高大空间热分层实测和自然通风潜力分析

Field measurements on thermal stratification and cooling potential of natural ventilation for high and large spaces

在自然通风建筑中,垂直方向上温度分布影响着热压通风。现对南京某单体大空间自然通风建筑垂直方向上温度进行实测,得出在九月份垂直温度呈线性变化,梯度在0.1~0.24℃/m范围内。将温度分层结合已有的热压模型,通过CFD模拟验证模型准确性,用Matlab计算分析建筑上下开口比Rab、室内热源q和垂直温度系数α对室内温度和自然通风量的影响,发现室内温度随着建筑上下开口比Rab和室内热源q的增大而增大,随着垂直温度系数α的增大而减小;建筑的自然通风量受室外温度影响较小,随着上下开口比Rab、室内热源q和垂直温度系数α的减小而减小。计算某高大空间在南京、重庆和广州各月的热压通风量和室内温度,结合热舒适模型确定满足基准通风量和热舒适要求的可利用上下开口比Rab范围和各月热舒适时数。结果表明:广州利用自然通风达到热舒适的时数最多,可利用的上下开口比Rab为1~9,室内热舒适时数占各月总时数的比例为35%~70%。

In naturally ventilated buildings,temperature distributions in vertical directions have much influence on the thermal pressure ventilation. Field tests were done on a single naturally ventilated large space during September at Nanjing in China.Results indicated that temperatures increased linearly towards the ceiling with its gradient being in range of 0. 1-0. 24 ℃/m. The stack effect model was modified by introducing the thermal stratification and validated by CFD simulation.Matlab codes were used to solve the model and to investigate different lower-upper opening area ratios Rab,heat sources q and temperature gradients α,finding out its influences on the thermal pressure ventilation.Results showed that occupied air temperatures increased with the increasing of lower-upper opening area ratio Rabor heat source q but with the decreasing of temperature gradient coefficient α,the outdoor climate did little influence on the ventilation flow rate,the ventilation flow rates declined with the decreasing of α or q. Occupied air temperatures and the ventilation flow rates were obtained for three cities in China to get the available Rab under thermal stratification model and benchmark ventilation rate.Guangzhou was of the highest occupied temperatures under the same Rab,q and α.The available Rabcombined the thermal comfort and benchmarkventilation rateissues which averaged from 1 to 9. Also,the satisfied hourly number frequencies averaged from 35% to 70%.