Now showing items 41-60 of 72

    • Thermal and fluid dynamic analysis of gas-to-liquids transportation through Trans Alaska Pipeline System

      Nerella, Sirisha (2002-08)
      Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this study, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations.
    • Steam reformation of diesel fuels

      Neogi, Bhaskar (2002-05)
      The Remote Area Program was created to evaluate the possible use of fuel cells and diesel reformers in residential and off-grid applications. Diesel was chose because an infrastructure already exits in rural communities. The UAF Energy Center demonstrated the use of a reformer to convert kerosene into hydrogen, which was used in a Proton Exchange Membrane fuel cell to power an AC load. In the summer of 1999, UAF hosted an Energy conference. At the conference Northwest Power (reformer manufacturer) indicated a diesel reformer efficiency of 65% while Plug Power promised a system efficiency (reformer, fuel cell and inverter) of 40%. After extensive experiments, the Energy Center found the current design reformer efficiency to be 30% and the system efficiency to be 15% at best. This efficiency does not compare favorably to the currently available diesel generator efficiency of 33%.
    • Order reduction and eigenstructure assignment for nonsmooth vibrating systems: a nonlinear normal modes approach

      Lu, Rongdong (2002-08)
      Two related problems are addressed in this thesis. The first one is for order reduction of conservative vibrating systems with piecewise linear nonsmooth nonlinearities of arbitrary dimension. Linear-based, PMM-based and LELSM-based order reduction transformations are applied. The technique is applied to multi-degree-of-freedom systems with nonsmooth clearance, deadzone, bang-bang, and saturation nonlinearities. The resulting approximate frequencies are compared with those obtained from numerical simulations. The second technique is eigenstructure assignment of n-degree-of-freedom conservative vibrating systems with nonsmooth nonlinearities. Three distinct control strategies which utilize methods for approximating the NNM frequencies and mode shapes are employed. First, PMM for approximating NNM frequencies is used to determine n constant actuator gains for eigenvalue placement. Second, an approximate single-degree-of-freedom reduced model is found with one actuator gain for the mode to be controlled. The third strategy allows the frequencies and mode shapes (eigenstructure) to be placed by using a full n x n matrix of actuator gains and employing LELSM for approximating NNM frequencies and mode shapes.
    • Properties and performance evaluation of syntroleum synthetic diesel fuels

      Sastry, Kanthikiran (2005-12)
      Synthetic fuels derived from natural gas or coal have been proposed as a replacement for the diminishing stock of fuels distilled from crude oil, and in addition offer significant environmental benefits. Fuels of this type are currently being produced and tested for their compatibility with existing diesel engines. This study examines the physical properties of the Syntroleum synthetic fuel produced by Syntroleum Corporation of Tulsa, OK, and its performance and energy balance in a Detroit Diesel series 50 engine generator. This is a high cetane fuel that contains predominately paraffins, and is essentially free of sulfur, olefins, metals, aromatics or alcohols. This work includes measuring physical properties: lubricity, density, cloud point, and heating value. Also discussed is the thermodynamic energy flow in a diesel generator system to determine what effect the new fuel has on electrical and heat production. In addition to the investigation of synthetic fuel, a similar kind of study was also performed on bio-diesel produced from fish oil.
    • Corrosion behavior of microarc oxidation and polycaprolactone coatings applied to AZ31 magnesium alloy evaluated in simulated body fluid and balanced salt solution

