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This paper and its future companion papers, were aimed to develop a set of efficient and accurate enough modular tools to build a simulation test bed for the stability analysis of interacting VAV (variable air volume air-conditioning system) control loops. By providing the correlation equations between the heat flow and temperature of the two opposite surfaces, the wall model was expected to link adjacent zones effectively and efficiently. In part 1, the development of an optimal simplified 3R2C (composed of three resistances and two capacitances) thermal network model of building envelope, i.e., the wall model, was descripted. The verification showed that the simplification of one-dimensional heat conduction through a typical wall of heavy construction was acceptable. The accuracy of the optimal simplified 3R2Cmodel was satisfying, and outperformed that of the optimal 4R3C model as well as two 3R2C models which were normally used in practical applications. First and foremost, the room dimensions of the test bed with the boundary conditions in numerical scheme were designed under the principle of similarity. After validation of the numerical scheme with the high-cited scaled experiment, a series of numerical test cases simulating the potential oscillations in practical applications, were conducted. Then, the long neglected concerned frequency range within which heat flow transfer through extern wall, was determined. Finally, the part of solid wall was separated with the part of indoor air, and was developed into a flexible wall module of 3R2C model based on frequency domain regression. [ABSTRACT FROM AUTHOR]

Abstract: This paper computes the thermal delay in multilayer systems. The heat transfer by conduction across multilayer systems under unsteady boundary conditions is simulated using analytical solutions. The solutions, obtained as Green''s functions, are established by imposing temperature and heat flux continuity at the media interfaces of the various layers. The unsteady state conditions are dealt with by first computing the solution in the frequency domain and then applying (fast) inverse Fourier transforms into space-time. After validating the analytical formulation by comparing these results with those obtained experimentally, the thermal delay is computed for different multilayer systems. It is computed as the difference between the time the thermal variation is recorded in one of the system''s surfaces and the time it appears at the opposite surface. The paper calculates the computed thermal delay for construction walls made of cork, mineral wood and extruded polystyrene panels. The thermal properties of these materials have been previously defined experimentally. In the simulations, the systems are subjected to temperature changes that vary according a sine function, with the aim of defining the environmental exterior temperature variation over a period of several days. [Copyright &y& Elsevier]

Abstract: This paper presents a review of studies on natural convection heat transfer in the triangular enclosure namely, in attic-shaped space. Much research activity has been devoted to this topic over the last three decades with a view to providing thermal comfort to the occupants in attic-shaped buildings and to minimising the energy costs associated with heating and air-conditioning. Two basic thermal boundary conditions of attic are considered to represent hot and cold climates or day and night time. This paper also reports on a significant number of studies which have been performed recently on other topics related to the attic space, for example, attics subject to localized heating and attics filled with porous media. [Copyright &y& Elsevier]

The heat and moisture states of building floors without impermeable boundary construction, which affect the indoor thermal and moist environment, are determined by the heat and moisture distribution features and coupled transfer process of the under-soil and groundwater level. Previous studies based mainly on mathematical models only considered heat transfer or simplified the boundary conditions as adiabatic and impermeable, which resulted in limitations in application, specifically greater errors in shallow groundwater areas. In this paper, a scale model experiment that combined the floor, soil and groundwater was conducted to study the affected degree of the thermal and wet conditions of the floor in terms of the combined effect of soil heat and moisture transfer and indoor thermal and moist environment. The results showed that under the influence of the latent heat of vaporization, groundwater increases the floor temperature in the short term, and under the influence of water vapor pressure, groundwater decreases the relative humidity of the floor in the short term. The influence range of underground moisture source, analysis of building energy consumption effected by underground moisture source, process of ground surface hot and humid states reaching equilibrium, were discussed by numerical calculations. [ABSTRACT FROM AUTHOR]

Abstract: In order to study the influence of moisture transfer on the wall internal surface temperature, a coupled heat and moisture transfer transient model was proposed in this paper. Relative humidity and temperature were chosen as the driving potentials. The accuracy of the proposed model was verified by comparing the simulated results with the experimental data. By employing the developed model, the internal surface temperature of walls made of different materials was evaluated under the constant and variable boundary conditions. The results show that the effect of moisture transfer on the wall internal surface temperature is significant. When the moisture transfer is taken into account, the internal surface temperature has cooling effect on the indoor air and is beneficial to improve the indoor thermal environment during the working hours in summer, which lays a scientific basis for low energy building design. [Copyright &y& Elsevier]

Abstract: The reliable estimation of buildings energy needs for cooling is a crucial issue in the implementation of the EPB Directive 2010/31/EU (formerly 2002/91/EC), especially in central and southern Europe climates. On this purpose one of the main topics is to predict the behavior of the opaque envelope subjected to variable boundary conditions. The EN ISO 13786:2007 technical standard assumes sinusoidal boundary conditions and introduces dynamic thermal characteristics. The aim of this paper is to assess the deviation arising by the use of different approaches for the calculation of the dynamic thermal characteristics of an opaque envelope element under periodic non sinusoidal boundary conditions. The EN ISO 13786 procedure has been firstly applied by decomposing the external forcing temperature by means of the Fast Fourier Transform (FFT) analysis. A comparison with different approaches, such as Finite Difference Methods (FDM) and Transfer Function Methods (TFM), has been carried out. The predictions of the EN ISO 13786 with a sinusoidal forcing temperature (i.e., standard approach) have also been assessed, comparing the results to the ones obtained through the FFT analysis. Furthermore, corrections to the periodic thermal transmittance and to the time shift have been proposed, in order to improve the explicative worth of those parameters. [Copyright &y& Elsevier]