Computations and experiments were run to study adiabatic effectiveness and thermal field contours for a simulated turbine blade leading edge. The RKE and SST k-[omega] turbulence models were used for the computational simulations. Predictions of RKE model for laterally averaged adiabatic effectiveness matched the experimental values. The computational simulations showed different flowfield for the coolant exiting the stagnation line row of holes. Both the experiments and SST k-[omega] simulations predicted coolant separation at the stagnation plane. Also, the downstream spreading of the coolant exiting the stagnation row of exit holes was better predicted by the SST k-[omega] model. At the stagnation plane, experimental thermal field measurements showed greater diffusion of the coolant into the mainstream than predicted by both turbulence models. Reasons for increased diffusion were examined. Thermal field comparison downstream of the offstagnation row of exit holes showed that the computational simulations and the experiments had the same general shape for the offstagnation coolant jet. But the computational simulations predicted greater diffusion of coolant in the direction normal to the surface than seen in the experiments. / text

Temperature dependent optical properties of lipid tissue verify critical information of tissue dynamics which can be applied to tissue treatment and diagnosis of various pathological features. Current methods of treating lipid rich tissues via heating are associated with post operation complications. Recent studies shows potential of lipid rich tissue removal by cooling. For monitoring cooling procedure and physical and chemical changes in lipid tissue, temperature dependent optical properties in subzero cooling need to be verified. This study designed heat transfer system estimating heat flux by cooling and programmed codes for image and data processing to obtain refractive indices of rodent subcutaneous lipid tissue. Phase transition of lipid tissue was observed and finally verified temperature dependent refractive index coefficient of lipid tissue from 24°C to -10°C. / text

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Water is abundant on earth and in the atmosphere and the most crucial liquid for life as we know it. It has been subject to rather intense research since more than a century and still holds secrets about its molecular structure and dynamics, particularly in the supercooled state, i. e. the metastable liquid below its melting point.  This thesis is concerned with different aspects of water and is written from a theoretical perspective. Simulation techniques are used to study structures and processes on the molecular level and to interpret experimental results. The evaporation kinetics of tiny water droplets is investigated in simulations with focus on the cooling process associated with evaporation. The temperature evolution of nanometer-sized droplets evaporating in vacuum is well described by the Knudsen theory of evaporation. The principle of evaporative cooling is used in experiments to rapidly cool water droplets to extremely low temperatures where water transforms into a highly structured low-density liquid in a continuous and accelerated fashion. For water at ambient conditions, a structural standard is established in form of a high precision radial distribution function as a result of x-ray diffraction experiments and simulations. Recent data even reveal intermediate range molecular correlations to distances of up to 17 Å in the bulk liquid. The barium fluoride (111) crystal surface has been suggested to be a template for ice formation because its surface lattice parameter almost coincides with that of the basal plane of hexagonal ice. Instead, water at the interface shows structural signatures of a high-density liquid at ambient and even at supercooled conditions. Inelastic neutron scattering experiments have shown a feature in the vibrational spectra of supercooled confined and protein hydration water which is connected to the so-called Boson peak of amorphous materials. We find a similar feature in simulations of bulk supercooled water and its emergence is associated with the transformation into a low-density liquid upon cooling. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.</p>

This study has focused on development, optimisation and implementation of the 2-line Planar Laser Induced Fluorescence (2-line PLIF) technique for combustion measurements on a single cylinder optical Gasoline Direct Injection (GDI) engine with both Spark Ignition (SI) and Controlled Auto Ignition (CAI) combustion operations. The CAI combustion was achieved by employing Negative Valve Overlap (NVO). Two excitation wavelengths at 308 nm (directly from a XeCl laser) and 277 nm (via Raman shifting a KrF laser output at 248 nm) were exploited for the measurements. A calibration curve of fluorescence signal intensity ratio of the two laser beams as a function of temperature was obtained by conducting a series of static tests on a specially designed Constant Volume Chamber (CVC). The developed technique was validated by measurements of in-cylinder charge temperature during the compression stroke for both motoring and firing cycles and comparing the PLIF values with the temperature values calculated from in-cylinder pressure data assuming a polytropic compression. Following the validation measurements, the technique was applied to study of fuel spray characteristics and simultaneous measurements of in-cylinder charge temperature and mole fraction of Exhaust Gas Residuals (EGR). Further optimisation of the thermometry technique by enhancing the fluorescence Signal to Noise Ratio (SNR) and improving both the temporal and spatial resolutions as well as measurements precision provided the opportunity to apply the technique to other combustion measurements. The thesis presents the first application of the 2-line PLIF diagnostic in study of direct injection charge cooling effects and study of flame thermal stratification in IC engines.

Liquid cooled small channel heat sinks have become a promising heat dissipation method for future high power electrical devices. Traditional mini and microchannel heat sinks consist of a single layer of low-aspect ratio rectangular channels. The alternative new heat sinks are fabricated by stacking many channels together to create multiple layer channels. These multilayer heat sinks can achieve high heat flux due to high heat transfer coefficients from small channels and large surface area from multilayer structure. In this research, multilayer copper and silicon carbide (SIC) minichannel heat sinks were tested in single-phase flow. It was shown that multilayer heat sinks have significant advantages over single-layer equivalents with reductions both in thermal resistance and pressure drop. A 3-D resistance network model for single and multilayered heat sinks was developed and validated. Parametric study and optimization on copper and SiC heat sinks with respect to channel geometries, number of layers, and heat sink conductivity were conducted by using the model.Both copper and SiC heat sinks were also tested in two-phase flow. In experiments, the multilayer copper heat sinks achieved smaller average surface temperature than their single-layer counterpart at low heat flux. However the multilayer copper heat sinks gradually lost stability at high heat flux, which lead to increased surface temperature. The redistribution of flow in different layers caused by pressure discrepancy in different layers was believed to be the cause. A three-zone model, which dividing the flow in small channels into three distinguishing parts: single-phase flow, subcooled boiling flow, and saturated boiling flow, was proposed to describe the different two-phase flow regimes. In each zone, the local heat transfer coefficient was computed by corresponding correlation. Several boiling correlations combined with the resistance network model were used to compute the heat sink surface temperature distributions, which were compared with experimental results. It was found the classical boiling correlations for macro channels are not suitable for the minichannels, frequently overestimating the boiling heat transfer coefficient. Boiling correlations for small channels are more consistent with experimental data and the predictions of Yu's correlation match the experimental results best.