      Wilke, Benjamin M.; Zhang, Lei; Peterson, Rorik; Zhang, Junqing; Chen, Cheng-fu (2015-08)
      Recent research in orthopedic implant materials has focused on the use of magnesium alloys as a base material due to its mechanical properties similar to that of human bone. Rapid corrosion of magnesium materials in aqueous environments poses a significant hurdle to their application as a biomedical implant. A variety of coatings have been shown to improve the corrosion resistance of magnesium based materials in simulated body fluid environments including microarc oxidation and polymer coatings. However, formulation and corrosion rates vary significantly between solution types. Furthermore, in vivo results have shown that many common in vitro solutions over estimate corrosion rates. In addition to variations between solutions needing to be resolved, there has been little work performed to characterize large sample corrosion under stress. This is an essential step in evaluating concept performance at a macro scale, for application as a human implant. The experiments performed and presented in this thesis primarily involve the comparison of conventional simulated body fluid (c-SBF) and Earle's balanced salt solution (EBSS). Samples evaluated in these environments are microarc oxidation (MAO) coated AZ31 magnesium alloy and polycaprolactone dip-coated AZ31. MAO coated samples were created for a range of process settings to observe the effect of processing on corrosion performance. A dependence of MAO coating thickness on process voltage was found which augmented the initial corrosion resistance values observed via electrochemical testing. Both MAO and PCL coatings were found to improve the corrosion resistance of the samples as compared to uncoated AZ31. It was found that all variations (MAO, PCL, and uncoated) showed a reduced corrosion rate in EBSS as compared to c-SBF. This corrosion reduction was apparent through potentiodynamic scanning, electrochemical impedance spectroscopy, and visual inspection. Preliminary mechanical corrosion results, in the form of constant extension testing, showed no dependence of corrosion on stress level. Future work may be aimed towards expanding modes of mechanical testing and further refining simulated body fluids to fit with in vivo test results.
    • Stability of milling using Chebyshev collocation method

      Nindujarla, Praveen (2004-12)
      The dynamic stability of the milling process is investigated through single and two degree-of-freedom mechanical models by determining the regions where chatter (unstable) vibrations occur in the two-parameter space of spindle speed and depth of cut. Dynamic systems like milling are modeled by linear delay-differential equations (DDEs) with time-periodic coefficients. A new approximation technique for studying the stability properties of such systems is presented in this thesis. The approach is based on the properties of Chebyshev polynomials and a collocation expansion of the solution at their extremum points, the Chebyshev collocation points. The stability properties are determined by the eigenvalues of the monodromy matrix which maps collocation points from one interval to the next and which is a finite dimensional approximation to which the exact infinite dimensional Floquet transition matrix (monodromy operator). We check the results for convergence by varying the number of Chebyshev collocation points and by simulation of the transient response via the DDE23 MATLAB routine. Stability charts and chatter frequency diagrams are produced for up-milling and down-milling cases of 1, 2, 4 and 8 cutting teeth and 0 to 100 % immersion levels. The unstable regions due to both secondary Hopf and flip (period-doubling) bifurcations are found which agree with the results found by other techniques in the previous literature. An in-depth investigation in the vicinity of the critical immersion ratio for down-milling (where the average cutting force changes from negative to positive) and its implication for stability is presented.
    • Predictive semi-empirical analysis for tire/snow interaction

      Sankapalli, Naveen Kumar; Lin, Chuen-Sen; Liu, Qing; Zhang, Tinggang; Lee, Jonah (2004-12)
      A semi-analytical method is presented to predict the shear stress and motion resistance at the tire/snow interaction. The shear stress model is a function of normal pressure and slip. The main goal was to develop a simplified model by reducing the number of parameters in the model, so that the computational time could be reduced towards real time simulations. Motion resistance is calculated by integrating the horizontal component of normal pressure along the tire/terrain contact surface. The motion resistance obtained is slip dependent because the sinkage is a function of slip. The calculations of motion resistance and sinkage were done using the presented model and an existing model. Also the calculated results were compared with the FEA (Finite Element Analysis) data, which matched reasonably well. In the second part of the thesis shear force is expressed as a function of normal load, slip and slip angle. Shear force parameters tire stiffness, friction coefficients, and contact pressure constants were assumed as the functions of normal load and the coefficients of parameters were found through curve fitting using FEA data. These functions were used to calculate tire stiffness, friction coefficient and contact pressure constant. The calculated results matched well with FEA simulation results for the same tire and snow conditions. Pure shear force and the combined shear force were compared, and the pure shear force is always greater than the combined shear force for the same slip and slip angle.
    • Experiments on the interactions between a rigid plate and vortices

