Papers by Keyword: Temperature Fluctuation

Abstract: Airflow temperature in mine changes with periodical change of surface air temperature, but its change pattern couldn’t be expressed by quantitative calculation currently. by differential equation of round roadway and zero dimension of boundary condition, wall rock thermal field is expressed by superposition of two thermal fields; the two thermal fields is respectively effected by annual average wind temperature and air temperature fluctuation. The paper mainly analyses wind temperature fluctuation differential equation and its definite condition; and deduces the expression of temperature fluctuation amplitude and phasing degree at different point of roadway, while surface air temperature periodically fluctuating; by calculating and analyzing, we have the conclusion that amplitude of temperature fluctuation presents downtrend of negative exponent curve with roadway length increasing; phasing degree linearly lag with roadway length increasing. The research result is greatly significant for controlling thermal damage and forecasting wind temperature for seasonal hot mine.

Abstract: Turbulence mixing in T-junctions filled with porous metal materials is numerical investigated using Large-eddy simulation turbulence model. Three cases of porous metal materials, made of three sintered metal spheres with different thermal conductivities (387.6 W/m۟۬•K for copper, 202.4 W/m۟۬•K for aluminum and 16.3 W/m۟۬•K for steel), are predicted. Compared the results of three cases, a higher thermal conductivity can also contribute more greatly to heat transfer enhancement. In T-junctions filled with porous metal materials, thermal conductivity is weakened considerably by the turbulence mixing of hot and cold fluid. The temperature fluctuation are no obvious different.

Abstract: In the present work the temperature fluctuations in a mixing tee were simulated on FLUENT platform using the large-eddy simulation (LES) turbulent flow model with three kinds of sub-grid scale (SGS) models such as Smagorinsky-Lilly (SL) model, Wall-adapted Local Eddy-viscosity (WALE) model, and Kinetic-energy transport (KET) model. The normalized mean and root mean square temperatures were predicted and analyzed with consideration of buoyancy. The numerical results showed that buoyancy greatly influences the mixing flow and the thermal striping phenomena were quite obvious. These three SGS models have somewhat similar accuracies for prediction of the temperature fluctuation and thermal stripping in a tee of mixing hot and cold fluids.

Abstract: Dynamic ice storage system has advantages of energy-saving by using electricity price difference of the different period. Food in display cabinet requires small temperature fluctuation to prolong preservation time. Considering the questions of energy consumption and unable to adopt the traditional method of halting and running compressor to control center temperature fluctuation in display cabinet, the paper provides dynamic ice storage system to cool display cabinet. When the wind speed keeps in suitable space, according to environment temperature, humidity and wind change, self-adaptive adjusting cooling water pump flow can maintain the center temperature within a certain range, and reduce center temperature fluctuations in display cabinet by controlling inverter frequency using PLC. Experiments prove that when environment temperature change range is 20°C to 32°C, and relative humidity is 40% to 90%, if not adopting PLC control pump flow, the temperature difference is 2.5°C, on the contrary, temperature difference is 1.3°C.

Abstract: The temperature field distribution and thermal stress distribution in concrete has been studied by finite elements method to establish the relationship between the thermal stress and the temperature in this paper. The results show that the maximum thermal gradient and the maximum thermal stress in the concrete appears on the direction of greater structural dimension, and the thermal stress value is positively correlated with thermal gradient or saying temperature difference and elastic modulus, and is negatively correlated with the water content and air content.