共查询到20条相似文献,搜索用时 15 毫秒
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Heat transfer around vertical ground heat exchangers is a common problem for the design and simulation of ground-coupled heat pump (GCHP) systems. Most models are based on step response of the heat transfer rate, and the superposition principle allows the final solution to be in the form of the convolution of these contributions. The step response is thus a very important tool. Some authors propose numerical tabulated values while others propose analytical solutions for purely radial problem as well as axisymmetric problems. In this paper we propose a new analytical model that yields results very similar to the tabulated numerical ones proposed in the literature. Analytical modeling offers better flexibility for a parameterized design. 相似文献
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Y.H. Yau 《Energy and Buildings》2008,40(5):917-925
In two earlier papers [Y.H. Yau, Application of a heat pipe heat exchanger to dehumidification enhancement in tropical HVAC systems—a baseline performance characteristics study, International Journal of Thermal Sciences 46 (2) (2007) 164–171; Y.H. Yau, The analysis of enthalpy change with and without a heat pipe heat exchanger in a tropical air conditioning system, International Journal of Energy Research 30 (15) (2006) 1251–1263], two series of experiments were conducted under controlled conditions to establish the baseline performance characteristics of the heat pipe heat exchanger (HPHX). In the present paper, a complete empirical transient systems simulation program model is assembled to estimate the air states as well as the entire typical meteorological year energy consumption of an operating theatre located in Kuala Lumpur, Malaysia. 相似文献
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The in situ thermal response test provides an effective method to determine the ground thermal properties required for the design of a geothermal energy installation. This paper presents a unique compact testing device for in situ thermal response testing based on a previous, trolley-based unit. Modernisations in the presented new apparatus enable the time and cost of the test to be reduced and offer enhanced flexibility and application potential for in situ thermal response testing. The methodology adopted for the test, including the theoretical approach for the evaluation of test data, together with an outline of the design and workings of the apparatus are presented. A case study is also shown for the verification of the quality of the results. 相似文献
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More and more efficient solutions of thermal insulation of buildings result in an increasing role of ventilation in the energy balance of buildings. This leads to a necessity for seeking unconventional heat sources, as well as development of the exhaust air heat recovery methods. The use of heat accumulating potential of the ground perfectly fits into this trend, allowing natural pre-heating and pre-cooling of the inlet air. There appears to be very limited research and published data on their thermal performance in Poland. This paper introduces a developed method of air-ground heat exchanger (AGHX) performance evaluation together with its validation and research results of conducted simulation. The AGHX model (based on a quasi 3D finite elements method) allows analysis of energy performance dependence on a wide range of parameters including AGHX geometrical configuration, mode of operation and environmental factors. The simulation results indicate that the analyzed parameters in various degrees affect the thermal efficiency of AGHX; various is also the nature of their impact. For some of them it is possible to set a value to maximize heat or cold yield (pipe diameter and placement depth, number of parallel pipes, bypass system, soil thermo-physical parameters, ground area shading and ground surface cover). In other cases, the influence of parameters has an asymptotic nature for which the maximum heating or cooling efficiency is achieved for parameter values tending to infinity (pipe length and distance between parallel pipes). 相似文献
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The thermal performance of an enthalpy/membrane heat exchanger is experimentally investigated. The heat exchanger utilizes a 60gsm Kraft paper as the heat and moisture transfer surface for HVAC energy recovery. The heat exchanger sensible, latent and total effectiveness have been determined through temperature and moisture content measurements. The annual energy consumption of an air conditioner coupled with an enthalpy/membrane heat exchanger is also studied and compared with a conventional air conditioning cycle using in-house modified HPRate software. The heat exchanger effectiveness are used as thermal performance indicators and incorporated in the modified software. Energy analysis showed that an air conditioning system coupled with a membrane heat exchanger consumes less energy than a conventional air conditioning system in hot and humid climates where the latent load is high. It has been shown that in humid climate a saving of up to 8% in annual energy consumption can be achieved when membrane heat exchanger is used instead of a conventional HVAC system. 相似文献