      Milke, Shaun; Peterson, Rorik; Peng, Jifeng; Xiang, Yujiang (2015-08)
      This study provides a quantitative analysis, and subsequent comparison, of flow field behavior under varied experimental parameters for vortex production by, and vortex ring interaction with, a rigid plate. The relationship between the experimental parameters: flapping amplitude and average rotational speed, and flow field characteristics: vorticity, circulation, total kinetic energy, and vortex trajectory, were examined for the cantilevered plate. The relationships between the parameter of plate inclination and the flow field characteristics of vorticity, circulation, and vortex trajectory, were examined for the inclined plate. All experiments involved a particle image velocimetry (PIV) analysis followed by processing of the data to produce quantified flow field data. The cantilevered plate experiments revealed that a flapping cantilevered plate produces two primary vortices: a tip vortex and a plate hugging vortex, and in some cases a stopping vortex above the tip. It was determined that the maximum magnitudes attained, the accumulation rate, and the dissipation rate of both circulation and kinetic energy are speed dependent. However, rate of accumulation and dissipation of either quantity does not vary with total flapping amplitude. It was concluded that flapping amplitude does not influence the shape of vortex trajectory or the trajectory angle relative to the horizontal, though the total distance traveled along the vortex trajectory is dependent on flapping amplitude. In the case of the inclined plate, it was concluded that the levels of vorticity, particularly in the lower part of the vortex ring, and the formation of additional vortices in the flow field are dependent on plate inclination and thus, the degree of asymmetry of the interaction. During the die off phase the circulation of the upper part of the vortex ring is inversely proportional to plate angle, while circulation of the lower part of the vortex ring is proportional to plate inclination. The relationship between plate inclination and vertical displacement of the two parts of the ring was found to be based on the degree of asymmetry.
    • Evaluation and parametric modeling of 50 kW organic rankine cycle for waste heat recovery from rural Alaska diesel generator power plants

