共查询到20条相似文献,搜索用时 31 毫秒
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Young-Ju Kim Nam-Sub Woo Sung-Cheol Jang Jeong-Ju Choi 《Journal of Mechanical Science and Technology》2013,27(8):2513-2521
This study investigates the economic feasibility of a hybrid renewable energy system (HRES) that uses geothermal and solar heat sources for water heating, space heating, and space cooling in a residential building in Korea. A small-scale HRES consists of a geothermal heat pump for heating and cooling, solar collectors for hot water, a gas-fired backup boiler, and incidental facilities. To determine whether the HRES will produce any economic benefits for homeowners, an economic analysis is conducted to compare the HRES with conventional methods of space heating and cooling in Korea. The payback period of a small-scale HRES is predicted as a maximum of 9 yrs by life cycle costing based on a performance index compared with conventional systems. However, the payback period of large-scale HRES above 400 RT is 6 yrs to 7 yrs. 相似文献
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A most common and economical way of utilizing solar energy is to use a flatplate collector to capture incoming solar energy
by heating either liquids or gases. Therefore, a solar collector should be the most critical part of the performance necessary
for the system, since maximum available heat depends solely on the collector. In the present investigation, considering that
most heat loss from solar collectors results from the natural convection between an absorber plate and a coverglass,it has
been demonstrated that this natural convection can be suppressed and heat performances of a solar collector are enhanced by
placing thin and poorly conducting honeycomb material between an absorber plate and a coverglass. By suppressing natural convection
within collector spacing it has been shown experimentally that honeycomb structures effectively raise critical Rayleigh number,
since they provide more shear surfaces. 相似文献
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In this paper, the performance of an ejector cooling system with constant-area mixing chamber was investigated at low generator temperatures. The cooling system was tested by using hot water as driving fluid and R123 as working fluid. The effects of operating temperatures on the cooling capacity and on the coefficient of performance (COP) of the system were experimentally investigated at an ejector area ratio of 7.17, which is suitable for solar cooling. As a result, COP of 0.42 was obtained at a vapor generator temperature of 74°C, evaporator temperature of 10°C, and at a critical condenser temperature of 29°C. A solar application of the system with single-glazed selective-type collectors in a horizontal position was conducted as a preliminary study. In the solar application, a cooling capacity of 1080 W for a 9.2 m2 collection area at an evaporator temperature of 10°C was obtained. 相似文献
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为解决原油输送过程中易结蜡,不易流动的问题,利用太阳能代替部分传统能源对工业锅炉24h给热,提供伴热软化水,实现了能源消耗的降低和环境保护。提出了油品储运伴热软化水太阳能预热系统,该系统主要应用于场地受限、高热值、高能耗及高污染工业上,具体表现为将太阳能高效集热装置、储热设备与工业锅炉进行结合改造,为锅炉提供预热软水,并且结合相变储热原理以满足出水温度达到工业要求,保证锅炉太阳能集热器完整、连续地运行。在理论研究的基础上,展开了大量的实验,实验结果验证了该系统的可靠性。研究结果表明,预热系统在日问日照充足时,集热效率高,相变蓄热器具有较好地蓄热和放热效果,放热时间能持续5h-7h以上,满足了原油输送过程对热水的需求。 相似文献
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Nguyen Kim-Bao Yoon Seok-Hun Choi Jae Hyuk 《Journal of Mechanical Science and Technology》2012,26(1):251-258
This study experimentally investigated the effect of the working-fluid filling ratio (FR) and the cooling-water flow rate
(CWFR) on the top heat loss and the performance of a solar collector equipped with a closed-loop oscillating heat pipe (CLOHP).
