热电联产燃气余热锅炉的热效率分析

在环保和节能日益受到重视的背景下,研究影响燃气余热锅炉热效率的工况点和环保具有重要意义.以2台热电联产燃气余热锅炉为研究对象,在10种不同的工况下,研究锅炉热效率和烟气排放状况,分析运行工况、热效率和烟气排放之间的关系,为提高燃气余热锅炉热效率和降低尾部烟气排放提供指导.     

低位烟气余热深度回收利用状况述评(Ⅱ)——传热过程与技术应用研究

以热力学为指导,通过利用高效的传热技术与吸收式热泵技术的耦合,对低位烟气余热“质”和“量”分控回收,可实现低位烟气余热的深度回收与梯级利用.应用于高水蒸气含量的燃油、燃气设备的烟气余热回收,不仅回收显热,还深度回收其潜热,综合效益最佳.高效的传热技术可减小余热与利用介质间的传热温差而减少传热过程的不可逆损失是最为核心的技术问题,对其进行分析探讨,有利于高效、节能、环保的低位烟气余热深度回收与利用技术的发展.     

火力发电厂锅炉烟气中SO3浓度对低温换热器积灰特性的影响

<正>在国家节能环保政策推动下,锅炉尾部低品位烟气余热回收利用技术得到了高度的研究和大力的推广运用。然而,低温烟气余热回收技术中受热面积灰,会严重影响换热器的换热效率,同时增加换热器烟气阻力,较严重积灰甚至会导致换热器设备无法正常运行工作。影响低温换热器积灰的因素有很多,本文将重点对烟气中SO_3浓度对换热器积灰特性的影响进行论述和研究。     

燃气锅炉排烟冷凝热回收技术

通过对天然气烟气特性的分析以及对冷凝式锅炉热效率的分析和计算得出,将烟气温度降低到露点温度以下对烟气进行余热回收有重要的实际意义;冷凝式换热器就是增设在天然气锅炉尾部的余热回收装置,可以将排烟中大量的能量加以回收利用,从而达到节能环保的效果.对几种不同结构型式的冷凝换热器的传热效果、烟气阻力以及腐蚀性等问题进行了定性对比,对各种排烟余热回收技术进行了综合探讨.     

加热炉空气预热器最佳设计

一、前言 加热炉是将燃料的化学能转化成热能的主要设备。由于其排烟温度一般较高,使得热损失偏大,直接影响加热炉的热效率。为了节约燃料消耗,提高加热炉的热效率,大多数厂家对烟气余热进行了回收。随着能源的紧张,烟气余热回收已显得日趋重要。 加热炉的余热最普遍的回收方式是利用烟气余热预热助燃空气。如图1所示的空气     

加热炉烟气余热自回收的节能计算

加热炉烟气余热自回收的节能计算江西新余钢铁总厂罗晓青，杨三根加热炉炉膛排出的烟气温度比较高，烟气余热的利用，通常是先回收用于自身（如预热空气，国标ＧＢ３４８６（评价企业合理用热技术导则》中规定有工业炉烟气余热回收率的要求），然后进一步进行用于炉外回收...     

提高注汽锅炉运行热效率研究

根据油田注汽锅炉热平衡测算数据及结果分析,找出了其运行热效率低的原因。影响注汽锅炉运行热效率的主要因素是排烟温度和空气系数,测算分析表明,大部分注汽锅炉二者均超标。根据注汽锅炉特点提出了提高运行热效率的技术措施,即空气系数调节技术、化学清烟垢技术和烟气余热回收技术。工程应用表明,节能及经济效益显著。     

天燃气导热油锅炉节能改造技术分析

通过在燃气锅炉尾部安装热交换器回收烟气余热来预热空气,以有效减少烟气带走的余热,提高天然气导热油锅炉的热效率。结果表明:(1)与传统天燃气导热油锅炉对比,新型燃气锅炉的排烟温度由350℃降低到150℃,提高锅炉热效率10%以上;(2)对1台2 t/h天然气锅炉进行节能改造年节约运行费用30万元,投资回收期仅8个月,经济效益显著。     

基于浸没式燃烧技术的节能高效燃气热水锅炉

通过对锅炉热效率、烟气余热回收及浸没式燃烧技术的基本原理进行分析,结合该技术特点及相关技术经验,设计出一种节能高效热水锅炉,并从技术经济等方面讨论该新型燃气热水锅炉的可行性和适用性。     