      Avadhanula, Vamshi Krishna; Lin, Chuen-Sen; Das, Debendra K.; Bargar, Harold E.; Kim, Sunwoo (2015-08)
      In rural Alaska, there are about 180 villages that run independent electrical power systems using diesel generator sets. A diesel engine generator loses fuel energy in the form of waste heat through the charge air cooler (after cooler), the jacket water cooler, friction, and exhaust. Diesel engine jacket water and exhaust account for about 20% and 30% of the total fuel energy, respectively. In previous studies it has been demonstrated that about 80% of the heat present in jacket water and 50% of the heat from exhaust gases can be recovered for useful purposes such as heating, power generation, refrigeration, and desalination. In this study, the diesel engine waste heat application selected was power generation using an organic Rankine cycle (ORC) heat engine. The basic principle of an ORC system is similar to that of the traditional steam Rankine cycle; the only difference is the working fluid. The working fluids generally used in an ORC are refrigerants, such as R11, R113, R123, R134a, R245fa, and HFE-7000. The working fluid in the ORC system under study is R245fa. A typical ORC consists of a pump, preheater, evaporator, expansion machine (expander), and condenser. The working fluid is pressurized through the pump and supplied to the preheater and evaporator, where it is heated by the heat source. The working fluid exits the evaporator as vapor or liquid/vapor. It expands in the expander, generating power. The low-pressure working fluid exiting the expansion machine is liquefied in the condenser by a cooling source, returned to the pump, and the cycle repeats. At the University of Alaska Fairbanks (UAF) power plant, a lab experimental setup was designed: a hot water loop (heat source) and cold water loop (heat sink) for testing the 50 kW ORC power unit. Different diesel engine waste heat recovery conditions were simulated to study the unit's reliability and performance. After lab testing, the ORC system was installed permanently on a 2 MW Caterpillar diesel engine for jacket water heat recovery in Tok, Alaska, and tested further. These two tests provide for the goals of the present dissertation which are: (i) testing of a 50 kW ORC system for different heat source and heat sink supply conditions, (ii) develop guidelines on applying the present 50 kW ORC system for individual rural Alaska diesel gen-sets, (iii) develop empirical models for the screw expander, (iv) develop heat transfer correlations for single-phase and two-phase evaporation, and two-phase condensation for refrigerant R245fa in the preheater, evaporator and condenser, respectively, and (v) parametric modeling and validation of the present ORC system using the empirical correlations developed for a screw expander and R245fa in heat exchangers to predict the performance of the ORC system for individual diesel generator sets. The lab experimental data were used to plot performance maps for the power unit. These maps were plotted with respect to hot water supply temperature for different ORC parameters, such as heat input to power unit in evaporator and preheater, heat rejection by power unit in condenser, operating power output, payback period, and emissions. An example of how performance maps can be used is included in this dissertation. As detailed in this dissertation, the resulting lab experimental data were used to develop guidelines for independent diesel power plant personnel installing this ORC power unit. The factors influencing selection of a waste heat recovery application (heating or power) are also discussed. A procedure to find a match between the ORC system and any rural diesel generator set is presented. Based on annual electrical load information published in Power Cost Equalization data for individual villages, a list of villages where this ORC system could potentially be beneficial is included. During lab work at the UAF power plant, experimental data were also collected on the refrigerant side (R245fa) of the ORC system. Inlet and outlet pressures and temperatures of each component (evaporator, pump, and expander) of the ORC were measured. Two empirical models to predict screw expander power output were developed. The first model was based on polytropic work output, and the second was based on isentropic work output. Both models predicted screw expander power output within ±10% error limits. Experimental data pertaining to the preheater, evaporator, and condenser were used to develop R245fa heat transfer correlations for single-phase and two-phase evaporation and two-phase condensation in respective heat exchangers. For this study the preheater, evaporator, and condenser were brazed plate heat exchangers (BPHEs). For single-phase heat transfer in the preheater, a Dittus-Boelter type of correlation was developed for R245fa and hot water. For R245fa evaporation in the evaporator, two heat transfer correlations were proposed based on two-phase equation formats given in the literature. For condensation of R245fa in the condenser, one heat transfer correlation was proposed based on a format given in the literature. All the proposed heat transfer correlations were observed to have good agreement with experimental data. Finally, an ORC parametric model for predicting power unit performance (such as power output, heat input, and heat rejection) was developed using the screw expander model and proposed heat transfer correlations for R245fa in heat exchangers. The inputs for the parametric model are heating fluid supply conditions (flow rate and temperature) and cooling fluid supply conditions, generally the only information available in rural Alaska power plant locations. The developed ORC parametric model was validated using both lab experimental data and field installation data. Validation has shown that the ORC computation model is acceptable for predicting ORC performance for different individual diesel gen-sets.
    • Testing of syntroleum fuels in diesel power plants suitable for Alaska

      Telang, Aseem Uday (2005-05)
      Sulfur free synthetic diesel fuels can be produced using Gas to Liquid (GTL) technology, and may prove useful as a substitute for conventional diesel fuels when oil reserves are depleted. These fuels also should produce lower emissions, as the sulfur content is near zero. However, this fuel has significantly different combustion properties than conventional diesel fuels, and may require injection timing adjustments to burn cleanly. This paper presents a comparison of the exhaust emissions from synthetic diesel fuels, manufactured by the Syntroleum Corporation, and conventional diesel fuel. Documented emissions are the total hydrocarbons, carbon monoxide and oxides of nitrogen. Effects of injection timing on exhaust emission and brake specific fuel consumption (BSFC) are also discussed.
    • A case/control analysis and comparison of indoor air quality in Alaskan homes

