No description available.

No description available.

No description available.

No description available.

<p>Radiative thermal management has become increasingly more relevant within the past few decades due to the avocation for higher efficiency buildings, increases in</p> <p>power densities with decreases in form factors, and cutting-edge technologies for space exploration. This research focuses on engineering coatings with spectrally selective optical properties to achieve ultra-efficient thermal management via passive radiative cooling of both terrestrial and extraterrestrial applications. Terrestrial radiative cooling is a phenomenon of passively cooling exterior surfaces below ambient temperatures by engineering coatings to exhibit low absorptance in the solar spectrum (0.25 μm< λ <2.5 μm), such that a minimal amount of solar irradiation is absorbed, and high emittance in the transmissive portion of the atmosphere (8 μm< λ <13μm), i.e. the sky window, to lose heat to deep-space for a net cooling effect. Deep-space is considered to be an infinite heat sink at 3 K. Extraterrestrial radiative cooling requires the same criteria as terrestrial radiative cooling, however, there is no atmosphere to block a portion of the solar irradiation or the emission from the surface. A key requirement for achieving passive radiative cooling for an ideal emitter during daytime is a total solar reflection >85%, and every 1% above this threshold results in ≈10 W/m2 gain in cooling power. Here, recognizing the broadband nature of solar irradiation, we propose and test a new concept of enhancing solar reflection at a given particle volume concentration by using hierarchical particle sizes, which we hypothesize to scatter each band of the solar spectrum, i.e. VIS, NIR and UV effectively. The hypothesis is tested using a TiO2 nanoparticle-acrylic system. Using the Mie Theory, the scattering and absorption efficiencies and asymmetric parameter</p> <p>of nanoparticles with different sizes and combinations are calculated, then the Monte Carlo Method is used to solve the Radiative Transfer Equation. An overall total solar</p> <p>reflection of ≈91%, which is higher than the ≈78% and ≈88% for 100 nm and 400 nm single particle sizes, respectively was achieved from our hypothesis.</p> <p>With increasingly better RC materials being demonstrated in literature, there is a growing need to understand the real-world utility and benefit of RC with regards</p> <p>to energy savings. A fundamental limit of current radiative cooling systems is that only the top surface facing deep-space can provide the radiative cooling effect, while</p> <p>the bottom surface cannot. Here, we propose and experimentally demonstrate a concept of “concentrated radiative cooling” by nesting a radiative cooling system in a mid-infrared reflective trough, so that the lower surface, which does not contribute to radiative cooling in previous systems, can radiate heat to deep-space via the reflective</p> <p>trough. Field experiments show that the temperature drop of a radiative cooling pipe with the trough is more than double that of the standalone radiative cooling</p> <p>pipe. Furthermore, by integrating the concentrated radiative cooling system as a preconditioner in an air conditioning system, we predict electricity savings of > 75% in Phoenix, AZ, and > 80% in Reno, NV, for a single-story commercial building. We further look into unique applications of radiative cooling for outdoor enclosures</p> <p>of electrical equipment, as demonstrated with a case study of coating pole-type distribution transformers. Utilizing RC paint on the exterior of the case would allow further dissipation of heat to deep-space, as well as, increase the solar reflectance to lessen the heat load on the case. A single 25 kVA pole-type transformer is modeled</p> <p>via CFD with two different exterior case coatings, the standard grey coatings commonly utilized and an RC coating, BaSO4 paint, is analyzed under different operating loads. The RC coating demonstrates great benefits from a thermal management perspective</p> <p>and a gain in the lifetime of the windings. The RC coating cooled a 25 kVA distribution transformer’s core by > 11oC when compared to the standard case and even shows below ambient cooling of the case under minimal heat generations. The lifetime of the distribution transformers was increased by a minimum of 55% when comparing the standard case to the case with a radiative cooling paint based on the Aging Acceleration Factor. A more traditional application of radiative cooling paints is to utilize them on the exterior of buildings to offset the cooling energy demand for air conditioning. This work develops a high-fidelity RC model which accounts for pertinent weather factors including precipitable water, sky clearness, and dynamic convective heat transfer coefficients based on wind speed to further understand the energy savings. We implement our RC model on a single-story residential building to study the impact of RC in every unique ASHRAE climate zone in the United States using the 16 DOE recommended representative cities. Our results show > 7% and > 12% cooling energy savings across the United States for NREL’s building and typical buildings, respectively. Furthermore, warm climates yield the greatest cooling energy savings of up to 22% and 46% for the NREL and the Typical building, respectively. Extraterrestrial radiative thermal management is becoming increasingly pertinent with the development of new space technologies and the need to discover what is beyond</p> <p>our world. Space presents extreme thermal environments for radiative transfer, from a total eclipse case where the body radiates to deep space at 3 K to a full solar load where 1400 W/m2 is radiated onto the surface and a hybrid of both situations. The goal of this work is to engineer micropatterned Lanthanum Strontium Manganite</p> <p>(LSM) Barium Sulfate (BaSO4) coatings as efficient variable emissivity coatings (VECs). The photon transport through the micropatterned system is modeled using</p> <p>geometric optics and Monte Carlo coupled with geometric optics to obtain the coatings reflectivity, transmissivity, and emissivity to predict the ideal reflectivity and</p> <p>emissivity of the micropatterns. Then the micropatterned LSM coatings are experimentally fabricated using screen printing on a BaSO4 paint layer. The coatings are</p> <p>characterized by their temperature-dependent variable emissivity and solar absorptivity from the dual-layer micropatterned coatings. Furthermore, a computational model for a body-mounted cylindrical radiator was developed to investigate the real implications a VEC can have on crewed space vehicles, as well as define some target guidelines for VEC’s to achieve in future technologies.</p>

