提高温室地热利用率的关键技术

本文分析了地热温室的温室特性和地热特性,研究了提高温室地热利用率的关键技术,构建了地热温室复合供热系统模型。

Alternate operation characteristics of a solar-ground source heat pump system

In order to investigate the alternate operation characteristics of a solar-ground source heat pump system（SGSHPS）,various alternate operation modes are put forward and defined.A two-dimensional mathematical model with freezing/melting phase changes is developed for the heat transfer analysis of the soil.Based on the numerical solution of the model,the variation trends of underground soil temperature of the SGSHPS operated in various alternate operation modes are discussed.The results indicate that,for the day-night and short-time interval alternate operation modes without solar energy,the operation time fraction of a solar heat source should be confined to from 50% to 58% when operated in an alternate period of 24 h.Meanwhile,the disadvantages of a natural resumption of soil temperature can be overcome effectively by solar energy filling,and an optimal operation effect can be achieved by integrating the mode of solar energy filling with other alternate modes.In addition,the accuracy of the presented model is verified by the experimental data of borehole wall temperatures.The conclusions can provide a reference for the optimization operation of the SGSHPS.

Experimental investigation on heat transfer characteristics of a new radiant floor system with phase change material

In order to improve the heat transfer characteristics of the traditional phase change material（PCM） floor, a new double-layer radiant floor system with PCM is proposed, which can store thermal or cold energy in the off-peak period and use them in the peak period. An experimental setup was developed to study the heat transfer characteristics of the new system under both cooling and heating modes. The experimental results show that the double-layer radiant floor system with PCM can meet both the cold and thermal requirements of users. Moreover, with the same duration of the thermal energy storage process, the increase of water temperature supplied to the system can improve the heat transfer characteristics of the system but lead to the discomfort of users. On the other hand, if the air temperature at the end of the thermal energy storage process is the same under different conditions, the increase of supplied water temperature will decrease the thermal energy storage time and ensure the comfort of users.

Relationship between Physical and Chemical Soil Attributes and Plant Species Diversity in Tropical Mountain Ecosystems from Brazil

Although the high diversity of plant species in the rupestrian fields has been primarily attributed to the existence of a set of distinct habitats, few studies support this assertion. The present study aimed to further investigate the relationship between physical and chemical attributes of soils with the diversity of plant species in this unique ecosystem. The rupestrian field is a unique vegetation formation that covers some of the southeastern Brazilian mountains in the transition of the Atlantic rain forest and the Cerrado(savanna). Different habitats occur according to soil characteristics(e.g., presence of rocks, sand, fertility, hydrology, etc.). These attributes ultimately influence the vegetation that is highly adapted to the harsh edaphic and climatic mountain conditions. Five distinct habitats were studied by us: rocky outcrops, peat bogs, sandy bogs, quartz gravel fields, and "cerrado"(savanna). A floristic survey indicated that four families are found at greater frequency: Poaceae, Asteraceae, Cyperaceae, and Leguminosae. The greatest diversity of plant species was found in the rocky outcrops habitat, followed by cerrado, peat bog, quartz gravel grassland, and sandy bogs, respectively. The main difference in the floristic composition among these habitats was related to the dominant species. Trachypogon spicatus(Poaceae) was the most dominant species in the rocky outcrops, Axonopus siccus(Poaceae) in the peat bogs, Lagenocarpus rigidus(Cyperaceae) in the sandy bogs, Schizachyrium tenerum(Poaceae) in the cerrado, while Vellozia sp. 8(Velloziaceae) dominated the vegetation in the quartz gravel grassland. This study demonstrated that physical and chemical soil properties strongly related the diversity of plant species occurring in the different habitats of rupestrian fields.

Characteristic analysis of bleeding effect on standing column well (SCW) type geothermal heat exchanger

Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy.The thermal performance is affected by many different design parameters and different operating conditions such as bleeding.This eventually determines the operation and cost efficiency of the borehole heat exchanger system.The thermal performance of an open standing column well (SCW) type geothermal heat exchanger was assessed under the influence of bleeding.For this,a thermal response test rig was established with line-source theory.The test rig also had a bleeding function by releasing fluid while taking additional underground water through the heat exchanger.The thermal response test was performed with an additional constant input heat source.Effective thermal conductivity and thermal resistance were obtained from the measured data.From the measurement,the effective thermal conductivity is found to have 1.47 times higher value when bleeding is applied.The thermal resistance also increases by 1.58 times compared to a non-bleeding case.This trend indicates enhanced heat transfer in the SCW type heat exchanger with a bleeding function.Bleeding,therefore,could be an effective method of achieving a high heat transfer rate in the SCW type heat exchanger with sufficient underground water supply.

NUMERICAL EXPERIMENT ON THE EFFECT OF URBANIZATION UPON SUMMER LAND-SEA BREEZES IN THE COASTLAND OF GUANGXI

The 2003-006 observations were utilized to analyze the surface characteristics of summer land-sea breezes along the coastland of Guangxi and the Weather Research and Forecast model was applied to simulate the breeze structure on August 1-2, 2006. Results show that 1） the intensity and distributions of the breezes reproduced from improved urban underlying surface were close to observations. In the daytime the coastwise urban band was a convergent belt of sea breeze, corresponding to the centers of torrential rains; in the nighttime hours the surface of the Gulf of Tonkin （the Vietnamese name） or the Northern Bay （the Chinese name） acted as a convergent zone of land breezes, likely to produce convective cloud cluster; 2） the experiment on urbanization showed the heat island effect enhancing （weakening） the sea （land） breeze development. Furthermore, the heat island effect mitigated the atmospheric cooling via radiation over the cities in the night, weakening sinking motion correspondingly, thereby suppressing the dominant factor responsible for the steady development of temperature inversion. As a result, the inversion vigor was reduced greatly, but nevertheless no strong effect of the decreased subsidence was found upon the inversion height.

穿越阿尔卑斯山异常地热带的深埋辛普隆铁路工程可行性研究

在辛普隆地区，深部开挖隧道通过阿尔卑斯山脉，遇到了岩体内的地热高温问题。有关沿规划铁路线各个特定地地点的地热特征，由于所获得的有用资料甚少，预计将会极其复杂。由于上述不确定因素，并考虑到隧道工程必须在深部岩体内进行施工的特殊性情况。为了解辛普隆地区的实际情况，作为基本解决办法而制定了多学科的勘探计划，其中 表地质测绘，偶极地电测绘，深层大地电磁法，以及对地下水采用物理、化学同位素分析法。

Relationship of atmospheric boundary layer depth with thermodynamic processes at the land surface in arid regions of China

The atmospheric boundary layer （ABL） is an important physical characteristic of the Earth＇s atmosphere. Compared with the typical ABL, the ABL in arid regions has distinct features and is formed by particular mechanisms. In this paper, the depth of the diurnal and nocturnal ABLs and their related thermodynamic features of land surface processes, including net radiation, the ground-air temperature difference and sensible heat flux, under typical summer and winter conditions are discussed on the basis of comprehensive observations of the ABL and thermodynamic processes at the land surface carried out in the extreme arid zone of Dunhuang. The relationships of the ABL depth in the development and maintenance stages with these thermodynamic features are also investigated. The results show that the depth of the ABL is closely correlated with the thermodynamic features in both development and maintenance stages and more energy is consumed in the development stage. Further analysis indicates that wind velocity also affects ABL development, especially the development of a stable boundary layer in winter. Taken together, the analysis results indicate that extremely strong thermodynamic processes at the land surface are the main driving factor for the formation of a deep ABL in an arid region.