      Dinakaran, Satish; Johnson, Ron; Naidu, Sathy; Lin, Chuen-Sen; Seifert, Rich (2005-08)
      Indoor Air Quality (IAQ) parameters such as CO, CO₂, relative humidity, temperature, radon, particulate matter, formaldehyde, benzene, toluene, hexane, Total Volatile Organic Compounds (TVOC) and microbial matter were monitored before and after remediation in 36 low-income homes in Alaska (Hooper Bay and Fairbanks). The objective was to see if there was any improvement in IAQ with remediation. Hooper Bay homes had significantly higher levels of CO₂ and relative humidity compared to Fairbanks homes both before and after remediation. There was a general reduction in CO₂ with remediation, although it was not statistically significant. When IAQ in two moderate-income homes in Fairbanks was compared with that in the remediated low-income homes, it was observed that indoor CO₂ levels were affected by ventilation rates and per capita floor area. A single zone model to predict concentration of indoor pollutants was constructed, using steady state and transient mass conservation, to predict, metabolically produced CO₂, and particulate matter when no indoor sources were present. The cost of energy to reduce indoor CO₂ levels in one of the homes by increasing ventilation by either using an exhaust-only system or a Heat Recovery Ventilator (HRV) is discussed.
    • Influence of underfill filler settling on the thermomechanical reliability of the flip chip on board package

      Thammadi, Navin; Chen, Cheng-fu; Lin, Chuen-Sen; Lee, Jonah (2005-08)
      A Flip Chip on Board package (FCOB) is analyzed under thermal cycling loading to study the effect of underfill filler settling on the thermo-mechanical reliability of the package. The Mori-Tanaka method, a micromechanics based formulation, is utilized to model the property gradation caused by filler settling to obtain the effective material model for underfill. The modeling of the underfill material depends on the filler settling assumed. A total of five different underfill material models are used to assess their impact on the reliability. The equivalent underfill material properties calculated are subsequently used in finite element simulations to evaluate the FCOB assembly reliability. The reliability issues investigated in this work are solder joint fatigue and die cracking. This work aims to predict solder joint fatigue lifetime and also determine an acceptable pre-existing flaw size in the die backside to prevent die cracking. The results show that, when the underfill filler settling is gradual (instead of homogeneous), the corresponding solder joint has the minimum fatigue lifetime among the models assessed. However, the filler settling configuration has very little influence on the critical flaw size in the die and the board warpage.
    • Axisymmetric numerical heat transfer analysis of natural gas hydrates reservoir

      Subbaihaannadurai, Vijayagandeeban; Das, Debendra K.; Patil, Shirish L.; Goering, Douglas J. (2004-12)
      Gas hydrates are crystalline substances, occurring in nature under high pressure and low temperature. Numerical studies were conducted on dissociation of gas hydrate to recover natural gas. The model is a cylindrical geometry with a wellbore at the center through which hot water is injected. Through this thermal stimulation technique frozen hydrate reservoir is melted and natural gas is released. The computational fluid dynamics software FLUENT was adopted to generate the model. The initial model was solely comprised of a hydrate layer. This model was refined by adding the overburden and the underburden to the hydrate and exploring the thermal regime of the entire composite medium. Unsteady state results showing the dissociation front propagation with respect to time were calculated. In the first part, the hydrate medium is dissociated by the conduction phenomenon only. In the second part, due to the porous nature of the hydrate medium, both conduction and convection phenomena are considered. This thesis presents the following results obtained from simulations using Fluent. They are: temperature rise within the reservoir with time, temperature profiles in the radial direction, and steady and transient state solutions of the dissociation of gas hydrate with the liquid fraction in the reservoir. Comparison of our results with a finite difference model and a finite element model is also included. Volumes of gas released with respect to time and thermal efficiency ratios are also determined.
    • Aerodynamic heating of the student rocket project-5 sounding rocket

