Mechanical Engineering Commons^™

Phase Transfer In A Collision Between A Droplet And Solid Spheres, Zheng Shen

Theses

The hydrodynamics of a liquid droplet impinging on a particle is of direct relevance to many engineering applications. The mechanism of heat and mass transfer during the droplet solid collision is essential to the design and operation of many industrial systems. However, very limited systemic research is available to describe the droplet impact on hot solid spheres.

This paper aims to establish a systematic investigation of phase transfer due to the droplet-solid impact, by both experimental and modeling approaches. The targeted phase transfer includes the surface attachment, mass of vaporization, heat transfer to droplet and its partition between vaporization and …

Flow Field And Heat Transfer Analyses Of Mechanical Seals, Zhaogao Luan

LSU Doctoral Dissertations

Mechanical seals are widely used in rotating equipment such as pumps, turbines and agitators to prevent leakage. One crucial factor for keeping seals reliable is the thermal behavior of the seal rings. The existing literature on thermal effects in seals primarily concentrates on the conduction of heat into the rings. Yet, a more complete analysis requires understanding of the flow field around the rings. In this dissertation, both the laminar and turbulent flows within the seal chamber are studied and their effects on the heat transfer in the seal rings are evaluated. Based on extensive sets of numerical simulations, heat …

Wall Heat Transfer Effects In The Endwall Region Behind A Reflected Shock Wave At Long Test Times, Corey Frazier

Electronic Theses and Dissertations

Shock-tube experiments are typically performed at high temperatures (≥1200K) due to test-time constraints. These test times are usually ~1 ms in duration and the source of this short, test-time constraint is loss of temperature due to heat transfer. At short test times, there is very little appreciable heat transfer between the hot gas and the cold walls of the shock tube and a high test temperature can be maintained. However, some experiments are using lower temperatures (approx. 800K) to achieve ignition and require much longer test times (up to 15 ms) to fully study the chemical kinetics and combustion chemistry …

Experimental Investigation Of Heat Transfer Rate In Micro-Channels, Pritish Ranjan Parida

LSU Master's Theses

Metal-based MHEs are of current interest due to the combination of high heat transfer performance and improved mechanical integrity. Efficient methods for fabrication and assembly of functional metal-based MHEs are essential to ensure the economic viability of such devices. The present study focuses on the results of heat transfer testing of assembled Cu- and Al- based microchannel heat exchanger (MHE) prototypes. Efficient fabrication of Cu- and Al- based high-aspect-ratio microscale structures (HARMS) have been achieved through molding replication using surface engineered, metallic mold inserts. Replicated metallic HARMS were assembled through eutectic bonding to form entirely Cu- and Al- based MHE …

Short-Term Reliability Of A Thin Film Resistance Temperature Detector (Rtd), Julian W. Post, Jr.

Theses and Dissertations

The primary focus of this dissertation was on the short term reliability of a thin film resistance temperature detector (RTD). As a first step, the transient and steady state temperature response of an encapsulated, thin-film RTD, which was used as a micro heater, have been characterized for a range of pressures and applied voltages, while placed on thermally insulating and conductive platforms. A user-friendly model was used to capture the three major mechanisms of heat transfer from the device (i.e. conduction, convection, and radiation). The calibration parameters of the model allowed the different modes of heat transfer to be quantified. …

Evolution Of Turbine Blade Deposits In An Accelerated Deposition Facility: Roughness And Thermal Analysis, James Edward Wammack

Theses and Dissertations

During the operation of a gas turbine, ingested contaminants present in the air form deposits on the surfaces of the turbine blades. These deposits grow over time, resulting in an increasingly rough surface. This gradual increase in roughness results in several negative consequences, among which is an increase in the rate of heat transfer to the blade which shortens blade life. This thesis presents research in which deposits were evolved on three different turbine blade coupons and their evolution was studied. A trend in roughness change over time was discovered. Also, an attempt was made to find the effect of …

Approximate Thermal Modeling Of Radiofrequency Cardiac Ablation, Aaron Joseph Walter

Theses and Dissertations

The ultimate objective of the research which led to this thesis is to increase the efficacy and safety of radiofrequency catheter ablation (RFCA) of cardiac tissue. The purpose of RFCA is to carefully heat selected locations in the heart. The resulting thermal injury creates lesions which prevent the generation or propagation of arrhythmias. The ability to predict the appropriate amount of energy required at any ablation site is essential to increasing the efficacy and safety of RFCA. The research documented in this thesis focuses on the development of an approximate thermal model of the time-dependent temperature profile within the myocardium …

P-Version Time-Discontinuous Galerkin's Method For Nonlinear Transient Heat Transfer Analysis And Sensitivity Analysis, Ta-Cheng Chien

Mechanical & Aerospace Engineering Theses & Dissertations

The finite element method is a powerful tool for approximating the solution of most engineering problems. Traditionally, the finite element method uses linear approximation of field variables over each element, where numerical results converge to the exact solution by increasing the number of elements. A newer finite element method called the p-version finite element method uses higher-order elements which assume a polynomial of order p for the approximation on each element. Here, the approximation will achieve accuracy without increasing the number of elements but by increasing the value of order p.

