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采用有限时间热力学研究了传热热阻,内部摩擦和冷头热漏三种不可逆损失对制冷机最优性能的影响。导出具有传热热阻,内部摩擦和冷头热漏不可逆损失的不可逆卡诺制冷机的最大制冷系数。 相似文献
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建筑墙体表面的太阳直射辐射投影及辐射强度随时间发生很大变化,该变化在已有的动态热过程算法框架内很难直接计算。根据建筑传热模型特点和计算机图形学原理,构建了动态热过程的建筑几何模型,该模型将建筑空间抽象为由矢量平面围成的空间区域的集合;提出了建筑几何模型的核心计算方法,即三维空间内直线与表面的矢量运算。该建筑几何模型能解决建筑动态热过程中直接计算建筑墙体表面之间的太阳直射辐射换热和太阳直射辐射投影等问题,并对空气流通、楼房之间的相互遮阳和光污染等问题的研究也具有实际意义。 相似文献
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本文在线性不可逆热力学范围内讨论了弹性体和考虑热传导及功转化为热两类不可逆现象的拟弹性体的热力学关系,在此基础上导出了相应阻尼阵的表达式。 相似文献
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本文建立了辐射板供冷与风机盘管结合的复合供冷方式下实验房间的传热传湿模型,提出将辐射板看作一种特殊的"表冷器",在处理室内空气时分干工况和湿工况两种情况:在干工况下辐射板对空气实施局部等湿冷却;在湿工况下辐射板对空气实施减焓、减湿冷却。在夏季工况对辐射供冷系统的温湿度等参数进行了实验测量,并将室内各状态点表示在焓湿图上,计算得到风机盘管与辐射板各自所承担的负荷大小。结果表明:当辐射板通水温度为20℃时,辐射板只承担显热负荷,大小为0. 85 k W;当辐射板通水温度为10℃时,辐射板在湿工况下运行,所承担的潜热负荷为0. 10 k W;得到了基于焓湿图的控制辐射板不结露的临界热力学条件,即辐射板送风状态点与室内空气状态点的焓值相等。 相似文献
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从不可逆热力学角度出发,建立了有一定通用性、能涵盖各类冻融损伤要素的熵产理论分析方法。基于经典Pennes生物传热方程,导出了描述活体组织传热过程熵产率的热力学模型,初步提出了用以刻画低温手术过程中组织冻融损伤程度的公式,在此基础上,采用有限元数值计算并借助熵产公式,就血液灌注率、代谢产热及手术时间等因素对手术疗效的影响进行了考察,为从组织层次定量刻画低温手术过程中的冻融损伤提供了新的理论途径。 相似文献
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本文论述了红外辐射测温中各种干扰的分类和各种干扰产生的机理。这些干扰包括光路中的干扰、外来光干扰和黑度变化产生的干扰。文中还叙述了克服或减小上述各种干扰的措施。最后叙述了杯形表面辐射温度计(又名前置反射器辐射温度计)的一般结构和原理。利用这种辐射温度计可以测量黑度大于0.5的任何工业表面的真实温度,这些表面可以是光滑的、粗糙的或者是静止的和移动的。 相似文献
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用有限时间热力学方法分析实际隐态制冷装置性能,导出了恒温和变温热源条件下实际闭式回热式布雷顿制冷循环制冷率与压力比和制冷系数与压力比之间的解析关系。考虑了不可逆性包括高,低温侧换热器和回热器的不可逆传热损失,压缩机和膨胀机中的非等熵压缩和膨胀损失,以及管路系统中的压力损失,通过优化两个换热器和回热器之间的热导率分配或传热面积分配可得循环最优性能,由数值算例给出了各项损失对循环制冷率和制冷系数的影响。 相似文献
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燃气辐射供暖系统辐射管发射率对室内热环境的影响研究 总被引:2,自引:0,他引:2
在对物理模型合理简化的基础上,对燃气辐射供暖空间温度场的分布进行了模拟,指出辐射管不同发射率对空间温度场的影响,指出提高辐射管黑度可强化燃气辐射供暖技术。 相似文献
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考虑工质与热源间的传热不可逆性及绝热压缩和膨胀过程中的摩擦阻力不可逆性,建立了不可逆卡诺制冷机的理论模型。采用有限时间热力学理论,导出不可逆卡诺制冷机的优化性能关系。对所得的结论进行了有意义的讨论。 相似文献
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The development of an energy efficient and economical modified jacketed vegetable storage concept and design is presented. Most fruits and vegetables require a storage environment near 0°C and 100%rh, which is difficult to achieve with conventional refrigeration systems. In a jacketed storage system, refrigerated air is circulated through air spaces surrounding the storage. High relative humidity levels can be achieved through the use of the large heat transfer surface of walls, ceiling and floor maintained at uniform temperature, and by preventing transmission heat gains into the storage space. While the jacket concept was initially introduced as a full jacket (covering walls, ceiling and floor), this paper discusses an alternative jacketed design which uses only the ceiling as a heat transfer surface. Based on construction simplicity, it is felt that this jacket design can be applied to conversion of conventional storage facilities and to new storage facilities. Acceptable relative humidity levels are attainable by the jacketed ceiling design with an extended heat transfer surface. It is expected that this concept will find favourable applications for storing fruits and vegetables wherever high humidity, medium temperature cold rooms are required. 相似文献
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在福州地区以天然能源为热泵冷热源的应用前景 总被引:2,自引:0,他引:2
以夏热冬暖地区城市-福州的气候、水文条件为基础,结合一住宅全年空调负荷的DOE-2.1模拟结果,分析在福州采用天然能源作为热泵的冷热源的应用前景,结果表明:(1)全年绝大部分时间内适合利用空气作为冷、热源;(2)闽江、内河周边的用户适合采用水源热泵;(3)温泉聚集地区不适合采用地下水和岩土作为冷源;(4)夏季适合联合使用岩土和辅助散热装置作冷源,冬季只使用岩土作热源。 相似文献
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本文利用居住建筑能耗模拟软件DeST-h,针对夏热冬暖地区的居住建筑,分析了窗墙面积比对建筑冷负荷的影响。通过对一典型实际住宅的模拟计算,得出了不同朝向夏季日照情况、窗墙比以及围护结构传热系数对建筑空调冷负荷的影响关系。 相似文献
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S. V. Puzach 《Journal of Engineering Physics and Thermophysics》2000,73(5):905-909
