Search

Tubular light guides are applicable for daylighting of windowless areas in buildings. Despite their many positive indoor climate aspects they can also present some problems with heat losses and condensation. A computer CFD model focused on the evaluation of temperature distribution and air flow inside tubular light guides of different dimensions was studied. The physical model of the tested light guides of lengths more than 0.60 m proves shows that Rayleigh numbers are adequate for a turbulent air flow. The turbulent model was applied despite the small heat flux differences between the turbulent and laminar model. The CFD simulations resulted into conclusions that the growing ratio of length/diameter increases the heat transmission loss/linear transmittance as much as by 50 percent. Tubular light guides of smaller diameters have lower heat transmission losses compared to the wider ones of the same lengths with the same outdoor temperature being taken into account. The simulation results confirmed the thermal bridge effect of the tubular light guide tube inside the insulated flat roof details. The thermal transmittance of the studied light guides in the whole roof area was substituted with the point thermal bridges. This substitution gives possibility for simple thermal evaluation of the tubular light pipes in roof constructions. [ABSTRACT FROM AUTHOR]

Deep mining results in an increasingly serious hazard. Based on the principle of heat transfer and radiant cooling, a three-dimensional heat transfer model of the working face was established. The influence of the inlet airflow parameter, the surrounding wall temperature and other parameters on the temperature distribution of airflow along the working face were analyzed under the radiation cooling mode. The results show that the increment of airflow temperature in several sections along the working face decreases by 0.67 °C, 0.48 °C, 0.40 °C, 0.36 °C, 0.33 °C, 0.29 °C respectively. The farther away from the airflow inlet, the more obvious the cooling effect was. The airflow temperature of the working face is positively correlated with the airflow inlet temperature and the surrounding wall temperature, and is negatively correlated with the airflow velocity. The research provides a good solution for the working face cooling of deep mines, and also provides a theoretical reference for the research on the radiation cooling technology of the working face. [ABSTRACT FROM AUTHOR]