<p>In this thesis we present a procedure by which synthetic photometry of a hydrodynamic model of star or star-like object can be calculated in a regime where the photosphere is not radially resolved. In order to properly model the unresolved photosphere, we present a method where pressure and density are integrated outward from the outermost resolved radius of the star and then interpolated in temperature-surface gravity space between a set of MARCS \citep{Gustafsson2008a} stellar atmosphere models. These interpolations are accurate to within 10\% of expected temperature values and are determined by minimizing the difference between the integrated pressure, density and surface gravity and that of the atmosphere model. Using the Monte Carlo Radiative Transfer code \texttt{radmc3d}\citep{Dullemond2012}, we produce blackbody spectra of stars and photometric light curves of equal and unequal mass detached binaries and a contact binary. Stellar blackbody spectra are accurate to better than 1\%. Resultant light curves have less scatter than existing methods, such as \texttt{shellspec}\citep{Budaj2004} and show the expected morphology. Our method allows for imaging directly from hydrodynamic simulations, with minimal user set-up. This procedure is designed with the intent of producing simulated photometry of stellar merger models.</p> / Master of Science (MSc)

The greenhouses play a key role in food sustainable production, the purpose of the greenhouses is to make an artificial suitable environment to grow different kinds of plants. The cost of energy used in the greenhouses to ensure the optimum temperature, humidity, and CO2 concentration, makes up a large part of the final cost of food. Due to global warming, the successive energy crises, and the food crises, the need to make the greenhouses more energy efficient and to utilize renewable energy resources is rapidly increasing. The enclosed water curtain cooling system meets the special requirement of the greenhouse cooling system, and it has potential energy savings when it is integrated with other systems such as heat pumps, underground water sources, and surplus heat energy recovery. This system involves two special nylon foils, and a thin layer of water flows between the two foils, the two foils will be stuck to eachother by the cohesive force of the water-detergent mixture, the detergent was added to decrease the water surface tension and ensure the even distribution of the water-detergent mixture over the nylon foils. In this study, an experimental model of the enclosed water curtain was made and two sets of tests were conducted, the first set was at room temperature around 20°C, and the second test was at room temperature around 25.7 °C with an electrical heater, each set contains three tests to measure the cooling capacity of the curtain, and each test takes 2 minutes, the curtain dimensions were height and width of 1.04 m and 1.20 m respectively. By measuring the difference between the average inlet and outlet temperature of the water-detergent mixture before and after the curtain, and the mixture mass flow rate during the test period, the cooling capacityof the curtain was calculated using the energy balance equation.It was found that the curtain cooling capacity increases with the increase of ambient temperature, The large heat transfer area of the curtain which allows using higher water temperature for cooling, and the useful features of the water membrane like the high absorption of the wavelength of infrared and the high transparency of the wavelength of visible light, make this system meets the special requirements of the greenhouses cooling system. However, to be able to apply this system in real-life, the design of the curtain should be improved, and suitable materials should be chosen to make it more reliable. Also, All tests in this study were conducted in the workshop in the absence of solar radiation, therefore, the actual performance of the curtain needs to be evaluated with the presence of solar radiation, to be able to study the effects of the direct and diffuse solar radiation with various spectrum range.

