Student Abstracts: Engineering at ORNL

Evaluation of the EMI Heat Pump Water Heater impact on the residential climate control system. GUSTAVO ARAMAYO (Iowa State University, Ames, IA 50013) JJ TOMLINSON (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Rather than strictly using electric energy, a heat pump water heater utilizes the ambient heat, producing hot water and cooled, dehumidified air. By utilizing ambient heat, the heat pump water heater requires much less energy than the conventional electric resistance water heater. However, since the evaporator of the heat pump relies on ambient heat to function, the overall performance of the unit depends on its location, namely if in a conditioned (such as a closet) or unconditioned (such as a garage) environment. To evaluate the overall impact of a heat pump water heater's location, an experiment was set up and is being conducted in an unoccupied house near Oak Ridge. An actuated valve was placed in the hot water line and programmed to regularly make water draws similar to those of a typical family. Sensors were placed on and around the water heater to determine the impact of the heat pump water heater on the heating and cooling loads of the house. Data was gathered to characterize the room the unit was located in as well as the water heater's performance itself. From this data, an assessment of the impact of the heat pump water heater on the space conditioning loads was performed.

Applications of Modified Microcantilever Tips. MATTHEW DELGADO (University of Texas at Austin, Austin, TX 78723) PANOS. G. DATSKOS (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
The atomic force microscope (AFM) has mainly been used to image a variety of substrates using common tipped cantilevers with a small radius of curvature (typically 20-60 nm). Tipped cantilevers consist of a pyramid like structure extending normally from the cantilever plane. Variations from tip to tip causes uncertainty in the dimensions of the tip, therefore microspheres are attached, at the tip of the cantilever, whose radius is well known. The microspheres are KromasilÒ and have an average diameter around 10m. The spheres are made out of high purity silicon and a various concentrations of carbon. The spheres are attached by using an optical fiber to pick up a sphere and a human eyebrow hair to apply the epoxy to the cantilever tip. The optical fiber and the eyebrow have tips that are approximately 10m in width. This makes eyebrow and optical fiber the correct order of magnitude to pick up the spheres and apply the glue. The epoxy must be workable for at least five minutes order to have enough time to attach the sphere. After attachment the spherical tip can be used in the AFM to create a liquid bridge between the sphere and the surface. By having a spherical tip of a known radius, one can use the Kelvin equation, which has been verified for this order of magnitude, to measure the surface tension of a liquid bridge. This surface tension is measured by observing the deflection of the cantilever, as it comes in contact with the surface to when it releases. Then force vs. distance curves can be constructed. Furthermore, the tips can be used to measure the friction of the substrate by operating the AFM in contact mode.

Fabrication and Testing of Bi-metallic Micro and Nano Tweezers using the Focused Ion Mill and Evaporator. BRENT GEORGE (Tennessee Technological University, Cookeville, TN 38505) PANOS DATSKOS (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
The manipulation of objects on the micro and nano scales is a very challenging process. To manipulate these structures, especially free standing structures, special tweezers need to be fabricated with various tips to minutely move and orient these structures as needed. The tweezers are fabricated using the focused ion mill. Each edge is cut away from either an undoped piece of silicon or a silicon nitride cantilever. Next, the milled tweezers are put in the evaporator to apply chromium (5nm) and gold (0.1ìm). By applying a potential of opposite polarity across the bi-metallic tweezers they will attract to one another due to elastic deformation of the legs. Once the tweezers make contact, electrostatics keep them together. An insulating layer between the legs is needed to prevent them from connecting electrically. Tips for the tweezers can be made into any shape that is desired for the given task, however since the tip is part of the tweezers a new set of tweezers must be made for every given tip. By expanding the number of various tips and tweezers an arsenal of tweezers can be constructed and be readily available the next time the same task presents itself. Mounting the tweezers is also a difficult task. Since the tweezers themselves are made of thin fragile materials like that of which you are trying to manipulate special care must be made in the mounting harness. The design envisioned in this process would give forward and backwards motion as well as a 90° rotational factor. Using this harness and the tweezers that can be constructed, manipulating micro and nano structures is simplified to an extent not possible with the bare hand.

