Search

The current technologies to treat hypersaline produced water (PW), such as thermal evaporation, are usually energy-intensive and cost-prohibitive. This study developed a low-cost, robust, solar-driven carbon black and airlaid paper-based evaporator (CAPER) for desalination of PW in the Permian Basin, United States. The study aims to better understand the removal of aromatic organic compounds and heavy metals during solar distillation, water output, and heat transfer. Outdoor experiments using CAPER assisted with polystyrene foam in a single slope, single basin solar still achieved an enhanced average evaporation rate of 2.23 L per m2 per day, 165% higher than that of a conventional solar still. Analysis of heat transfer models demonstrated that CAPER solar evaporation achieved an evaporative heat transfer coefficient of ∼28.9 W m−2·K−1, 27.9% higher than without CAPER. The maximum fractional energy of evaporation and convection heat transfer inside the solar still with and without CAPER was ∼81.4% and ∼78.2%, respectively. For the PW with a total dissolved solids concentration of 134 g L−1, solar distillation removed 99.97% salts and over 98% heavy metals. The high removal efficiency of 99.99% was achieved for Ca, Na, Mg, Mn, Ni, Se, Sr, and V. Organic characterization revealed that solar distillation removed over 83% aromatic compounds. Solar desalination using CAPER provides a low-cost and high-performance process to treat PW with high salinity and complex water chemistry for potential fit-for-purpose beneficial uses. Image 1 • A carbon black and airlaid paper-based solar evaporator (CAPER) was developed. • Outdoor distillation of produced water (PW) achieved evaporation of 2.23 L m−2·d−1. • The evaporation rate of PW with CAPER is 165% higher than without CAPER. • Heat transfer coefficient with CAPER is 27.9% higher than without CAPER. • 99.97% salts, 98% metals, >83% aromatic compounds removed from 134 g L−1 TDS PW. [ABSTRACT FROM AUTHOR]

• Energy simulation of AIS using experimentally validated thermal resistances. • AIS evaluation at varying orientations, climate zones, and switching ratios. • Investigation of AIS switching and wall thermal conductivity/heat transfer. • Application of freeze timer to reduce the number of switches of AIS. Active insulation systems (AISs) in buildings are envelopes that integrate thermal insulation, thermal energy storage, and controls. Although different designs for AISs have been proposed in the literature, a comprehensive analysis of feasible AISs is lacking. This paper discusses the energy performance, peak demand reduction potential, and performance characteristics of an AIS that uses a concrete wall as thermal mass sandwiched between two solid-state thermal switches (STSs). These STSs change their thermal conductivity using an on/off metal switch to create or break a thermal bridge across the STS. This paper first describes the experimental setup, used to determine the ratio of thermal resistance during R-high (low thermal conductivity) and R-low (high thermal conductivity) states of the STSs. This ratio was then used in whole-building energy simulations to evaluate the performance of AIS walls across different climate zones with/without a freeze timer of 60 min. The timer was added to reduce the number of switches of STSs from one state to another, and hence the energy needed for these switches. Analysis of the switching frequency and interval of STSs, thermal conductivity of walls, impact of wall orientation, and heat transfer through the wall from the use of AIS at different climate zones/locations were performed. The simulation results show that the AIS can achieve energy savings ranging from ∼ 980 to 2,290 kWh in a single-family home with a floor area of ∼ 220 m2 compared with an IECC 2018 baseline. The energy savings was higher in dry climate zones which represent 17% of residential buildings in the United States, compared to humid or marine climate. [ABSTRACT FROM AUTHOR]

