This paper investigates heat transfer in a rotating disk system using preswirled cooling air from nozzles at high and low radius. The experiments were conducted over a range of rotational speeds, flow rates, and preswirl ratios. Narrow-band thermochromic liquid crystal (TLC) was specifically calibrated for application to experiments on a disk, rotating at ∼5000 rpm and subsequently used to measure surface temperature in a transient experiment. The TLC was viewed through the transparent polycarbonate disk using a digital video camera and strobe light synchronized to the disk frequency. The convective heat transfer coefficient h was subsequently calculated from the one-dimensional solution of Fourier's conduction equation for a semi-infinite wall. The analysis was accounted for the exponential rise in the air temperature driving the heat transfer, and for the experimental uncertainties in the measured values of h. The experimental data was supported by “flow visualization,” determined from CFD. Two heat transfer regimes were revealed for the low-radius preswirl system: a viscous regime at relatively low coolant flow rates, and an inertial regime at higher flow rates. Both regimes featured regions of high heat transfer where thin, boundary layers replaced air exiting through receiver holes at high radius on the rotating disk. The heat transfer in the high-radius preswirl system was shown to be dominated by impingement under the flow conditions tested.

Research Article| September 01, 2010 Goodness-of-fit Criteria for Broadband Synthetic Seismograms, with Application to the 2008 Mw 5.4 Chino Hills, California, Earthquake Kim B. Olsen; Kim B. Olsen San Diego State University Department of Geological Sciences 5500 Campanile Drive San Diego, California 92182 U.S.A. kbolsen@sciences.sdsu.edu (K. B. O.) 1San Diego State University Search for other works by this author on: GSW Google Scholar John E. Mayhew John E. Mayhew San Diego State University Department of Geological Sciences 5500 Campanile Drive San Diego, California 92182 U.S.A. kbolsen@sciences.sdsu.edu (K. B. O.) 1San Diego State University 2Now at: ExxonMobil Exploration Company, Houston, Texas Search for other works by this author on: GSW Google Scholar Author and Article Information Kim B. Olsen 1San Diego State University San Diego State University Department of Geological Sciences 5500 Campanile Drive San Diego, California 92182 U.S.A. kbolsen@sciences.sdsu.edu (K. B. O.) John E. Mayhew 1San Diego State University 2Now at: ExxonMobil Exploration Company, Houston, Texas San Diego State University Department of Geological Sciences 5500 Campanile Drive San Diego, California 92182 U.S.A. kbolsen@sciences.sdsu.edu (K. B. O.) Publisher: Seismological Society of America First Online: 09 Mar 2017 Online ISSN: 1938-2057 Print ISSN: 0895-0695 © 2010 by the Seismological Society of America Seismological Research Letters (2010) 81 (5): 715–723. https://doi.org/10.1785/gssrl.81.5.715 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kim B. Olsen, John E. Mayhew; Goodness-of-fit Criteria for Broadband Synthetic Seismograms, with Application to the 2008 Mw 5.4 Chino Hills, California, Earthquake. Seismological Research Letters 2010;; 81 (5): 715–723. doi: https://doi.org/10.1785/gssrl.81.5.715 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search Broadband synthetics obtained from scenario simulations of earthquakes with a frequency content between 0 and 10 Hz, referred to hereafter as "BBSs," are playing an increasingly important role in seismic hazard analysis. An example is the Great Southern California ShakeOut, the largest disaster response exercise in U.S. history and an annual event since 2008 (Jones et al. 2008). The drill was the first to be based on BBSs, in this case for an M 7.8 scenario earthquake on the southern San Andreas fault. Another example of the important role of synthetic ground motions is the increasing awareness of... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Encapsulated thermochromic liquid crystal (TLC) can accurately measure surface temperature in a variety of heat transfer and fluid flow experiments. Narrow-band TLC, where the colour changes over a temperature range of ∼1°C, can be used to determine surface temperature within an uncertainty of 0.1°C. Wide-band TLC, typically active over 5–20°C, allow the possibility of mapping surface temperature distributions. In part 1 of this two-part paper, an extensive set of calibrations for narrow-band and wide-band TLC is reported. This generic study provides insight into the importance and influence of the various factors governing the colour–temperature relationship. These governing effects include the variation in optical path, the spectrum of the illumination source, the lighting and viewing angles, the differences between cooling or heating cycles (hysteresis), the variation with the number of heating or cooling cycles (aging) and how this varies with TLC film thickness. Two narrow-band crystals are also specifically calibrated for application to experiments on a transparent disc rotating at high speed (∼5000rpm). Part 2 of this paper describes how these accurately-calibrated crystals were used to measure the transient surface temperature on, and heat transfer to, a rotating disc.

Encapsulated thermochromic liquid crystal (TLC) can accurately measure surface temperature in a variety of heat transfer and fluid-flow experiments. In Part 1 of this two-part paper, two narrow-band liquid crystals were specifically calibrated for application to experiments on a disc rotating at high speed (∼5000rpm). Part 2 describes how these crystals were used to measure the surface temperature on the disc in a transient experiment that models the flow of internal cooling air in a gas turbine. The TLC was viewed through the transparent polycarbonate disc using a digital video camera and strobe light synchronised to the disc frequency. The convective heat transfer coefficient, h, was subsequently calculated from the one-dimensional solution of Fourier’s conduction equation for a semi-infinite wall. The analysis accounted for the exponential rise in the air temperature driving the heat transfer, and for experimental uncertainties in the measured values of h. The paper focuses on the method used, and sample experimental results are provided to demonstrate the accuracy and potency of the technique.