Water availability is a common concern in semi-arid regions, such as Southern Arizona, USA. Hydroponic greenhouse crop production greatly reduces irrigation water use, but the study of water use by evaporative cooling has been limited.This project investigated water use by two evaporative cooling systems: pad-and-fan and high-pressure-fog with fan ventilation. All studies were performed in a double-layer polyethylene film-covered greenhouse (28 x 9.8 x 6.3 m) with mature tomato plants (2.9 plants m-2). Water use efficiency (WUE, kg yield per m3 water use) was calculated daily according to ventilation rate, as well as for a 6-month croppipng period, which used temperature-controlled pad-and-fan cooling.Pad-and-fan water use was 3.2, 6.4, 8.5, and 10.3 L m-2 d-1 for ventilation rates of 0.016, 0.034, 0.047, 0.061 m3 m-2 s-1, respectively. High-pressure-fog water use with a single central, overhead line was 7.9, 7.4, and 9.3 L m-2 d-1 for ventilation rates of 0.01, 0.016, 0.034 m3 m-2 s-1, respectively. For pad-and-fan ventilation rates less than 0.034 m3 m-2 s-1, total greenhouse WUE (20 - 33 kg m-3) was similar to field drip irrigation. For the temperature-controlled high-pressure-fog system, total greenhouse WUE (14 - 17 kg m-3) was similar to field sprinkler irrigation.For the 6-month crop cycle, combining water use by closed irrigation and pad-and-fan systems produced a total WUE of 15 kg m-3. Pad-and-fan WUE increased during monsoon conditions due to lower water use rates.Evaporative cooling water use and air temperature were well-predicted by the energy balance model. Predictions of air temperature improved when outside climate the measured conditions at one greenhouse location. Wind tunnel and full-scale studies of natural ventilation demonstrated the value of knowing airflow patterns when designing and operating a high-pressure-fog systemIt is possible for greenhouse tomato production to have a higher WUE than field production, if ventilation rates are not excessive, if closed irrigation is used, and if control methodologies are improved. Water use can be minimized by knowing how the evaporative cooling system affects greenhouse climate and plant responses.

The primary purpose of the current research was to implement a numerical model to investigate the interactions between the energy consumption in Heating, Ventilating, and Air Conditioning (HVAC) systems and occupants’ thermal comfort in commercial buildings. A numerical model was developed to perform a thermal analysis of a single zone and simultaneously investigate its occupants’ thermal sensations as a non-linear function of the thermal environmental (i.e. temperature, thermal radiation, humidity, and air speed) and personal factors (i.e. activity and clothing). The zone thermal analyses and thermal comfort calculations were carried out by applying the heat balance method and current thermal comfort standard (ASHRAE STANDARD 55-2004) respectively. The model was then validated and applied on a single generic zone, representing the perimeter office spaces of the Centre for Interactive Research on Sustainability (CIRS), to investigate the impacts of variation in occupants’ behaviors, building’s envelope, HVAC system, and climate on both energy consumption and thermal comfort. Regarding the large number of parameters involved, the initial summer and winter screening analyses were carried out to determine the measures that their impacts on the energy and/or thermal comfort were most significant. These analyses showed that, without any incremental cost, the energy consumption in both new and existing buildings may significantly be reduced with a broader range of setpoints, adaptive clothing for the occupants, and higher air exchange rate over the cooling season. The effects of these measures as well as their combination on the zone thermal performance were then studied in more detail with the whole year analyses. These analyses suggest that with the modest increase in the averaged occupants’ thermal dissatisfaction, the combination scenario can notably reduce the total annual energy consumption of the baseline zone. Considering the global warming and the life of a building, the impacts of climate change on the whole year modeling results were also investigated for the year 2050. According to these analyses, global warming reduced the energy consumption for both the baseline and combination scenario, thanks to the moderate and cold climate of Vancouver.

This thesis presents an experimental apparatus and methodology for measuring the interface conductance of thermal interface materials (TIMs) as a function of clamping pressure. The experimental apparatus is a steady state characterization device based on the basic premise presented in ASTM D5470 – 06. The setup is designed to develop an approximately one dimensional heat transfer through a TIM sample which is held between two meter bars. The temperature is measured along the meter bars using resistance temperature detectors (RTDs) and the temperature drop across the interface is extrapolated from these measurements and then used to calculate the conductance of the interface. This setup and methodology was used to characterize six commercial TIMs at pressures ranging from 0.17-2.76 MPa (25-400 psi). These TIMs included: Tgrease 880, Tflex 720, Tmate 2905c, Tpcm HP105, Cho-Therm 1671, and Cho-Therm T500. The measured conductance values for the various tests ranged from 0.19 to 5.7 W/cm2K. A three dimensional FEA model of the experimental setup was created in COMSOL Multiphysics 4.2a. This model was compared to the experimental data for a single data point and showed good correlation with the measured temperatures and conductance value.

No description available.