多井同期抽灌储能模式咸水层热运移特性研究

基于含水层储能水、热运移的基本理论与控制方程,针对地下咸水层储能过程中渗流溶液密度及粘滞性系数变化显著的特点,对现有的地下含水层储能数学模型进行修正、完善,建立地下咸水层耦合储能模型,探索不同储能模式下含水层温度场变化规律及阶段性热量运移特征。研究结果得到,采用地下原水与去离子水回灌时,在储热运行期与间歇停运期粗粉砂层中热作用半径变化率分别为0.272m/d、0.008m/d,0.348 m/d、-0.04 m/d。在储能阶段,伴随回灌溶液温度上升、盐度降低,地下水渗流速度上升,导致对流换热与热弥散效应增强；间歇阶段,则由于地下咸水与回灌溶液间盐度梯度增大,在分子扩散作用下回灌溶液温度场影响范围减弱。     

非完整河与潜水含水层相互作用的非稳定流数值模拟

针对以往河流对含水层补给方式考虑的不足,基于含水层水位与河水位及河床底板高程的关系,考虑了非饱和带的影响,借助非饱和带的相关理论获得了河流对含水层的补给量的表达式,采用数值模拟方法计算了非完整河对潜水含水层的补给量,并探讨了补给量与抽水井中水位变幅和非饱和带内最大基质吸力的关系。结果表明,非饱和带内的补给量不可忽略,且井中水位变幅越小、最大基质吸力越大,则补给量越大。     

中深层地热单井循环系统传热强化方法研究

针对中深层地热单井循环系统井内热贯通导致的换热功率低的问题,提出一种内管末端变径的井下传热强化方法,并建立数值模型,利用FLUENT进行为期30 d的模拟计算。结果表明,采用内管末端变径的方式能有效增强地下水“互动”,充分利用含水层的高温来提高单井换热功率。将井下换热分为导热区和采灌区两部分,随着封堵比例的增加,抽水中的含水层补给占比增加,且采灌区换热功率在系统换热功率中的占比逐渐增加。当封堵比例增大到100%时,采灌区换热功率达到导热区的1.76倍,井口出水温度可基本稳定在58℃,系统换热功率稳定在约995.46 kW,相较于内管等径系统,换热功率可提高84.71%。同时,单井循环系统仅导热区的延米换热量就可达到154.23～216.89 W/m,超过了闭式同轴套管换热系统稳定运行的最高延米换热功率,而系统换热功率可达到闭式系统的3.57～6.60倍,在单井换热系统中具有显著优势。     

Geophysical exploration of the Boku geothermal area, Central Ethiopian Rift

The Boku central volcano is located within the axial zone of the Central Ethiopian Rift near the town of Nazareth, Ethiopia. An integrated geophysical survey involving thermal, magnetic, electrical and gravimetric methods has been carried out over the Boku geothermal area in order to understand the circulation of fluids in the subsurface, and to localize the “hot spot” providing heat to the downward migrating groundwaters before they return to the surface. The aim of the investigations was to reconstruct the geometry of the aquifers and the fluid flow paths in the Boku geothermal system, the country's least studied. Geological studies show that it taps heat from the shallow acidic Quaternary volcanic rocks of the Rift floor. The aquifer system is hosted in Quaternary Rift floor ignimbrites that are intensively fractured and receive regional meteoric water recharge from the adjacent escarpment and locally from precipitation and the Awash River. Geophysical surveys have mapped Quaternary faults that are the major geologic structures that allow the ascent of the hotter fluids towards the surface, as well as the cold-water recharge of the geothermal system. The shallow aquifers are mapped, preferred borehole sites for the extraction of thermal fluids are delineated and the depths to deeper thermal aquifers are estimated.     

