Simulation of embedded heat exchangers of solar aided ground source heat pump system

Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 ℃ higher than the original one after one year's running. It is beneficial for the system to operate for long period.

THE SIMULATION ANALYSIS OF A PROPOSED‘HYDRONIC RADIATOR’SYSTEM TOWARDS LOW COST HOUSING OPERATION IN TEMPERATE AND HOT TROPICAL CLIMATES

Fuel poverty is one of the global concerns affecting not only users’financial capacity or affordability for maintaining housing operation but also the occupants’health and wellbeing.Space heating and cooling require a relatively large amount of domestic energy use in housing.Therefore,this study was formed with the aim to propose an innovative approach to utilising free,clean renewable sources of energy applicable to the space heating and cooling of housing in both cold and hot regions.Accordingly,housing test facilities based in Melbourne,Australia,and Kuching,Malaysia,were selected and used for this study that examined the thermal performance of a proposed‘hydronic radiator’(HR)system through simulation and onsite measurements.The geothermal heat capacity of a‘vertical ground heat exchanger’(VGHE)installed in the house in Melbourne was examined previously by the authors and the VGHE measured data was also applied to this HR performance simulation.The water that circulates through the HRs is heated by sunlight and VGHE or cooled by night sky radiation.This study drew conclusions that the sole utilisation of renewable sources through these proposed HR space heating and cooling systems can provide thermally accessible or comfortable indoor living environments in both heating or cooling dominant regions.Thus,fuel poverty issues may be alleviated through HR system application.The HRs can remove a‘sensible’portion of metabolic heat,but they cannot effectively contribute to the‘latent’heat removal.Thus,the future potential use or effect of‘flow-through’HRs,which are integrated into a underfloor air distribution(UFAD)plenum,was also dsicussed in this study.In the test house located in Melbourne,the flow-through HR UFAD system is currently under development.Therefore,the performance will be measured once the system has come into operation for further testing.

A Study on Comparison of Building Energy Simulation and Measurement Results for a City Hall

In recent years, the number of public office buildings which were built by the glass curtain wall increased rapidly, but through the results of the investigation of the government, these buildings have been found that the heating and cooling load is high, and showed low energy efficiency. So in this study, through energy simulation, the energy consumption of public office building was verified and measured;environment data and calculated data were compared to make more precise simulation. The heating and cooling load was calculated via EnergyPlus;building was modeled by Google SketchUp connected to EnergyPlus. The results of this study were as follows: in simulation, incident solar radiation from large curtain wall should be underestimated. And using site-measured outdoor environment data can increase accuracy of simulation result.

Radiation effect on magnetohydrodynamic flow with induced magnetic field and Newtonian heating/cooling:an analytic approach

The aim of the present analysis concerns the magnetohydrodynamic flow of fluid which is natural convective and electrically charged through two vertical insulated walls.Influences of radiative heat flux,induced magnetic field,and the Newtonian heating/cooling are taken.We found exact expressions for the temperature field,the velocity field,and the induced magnetic field by solving the set of dimensionless coupled governing equations.Further,we obtained the equations for induced current density,Nusselt number,skin frictions as well as mass flux.The influences of the several constraints like the magnetic,the radiation and the Newtonian heating/cooling on the profiles of the velocity,the temperature field,the induced magnetic field as well as the current density display with graphics.Moreover,the influence of these non-dimensional parameters on the skin frictions,the Nusselt number,and the mass flux is explored in tabular form.The outcome of the radiation raised the velocity,the temperature field,the induced magnetic field and the current density field in view of enhancing the thickness of the boundary layer.Also,the impact of Newtonian heating is to raise the velocity,temperature,induced magnetic field and induced current density,whereas all these fields have opposite behaviors in case of Newtonian cooling.

Radiative Cooling in Northern Europe Using a Skylight

The purpose of this paper is to present the design and performance of a skylight using a mathematical model. This model uses weather data from the Finnish city Helsinki to assess its performance. This skylight could act as a radiative cooler or as a thermal insulator depending on the need. This versatile usage would thus decrease the need for traditional air-conditioning and hence save electricity. The skylight would consist of one normal silica glass window and of two polymer windows with a grcenhousc gas trapped in the spaces between the windows. The skylight would be in its cooling mode when the two spaces would be connected to each other and insulating when disconnected. Thus when cooling, a natural convective flow transports heat from the 1o~ er part of the skylight to the upper part of the skylight where the greenhouse gas is cooled by radiative heat exchange with the sky.

