The thermal buoyancy generated by the difference in air density in a building can drive hot-pressed natural ventilation,which is an energy-efficient means of ventilation used to obtain higher air quality.Therefore,the...The thermal buoyancy generated by the difference in air density in a building can drive hot-pressed natural ventilation,which is an energy-efficient means of ventilation used to obtain higher air quality.Therefore,the effect of a single-point heat source with limited sides at different heights on stratified flow was studied in a naturally ventilated room in this paper.Based on the classical plume diffusion law of an independent point heat source and the mirroring principle,a calculation model of the thermal stratification height with a restricted source elevated to different levels was derived and validated.The quantitative effects of the heat source height from the floor,the effective opening area and other factors on the natural ventilation of hot pressure were analyzed.A threshold X_(T)for the separation between a point source and a sidewall was defined to estimate whether the thermal plume was independent or restricted by a sidewall.And a method for calculating the threshold xt was obtained.This research can provide a reference basis for designing natural ventilation for buildings with a restricted heat source at different levels to achieve a desired indoor environment.展开更多
Understanding the relationship between tree height （H） and diameter at breast height （D） is vital to forest design, monitoring and biomass estimation. We developed an allometric equation model and tested its appli...Understanding the relationship between tree height （H） and diameter at breast height （D） is vital to forest design, monitoring and biomass estimation. We developed an allometric equation model and tested its applicability for unevenly aged stands of moso bamboo forest at a regional scale. Field data were collected for 21 plots. Based on these data, we identified two strong power relationships： a corre- lation between the mean bamboo height （Hm） and the upper mean H （Hu）, and a correlation between the mean D （Din） and the upper mean D （Du）. Simulation results derived from the aUometric equation model were in good agreement with observed culms derived from the field data for the 21 stands, with a root-mean-square error and relative root-mean-square error of 1.40 m and 13.41%, respectively. These results demonstrate that the allometric equation model had a strong predictive power in the unevenly aged stands at a regional scale. In addition, the estimated average height-diameter （H-D） model for South Anhui Province was used to predict H for the same type of bamboo in Hunan Province based on the measured D, and the results were highly similar. The allometric equation model has multiple uses at the regional scale, including the evaluation of the variation in the H- D relationship among regions. The model describes the average H-D relationship without considering the effects caused by variation in site conditions, tree density and other factors.展开更多
基金supported by the Natural Science Foundation of Shaanxi Province(No.2020JQ-670)China Postdoctoral Science Foundation(No.2020M673353).
文摘The thermal buoyancy generated by the difference in air density in a building can drive hot-pressed natural ventilation,which is an energy-efficient means of ventilation used to obtain higher air quality.Therefore,the effect of a single-point heat source with limited sides at different heights on stratified flow was studied in a naturally ventilated room in this paper.Based on the classical plume diffusion law of an independent point heat source and the mirroring principle,a calculation model of the thermal stratification height with a restricted source elevated to different levels was derived and validated.The quantitative effects of the heat source height from the floor,the effective opening area and other factors on the natural ventilation of hot pressure were analyzed.A threshold X_(T)for the separation between a point source and a sidewall was defined to estimate whether the thermal plume was independent or restricted by a sidewall.And a method for calculating the threshold xt was obtained.This research can provide a reference basis for designing natural ventilation for buildings with a restricted heat source at different levels to achieve a desired indoor environment.
基金financially supported by the Special Fund for Basic Scientific Research of International Centre for Bamboo and Rattan(1632014003)National Natural Science Foundation of China(31101148 and 31300177)
文摘Understanding the relationship between tree height （H） and diameter at breast height （D） is vital to forest design, monitoring and biomass estimation. We developed an allometric equation model and tested its applicability for unevenly aged stands of moso bamboo forest at a regional scale. Field data were collected for 21 plots. Based on these data, we identified two strong power relationships： a corre- lation between the mean bamboo height （Hm） and the upper mean H （Hu）, and a correlation between the mean D （Din） and the upper mean D （Du）. Simulation results derived from the aUometric equation model were in good agreement with observed culms derived from the field data for the 21 stands, with a root-mean-square error and relative root-mean-square error of 1.40 m and 13.41%, respectively. These results demonstrate that the allometric equation model had a strong predictive power in the unevenly aged stands at a regional scale. In addition, the estimated average height-diameter （H-D） model for South Anhui Province was used to predict H for the same type of bamboo in Hunan Province based on the measured D, and the results were highly similar. The allometric equation model has multiple uses at the regional scale, including the evaluation of the variation in the H- D relationship among regions. The model describes the average H-D relationship without considering the effects caused by variation in site conditions, tree density and other factors.
