antarctic Front has a mean sea surface width of 73 km and a mean sub-surface width of 77 km. In 30 % of the sections investigated the- Antarctic Polar Front consisted of a primary and secondary front. The Antarctic Polar Front does not join the Sub-antarctic Front east of · 40° E at sub-surface and subsequently no quadruple front is formed. It has a mean sea surface middle temperature of 2, 1 ° C and a mean sub-surface middle temperature of 2,3° C. The mean sea and sub-surface temperature gradients across the Antarctic Polar Front are 0,01 °C/km and 0,02 °C/km respectively. The mean sea and sub-surface geographic position of the thermal expression of the Antarctic Polar Front are 52, 7° S; 14,9° E and 49,2° S; 20,8° E. The Antarctic Polar Front has a mean sea surface width of 66 km and a mean sub-surface width of 74 km.

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Electrical vehicles have become more popular during recent years due to their reduced greenhouse gas emissions. The research within Li-ion batteries is therefore moving fast. Presently, two-level converters transforming the current from DC to AC. However, an alternative method of power conversion is by utilizing modular multilevel converters, which can perform better harmonics than the two-level converter. This study aims to research the impact of these converters on battery cell heat generation. In doing so, developing a digital twin of the Li-ion battery cell, which in this case is a Samsung 28 Ah nickel, manganese, and cobalt prismatic battery cell, focusing on the thermal aspects such as heat generation, heat capacity, and thermal conductivity. The modular multilevel converter may also cause significant overtones, harmonics. Therefore, this study investigates the thermal impact of these frequencies. The results show that it is possible to, via experiments and simulations, determine the heat capacity and thermal conductivity of a Li-ion cell. Furthermore, the frequencies caused by the modular multilevel converter cause a temperature rise in the cell, compared to the two-level converter. Although, if the same root mean square for the modular multilevel converter current is used, the temperature rise is lower compared to DC. During the load cycles, the results show that there are slightly higher temperatures at the positive current collector side compared to the negative. It is, however, the jelly roll core that has the highest temperatures.

<p>Predmet istraživanja načelno se odnosi na razmatranje koncepta dvostrukih ventilisanih fasada (DVF) i njihov uticaj na energetsku efikasnost objekta. Ovaj koncept predstavlja jedan od primera adaptivnih fasada. Plan istraživanja zasnovan je na eksperimentalnom radu (na realnom objektu) i na numeričkim simulacijama modela objekta. Rezultati eksperimentalnog dela istraživanja pokazuju na koji način zavise termičke osobine objekta sa DVF od trenutnih meteorolo&scaron;kih uslova. Takođe, ovi rezultati poslužili su za fino pode&scaron;avanje modela i za postizanje &scaron;to vernije slike realnog objekta. Kriterijum prihvatljivosti, kada je model potvrđen, definisani su sa preporučenim statističkim indikatorima. Na taj način, formiran model u daljoj analizi je kori&scaron;ćen za definisanje sezonskih operativnih strategija. Rezultati simulacija za sve predložene operativne strategije, ocenjuju kakav je njihov uticaj na potro&scaron;nju energije za grejanje i klimatizaciju posmatranog objekta. Poređenjem sa modelima objekta sa tradicionalnom fasadom, pokazana je opravdanost primene koncepta DVF u klimatskim uslovima Beograda.</p> / <p>Research generally refers to the consideration of the concept of a double skin facades (DSF) and their impact on energy efficiency of the building. This concept is an example of adaptive facades. The research plan is based on experimental work and on the numerical model simulation. The results of experimental research works show how energy characteristics of the object with the DSF depend of current meteorological conditions. Also, these results were used to fine-tune the model to achieve as closely as possible the real presentation of the real building. The criterion of eligibility, when the model is verified, are defined with the recommended statistical indicators. Validated model in further analysis is used to define seasonal operational strategies. The simulation results for all proposed operational strategies, assess what is their impact on the building energy consumption for heating and air-conditioning. Compared to the models with a traditional facade, analysis show justification for the application of the concept of DSF in the climatic conditions of Belgrade.</p>

