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


 The rotor casing of gas turbine engines is generally cooled with cooling air from compressors and then the cooling air is discharged into the passage flow of the rotor. In this paper, a novel design both for the blade tip leakage flow control and for the rotor casing and tip cooling is proposed. Cooling air is injected through a pair of inclined rows of discrete holes positioned between 30% and 50% axial chord downstream of the blade leading edge in the casing. The casing injection forms as air-curtain within the blade tip gap, and inhibits the development of the tip leakage flows and provides secondary-order cooling for the rotor tip. Air injection from the rotor casing onto flat and recessed blade tips is investigated using numerical simulations that is validated by extensive aerodynamic and heat transfer experimental data. Flow and film cooling over the blade tip and turbine overall aerodynamic performance are examined in detail for two casing injection rates. Comparisons between flat tip without casing injection (baseline) case and the casing injection cases show that the air-curtain injection significantly alters the flow structures near the casing by modifying the development and migration of the tip leakage flow. The air-curtain injection over the flat and recessed tips both generates turbine stage overall aerodynamic efficiency improvement due to the sealing effects of the casing injection, but the efficiency gain depends on the competing results between the sealing effects and the “over-blown” effects of the air-curtain injection. Applying a recess to the blade tip is generally detrimental to the efficiency improvement by the air-curtain injection. In addition to efficiency improvement, secondary-order cooling effects from the casing injection are found to provide considerable thermal protection for the blade tips. However, increasing injection rate reduces the film cooling performance over the rotor tip surfaces. The recessed tip could present better film cooling effectiveness than the flat tip in the presence of the air-curtain.

Controlling leakage flows over a rotor blade tip using air-curtain injection: Part I — Aero-thermal performance of rotor tips

Liquid piston compression technology is being explored as a way to achieve high-pressure gas compression in Compressed Air Energy Storage (CAES) systems. When combined with a porous medium, a liquid piston compressor is able to provide near-isothermal compression, and high efficiency. However, the gas being compressed can dissolve into the liquid resulting in loss of compressed gas output. Also, the dissolved gas in the liquid lines can cause aeration that causes damage to pumps and valves. To understand this gas transport phenomenon in the liquid and to evaluate the total amount of gas dissolved, a numerical model was developed. Dispersion due to the porous medium is found to be the dominant mode of mass transfer. The dispersion coefficient is calculated based on an experimental correlation that is given in terms of flow velocity, porous medium geometry and molecular diffusion coefficient. The numerical model is used to investigate a case study in which a water liquid piston is used for air compression. The amount of dissolved gas under various conditions is calculated, such as gas concentration of the inlet flow to the compressor and discharge pressure to the storage tank at the end of compression. The effects of different types of liquids are also quantified by applying in the model the different solubility values of gases in liquids.

Analysis of dissolved gas in the application of liquid piston gas compression

\n In this paper, detailed overall cooling effectiveness and associated flow patterns are presented for two distinct film hole distribution patterns over a turbine endwall: an axial-row pattern and an iso-Mach number line row pattern. Measurements, in combination with numerical simulations, are performed in a scaled-up cascade. Thermal protection for the endwall is achieved by jet-array impingement on the cold side and discrete film cooling on the hot-gas side, combined with purge air from an inclined slot that simulates the upstream seal cavity. Infrared (IR) thermography techniques are used to obtain overall effectiveness in a wide range of coolant flow ratios of 1.5–3.8%. Mach numbers at the exit of the vane cascade are 0.25 and 0.70, representing the variations of engine operating conditions. Overall effectiveness measurements and computational flowfields show that the iso-Mach number line hole pattern outperforms the hole pattern with axial rows of holes in terms of overall effectiveness levels and thermodynamic energy losses, regardless of coolant flow ratios. Increasing Mach number increases overall effectiveness levels on the endwall and higher Mach numbers generate higher effectiveness improvement for the iso-Mach number line arrangement, relative to the axial-row configuration. Additionally, adding purge air to the endwall considerably improves the overall effectiveness levels and purge air performs better for the axial-row pattern due to no direct interactions with downstream discrete coolant injection.

Terrence W. Simon

Papers

Controlling leakage flows over a rotor blade tip using air-curtain injection: Part I — Aero-thermal performance of rotor tips

Analysis of dissolved gas in the application of liquid piston gas compression

Comparisons of endwall overall effectiveness from two film hole distribution patterns at low and high exit mach numbers

Guest Editors’ Introduction: Thermal and Environmental Issues in Energy Systems

Collection of Technical Papers - 2nd International Energy Conversion Engineering Conference