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Experimental study on the influence of power steps on the thermohydraulic behavior of a natural circulation loop
No full textSingle phase natural circulation is a heat transfer mechanism of great interest in various energy systems, including solar heaters, nuclear reactors, geothermal power production, engine and computer cooling. The present paper deals with an experimental study on the influence of power steps on the behavior of a single-phase natural circulation loop. In particular two sets of experiments were performed: constant power and variable power. Several parameters such as the amplitude of power steps as well as the period of the oscillations were experimentally investigated. The runs at constant power were carried out at different power levels from 500 W to 3000 W. The experiments at variable power were carried out for the values of 500 W, 1000 W, and 2000 W. The amplitude of steps was ±50% or ±20% of the input power, whereas the period of the oscillations varied between 50 s and 7200 s. All tests, both at constant power and variable power, show always an unstable behavior, i.e., temperature oscillations across the heated sections occur in the fluid. Moreover, the amplitude and the frequency of the oscillations increase as the input power increases. The thermal inertia of the loop plays a role in case of smaller time steps
Sull’accumulo termico di pareti interne: valutazione della partecipazione al regine variabile per differenti sollecitazioni termiche
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Dynamic behaviour of a single-phase natural circulation loop : influence of heat sink temperature
No full textDynamic behaviour of a rectangular single-phase natural circulation loop: influence of loop inclination
No full textMeasurement of total hemispherical emittance and specific heat of aluminium and Inconel 718 by a calorimetric technique
No full textAn apparatus for the measurement of the total hemispherical emittance and specific heat of metals has been developed. The measurement principle is based on the calorimetric technique: the sample, heated by Joule effect and placed in a vacuum chamber, exchanges radiative heat transfer with the walls of the container, kept at a relatively low temperature. Emittance is deduced from the radiative heat transfer laws at the steady state. When the heating power is switched off, the specific heat of the sample can be recovered from the time history of the sample temperature during the cooling transient. Measurements have been performed on samples of aluminum Anticorodal alloy and Inconel 718 alloy under different surface conditions in the 350 –630 K range
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