Influence of natural convection on forced horizontal flow in saturated porous media for aquifer thermal energy storage

Estimation of the heat recovery rate in high-temperature underground storage (>50 °C) is required before such a system can be built. However, if high-temperature water is injected into and stored in the aquifer, large-scale natural convection could occur that might reduce the heat recovery rate. This study aims to clarify the universal quantitative condition under which natural convection appears and exerts an observable influence for a system with forced horizontal flow in the saturated porous medium. The authors investigated this using both experiments and computer simulations.A test section simulating an aquifer was made. Warm water was injected into the test section, which was filled with glass beads. The temperature distribution and the flow rate profile at the outlet were measured. The authors found that the limit condition at which natural convection influences the forced horizontal flow can be determined from the velocity profile and modified Rayleigh number Ra^*. In addition, the heat transfer coefficients of the upper and the lower side of walls were estimated. A computer simulation was made for calculation of the temperature field and the velocity vector in the porous medium under natural convection and under forced convection. As calculated temperature fields and flow rate distributions at the outlet were similar to the experimental results, it is thought that this program can be applied to evaluation of the temperature and the velocity of aquifer thermal energy storage. In addition, an index expressing the degree of influence of natural convection on forced convection was proposed.     

常温注水井对含水层热贯通的影响机理分析

为探究常温注水井对水源热泵热贯通现象的影响,利用FlowHeat1.0软件模拟了3组情景下含水层渗流场、温度场时空分布特征,并分析了常温注水井对含水层热贯通的影响机理和抽水井水温变化规律。结果表明,常温注水井通过减小回灌井、常温注水井之间的水力坡度和延长地下水渗透途径的方式达到缓解热贯通的效果;回灌井、常温注水井流量比相同时,常温注水井在抽灌井连线的位置对含水层热贯通的影响小;抽灌量不变时,常温注水井与回灌井的流量比越大,常温注水井缓解热贯通的效果越明显;在有利地下水回灌的水源热泵系统中,布设常温注水井能有效地降低含水层热贯通程度。     

Surface heat flow and deep temperatures in the Bradano Trough (Southern Italy). Possible effects of groundwater circulation

The surface heat flow distribution in the Bradano Trough (southern Italy) is examined in the light of temperature distribution at depth, reconstructed on the basis of data from deep oil wells. The effects of groundwater circulation and the related problem of inferring deep thermal conditions from surface heat flow have been studied by mathematical models. Groundwater effects are certainly important in the zones close to the recharge areas, whereas far from these areas we cannot even establish whether water circulation has a significant effect on surface heat flow.     

Thermal analysis of constant flow partitioned solar pond

This paper presents the thermal analysis of the process of heat extraction by circulating water layer through the convective zone of a partitioned solar pond. The observed variation of atmospheric air temperature and solar intensity is assumed periodic. Explicit expressions for the transient rate and temperature at which heat can be extracted by circulation of water at constant flow rate, are derived. Numerical computations corresponding to solar heat flux and atmospheric air temperature measurement at New Delhi during the year 1974 have been made, and the optimization of the flow rate as well as the depth of the convective-non-convective zones in the pond have been investigated. The optimum heat retrieval efficiency of 27.5%, 34% and 40% corresponding to heat retrieval temperatures of 97°C, 60.5°C and 45.5°C, respectively, are predicted for water flow rates of 2 × 10^?4, 5 × 10^?4 and 10^?3 kg/s.m², respectively. The load levelling in retrieved heat flux improves as flow rates are lowered, and the non-convective zone is oversized. With the non-convective zone depth near optimum, an increase in the depth of the heat extraction zone considerably influences the retrieved heat flux; it shifts its maximum to winter months and deteriorates the load levelling. The variability in flow rate required for the maintenance of constant temperature of the heat extraction zone is also investigated. It is found that the required variability is less for higher temperatures of the extraction zone and larger depths of non-convective zone.     

供热系统散热器的热特性敏感性分析

本文对供热系统中四种重要型式散热器的热特性进行了理论分析。考虑流量和供水温度的关键影响,根据传热学原理和工程实践,定量地并形象地给出了敏感性分析结果。研究表明,和流量的影响相比,供水温度对四种散热器的散热量具有近线性的更显著的敏感影响,而流量增加到一定数值后,敏感性影响明显减弱。比较发现,钢制柱式散热器由于相对不敏感的热特性使之调节性能差,但稳定性能好;M-132型散热器的可调节性最好。本文的研究为供热系统的节能提供了参考。     

Geothermal assessment of the deep aquifers of the northwestern part of the Bohemian Cretaceous basin, Czech Republic

