Investigating Thermal Hydraulics Performance of a New Test Section Designed for the LSTL FLiNaK Using CFD
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Kappes, Ethan↗
SEARCH · Engineering Papers
Results for “Thermal performance”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Energy Performance of Awnings in Residential Buildings
Residential buildings consume approximately 20% of the total primary energy in the United States. More than 50% of this energy is spent in heating, cooling, and lighting these buildings. Solar heat gain is one of the largest and most variable sources of cooling load in these buildings, while it can also provide passive heating during the heating season. Shading devices can be used to control the amount of solar heat gain in buildings. Various studies have considered how different shading devices and their applications affect energy and occupant comfort in buildings. However, most of these studies were limited to planar shading devices such as roller shades, cellular shades, and blinds. Although some theoretical studies have been performed for awnings, the energy performance of awnings has rarely been studied via either energy simulation or field measurement. In this study, the authors evaluated the energy performance of typical operable awnings by using field data, aided by simulation. Awnings were installed on a real house, and measurements were performed to evaluate the thermal performance of the awning. The measured data were then used to develop a calibrated energy model and evaluate the awning’s energy performance. The annual simulation of the building model used showed that awnings left in the closed position from April to September can reduce annual HVAC energy consumption by 15% compared with a building without any shades. The validated model was used in US Department of Energy prototype buildings to evaluate awning energy performance in climate zones 1A through 4B via energy simulation. For these prototype buildings, energy savings of up to 1,034 kWh were achieved for a building with a conditioned floor area of 2,377 ft 2 .
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Development of a Cloud-Based Tool for Predicting Thermal Battery Performance: TABS v6
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Roberts, Scott Alan↗
Development of a Cloud-Based Tool for Predicting Thermal Battery Performance: TABS v6
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Roberts, Scott Alan↗
Evaluation of Cement Mechanical Performance in Thermal Storage Wells
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15 GEOTHERMAL ENERGY↗
Insulation or Irradiance: Exploring Why Bifacial Photovoltaics Run Hot
Bifacial photovoltaics are predicted to become the dominant device architecture over the next couple of years, but their thermal performance is not yet well understood. In this study, we model the thermal effects of different backside lamination materials on the performance of bifacial PERC cells. Glass-glass laminated cells were found to operate hotter than equivalent glass-polymer backsheet packed cells. This was solely due to the increased absorption of rear side incident light.
bifacial↗
Impact of Mass Wood Walls on Building Energy Use, Peak Demand, and Thermal Comfort
Thermal mass moderates indoor temperatures, allowing the heating, ventilation, and air conditioning (HVAC) system to operate more efficiently during peak hours. Cross-Laminated Timber (CLT) and other mass wood products provide thermal mass to the building envelope in a lighter and more environmentally friendly form than concrete. However, the influence of CLTs on heating and cooling energy, peak energy demand, and the indoor climate is not well-known. This project was formed to find the energy efficiency benefits of mass timber structures. The objectives were to (1) test the thermal performance of insulated mass wall structures in controlled laboratory conditions, (2) validate simulation models to expand performance to natural climatic conditions, (3) isolate the impact of the thermal properties of wood (thermal mass, thermal conductivity, moisture storage) on heating and cooling energy use and peak energy demand, and to optimize the performance. Currently, the designs used for CLT buildings have focused on structural and fire issues, and they do not consider the thermal mass benefits. Therefore, the thermal performance is not necessarily optimized.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
The hygrothermal performance of continuous and cavity wood fiber insulation
Wood fiber insulation is an emerging material known for its effective thermal performance and moisture management properties, making it a compelling alternative to conventional insulation. Its vapor permeability and ability to regulate indoor humidity contribute to improved building durability and comfort, particularly in varying climate conditions. The goal of this project is to characterize the hygrothermal performance of a new wood fiber insulation product line in U.S. climate zones and to facilitate the design and construction of the product in residential and light commercial building envelopes. This study investigates the thermal and hygrothermal performance of wood fiber insulation, both as continuous and cavity insulation. The research employs an exhaustive simulation task and an environmental chamber test of a wood fiber insulation. Over 400 simulations were conducted to study the hygrothermal characteristics of bio-based wood fiber insulation in various building envelope configurations across four climate zones. Environmental chamber tests were conducted under controlled winter conditions representative of Climate Zone 5A (Chicago, IL) to complement the simulation results. The chamber tests focused on the hygrothermal performance of the wood fiber insulation and the sheathing board to assess the insulation's ability to manage moisture in a cold climate. Simulation and environmental chamber test results were analyzed to evaluate the insulation's consistency and efficacy across diverse climatic zones. Results show that with a proper moisture control strategy, both cavity and continuous wood fiber insulation can work properly in both new and retrofit constructions.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Performance of Windows in Walls With Continuous Insulation
