With the advent of the new high Tc superconductors, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In our investigations we examine the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions. Using a platinum hot wire technique, it is verified that there is a premature transition to film boiling in the transient case at power levels significantly lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity.

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Fluid-to-particle heat transfer coefficients (h$ rm sb{fp}$) associated with food and model particles under simulated aseptic processing conditions were experimentally evaluated, and verified using measured inactivation kinetic parameters of the enzyme trypsin. Convective heat transfer coefficients were determined initially using two methods: a rate method based on evaluated heating/cooling rate indices (f$ rm sb c$/f$ rm sb h$) and a ratio method based on the ratio of temperature difference between the medium and particle locations. / Carrot and potato tissue in the form of finite cylinders of different lengths (0.02-0.04 m) and diameters (0.016-0.023 m) were used for evaluating h$ rm sb{fp}$ associated with aqueous CMC solutions (0-1.0% w/w) at temperatures ranging from 50 to 80$ sp circ$C and at relatively low fluid flow (0.2 to $0.7 times10 sp{-3}$ m/s) conditions. Carrots generally gave higher h$ rm sb{fp}$ values (100-550 W/m$ sp2$C) compared to potatoes (80-450 W/m$ sp2$C). Laminar flow natural convection dominated the flow regime. Hence, the Nusselt number was modeled as a function of Rayleigh's number which resulted in coefficients of determination (R$ sp2$) greater than 0.80. / A pilot scale holding tube simulator was designed and fabricated for routine/rapid gathering of heat penetration data which may be experienced in high temperature short time processing conditions. / Using the simulator under conditions comparable to industrial applications, and a full factorial experimental design, h$ rm sb{fp}$ values were estimated using finite cylinders of Teflon and potato tissue of different sizes (length: 0.020-0.0254 m; diameter: 0.0159-0.0254 m), and spherical Teflon particles (diameter 0.0191 m) in food grade CMC solutions (0-1.0% w/w). Operating temperatures were 90, 100 and 110$ sp circ$C, and flow rate was varied from 1.0-$1.9 rm times10 sp{-4} m sp3$/s. Average h$ rm sb{fp}$ values ranged from 56 to 966 W/m$ sp2$C depending on size, shape, fluid concentration, particle orientation, and tube diameter. Differences caused by different particle materials were accounted for by introducing a thermal diffusivity ratio in developed dimensionless correlations for both mixed and forced convective heat transfer to spherical and finite cylindrical particles under simulated aseptic processing conditions. / Thermal inactivation of trypsin (bovine pancreas type III) in low and high pH media was studied at temperatures ranging from 90-130$ sp circ$C. Comparative studies of its kinetic data with other bioindicators indicated the enzyme to be suitable for HTST verification/validation purposes. Further studies revealed, probably depending on pH, that trypsin was more susceptible to thermal inactivation at temperatures around 70$ sp circ$C. (Abstract shortened by UMI.)

The successful design of a long-lived and efficient gas turbine engine requires a good knowledge of the thermal and aerodynamic performances of the components of the turbine. Of particular importance, is the heat transfer rate from the hot gases to the cooled turbine blades, since this limits the maximum turbine entry temperatures which can be obtained. Much gas turbine research is concentrated on experimental modelling and measurements to assist in the development of improved theoretical prediction techniques. The difficulties of instrumenting fully rotational rigs, which are necessary for a full understanding of the complex three dimensional flow in the turbine, have, however, to a large extent, limited most experimental research to stationary facilities. A technique is described which will allow heat transfer rate measurements to be made on fully rotating test facilities using mutlilayered model turbine blades comprising an electrical insulator on a metal base. An accurate and computationally efficient method for determining the surface heat flux to a multi-layered model turbine blade is developed theoretically, together with a method for calibrating the thermal properties of the multi-layered system. This method allows the existing successful heat flux measurement technique, which utilises electronic analogue circuitry in conjunction with thin film surface thermometers on a model made from a thermal insulator, to be extended for application to multi-layered models. The production of test models by the application of a vitreous enamel (as an electrical insulator), to a mild steel, is identified as the most suitable coating technique for experimental application. Radiant and wind tunnel testing of multi-layered cylindrical models are described, which confirm that the method is both practical and accurate.

No description available.