On the basis of numerical calculations by a three-dimensional mathematical model, the author revealed some special features
of heat and mass transfer within a building in the inflow of hydrogen at the floor level and subsequent detonation combustion
of a local hydrogen-air mixture upon its ignition on the ceiling surface. By generalizing calculation results, the author
obtained formulas for determining the height of a local explosion-hazardous zone which is formed above the source of hydrogen
inflow. It is shown that in detonation combustion, local explosion- and fire-hazardous zones near the source of ignition can
be destroyed and shifted to the lower and upper parts of the building toward the wall which is opposite to the opening.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 5, pp. 922–926, September–October, 2000. 相似文献
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Experimental analysis and modeling of hydronic radiant ceiling panels using transient-state analysis
Néstor Fonseca 《International Journal of Refrigeration》2011,34(4):958-967
The model developed in this investigation considers the hydronic panels as a transient-state heat exchanger connected to a detailed lumped transient model of the building. The behavior of the hydronic ceiling system and the interactions with its environment has been experimentally and numerically evaluated. This article presents the results of a study performed to develop a transient model of hydronic ceiling panels in heating or cooling modes and its environment (window, building structure, internal thermal loads and ventilation).Only the dry regime is considered in this case. Using as inputs the hydronic ceiling and room dimensions, material properties and the transient measurements of the air temperature at the adjacent zones, climatic conditions, supply air and water temperatures and mass flow rates, the model permits to estimate the water exhaust temperature, ceiling average surface temperature, resultant and dry air room temperatures, hydronic ceiling power and internal surface temperatures of the room in order to compare with measurements taken during the commissioning process. Two transient tests in heating and cooling modes are used to the experimental validation. 相似文献
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Traditional roof systems are constructed with concrete and weathering coarse layer and these roof systems absorb and reflect a certain amount of solar radiation. The absorbed solar energy is transferred into building indoor and causes significant discomfort to the occupants. Also, this solar energy gets dissipated without any useful energy conversion. Hence this paper is focused to use the available solar energy effectively through a novel solar water heating system and the transfer of heat in the building indoor is arrested by proper roof insulation material. The modified insulated roof with the solar water heater is designed and simulated numerically in commercial computational fluid dynamics code with validation. Through this study, the factors that affect the performance of solar water heating system and thermal insulation capacity are analysed and the best design of the modified roof system is identified. The modified roof system produces 25 L of hot water per day with a temperature raise of 60°C in the winter season. Also, the same roof system maintains the ceiling temperature at about 27°C for a complete day in a summer season. 相似文献
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陶求华 《制冷空调与电力机械》2010,31(4):49-53
夏热冬暖地区夏季闷热,通过外窗进入的太阳辐射热量较大。本文以厦门为例,首先分析了外窗玻璃太阳辐射得热数学模型,指出采用建筑贴膜技术可有效解决夏季太阳照射带来的室内过热。其次,分析了办公建筑侧窗采光数学模型,指出外窗玻璃贴膜减弱了建筑自然采光,增加照明能耗,外窗玻璃贴膜应综合考虑照明和空调能耗。为兼顾空调制冷与照明的能耗平衡,本文采用建筑环境模拟分析软件DeST,在6mm普通玻璃上采用10种不同性能的玻璃贴膜,模拟分析各种贴膜对建筑照明能耗、空调能耗的影响。最后得到夏热冬暖地区办公建筑适合的玻璃贴膜性能范围。 相似文献