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热管及其换热器在烟气余热回收中的应用 总被引:5,自引:1,他引:4
简要介绍了热管技术,并分析了其传热机理。热管换热器具有许多独特的优点,已经获得了广泛的工业应用,应用主要集中在中低温余热资源回收利用方面,应完善高温热管,以拓宽热管换热器在高温余热资源中的应用。 相似文献
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根据纵向涡强化传热技术提出了新型的强化换热管——锥形内肋管,运用数值模拟方法,研究了新型强化换热管结构参数锥底宽度a、导程P、肋深e和Re数对Nu、沿程阻力系数f及传热综合因子η的影响。结果表明:换热管内壁面边缘处产生了较多的微小涡流,有效破坏了流动边界层,强化了传热。在充分湍流的条件下,流体Re越小、e越小,其综合传热性能越强。当Re<15 000时,a对η的影响要大于P;在过渡点后, P对η影响较大。通过综合传热性能分析,给出了适合不同Re区间的锥形内肋优化参数。 相似文献
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利用fluent软件中的太阳载荷模型对真空管家用太阳热水器进行了三维数值模拟计算,分析了30°、45°、60°倾角下真空管热水器内的流场和温度场随加热时间的变化及传热和流动过程。结果表明,真空管热水器在加热期间,在真空管管口的上壁面出现温度最大值,水箱内真空管管口以下水的温度相对于管口以上的温度分层很明显,水箱内真空管管口以上的热水温度几乎相同,说明水箱内管口以上的水进行了充分混合;对于30°和45°倾角的系统,随着加热时间的增加,水箱内管口以下的水温与管口以上的水温从10 K增加到30 K,以45°倾角为例,当考虑了水箱内管口以下的冷水区时,随着加热时间的增加,真空管与水箱内的温差从0.73 K增大到1.13 K,仅考虑水箱内均匀分布的三点时,随着加热时间的增加,真空管与水箱内的温差从0.15 K减小到了0.03 K;随着系统倾角从30°增加到60°,水箱内管口以下的冷水区域在逐渐减小。因此,为了减小水箱底部的冷水区,插入水箱内的真空管应尽可能短。 相似文献
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本文介绍了用于余热锅炉等传热部件的翅片管设计准则和翅片管结构型式和连接方法,分析了不同翅片管结构尺寸及型式对传热特性的影响,提出改善传热特性的途径。 相似文献
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有机热载体炉烟气余热回收技术浅析 总被引:2,自引:0,他引:2
长期以来,有机热载体炉排烟温度偏高,造成大量的能源浪费,严重影响了锅炉运行的经济性。为减少热能损失,对烟气余热回收技术的可行性方案、工程应用实例进行了阐述;并指出通过锅炉烟气余热利用技术回收排烟中的显热和潜热,可以大大提高有机热载体炉的热效率,实现节能降耗。 相似文献
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Consteel电炉余热锅炉的热平衡计算方法研究 总被引:2,自引:0,他引:2
针对Consteel电炉余热锅炉烟气入口参数不稳定的特点,得到了余热锅炉的各项热损失、锅炉效率、有效利用热量和蒸发量的计算公式。对65t Consteel电炉炼钢设备余热锅炉进行了热平衡计算,计算表明,锅炉的排烟热损失随烟气入口温度的降低而增加,而锅炉效率、有效利用热量和蒸发量随烟气入口温度的降低而降低,锅炉的平均蒸发量为23.1t/h。 相似文献
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为了研究双通道余热锅炉内烟气流场的分布情况,基于Fluent平台,采用可实现的k-ε双方程模型和多孔介质模型,对某钢铁厂双通道烧结余热锅炉内流场(压力场、温度场、速度场)进行数值模拟。结果表明,余热锅炉烟气阻力和炉膛出口排烟温度的数值模拟结果与锅炉实际运行结果比较符合,说明数值模拟准确度较高,理论模型可行;锅炉高温与低温烟气通道结合区域存在烟气走廊,结构不够合理;另外,锅炉进出口由于缺乏合适的导流装置,流场不均匀程度较大。研究结果可为双通道余热锅炉结构改进提供理论指导。 相似文献
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Investigation of a novel bayonet tube high temperature heat exchanger with inner and outer fins 总被引:1,自引:0,他引:1
Ting MaMin Zeng Yanpeng JiHaibin Zhu Qiuwang Wang 《International Journal of Hydrogen Energy》2011,36(5):3757-3768
In this paper, a novel bayonet tube high temperature heat exchanger (HTHE) with inner and outer fins is presented. It can be used in the ultra high temperature environment, such as hydrogen production, very high temperature reactor and externally fired combined cycle. Numerical investigation of heat transfer performance on the inside of bayonet element has been conducted for structure design. The numerical results suggest that the inner fin and inner tube should not be welded together. It is recommended that the air enters from the inner tube and exits from the annular space in the high temperature zone. A high temperature experimental system has been established to test the heat transfer and pressure drop characteristics of the HTHE. The surface area density of the tested HTHE is 6 times higher than that of the bare bayonet tube heat exchanger. The experimental results indicate that the mass flow rate on both sides and inlet temperature on the fuel gas side have a significant effect on the heat transfer rate and effectiveness, while the pressure drop ratios are mainly affected by the mass flow rate rather than the inlet temperature. Comparison between the tested HTHE and the similar HTHE without fins indicates that the proposed HTHE has a significant potential to improve the comprehensive heat transfer performance. 相似文献
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The third-generation heat transfer technologies, such as three-dimensional fin and dimple, are still important means of improving energy efficiency and will continue to be challenging issues. This paper presents condensation heat transfer performance of an edge-shaped finned tube fabricated by a ploughing–extruding process. The edge-shaped finned tube integrates more than one heat transfer enhancement technology and can enhance the heat transfer capacity greatly. It is seen that the overall heat transfer coefficient and heat flux increase with inlet velocity of cold water increasing, and decrease with inlet temperature of cold water increasing, whereas the shell-side heat transfer