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In this paper a methodology for comparative evaluation of design alternatives of cast-in-place energy piles (EPs) is presented. The methodology proposes the comparison to be based on the difference between the temperature of fluid in the pipes and the temperature at the axis of the pile, under a constant heat injection rate in a homogeneous infinite concrete - ground solid, for a period that the thermal influence between all the pipes has been developed, while the conductive heat transfer along the pile is not significant. It is proved that the temperature at the axis of an EP does not depend on the number of the pipes, thus behaving as a reference temperature at a given time for an EP of a given diameter. The difference between the mean fluid temperature in the pipes and the temperature at the axis of the pile is analysed in four components. It is proved that only one of these components depends on time, and it is common in all EPs of the same diameter, the other three depending on the basic design parameters of the EPs, i.e. the number of pipes, the type and dimensions of pipes and the heat/flow characteristics in the pipes. EPs with different design parameters can be compared, the comparison based on the, easily calculated, constant in time temperature difference between the fluid and the axis of the pile. 相似文献
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Terrestrial laser scanning, also known as Light Detection and Ranging (LiDAR) is an emerging technology that has many proven uses in the geotechnical engineering community including rockmass characterization, discontinuity measurement and landslide monitoring. One of the newer applications of LiDAR scanning is deformation monitoring and change detection. In tunnels, deformation is traditionally measured using a series of five or more control points installed around the diameter of the tunnel with measurements recorded at regular time intervals. LiDAR provides the ability to obtain a more complete characterization of the tunnel surface, allowing for determination of the mechanism and magnitude of tunnel deformation, as the entire surface of the tunnel is being modeled rather than a fixed set of points. This paper discusses terrestrial LiDAR scanning for deformation mapping of a surface and for cross-sectional closure measurements within an active tunnel using an elliptical fit to data for profile analysis. The methods were found to be accurate to within a few millimeters when measuring 58 mm of diametric difference over an 18.3 m diameter circular profile, even when some sections of the data were removed from the analysis. 相似文献
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In this paper we investigate of energetic and exergetic efficiencies of ground-coupled heat pump (GCHP) system as a function of depth trenches for heating season. The horizontal ground heat exchangers (HGHEs) were used and it were buried with in 1 m (HGHE1) and 2 m (HGHE2) depth trenches. The energy efficiency of GCHP systems are obtained to 2.5 and 2.8, respectively, while the exergetic efficiencies of the overall system are found to be 53.1% and 56.3%, respectively, for HGHE1 and HGHE2. The irreversibility of HGHE2 is less than of the HGHE1 as about 2.0%. The results show that the energetic and exergetic efficiencies of the system increase when increasing the heat source (ground) temperature for heating season. And the end of this study, we deal with the effects of varying reference environment temperature on the exergy efficiencies of HGHE1 and HGHE2. The results show that increasing reference environment temperature decreases the exergy efficiency in both HGHE1 and HGHE2. 相似文献
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介绍了直接式和间接式地热供热系统调峰负荷的理论计算方法。重点分析了间接式地热供热系统调峰负荷随环境温度的变化,以及所受末端散热器设计、地热水与循环水换热器设计运行参数的影响。 相似文献
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The inevitable influence of large excavation in soft soils on nearby tunnels is of great concern in practice. In this paper, the influence of a nearby large excavation on existing metro tunnels of the Ningbo Metro Line 1 in sensitive soft soils is investigated and presented. Considerable displacement in the left tunnel closer to the excavation induced by the nearby excavation was revealed by field monitoring. Visible cracks and leakages were observed in left tunnel linings. Three dimensional numerical simulations are conducted to investigate the responses of the ground and left tunnel due to the adjacent excavation. The development of bending moment and displacement of the left tunnel during different construction stages of the nearby excavation is obtained. Then the interaction mechanism between the nearby excavation, surrounding soils and existing twin tunnels is investigated, which is of significance to the interpretation of the influence of the nearby excavation on the existing twin tunnels. Several protective