有限体积法在电站锅炉炉膛辐射换热计算中的应用

辐射换热是大型锅炉炉膛内的主要换热形式,准确的计算炉膛内的辐射换热量对大型锅炉设计和优化有重要意义。本文将有限体积法推广用于求解和分析大型电站锅炉炉膛内的辐射换热。给出了有限体积法对辐射传递方程进行离散和求解的基本过程。评估了有限体积法求解大型电站锅炉炉膛辐射换热的可靠性。将有限体积法用于分析某电厂600MW锅炉炉膛内的辐射换热,结果表明有限体积法可以有效的求解大型电站锅炉炉膛内的复杂辐射换热过程。     

新式节能型蒸汽气体发生器

热蒸汽驱油是油田开采稠油的一种重要手段。本文介绍的蒸汽发生器改变了传统的锅炉间接换热的方式，采用高温烟气与雾化水直接换热方式实现了低耗高效的蒸汽供给。     

大型锅炉长期动态特性研究中的烟气计算模型

为了简便、准确、快速地解决大空量锅炉汽轮机组长期动态特性研究中的烟气放热计算问题,本文针对现有仿真用烟气放热模型的主要不足,由大容量锅炉热力计算的杜卜斯基－卜劳赫公式推导出新的仿真与动态特性分析用炉膛烟气放热模型;并通过简要的分析、简化和推导,得出了动态过程中各种锅炉换热面烟气出口温度和放热量计算方法,这些烟气计算模型能够较为准确、简单地反映动态过程中高温烟气在大容量锅炉的炉膛和各烟道换热面的烟温及放热量的变化规律,应用十分方便。最后将本文的烟气计算模型应用于某600MW超临界机组的动态特性仿真,仿真结果合理、正确。     

工业锅炉过热器及汽温调节系统设计误区分析

采用锅炉给水的面式减温器过热蒸汽侧并非单相换热而是伴随凝结过程的双相换热.减温器应布置在高于过热器受热面之处且蒸汽应自上而下流动;带烟气调节挡板的过热器设计工况并非锅炉的额定工况而是保持过热蒸汽温度为额定值的锅炉最低工况;不要将低压锅炉过热器紧靠炉膛布置直接承受辐射热.     

生活锅炉中相变热面热特性研究

介绍了生活锅炉中相变换热的传热系数K的数值及影响因素，应用相应的K值计算的相变热面面积与实际需求基本相符，使设计更趋合理与完善。     

关于浮升力增强锅炉系统中湍流换热的研究

在锅炉系统中会遇到流体在一个表面加热,而另一个表面近似绝热的环形通道的湍流混合对流。这一问题中由于有浮升力的存在,使湍流换热被强化,从而使能源的利用率提高了。本文应用Fortran程序对锅炉内浮升力增强换热这一问题进行了数值模拟求解。     

铸铁锅炉烟气流通通道内流动与换热特性的实验研究

介绍了对铸铁锅炉烟气流通通道内烟气流动与换热特性进行的实验研究和得到的烟气阻力和对流换热系数的实验关联式。     

燃油热水锅炉的改进设计与分析

传统的壳管式热水锅炉体积大,结构复杂,热应力集中,产品成本高,安装、售后及现场维修困难。为克服传统热水锅炉的缺点,改进设计燃油热水锅炉的结构为组环式。测试发热量为350kW成品炉的主要热工参数,进行热力分析及动力分析。表明了组环式热水锅炉独特的换热结构可减小其热应力,增强炉内的对流换热程度。炉膛辐射换热空间和辐射换热面较大,换热性能显著。在总换热量恒定时,相比于壳管式热水锅炉,组环式锅炉的体积小,换热面积少,金属耗用量减少,性能价格比增强。     

常温空气无焰燃烧在燃煤锅炉煤改气中的应用

在燃煤锅炉的炉膛内安装常温空气无焰燃烧反应器,可将燃煤锅炉改造为燃气锅炉。计算表明与其它燃气锅炉以对流换热为主的热交换方式不同,该锅炉强化炉内换热,辐射换热量提高。实测结果锅炉热效率达到92.92%,比改造前提高30%以上,比现有同吨位的燃气锅炉高4%以上。由于锅炉实现了无焰燃烧,反应器温度分布均匀,尾气污染物排放远低于国家标准。     

电站锅炉炉膛内火焰刷墙时对流换热系数的计算方法

分析了电站锅炉炉膛内火焰刷墙时的对流换热,提出了火焰刷墙时的对流换热由烟气对流换热和粒子对流换热组成的换热模型。按此模型的计算结果与试验数据符合良好。     

生活锅炉中相变热面传热特性研究

介绍了生活锅炉中相交换热的传热系数Ｋ的数值及影响因素,应用相应的Ｋ值计算的相变热面面积与实际需求基本相符,使设计更趋合理与完善。     

Heat transfer and skin friction of a phase-changing interface of gas-liquid laminar flows

Gas and liquid laminar flows having a phase-changing (evaporation or condensation) interface at their common boundary are investigated numerically under the conditions of constant properties and of flat-surface boundary layers of zero-pressure gradient. The increase of the normal velocity at the interface associated with phase-changing modifies the velocity and temperature profiles so as to reduce the coefficients of skin-friction and heat-transfer at the interface. With an approximation for the velocity profile, these coefficients are analytically presented as functions of the parameter of the phase-change, that is, the normal and parallel velocities and the temperature or the vapor concentration at the interface.     