coefficient decreases with inlet velocity of cold water increasing and increases with inlet temperature of cold water increasing. At the same inlet velocity, the shell-side heat transfer coefficient for the edge-shaped finned tube is improved by 5–7 times compared to that of a smooth tube. At the same temperature difference between wall and vapor, the shell-side heat transfer coefficient is also higher than what had been reported in the literature. The shell-side heat transfer coefficient of the edge-shaped finned tube decreases with the increase of fabrication parameter feed at the same inlet velocity or inlet temperature of cold water. 相似文献
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转化气余热锅炉入口温度达到860℃,管壳程温差载荷较大,管板承受内压和温差载荷的双重作用,在管板管程侧、换热管管板部位和旁通管内部设计了防热材料,管板的管壳程的连接结构采用H型锻件,在温差载荷和管壳程设计压力相互作用的三种工况条件下,依据JB4732对设备相应部位进行应力评定,评定结果合格,为工程设计人员提供可参考的数据。 相似文献
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Parabolic trough solar collector (PTSC) is one of the most proven technologies for large‐scale solar thermal power generation. Currently, the cost of power generation from PTSC is expensive as compared with conventional power generation. The capital/power generation cost can be reduced by increasing aperture sizes of the collector. However, increase in aperture of the collector leads to higher heat flux on the absorber surface and results in higher thermal gradient. Hence, the analysis of heat distribution from the absorber to heat transfer fluid (HTF) and within the absorber is essential to identify the possibilities of failure of the receiver. In this article, extensive heat transfer analysis (HTA) of the receiver is performed for various aperture diameter of a PTSC using commercially available computational fluid dynamics (CFD) software ANSYS Fluent 19.0. The numerical simulations of the receiver are performed to analyze the temperature distribution around the circumference of the absorber tube as well as along the length of tube, the rate of heat transfer from the absorber tube to the HTF, and heat losses from the receiver for various geometric and operating conditions such as collector aperture diameter, mass flow rate, heat loss coefficient (HLC), HTF, and its inlet temperature. It is observed that temperature gradient around the circumference of the absorber and heat losses from the receiver increases with collector aperture. The temperature gradient around the circumference of the absorber tube wall at 2 m length from the inlet are observed as 11, 37, 48, 74, and 129 K, respectively, for 2.5‐, 5‐, 5.77‐, 7.5‐, and 10‐m aperture diameter of PTSC at mass flow rate of 1.25 kg/s and inlet temperature of 300 K for therminol oil as HTF. To minimize the thermal gradient around the absorber circumference, HTFs with better heat transfer characteristics are explored such as molten salt, liquid sodium, and NaK78. Liquid sodium offers a significant reduction in temperature gradient as compared of other HTFs for all the aperture sizes of the collector. It is found that the temperature gradient around the circumference of the absorber tube wall at a length of 2 m is reduced to 4, 8, 10, 13, and 18 K, respectively, for the above‐mentioned mass flow rate with liquid sodium as HTF. The analyses are also performed for different HTF inlet temperature in order to study the behavior of the receiver. Based on the HTA, it is desired to have larger aperture parabolic trough collector to generate higher temperature from the solar field and reduce the capital cost. To achieve higher temperature and better performance of the receiver, HTF with good thermophysical properties may be preferable to minimize the heat losses and thermal gradient around the circumference of the absorber tube. 相似文献
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为开发适用于低温热源的高效降膜蒸发换热装置,本研究采用FLUENT软件对低沸点有机工质氟利昂(R113)在竖直管内汽液两相逆流降膜蒸发进行模拟研究。汽液界面捕捉选用VOF模型,并通过udf编程模拟汽液两相蒸发传热,研究了喷淋密度、热流密度及入口温度对R113降膜蒸发换热的影响。结果表明:在一定结构参数下,存在降膜换热最佳喷淋密度;在一定喷淋密度下,热流密度对降膜换热影响显著,且热流密度越高换热效果越好;随着入口温度升高,降膜换热效果削弱,且高于某温度后其对降膜换热几乎没有影响。 相似文献
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在回收燃气锅炉烟气余热时,采用特殊管型强化传热以吸收烟气中大量的水蒸气所携带的显热和潜热,可以降低锅炉的排烟温度,提高锅炉的热效率。对滴型管和圆管烟气侧传热特性进行数值计算,通过对计算结果的分析比较,探讨了影响传热的因素,得出滴型管的传热特性优于圆管的结论,为特殊管型在冷凝换热器中的应用提供参考。 相似文献