Review on thermal energy storage with phase change: materials, heat transfer analysis and applications

The boundary layer equations for plane, incompressible, and steady flow are 

$$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Boundary Layer Theory

An introduction to heat transfer

Thank you for reading numerical heat transfer and fluid flow. Maybe you have knowledge that, people have search numerous times for their favorite books like this numerical heat transfer and fluid flow, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some malicious virus inside their computer. numerical heat transfer and fluid flow is available in our digital library an online access to it is set as public so you can get it instantly. Our books collection spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the numerical heat transfer and fluid flow is universally compatible with any devices to read.

Numerical Heat Transfer And Fluid Flow

This paper explores the recent research developments in high-heat-flux thermal management. Cooling schemes such as pool boiling, detachable heat sinks, channel flow boiling, microchannel and mini-channel heat sinks, jet-impingement, and sprays, are discussed and compared relative to heat dissipation potential, reliability, and packaging concerns. It is demonstrated that, while different cooling options can be tailored to the specific needs of individual applications, system considerations always play a paramount role in determining the most suitable cooling scheme. It is also shown that extensive fundamental electronic cooling knowledge has been amassed over the past two decades. Yet there is now a growing need for hardware innovations rather than perturbations to those fundamental studies. An example of these innovations is the cooling of military avionics, where research findings from the electronic cooling literature have made possible the development of a new generation of cooling hardware which promise order of magnitude increases in heat dissipation compared to today's cutting edge avionics cooling schemes.

Assessment of high-heat-flux thermal management schemes

Attention is given to an empirical model for transition to turbulence in oscillatory flows in straight tubes. Designed after a correlation for transition of a boundary layer on a flat plate, the model yields the laminar flow momentum thickness Reynolds number that must be met before transition to turbulence will occur. The transition point is located by comparing this to the actual momentum thickness Reynolds number. A scheme is proposed for estimating the momentum thickness Reynolds number in terms of the position within the cycle, the maximum value of the diameter Reynolds within the cycle, Re(max), and the dimensionless frequency, Valensi number. Results from an experimental study of oscillatory flow in a tube are employed to develop the model. When the flow is determined to be turbulent, it is proposed that a fully-developed, steady flow friction coefficient be applied. When the flow is laminar, the assumption of fully developed flow cannot be made; thus, a method is suggested for estimating the friction factor.

Transition of Oscillatory Flow in Tubes: An Empirical Model for Application to Stirling Engines

This paper presents hot-wire anemometry data from an experiment that replicates important features of oscillatory flows in Stirling engines. These features include impinging and sink flows, large-scale separation zones, recirculation bubbles, unsteady shear layers and spatially varying transition and relaminarization zones. In addition to a characterization of oscillatory flow, this paper presents and compares results gathered in a unidirectional investigation to determine when, during the oscillation cycle, quasi-steady results can be applied to Stirling engine design. This paper is part of a program that focuses on characterization of fluid flow and heat transfer within Stirling engines. The unsteady velocity data presented herein serves to support the development of 3-D CFD models and verify the conditions under which 1-D systems models may be applied. The ultimate goal is that Stirling engine design codes can be used with a greater degree of confidence.

Unsteady fluid dynamics simulation of a stirling engine heater head

A technique for determining local wall temperature, local surface heat flux and local convective heat transfer coefficient from a carefully-taken, near-wall temperature profile was evaluated. With the present technique, profile measurements taken with very accurate near-wall values are substituted for these separate instruments. The profiles are extrapolated to the wall to determine the local surface temperatures and their slopes are used to calculate the local surface heat flux. This technique depends on accurate positioning of a traversing temperature sensor with respect to the wall. In the present paper, the technique is evaluated in two simple flows, a fully-developed tube flow and a simple boundary layer flow. In the tube flow, local wall temperatures determined from profile measurements agreed with those obtained with an embedded wall thermocouple to within 5.3% and 12% of the wall-to-bulk temperature difference for two cases of different Reynolds numbers. Nusselt numbers determined using the near-wall profile data were compared to values obtained from two standard pipe flow correlations. Agreement with the average of two correlations was within 7.2%. For the simple, unaccelerated boundary layer flow on a flat plate, Stanton numbers determined from temperature profile measurements agreed with standard flat plate correlation values to within 8%.more » To demonstrate the utility of the technique, it as also applied to an accelerated, transitional boundary layer on a concave wall under high free-stream turbulence conditions and to an oscillatory flow within a pipe. The temperature profiles from the curved, accelerated boundary layer case, when cast in terms of wall coordinates using the profile-determined wall temperature and heat flux, agreed well with analytically-predicted profiles.« less

Evaluation of local wall temperature, heat flux, and convective heat transfer coefficient from the near-wall temperature profile

Recently, increased attention has been paid to small gas turbine units. Microturbines with fuel cells and microturbines with heaters in a Combined Heat and Power (CHP) arrangement are showing great promise for supplying distributed electric and shaft power and process or space heat. Small jet engines are becoming increasingly popular for small piloted and non-piloted aircraft. In developing the microturbine for power generation, considerable attention has been paid to improving the recuperator, which had not seen such intensive research and development activity since the years of automobile gas turbine development. Also, the small size of the microturbine has led to a preference for radial turbomachinery, including radial inflow turbines. Smaller turbomachinery and other components have led to greater interest in ceramic components and ceramic coatings. Renewed interest in radial flow turbomachinery revealed a need to better understand radial-flow component fluid mechanics such as the effects of streamline curvature on boundary layer flows. Finally, small sizes have raised attention to low Reynolds number effects, such as transition and flow separation, particularly in the development of small axial-flow turbines for use in aircraft propulsion. In this report, we review recent developments documented in the literature for these areas of interest to small gas turbine engines and comment on contributions from our research lab.

/pdf/micro-or-small-gas-turbines-1mw611hav5.pdf

Terrence W. Simon

Papers

Transition of Oscillatory Flow in Tubes: An Empirical Model for Application to Stirling Engines

Unsteady fluid dynamics simulation of a stirling engine heater head

Evaluation of local wall temperature, heat flux, and convective heat transfer coefficient from the near-wall temperature profile

Micro- or Small- Gas Turbines

Measurements of net change in heat flux as a result of leakage and steps on the contoured endwall of a gas turbine first stage nozzle