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Our current areas of research are illuminated below. For more details, please see our Publications or contact Matthew J. Traum.
Those interested in helping out with one of the following projects should visit the Join page.
During evaporative cooling, vapor mass transport carries energy bound as latent heat away from a hot surface toward a hotter ambient environment by using a concentration gradient to pump heat against a temperature gradient. Systems enclosed in protective covers often require cooling (e.g., soldiers wearing body armor), but evaporative cooling is impeded by the vapor transport resistance presented by the protective cover. Inlaying protective barriers with micro/nano-pores enables mass transport through that layer without reducing its protective properties.
This project identifies the impacts of pore size, shape, and distribution during simultaneous heat and mass transport through protective porous barriers using common working fluids including water and alcohols. We focus especially on nano-scale effects that accelerate mass transport and improve evaporative cooling, which emerge only when the pore diameter is on the order of the vapor mean free path.
A computer simulation to predict Tesla turbine performance is being experimentally validated using a custom-built pressurized-air-driven Tesla turbine apparatus. The validated model will be applied to predicting performance of a miniaturized Tesla turbine within a tiny Brayton cycle.
While inefficient in the macro-regime, Telsa turbines are expected to exhibit excellent performance at low Reynolds Number where fluid viscous forces dominate. Using Telsa turbines in miniature generators, we anticipate improving portable energy generation technology for military, homeland security, portable electronics, and remote power applications.
NASA stated the potential of Rankine cycles to revolutionize isotropic power plants for manned space flight: “high thermodynamic cycle efficiencies reduce the power requirements of the nuclear reactor and thus its weight, shielding, and heat rejection requirements.” However, NASA cautioned that the necessary enabling technologies are still years from realization.
Building upon UNT’s existing cryogenic power cycle expertise, we are creating a cryogenic Rankine cycle for space that can be quickly fabricated using existing, proven NASA and US Air Force technologies. We have already shown that space-based cryogenic Rankine cycles are more efficient than solar panels now in orbit, while untethering spacecraft from need for continuous sunlight.
The key to microgravity Rankine cycle operation is condenser phase separation. This process is achieved through passage of two-phase working fluid through capillary-lined porous barriers that promote liquid-wall adhesion via high cryogenic liquid surface affinity. This micro-separation process will be closely studied to guarantee Rankine cycle reliability in micro-gravity.
We are making instruction in building energy auditing globally available through a module-based energy engineering laboratory curriculum (MEELC) using inexpensive handheld instruments. Training energy professionals in developing countries with these skills will create new building energy audit niches within emerging economies by
This project has three components:
Track-etched barriers are commercially available in a variety of pore diameters, but the most interesting transport and separation processes emerge in barriers with pores smaller than 10 nanometers. Pore diameter control at this tiny size scale is an unresolved fabrication challenge.
To modulate pore diameter in polymer barriers, we propose controlled heating in a special fixture. By elevating temperature while suppressing changes in matter state and chemical composition, thermal tension and creep cause the barrier pores to change size.
Preliminary experiments have already confirmed that annealing can elongate pores. We are now improving this process to convert commercial mico-porous barriers into highly controlled custom nano-porous barriers. Importantly, this process has potential to achieve barriers of any pore diameter; researchers are no longer restricted to only commercially available pore dimensions.
A technique to create barriers with pores with deliberately fabricated sharp corners is being pioneered and tested.
Prior research shows that liquid wicking into sharp-cornered pores dries and evaporates rapidly, even in high humidity ambient environments. Simultaneous heat and mass transport analysis of these humidity-independent drying processes will measure rates of latent heat binding to show whether these porous barriers can accelerate evaporative cooling in humid environments.
A technique to create barriers with pores having hydrophilic entrances and hydrophobic exits is being pioneered and tested. We expect evaporative cooling from wetted surfaces in contact with these barriers to be accelerated. A liquid/vapor evaporation front forms within the barrier’s pores, which balances two competing effects: wicking mass transport and convective mass transport.
The extent these processes contribute to cooling can be modulated by controlling the hydrophobic/hydrophilic boundary location within the pores during the fabrication process.
To deploy renewable energy technologies at UNT’s Discovery Park, the available resource base is continuously monitored by the North Texas Ambient Energy Monitoring Station (NT-AEMS), which is the only meteorology station in the US operated by a mechanical and energy engineering department.
