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Impact of Non-Uniform Distribution of Temperature on the State of Stress of Masonry
Beran, Pavel
Deterioration of masonry is caused by inordinate loading and by climatic actions. Climatic cyclic thermal stress in a structure is incurred by unequal temperature gradient across the thickness of homogenous or heterogeneous masonry. Thermal gradient also causes significant stress close to the interface between stone and mortar in masonry made of components with different thermal expansion properties. The values of thermal stress increase with higher thermal gradient. Impact of insolation, absorption of solar radiation, air temperature around the structure, heat transfer coefficient, coefficient of heat conduction, and heat capacity to the temperature gradient in the wall exposed to the exterior weather conditions were investigated with a numerical model. All of these effects or material properties affect the maximal surface temperatures in masonry during summer.
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Prospects of digital holographic interferometry in heat transfer measurement
Doleček, R. ; Lédl, Vít ; Kopecký, V. ; Psota, P. ; Václavík, Jan ; Vít, Tomáš
In the measurement of heat transfer problem, a holographic interferometry (HI) is often used mainly because of its unique properties and very high adaptability to different sort of problems under investigation. Although in the area of vibration or deformation measurement of solid body the standard HI is replaced massively by digital holography in the case of refractive index distribution the situation is quite opposite. In this paper we present two different types of digital holographic interferometers. The interferometers with different sensitivities have been build and successfully tested.
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Numerická simulace separovaného dvoufázového proudění vařící se vody v kanálu o tvaru cívky
Novák, Aleš ; Hrubý, Jan
This work deals with a quasi-1D mathematical model of flow of a boiling liquid-vapor mixture in a coil-shaped duct heated from the outer side of the coil. The liquid and gas phases are allowed to flow at different velocities (stratified flow regime). The model simulates a modification of the laboratory steam generator built in Institute of Thermomechanics AS CR. The liquid is centrifuged to the heated wall thus enhancing the heat transfer. The model also includes heat conduction in the metal body of the steam generator.
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Přenos tepla napříč superizolacemi z pokojových do nízkých teplot
Hirschl, Ch. ; Králík, Tomáš ; Laa, Ch. ; Musilová, Věra ; Schmid, T. ; Stipsitz, J.
For more than 30 years thermal measurement results and analytical formulas are available to calculate the heat transfer through Super Insulation (SI). According to the temperature dependence of the emissivity for aluminium, the most commonly used material for the reflecting surfaces, derivations based on the Stefan-Boltzmann-Law for radiative heat transfer have been established. Together with conductive terms this leads to formulas for the calculation of heat transfer through SI. Using new measurement results of temperature-dependent emissivity and conductivity we have performed heat flux calculations applying common software tools. The heat transfer through the SI and the temperature distribution inside the SI calculated with this new approach has been compared with the established formulas and measurement results.
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