The CLOHP was composed of a heating section, a cooling section, and an adiabatic section; it had a 0.002-m internal diameter
and eight turns. The heating section was attached to a copper plate coated with black chrome, which absorbed energy from a
solar simulator that had 12 halogen lamps and was controlled by a voltage regulator. The cooling section was inserted into
the collector’s cooling box, which was made of a transparent acrylic plate. The FR of the working fluid ranged from 30% to
80% with a 10% interval, and the CWFRs were 0.15 l/min, 0.30 l/min, and 0.45 l/min. The experimental results show that the
solar collector equipped with the CLOHP has good performance at working-fluid FRs of 60% and 70% with low flow rates of 0.15
l/min and 0.30 l/min. 相似文献
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《流体机械》2015,(12):77-82
对太阳能燃气热泵供暖系统及余热回收性能进行了研究。建立了系统的仿真模型,对套缸冷却系统和排烟余热回收器进行了模拟计算。分析了套缸冷却水流量的变化规律、确定了排烟余热回收比(排烟余热中回收的热量占排烟余热总热量的比例)、热回收循环水流经套缸冷却器及排烟余热回收器后的温升情况,最后以沈阳地区某建筑为例,对系统余热回收的经济性进行了分析。结果表明:发动机转速每增加100r/min,所需的套缸冷却水流量增0.285~1.21g/s;排烟余热回收比为0.7时,系统可以获得最大的能源利用率(是指有效利用部分与总能源量的比值);热回收循环水流经套缸冷却器后温度上升2~5℃,在最佳的余热回收比下,热回收循环水流经排烟余热回收器后温度可提高2℃左右;运行时间超过2年时,余热回收型太阳能燃气热泵比非余热回收型太阳能燃气热泵更加经济。 相似文献
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相变储热有着密度高、体积小、质量轻,蓄放热过程中温度波动小等优点,在太阳能热利用、工业余热回收、采暖及空调等领域有着较为广泛的应用。本文利用相变储热试验平台模拟储热器的工作原理,对储热器不工作状态下内部和外部温度进行监测,发现相变储热器在非稳态散热时具有比较明显的凝固放热现象,而且通过顶面的热损失严重;对储热器热损失进行了分类,对储热器热损失系数这一关键数据进行探讨;最后,在试验和理论分析基础上提出增大上部保温层厚度、加强进出口部位的保温、减小管径和增加阀门可减小储热器通过顶面的热损失。 相似文献
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现代民用飞机座舱内设置有众多的设施包括座椅、内壁、生活设施等都具有明显的蓄放热特征。而在热载荷动态计算过程中,舱内设施蓄、放热性能对空调系统加热、制冷负荷有显著影响。在这些舱内设施中,座椅所具有的热容最大,并且其结构和边界条件及其复杂,座椅蓄放热特性对座舱动态热载荷仿真计算结果的准确性有很大影响。如果采用纯理论的方法,无法判断座椅动态建模中相关边界条件和系数的确定是否准确。因此本文将通过座椅动态热特性实验研究,对座椅的动态蓄放热特征数学模型进行验证。 相似文献
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给出了以太阳能辐射技术为基础的热能转换空调制冷技术的技术方法,即将太阳能转变成热能,使用热能进行制冷。以太阳能辐射技术的热能转换为基础,研制了新型的太阳能吸收式空调系统,并且通过实验研究,验证了该系统的集热、蓄热特性以及制冷机组的运行热性。实验表明,该空调系统可连续8 h稳定地工作,最大制冷量可达到47 kW,平均值也可达到4 kW,该空调系统性能参数COP,平均可达到03。因此,基于太阳能辐射技术的热能转换空调制冷技术为太阳能规模化、低成本应用提供了行之有效的新方法。 相似文献
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为了解决工业中的大量低品质烟气余热的回收利用和烟气酸露点腐蚀导致设备容易失效的工程问题,提出了一种复合中空热管传热元件,介绍了其结构及工作原理;对其内部传热机理进行了分析,并对其启动特性、等温性能和传热性能进行了试验研究。研究结果表明:复合中空热管在外管壁温度30℃时,加热时间2 min之内就能正常快速启动工作;在自然空气对流冷却条件下,具有较好的等温特性;复合中空热管的传热系数随着冷却水雷诺数的增加而增加;在加热蒸汽温度低于125℃的低温蒸汽加热条件下,当冷却水的雷诺数为6650时,复合中空热管的传热系数为1350W/(m2.℃)。试验研究结果为复合中空热管换热器的工程应用提供了基础。 相似文献
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Jeong Ho Lee Soo Young Kang Tong Seop Kim 《Journal of Mechanical Science and Technology》2012,26(11):3733-3740
