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In this paper, a mathematical modelling and numerical simulation of the thermal behaviour of the paraffin slurry in a vertical rectangular channel are presented. A continuum model has been developed taking into account the energy balances of the phase change material (PCM) solid particles and the mixture as well to describe the temperature distribution and the local heat exchange between the slurry...
The new developments in absorption systems for air-conditioning applications respond to the new energetic and environmental situation that requires systems more efficient, use of renewable energy sources, such as thermal solar energy, and integration in polygeneration systems for the energy supply of buildings. Among these new developments, it's of great interest to mention absorption systems designed...
A boundary layer analysis is presented for the mixed convection past a vertical wedge in a porous medium saturated with a nanofluid. Numerical results for friction factor, surface heat transfer rate and mass transfer rate have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt and Lewis number Le. The dependency of...
Different thermal hydraulic limiting phenomena's are important to be studied during the natural convection cooling of a hypothetical irradiated Low Enriched Uranium (LEU) plate's target. The irradiated LEU targets are used for the production of the medical isotope molybdenum -99 (Mo-99), whose decay product, technetium -99 (Tc-99) is used in the majority of medical diagnostic imaging procedures. After...
With the recent advancements in the electronics industry, thinner systems with greater functionality are on demand. Natural convection air-cooling is the method of choice for many low power electronics applications due to cost, availability, and reliability. However, its performance is very limited due to buoyancy dependent weak flow. Therefore, there is a need for further enhancement of natural convection...
An experimental study has been performed with a single liquid-vapor meniscus formed in a vertical channel of 600 μm width between two flat parallel plates. A 10 μm thick stainless steel heating foil forms a part of one of the flat plates. HFE7100 was used as test fluid. Liquid is sucked into the gap between the plates due to capillary forces and evaporates inside the gap under steady state conditions...
In this paper, we present an analysis aiming at assessing the feasibility and economic performance of a solar-assisted air-conditioning system for a middle class house under the climatic conditions of Tunis City. A single effect water-lithium bromide absorption machine, with a cooling capacity of 10 kW is considered. Various simulations are carried out using the TRNSYS and EES programs. The calculations...
Modeling conduction heat transfer in electronic systems has gained some maturity over the past 3 decades. Although new modeling challenges were associated with 3D stacked dies or packages, some modeling approaches were proposed to handle this rather complicated multiple heat source problem. An even newer problem has started to emerge related to this growing tendency towards exploiting the vertical...
Dense packaging of electronic components generates very high heat fluxes and therefore results in challenges for proper thermal management of such components. Microchannel based evaporators with phase changing liquids are regarded as a promising solution for such high heat flux cooling applications. Due to confinement of flow and differences in the relative importance of governing phenomena, the two-phase...
Fins are commonly used to increase surface area for enhancing heat transfer to the ambient air or other coolants. The finite thermal conductivity of the fin material is a limiting factor in the heat transfer because of the thermal resistance and temperature drop across the length of the fins. The ideal system should have fins of very high thermal conductivity, resulting in isothermal fins and 100%...
Time-dependent thermoelectromechanical behavior of metal contacts in microelectromechanical system (MEMS) devices and packaging is studied. The analysis relates the electrical constriction resistance to contact temperature and contact surface evolution over time, using a microcontact asperity creep model for metal microcontacts under continual applied or residual stresses. The effects of contact temperature...
The paper presents the results of investigating the effect of Latitude angle and environmental temperature on the thermal behavior and performance of a fully equipped, air-conditioned, zero energy house located in a desert residential compound. It makes use of the thermal design and analysis tools presented in other work and extends the investigation to include different site environmental characteristics...
Experiments were performed on natural convection heat transfer from circular pin fin heat sinks subject to the influence of its geometry, heat flux and orientation. The geometric dependence of heat dissipation from heat sinks of widely spaced solid and hollow/perforated circular pin fins with staggered combination, fitted into a heated base of fixed area is discussed. Over the tested range of Rayleigh...
When constructing efficient solar energy harvesting systems, it is important to connect the photovoltaic (PV) elements in the configuration which maximizes the absorbed solar energy. This undoubtedly gives the best possible efficiency for the system. The usage of fractal topologies to arrange the PV elements spatially is suggested. Our goal is to find the best possible configuration for the same number...
Although diesel vehicles have features of low fuel consumption and high durability, stricter diesel emission standards have been set, and the after-treatment of exhaust gas is needed. In this study, as a potential catalyst-free continuous regeneration, the after-treatment system using a carbon-fiber filter was investigated, where diesel particulates are burned by electric heating. In experiments,...
Perforated plate matrix heat exchangers (MHE) are employed in applications that require high compactness (typically greater than 1500 m2/m3), high effectiveness (typically greater than 95%), and a small length (typically a few mm to a few hundred mm). There are no methods known in open literature for the complete sizing of the MHE. In this paper we, a method for the optimum sizing of MHE is presented...
The thermo-hydrodynamic behaviour of lubricant films strongly depends on the operating conditions (pressure, speed), on the physical properties of the lubricant, on the temperature level and is often nonlinear. The thermo-hydrodynamic study of a thin fluid film between two parallel planes in relative motion is presented in this paper. The case considered is that of not fully-developed thermal conditions...
Heat exchangers with very high effectiveness, typically greater than 95%, are required in all cryocoolers. Conventional experimental methods cannot be used for the determination of the effectiveness of cryogenic heat exchangers since the uncertainty in temperature measurement typically 0.1 K at room temperature to 0.3 K at cryogenic temperatures can result in an uncertainty of 1 to 2% in effectiveness...
A numerical micro-scale model is developed to study the behavior of dendrite growth in presence of melt convection. In this method, an explicit, coupled enthalpy model is used to simulate the growth of an equiaxed dendrite, while a Volume of Fluid (VOF) method is used to track the movement of the dendrite in the convecting melt in a two-dimensional Eulerian framework. Numerical results demonstrate...
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