Vita. / Digitized by Kansas Correctional Industries

Qiu, Can = / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 82-87). / Abstracts in English and Chinese. / Qiu, Can = / Abstract --- p.i / 摘要 --- p.ii / Acknowledge --- p.iii / Table of Contents --- p.iv / List of Figures --- p.v i i / List of Tables --- p.xi / Chapter Chapters I --- Introduction --- p.1 / Chapter 1.1 --- Turbulence --- p.1 / Chapter 1.2 --- Rayleigh-Benard convection --- p.3 / Chapter 1.2.1 --- Physics picture-Motion in the convection cell --- p.4 / Chapter 1.2.2 --- The governing equations and parameters --- p.6 / Chapter 1.2.3 --- Multilayer convection --- p.9 / Chapter 1.2.4 --- The Nu scaling --- p.9 / Chapter 1.2.5 --- Boundary layers --- p.11 / Chapter 1.3 --- Present work and the organization of the thesis --- p.14 / Chapter II --- Experimental Setup --- p.16 / Chapter 2.1 --- The convection cell --- p.16 / Chapter 2.2 --- The thermistors --- p.20 / Chapter 2.2.1 --- Calibration --- p.20 / Chapter 2.3 --- The multimeter --- p.21 / Chapter 2.4 --- Thermostat box --- p.22 / Chapter 2.5 --- Visualization --- p.23 / Chapter 2.6 --- Motorized translation stage --- p.24 / Chapter 2.7 --- AC Wheatstone Bridge and Lock in amplifier --- p.24 / Chapter 2.8 --- Test different heaters --- p.26 / Chapter III --- "Heat flux, boundary layer and Reynolds number measurement of one-layer FC77 thermal convection" --- p.30 / Chapter 3.1 --- Heat flux measurement with correction --- p.30 / Chapter 3.1.1 --- Sidewall correction --- p.31 / Chapter 3.1.2 --- Bottom plate correction --- p.31 / Chapter 3.1.3 --- Post correction --- p.31 / Chapter 3.2 --- The Nu result --- p.32 / Chapter 3.3 --- Boundary layer measurement --- p.34 / Chapter 3.4 --- The Pr dependence of the Reynolds number Re --- p.37 / Chapter 3.5 --- Summary --- p.40 / Chapter IV --- "Heat transfer, thermal boundary layer and flow property measurement of multilayer immiscible fluid turbulent thermal convection" --- p.41 / Chapter 4.1 --- Introduction --- p.41 / Chapter 4.2 --- Experiment --- p.44 / Chapter 4.3 --- The temperature and temperature fluctuation across the interface --- p.46 / Chapter 4.3.1 --- The temperature near the interface --- p.46 / Chapter 4.3.2 --- Position and temperature of the interface --- p.47 / Chapter (a) --- Using the profile to get the temperature of the interface --- p.47 / Chapter (b) --- Using the traveling microscope to get the absolute position of the interface --- p.50 / Chapter 4.4 --- The Nu result --- p.50 / Chapter 4.5 --- Boundary layer thickness and scaling --- p.54 / Chapter 4.6 --- Statistical properties of the temperature field across the interface --- p.58 / Chapter 4.6.1 --- Temperature time series and the corresponding histogram of the interface --- p.58 / Chapter 4.6.2 --- "The mean, root mean square, skewness, time derivative skewness and flatness of the temperature profiles across the interface" --- p.64 / Chapter 4.6.3 --- Scaling of the temperature fluctuation in two-layer system --- p.71 / Chapter 4.7 --- The temperature oscillation --- p.74 / Chapter 4.8 --- Passive scalar and active scalar --- p.77 / Chapter 4.9 --- Summary --- p.79 / Chapter V --- Conclusion --- p.80 / Chapter 5.1 --- One-layer thermal convection --- p.80 / Chapter 5.2 --- Two-layer thermal convection --- p.80 / Chapter 5.3 --- Future works --- p.81 / References --- p.82