炊用燃气大锅灶余热能源分析及综合利用评价方法的探讨

炊用燃气大锅灶是商用厨房重要的燃气消耗设备,节能减排是设计、使用的关注指标。随着新技术进步以及强制性标准的实施,新型式结构的大锅灶不断推出,烟气余热的回收利用技术广泛运用,评价其能源综合利用效率,探求科学合理的试验与评价综合利用热效率方法提上议程。结合炊用燃气大锅灶余热能源分析及综合利用评价方法的探讨,提出大锅灶综合热效率的试验和计算方法,鼓励更多的技术创新与应用,为社会提供更优质的产品。     

一种带回热的新型节能燃气灶的研究

提出一种带回热的新型节能燃气灶,即采用回热循环来提高燃气灶的热效率.利用燃烧后排走的高温烟气加热助燃空气.一方面提高了助燃空气的温度使燃烧效率得到提高;另一方面回收了烟气的热量提高了总的热效率,并且改变了传统的上抽油烟方式为下抽油烟,使厨房环境得到明显改善.理论计算表明在考虑上部进风20%的情况下热回收率为6.07%,相对热回收率为20.25%,热效率可提高4.25%.本文给出了燃气灶热力计算的基本流程,希望会对节能燃气灶的设计提供参考.     

钢铁厂焦化及烧结工序热量利用效率及余热资源评价

针对钢铁生产流程中焦化及烧结工序的能量平衡、热效率及火用效率等展开研究,并对各种余热资源的能级等进行了计算和评价。在焦炉产生的余热资源中,红焦的焓值和火用值均高于其他两项,说明红焦余热量大,并且余热品质好。焦炉煤气的比焓值和比火用值均大于焦炉烟气,说明焦炉煤气的能量品质要好于焦炉烟气,而焦炉烟气的焓值大于焦炉煤气。烧结矿的比焓值和比火用值均比烧结烟气和环冷废气的比焓值和比火用值高,说明烧结矿的余热资源量和余热品质均高于烧结烟气和环冷废气。这项研究为焦化工序及烧结工序余热利用等奠定了基础。     

光管翅片管热管式佘热锅炉在Consteel电炉的应用

介绍了Consteel电炉余热回收特点,并根据不同的温度和含尘研制了光管一翅片管一热管式余热锅炉,设计中充分考虑了结构合理、热稳定性好、检修维护方便,并给出现场测试数据与理论计算结果的对比,在Consteel电炉余热回收中使用光管一翅片管一热管式余热锅炉,既回收了烟气显热又减少环境污染,有着良好的推广前景。     

The oven receiver: An approach toward the revival of concentrating solar cookers

Concentrating type solar cookers are expected to demonstrate high performance because of the large collection area employed. However, the net amount of heat used is still low. This is greatly attributed to the large amount of heat losses from the bare food pots used. Introducing the oven type concept as an alternative approach for collecting the concentrated solar energy would drastically boost the overall cooker efficiency. In this work, the transient heat balance equations were developed for predicting the thermal behavior of an oven type concentrating solar cooker. This simulation was used to show theoretically the great advantage of using a glass-sided oven over the conventional bare receiver pot. The resulting mathematical model was solved using numerical integration. The transient nature of solar radiation and effects of wind speed variation were all taken into consideration. The analysis showed that the oven type receiving pot has both a higher fluid temperature and overall receiver efficiency compared to the bare receiver type, working under similar conditions.     

Heat release rate and thermal fume behavior estimation of fuel cell vehicles in tunnel fires

This study proposes a heat release rate (HRR) estimation method for a carrier loaded with fuel cell vehicles (FCVs) trapped in a tunnel fire. The carrier is divided into several parts, and the HRR is estimated by adding the HRRs of all system parts (carrier and FCVs). The HRR of one FCV was compared with that of a gasoline vehicle. The thermal fume behavior in longitudinally inclined tunnel fires was also investigated. Even a modest inclination hastened the thermal fume propagation of the FCV fires. Of relevance to the prevention of tunnel fire disasters, the thermal fume behavior differed between FCV and gasoline fires. For safety assessment of tunnel fires, the thermal fume behaviors of an FCV fire and gasoline vehicle fire in a tunnel were investigated by the proposed method. In the case of no longitudinal inclination, the thermal fume of the FCV fire arrived earlier than that of the gasoline vehicle fire (by 1 min at x = 200 m and over 4 min at x = 250 m) because of the emitted hydrogen gas. At 2% longitudinal inclination, the thermal fume of the FCV fire propagated to the downstream side 4 min before that of the gasoline vehicle fire. At 4% longitudinal inclination, the thermal fume propagated 50 m downstream of the initial fire after 10 min. Therefore, after the hydrogen emission, the thermal fume of the FCV fire traveled faster than that of the gasoline vehicle fire. The proposed HRR estimation method can contribute to the risk analysis of various types of tunnel fires.     