The focus of this research is on …

Thermally Developing Electro-Osmotic Convection In Circular Microchannels, Spencer L. Broderick

Theses and Dissertations

Thermally developing, electro-osmotically generated flow has been analyzed for a circular microtube under imposed constant wall temperature (CWT) and constant wall heat flux (CHF) boundary conditions. Established by a voltage potential gradient along the length of the microtube, the hydrodynamics of such a flow dictate either a slug flow velocity profile (under conditions of large tube radius-to-Debye length ratio, a/lambda_d) or a family of electro-osmotic flow (EOF) velocity profiles that depend on a/lambda_d. The imposed voltage gradient results in Joule heating in the fluid with an associated volumetric source of energy. For this scenario coupled with a slug flow velocity …

The Development Of An Accelerated Testing Facility For The Study Of Deposits In Land-Based Gas Turbine Engines, Jared Wilfred Jensen

Theses and Dissertations

Turbine engine efficiency modeling depends on many parameters related to fluid dynamics and heat transfer. Many of these parameters change dynamically once the engine enters service and begins to experience surface degradation. This thesis presents a validation of the design and operation of an accelerated testing facility for the study of foreign deposit layers typical to the operation of land-based gas turbines. It also reports on the use of this facility in an effort to characterize the change in thermal resistance on the surface of turbine blades as deposits accumulate. The facility was designed to produce turbine deposits in a …

3-D Numerical Simulation Of Reactive Extrusion And Its Application To Polymerization Of Ε-Caprolactone In Co-Rotating Twin-Screw Extruders, Linjie Zhu

Dissertations

A 3-D numerical simulation model was proposed to predict the polymerization of ε-caprolactone in fully-filled conveying elements and kneading blocks of co-rotating twin-screw extruders, in which the kinetics equation for polymerization is coupled with continuity equation, momentum equation, and energy equation. With the 3-D model, parametric studies have been carried out to investigate the effects of screw configurations, screw diameter, operational conditions, values of heat from reaction, initiator concentration, and heat transfer conditions at barrel surface upon the polymerization progress. Two simulation models for the polymerization in the partially-filled channels were developed based on the conveying mechanisms of the reaction …

Turbine Blade Tip Cooling And Heat Transfer, Hasan Nasir

LSU Doctoral Dissertations

Turbine blade tip leakage flow from blade pressure side to suction side over the tip surface increases the thermal loading to the blade tip, leading to a high local temperature and thus, is considered one of the primary sources of blade failure. Leakage flow can be reduced by using a recessed or squealer tip blade or by cooling the blade tip to incorporate film cooling. The performance of different recessed tip geometries were investigated and compared with plane tip performance. A transient liquid crystal technique was employed to measure detailed heat transfer coefficient distributions. Coolant injection from holes located on …

Innovative Cooling Configurations For Low Emission Gas Turbine Combustors, Ryan Thomas Hebert

LSU Master's Theses

Presently, effective cooling of modern low NOx combustor liners is achieved through combinations of innovative impingement configurations and other heat transfer enhancement methods. An inherent characteristic of conventional impingement configurations is the occurrence of downstream heat transfer degradation due to increased crossflow effects. In the present study, two different impingement configurations are studied. Both impingement configurations examined in this study aim to increase heat transfer effectiveness by reducing the detrimental effects of spent air crossflow. In Part I, a combination technique wherein impingement is combined with ribs placed in between impingement rows is studied. Three configurations with increased rib placements …

Design And Fabrication Of A Microscale Joule -Thomson Refrigerator, Lionel Gamini Hewavitharana

Doctoral Dissertations

A simple thermodynamic, heat transfer, and fluid flow model was developed for microscale Joule-Thomson refrigerators (JT devices). For a given geometry, the model predicted that the cooling capacity of the refrigerator increased with the inlet refrigerant pressure. The effectiveness of the JT device also increased with the inlet pressure, and the heat exchanger channel length. At a constant inlet pressure, the effectiveness, and the refrigeration capacity of a given JT device increased as the aspect ratio of heat exchanger channels was increased. For nitrogen refrigerant, the model predicted that it was possible to obtain approximately 250 mW of refrigeration capacity …

