肋片几何参数对表冷器除湿性能影响的数值分析

对表冷器除湿性能进行数值计算,选取5个影响表冷器除湿性能的参数:肋片高度、肋片厚度、肋片间距、风速、冷壁温度。重点研究肋片结构参数对表冷器除湿性能的影响。采用正交方法进行实验设计,比较极差大小后发现,影响表冷器除湿性能的结构参数大小依次为肋片厚度、肋片间距、肋片高度,所占权重分别为54.97%、39.79%、5.24%;通过计算各个因素对表冷器除湿性能的显著性水平,得到肋片厚度对表冷器除湿性能有显著性影响。     

空气纵掠带顶端间隙的非标准错列肋片簇的换热及阻力性能的研究

利用萘升华技术，在Ｒｅ＝２０００－２２０００的范围内对有顶端间隙的非标准错列肋片簇的传热（质）及阻力特性进行了实验研究，给出了各个肋片位错情况下，Ｓｈｅｒｗｏｏｄ数及阻力系数ｆ随Ｒｅｙｎｏｌｄｓ数变化的拟合关系式，并综合分析了肋片位错对非标准错列肋片簇的传质（换热）及阻力性能的影响，所得结论可供工程设计时参考。     

肋片的强化传热和调温作用

本文阐述了肋片强化传热的原理；分析了肋片最佳形状和尺寸确定的计算式；提出了肋片在强化传热、调节壁温中的正确布置方法。     

梯形剖面圆形肋片管温度场的研究

提出了一种新的梯形剖面肋片管沿肋高（即沿肋根致肋端方向）温度分布计算方法,实测结果表明这一计算方法有较高精度,实验同时显示了沿肋宽方向（即沿肋片的厚度方向）的温度分布不均匀性,对环肋结构优化有重要参考作用。     

梯形肋片管表面温度的试验与计算

以几种不同形状的梯形肋片管为研究对象 ,通过建立试验台 ,模拟了肋片的多种工况 ,得到了肋片的实际温度分布 ,继而从理论上对肋片的温度和传热量进行了推导计算 ,最后 ,对两者进行了对比 ,并分析了结果     

扰流孔和片距对矩形翅片椭圆管换热性能的影响

本文采用热质比拟技术研究了矩形翅片椭圆管的换热特性.矩形翅片上的苦干扰流孔能起到加强流体扰动,增强换热的目的.实验发现:扰流孔数目,位置和翅片间距对换热影响较大,翅片表面开设8个和10个扰流孔可使换热增加30%.中问位置的扰流孔对换热起的作用不大.本文还得出了不同扰流孔下单排管的Sh～Re准则数的关联式,图8参8     

纳米颗粒协同肋片强化相变材料传热性能试验

以石蜡作为相变材料(phase change material,PCM),设计并搭建了一套PCM传热强化试验系统,在PCM中加入了高导热率纳米颗粒和金属肋片,结合温度数据采集系统对PCM熔化过程进行了试验测试,对PCM内部不同测点的温度变化趋势进行了分析,研究了纳米颗粒质量分数和肋片数对PCM传热性能的影响。结果表明：添加纳米颗粒可有效提升PCM温升速率,0.06%(质量分数,余同)石墨烯/PCM温升速率较高,与其他组分的石墨烯/PCM相比传热效果更好;加入肋片可加快PCM内部温度响应,9肋片/PCM的整体传热性能优于其他数量的肋片/PCM;纳米颗粒协同肋片结构可促进PCM传热性能的提升,9肋片、0.06%石墨烯/PCM与9肋片、0.09%石墨烯/PCM启动时间早,温升幅度高,传热性能好,为强化PCM传热性能中的较优组合。     

冷却肋片对光伏板发电性能的影响研究

研究了被动式冷却条件下肋片对光伏板发电性能的影响,分析了光伏板倾角、太阳辐射强度、环境温度和风速等因素对光伏板发电效率和发电功率的影响规律,对带冷却肋片和不带冷却肋片的光伏板进行了实验对比。研究结果表明,在实验条件下,安装冷却肋片可以使光伏板的发电效率提高0.3%~1.8%,发电功率提高1.8%~11.8%。     

肋片管在对流式过热器中的应用

肋片管能大幅度地扩展受热面积 ,减少锅炉对流受热面的布置空间和重量 ,目前已广泛用于锅炉省煤器部分。实践证明 ,它对提高锅炉安全、经济性有重要意义。由于锅炉过热器的工作条件和省煤器不同 ,因而限制了肋片管技术在过热器中的应用。针对中压锅炉和具有类似工作条件的余热锅炉 ,讨论肋片管应用于过热器的使用条件以及应当注意的问题。认为在烟温小于 75 0℃且管内蒸汽温度较低条件下 ,只要保证管内蒸汽足够的冷却条件 (α2 )采用低肋片的过热器的管壁温度和肋端温度是能保证其安全运行的。     