Simulation of Radiant Heat Transfer on the Border of Coke Bed and Metal Surface of Heat Transfer Passage

The article is dedicated to the issues of heat transfer, radiant heat transfer in particular, between fluidized bed of coke and water-cooled panels arranged inside it in a staggered order. The model by A.F. Chudnovsky describing radiant heat transfer in a porous body (disperse medium) as applied to coke bed has been updated.

Achieving Cooler Soil as an Effective Heat Sink for Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia Tropical Climate

This research is intended to explore the capacity of Malaysia soil in becoming a more effective heat sink for the application of Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia. EAHE Cooling Technology consists of buried pipes underground where the ambient air is channeled through from the pipe inlet and produces cooler air at its outlet. Within the buried pipes, heat exchange process occurs between the air and the soil that surrounding the pipe. This building cooling technology has been applied in many countries, mostly in temperate or hot and arid climate where the diurnal temperature is large. However, minimal resources were found on the study of EAHE application to buildings in Malaysia, hence there is room to develop. A parametric study on EAHE cooling application in Malaysia was done through field experiment and concluded that among many parameters affecting the technology performance, the soil temperature which surrounded the pipe was the most influential factor. The study recommended to further reduce the soil temperature to achieve a cooler outlet temperature. In response to that, this research conducted a parametric study of soil temperature under three different soil surface conditions: bare, shaded with timber pallettes and insulated with used tyres at 1.0 m and 1.5 m underground. The data was logged for a month and the result has shown significant reduction in the soil temperature underground below the shaded and insulated soil surface as compared to below bare soil surface condition. The insulated soil surface produced the best result where the soil temperature was reduced up to 26.9°C. The main contribution of this paper is to highlight that the soil surface treatment can be used to reduce solar heat gain within the soil underground and thus improving the performance of EAHE Cooling Technology particularly for the application in Malaysia tropical climate.

Simulation and analysis for anthropogenic heat release

Heat balance of urban ecosystem is a key point for the study of urban climate and micro-climate pattern and its change mechanism. Urban heat island effect is becoming increasingly serious,which is mainly caused by the change of the earth's surface cover and the anthropogenic heat release. In this study,the simulation experiment for the anthropogenic heat release was designed according to the heat balance principle. A set of buildings of miniature city were used to constitute the residential area,U grooves were applied to simulate the single building,and the fluorescent lamps in the U groove were regarded as the heat sources of the anthropogenic heat release. The simulation experiment was launched with long-short wave sun photometer,sonic anemothermometer and heat flow gauge in the experiment site. Then the net solar radiation,sensible heat flux and heat flux into the ground were determined. The quantities of the anthropogenic heat release were calculated based on the heat balance principle,and were compared with the theoretical power consumption of the fluorescent lamps. The root mean square error( RMSE) of the simulation for the anthropogenic heat release reaches0. 078 W·m- 2,a comparatively high precision,which showes that the anthropogenic heat release can be accurately determined through the simulation experiments. This study provided a scientific method for the purpose of monitoring the anthropogenic heat release.

燃氢燃机高温高湿透平耦合传热和冷却特性

分析了燃氢燃机透平在导热/对流/辐射耦合作用下的流动传热和冷却特性,发展了能够计算高H_(2)O与CO_(2)分压比的灰气体加权和(WSGG)模型。结果表明:燃氢燃机工质中水蒸气含量增大导致金属壁面温度升高;加入辐射的影响后,H_(2)O和CO_(2)含量对传热的影响呈相反的结果,这主要是由于CO_(2)的对流传热能力强于H_(2)O,而H_(2)O的辐射能力强于CO_(2);在对流、导热、辐射3种传热方式都存在的燃氢透平冷却耦合系统中,气膜冷却的速度场几乎不受影响,而温度场则深受耦合及辐射的影响,所定义的耦合条件下气膜冷却效率能够表征燃氢条件下气膜的冷却性能,因此在燃氢燃机透平冷却的设计中,燃氢导致的热负荷恶化需纳入设计变量中。

钠液面高度对氩气空间耦合传热特性影响的实验研究

锥顶盖作为快堆主容器重要的压力边界之一,其结构的完整性对快堆的安全运行至关重要。锥顶盖结构完整性与其温度载荷密切相关,而温度载荷受氩气空间自然对流与辐射耦合传热特性影响显著,有必要开展深入研究。基于钠液面上部氩气空间传热特性实验台架,开展了氩气空间传热特性实验研究,测量了锥顶盖、氩气空间和主泵支承的温度分布,阐明钠液面高度对传热特性的影响。实验结果表明,随着钠液面高度的增加,锥顶盖和氩气空间的温度随之升高,而且在高钠温时现象更加明显。此外,钠液面高度对主泵支承的温度分布和周向温差影响微弱。通过开展氩气空间钠液面高度对传热规律的影响研究,可为建立实验装置与原型反应堆之间的温度映射关系提供参考。