Groundwater in the Benešov-Ústí aquifer system in the northwestern Bohemian Cretaceous basin has been intensely exploited since the twentieth century. Apart from providing drinking water, it contains the most extensive accumulation of thermal water in the country. However, excessive exploitation can result in temperature declines and changes in the quality of the groundwater in the future. More than a hundred in situ temperature measurements were used to assess the geothermal gradient and heat flux. However, intense groundwater vertical flow across the well significantly controls the heat flux distribution, resulting in a huge range of values—from less than 50 mW/m² within infiltration areas to more than 125 mW/m² in drainage areas. Certain simplifications and corrections considering the vertical flow between different permeable zones were developed, and the correction for topography as well as lithological variability have been applied to improve accuracy of the geothermal gradient assessment. Despite the fact that the Bohemian Cretaceous basin is tectonically very complex, it is concluded that tectonics [with the exception of the Eger (Oh?e) rift] has only a secondary effect on the thermal field. Two longitudinal W-E areas in the Benešov-Ústí aquifer system have elevated heat flux values. The calculated heat flux values are useful for heat transfer modelling and the assessment of the sustainable limits of thermal water exploitation.     

Mixed convection heat transfer in a passive solar building

Convective heat transfer through apertures such as doorways can be an important process by which thermal energy is transferred from one zone to another zone of a building. In this article, interzonal natural and forced convection in a two- and a three-zone, full-scale building are examined. Aperture velocity and temperature distributions are measured and the experimental interzonal mass flow rate and heat transfer are determined. A model based on zone temperature distributions is derived to predict the interzonal mass flow rate and heat transfer. The measured and predicted interzonal flow rate and heat transfer are compared and found to be in good agreement.     

岩溶含水层地下水源热泵运行对地下水温度场的影响

为探究岩溶含水层水源热泵运行期间地下水温度场变化规律,以武汉市某场地地下水源热泵系统为例,基于有限元数值模拟软件FEFLOW,分别模拟了水源热泵空调制冷和制热期间抽水-回灌目的含水层中的渗流场和温度场,并对表征岩溶发育的重要参数储水系数和孔隙度进行敏感性分析。模拟结果表明,地下水源热泵运行仅影响回灌井附近地下水温度,不会对区域含水层温度产生影响;而表征岩溶发育的典型参数储水率和孔隙度,对模拟结果的影响不大。     

Mathematical model for coal conversion in supercritical water: reacting multiphase flow with conjugate heat transfer

Providing heat for supercritical water gasification (SCWG) of coal by coupling subsequent products oxidation in integrated supercritical water reactor (ISWR) provides an effective method for directional control of temperature field and avoids excessive hot spots caused by uniform heating. An exploratory numerical model incorporating particle-fluid flow dynamics, multispecies transport and thermal coupling between endothermic coal gasification and exothermic product oxidation was established to simulate the reacting multiphase flow process of coal conversion in a novel lab-scale ISWR. An eleven-lump kinetic model was proposed for the prediction of chemical reactions. And the thermal coupling relationship was described by conjugate heat transfer boundary conditions (BC). Detailed physical and chemical field distribution in ISWR were analyzed and influence factors were discussed. The results showed that oxidation of gas products as inner heat source could promote the gasification reaction with only slight or even little maximum temperature increase of the pressure-bearing wall. Coal feeding rate and oxygen supply method significantly affected the field distribution. The multi-injection compressed-air supply method provided a more uniform temperature field but would reduce heat transfer temperature difference. The carbon gasification efficiency (CGE) in the gasification zone could easily reach up to 97% under mild conditions (less than 650 °C).     

渗滤池砂样对回灌水中污染物去除的研究

采用室内砂柱实验研究了渗滤池回灌过程中的渗滤层堵塞特征和水质变化规律,通过测定渗透系数定量分析了砂柱的堵塞程度并在回灌过程中测定砂柱不同位置水样的悬浮物浓度、TOC、高锰酸盐指数、总氮、无机阴离子等的变化.结果表明,回灌水中的悬浮物颗粒充填含水介质空隙引起的机械堵塞为砂柱堵塞的主要原因,砂柱对回灌水具有明显的去除作用,但对回灌水中的有机物、还原性污染物去除作用有限,当回灌水的污染物浓度较高时,地下水将被持续污染.     