Yes / In this paper, the Chebychev spectral collocation method is applied for the thermal analysis of convective-radiative straight fins with the temperature-dependent thermal conductivity. The developed heat transfer model was used to analyse the thermal performance, establish the optimum thermal design parameters, and also, investigate the effects of thermo-geometric parameters and thermal conductivity (nonlinear) parameters on the thermal performance of the fin. The results of this study reveal that the rate of heat transfer from the fin increases as the convective, radioactive, and magnetic parameters increase. This study establishes good agreement between the obtained results using Chebychev spectral collocation method and the results obtained using Runge-Kutta method along with shooting, homotopy perturbation, and adomian decomposition methods.

This dissertation presents three different aspects of the incorporation of directionality into the Monte Carlo ray-trace (MCRT) environment: (1) the development of a methodology for using directional surface optical data, (2) the measurement of the bi-directional reflectivity functions for two different surfaces, and (3) MCRT simulations performed using these directional data sets. The methodology presented is based upon a rigorous analytical formulation and is capable of performing simulations of radiation exchange involving directional emission, absorption and reflection given the bi-directional reflectivity functions (BDRF) of the participating surfaces. A wavelet compression technique is presented for the management of extremely large directional data sets. The BDRFs of two different surfaces were acquired using a Surface Optics Corporation model SOC-250 bi-directional reflectometer. These data were processed according to the methodology presented and an MCRT code was used to simulate the action of the SOC-250 in measuring radiant energy reflected from the surfaces of the two samples when illuminated by the source of the SOC-250. Another MCRT code was used to simulate the radiant energy reflected into a plane at the exit of an open-ended rectangular box when the entrance to the box is illuminated by source of the SOC-250. The RMS error between the MCRT simulations of sampling using the SOC-250 and the measured data were determined and then divided by the mean BDRF level of the measured data (RMS/mean[rho]) to provide an estimate of convergence. The RMS/mean[rho] was observed to fall from as much as 138 to 0.84 for the aluminum substrate coated with Krylon Shortcuts Hunter Green Satin aerosol paint as the number of energy bundles emitted in the MCRT simulation went from 103 to 106 at an incident zenith angle of 40 deg. The RMS/mean[rho] was observed to fall from as much as 2.2 to 0.2 for the Norton (150 Fine grit) all-purpose sandpaper coated with Krylon Shortcuts Hunter Green Satin aerosol paint as the number of energy bundles emitted in the MCRT simulation went from 103 to 106 at an incident zenith angle of 40 deg. / Ph. D.

To date, there exists no complete, computationally efficient, physics-based model to compute the radar backscatter from forest canopies. Several models attempt to predict the backscatter coefficient for random forest canopies by using the Vector Radiative Transfer (VRT) Theory with success, however, these models often rely on purely time-harmonic formulations and approximations to integrals. Forms of VRT models have recently been developed which account for a Gaussian pulse incident waveform, however, these models often rely heavily on very specific and obfuscated approximations to solve the associated integrals. This thesis attempts to resolve this problem by outlining a method by which existing, proven, time harmonic solutions to the VRT equation can be modified to account for arbitrary pulse waveforms through simple path delay method. These techniques lend physical insight into the actual scattering mechanisms behind the returned waveform, as well as offer explanations for why approximations of previous authors' break down in certain regions. Furthermore, these radiative transfer solutions can be reformulated into a convolutional model which is capable of quickly and accurately predicting the radar return of random volumes. A brief overview of radiative transfer theory as it applies to remote sensing is also given. / Master of Science