This paper presents models for simulating the operation of a polymer electrolyte membrane fuel cell (PEMFC) system and the results of the dynamic simulations. The entire system included a PEMFC stack and balance-of-plant components such as an air supply blower, a membrane humidifier, a fuel supply unit, and a heat management unit. Mathematical modeling for the computation of power generation and heat transfer of the PEMFC stack, the heat and mass transfer of the humidifier, and the energy transfer of the cooling system was set up. Theoretical and experiential data such as the voltage-current density relationship of the cell stack and the performance maps of blowers and pumps, together with semi-theoretical heat and mass transfer equations, were used to represent the characteristics of all the components. The effect of the thermal inertia of solid parts was considered in the fuel cell stack, the membrane humidifier, and the radiator. System dynamic behaviors under various operating conditions due to changes in stack current and ambient temperature were predicted. The sudden abnormal operations of the cooling water circulation pump and the radiator fan were also simulated as an example of component malfunctions. 相似文献
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针对一种用于太阳能空调系统的分区蓄热水箱,对其运行情况进行了分析,结果表明,采用分区蓄热水箱来匹配太阳能空调能显著提高系统的性能.在夏季,分区水箱使得运行热水长时间内维持在较高温度,系统制冷COP也得以长时间维持在较高范围,虽然,在夜间无日照的情况下,系统的日工作时间减小了,但系统整体性能得以提高,尤其经过优化后,系统性能提升显著;同时,夏季的水箱结构较好地适用于冬季,在达到供暖要求的情况下,使得冬季系统的散热量降低,系统更为节能.总体而言,分区水箱应用于太阳能空调系统可以减小辅助能源的消耗,提高太阳能利用率. 相似文献
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直接甲醇燃料电池测试用温度控制系统 总被引:1,自引:0,他引:1
为了精确控制燃料电池阳极燃料的温度,搭建了直接甲醇燃料电池(DMFC)测试用温度控制系统。针对温度控制对象为定速流动的特点,设计了用于加热流动液体的特殊结构,即将不锈钢软管以双层跑道的布局紧密贴合于三层黄铜板之间,以延长液体在加热块中的流动时间,保证出口流动液体温度的精确控制。计算了不同内径的不锈钢软管最小管长和控制系统的最小加热功率。采用半导体制冷片为流体加热/制冷元件,设计制作了其功率驱动和换向电路。采用基于PID闭环控制的VC++程序设计方法实现了温度自动控制。实验结果表明:温度控制系统的平均升/降温速度为14℃/min,稳态温度控制示值误差±2℃,能够满足DMFC恒定温度条件下实时测试的要求。 相似文献
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The combined heat transfer and thermal stress analysis of thin cylindrical shells is considered in this and a subsequent paper. This paper presents two typical heat transfer models and the harmonic analysis which is used to represent the temperature distributions as double Fourier coefficients. These models are (i) a circular hot spot caused by a postulated loss of part of the internal refractory lining in a high temperature cylindrical reactor vessel and (ii) a heated “band” caused by solar heating on a horizontal storage vessel. In the case of the hot spot the inside and outside surface temperature distributions vary independently in the axial and circumferential directions, with linear transition through the thickness. In the simpler case of solar heating, the through-thickness temperature gradient is negligible and the temperature only varies around the circumference. The use of the double Fourier coeficients to obtain the displacements and stresses is described in Part II 相似文献