降低锅炉排烟温度新技术

总结了近年来国内降低锅炉排烟温度的各种新技术，如新型低温省煤器、复合相变换热器、新型自调节重力热管、充气式热管等。对这些新型节能设备的结构特点、性能原理及其应用情况进行了简要介绍。     

相变储热预热式热泵热水器系统性能研究

对集储热、预热与放热于一体的相变储热预热式热泵热水器系统的工作性能进行了研究,并对储、放热过程中相变材料、制冷介质的温度变化及压缩机的功耗情况进行了分析,该储热式热泵热水器系统采用分段加热,利用储能材料对水的预热作用,减小水与系统工作介质之间的换热温差,降低压缩机的功率消耗,使系统COP提高,若储热阶段结合谷电的应用,系统节能效果将更加显著,该试验研究为此类热泵热水器的理论模拟及性能优化奠定了基础.     

Analysis of flat-plate collectors charged with phase-changing fluids

The steady-state performance of flat-plate collectors, charged with phase-changing working fluids, has been studied analytically. The collector is divided into three distinct regions of heat transfer—(i) that in which the fluid is sensibly heated, (ii) that in which boiling occurs and (iii) that in which the vapour is superheated. The results are then combined to express the collector efficiency as a function of the saturation temperature and liquid level.Numerical calculations of the collector efficiencies were carried out for double-glazed flat-plate collectors employing R-11 as the working fluid.     

ZK系列真空相变锅炉的研制开发

文章主要阐述了ZK系列真空相变锅炉,不用真空泵,通过专用控制阀和采取特定操作措施控制冷凝器工质流量的办法,排除锅内不凝结气体、形成并维持锅内真空状态、确保锅炉在任何情况下不超压。该种锅炉具有不爆炸、不结垢、不腐蚀、不发生裂纹、鼓包、爆管等特点,运行安全、可靠、平稳,热效率高。     

A solar water heater based on phase-changing material

A water heater utilising a material which changes phase for storage of solar energy is discussed. The transient analysis is carried out by replacing the solid-liquid block of the phase-changing material by a fictitious solid and assuming that the solid-liquid boundary remains stationary throughout the day. The efficiency of the system and the outlet water temperature during the evening hours increase with the increase in the thermal conductivity of the solid-liquid phases of the materials. Hot water can be obtained throughout the day if water pipes are placed near the surface of the storage material. The outlet water temperature curve becomes flat if the pipes are placed near the bottom of the storage material.     

电站锅炉新型烟气余热回收技术及经济性分析

为解决某300 MW火力发电厂循环流化床锅炉排烟温度偏高的问题,提出将传统低压省煤器与卧式相变换热器相结合的新型烟气余热回收技术.该技术不仅能预防换热设备酸腐蚀,还能实现电厂烟气深度余热回收节能.给出了系统的具体布置方案和设计参数,分析了系统对凝汽器真空以及引风机性能的影响,并应用等效焓降理论及节能定量分析理论进行理论计算.计算结果表明,采用该系统后,锅炉排烟温度降低45℃,降低标准煤耗近3.5 g/（kW·h）.     

Natural cooling systems and an economic feasibility study of long-term storage of coolness

Natural cooling systems are described and classified according to sources of coolness³ storage materials, and modes of fluid flow and heat transfer, as well as the duration of storage. Ambient air, water vapor in the air, and clear sky provide the major sources of coolness, for both short-term (a few hours) and long-term (a few months) storage. Materials suitable for short-term storage of coolness are the building mass, water, rocks and phase-changing salt hydrates. For long-term storage, water (stored in aquifers and in the form of ice and frozen soil), ground, rocks, and phase-changing materials are possible candidates.Seasonal storage of coolness in rocks, ground, water (stored in aquifers), and in the form of ice (produced in a covered underground pond) and frozen soil were considered to meet the cooling demands of three commercial buildings. The characteristics of each system were determined, and an economic analysis was performed for these systems, as well as for a conventional vapor compresssion refrigeration machine. It was found that the cost of land and the interest to be paid on it constituted the major initial and annual costs, respectively. For the aquifer storage, where the land used for the system accessories is very small, and for the covered underground ice pond, where the land above the pond can be used for parking, landscaping, etc., the cost of one GJ of coolness delivered by these systems is lower than that delivered by the conventional unit. Both initial and unit coolness costs of the ground and rock-bed storage systems, even without considering the cost of land, are higher than those of the conventional unit. If the cost of land is excluded, the cost of one GJ of coolness stored in the form of frozen soil is competitive with the unit costs incurred using aquifer and ice pond systems.     

Thermal performance of a non-air-conditioned building with PCCM thermal storage wall

This paper presents a time-dependent periodic heat transfer analysis of a non-air-conditioned building having a south-facing wall of phase-changing component material (PCCM). A rectangular room (6 × 5 × 4 m) based on the ground is considered. The effects of heat transfer through walls and roof, heat conduction to the basement ground and furnishings, heat gain through window and heat loss due to air ventilation have been incorporated in the periodic time-dependent heat transfer analysis. The time-dependent heat flux through the PCCM south-facing wall has been obtained by defining the effective thermal properties of the PCCM for a conduction process with no phase change. Numerical calculations are made for a typical mild winter day (7 March 1979) at New Delhi for heat flux entering through the wall and inside air temperature. Further, a PCCM wall of smaller thickness is more desirable, in comparison to an ordinary masonry concrete wall, for providing efficient thermal energy storage as well as excellent thermal comfort in buildings.