严寒干热地区集热冷却联用系统试验研究

该文结合新疆地区昼夜大温差气候特性,在乌鲁木齐市搭建一套小型太阳能集热——天空辐射冷却两用系统,通过对比PE防风膜层数和测试不同流速工况下的系统运行结果来探究两用装置的集热/冷却潜力。试验结果表明:系统在日间集热模式下的最大进出口温升为6.40℃,最大瞬时集热功率为721.88 W/m^(2);夜间冷却模式下最大进出口温降为0.94℃,出口温度相对环境温降可达1.43℃,最大瞬时冷却功率为50.89 W/m^(2),这为其在实际中的工业集热应用和本地区的温湿度独立控制空调系统高温冷冻水制备提供可能。

采用冷却塔补偿的地埋管地源热泵热平衡系统控制研究

采用冷却塔补偿来减少夏季土壤排热量的做法是地埋管地源热泵最常见的一种热平衡措施,但目前与其相适应的控制策略尚不够完善。在此,针对采用冷却塔补偿的地埋管地源热泵热平衡系统,提出一种以效率优先和热量补偿双模式运行的控制策略。这种控制策略明确了冷却塔与地埋管双向切换的条件,可以在保持地埋管地下热平衡前提下提高地源热泵系统的工作效率,并能够自动适应不同负荷特点的建筑物。

氦氙气冷小堆燃料棒辐射散热特性分析

反应堆堆芯热工安全特性是反应堆系统安全特性最重要的组成部分。氦氙气冷小堆中燃料棒间温差大,辐射散热不可忽略。因此针对氦氙气冷小堆堆芯,不止需要考虑对流换热和热传导两种换热形式,也需要考虑辐射散热对堆芯换热的影响。本文通过建立氦氙气冷小堆堆芯1∶1精细化模型,开展反应堆堆芯内部三维辐射散热特性分析,同时获得辐射角系数。将本文模型计算结果与蒙特卡罗方法结果进行对比验证,两者相对误差小于1%,证明该辐射角系数计算方法的准确性。开展了燃料棒径距比、燃料棒表面温度、燃料棒长度等几何参数敏感性分析,关注其对燃料棒辐射散热特性的影响,并开发出一套具有普适性的堆芯内燃料棒辐射角系数经验关系式。本文通过研究燃料棒间辐射散热特性了解反应堆内辐射散热规律,为后续反应堆堆芯热工安全特性研究提供了技术支撑。

适用于地面装备的特种降温涂层研究与应用

[目的]为了有效降低太阳辐射引起的导弹温升,考察了一种针对地面装备的特种涂层的降温性能。[方法]通过基料与颜填料的筛选,确定以环氧树脂搭配固化剂作为基料,金红石型二氧化钛作为主要颜填料。对涂层方案及其作用机理进行分析后,确定了特种降温涂层的设计原则。对涂层建立了热传导模型,分析辐射来源,对地面装备进行了仿真分析。[结果]通过试样级试验验证了特种涂层的环境适应性与降温性能。[结论]该特种降温涂层解决了太阳辐射下地面装备内部升温较高的问题,为地面装备的应用打下了基础。

北京奥林匹克公园中心区广场下垫面热环境特征及材质优化研究

【目的】城市中大面积且连续的硬质下垫面是近地表热环境恶化的重要原因之一,下垫面反照率的增加通常能使地表环境变得凉爽。通过研究下垫面热环境特征与环境温度的关系,可以为缓解城市地表升温提供理论依据。【方法】以北京奥林匹克公园中心区广场为例,实测6种典型下垫面(沥青、透水混凝土、砖、花岗岩、砾石、草地)的地表温度,对下垫面热环境特征及温度区间进行相关性研究,并结合ENVI-met数值模拟法探究整体反照率对热环境的具体影响。【结果】硬质下垫面在四季均能加热空气,在相同环境条件下,所有参与研究的硬质下垫面中沥青最热,花岗岩最凉爽;在不同下垫面类型中,颜色深浅对表面温度的影响高于材料类型与表面粗糙程度差异的影响;在单日内不同的测试时间段,日温度均值较低的深色下垫面在某一时刻的瞬时温度可能会高于日温度均值较高的浅色下垫面;在一定区间内增加场地整体反照率可有效降温,场地温度降幅随反照率上升呈先升后降的单峰趋势,且研究区域内整体反照率约为0.56时热环境改善效益最佳。【结论】提出硬质下垫面材料选择及设置建议,为北京公共空间硬质下垫面设计提供参考和依据。

Ground experimental investigations into an ejected spray cooling system for space closed-loop application