Effect of architecture at nanoscale on the macroscopic properties of polymer materials has long been a field of major interest, as evidenced by inhomogeneities in networks, multimodal network topologies, etc. The primary purpose of this research is to establish the architecture-property relationship of polymer networks by studying the physical and mechanical responses of a series of topologically different PTHF networks. Monodispersed allyl-terminated PTHF precursors were synthesized through ¡°living¡± cationic polymerization and functional end-capping. Model networks of various crosslink densities and inhomogeneities levels (unimodal, bimodal and clustered) were prepared by endlinking precursors via thiol-ene reaction. Thermal characteristics, i.e., glass transition, melting point, and heat of fusion, of model PTHF networks were investigated as functions of crosslink density and inhomogeneities, which showed different dependence on these two architectural parameters. Study of freezing point depression (FPD) of solvent confined in swollen networks indicated that the size of solvent microcrystals is comparable to the mesh size formed by intercrosslink chains depending on crosslink density and inhomogeneities. Relationship between crystal size and FPD provided a good reflection of the existing architecture facts in the networks. Mechanical responses of elastic chains to uniaxial strains were studied through SANS. Spatial inhomogeneities in bimodal and clustered networks gave rise to ¡°abnormal butterfly patterns¡±, which became more pronounced as elongation ratio increases. Radii of gyration of chains were analyzed at directions parallel and perpendicular to stretching axis. Dependence of Rg on ¦Ë was compared to three rubber elasticity models and the molecular deformation mechanisms for unimodal, bimodal and clustered networks were explored. The thesis focused its last part on the investigation of evolution of free volume distribution of linear polymer (PE) subjected to uniaxial strain at various temperatures using a combination of MD, hard sphere probe method and Voronoi tessellation. Combined effects of temperature and strain on free volume were studied and mechanism of formation of large and ellipsoidal free volume voids was explored.

The path to future aero-engines with more efficient engine architectures requires advanced thermal management technologies to handle the demand of refrigeration and lubrication. Oil systems, holding a double function as lubricant and coolant circuits, require supplemental cooling sources to the conventional fuel based cooling systems as the current oil thermal capacity becomes saturated with future engine developments. The present research focuses on air/oil coolers, which geometrical characteristics and location are designed to minimize aerodynamic effects while maximizing the thermal exchange. The heat exchangers composed of parallel fins are integrated at the inner wall of the secondary duct of a turbofan. The analysis of the interaction between the three-dimensional high velocity bypass flow and the heat exchangers is essential to evaluate and optimize the aero-thermodynamic performances, and to provide data for engine modeling. The objectives of this research are the development of engine testing methods alternative to flight testing, and the characterization of the aerothermal behavior of different finned heat exchanger configurations. A new blow-down wind tunnel test facility was specifically designed to replicate the engine bypass flow in the region of the splitter. The annular sector type test section consists on a complex 3D geometry, as a result of three dimensional numerical flow simulations. The flow evolves over the splitter duplicated at real scale, guided by helicoidally shaped lateral walls. The development of measurement techniques for the present application involved the design of instrumentation, testing procedures and data reduction methods. Detailed studies were focused on multi-hole and fine wire thermocouple probes. Two types of test campaigns were performed dedicated to: flow measurements along the test section for different test configurations, i.e. in the absence of heat exchangers and in the presence of different heat exchanger geometries, and heat transfer measurements on the heat exchanger. As a result contours of flow velocity, angular distributions, total and static pressures, temperatures and turbulence intensities, at different bypass duct axial positions, as well as wall pressures along the test section, were obtained. The analysis of the flow development along the test section allowed the understanding of the different flow behaviors for each test configuration. Comparison of flow variables at each measurement plane permitted quantifying and contrasting the different flow disturbances. Detailed analyses of the flow downstream of the heat exchangers were assessed to characterize the flow in the fins¿ wake region. The aerodynamic performance of each heat exchanger configuration was evaluated in terms of non dimensional pressure losses. Fins convective heat transfer characteristics were derived from the infrared fin surface temperature measurements through a new methodology based on inverse heat transfer methods coupled with conductive heat flux models. The experimental characterization permitted to evaluate the cooling capacity of the investigated type of heat exchangers for the design operational conditions. Finally, the thermal efficiency of the heat exchanger at different points of the flight envelope during a typical commercial mission was estimated by extrapolating the convective properties of the flow to flight conditions. / Villafañe Roca, L. (2013). Experimental Aerothermal Performance of Turbofan Bypass Flow Heat Exchangers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34774 / TESIS