Browsing by Subject "thermal"
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Item Analytical Models for Flowing-Fluid Temperature Distribution in Single-Phase Oil Reservoirs Accounting for Joule-Thomson Effect(2014-11-13) Chevarunotai, NatashaModern downhole temperature measurements indicate that bottomhole fluid temperature could be significantly higher or lower than the original reservoir temperature, especially in ?more challenging? low-permeability reservoirs, where high pressure drawdown is expected during production. This recent finding contradicts the isothermal assumption originally made for typical conventional reservoirs. In a high- pressure drawdown environment, Joule-Thomson (J-T) phenomenon plays an important role in fluid temperature alteration in the reservoir. In this study, we developed a robust analytical model to estimate the flowing-fluid-temperature distribution in the reservoir accounting for J-T heating or cooling effect. All significant heat-transfer mechanisms for fluid flow in the reservoir, including heat transfer due to conduction, convection, and heat transfer from over- and -under-burden formations to the reservoir, as well as temperature change due to J-T phenomena, are incorporated in this study. The proposed model is successfully validated with results from a rigorous numerical simulator using field data. In general, a more accurate flowing-fluid temperature calculation leads to better estimates of well productivity index, which is one of the key parameters in production optimization and field development planning. Sensitivity analysis results show that production rate, reservoir permeability, fluid viscosity, and J-T coefficient are critical parameters in reservoir flowing-fluid temperature calculation. Findings from the sensitivity analysis allow us to make a decision whether or not to acquire more data or to perform additional tests for a more reasonable outcome- the flowing-fluid temperature in the reservoir. Bottomhole flowing-fluid temperature from the proposed analytical model can be further coupled with wellbore heat-transfer model to allow prediction of flowing-fluid temperature along the wellbore up to surface. The flowing-fluid temperature profile along the wellbore is normally very useful for well design and production optimization in production engineering, as well as for pressure-transient analysis.Item Computational Nuclear Forensics Analysis of Weapons-grade Plutonium Separated from Fuel Irradiated in a Thermal Reactor(2014-04-27) Coles, Taylor MarieThe objective of this thesis work is to utilize computational models to reliably predict the intrinsic signature of the weapons-grade plutonium separated from a Pressurized Heavy Water Reactor (PHWR), specifically an Indian 220 MWe PHWR. The PHWR produced weapons-grade plutonium due to the low-burnup seen by the fuel in the computational model. The computational modeling for this project was completed using MCNPX-2.7 radiation transport code. MCNPX-2.7 was used to perform burnup calculations for the PHWR in able to determine the resulting isotopic makeup of actinides and trace elements found in the discharged fuel. The discharged fuel of interest was a single bundle of natural uranium fuel which had undergone a burnup of about 1 GWd/tU. During the PHWR core burnup simulation, certain fuel channels were reshuffled and replaced with a number of new or "fresh" fuel bundles to simulate the process of refueling the reactor; however, it was later determined that utilizing a computational model of a single bundle with reflective boundary conditions on all sides was sufficient in producing the necessary data. That single bundle was burnt to the desired burnup and the final fuel composition of that bundle was used in the isotopic analysis. The specific fission products and actinides selected for this analysis were chosen based upon five parameters; the amount of production, half-life, activity, probability of detection, and the Plutonium Uranium Extraction Process (PUREX) decontamination factor. An uncertainty analysis associated with Monte Carlo methodology was completed using the computational model to predict the mean and standard deviation of the amount of production from the PHWR. Ratios of the selected isotopes concentrations and activities per 1 Kg of total plutonium with a decontamination factor of 106 were calculated for the PHWR. The intrinsic signature of the PHWR was also compared to that from a Fast Breeder Reactor (FBR), and a ratio of the PHWR results to the FBR results was completed to determine if noticeable differences could be seen between the two reactor types, hence, proving the existence of identifyable intrinsic physical signatures in separated weapons-grade plutonium produced by differing reactor types. Ultimately, if smuggled weapons-grade plutonium is intercepted, an analysis of isotopic signatures would be able to attribute the material back to a source reactor. The future work would include experimental data collected after single fuel pellets of natural uranium fuel have been irradiated to the desired burnup in the Oak Ridge National Laboratory- High Flux Isotope Reactor (ORNL-HFIR), and then separated using the PUREX process to experimentally determine the intrinsic signature of the fuel. The experimental data is not yet available.Item Optimization of the configuration and working fluid for a micro heat pipe thermal control device(Texas A&M University, 2006-04-12) Coughlin, Scott JosephContinued development of highly compact and powerful electronic components has led to the need for a simple and effective method for controlling the thermal characteristics of these devices. One proposed method for thermal control involves the use of a micro heat pipe system containing a working fluid with physical properties having been speciffcally selected such that the heat pipes, as a whole, vary in effective thermal conductance, thereby providing a level of temperature regulation. To further explore this possibility, a design scenario with appropriate constraints was established and a model developed to solve for the effective thermal conductance of individual heat pipes as a function of evaporator-end temperature. From the results of this analysis, several working fluids were identified and selected from a list over thirteen hundred that were initially analyzed. Next, a thermal circuit model was developed that translated the individual heat pipe operating characteristics into the system as a whole to determine the system level effects. It was found that none of the prospective fluids could completely satisfy the established design requirements to regulate the device temperature over the entire range of operating conditions. This failure to fully satisfy design requirements was due, in large part, to the highly constrained nature of problem definition. Several fluids, however, did provide for an improved level of thermal control when compared to the unmodified design. Suggestions for improvements that may lead to enhanced levels of thermal control are offered as well as areas that are in need of further research.Item Thermal signature reduction through liquid nitrogen and water injection(Texas A&M University, 2005-02-17) Guarnieri, Jason AntonioThe protection of aircraft against shoulder fired heat seeking missiles is of growing concern in the aviation community. This thesis presents a simple method for shielding the infrared signature of a jet engine from heat seeking missiles. The research efforts investigated two approaches to shield the thermal signature of the Noel Penny Type 401 turbojet at the Texas A&M University Propulsion Lab Test Cell. First, liquid nitrogen was injected through a manifold at a flow rate equivalent to the flow rate of exhaust gases, producing a small temperature reduction in the exhaust but no infrared shielding. Second, water was injected at a flow rate of 13% of the flow of exhaust gases, producing a greater temperature reduction and some shielding. Water was then injected through a manifold at a ?ow rate of 118% of the flow rate of exhaust gases, producing a substantial reduction in temperature and complete shielding of the infrared signature. Additionally, numerical simulations were performed using FLUENT to support these experiments. Results are presented in the form of thermocouple data and thermal images from the experiments, and in the form of temperature contours and streamtraces from the simulations.