共查询到20条相似文献,搜索用时 15 毫秒
1.
The excessively increasing environmental concerns along with reducing fossil fuel resources introduce the trend of increasing the efficiency of boiler via implementing waste heat recovery. In the present study, the potential of latent heat recovery is investigated in the middle‐size boiler exhaust flue gas using the shell and corrugated tube heat exchanger. The main purpose of the present study is efficiency growth in flue gases using latent heat recovery of the steam energy. The heat recovery analysis is evaluated by a validated computational fluid dynamics model by a commercial software. For this study, the effect of different tube arrangements, number of tubes, and flow direction in the shell on heat transfer and pressure drop were investigated. The results showed that in‐line arrangement of the tubes in the shell presents better thermal performance and also high pressure drop among the other arrangements. As a result, by considering the thermal performance and pressure drop, radial arrangement shows higher performance. According to the obtained results from Section 2 of the present study, by considering the radial arrangement of tubes in the shell, as the number of tube rises, the thermal performance declines. 相似文献
2.
An experimental system investigating condensation heat transfer of wet flue gas was set up, and the heat transfer performance of vapor‐gas mixture with vapor condensation was discussed. The experimental results of laminar flow in a plastic longitudinal spiral plate heat exchanger were obtained and are in good agreement with the modified classical film model. It is shown that the plastic air preheater can avoid acid corrosion in the low‐temperature field for the boiler using fuel containing sulfur and recover latent heat of the water vapor of the wet flue gas. Also some SO2 was scrubbed during the vapor condensing process in the heat exchanger. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 571–580, 2001 相似文献
3.
4.
5.
An experimental study on the heat recovery from the exhaust air of stenters with a packed bed column
Stenters are the dryers that are commonly used in textile finishing mills. The exhaust air of the stenters is of great potential of energy saving via heat recovery mainly using the latent heat of condensation of the water vapour involved. This study reveals the usage possibility of a packed bed column for the heat recovery from the exhaust air of the stenter. An experimental investigation was carried out with a laboratory‐scale counter flow packed bed column. Additionally, an exergetic evaluation of the system was performed. Water inlet temperature and relative humidity ratio of the exhaust air are the main factors that affect the water outlet temperatures and efficiency of the system. It was observed that a decrease in the water inlet temperature increases the recovered exergy; however, water outlet temperature is not significantly affected by the inlet temperature of the water. The exergy efficiency of the system increases with the increase in the relative humidity ratio of the exhaust air. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
6.
Masahiro Osakabe Kazuhiko Ishida Kiyoyuki Yagi Tugue Itoh Kunimitu Ohmasa 《亚洲传热研究》2001,30(2):139-151
In order to improve boiler efficiency, latent heat recovery from flue gas is a very important concept. Condensation heat transfer on horizontal stainless‐steel tubes was investigated experimentally by using an actual flue gas from a natural gas boiler. The experiment was conducted at different air ratios of the flue gas and a wide range of tube wall temperatures. The condensation pattern was similar to a dropwise condensation near the dew point. By decreasing the wall temperature, the wall region covered with a thin liquid film increased. The heat and mass transfer behavior was well predicted with the analogy correlation at the high‐wall‐temperature region. At the low‐wall‐temperature region, the total heat transfer was higher than that predicted by the analogy correlation. © 2001 Scripta Technica, Heat Trans Asian Res, 30(2): 139–151, 2001 相似文献
7.
8.
9.
烟气余热回收是提高燃煤电站运行效率的有效手段。本文建立了某600 MW机组烟气余热回收系统的变工况计算模型,获得了环境温度、设计参数和运行参数对系统变工况运行特性的影响规律,提出了运行参数优化与构型在线调整相结合的优化策略:在环境温度较高时采用系统构型自适应策略,在环境温度较低时采用系统构型自适应结合参数调控策略。研究结果表明:优化后,系统在运行范围内的平均节煤率达到了2.72 g/(kW·h),相比原系统平均节煤率仅降低了0.3 g/(kW·h),安全运行的环境温度下限由24℃扩展至-10℃。 相似文献
10.
降低燃气锅炉排烟热损失方法探讨 总被引:4,自引:0,他引:4
燃用天然气的锅炉其排烟温度较高,除带走大量显热之外,烟气中还存在大量水蒸汽的潜热,若将这两部分热量充分回收,则将大幅度提高锅炉热效率。文章在对天然气的燃烧特性计算的基础上,分析燃气锅炉烟气潜热回收的效果和需要解决的问题。 相似文献
11.
To improve the practicability of the waste heat recovery system for internal combustion engines, the compact potential of exhaust heat exchangers using metal foams is investigated. In the present study, the performance of compact exhaust heat exchangers is compared with that of a conventional shell and tube heat exchanger in a real test bench. Both heat transfer and pressure drop performance are considered when assessing the performance of heat exchangers because these two factors normally show a trade‐off relationship when designing exhaust heat exchangers. Compared with the conventional heat exchanger, the compact heat exchanger can achieve a similar pressure drop, and at the same time the heat transfer is increased by 30%, whereas the volume and the weight are each reduced by 2/3. The performance of compact heat exchangers with six types of Ni metal foams is also investigated under different mass flow rates and thicknesses of the porous layer. Results show that the optimum compact heat exchanger enhances the comprehensive performance 1.9 times compared with original one. This study shows that metal foams have great potential in realizing a compact exhaust heat exchanger for engine waste heat recovery. 相似文献
12.