measures for alleviating the influence of adjacent excavation on left tunnel are studied, including divided excavation, soil improvement and a cut-off wall. It is found that the left tunnel is influenced to varying degrees during different construction stages and the time effect is distinct for this large excavation in soft soils, which would be suggestive to engineers to pay more attention to the protection of adjacent tunnel during the crucial construction stages. The bending moment and displacement of the left tunnel is strongly related to the unloading effects and displacement of surrounding soils, which can be alleviated by means of proper improvement of excavation sequence. Comparatively, longitudinally divided excavation is more effective in protecting the left tunnel than soil improvement or a cut-off wall. This study is of certain reference value for protecting metro tunnels adjacent excavation in soft soils. 相似文献
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回顾了地下埋管新风系统的研究进展,介绍了地下埋管部分的换热计算,分析了影响地下埋管新风系统性能的因素,给出了工程应用实例,并针对系统存在的问题展望了今后的发展方向。 相似文献
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《Building Research & Information》2013,41(3):199-202
Research and development by Altechnica into the applied use of wind energy suggests the novel and innovative solution of employing buildings as primary wind collectors. Buildings can be designed with the means of extracting wind energy advantageously. The roof design of a building can direct and accelerate the wind flow to turbines along the ridge. Dr Derek Taylor of Altechnica introduces the idea of a wind energy system for (new and existing) buildings that can augment solar power, work for a range of building typologies and settings, generate electricity for the building and contribute into the larger electric grid. 相似文献
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Using buildings to harvest wind energy 总被引:1,自引:0,他引:1
《Building Research & Information》1998,26(3):199-202
Research and development by Altechnica into the applied use of wind energy suggests the novel and innovative solution of employing buildings as primary wind collectors. Buildings can be designed with the means of extracting wind energy advantageously. The roof design of a building can direct and accelerate the wind flow to turbines along the ridge. Dr Derek Taylor of Altechnica introduces the idea of a wind energy system for (new and existing) buildings that can augment solar power, work for a range of building typologies and settings, generate electricity for the building and contribute into the larger electric grid. 相似文献
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Model experiments for examining heaving phenomenon in tunnels 总被引:1,自引:0,他引:1
Shigekazu Seki Shinobu Kaise Yasutaka Morisaki Shinichi Azetaka Yujing Jiang 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2008,23(2):128-138
In recent years, heaving has occurred in pavement slabs in some expressway tunnels, adversely affecting road comfort and tunnel stability. When the heaving displacement is limited, the repair is limited to the overlay slabs. However, in the sections where the displacements are significant, the tunnel invert needs to be reconstructed and this brings many additional problems; for example, in reconstruction, traffic needs to be restricted which brings inconvenience to the public. In this study, model experiments as well as numerical analysis using the finite differential method (Code FLAC) were carried out to establish a rational measure facing to the heaving phenomenon. Based on the results of model experiments and numerical analysis, the validity of reproducibility of the model experiments has been examined, some characteristics of heaving phenomenon have been grasped, factors for estimating the heaving phenomenon in different loading patterns have been established. All these factors have important implications for future construction practice. 相似文献
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通过对地热能源的研究和调查,分析了地热能源在供暖方面的应用现状、作用及影响,同时总结出地热能源所具有的优势和不足,为地热能源的应用奠定了理论基础,以实现资源的节约。 相似文献
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A Window Energy Rating System (WERS) provides a simple, approximate method to compare the energy performance of the various windows and to determine the different potential savings for the various weather conditions. The main aim of this paper is to obtain a WERS for two climatic zones in Spain.For this purpose, the heating loads and energy savings of a residential building with different types of windows were obtained by three ways. Firstly, the energy through the window was evaluated considering only the climatic conditions. Secondly, the study was performed taking into account the energy useful for the heating system considering the climate and the type of building. Finally, the different cases were simulated using TRNSYS16 and WINDOW5. This study was performed for different European climates.The WERS proposed here is based on the second method. It takes into account the U factor of the window, U factor of the frame, absortivity of the frame, solar heat gain of the glazing and infiltration. 相似文献