Coupled simulations for hygrothermal investigation of subterranean car parks and similar spaces

To investigate the hygrothermal conditions in subterranean car parks a twodimensional simulation procedure has been used, based on coupling the transient heat transfer programme HEAT with the dynamic thermal building simulation program TRNSYS. The likelihood of condensation and the rate of water deposition on surfaces were calculated with a new moisture model KOND. To estimate the consequence of moisture adsorption in materials in the hygroscopic range below saturation, the TRNSYS moisture capacitance model (buffer storage model) was used. A parametric study of the internal temperatures and the annual hours of condensation risk in underground car parks were conducted using German and UK climate data. The simulations indicate the relative risk of condensation occurring for different earth conditions, levels of insulation and air change rates, in spaces covered by earth and spaces covered by a heated building. It is shown that increased ventilation rates in summer can reduce condensation risk in underground car parks below heated buildings

Influence of transmission models for special glazing on the predicted performance of commercial buildings

A new improved model has been developed to calculate the radiation transmittance, absorptance and reflectance values for glazing with optical thin films and/or tinted glass layers. The model is based on the optical behaviour of radiation in thin films and substrates. Simulation studies examined the thermal consequences of using glazing properties calculated using the improved method rather than properties calculated by applying the conventional Fresnel-based calculations for clear glass to special glazing. Two glazings (one heat-absorbing and one coated) which had the same basic window properties (U-value and total solar energy transmittance) were studied using a commercial building, located in either a temperate, or an extreme continental, climate. The heating and cooling loads predicted by using the improved model differed from those using the conventional approximations by up to 19%. The results also demonstrated that conventional total solar energy transmittance values do not accurately reflect the thermal differences between glazing systems. Therefore, effective total solar energy transmittance values have been introduced which correctly represent the imposed heating and cooling effects of glazings. They permit more accurate predictions of heating or cooling loads from simplified (steady-state) calculation methods

Solar radiation transport through slat-type blinds: a new model and its application for thermal simulation of buildings

Although external and internal slat-type blinds (such as venetian blinds) are used frequently to reduce the solar load on windows, there are no detailed calculation models for such shading devices within detailed thermal simulation models (DSMs). A new calculation model (GLSIM-BLIND) has been written to either simulate blind systems accurately at each simulation time-step, or to simulate blinds approximately using simplified daily effective shading factors for each radiation component. In addition, the program calculates annual or monthly effective total solar transmittance values, or effective shading factors, which can be used in thermal calculations or in simple dynamic programs. The model can be used for a wide range of different blind systems and blind control strategies. It is suitable for optimising blind arrangements during the design phase of a building. This article shows the theoretical basis of the new calculation technique and demonstrates its application in thermal building simulations

The radiation transfer through coated and tinted glazing

The incidence angle dependent transmittance and absorptance of special glazing containing coated or tinted glass are conventionally modelled using a simple application of the Fresnel equations, treating the glazing as if it were clear glass. This simplified approach leads to only a rough approximation of the true transmission and can result in an inaccurate assessment of the solar energy gains in highly glazed spaces such as atria and in commercial buildings where special glazing is popular. An improved calculation technique has been developed which is based on the fundamental optical behaviour of radiation in thin films and in substrates. It considers the physical effects of coherent and incoherent layers, interference, and absorption. The main feature of the model is its applicability to any combination of coating and glass, with no limitation on the number or sequence of the layers. This paper shows the theoretical basis of the calculation technique and demonstrates its ability to produce wavelength and incidence angle dependent properties of special glazing. The validity of the predictions is illustrated by comparison with measurements