The Application of Microcantilevers in an Aqueous-based Chemical Detection System. KATHLEEN GIESFELDT (University of Texas at Dallas, Richardson, TX 75083) PANOS DATSKOS (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Many chemicals can cause serious injury or death at level well below the ppm range. Many chemical detection systems have been developed to identify airborne and water-borne contaminants. However, numerous chemical warfare agents and some industrial chemicals are hazardous well below the detection limits of most commercially available instruments. In previous research in this laboratory, it has been determined that commercially available microcantilevers, similar to those used in atomic force microscopy, can be used to detect single elements or chemical compounds at ppb range in the gas phase. In this work, chemical detection in an aqueous solution with microcantilever-based optical detection systems is demonstrated. The deflection of microcantilever was observed using a low-power diode laser operating and a four-element silicon photodiode (quadcell) when different concentrations of saline, ethanol, and isopropanol were flowed at 1 ml min-1 into a sample cell. The output of the quadcell was connect ed to an oscilloscope. The microcantilever deflections, which were detected, were recorded as a function of time using a lock-in amplifier. Microcantilever-based optical detection systems appear to be very sensitive in the detection of contaminants in aqueous solutions as was in the case with gas phase contaminants.

Evaluation and Development of RF Source for Cryomodule Testing. RYAN HALE (Tennessee Technological University, Cookeville, TN 38501) RAY FUJA (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
In the near future, Jefferson National Laboratory (JLab) will be conducting cryomodule cavity tests for the Spallation Neutron Source (SNS) project, and Oak Ridge National Laboratory (ORNL) and Los Alamos National Laboratory (LANL) are pooling their resources to provide JLab with the necessary facilities. One of the tasks of the SNS Accelerator Systems Division at ORNL is to provide JLab with a 1MW peak RF source that will include a power supply, energy storage, and fault protection (crowbar) system. An industry-built power supply was ordered to provide the ~100 kVDC necessary to operate the transmitter klystron. A crowbar cabinet, originally used in the Continuous Wave Deuterium Demonstrator (CWDD), was received from Argonne National Laboratory. This system implements a thyratron tube and is designed to protect the klystron in the event of a high voltage fault. The system is currently being evaluated and will soon be tested in the SNS Receiving/Acceptance/Testing/Storage (RATS) building. This evaluation includes circuit diagram generation and component testing. Following the testing and any necessary modifications, the system will be shipped to JLab for their testing.

Characterization and Analysis of a Typical T8 Luminaire for the Development of a Flexible Computer Based Control System. BRYAN HILSON (Central Piedmont Community College, Charlotte, NC 28235) J. D. MUHS (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Energy efficiency is a common concern in today's economy. The Hybrid Lighting Project combines energy conscience technologies like solar collection and remote source lighting. A hybrid luminaire blends both natural visible light with artificial fluorescent light. This requires a control system to maintain a constant total illumination by increasing and decreasing fluorescent light to inversely match the decrease and increase in natural light. Proper design of a hybrid luminaire control system required the characterization and analysis of a general purpose Lithonia Model 2GT8 luminaire, four Sylvania 4100k Octron fluorescent lamps, and two controllable rapid-start electronic ballasts from Advanced Transformer Company. A system-level evaluation of two potential hybrid luminaires was used to establish a base of knowledge for the development of an effective control system. A photosensor that utilizes transient signal analysis to distinguish between the fluorescent and natural light was used to develop the transfer equation that is the heart of the control system. A prototype hybrid luminaire was developed complete with fixture, fluorescent lamps, dimmable ballasts, photosensors, and software driven control system. With this prototype the control system can be further developed and future more efficient hybrid luminaires can be developed.

Design of Software for Motor Control Center for water pumps used in cooling water loops. THOMAS JUSTICE (Tennessee Technological University, Cookeville, TN 37845) JOHN HAINES (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
The neutron-scattering research that will be conducted at the Spallation Neutron Source (SNS) when completed is expected to benefit all areas of scientific research. Neutron scattering will take place in the mercury target when an intense proton beam bombards the target. Because the spallation process produces heat, various systems must be cooled down using cooling water loops. The target has five cooling water loops, four in the target building and one in the ring injection dump. This paper describes the control system, which is designed to operate the two pumps and four block valves in each cooling water loop. The control system provides the target operator with the ability to start the system through automatic procedures or manual procedures, as well as giving the operator valuable diagnostic information at the touch of a graphic interface button. The motor is controlled using a programmable logic controller (PLC) and the Experimental Physics and Industrial Control System (EPICS), which provides the graphical user interface. EPICS is the development tool used to access all the process variables. In conjunction with an input/output controller (IOC), EPICS communicates between the PLC and the user interface. The PLC allows EPICS to communicate with the motor starter over DeviceNet, which is standardized communication software and hardware.