Effect Of Unsteady Wake, Free Stream Turbulence, Tip Geometry On Blade Tip Flow And Heat Transfer, Vikrant Saxena

LSU Master's Theses

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer. The linear cascade is made of four blades scaled up HPT turbine in a low speed wind tunnel facility with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116 degree turn in the flow through the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83e5. The center blade …

Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb

Theses and Dissertations

This research effort investigated the effects of evaporation of water on the heat transferred to the wall of the diverging portion of a porous walled nozzle The AFIT High Pressure Shock Tube was used with a two-dimensional Mach 3 nozzle. One flat surface of the nozzle was fitted with a layer of porous stainless steel from the nozzle throat to the exit. This porous material was saturated with water to simulate liquid transpiration cooling. Surface temperature data was taken in this region using fast response coaxial thermocouple. Heat transfer was determined from the surface temperature history. Data was taken for …

Two-Phase Flow In Microchannels, Roger Scott Stanley

Doctoral Dissertations

The purpose of this study was to investigate fluid mechanic and heat transfer characteristics of two-phase two-component flow in rectangular microchannels. Experiments were conducted using rectangular aluminum channels with hydraulic diameters ranging between 56 $\mu$m and 256 $\mu$m and aspect ratios which varied from 0.5 to 1.5. Both single- and two-phase tests were conducted using water and gaseous argon, helium, and nitrogen as the working fluids. The Reynolds number for both types of experiments ranged from approximately 50 to nearly 10,000. The Nusselt number ranged between 0.0002 and 70. The single- and two-phase experimental data were empirically correlated, using parameters …

Are Energy Savings Due To Ceiling Fans Just Hot Air?, Florida Solar Energy Center, Patrick James

FSEC Energy Research Center®

Human comfort studies have shown that people prefer higher temperatures when they are subjected to a breeze. Ceiling fans are often used to create air motion in residences. Simulation studies (including one given in this paper) have demonstrated that in Florida, using ceiling fans combined with raising a home's temperature 2° F will generate about a 14% net savings in annual cooling energy use (subtracting out the ceiling fan energy and accounting for internally released heat). This savings drops to 2.6% with a 1° F increase in set point and to a negative 3.7% savings with only a 0.5° F …

Laminar And Turbulent Natural Convection Heat Transfer In Trombe Wall Channels, Tony D. T. Chen

Mechanical & Aerospace Engineering Theses & Dissertations

The natural convective heat transfer and air movement in a Trombe wall solar passive system has been studied analytically and numerically. Three Trombe wall channel geometries including the parallel channel with axial inlet and exit, parallel channel with side vents and Trombe wall channel coupled to the room have been considered. Several models representing these Trombe wall geometries have been formulated. For the parallel channel with axial inlet and exit geometry, a momentum-integral method has been used to solve parabolic governing equations for two-dimensional laminar flow. This formulation leads to a second order ordinary differential equation for pressure defect in …

Development Of A Spray Drought Cooling Tower, O. K. Kaunde

Tanzania Journal of Engineering and Technology (TJET)

ABSTRACT A noval type direct contact cooling tower has been proposed in which the gas or air entering the tower is drawn by the ejector action of the sprays through which the feed water is admitted. The advantage offered by this type of tower is that it eliminates the usages of fan, thus saving the capital cost and power to drive it.

Entrainment of air by water was studied in a laboratory cooling tower and the result of the entire experiment indicate that the development of a spray drought tower is a feasible practice.

Solar Ovens And Cookers, Florida Solar Energy Center

FSEC Energy Research Center®

Solar ovens work much like solar collectors used in domestic water heating systems. Both collect solar radiation, convert it to heat and transfer it to another substance. Solar ovens, however, focus the sun's rays with reflective surfaces on one point. The object of the sun's energy in the solar oven is the food.

Designing And Installing Radiant Barrier Systems, Florida Solar Energy Center, Philip W. Fairey

FSEC Energy Research Center®

A radiant barrier system is, in general, a layer of foil facing an airspace, installed in the envelope of a building. Such systems are very effective in impeding radiant heat transfer and consequent heat gain, especially in southern residences. Before designing and installing a radiant barrier system, you should become familiar with the concept of radiant energy transfer. Design Note 6, Radiant Energy Transfer and Radiant Barrier Systems in Buildings, is required reading if you are not familiar with this concept.