      Mudunuri, Venkata; Goering, Douglas; Das, Debendra K.; Hawkins, Joseph (2005-05)
      This thesis deals with the calculation of the flow properties and heat transfer around the rocket nose cone for Student Rocket Project-5 (SRP-5). Governing differential equations are presented for this purpose, giving the fundamental relations between the skin temperature and flight history. The determination of all the required parameters in the equations is discussed, and the Runge-Kutta numerical method of integration is used to obtain the solution. A model to implement the above equations to predict skin temperature for the given trajectory was built in SIMULINK®. Individual sub-systems of the SIMULINK® model are used to calculate local tree-stream values, Reynolds number, heat absorption capacity and skin friction coefficient. The SIMULINK® model was used to predict the variation of the skin temperature for the SRP-5 flight trajectory. The simulation results also show comparisons of the different subsystem outputs with data provided by the contractor for the NASA Sounding Rocket Contract (NSROC).
    • Synthesis and investigation of properties of barium titanate doped with ferromagnetic materials for use in spin field effect transistors

      Kulkarni, Kapildev (2004-05)
      The fundamental aspect of this research was to synthesize nano particles of certain materials and to investigate their properties related to potential use in spin-field effect transistor (Spin-FET). Barium titanate was doped with ferromagnetic material and nano particles of this material were synthesized using a sol-gel process. Sol-gels were characterized for their size and shape using an atomic force microscope and a scanning electron microscope. Composition of these compounds and the distribution of dopents were investigated using x-ray fluorescence and the scanning electron microscope. Dielectric properties were measured using high precision impedance, capacitance, and resistance (LCR) meter. Barium titanate, when doped with ferromagnetic materials, becomes ferroelectric material. Ferroelectric materials have finite polarization even in the absence of an applied electric field, which can be exploited for their use as source/drain in spin-FET. The sintering temperature and pH of the sol-gel solution play important roles in determining the dielectric constants, particle size and distribution of dopent in barium titanate. It was found that iron has advantage over nickel and cobalt as a dopent, as it has high electrical susceptibility.
    • Analysis of a generic flip chip under shock and vibration

      Kasturi, Uday Bhaskar; Chen, Cheng-fu; Butcher, Eric; Lin, Chuen-Sen (2004-12)
      A flip chip package, underfilled or non-underfilled, was analyzed under mechanical shock and/or vibration at the device and board levels, respectively. For the tests at the device level, the maximum stress developed at the corner-most solder joint. The horizontal drop orientation, with the chip facing up, produced the worst scenario for solder joint lifetime prediction. The underfilled package is better than non-underfilled under the excitation of mechanical shock and vibration. Parametric studies of the underfill material strength suggested that the higher the elastic modulus, the better it carried the mechanical shock. However, practically the upper bound of the elastic modulus is limited to avoid die cracking due to thermal mismatch of material expansion. The combined loading of thermal residual stress and mechanical shock was also conducted to study their influence on the solder lifetime prediction. It was found that the thermal pre-stressed condition plays a key role for the von Mises stress excursion, but has almost no influence on the shock-induced normal stress. The phenomenon appears similarly in the board level testing, but with worse reliability in solders due to the higher stresses induced.
    • Effects of electromigration on the reliability of radio frequency microelectro mechanical switches

      Karri, Naveen Kishore (2004-12)
      Radio Frequency (RF) Micro-Electro-Mechanical System (MEMS) switches have many advantages over semiconductor switches. Despite these advantages they are not implemented in reliability demanding space, defense and commercial applications because of reliability concerns. Although some failure modes have been identified so far, other failure modes are still under research. Electromigration, a well-known failure mechanism in interconnects, was recently recognized as a possible cause of failure in micro-switches. However, there have been no instances of electromigration studies in the literature. This thesis presents a preliminary study on the electromigration failure and its impact on the lifetime of MEMS switches. A simulation program that emulates the electromigration process was developed. Parametric studies were performed to study the impact of impact certain parameters on electromigration process. The combined effects of Joule heating and electromigration were analyzed. Unlike passivated interconnects, the micro-switch is cantilevered and suspended in an inert medium without encapsulation. The electromigration lifetime estimation program developed in this thesis is applicable to all such free structures. Joule heating has been demonstrated to be a key factor in the electromigration failure of micro-switches. Results showed that the electromigration process is very slow at the beginning. After a certain time, the resistance is found to increase exponentially, increasing the temperature of the strip drastically toward failure. The same trend is also observed in a gold micro-switch, but with much slower rate of electromigration degradation, indicating a longer lifetime.
    • Stochastic reconstruction of snow microstructure from x-ray microtomography images