Magnetic Levitation of Small Objects. RYAN KEREKES (University of Tennessee, Knoxville, TN 37916) PANOS G. DATSKOS (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Infrared detection is important in many applications such as thermal imaging, industrial process control, and chemical sensing. Using thermal MEMS (microelectromechanical systems) devices, IR detection can be accomplished. Thermal isolation of the micromechanical sensing element is very important in such applications because small amounts of heat energy must be detected by the sensor. Magnetic levitation provides a means of achieving thermal isolation. A magnetic levitation system can be used to "float" an unattached magnetically coated MEMS structure at a fixed position to achieve bending responses to infrared photons. An electromagnet connected to an active feedback circuit is necessary to keep the hovering MEMS in place. The circuit uses a pair of photodiodes and a laser to detect the position of the floating object, and it adjusts the strength of the magnetic field accordingly by varying the current through the electromagnet. Such a system could lead to new possibilities in precision and accuracy for IR detection applications.

Pitch-based carbon foams. SHAUN STINTON (University of Tennessee, Knoxville, TN 37996) JAMES KLETT (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Pitch-based carbon foams with high thermal conductivity are being researched for thermal applications. Foam is currently produced using a batch method that requires several different steps, and is costly. The objective of this project is to determine whether the foam can be made with extrusion in a continuous manner, which will decrease the cost. The extrusion is done through a series of chambers that forms a continuous tube. Pellets of mesophase pitch are ground up and melted in the screw extruder which contains several heating zones that create the proper molten phase. Molten pitch enters the metering pump, which controls the flow rate into the chambers after the pump, and the temperature is raised high enough for the pitch to foam and start solidifying. The pitch is cooled and exits through the die head. Testing relies on the heating profile of the extruder since chamber temperatures affect how the pitch foams. Different heating profiles have been tried, and the last run seemed to be close to what is needed. The testing showed that there was a problem in the design of the extruder, which caused the pressure to rise and flow to be affected. The problem was probably due to the change in shape of the chambers after the pump. Parts of the extruder were redesigned in order to have a continuous shape through the last several chambers. The samples taken from the first extruder runs were examined under a SEM, and the results were encouraging. Similar open celled porosity was found in both types of foam. The next step is to obtain better extruded foam samples so the properties of the extruded foam can be tested and compared to properties of foam made by the batch method.

Ammonia-Scrubbing Technology for Removal of Industrial CO2 Emissions. ROBERT TOWNSEND (Tennessee Technological University, Cookeville, TN 38505) DR. JAMES WEIFU LEE (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
A potential way in which to achieve 22% reduction in the emission of CO2 as outlined in the Kyoto Treaty is to use a method by which flue gas (15% CO2 by volume) from coal burning power plants is passed through a reaction chamber while a fine spray of ammonium hydroxide (NH4OH) is concurrently introduced to the resulting flue gas cloud. Theoretically, a reaction then occurs by which ammonium bicarbonate (NH4HCO3), a useful fertilizer, is formed from NH4OH and CO2. This product precipitates out as tiny white particles or aggregates of particles in the form of snow. In order to prove this reaction occurs, a bench scale model of this reactor was designed. Upon spraying by means of an electric field, it was found that particles did not form instantly, but instead only formed along the walls of the reactor where the NH4OH coalesced as it was sprayed. This product was harvested and analyzed using NMR analysis techniques. The product created was pure NH4HCO3, substantiating the concept behind this method. The mechanism by which the bicarbonate product forms turns out to be two phase. Ammonium carbamate is initially formed followed by a slower, second reaction where the carbamate is transformed into bicarbonate. In actuality the bicarbonate may have been forming, but due to the excess of water in the hydroxide solution and the high solubility of NH4HCO3, the particles were being absorbed into the water phase. This was demonstrated using a bubble tank that used NH4OH as the constant phase while bubbling pure CO2 through the fluid bed. Particles only precipitated out after the solution became saturated, thus showing an excess of water in the hydroxide solution.

Measurement of NST Superconducting Tapes in the Presence of an Applied Magnetic Field. MARCUS YOUNG II (University of Tennessee Knoxville, Knoxville, TN 37996) JONATHAN DEMKO (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
The ability of high temperature superconductors (HTS) to maintain superconducting properties in the presence of a magnetic field must be known for their use in present and future HTS applications. Although the critical current differs according to the manufacturing process, the critical current of HTS tapes generally degrade as the applied magnetic field increases. NST (Nordic Superconductor Technologies) superconducting tapes were constructed from a silver-metal alloy consisting of BSCCO-2223. V-I measurements of these tapes were performed at the Oak Ridge National Laboratory at 77K under DC operating conditions while in the presence of an applied magnetic field. A superconducting cryogenically-cooled magnet was used to achieve the desired magnetic field, and the orientation of the magnetic field was set by the position of the superconducting tape within magnet. V-I curves were taken for both the perpendicular and parallel magnetic field orientations. The critical currents where then calculated and plotted v ersus magnetic field.