Lithium bromide-mediated reaction performance enhancement of a chemical heat-storage material for magnesium oxide/water chemical heat pumps

The reaction performance enhancement of a chemical heat-storage material for a magnesium oxide/water chemical heat pump was discussed. A new composite, denoted as EML, was developed by mixing pure magnesium hydroxide with lithium bromide and expanded graphite, which were employed as reactivity and h...

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Bibliographic Details
Published in:Applied thermal engineering 2014-02, Vol.63 (1), p.170-176
Main Authors: Myagmarjav, Odtsetseg, Ryu, Junichi, Kato, Yukitaka
Format: Article
Language:English
Subjects:
Applied sciences
Chemical heat pump
Dehydration
Energy
Energy. Thermal use of fuels
Exact sciences and technology
Expanded graphite
Heat pumps
Heat transfer
Hydrates
Hydration
Lithium
Lithium bromide
Magnesium hydroxide
Magnesium oxide
Performance enhancement
Theoretical studies. Data and constants. Metering
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Summary:The reaction performance enhancement of a chemical heat-storage material for a magnesium oxide/water chemical heat pump was discussed. A new composite, denoted as EML, was developed by mixing pure magnesium hydroxide with lithium bromide and expanded graphite, which were employed as reactivity and heat transfer enhancers, respectively. With respect to pure magnesium hydroxide powder, the EML composite showed higher reaction rates for dehydration and hydration transformations; further, the EML could dehydrate and hydrate at the same reaction temperature (200 °C). Addition of LiBr was found to decrease the estimated activation energy in the dehydration. The heat output capacity of the EML composite calculated at a hydration temperature of 110 °C was 1405.3 kJ kg−1, which was higher than that of pure MgO. It was established that the newly developed EML composite is a promising candidate for novel chemical heat-storage materials for chemical heat pumps at working temperatures of 200–300 °C. •A new chemical heat storage material, donated as EML, was developed.•EML composite made from pure Mg(OH)2, expanded graphite and lithium bromide.•LiBr was capable of being a reactivity enhancer.•EML composite could dehydrate and hydrate at the same reaction temperature (200 °C).•The heat out capacity of the EML composite was larger than that of pure Mg(OH)2.
ISSN:1359-4311
DOI:10.1016/j.applthermaleng.2013.10.045