Buildings contribute to about 40% of total annual energy consumption in the U.S. and saving a small percentage of that can lead to significant economic and environmental impacts. Building Energy Modeling (BEM) tools are important in reducing building's energy consumption. Most of the available tools only provide total energy consumption related to HVAC system, lighting, hot water, and appliances. While fine-grained data may be available in some computer tools, the process for obtaining these data is time-consuming, error-prone, and requires software-related skills. This paper explains a developed tool that contributes in automation of building energy simulation and providing fine-grained outputs by using Building Information Modeling (BIM) and modified source code of energy simulation tools such as EnergyPlus and OpenStudio. This tool, which is referred to as ABEMAT (Automated Building Energy Modeling and Assessment Tool), receives gbXML file and provides users with the amount of heat transfer through every single building envelope component such as windows, doors, and walls through an automated process. ABEMAT's and EnergyPlus advanced outputs are compared for validation; the latter being a time consuming process and error-prone, which requires software-related skills compared to ABEMAT. Results showed similar findings indicating the functionality of ABEMAT in providing fine-grained outputs. [ABSTRACT FROM AUTHOR]

Grout is widely used in bonded post-tensioned bridge construction as an anti-corrosive material for protecting the steel strands. Several occurrences of tendon failures in U.S. bridges, however, have led to an interest in unbonded tendons where a flexible filler, such as wax, grease, or gel, is injected into the tendon duct instead of cement grout. In general, the consistency of these flexible fillers in ambient temperature falls within the realm of semi-solids and, thus, they are not readily injectable without preheating. A major concern with flexible filler injection is, therefore, maintaining an adequately elevated filler temperature to keep the material’s viscosity sufficiently low for complete filling of the duct and to avoid a blockage that might result in a burst pipe or duct. This paper presents a simplified heat transfer model that computes the decrease in temperature of the moving filler front during injection as it cools while interacting with the surrounding strands and duct. The proposed model has been validated by multiple mockup experiments conducted with different filler materials and injection rates. A comprehensive parametric study has been conducted to determine the sensitivity of the filler front temperature to several practical factors, such as effective strand surface area, tendon length, injection rate, ambient temperature, injection temperature, and number of strands in a tendon system. The required minimum injection pressure for different flow velocities and tendon lengths has also been determined. The experimental results confirm the model’s applicability to a wide range of tendon lengths and strand patterns, and its usefulness in determining tendon constructability. [ABSTRACT FROM AUTHOR]

The paper summarizes the relative influence of different pavement thermophysical properties on the thermal response of pavement cross sections and how their relative behavior changes in different climatic regions. A simplified one-dimensional (1D) heat-flow modeling tool was developed to achieve this by using a finite difference solution method for studying the dynamic temperature profile within pavement constructions. This approach allows for a wide variety and for daily varying climatic conditions to be applied, where limited or historic thermophysical material properties are available, and permits the thermal behavior of the pavement layers to be accurately modeled and modified. The model was used with available thermal pavement materials properties and with properties determined specifically for the study reported in this paper. The pavement materials included in the study comprised both conventional bituminous and cementicious mixes and unconventional mixtures that allowed a wide range of densities, thermal conductivities, specific heat capacities, and thermal diffusivities to be investigated. Initially, the model was validated against in situ pavement data collected in the United States in five widely differing climatic regions. It was found to give results at least as good as others available from more computationally expensive approaches such as two-dimensional (2D) and three-dimensional (3D) finite-element (FE) commercial packages. The model was then used to compute the response for the same locations where the thermal properties had been changed by using some of the unconventional pavement materials. This revealed that reduction of the temperature range by several degrees was easily possible (with implications for reduction of rutting, fatigue, and the urban heat island effect) and that depth of penetration of peak temperatures was also achievable (with implications for winter freeze and thaw). However, the results showed that there was little opportunity to displace the peak temperatures in time. [ABSTRACT FROM AUTHOR]