Spray cooling has proved its superior heat transfer performance in removing high heat flux for ground applications. However, the dissipation of vapor liquid mixture from the heat sur- face and the closed-loop circulation of the coolant are two challenges in reduced or zero gravity space enviromnents. In this paper, an ejected spray cooling system for space closed-loop application was proposed and the negative pressure in the ejected condenser chamber was applied to sucking the two-phase mixture from the spray chamber. Its ground experimental setup was built and exper- imental investigations on the smooth circle heat surface with a diameter of 5 mm were conducted with distilled water as the coolant spraying from a nozzle of 0.51 mm orifice diameter at the inlet temperatures of 69.2 ℃ and 78.2 ℃ under the conditions of heat flux ranging from 69.76 W/cm2 to 311.45 W/cm2, volume flow through the spray nozzle varying from 11,22 L：h to 15.76 L·h. Work performance of the spray nozzle and heat transfer performance of the spray cooling system were analyzed; results show that this ejected spray cooling system has a good heat transfer performance and provides valid foundation for space closed-loop application in the near future.

城市水体斑块对热岛效应的缓解能力——以沈阳市为例

水体对环境具有调节作用,在城市生态系统中,水体通过冷却周围地表从而有效缓解热岛效应。采用Landsat影像分析了2000—2020年沈阳市辖区的城市热岛效应的演变情况,利用常规的水体斑块构建缓冲区并进行分析,通过冷却范围、冷却幅度和冷却梯度3个指标量化水体斑块对城市热岛效应的缓解能力,利用水体斑块的面积、形状指数和周围建成区占比定量分析了影响水体斑块缓解能力的因素。结果表明:(1)2000—2020年沈阳市城市热岛分布由中心城区向郊区扩展,热岛面积增加约40%;(2)水体斑块能有效降低周边建成区地表温度的平均距离为0.27 km,相邻建成区平均降温2.26℃,每距离水体边界1 km的建成区平均地表温度的降幅为8.28℃;(3)水体斑块的面积增加对冷却范围和冷却幅度有着极强的增强作用,水体斑块形状指数的增加也会增强冷却作用,而水体周边建成区占比的增加则会抑制水体斑块的冷却范围与冷却幅度,水体斑块的冷却梯度仅与周边建成区占比之间呈极显著的负相关,而与水体斑块的面积、形状指数无明显关联。

基于复合式热源的天棚辐射供暖系统在住宅中的应用

在我国实现“碳达峰、碳中和”目标的大背景下,为响应南方地区人民对冬季供暖的热切呼声,亟待探索出适合南方地区气候特点同时又兼顾经济性、环保性的住宅供暖方式。以南方地区某新建住宅小区为例,对该区域住宅小区集中供暖系统不同热源形式进行了分析比选。详细介绍了地源热泵与风冷热泵联合供暖的热源方案比选思路、系统设置及运行原理,重点对这两种热源不同搭配比例下的经济性进行了对比分析;总结了该系统能源机房及地源侧设计要点;介绍了改善地源热泵系统地源侧土壤冬、夏热量不平衡的方法;提供了天棚辐射系统夏季辅助供冷运行的判断条件;介绍了天棚辐射供暖末端在住宅中的设置方式及构造做法。

可再生能源在医疗综合体项目的应用实践

以地处夏炎冬寒地区的某医疗综合体项目为例进行探讨,分析了地源热泵集中供冷供热和热回收技术供应生活热水的技术方案及合同能源管理商业模式设计方案,分析了其经济、节能和环保效益,并对未来同类项目的复制和推广给出了合理建议。

基于[火用]损分析的地源热泵地板辐射供冷系统运行优化

随着地板辐射技术的普及,越来越多的办公建筑选择使用地源热泵耦合地板辐射系统供冷,系统的高效运行日益受到重视。文章以[火用]损作为评价指标,运用3台热泵优化济南市某办公大楼供冷系统。将系统分为地埋管子系统、地板辐射子系统和热泵机组子系统,并建立了对应的[火用]损模型。在MATLAB平台上,使用快速非支配排序遗传算法降低系统总[火用]损,同时以3台热泵的负荷分配为自变量,寻求最优解集。结果表明:当运用遗传算法优化运行策略时,总能找到最优解集,使系统总[火用]损降到最低,并得到了系统的最佳运行策略;优化后的地埋管换热器的[火用]损虽然增加,但系统的总[火用]损却降低了7.3%,一天内热泵机组能耗也降低了16.66 kWh,其节能率达到了9.2%;从[火用]损占比来看,地板辐射子系统的[火用]损占整个系统损失的66.3%,因此通过对地板辐射子系统的优化改进,能够有效改善整个系统的总[火用]损。