NT-AMES includes all sensors required for compliance and data sharing with both the nearby Oklahoma Mesonet and the West Texas Mesonet weather monitoring networks. Our installation’s measurement capabilities include air temperature, wind velocity, humidity, barometric pressure, and normal-direct solar radiation. In addition to these standard weather monitoring capabilities, NT-AEMS includes a sun tracking pyranometer, wind anemometers at multiple elevations, and deep ground temperature sensors to measure the resource base for solar, wind, and geothermal energy respectively.
Data collected through NT-AEMS will inform design and deployment of renewable energy technologies at UNT and the surrounding region.
High exposed surface temperature reduces photovoltaic (PV) generator efficiency, but it improves thermoelectric (TE) generator efficiency. This behavior is an important consideration for remote, solid-state, solar concentrating generators, which focus enormous power onto small target areas. Resulting temperatures exceed the threshold beyond which TEs become a competitive alternative to PVs. Importantly, water is typically evaporated as a coolant from PV installations in arid regions to regulate temperature, straining the local water supply.
Our TE solution has potential for higher energy conversation efficiency while eliminating need for PV coolant water. Currently, we use a TE surrogate illuminated under Fresnel-concentrated sunlight in controlled outdoor conditions to provide critical design parameters including absorbed thermal power, energy reflectivity index, and maximum temperature. Solar reflection from the target surface represents the most serious impediment to achieving high temperature, and we are now exploring reflection-reducing coatings to promote TE as a viable PV alternative in solar concentrating generators.
A network of wireless indoor sensors is to be installed throughout UNT’s Discovery Park. This sensor network will measure temperature, barometric pressure, ambient light level, and relative humidity in the space to inform how energy is used to sustain human comfort.
Discovery Park is a large indoor educational space adapted from a previous industrial occupant. As a result of age and change from original intended use, data collected from Discovery Park’s hard-wired sensor network provides an incomplete picture compared to purpose-built sensor systems in more contemporary buildings. Discovery Park, therefore, is an ideal test bed for building energy technologies deployed in re-tasked buildings.
Through an endurance study, we determined whether wireless sensors could be operated as stand-alone wireless units. In addition, wireless sensor data reliability and accuracy were compared against existing hard wired thermostats.
Typical residences consume power even when no one is home during the day. Peak power grid demand also occurs in the middle of the day, which coincides with the sun being directly overhead - ideal solar energy collection time. By combining three well-studied energy conversion and concentration technologies in a new way, we are creating a pollution-free residential-scale solar steam power plant to completely offset a home's base power consumption. The three technologies to be integrated are 1) a solar-fired boiler using a Fresnel lens for sunlight collection, 2) a self-starting hit-and-miss steam engine and flywheel, and 3) an electric generator with battery storage.
The key novelty of this approach is the self-starting hit-and-miss steam engine and flywheel combination, venerable technology widely used at the turn of the 20th century for which we have found new application. Once the flywheel is spinning, the steam engine coasts, releasing a burst of energy only when needed to maintain a set rotational velocity. This operation, the hallmark of hit-and-miss engines, allows boiler pressure to build between engine firings, providing constant power output despite intermittent sunlight conditions. The flywheel turns a generator, providing power to the home.
In an annual, team-based, lower-division, design-and-build project, students try to create the fastest solar-powered winch-and-cart system for a competitive drag race. Performance of these solar cars and design improvements leading to enhanced performance are being logged over the 10-year lifetime of this project. Winning vehicles from the previous year will be presented to the next ensuing class year, enabling students to use successful elements from previous entries as a baseline for their designs.
Our intent is to illuminate the effectiveness of introducing an annually repeating competitive design-and-build project targeted to teaching basic principles of design. We anticipate that the cars’ performance will improve each year because students will incorporate successful elements and avoid weaknesses inherent in previous winning designs. Performance improvement, if observed, demonstrates that students are learning a fundamental element of engineering: design is an evolutionary process.
We are collecting three consecutive years of pre/post data to assess the impact of exposing new students to the careers of practicing engineers. The Department’s first-year experience classes are team-taught by faculty and engineers from local companies. We feel practice exposure is a significant component of the freshman year because this approach highlights the activities and responsibilities students will encounter as engineers when they join the profession. This course therefore empowers them to make an early informed choice about whether they wish to persist in engineering.
While students’ self-reported level of interest in pursuing engineering careers remains positive and unchanged after exposure to engineering practitioners, students’ post-assessments indicate a statistically significant decline in desire to remain in the Department. We are analyzing the data to resolve possible sources of this discrepancy and to evaluate whether early exposure to engineering practitioners is detrimental to STEM retention.