Window openings in walls are a significant contributor to poor thermal performance because of thermal bridging through the framing members (e.g., studs, joists, plates, bracing) and because windows lack the thermal properties of insulation. This report, Performance of Windows in Walls with Continuous Insulation , explores the common method for installing windows in walls with continuous insulation and presents acceptance criteria for evaluating the performance of windows installed in walls with and without continuous insulation.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Thermal and mechanical performance of gypsum composites containing fly ash cenosphere encapsulated phase change materials
Utilizing phase change materials (PCMs) within construction materials improves the thermal energy storage capabilities in the built environment. Notably, integrating PCMs into drywalls presents a promising avenue to reduce building energy use. However, incorporating PCMs into drywalls poses challenges, particularly reduced mechanical properties and workability limitations as it can adversely affect the hardening and cohesiveness of gypsum composites. To address these challenges, this study explores a novel strategy to incorporate PCMs into gypsum composites through fly ash cenosphere-encapsulated PCM, namely CenoPCM, aiming to enhance the mechanical properties and thermal conductivity over existing commercial counterparts. An experimental program was conducted to study the impact of the inclusion of CenoPCM on the mechanical and thermal performance of gypsum composites, and the results were compared to those of commercially available polymerencapsulated PCM benchmark (Micronal). The findings highlighted that PCM-charged samples exhibited up to 95.90 J/g (CenoPCM) of latent heat with 70 % CenoPCM loading. The results of mechanical tests also showed that CenoPCM outperformed its polymer-encapsulated counterpart, achieving 55 % higher mechanical strength on average. Here, this improvement is attributed to the rigid shell of fly ash cenosphere (FAC) serving as a PCM carrier, providing a skeleton-like structure to gypsum composites for higher load-bearing capacity. Additionally, hotbox tests demonstrated that the CenoPCM-charged wall panels yielded a 20 % higher thermal conductivity and a 22 % increased time lag compared to Micronal PCM-charged panels, indicating its potential to shift the peak load in buildings.
Ceno PCM↗
Thermal energy storage in concrete: Review, testing, and simulation of thermal properties at relevant ranges of elevated temperature
This study examines the thermal performance of concrete used for thermal energy storage (TES) applications. The influence of concrete constituents (aggregates, cementitious materials, and fibers) on the thermal conductivity and specific heat are summarized based on literature and via experimentation at elevated temperatures. It is indicated that concrete with siliceous aggregate, low water/cement ratios, and steel fibers produces better overall thermal properties. The results of literature review and laboratory testing are used for numerical simulation to evaluate the impact of concrete thermal property variability on TES capabilities. The TES module consists of the heat exchanger and surrounding concrete as the storage media. Both idealized cases without heat loss and realistic cases with insulation and heat losses are considered. Furthermore, the result shows that conventional concrete mixes can be tailored to decrease the module charge/discharge durations and increase the amount of thermal energy storage.
25 ENERGY STORAGE↗
Advanced Power Electronics Designs - Reliability and Prognostics (Keystone Project 1)
The primary deliverable for this project will be to construct a power electronics package utilizing an organic electrically insulating substrate material with a direct chip-to-chip interconnect technology and demonstrate superior thermal performance and greater reliability under thermal cycling, thermal aging, vibration, power cycling, and electrical high-potential evaluation over traditional packages.
47 OTHER INSTRUMENTATION↗
Advanced Power Electronics Designs - Reliability and Prognostics (Keystone Project 1)
The primary deliverable for this project will be to construct a power electronics package utilizing an organic electrically insulating substrate material with a direct chip-to-chip interconnect technology and demonstrate superior thermal performance and greater reliability under thermal cycling, thermal aging, vibration, power cycling, and electrical high-potential evaluation over traditional packages.
ADVANCED PROPULSION SYSTEMS↗
Advanced Power Electronics Designs - Reliability and Prognostics (Keystone Project 1)
The primary deliverable for this project will be to construct a power electronics package utilizing an organic electrically insulating substrate material with a direct chip-to-chip interconnect technology and demonstrate superior thermal performance and greater reliability under thermal cycling, thermal aging, vibration, power cycling, and electrical high-potential evaluation over traditional packages.