导流片结构对物流分配性能影响的实验研究

通过板翅式换热器物流分配问题的实验研究发现,不合理的导流片结构造成板翅式换热器内部物流分配极不均匀,以及在横向与纵向上物流分配不均匀的程度也不相同。同时提出了具有补液腔的新型导流片结构,并定义了新型导流片的结构参数。实验结果表明,采用新型的导流片可以有效的改进换热器内部物流分配不均匀的问题,同时还发现在实验的条件下结构参数为0．2的导流片具有最佳的导流性能,通过实验研究得到了不同导流片结构的物流分配不均匀特性与流体雷诺数之间的关系式。     

表冷器热工性能数值模拟的探讨

表冷器是空调机组的核心部件,通常的热性能计算都以试验为基础。提出一种数值模拟方法,从最基本的结构参数来计算表冷器的热性能。按此方法所编制的计算程序经过试验验证,已经取得了预期的效果。     

Experimental investigations of a small-scale solar-assisted absorption cooling system

The present study deals with a small-scale solar-assisted absorption cooling system having a cooling capacity of 3.52 kW and was investigated experimentally under the climatic conditions of Taxila, Pakistan. Initially, a mathematical model was developed for LiBr/H₂O vapor absorption system alongside flat-plate solar thermal collectors to achieve the required operating temperature range of 75°C. Following this, a parametric analysis of the whole system was performed, including various design and climate parameters, such as the working temperatures of the generator, evaporator, condenser, absorber, mass flow rate, and coefficient of performance (COP) of the system. An experimental setup was coupled with solar collectors and instruments to get hot water using solar energy and measurements of main parameters for real-time performance assessment. From the results obtained, it was revealed that the maximum average COP of the system achieved was 0.70, and the maximum outlet temperature from solar thermal collectors was 75°C. A sensitivity analysis was performed to validate the potential of the absorption machine in the seasonal cooling demand. An economic valuation was accomplished based on the current cost of conventional cooling systems. It was established that the solar cooling system is economical only when shared with domestic water heating.     

蓄能型液体除湿蒸发冷却系统中除湿性能的实验研究

提出了一种新型空调系统——液体除湿冷却空调系统的设计方案并搭建一功率为3kW的实验台，考虑到除湿过程和再生过程是该系统性能优良的决定性环节，设计加工了水冷型波纹板降膜式结构的除湿器和以丝网填料作为内部填料的再生器。在此实验装置上对系统的除湿过程以及其蓄能能力特性进行了实验研究，得出影响该系统除湿能力、蓄能能力等方面的主要因素，为系统的优化设计和运行提供依据。     

Dynamic Models of Heating and Cooling Coils with One—Dimensional Air Distribution

This paper presents the simulation models of the plate-fin, air-to-water (or water vapour) heat exchangers used as air-heating or air-cooling and dehumidifying coils in the HVAC (Heating, Ventilation and Air-Conditioning) systems. The thermal models are used to calculate the heat exchange between distributing air and coil pipes and outlet temperatures of air and heat or chilled fluid. The aerodynamic models are used to account for the pressure drop of the air crossing the coil tubes. They can also be used to optimize the structures of such coils. The models are based on principal laws of heat and mass conservation and fluid mechanics. They are transparent and easy to use.In our work, a coil is considered as an assembly of numbers of basic elements in which all the state variables are unique. Therefore we can conveniently simulate the coils with different structures and different geometric parameters. Two modular programs TRNSYS (Transient System Simulation) and ESACAP are utilized as supporting softwares which make the programming and simulation greatly simplified. The coil elements and a real coil were simulated. The results were compared with the data offered by the manufacturer (company SOFICA) and also with those obtained using critical methods such as NTU method, etc. and good agreement is attained.     

吊顶辐射冷却塔供冷系统试验研究与性能分析

通过供冷试验及TRNSYS软件模拟研究了吊顶辐射冷却塔供冷系统的运行效果,分析了气象参数、部件结构等因素对系统供冷效果的影响,并与常规供冷系统全年的运行能耗进行对比。试验与理论分析结果表明,吊顶辐射冷却塔供冷系统的有效供冷量能够满足用户供冷需要,供冷房间温度稳定且分布均匀。冷却塔供冷效果与大气湿球温度、建筑内部负荷、热交换器结构等因素有关。辐射顶板末端与冷却塔供冷匹配性高,系统全年运行时数增加,应用于需全年供冷的建筑节能效果显著。     