The objective of this U.S.-Japan joint seminar series is to provide a cross-disciplinary and international forum for discussing and identifying outstanding science and technology issues in the area of nanoscale thermophysics and energy conversion and to foster collaboration among researchers in these areas. The first of this seminar series, championed by the late Professors Chang-Lin Tien and Kunio Hijikata, was held in Kanazawa, Japan, in June of 1993. Subsequent meetings have been held every three years, alternating venues between the United States and Japan. The Sixth U.S.-Japan Joint Seminar on Nanoscale Transport Phenomena—Science and Engineering was held in Boston, Massachusetts, July 13-16, 2008, and was organized by Professors Gang Chen from MIT, Fushinobu Kazuyoshi from Tokyo Institute of Technology, Shigeo Maruyama from Tokyo University, and Pamela Norris from University of Virginia. Nearly 100 scientists participated in the seminar. (The agenda of the seminar is attached at the end at this report[14].) The seminar included keynote sessions and invited sessions, as well as a dedicated poster session of selected presentations from an open call for papers. All papers presented in the regular sessions, the invited sessions, were upon invitation by the organizers. Invited sessions used a mixed form of communication: each speaker gave a 5-minute summary of his work followed by a 30-minute poster session of just the papers summarized orally, and then these speakers came back to the podium, serving as panelists to answer questions regarding their papers and session themes. This format offered good opportunities for the presenters to discuss their work with the participants. Reports for each session were summarized by session chairs. Following is a brief summary of the sessions. [ABSTRACT FROM AUTHOR]

The paper is part of a larger study, in which the author investigates the effects of radiant heat transfer from exterior shading devices on the surface temperatures of glass using an experimental setup at the Solar Laboratory at Arizona State University, Arizona, USA. Shading devices play an important role in controlling the amount of direct solar radiation entering the interior of a building. Designers provide various material alternatives while designing these exterior-shading devices. The main idea is to improve the aesthetic appearance of the building facade while at the same time providing an efficient shading system to the fenestration. One important effect that is overlooked by most of the currently available whole building simulation tools is the long-wave radiant (re-radiation) effect these shading devices have on the glass temperatures. The paper investigates the radiant effect using sunshades made of three different materials and compares the effectiveness of RADTHERM (a simulation tool used to simulate the experiment). [Copyright &y& Elsevier]

Abstract: This paper presents an analysis of heat-transfer to supercritical water in bare vertical tubes. A large set of experimental data, obtained in Russia, was analyzed and a new heat-transfer correlation for supercritical water was developed. This experimental dataset was obtained within conditions similar to those in supercritical water-cooled nuclear reactor (SCWR) concepts. The experimental dataset was obtained in supercritical water flowing upward in a 4-m long vertical bare tube with 10-mm ID. The data were collected at pressures of about 24MPa, inlet temperatures from 320 to 350°C, values of mass flux ranged from 200 to 1500kg/m2 s and heat fluxes up to 1250kW/m2 for several combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudocritical temperature. A dimensional analysis was conducted using the Buckingham Π-theorem to derive the general form of an empirical supercritical water heat-transfer correlation for the Nusselt number, which was finalized based on the experimental data obtained at the normal and improved heat-transfer regimes. Also, experimental heat transfer coefficient (HTC) values at the normal and improved heat-transfer regimes were compared with those calculated according to several correlations from the open literature, with CFD code and with those of the proposed correlation. The comparison showed that the Dittus–Boelter correlation significantly overestimates experimental HTC values within the pseudocritical range. The Bishop et al. and Jackson correlations tended also to deviate substantially from the experimental data within the pseudocritical range. The Swenson et al. correlation provided a better fit for the experimental data than the previous three correlations at low mass flux (∼500kg/m2 s), but tends to overpredict the experimental data within the entrance region and does not follow up closely the experimental data at higher mass fluxes. Also, HTC and wall temperature values calculated with the FLUENT CFD code might deviate significantly from the experimental data, for example, the k–ɛ model (wall function). However, the k–ɛ model (low Reynolds numbers) shows better fit within some flow conditions. Nevertheless, the proposed correlation showed the best fit for the experimental data within a wide range of flow conditions. This correlation has an uncertainty of about ±25% for calculated HTC values and about ±15% for calculated wall temperature. A final verification of the proposed correlation was conducted through a comparison with other datasets. It was determined that the proposed correlation closely represents the experimental data and follows trends closely, even within the pseudocritical range. Finally, a recent study determined that in the supercritical region, the proposed correlation showed the best prediction of the data for all three sub-regions investigated. Therefore, the proposed correlation can be used for HTC calculations in SCW heat exchangers, for preliminary HTC calculations in SCWR fuel bundles as a conservative approach, for future comparison with other datasets and for the verification of computer codes and scaling parameters between water and modelling fluids. [Copyright &y& Elsevier]

