Browsing by Subject "Capillary"
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Item Analytical and experimental investigation of capillary forces induced by nanopillars for thermal management applications(2010-05) Zhang, Conan; Hidrovo, Carlos H.This thesis presents an analytical and experimental investigation into the capillary wicking limitation of an array of pillars. Commercial and nanopillar wicks are examined experimentally to assess the effects of micro and nanoscale capillary forces. By exerting a progressively higher heat flux on the wick, a maximum achievable mass flow was observed at the capillary limit. Through the balance of capillary and viscous forces, an ab initio analytical model is also presented to support the experimental data. Comparison of the capillary limit predicted by the analytical model and actual limit observed in experimental results are presented for three baseline wicks and two nanowicks.Item Oxygen Deficient Metabolism in Organs: A Link to Combustion Science(2014-12-10) Miller, Jason MathewIn an attempt to better understand and model transport of oxygen, O2, from capillaries to living cells in surrounding tissue, the group combustion (O2 deficient) concept from the field of combustion science in engineering is applied to the biological field of microvascular O2 transport from capillaries to cells immersed in interstitial fluid (IF). The conventional Krogh model represents typical biological models, considering tissue cylinder with uniform oxygen source/sink term (US) (m''', g/s/cm^3) and O2 transport from capillary on axis (COA) towards the surface; engineering models consider cylinders with O2 supplied from the surface of cylinder (COS); in addition, they present i) transport (diffusion) and ii) kinetics limited sink rates and profiles for O2. Diffusion limitation causes m''' to be proportional to local O2 concentration. Thus, the present work modifies COS engineering models for COA cases and considers only diffusion limited transport of O2 to metabolic cells from IF. O2 profiles and resulting specific metabolic rates, SMRs (W/g), are generated for four models: I) COA with oxygen dependent consumption source term (O2) (COA-O2), II) COA-US, III) COS-O2, and IV) COS-US. In order to validate the current approach, the model results are verified with the following different types of experimental data: A) If SMRs (mq W/g) are given by the allometric law, kbmk^kq=am for organ k, then COS models under limiting conditions suggest -1/3Item Simulation study of surfactant transport mechanisms in naturally fractured reservoirs(2010-08) Abbasi Asl, Yousef; Pope, Gary A.; Mohanty, Kishore K.Surfactants both change the wettability and lower the interfacial tension by various degrees depending on the type of surfactant and how it interacts with the specific oil. Ultra low IFT means almost zero capillary pressure, which in turn indicates little oil should be produced from capillary imbibition when the surfactant reduces the IFT in naturally fractured oil reservoirs that are mixed-wet or oil-wet. What is the transport mechanism for the surfactant to get far into the matrix and how does it scale? Molecular diffusion and capillary pressure are much too slow to explain the experimental data. Recent dynamic laboratory data suggest that the process is faster when a pressure gradient is applied compared to static tests. A mechanistic chemical compositional simulator was used to study the effect of pressure gradient on chemical oil recovery from naturally fractured oil reservoirs for several different chemical processes (polymer, surfactant, surfactant-polymer, alkali-surfactant-polymer flooding). The fractures were simulated explicitly by using small gridblocks with fracture properties. Both homogeneous and heterogeneous matrix blocks were simulated. Microemulsion phase behavior and related chemistry and physics were modeled in a manner similar to single porosity reservoirs. The simulations indicate that even very small pressure gradients (transverse to the flow in the fractures) are highly significant in terms of the chemical transport into the matrix and that increasing the injected fluid viscosity greatly improves the oil recovery. Field scale simulations show that the transverse pressure gradients promote transport of the surfactant into the matrix at a feasible rate even when there is a high contrast between the permeability of the fractures and the matrix. These simulations indicate that injecting a chemical solution that is viscous (because of polymer or foam or microemulsion) and lowers the IFT as well as alters the wettability from mixed-wet to water-wet, produces more oil and produces it faster than static chemical processes. These findings have significant implications for enhanced oil recovery from naturally fractured oil reservoirs and how these processes should be optimized and scaled up from the laboratory to the field.