329 research outputs found

    Thermal energy storage implementation using phase change materials for solar cooling and refrigeration applications

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    The final goal of this study is to implement and to test a thermal energy storage (TES) system using different phase change materials (PCM) for solar cooling and refrigeration applications. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly by three parts: heating system, cooling system, and different storage tanks. The pilot plant uses synthetic thermal oil as heat transfer fluid (HTF) and has a working temperature range from 100 潞C to 400 潞C. Two different PCM were selected after a deep study of the requirements of a real solar cooling plant and the available materials in the market, finally d-mannitol with phase change temperature of 167 潞C and hydroquinone which has a melting temperature of 172.2 潞C were used.The work is partially funded by the Spanish government (ENE2011-22722). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2009 SGR 534). Antoni Gil would like to thank the Col路legid鈥橢nginyers Industrials de Catalunya for his research appointment. Eduard Or贸 would like to thank the University of Lleida for his research fellowship

    A class of elementary particle models without any adjustable real parameters

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    Conventional particle theories such as the Standard Model have a number of freely adjustable coupling constants and mass parameters, depending on the symmetry algebra of the local gauge group and the representations chosen for the spinor and scalar fields. There seems to be no physical principle to determine these parameters as long as they stay within certain domains dictated by the renormalization group. Here however, reasons are given to demand that, when gravity is coupled to the system, local conformal invariance should be a spontaneously broken exact symmetry. The argument has to do with the requirement that black holes obey a complementarity principle relating ingoing observers to outside observers, or equivalently, initial states to final states. This condition fixes all parameters, including masses and the cosmological constant. We suspect that only examples can be found where these are all of order one in Planck units, but the values depend on the algebra chosen. This paper combines findings reported in two previous preprints, and puts these in a clearer perspective by shifting the emphasis towards the implications for particle models.Comment: 28 pages (incl. title page), no figure

    Duality between a deterministic cellular automaton and a bosonic quantum field theory in 1+1 dimensions

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    Methods developed in a previous paper are employed to define an exact correspondence between the states of a deterministic cellular automaton in 1+1 dimensions and those of a bosonic quantum field theory. The result may be used to argue that quantum field theories may be much closer related to deterministic automata than what is usually thought possible. Version 2 had a minor typo corrected and notation was made more consistent.Comment: 18 pages (incl. Title page). No figure