Fuel economy improvement on medium-duty tactical truck has and continues to be a significant initiative for the U.S. Army. The focus of this study is the investigation of Automated Manual Transmissions (AMT) and mild hybridization powertrain that have potential to improve the fuel economy of the 2.5-ton cargo trucks. The current platform uses a seven-speed automatic transmission. This study utilized a combination of on-road experimental vehicle data and analytical vehicle modeling and simulation. This paper presents the results of (1) establishment of a validated, high fidelity baseline analytical vehicle model, (2) modeling and simulation of two AMTs and their control strategy, (3) optimization of transmissions shift schedules, and (4) modeling and simulation of engine idle stop/start and Belt-Integrated-Starter-Generator (B-ISG) systems to improve the fuel economy. The fuel economy discrepancy between experimental average and the baseline simulation result was 2.87%. The simulation results indicated a 14.5% and 12.2% fuel economy improvement for the 10-speed and 12-speed AMT respectively. A stop/start system followed by a B-ISG mild hybrid system incorporating regenerative braking was estimated to improve fuel economy 3.39% and 10.2% respectively. [ABSTRACT FROM AUTHOR]

Abstract: Several advanced He-cooled W-alloy divertor concepts have been considered recently for power plant applications. They range in scale from a plate configuration with characteristic dimension of the order of 1m, to the ARIES-CS T-tube configuration with characteristic dimension of the order of 10cm, to the EU FZK finger concept with characteristic dimension of the order of 1.5cm. The trend in moving to smaller-scale units is aimed at minimizing the thermal stress under a given heat load; however, this is done at the expense of increasing the number of units, with a corresponding impact on the reliability of the system. The possibility of optimizing the design by combining different configurations in an integrated design, based on the anticipated divertor heat flux profile, also has been proposed. Several heat transfer enhancement schemes have been considered in these designs, including slot jet, multi-hole jet, porous media and pin arrays. This paper summarizes recent US efforts in this area, including optimization and assessment of the different concepts under power plant conditions. Analytical and experimental studies of the concepts and cooling schemes are presented. Key issues are identified and discussed to help guide future R&D, including fabrication, joining, material behavior under the fusion environment and impact of design choice on reliability. [Copyright &y& Elsevier]

Abstract: A general estimate shows that 80% of communities across the United States receive their goods exclusively by transport trucks, of which a significant number are climate-controlled because they carry perishable goods, pharmaceutical items and many other temperature-sensitive commodities. Keeping the inside of a truck trailer at a constant temperature and relative humidity requires exact amounts of heat and/or moisture management throughout the shipment period, which is regulated via small refrigeration units, placed outside the truck, that operate by burning fuel. These trucks, known as refrigerated truck trailers, are the focus of this paper. In the research presented herein, the conventional method of insulation of the refrigerated truck trailer was modified using phase change materials (PCMs). The limited research carried out in refrigerated transport compared to other refrigeration processes has left spaces for innovative solutions in this area. The research investigated the inclusion of paraffin-based PCMs in the standard trailer walls as a heat transfer reduction technology. An average reduction in peak heat transfer rate of 29.1% was observed when all walls (south, east, north, west, and top) were considered. For individual walls, the peak heat transfer rate was reduced in the range of 11.3–43.8%. Overall average daily heat flow reductions into the refrigerated compartment of 16.3% were observed. These results could potentially translate into energy savings, pollution abatement from diesel-burning refrigeration units, refrigeration equipment size reduction, and extended equipment operational life. The research and its results will help to better understand the scope of this technology. [Copyright &y& Elsevier]

