http://yetl.yabesh.ir/yetl1/handle/yetl/4298015 Fri, 24 Apr 2026 12:30:38 GMT 2026-04-24T12:30:38Z http://localhost:80/yetl1/bitstream/id/447620/ http://yetl.yabesh.ir/yetl1/handle/yetl/4298015 http://yetl.yabesh.ir/yetl1/handle/yetl/4311037 Effect of Tin-Doped Copper Oxide Capillary-Porous Surfaces on Flow Boiling Performance of De-Ionized Water on Copper Heat Sink Minichannels Gupta, Sanjay Kumar A cost-efficient sol–gel method was utilized to synthesize tin-doped copper oxide (Sn–CuO) capillary nanoporous coatings on copper substrates in this study. The micro/nanostructured surfaces exhibited superhydrophilicity and significantly enhanced boiling heat transfer in a confined minichannel environment. Compared to uncoated copper, the coated surfaces showed a substantial reduction in wall superheat at the onset of boiling. High-speed visualization revealed that the Sn-CuO coating facilitated frequent formation and rapid departure of small spherical bubbles, which enhanced liquid replenishment and heat transfer. Among the developed coatings, the Sn-CuO film annealed at 600 °C (Sn–CuO–600) demonstrated the best thermal performance. At a mass flux of 60 kg/m2s, the critical heat flux (CHF) improved by 64.21%, 168.1%, and 203% for coatings annealed at 500 °C, 550 °C, and 600 °C, respectively, compared to bare copper. The highest heat transfer coefficient (HTC) enhancement—up to 235%—was observed with the Sn–CuO–600 coating. The superior performance is attributed to enhanced surface wettability, reduced bubble departure diameter, and shorter bubble residence time, which collectively promote efficient heat removal. This work highlights the potential of integrating superhydrophilic Sn-doped CuO coatings with minichannel flow boiling to significantly improve heat transfer and delay CHF. The results provide valuable insights into the influence of surface micro/nanostructuring on boiling dynamics and support the development of high-performance thermal management solutions for compact electronic and energy systems operating under high heat flux conditions. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4311037 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4311032 Numerical Investigation of Conjugate Heat Transfer From a Solid Torus Ranjan, Kumud; Mohamad, Shafiq; Biswal, Gloria; Rout, Sachindra Kumar; Senapati, Jnana Ranjan The present work comprehensively investigates conjugate heat transfer in a vertically oriented torus through numerical analysis using Ansys Fluent. A solid torus made of aluminum, having a constant surface temperature of 450 K, is allowed to cool using ambient air, whose temperature is 300 K. The combined influence of free convection and radiation heat transfer has been considered here. Independent parameters such as Aspect Ratio (D/d) of 2.5,5,7.5; Rayleigh number for the laminar regime in the range of 103–107 and surface emissivity ranging from 0 to 1 have been selected for the numerical study. Continuity, Momentum, Energy, and Radiation Equations were solved numerically using finite volume method (FVM). Due to the high temperature difference between the ambient air temperature and torus surface (150 K), the thermo-physical properties of the fluid were calculated using a polynomial function of temperature to achieve more accurate results. It has been observed that each parameter has a substantial impact on the overall heat transfer and also, at a higher Rayleigh number of 107 and with an increase in emissivity, both radiation and convection have a considerable role in the overall heat transfer. Temperature and velocity contours have been plotted to visualize the consequences of the parameters on overall heat transfer. Using a nonlinear regression model of the obtained results, a correlation for the overall Nusselt number has been formulated, which can be beneficial to industrial engineers. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4311032 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4311028 Thermal Conductivities of Ethylene Glycol, Propylene Glycol, and Glycerol Alharbi, Salman; Kumar, Kamal This work provides the temperature dependence of the thermal conductivities of ethylene glycol, propylene glycol, and glycerol. The experimental results are obtained using the transient hot-wire method over a temperature range of 235–350 K, depending on the liquid, and under atmospheric pressure conditions. A consistent data reduction technique minimizes the influence of buoyancy-induced convection on the experimental results. A reliable correlation of thermal conductivity values with the temperature of each liquid is provided. Additional insights into the experimental methods are obtained using numerical simulations. The velocity and temperature field induced by the measurement process are computed to understand their impact on the measured thermal conductivity. The experimental and computed results are compared to evaluate the assumptions of the transient hot-wire method. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4311028 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310952 Depth and Velocity of Ablation Under a Constant Heat Flux Mendez, Patricio F.; Prisco, Umberto Explicit closed-form expressions for the velocity, depth of ablation front, and penetration of the thermal profile valid up to a Stefan number of 30 (the vast majority of technological materials have a value below 10) and for all times in the problem of ablation under a constant heat flux are derived. The analysis is based on the blending of the asymptotic, transient, and steady-state, regimes of the above-mentioned quantities. Expressions to estimate the characteristic values representative of intermediate behaviors are also proposed. The prediction of depth and velocity of penetration calculated with the expressions proposed resulted in a maximum absolute error below 8% in comparison to the numerical solution. This model assumes a thick substrate and a criterion for minimum thickness is also proposed. Equations to predict the thickness of the heat-affected zone and of the mushy zone in ablation are also derived. The ultimate aim of this work is to provide simple and accurate expressions to predict the progress of the ablation or to select optimal process parameters in case ablation is used in manufacturing. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4310952 2025-01-01T00:00:00Z