Ren Liyuan = 小寬高比熱對流中高精度Nusselt數和局部溫度測量 / 任立元. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 64-66). / Text in English; abstracts in English and Chinese. / Ren Liyuan = Xiao kuan gao bi re dui liu zhong gao jing du Nusselt shu he ju bu wen du ce liang / Ren Liyuan. / Abstract (in English) --- p.i / Abstract (in Chinese) --- p.ii / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vi / List of Tables --- p.ix / Chapters / Chapter I. --- Turbulent Rayleigh-Benard Convection --- p.1 / Chapter 1.1 --- Introduction of Rayleigh-Benard Convection --- p.1 / Chapter 1.2 --- The Convection Equations --- p.2 / Chapter 1.3 --- The parameters --- p.3 / Chapter 1.4 --- Background --- p.5 / Chapter 1.5 --- Synopsis of this thesis --- p.8 / Chapter II. --- Experimental Setup and Methods --- p.9 / Chapter 2.1 --- The Apparatus --- p.9 / Chapter 2.2 --- Thermistor Calibration --- p.12 / Chapter III. --- Local temperature measurements --- p.19 / Chapter 3.1 --- Introduction and motivation --- p.19 / Chapter 3.2 --- Local temperature measurements --- p.20 / Chapter 3.3 --- Temperature time series and histograms --- p.20 / Chapter 3.4 --- Mean temperature profile --- p.24 / Chapter 3.5 --- Summery --- p.35 / Chapter 3.6 --- Appendix A: Data lists for this chapter --- p.36 / Chapter IV --- Heat transport measurement --- p.39 / Chapter 4.1 --- Introduction and Motivation --- p.39 / Chapter 4.2 --- Heat transfer measurements --- p.40 / Chapter 4.3 --- Experimental uncertainties associated with high-precision measurements of Nu --- p.41 / Chapter 4.3.1 --- Cell height measurement --- p.41 / Chapter 4.3.2 --- Temperature measurement --- p.41 / Chapter 4.3.3 --- Thermal source --- p.41 / Chapter 4.3.4 --- Thermal leakage --- p.42 / Chapter 4.3.5 --- Sidewalleffect --- p.44 / Chapter 4.3.6 --- Long time measurement --- p.44 / Chapter 4.4 --- Results and discussion --- p.45 / Chapter 4.4.1 --- Experimental data --- p.45 / Chapter 4.4.2 --- Finite conductivity effect --- p.47 / Chapter 4.4.3 --- Nu dependence on Г --- p.49 / Chapter 4.4.4 --- Nu dependence on Ra --- p.50 / Chapter 4.5 --- Summary --- p.53 / Chapter 4.6 --- Appendix B: Data lists for this chapter --- p.54 / Chapter V. --- Conclusions --- p.62 / References --- p.64

Critical Heat Flux (CHF) is an important safety parameter for the design of nuclear reactors. The most commonly used predictive tool for determination of CHF is a look-up table developed using tube data with an average hydraulic test diameter of 8 mm. There exist in the world today nuclear reactors whose geometry is annular, not tubular, and whose hydraulic diameter is significantly smaller than 8 mm. In addition, any sub-channel thermal hydraulic model of fuel assemblies is annular and not tubular. Comparisons were made between this predictive tool and annular correlations developed from test data. These comparisons showed the look-up table over-predicts the CHF values for annular channels, thus questioning its ability to perform correct safety evaluations. Since no better tool exists to predict CHF for annular geometry, an effort was undertaken to produce one. A database of open literature annular CHF values was created as a basis for this new tool. By compiling information from eighteen sources and requiring that the data be inner wall, unilaterally, uniformly heated with no spacers or heat transfer enhancement devices, a database of 1630 experimental values was produced. After a review of the data in the database, a new look-up table was created. A look-up table provides localized control of the prediction to overcome sparseness of data. Using Shepard's Method as the extrapolation technique, a regular mesh look-up table was produced using four main variables: pressure, quality, mass flux, and hydraulic diameter. The root mean square error of this look-up table was found to be 0.8267. However, by fixing the hydraulic diameter locations to the database values, the root mean square error was further reduced to 0.2816. This look-up table can now predict CHF values for annular channels over a wide range of fluid conditions. / Graduation date: 2001

Current research shows that pulse combustion impingement drying is an improvement over the steady impingement drying currently in commercial use. Pulse combustion impingement has higher heat transfer rates and a lower impact on the environment. Commercialization of pulse impingement drying is the goal of the Pulsed Air Drying group at IPST. To that end the objective of this project is to develop a system that will allow researchers to measure heat transfer rates at the impingement surface from the impinging air. A water cooled impingement plate with temperature and heat flux measuring capabilities was developed which accurately measures and records the desired information. The impingement plate was tested and its results were verified by comparison with previous literature. Finally a preliminary comparison between steady and pulse combustion impingement was carried out. The study shows pulsed combustion impingement to be superior to steady impingement.