%0 PDF %T Convection Heat Transfer in the Presence of Apparent Slip. %A Lam, Lisa. %8 2017-04-20 %R http://localhost/files/j9602b562 %X Abstract: Structured surfaces, e.g., superhydrophobic surfaces or superoleophobic surfaces are a class of surfaces engineered on the micro- and nano-scale that resist wetting and decrease hydrodynamic drag. The capacity to design these surfaces with a variety of textures and coatings continues to develop and they are being considered for a wide variety of application areas ranging from retarding frost formation on airplane wings to drag reduction in microchannel flows. This dissertation addresses four problems related to heat transfer to flows over structured surfaces. We first investigate the problem of heat transfer in a thermally developing, steady, laminar Couette flow in the presence of hydrodynamic and thermal slip. Fluid temperature at the inlet to a parallel plate channel is prescribed, as are various combinations of isothermal and adiabatic boundary conditions along its surfaces. Analytical expressions incorporating arbitrary slip are developed for temperature profiles, and developing and fully developed Nusselt numbers. Representative results show the presence of thermal slip lowers the Nusselt number relative to the no-slip value. The second problem we consider is liquid cooling in a microgap lined with microscale ridges oriented parallel to the flow. Using available expressions for Nusselt number and Poiseuille number as a function of hydrodynamic and thermal slip length, thermal resistance expressions for a Poiseuille flow in a parallel plate channel are developed in order at assess the relative contributions of convection and caloric heat transfer. Water and a liquid metal, galinstan, are considered as the working fluids. Notably heat transfer is enhanced with the use of structured surfaces in the selected geometry. We develop a dimensionless expression to evaluate the tradeoff between the pressure stability of a liquid-solid-gas system and hydrodynamic slip. Finally, we consider entrance effects and the temperature dependence of thermophysical properties and quantify their the effect on thermal resistance. The third problem we consider is evaporation and condensation across menisci between ridge structures. We assume that the gaps between ridges, where the vapor phase resides, are closed systems; therefore, the net rate of heat transfer across menisci is zero. The reduction in apparent thermal slip length due to evaporation and condensation relative to the limiting case of an adiabatic meniscus is quantified. Results suggest that interfacial evaporation and condensation need be considered in the design of microchannels lined with structured surfaces for direct liquid cooling of electronics applications. A quantitative means to do so is elucidated. The final problem we consider is the effect of meniscus curvature on thermal slip length. Perturbation theory is used to develop expressions that account for the change to temperature that occurs in the limit of small deflections to an adiabatic meniscus. Constant heat flux boundary conditions are considered at the tips of the ridges. Results show that slip length is sensitive to meniscus protrusion angle at low solid fractions. When liquid pressure is higher than that of the gas, a negative protrusion angle exists and heat transfer is enhanced. Conversely, the presence of bubble mattresses formed because the pressure in the gas is higher than that of the liquid reduces heat transfer to the liquid at low protrusion angles.; Thesis (Ph.D.)--Tufts University, 2015.; Submitted to the Dept. of Mechanical Engineering.; Advisor: Marc Hodes.; Committee: Scott MacLachlan, Ryan Enright, Vincent Manno, Jeffrey Guasto, and Nikhil Nair.; Keyword: Mechanical engineering. %[ 2022-10-11 %9 Text %~ Tufts Digital Library %W Institution