不同热调控策略下太阳能PV/T PCM系统性能实验研究

通过在太阳能集热器中添加饱和式脂肪酸相变材料,对太阳能光伏光热系统的不同热调控策略开展了实验研究。分析集热器中通水和不通水两种热调控策略对系统能量利用的影响。结果表明：相变材料可有效降低光伏板温度,但两种热调控策略下相变材料存在明显的温度分层现象;与不通水策略相比,通水策略在强化系统换热的同时促进了更多余热的回收,不通水和通水策略的热效率分别为71.3%和77.1%;通水策略可以更加有效地降低光伏板温度,缓解相变材料过热的影响,光电转化效率提高了7.3%。     

Mixing of thermal and non-thermal waters in the Steamboat Hills area, Nevada, USA

Groundwater monitoring began in 1985 at two geothermal facilities in the Steamboat Hills area, Nevada. Wells representing non-thermal, thermal, and mixed waters are evaluated by assessing temporal variations in B and Cl concentrations, water levels, and temperature. The objective is to assess the hydrologic and geochemical connection between the fractured bedrock geothermal reservoir and the alluvial aquifer. Results suggest that fault-controlled groundwater flow between the geothermal system and the alluvial aquifer is the dominant hydrologic process. Temporal trends suggest that the thermal water component in the alluvial aquifer has increased in most areas but decreased in at least one area.     

Performance analysis and parametric study of thermal energy storage in an aquifer coupled with a heat pump and solar collectors,for a residential complex in Tehran,Iran

Aquifers are underground porous formations containing water. Confined aquifers are the formations surrounded by two impermeable layers, called cap rocks and bed rocks. These aquifers are suitable for seasonal thermal energy storage.In the present study, a confined aquifer was considered to meet the cooling and heating energy needs of a residential complex located in Tehran, Iran. Three different alternatives were analyzed in this aquifer thermal energy storage (ATES), including: using ATES for cooling alone, for cooling and heating, as a heat pump, and for heating alone, employing flat plate solar energy collectors. A numerical simulation, based on the finite difference method, was carried out for velocity and temperature distributions as well as the heat transfer in the aquifer. The thermal energy recovery factor and the annual coefficient of performance of the system were determined under various schemes of operation, revealing that the combination of the ATES with the heat pump, to meet both cooling and heating needs of the complex, is the best. The study was repeated for different aquifer properties.     

Experimental Study on Heat Transfer of Heated Falling Film Under Gas–Liquid Cross-Flow Condition

With the influence of the different gas Reynolds numbers and liquid Reynolds numbers on heated falling film heat transfer, an experiment was performed by noncontact thermal infrared imaging technology under the gas–liquid cross-flow condition. The results indicated that during the increase of liquid Reynolds number the thickness and thermal resistance of liquid film increased in the determined temperature of the heating water, which weakened the heat transfer of the liquid film. However, the increase of liquid Reynolds number strengthened liquid film turbulence and therefore enhanced heat transfer. Under the synergistic effect of these two factors, there should be an optimal liquid Reynolds number that minimizes thermal resistance and maximizes the heat transfer coefficient of the liquid film. Temperature plays an important role in heat transfer of laminar liquid film flow. However, the heat transfer of turbulent liquid film flow is not sensitive to liquid film inlet temperature.     

The detection of groundwater flow by precise temperature measurements in boreholes

The flow of water is a very effective means for the transfer of heat, and one method of detecting such flow is to make precise temperature measurements at closely spaced intervals in a borehole that intersects a flow zone. Water can flow through permeable formations; within a borehole it can flow between two aquifers or fracture systems; it can flow into a fracture system during the drilling of a borehole; and it can flow up or down narrow, dipping fracture zones. Each of these phenomena produces a characteristic thermal signature on a borehole temperature log that can be modelled mathematically. Analysis of such thermal anomalies permits, therefore, a quantitative estimate to be made of the amount and rate of fluid flow. In principle, very small flow rates can be detected from their thermal effects, but in practice other factors, such as thermal conductivity variations, can cause variations in thermal gradients that limit the detectability. Anomalies that persist over large depth ranges compared with the diameter of the borehole can generally be interpreted unambiguously. Examples of each type of flow are given.     

突扩燃烧室内回流区长度研究

讨论了热过程对圆管突扩回流流动的影响,数值计算的结果表明：圆管突扩流动中,加热使流动方向上的逆压梯度降低,从而使回流区长度减小,在此基础上,用均匀热源的方法来模拟热态的燃烧过程,对层流、湍流状况下分别拟合出回流区长度与燃烧温度的近似关系,以便能通过冷态的数据预测热态回流区长度