五级自动复叠系统制冷剂组分实验研究

基于自动复叠制冷循环设计并搭建了实验系统,针对多级自动复叠制冷系统中混合工质的配比以及实际运行中循环特性的难题,利用气相色谱仪对五级自动复叠制冷系统中混合工质在各级的实际运行的成分进行了取样、检测和分析。经过多次调试,使系统达到-126 ℃的低温工况,并通过实验全面了解循环过程中各级的状态。结果发现,自动复叠制冷循环中制冷剂的配比对系统的运行压力、各级毛细管节流后的温度、各级中间换热器的换热温差等参数影响很大。研究为混合工质的运行成分分析提供了指导与建议。     

Experimental study of the effects of structured surface geometry on water spray cooling performance in non-boiling regime

Experiments were conducted to study the effects of enhanced surfaces on heat transfer performance during water spray cooling in non-boiling regime. The surface enhancement is straight fin. The structures were machined on the top surface of heated copper blocks with a cross-sectional area of 10 mm×10 mm. The spray was performed using Unijet full cone nozzles with a volumetric flux of 0.044–0.053 m³/(m²·s) and a nozzle height of 17 mm. It is found that the heat transfer is obviously enhanced for straight fin surfaces relative to the flat surface. However, the increment decreases as the fin height increases. For flat surface and enhanced surfaces with a fin height of 0.1 mm and 0.2 mm, as the coolant flux increases, the heat flux increases as well. However, for finned surface with a height of 0.4 mm, the heat flux is not sensitive to the coolant volumetric flux. Changed film thickness and the form of water/surface interaction due to an enhanced surface structure (different fin height) are the main reasons for changing of the local heat transfer coefficient.     

冷却空气量对涡轮冷却性能影响综述

涡轮冷却技术被广泛应用于航空发动机及燃气轮机涡轮研发中,冷却空气的引气量成为影响整机效率的重要因素之一。本文基于现代燃气轮机及航空发动机涡轮叶片采用外部冷却与内部冷却结合的复合冷却的技术发展背景,综述了国内外在冷却空气量对涡轮叶片冷却性能影响方面的研究进展,分析并总结了冷却空气量对气膜冷却、交错肋冷却以及对综合冷却效率的影响规律,并对未来的研究方向给出了一定的建议。分析表明：对气膜孔形状的探索是未来气膜冷却技术研究的重点;交错肋研究主要处于定性研究阶段,对定量研究方法的探索是目前的发展趋势;对综合冷却效率的研究还处于起步阶段,未来可以从外部冷却和内部冷却之间的相互作用关系方面对综合冷却效率开展进一步的研究。     

Experimental performance of a thermoelectric ceiling cooling panel

An experiment has been performed to investigate the cooling performance of a thermoelectric ceiling cooling panel (TE‐CCP). The TE‐CCP was composed of 36 TE modules. The cold side of the TE modules was fixed to an aluminum ceiling panel to cool a test chamber of 4.5 m³ volume, while a copper heat exchanger with circulating cooling water at the hot side of the TE modules was used for heat release. Tests were conducted using various system parameters. It was found that the cooling performance of the system depended on the electrical supply, cooling water temperature and flow rate through the heat exchanger. A suitable condition occurred at 1.5 A of current flow with a corresponding cooling capacity of 289.4 W which gives the coefficient of performance (COP) of 0.75 with an average indoor temperature of 27°C. Using thermal comfort test data in literature for small air movements under radiant cooling ceilings, results from the experiments show that thermal comfort could be obtained with the TE‐CCP system. Copyright © 2007 John Wiley & Sons, Ltd.     

Experimental performance of cooling photovoltaic panels using geothermal energy in an arid climate

In this study, an experimental prototype was built to examine the use of an underground water tank as a heat exchange medium with the soil to reduce photovoltaic (PV) panel operation temperatures and simultaneously improve PV efficiency. Three PV systems were evaluated: a benchmark PV panel without cooling (panel A); a PV panel with water spray cooling (panel B); and a PV panel with evaporative cooling (panel C). The cooling techniques in modules (B) and (C) were used to investigate the effects of underground water on the performance of PV panels in arid conditions. Four cases were devised as follows: spray panel back cooling (I), spray front and back cooling (II), spray front and back cooling using an Arduino controller (III), and repeating case III with different water flow rates (IV). Readings were taken from 9:00 am to 4:00 pm  from May to August. The experimental results showed that the use of underground water spray cooling led to reductions in the temperature of PV panel B, 14°C, 17.6°C, 18.8°C, and 22.7°C for cases I, II, III, and IV, respectively, when compared with the uncooled panel, and efficiency improved by 3.5%, 4.8%, 18%, and 23.1%, respectively.