Abstract: There are a number of future European Space Agency (ESA) and NASA planetary science missions that are in the planning or initial study phases, where the scientific objectives include determining the surface composition, measuring planetary surface heat flow and constraining planetary chronology. The University of Leicester is developing instrumentation for geophysical applications that include γ-ray spectroscopy, γ-ray densitometry and radiometric dating. This paper describes the modelling of a geophysical package, with the Monte Carlo code MCNPX, in order to determine the impact that a neutron source would have on in-situ composition measurements, radiometric dating and, in particular, trace element detection. The suitability of ∅ 2.54×2.54cm LaBr3(Ce) detectors in the geophysical package for in-situ missions was examined. 252Cf, Am–Be and Pu–Be neutron sources were compared in a trade-off study to determine mission suitability, potential for thermal and electric power production, mass and shielding requirements. This study is linked to a parallel examination of the suitability of radioisotope thermal generators for in-situ planetary science applications. The aim of the modelling was to optimise the source type and detector geometry in order to measure the elemental peaks of interest with a precision of 10% or better based on the Poisson statistics of the detected counts above background. [Copyright &y& Elsevier]

Abstract: Numerous Probabilistic Risk Assessments (PRAs) have shown that fire is a major contributor to Nuclear Power Plant (NPP) risks. However, prediction and estimation of the likelihood of fire-induced damage to electrical cables and circuits and their potential effects on the safety of the NPPs are still a practical challenge, particularly because of the lack of physics-based models with which to perform consistent and objective assessments. This paper contains a discussion of two models – the heat transfer and the IR “K-factor” models – to estimate the likelihood of fire-induced cable damage given a specified fire profile. The results of this research will help to (1) develop a consistent framework to estimate the likelihood of fire-induced cable failure modes, and (2) develop some guidance to evaluate and/or reduce the risks associated with these failure modes in existing and new NPPs. The models are developed (i.e., their parameters are estimated) based on the test data from various fire damage tests sponsored by the nuclear industry and the U.S. Nuclear Regulatory Commission (NRC). Among the models evaluated, the physics-based heat transfer model is promising because it takes into account the properties and characteristics of the cables and cable materials and the characteristics of the thermal insult. This model can be used to estimate the probability of cable damage (P CD ) under different thermal conditions. [Copyright &y& Elsevier]

An apparent error was detected in the calculation of windchill equivalent temperatures (WCETs) in the “new” chart and corresponding equation that were adopted in 2001 by the weather services in the United States and Canada. The problem is caused by significant discontinuities in WCETs at the assumed “calm” wind speed condition of 1.34 m s-1. As a result, published WCETs are not equal to, as they should be by definition, but are lower than air temperatures at the assumed calm wind speed condition. This inconsistency further propagates to higher wind speeds beyond the assumed calm condition. In this paper, a straightforward correction is proposed to circumvent these inconsistencies of the new windchill. The proposed correction makes this transition gradual rather than abrupt by applying it to the expression used for estimating the effects of wind on the convective heat exchange coefficient between humans and their cold and windy environment. [ABSTRACT FROM AUTHOR]

MELCOR, SCDAP/RELAP5, MAAP4 are three representative U.S. computer codes that are being most widely used for the integral analysis of core melt accident progression and the resultant lower head response expected at the reactor lower plenum such as the accident that took place in the TMI-2: the first two are NRC codes and the last one is an industrial code. However, their capabilities in predicting core melt accident progression and lower head response differ substantially at each phase of the lower plenum accident progression, due to the different modeling assumptions involved in various initial and boundary conditions, different debris bed configurations and heat transfer correlations, different model parameters and numerical schemes. The main objectives of this paper are to give (1) some insights into the aforementioned questions through a qualitative comparison of functional aspects of the lower head models employed in the three U.S. severe accident codes and (2) some potential areas that should be taken into account for further modeling of the present lower head models. [Copyright &y& Elsevier]