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Schmidt, Dietrich Dietrich; Jóhannesson, Gudni Gudni. Optimised RC Networks Incorporated within Macro-Elements for Modelling Thermally Activated Building Constructions. Nordic Journal Of Building Physics: Acta Physica Aedificiorum, p. 1 -2, 2004.
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Número de Trabalhos: 4 (Nenhum com arquivo PDF disponível)
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Dados do autor na base InfoHab:
Número de Trabalhos: 3 (Nenhum com arquivo PDF disponível)
Citações: Nenhuma citação encontrada
Índice h: Indice h não calculado  
Co-autores: Nenhum co-autor encontrado

Abstract

This paper presents an effective modelling method for the thermal simulations of thermally activated building constructions or hybrid systems, and a scheme in which the resulting mathematical models can be implemented in a commonly used dynamic simulation computer program. The advantage of this method is the fact that only a limited number of nodes are required to obtain reliable results for the simulation. A general overview of the modelling method, based on an earlier conducted analysis (Schmidt and Jóhannesson 2002a), is provided and the modelling method is described in detail in presented case studies. A comparison between the new model and a derived analytic solution for a case example shows the quality of the model. The so-called macro element modelling method, MEM, is based on earlier research on the modelling dynamic heat flows in solid constructions with discrete resistances and capacitances (Jóhannesson 1981, Mao 1997, Akander 2000). Here, it has been expanded by the simultaneous modelling of heat carrier flows and used on a different class of constructions, thermally activated building constructions, such as hydronic floor and wall heating or hollow core slabs. As shown in an example in this paper, the MEM method is suitable for the dynamic simulations of thermally activated components in buildings. With the MEM model, the temperature variation of the heat carrier fluid is modelled correctly along the flow path with the assumption that the temperatures of the mass nodes of the construction vary stepwise linearly along the direction of the flow. The fluid’s temperature profile is calculated in quasi-steady state conditions. In the present stage this limits the model validity to cases in which the fluid’s flow-through time is shorter than the period of studied time variations. The results can be corrected when the actual flow through time is taken into account. The cases shown demonstrate the advantages of using MEM models to calculate even extreme time-dependent processes, such as switching the flow direction or steps in the inlet temperature or flow conditions. These are preferable to other known simplified models of thermally activated constructions in dynamic simulations. It has been demonstrated that the MEM method is generally suitable for modelling the dynamic behaviour of combined systems with a heat carrier flow and solid construction parts with substantial heat storage capacity.
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