The film-cooling performance of a flat plate in the presence of low and high freestream turbulence is investigated using thermochromic liquid crystal thermography. Distributions of the convective heat transfer coefficient and adiabatic effectiveness are determined over the film-cooled surface of the flat plate. Three blowing rates are investigated for a model with one hole oriented at a compound angle of 45° and with an injection angle of 30° from the flat plate surface. An increase in heat transfer coefficient due to mass injection is clearly observed in the images and is quantitatively determined for both the low and high freestream turbulence cases. The increase in heat transfer coefficient is greater than in previously published research, possibly due to the use of different, more representative thermal boundary conditions upstream of the injection location. At low blowing ratio, freestream turbulence is shown to reduce the adiabatic effectiveness due to increased mixing between the cooling air and the main flow. However, at high blowing ratio, when much of the jet has lifted off in the low turbulence case, high freestream turbulence turns its increased mixing into an asset, entraining some of the coolant that penetrates into the main flow and mixing it with the air near the surface. This paper also contributes high-resolution contour plots that show the wider spreading of cooling air over the film-cooled surface as a result of high turbulence, and the asymmetric regions of high heat transfer.

These pictures show the hue values (calibrated against temperature) of thermochromic liquid crystals on a flat surface with an oblique impinging air jet.The pictures in the left column are obtained on an insulated surface with a heated jet. For these pictures the hue values represent the adiabatic effectiveness distribution and illustrate the region of entrainment effects.The pictures in the right column are for the same insulated surface. However, in these pictures the jet is unheated; instead a micro-thin gold coating on the surface is electrically heated to produce a uniform surface heat flux. In this case, the hue values represent the heat transfer coefficient distribution and illustrate the region of enhanced heat transfer.Comparing the adiabatic effectiveness distribution to the heat transfer coefficient distribution it can be seen that there is a region of strong variation in heat transfer coefficient in which entrainment effects are small (i.e., high effectiveness). Outside this region, both adiabatic effectiveness and heat transfer coefficient are needed to calculate the overall heat transfer.

These pictures show the hue values (calibrated against temperature) of thermochromic liquid crystals on a flat surface with an oblique impinging air jet.The pictures in the left column are obtained on an insulated surface with a heated jet. For these pictures the hue values represent the adiabatic effectiveness distribution and illustrate the region of entrainment effects.The pictures in the right column are for the same insulated surface. However, in these pictures the jet is unheated; instead a micro-thin gold coating on the surface is electrically heated to produce a uniform surface heat flux. In this case, the hue values represent the heat transfer coefficient distribution and illustrate the region of enhanced heat transfer.Comparing the adiabatic effectiveness distribution to the heat transfer coefficient distribution it can be seen that there is a region of strong variation in heat transfer coefficient in which entrainment effects are small (i.e., high effectiveness). Outside this region, both adiabatic effectiveness and heat transfer coefficient are needed to calculate the overall heat transfer.

Technical Briefs Hysteresis of Thermochromic Liquid Crystal Temperature Measurement Based on Hue J. W. Baughn, J. W. Baughn Department of Mechanical and Aeronautical Engineering, University of California, One Shields Avenue, Davis, CA 95616 e-mail: jwbaughn@ucdavis.edu Search for other works by this author on: This Site PubMed Google Scholar M. R. Anderson, M. R. Anderson Department of Mechanical and Aeronautical Engineering, University of California, One Shields Avenue, Davis, CA 95616 Search for other works by this author on: This Site PubMed Google Scholar J. E. Mayhew, J. E. Mayhew Department of Aeronautics, United States Air Force Academy, CO 80840 Search for other works by this author on: This Site PubMed Google Scholar J. D. Wolf J. D. Wolf Department of Mechanical and Aeronautical Engineering, University of California, One Shields Avenue, Davis, CA 95616 Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information J. W. Baughn Department of Mechanical and Aeronautical Engineering, University of California, One Shields Avenue, Davis, CA 95616 e-mail: jwbaughn@ucdavis.edu M. R. Anderson Department of Mechanical and Aeronautical Engineering, University of California, One Shields Avenue, Davis, CA 95616 J. E. Mayhew Department of Aeronautics, United States Air Force Academy, CO 80840 J. D. Wolf Department of Mechanical and Aeronautical Engineering, University of California, One Shields Avenue, Davis, CA 95616 J. Heat Transfer. Nov 1999, 121(4): 1067-1072 (6 pages) https://doi.org/10.1115/1.2826057 Published Online: November 1, 1999 Article history Received: November 1, 1998 Revised: June 15, 1999 Online: December 5, 2007

A new periodic transient method for the measurement of local heat transfer coefficients is described. In this method, the freestream temperature is periodically heated while the local surface temperature fluctuation is measured. The local heat transfer coefficient can be determined from the frequency, the ratio of the surface temperature fluctuation to the free stream temperature fluctuation and the wall thermal properties. Measurements on a Plexiglas flat plate with a laminar boundary layer are presented as a demonstration of this method. For this demonstration the free stream is electrically heated using a fine wire cloth. The surface temperature fluctuation is measured using liquid crystals with a hue analysis technique. The results show that this is a viable method for measuring local heat transfer coefficients. Its advantages are that it approximates a uniform temperature thermal boundary condition and it is not necessary to control or measure the initial wall temperature.