ADVANCED PROPULSION SYSTEMS,ENGINEERING↗
Advanced Packaging Designs
The primary deliverable for this project will be to construct a power electronics package utilizing an organic, electrically insulating substrate material and demonstrate superior thermal performance and greater reliability under thermal cycling, thermal aging, vibration, power cycling, and electrical high-potential evaluation over traditional packages.
ENGINEERING↗
A computational analysis of effective R-values of buried ducts – the dynamic performance of buried ducts
Here, this paper evaluates the thermal performance of ducts partially or fully buried in loose-fill attic insulation. The overall thermal resistance between the ducts and the attic is referred to as an effective R-value. This paper shows a strong dependency of assumed attic temperature on the effective R-value. Based on the results, the effective R-value can be about twice as much with an attic temperature of 130 °F [54.4 °C], compared to when the attic temperature is 80 °F [26.7 °C]. Thus, this paper provides a polynomial regression equation based on a large set of simulations to determine the effective R-value of buried ducts depending on attic temperature and whether the HVAC system runs in cooling or heating mode. Further, the work presented in this paper investigated the potential impact of convective airflow within the attic insulation, particularly around the ducts. The analysis was based on computational fluid dynamics (CFD) and indicated that convectional forces are presented around the exterior surface of the ducts, but with negligible impact on the overall heat balance between the duct and the attic space.
97 MATHEMATICS AND COMPUTING↗
Demonstration and Evaluation of Lightweight High Performance Secondary Windows
Eight secondary windows (single-pane and double-pane) were installed at Building 53 of the Denver Federal Center in Colorado as part of a demonstration project to assess their thermal performance, life cycle costs, and deployment potential for use in conjunction with existing, older single-pane windows. The U.S. Department of Energy's National Renewable Energy Laboratory performed several different evaluations to assess the viability of the secondary windows for GSA applications. Some assessments were performed with models, while others required onsite evaluations including time series measurements.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Performance of Windows in Walls With Continuous Insulation
Window openings in walls are a significant contributor to poor thermal performance because of thermal bridging through the framing members (e.g., studs, joists, plates, bracing) and because windows lack the thermal properties of insulation. Window installation guidance for walls with continuous insulation (CI) is critical for continued market growth of this energy efficiency technology. This research project offers window manufacturers a starting point and a potential path toward developing installation instructions for windows over CI. The objectives of the research include evaluating the common method for installing windows in walls with CI, as well as establishing acceptance criteria for evaluating the performance of windows installed in walls with and without CI. The research measures: 1. The performance characteristics (e.g., water management, structural integrity) of windows in walls without CI. 2. The performance of different thicknesses and types of CI used in walls. 3. The performance of different types of window assemblies (e.g., double-hung windows, mulled double-hung windows, mulled casement windows, and slider windows) installed over CI. 4. The performance of window flange types (e.g., rigid mounting and less robust flanges) installed over CI. 5. Installing windows over CI using baseline installation instructions versus window manufacturer installation instructions. The project’s sequential testing protocol consists of the following: • A water penetration resistance testing adapted from two ASTM standards: E331 (uniform static air pressure in four steps) and E547 (cyclic static air pressure) • A temperature cycling adapted from ASTM E2264 Method B (convective hot air) • A service condition wind loading test adapted from ASTM E330 • A six-month vertical displacement observation phase prior to the structural performance testing • A final water penetration resistance test after vertical displacement observation • A structural performance test adapted from ASTM E330. Key research findings include: • The criterion for passing a water penetration resistance test is that there is no water overflowing at the interior face of the studs. If there is any bubbling or slight pooling of water at the sill, then it must recede after the pressure is removed. Excessive leakage and/or water leaking to the interior face of the framing around the window constitutes a failure. • All single double-hung windows installed directly to lumber or over oriented strand board passed all test protocols. • For most wall specimens, the test results showed that the use of foam sheathing did not affect the performance of the window for water leakage. • All wall specimens underwent temperature cycling. The results indicated that temperature cycling had little to no effect on windows installed over foam sheathing. • For wall specimens that underwent six-month vertical displacement monitoring, the results showed that windows installed over foam sheathing do not sag over time. • The single-hung and double-hung windows installed using window manufacturer installation instructions passed the structural performance test, compared to failures observed in windows that were installed using generic installation instructions. The generic and manufacturer installation methods differed on the following construction details: type of fasteners, fastening patterns on the flanges, and window shimming details. • Additional testing is required to determine methods to improve structural pressure performance of slider windows. Potential solutions that would require additional testing may include fastener spacing, different types of fasteners, masonry window clips, construction adhesive, foam sealant, stronger window flange material, and/or straps.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