Thermal energy can be stored in supercooled liquids where the material is in thermal equilibrium with its surroundings. The stored latent heat of fusion is released by triggering the crystallization ...of the supercooled substance. In this study, enthalpy–temperature curves including the effect of supercooling are measured for some well known supercooling salt hydrates (disodium hydrogen phosphate dodecahydrate, sodium acetate trihydrate and STL-47). A series of properties relevant for supercooling energy storage applications are identified, including the optimal working temperature range for the materials, temperature increase during crystallization as a function of degree of supercooling, available enthalpy at different temperatures, and fraction of enthalpy lost in the initial supercooling phase. The enthalpy–temperature curves are measured by a simple and inexpensive method.
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Radiative strength functions (RSFs) for the (56,57)Fe nuclei below the separation energy are obtained from the 57Fe(3He,alphagamma)56Fe and 57Fe(3He,3He'gamma)57Fe reactions, respectively. An ...enhancement of more than a factor of 10 over common theoretical models of the soft (E(gamma) less than or approximately equal 2 MeV) RSF for transitions in the quasicontinuum (several MeV above the yrast line) is observed. Two-step cascade intensities with soft primary transitions from the 56Fe(n,2gamma)57Fe reaction confirm the enhancement.
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A radiative cooling system consisting of unglazed flat plate radiators, water as heat carrier and a reservoir is presented. The radiators are twin-wall sheets made of a modified PPO ...(polyphenylenoxid) resin, which are proposed as low cost roof integrated modules. The thermal performance of a system with a radiator aperture area of 5.3 m
2 and reservoir volume of 280 l has been investigated in experiments for Oslo climate. A parameterisation for the cooling performance of a tilted radiator surface for clear and cloudy atmospheres is proposed and applied to model the experimental results. The impact of the tilt angle, the aperture area and the reservoir volume on the cooling performance has been studied in simulations. The feasibility of a radiative cooling system designed for a single-family house at southern latitudes has been modelled. Except for mid-summer ambient temperature and high relative humidity, the simulations show that the radiative cooling system seems to cover the demand.
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We present a new iterative procedure to extract the level density and the γ strength function from primary γ spectra for energies close up to the neutron binding energy. The procedure is tested on ...simulated spectra and on data from the
173
Yb
(
3
He,α)
172
Yb
reaction.
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A mechanical test is used to characterize the ageing process of a polymeric solar absorber as a consequence of exposure to high temperature. Specimens from the polymeric absorber sheet were exposed ...to different temperature and time conditions. Specimens were then tested using mechanical indentation to evaluate the damage level produced. Based on these measurements, this work proposes a model to predict degradation of the polymeric solar absorber during their service life. Model predictions are compared with results from a polymeric absorber exposed to outdoor conditions during two years.
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An indentation test is proposed to study the degradation of extruded polymeric solar absorbers. The thermal degradation caused by accelerated aging is investigated. The results are compared with the ...thermal and mechanical impacts during the operation of the solar collector.
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In this work, we have reviewed the Oslo method, which enables the simultaneous extraction of the level density and {gamma}-ray transmission coefficient from a set of particle-{gamma} coincidence ...data. Possible errors and uncertainties have been investigated. Typical data sets from various mass regions as well as simulated data have been tested against the assumptions behind the data analysis.
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Within this study, the aging behavior of a PPE
+
PS absorber material was investigated on the absorber component level. To indicate aging, characteristic mechanical values were determined by ...indentation tests of specimens taken from components and exposed to laboratory aging (140
°C in air, 80
°C in water) and service near outdoor aging conditions (stagnation in northern climate). In addition to the mechanical tests, the unaged and aged specimens were also characterized thermo-analytically via differential scanning calorimetry (DSC). The results indicate that reductions in both characteristic mechanical values of the indentation tests, i.e., load of the first transition and ultimate indentation, reflect at least some physical aging although chemical aging may also be of importance based on previous analytical investigations of laboratory aged polymer films. While laboratory aging in air at 140
°C and service exposure at a test facility in Oslo (N) under stagnation conditions led to a significant reduction in the mechanical indentation resistance, no influence of laboratory aging in water at 80
°C on the mechanical behavior of the absorber sheet was found. Depending on the ultimate failure criterion applied (reduction of characteristic mechanical values to 80% and 50%, respectively), the technical service life found for hot air laboratory and stagnation service conditions was found to be less than 51 and 159
h, respectively. As these durations are significantly below the estimated stagnation conditions accumulated in the desired operation lifetime for such a collector, the PPE
+
PS type investigated does not seem to be a proper material candidate for solar thermal absorbers. Finally, based on the results obtained, a relation between laboratory aging time in air at 140
°C and cumulated irradiation energy during exposure on the test facility in Oslo was established.
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9.
The unfolding of continuum γ-ray spectra Guttormsen, M; Tveter, T.S; Bergholt, L ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/1996, Volume:
374, Issue:
3
Journal Article
Peer reviewed
A new method for unfolding γ-ray spectra is described. The method is based on the fact that the contribution of Compton scattered γ-rays in the spectra is a slowly varying function of energy. Thus, ...the Compton part can be smoothed and subtracted from the original observed spectrum giving an unfolded spectrum with the same statistical fluctuations as the observed spectrum. In particular, we show that the method works very well for poor statistics continuum γ-ray spectra.
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A polymer solar heat collector was combined with single-crystal silicon PV cells in a hybrid energy-generating unit that simultaneously produced low temperature heat and electricity. The PV/T unit ...was tested experimentally to determine its thermal and photovoltaic performance, in addition to the interaction mechanisms between the PV and thermal energy systems. Thermal efficiency measurements for different collector configurations are compared, and PV performance and temperature readings are presented and discussed. An analytical model for the PV/T system simulated the temperature development and the performance of both the thermal and photovoltaic units.
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