      Yuan, Hongyan (2007-08)
      The three-dimensional (3D) high-resolution digitized snow microstructure (pixel size 6 micron) was obtained by X-ray microtomography. The experimental result was verified by measuring the density of the snow sample. Statistical characteristics (porosity, local porosity, two-point correlation function) were extracted from cross-sectional images. The one-level-cut Gaussian random field model was used to stochastically reconstruct snow microstructure from X-ray microtomography images. Efficient computer programs were developed in MATLAB for the whole stochastic reconstruction procedure, including the numerical inversion of the correlation function and the generation of 3D large-scale Gaussian random fields by 3D inverse fast Fourier transform. The quality of the reconstruction was assessed by comparing the two-point correlation function and cross-sectional images.
    • Performance analysis of capture of heat energy from diesel engine exhaust

      Raghupatruni, Prasada Rao (2007-08)
      Diesel generators produce electrical power. New diesel generators, which use turbochargers, release a significant amount of heat energy from the turbocharger after coolers. Another significant amount of heat energy released from diesel engines and normally not captured for useful applications is the heat released from exhaust manifolds. This project discusses the design, installation, instrumentation, performance measurement and performance analysis of an exhaust heat recovery system for a new diesel generator, which has injection timing control. A diesel generator releases about one-third of its fuel energy in exhaust heat. The main aspect of this project is to study heat recovery from the exhaust of a diesel generator for heating purposes. The amount of heat liberated from the exhaust can be used both for the space and floor heating. This project covers the work for the selection of a desired heat recovery system as well as an analysis of the results of the selected heat recovery system. The amount of heat recovered from the exhaust by the heat recovery system was 50% of the total amount of heat present in the exhaust. No corrosion spots were found on the heat exchanger during the heat recovery system run time.
    • Thermophysical properties measurements and numerical modeling of nanofluids

      Namburu, Praveen Krishna (2007-08)
      This thesis covers measurements of the thermo physical properties of various nanofluids containing copper oxide (CuO), silicon dioxide (SiO₂) and aluminum oxide (Al₂O₃) nanoparticles and numerical investigation on the fluid dynamic and heat transfer characteristics of nanofluids. Nanofluids are dispersions of nanometer-sized particles (<100 nm) in heat transfer liquids such as water, ethylene glycol or propylene glycol. An ethylene glycol and water (60:40 by mass) mixture was used as a base fluid in which various volume concentrations of nanofluids were dispersed. These nanofluids will be useful in the sub-arctic and arctic environments. Experiments were performed to investigate the rheological properties of CuO, SiO₂ and Al₂O₃ nanofluids. New viscosity correlations for different nanofluids as a function of volume concentration and temperature were developed. Using these correlations heat transfer performance of nanofluids as compared to the base fluid was numerically analyzed for laminar as well as for turbulent flows. Developing laminar flows in a parallel plate duct were computed for Reynolds number ranging from 100 to 2000 for various concentrations of CuO nanofluids. Turbulent convective heat transfer in circular tube geometry under a prescribed heat flux was numerically analyzed for Reynolds numbers ranging from 10⁴ to 10⁵. Heat transfer enhancement of various nanofluids over the base fluid was evaluated. The numerical results show enhanced heat transfer with increase in the volume concentration of nanoparticles.