Search results for " Thermal"
showing 10 items of 492 documents
Improving thermoelectric performance of TiNiSn by mixing MnNiSb in the half-Heusler structure
2016
The thermoelectric properties of n type semiconductor, TiNiSn is optimized by partial substitution with metallic, MnNiSb in the half Heusler structure. Herein, we study the transport properties and intrinsic phase separation in the system. The Ti1-xMnxNiSn1-xSbx alloys were prepared by arc-melting and were annealed at temperatures obtained from differential thermal analysis and differential scanning calorimetry results. The phases were characterized using powder X-ray diffraction patterns, energy dispersive X-ray spectroscopy, and differential scanning calorimetry. After annealing the majority phase was TiNiSn with some Ni rich sites and the minority phases was majorly Ti6Sn5, Sn, and MnSn2…
Ab initiolattice dynamical studies of silicon clathrate frameworks and their negative thermal expansion
2014
The thermal and lattice dynamical properties of seven silicon clathrate framework structures are investigated with ab initio density functional methods (frameworks I, II, IV, V, VII, VIII, and H). The negative thermal expansion (NTE) phenomenon is investigated by means of quasiharmonic approximation and applying it to equal time displacement correlation functions. The thermal properties of the studied clathrate frameworks, excluding the VII framework, resemble those of the crystalline silicon diamond structure. The clathrate framework VII was found to have anomalous NTE temperature range up to 300 K and it is suitable for further studies of the mechanisms of NTE. Investigation of the displa…
Investigation on a Bio-Composite Material as Acoustic Absorber and Thermal Insulation
2020
In order to limit the anthropic emissions of CO2, research is currently investigating new materials for the building sector. The main purpose is the reduction in the embodied energy consumption, especially in the residential sector, and consequently the limitation of the direct and indirect utilization of fossil fuels, for the indoor heating, cooling, and ventilation services. Indeed, the residential sector is affected by a high energy demand, thus the choice of improved materials is fundamental to improve the sustainability. All phases: construction, building life, and dismantling are impacting in terms of resource and energy consumption, both associated with the emissions of pollutants in…
The effect of the axial heat transfer on space charge accumulation phenomena in HVDC cables
2020
To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating …
Fossil Fuel and Biofuel Boilers in Ukraine: Trends of Changes in Levelized Cost of Heat
2022
An increase in the share of renewables in heat supply systems is a promising direction to reach sustainable development goals and decarbonization. Decision makers should consider various factors, including energy market prices, the availability of biofuels, boiler and auxiliary equipment costs, logistic costs, and the taxation system. In the European Union, the energy crisis causes a rapid increase in fossil fuel prices. Moreover, the use of fossil fuels results in greenhouse gas emissions, which threatens the achievement of sustainable development goals. We studied the influence of the delivery cost and the value of environmental tax rates on the levelized cost of heat. Low-capacity boiler…
FEM Analysis: A Review of the Most Common Thermal Bridges and Their Mitigation
2022
The necessity to improve the energy saving potential of buildings is now a duty. European and national policies are being implemented to address the important decisions being made on this subject. For these reasons, several studies focus on this relevant topic. This paper review not only focusses on it but studies it in-depth. A commercial 3D simulation software was used to design a building sited in Palermo estimating the thermal losses before and after external envelope insulation. In particular, all the thermal bridges (TBs) were analysed with the finite element method (FEM) and mitigated with rock wool insulation. The paper shows the linear thermal transmittance difference and heat flux…
Detecting crop irrigation status in orchard canopies with airborne and ASTER thermal imagery
2007
This work provides a description of the research conducted to assess if ASTER satellite data enable the detection of the water status in orchard tree crops. Summer and winter TERRA-ASTER images were acquired over a study area of Seville in southern Spain over a 6-year period. 1076 olive orchards were monitored in this area, obtaining field location, area, tree density, and irrigation status information. Surface temperature images were obtained using the TES method and 0.5 m resolution panchromatic ortho-rectified imagery collected over the entire area to obtain vegetation cover. A comparison study of the temperature difference between orchards under different irrigation schemes is presented…
Temperature effects on the performances of the ATHENA X-IFU thermal filters
2016
The X-Ray Integral Field Unit (X-IFU) detector on-board ATHENA is an array of TES micro-calorimeters that will operate at ~50 mK. In the current investigated design, five thermal filters (TF) will be mounted on the cryostat shields to attenuate IR radiative load and avoid energy resolution degradation due to photon shot noise. Each filter consists of a thin polyimide film (~50 nm thick) coated with aluminum (~30 nm thick). Since the TF operate at different temperatures in the range 0.05-300 K, it is relevant to study how temperature affects their mechanical/optical performances (e.g. near edge absorption fine structures of the atomic elements in the filter material). Such results are crucia…
Thermal Filters for the ATHENA X-IFU: Ongoing Activities Toward the Conceptual Design
2016
ATHENA is the L2 mission selected by ESA to pursue the science theme “Hot and Energetic Universe.” One of the two focal plane instruments is the X-ray Integral Field Unit, an array of TES microcalorimeters operated at T $$<$$ 100 mK. To allow the X-ray photons focused by the telescope to reach the detector, windows have to be opened on the cryostat thermal shields. X-ray transparent filters need to be mounted on these open windows to attenuate the IR radiation from warm surfaces, to attenuate RF electromagnetic interferences on TES sensors and SQUID electronics, and to protect the detector from contamination. This paper reviews the ongoing activities driving the design of the X-IFU thermal …
Simultaneous measurement of temperature and strain in glass fiber/epoxy composites by embedded fiber optic sensors: II. Post-cure testing
2007
In this paper the use of fiber optic sensors embedded into GFRP laminates for structural health monitoring of thermo-mechanical loads is presented. The proposed sensing system, consisting of two coupled fiber Bragg grating (FBG) sensors, allows the simultaneous measurement of both temperature and strain by decoupling the change in reflected wavelength induced by temperature variations from that induced by either mechanical or apparent strain, with significant advantages either for monitoring the composite cure kinetics, as described in the accompanying paper (Part I), or for assessing the structural response to thermo-mechanical loads. Both thermal ramp and mechanical static/dynamic bending…