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

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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

Heat transfer-a review of 1986 literature

This paper describes the advantages of introducing film cooling flow through the endwall upstream of the first stage nozzle guide vane. To perform these studies, a linear cascade is built. It consists of three vanes and two endwalls that form two passages. One endwall is flat and the other is contoured from upstream of the leading edge, continuing through the passage. The approach flow is of high turbulence and large length scale, representative of the engine combustor exit flow. Film cooling flow is introduced through two successive rows of slots, a single row of slots and slots that have particular area distributions in the pitchwise direction. Measurements are taken by heating the film cooling flow slightly above the main flow temperature and recording temperature distributions in the film cooling flow-main flow mixing zone at various axial planes. The single and double slot injection cases represent base-line injection geometries. They show that at lower ratios of coolant to main flow momentum fluxes, film cooling flow migrates toward the suction side due to secondary flow. At higher ratios, the pressure side endwall region is cooled more effectively. Observations are drawn by comparing the baseline injection cases with cases of different geometries for which slots are blocked partially to re-distribute mass and momentum injection rates of the emerging flow. The downstream evolutions of temperature contours are discussed. The idea is to utilize secondary flows to control pitchwise coolant distributions.Copyright © 2002 by ASME

Film Cooling Experiments With Flow Introduced Upstream of a First Stage Nozzle Guide Vane Through Slots of Various Geometries

Experimental results from a study of the effects of passing wakes upon laminar-to-turbulent transition in a low-pressure turbine passage are presented. The test section geometry is designed to simulate the effects of unsteady wakes resulting from rotor-stator interaction upon laminar-to-turbulent transition in turbine blade boundary layers and separated flow regions over suction surfaces. Single-wire, thermal anemometry techniques were used to measure time-resolved and phase-averaged, wall-normal profiles of velocity, turbulence intensity, and intermittency at multiple streamwise locations over the turbine airfoil suction surface. These data are compared to steady state, wake-free data collected in the same geometry to identify the effects of wakes upon laminar-to-turbulent transition. Results are presented for flows with a Reynolds number based on suction surface length and exit velocity of 50,000 and an approach flow turbulence intensity of 2.5 percent. From these data, the effects of passing wakes and associated increased turbulence levels and varying pressure gradients on transition and separation in the near-wall flow are presented. The results show that the wakes affect transition both by virtue of their difference in turbulence level from that of the free-stream but also by virtue of their velocity deficit relative to the freestream velocity, and the concomitant change in angle of attack and temporal pressure gradients. The results of this study seem to support the theory that bypass transition is a response of the near-wall viscous layer to pressure fluctuations imposed upon it from the free-stream flow. The data also show a significant lag between when the wake is present over the surface and when transition begins. The accompanying CD-ROM includes tabulated data, animations, higher resolution plots, and an electronic copy of this report.

/pdf/experimental-investigation-of-transition-to-turbulence-as-506fado0jy.pdf

Experimental investigation of transition to turbulence as affected by passing wakes

The heat/mass transfer analogy factor, Nu/Sh, for boundary layers on turbine blade profiles

Compact piezoelectric actuators based on an oval loop shell structure were fabricated and their vibration characteristics were investigated. The actuators can successfully create a translational motion at a high frequency and a large displacement working distance at the second resonant mode of the shell structure. As a result of a shot peening process to harden the surface and increase the strength of the shell structures, fatigue limits were enhanced. The highest operating frequency of 1444 Hz was achieved with about 1.5 mm translational displacement under an applied voltage of 100 VAC. The largest amplified displacement of 2.1 mm was obtained at a resonant frequency of 961 Hz. Displacement amplification ratios between static and resonance conditions are presented and compared. A theoretical approach was provided to estimate the natural frequencies of the oval loop shell actuators. The estimated natural frequencies of the actuators agreed with experimental values to within 12%. In addition, load bearing capacity and efficiency of one of the shell actuators was evaluated with an experimental method. The calculated actuator efficiency is around 55% when 3.1 g of mass is loaded to the actuator and an applied voltage of 140 V is applied. A possible application of the actuator, a cooling device, was demonstrated by providing its configuration and test results.

Terrence W. Simon

Papers

Heat transfer-a review of 1986 literature

Film Cooling Experiments With Flow Introduced Upstream of a First Stage Nozzle Guide Vane Through Slots of Various Geometries

Experimental investigation of transition to turbulence as affected by passing wakes

The heat/mass transfer analogy factor, Nu/Sh, for boundary layers on turbine blade profiles

High frequency, large displacement, and low power consumption piezoelectric translational actuator based on an oval loop shell