An experimental study was performed to measure the cooling of a smoke layer by water sprays. This was followed by the development of a mathematical model based on the theory of Chow and Tang. The predictions of the model agree well with the experimental measurements. Water sprays investigated in the present work provided significant cooling of the smoke layer. We observed little effect of increasing the water pressure from 50 to 100 kPa on the cooling of the smoke layer. KEYWORDS:

A mathematical model for predicting sprinkler cooling effect on smoke layer was developed. Results of calculation showed that the temperature difference between droplets and smoke layer and the thickness of smoke layer are major factors of the cooling effect. The cooling effect might lose its efficiency when the sprinkler pressure became relatively high. Experiments were carried out to validate the model and compared with Morgan model. The experimental results show that temperatures predicted by the current model agree well with the experimental results when temperature difference is high. However Morgan model is more suitable for low temperature difference.

As sprinklers systems are widely adopted as fire fighting devices in buildings, it is necessary to develop quantitative models for investigation of the influence of sprinklers on fire development. A fire zone model which includes the cooling effect of sprinklers is developed. Heat transfer from the smoke layer to sprinkler water spray was considered as an additional heat loss term in energy balance equation. In the absence of a sprinkler, the predicted temperature of this model matched that of CFAST6.0, while when sprinkler effects were included, the model predicted the temperature profile of the smoke layer with good agreement with published experiments. This model was applied to a hypothetical compartment fire. Results showed that a higher heat release rate of fire led to a significant decrease in smoke temperature following sprinkler activation, while only a small decrease in smoke layer temperature is predicted when increasing sprinkler pressure from 0.05MPa to 0.1MPa.

In this paper, we shall discuss the calculate method of heat loss of central heating pipes.the calculation formulas available are too complicated and inconvenienced to analysis the dynamic thermal conditions of heating pipeline. Therefore, this paper presents one order polynomial with least-squares solution, and then establishes linear equations of heating pipeline heat loss that the hot water temperature as a variable alone. It is based on the comparision and analysis of buried hot water heating pipeline heat loss formula. This method will simplify not only the calculation, but also the model of calculation analysis for different diameter, different insulation materials. The result is that the deviation of the formula is caused mainly by the thermal resistance. The relative errors of simplified formula and the selection formulas are less than 3%, which can meet the requirements for engineering applications.