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Title:
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Determination of structural, thermodynamic and phase properties in the NA2S-H2O system for application in a chemical heat pump
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Author(s):
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Published by:
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Publication date:
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ECN
Energy Efficiency in Industry
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1-3-2002
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ECN report number:
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Document type:
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ECN-RX--02-009
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Article (scientific)
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Number of pages:
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32
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Published in: The paper is to be published in: Thermochimica Acta (Jan. 3003) (), , , Vol., p.-.
Abstract:
Structural, thermodynamic and phase properties in the Na2S-H2O systemfor application in a chemical heat pump have been investigated using
XRD, TG/DTA and melting point and vapour pressure determinations. Apart
from the known crystalline phases Na2S-9H2O, Na2S-5H2O and Na2S a new
phase Na2S-2H2O has been proven to exist. Na2S-½H2O is not a phase but
a 3:1 mixture of Na2S and Na2S-2H2O, presumably stabilised by very slow
dehydration kinetics. The vapour pressure-temperature equilibria of
the sodium sulphide hydrates have been determined and a consistent set
of thermodynamic functions for these compounds has been derived. XRD
measurements indicate the topotactic character of the transitions between
the hydration states.
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