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A conversion of shortwave to longwave radiation heat transfer in building envelope system represents an substantial part in low-energy design campaing. For that reason, an experimental test sample of a novel solar façade element based on a Transparent Insulation Material (TIM) with a selective and a nonselective absorber was developed. The investigated element is a part of an opaque lightweight structure of a building envelope. The capability of one widely used Building Energy Simulation (BES) tool is analyzed in terms of its ability to model the performance of the TIM façade element. The good consistency between the simulation results and the experimental data obtained specifically via cooling period indicates that the reference simulation model based on high emisivity of solar absorber was reliable when predicting the energy performance of TIM based façade models. However, the low emissivity of solar absorbers in the façade cavity gives rise significant limitations. They were identified concerning the BES calculation methods and modeling principles. The computational results are significantly underestimated in case of low emissivity internal surface. The methodology developed in this study is expected to provide a reference for simulating the thermal and energy performance of TIM-based building elements with different solar absorbers. [ABSTRACT FROM AUTHOR]

This paper is divided into two parts; the first describes a CFD analysis of a gland packing labyrinth seals in 20 MW steam turbine in LNG plant using ANSYS CFX code as an isothermal simulation in fluid domain. The results of two turbulence models k-ε and k-ω SST are compared and validated against experimental data. It is shown that the labyrinth seal leakage is proportional to the clearance cube so any variation in clearance can have a significant impact on the steam leakage. This clearance between the shaft and the labyrinth seal vary as a function of operating temperature due to the different rates of thermal expansion of the materials for these two components. Likewise the fluid temperature has a direct effect on fluid dynamic behavior. For that; the second part of the paper investigates the effect of fluid thermal conditions of the labyrinth seal via the heat transfer and Nusselt number variation in the stator and the rotor, for different cases of inlet temperature (400 °C, 200 °C, 100 °C, 50 °C) and pressure ratio (2.5, 4.5, 6.5) for an ideal gas. Also it is important to know the temperature distribution across tooth and cavities of the labyrinth seal, and finally the Influence of Inlet total temperature on fluid pressure drop in the labyrinth seal will be treated for improving and readjusting the steam turbine sealing system. [ABSTRACT FROM AUTHOR]

Light pipes transmit daylight into building interiors. Their installation into thermally insulated roofs of low energy buildings can be a problem because of thermal bridges and condensation problems. This article is focused on a CFD simulation thermal analysis that includes four variations of light pipes with a segment of a flat roof. Common light pipes with a hollow light guiding tube were compared to special light pipes containing an additional glass unit located inside the tube. The additional glass units increase thermal resistance and reduce condensation risks of the light guiding systems. The light pipes were compared in two different simulation models run in ANSYS Fluent software and the CalA program. Temperature profiles and air flow patterns of the cross sectional profiles of the light pipes served to determine the total heat transmittance and heat losses of the studied light pipes installed in a segment of a thermally insulated flat roof. The paper compares simplified 2D rotational–symmetrical numerical model based on the thermal diffusion equation with the complex 3D CFD numerical simulation. The results confirm that the simplified 2D numerical model is suitable for the thermal evaluation of the light pipes containing an additional glass unit, too. The additional glass unit with the triple glass improves thermal resistance up to 88% in case of light pipe with diameter 600 mm and reduces optical transmittance to 28%. [ABSTRACT FROM AUTHOR]

Numerical simulations and experiments were performed for a thermally active wall with pipes arranged in milled channels in the thermal insulation. The advantage of this system is its suitability for installation in both new and existing buildings in the form of precast heat insulation panels attached to their facades. The study shows that by active control of the supply water temperature, it is possible to alternate the walĺs function between space heating and a thermal barrier. The wall system has the potential to significantly reduce heat loss when used as a thermal barrier. When operated as space heating, embedding the pipes in thermal insulation reduced the heating capacity by 50% as compared to systems with pipes arranged in a concrete core and by 63% for pipes arranged in a layer underneath the surface. It is crucial that pipes arranged in channels are embedded in a thermally conductive material. Failing to do so can substantially diminish the heating capacity due to the imperfect contact between the pipes and radiant surface and also due to the air gap that may form around the pipes. The thickness of the thermal insulation, spacing of the pipes, and supply water temperature also have a substantial effect on the heating capacity, whereas the thickness of the concrete core does not. [ABSTRACT FROM AUTHOR]

[Display omitted] • Analyses are conducted focused on climate adaptive reactions of BiPV facade system. • System's performance prediction is relevant for energy-efficient buildings. • Optimisation techniques yielded an increase in total thermal and energy performance. Ventilated building-integrated photovoltaic (BiPV)/phase-change material (PCM) façades have been applied and validated in building energy simulations; however, the dynamic thermal response of these façades has not been investigated. Notably, performance predictions and simulations for systems featuring natural airflows in the façade cavity are important for guiding the decision-making for energy-efficient buildings. To address this challenge in literature, in this work, numerical analyses were conducted, focusing on the climate adaptive reactions of a BiPV façade system coupled with a latent thermal energy storage system, based on a PCM. Numerical methods for determining the PCM heat transfer were evaluated, including their limitations. The thermodynamic reactions of two BiPV façade concepts were comparatively studied using two simulation domains: building energy simulations and computational fluid dynamics. The reliability of the theoretical methods was also evaluated. Good agreement between the simulation results and experimental data was noted through dynamic outdoor tests, empirically validating the study; standard statistical indicators were calculated and employed to assess the consistency between the experimental and simulation results. The used numerical approach can reliably predict the thermo-responsive capabilities of PCM-based BiPV façades with respect to the overall tendencies. The parameter variation techniques revealed modifications in the overall thermal and energy performance of the façade system. The most undesirable instance of overheating was predicted when using RT27; therefore, the PCM is considered inappropriate in this case. [ABSTRACT FROM AUTHOR]