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Thermal protection of a ground layer with phase change materials / X. Duan in Journal of heat transfer, Vol. 132 N° 1 (Janvier 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 1 (Janvier 2010) . - pp. [011301/9] Titre : Thermal protection of a ground layer with phase change materials Type de document : texte imprimé Auteurs : X. Duan, Auteur ; G. F. Naterer, Auteur Article en page(s) : pp. [011301/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Phase  change  material  Ground  heat  transfer  Insulation  Foundation  Permafrost Index. décimale : 536 Chaleur. Thermodynamique Résumé : Conventional ground surface insulation can be used to protect power line foundations in permafrost regions from the adverse effects of seasonal freezing and thawing cycles. But previous studies have shown ineffective thermal protection against the receding permafrost with conventional insulation. In this paper, an alternative thermal protection method (phase change materials (PCMs)) is analyzed and studied experimentally. Seasonal ground temperature variations are estimated by an analytical conduction model, with a sinusoidal ground surface temperature variation. A compensation function is introduced to predict temperature variations in the foundation, when the ground surface reaches a certain temperature profile. Measured data are acquired from an experimental test cell to simulate the tower foundation. With thermal energy storage in the PCM layer, the surface temperature of the soil was modified, leading to changes in temperature in the foundation. Measured temperature data show that the PCM thermal barrier effectively reduces the temperature variation amplitude in the foundation, thereby alleviating the seasonal freezing and thawing cycles. Different thermal effects of the PCM thermal barrier were obtained under different air temperature conditions. These are analyzed via melting degree hours and freezing degree hours, compared with a critical number of degree hours. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Thermal protection of a ground layer with phase change materials [texte imprimé] / X. Duan, Auteur ; G. F. Naterer, Auteur . - pp. [011301/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 1 (Janvier 2010) . - pp. [011301/9] Mots-clés : Phase  change  material  Ground  heat  transfer  Insulation  Foundation  Permafrost Index. décimale : 536 Chaleur. Thermodynamique Résumé : Conventional ground surface insulation can be used to protect power line foundations in permafrost regions from the adverse effects of seasonal freezing and thawing cycles. But previous studies have shown ineffective thermal protection against the receding permafrost with conventional insulation. In this paper, an alternative thermal protection method (phase change materials (PCMs)) is analyzed and studied experimentally. Seasonal ground temperature variations are estimated by an analytical conduction model, with a sinusoidal ground surface temperature variation. A compensation function is introduced to predict temperature variations in the foundation, when the ground surface reaches a certain temperature profile. Measured data are acquired from an experimental test cell to simulate the tower foundation. With thermal energy storage in the PCM layer, the surface temperature of the soil was modified, leading to changes in temperature in the foundation. Measured temperature data show that the PCM thermal barrier effectively reduces the temperature variation amplitude in the foundation, thereby alleviating the seasonal freezing and thawing cycles. Different thermal effects of the PCM thermal barrier were obtained under different air temperature conditions. These are analyzed via melting degree hours and freezing degree hours, compared with a critical number of degree hours. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Upgrading of waste heat for combined power and hydrogen production with nuclear reactors / C. Zamfirescu in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Titre : Upgrading of waste heat for combined power and hydrogen production with nuclear reactors Type de document : texte imprimé Auteurs : C. Zamfirescu, Auteur ; G. F. Naterer, Auteur ; I. Dincer, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Chlorine  Copper  Fission  reactor  cooling  Heat  pumps  Heat  recovery  Hydrogen  production  Waste  heat Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a new heat upgrading method that utilizes waste heat from nuclear reactors for thermochemical water splitting with a copper-chlorine (Cu–Cl) cycle. Through combined power, hydrogen, and oxygen generation, the exergy efficiency of a power plant can be significantly augmented. The heat rejected to the environment for moderator cooling, a relatively small amount of low pressure superheated steam and a small fraction of generated power, are extracted from the nuclear reactor and used to drive a Cu–Cl hydrogen plant. More specifically, the moderator heat transfer at ~80°C is used as a source to a newly proposed vapor compression heat pump with a cascaded cycle, operating with retrograde fluids of cyclohexane (bottoming cycle) and biphenyl (topping supercritical cycle). Additionally, the heat pump uses as input the heat recovered from within the Cu–Cl cycle itself. This heat is recovered at two levels: ~80–130°C and ~250–485°C. This heat input is upgraded up to 600°C by work-to-heat conversion and then used to supply the endothermic water splitting process. The extracted steam is fed into the Cu–Cl cycle and split into hydrogen and oxygen as overall products. Electricity is partly used for an electrochemical process within the Cu–Cl cycle, and also partly for the heat pump compressors. This paper analyses the performance of the proposed heat pump and reports the exergy efficiency of the overall system. The proposed system is about 4% more efficient than generating electricity alone from the nuclear reactor. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Upgrading of waste heat for combined power and hydrogen production with nuclear reactors [texte imprimé] / C. Zamfirescu, Auteur ; G. F. Naterer, Auteur ; I. Dincer, Auteur . - 2011 . - 09 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Mots-clés : Chlorine  Copper  Fission  reactor  cooling  Heat  pumps  Heat  recovery  Hydrogen  production  Waste  heat Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a new heat upgrading method that utilizes waste heat from nuclear reactors for thermochemical water splitting with a copper-chlorine (Cu–Cl) cycle. Through combined power, hydrogen, and oxygen generation, the exergy efficiency of a power plant can be significantly augmented. The heat rejected to the environment for moderator cooling, a relatively small amount of low pressure superheated steam and a small fraction of generated power, are extracted from the nuclear reactor and used to drive a Cu–Cl hydrogen plant. More specifically, the moderator heat transfer at ~80°C is used as a source to a newly proposed vapor compression heat pump with a cascaded cycle, operating with retrograde fluids of cyclohexane (bottoming cycle) and biphenyl (topping supercritical cycle). Additionally, the heat pump uses as input the heat recovered from within the Cu–Cl cycle itself. This heat is recovered at two levels: ~80–130°C and ~250–485°C. This heat input is upgraded up to 600°C by work-to-heat conversion and then used to supply the endothermic water splitting process. The extracted steam is fed into the Cu–Cl cycle and split into hydrogen and oxygen as overall products. Electricity is partly used for an electrochemical process within the Cu–Cl cycle, and also partly for the heat pump compressors. This paper analyses the performance of the proposed heat pump and reports the exergy efficiency of the overall system. The proposed system is about 4% more efficient than generating electricity alone from the nuclear reactor. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]