冷轧板退火炉余热回收研究与实践

通过对某镀锌厂生产线的供用能设备进行全面的热平衡测试及分析，提出对退火炉烟气余热回收利用，以代替现有供热锅炉方案。本方案已实施并达到预期效果。     

A numerical study on the effect of a heated hollow cylinder on mixed convection in a ventilated cavity

The present work is aimed to study mixed convection heat transfer characteristics within a ventilated square cavity having a heated hollow cylinder. The heated hollow cylinder is placed at the center of the cavity. In addition, the wall of the cavity is assumed to be adiabatic. Flows are imposed through the inlet at the bottom of the left wall and exited at the top of the right wall of the cavity. The present study simulates a practical system such as air-cooled electronic equipment with a heat component or an oven with heater. Emphasis is sited on the influences of the cylinder diameter and the thermal conductivity of the cylinder in the cavity. The consequent mathematical model is governed by the coupled equations of mass, momentum and energy and solved by employing Galerkin weighted residual method of finite element formulation. A wide range of pertinent parameters such as Reynolds number, Richardson number, cylinder diameter and the solid-fluid thermal conductivity ratio are considered in the present study. Various results such as the streamlines, isotherms, heat transfer rates in terms of the average Nusselt number and average fluid temperature in the cavity are presented for different aforesaid parameters. It is observed that the cylinder diameter has significant effect on both the flow and thermal fields but the solid-fluid thermal conductivity ratio has significant effect only on the thermal field.     

A modular phase change heat exchanger for a solar oven

A modular energy storing heat exchanger designed to use pentaerythritol for thermal storage (solid-solid phase change at 182°C) is tested in an oven by circulating heat transfer oil which is electrically heated in a manner to simulate a concentrating solar collector. Three efficiencies for heating the system under controlled and measured power input are determined—the heat exchanger efficiency, the efficiency of the heater with distribution lines, and the total system efficiency. Thermal energy retention times and cooking extraction times are determined, and along with the efficiencies, are compared with the results previously reported for a nonmodular heat exchanger. The modular configuration provides a highly improved extraction rate for cooking due to its wrap-around character and its increased surface-to-volume ratio. A full scale glass model of the copper tubing of the system is described and flow observations reported demonstrating how uniformly the parallel pumping branches perform and how trapped air pockets affect pumping power. A technique for measuring pumping power is described and its application to our system is quantified to show that less than 1 watt is required to circulate the heat transfer oil even when the system includes the solar collector and its longer connecting tubes.     

A simple approach to solve conjugated heat transfer problems in circular and parallel plate ducts

A simple perturbation technique is used to reformulate the energy equations which describe the transient thermal behaviour of a radially lumped conjugated heat transfer problem in circular and parallel plate ducts of finite wall thickness. The simple perturbation technique is used to eliminate the coupling between the fluid and the solid-wall energy equations when the temperature difference between the fluid and the solid wall is a small perturbed quantity, which is true when the interface convective heat transfer coefficient between the fluid and the solid wall is high. A mathematical criterion is derived to determine the conditions under which fluid and solid wall are in thermal equilibrium. It is found that there are four dimensionless parameters that control the state of thermal equilibrium between the fluid and the solid domains. © 1998 by John Wiley & Sons, Ltd.     

Thermal characteristics of a eutectic mixture of myristic and palmitic acids as phase change material for heating applications

The melting temperatures of the palmitic acid (PA) (61.2 °C) and the myristic acid (MA) (52.2 °C) are high for solar thermal energy storage under the climate conditions of the some regions in Turkey. However, their melting temperatures can be adjusted to a suitable value by addition of MA to PA. In this study, the thermal analysis by differential scanning calorimetry technique shows that the mixture of MA and PA with 58.0 wt% MA forms a eutectic mixture with melting temperature of 42.6 °C and the latent heat of fusion of 169.7 J g⁻¹. The melting temperature and latent heat of fusion of MA–PA eutectic mixture make it a suitable material for energy storage in passive solar space and greenhouse heating systems under the climate conditions of some residential and agricultural regions in Turkey. The present study also deals with the experimental establishment of thermal characteristics of the eutectic mixture as a phase change material in a vertical concentric two pipes––energy storage system. Reynolds and Stefan numbers were selected as experimental parameters and used for the evaluation of the results. The experimental results prove that the MA–PA eutectic mixture has attractive thermal characteristics during the melting and the solidification processes and it is a potential latent heat storage material for heating applications with respect to the climate requirements in Turkey.