燃气锅炉排放的烟气中含有大量的水蒸气,因排烟温度未能降到露点以下而无法有效回收水蒸气的冷凝潜热。本文采用压缩式热泵与低温空预器相结合的方式深度回收燃气锅炉烟气余热,主要研究了在不同过量空气系数下供热回水流量和供热回水温度对排烟温度、余热回收效率、热泵机组制热性能系数及水蒸气冷凝率的影响。研究结果表明:在过量空气系数为1、供热回水流量为80 t/h条件下,热泵可将供热回水温度从50.0 ℃提升至65.1 ℃,其制热性能系数为4.25;空气进、出低温空预器的温度分别为-3.8 ℃和33.0 ℃,流量为15 360 m3/h时,排烟温度从90 ℃降至20 ℃,烟气余热回收效率达到14.8%;以29 MW的燃气锅炉为研究对象,按供热面积为5.2×105m2,供暖151天计算,烟气中回收的冷凝水量为8 000 t,占锅炉补水量的54.1%;该余热回收系统的投资回收期为2.1年,压缩式热泵烟气余热回收系统节能效果显著。 相似文献
13.
14.
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
15.
This paper is based on the proposal of a new waste heat recovery (WHR) system, which can be utilized to heat the boiler return water, boiler supply air, and building heating air. The system is the combination of an indirect contact condensing unit (IDCCU), a mechanical compression heat pump, and two air preheaters. The system is modeled on the basis of mass and energy balance and then thermodynamically analyzed. Improved performance results were obtained in the form of an increase in the boiler's energy efficiency of about 10.47%, with 4.87% increase in exergy efficiency. The coefficient of performance (COP) of the heat pump was increased from 1.23 to 1.45 by the addition of an air heater in the conventional heat pump. The exergy destruction in each component is calculated. Sensitivity analysis was performed to check the influence of different operating parameters on the performance of the WHR system and boiler. It can be observed from the results that for a specific refrigerant temperature and a calculated amount of mass, flow rate can maximize the condensation efficiency of IDCCU by decreasing the flue gas temperature, while the use of the air heater can further reduce the flue gas temperature, and a stream of hot air can be utilized for space heating. A comparison is made with the other system on a performance basis. The results shows a clear difference in efficiencies and profit earned. 相似文献
16.
17.
锅炉是一种特殊结构部件,既可以为热电效应为基础的温差发电器提供热源,也可以为其提供冷源,这为应用温差发电器创造了条件。应用温差发电器可以降低排烟温度,减少排烟热损失。文章对应用温差发电器的可能性以及应用后的效率进行了分析,结论是可以提高锅炉效率;提出了如何应用温差发电器件的方法.并对锅炉应用温差发电器降低排烟损失应该考虑的问题进行了分析。 相似文献
18.
The exhaust gas from an internal combustion engine carries away about 30% of the heat of combustion. The energy available in the exit stream of many energy conversion devices goes as waste, if not utilized properly. The major technical constraint that prevents successful implementation of waste heat recovery is due to its intermittent and time mismatched demand and availability of energy. In the present work, a shell and finned tube heat exchanger integrated with an IC engine setup to extract heat from the exhaust gas and a thermal energy storage tank used to store the excess energy available is investigated in detail. A combined sensible and latent heat storage system is designed, fabricated and tested for thermal energy storage using cylindrical phase change material (PCM) capsules. The performance of the engine with and without heat exchanger is evaluated. It is found that nearly 10–15% of fuel power is stored as heat in the combined storage system, which is available at reasonably higher temperature for suitable application. The performance parameters pertaining to the heat exchanger and the storage tank such as amount of heat recovered, heat lost, charging rate, charging efficiency and percentage energy saved are evaluated and reported in this paper. 相似文献
19.
20.
Xiaojun Shi Defu Che Brian Agnew Jianmin Gao 《International Journal of Heat and Mass Transfer》2011,54(1-3):606-615
An experimental and theoretical investigation of the utilization of finned tube compact heat exchanger for a heat recovery steam generator (HRSG) to recover both sensible and latent heat is presented in this paper. The heat transfer and pressure drop characteristics of the fin-and-tube heat exchanger are theoretically studied. A correlation of the combined convection–condensation heat transfer is derived by using the heat and mass transfer analogy models. The experimental results have shown that the Colburn factor (j) and the friction factor (f) for humid air, simulating the exhaust of HRSG, are larger than those for dry air. It has been also found that the f factor difference between humid air and dry air decreases as the air side Reynolds number increases and both the f factor and the j factor for humid air increase with the increase of water vapour concentration. A scheme for the design of compact heat exchanger for HRSGs is presented. 相似文献