共查询到20条相似文献,搜索用时 15 毫秒
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Mohammad Shakir Nasif Rafat Al-Waked Masud Behnia Graham Morrison 《Journal of Mechanical Science and Technology》2013,27(11):3541-3551
The thermal performance of a Z shape enthalpy heat exchanger utilising 70 gsm Kraft paper as the heat and moisture transfer surface has been investigated. Effects of different inlet air humidity ratio conditions on the heat exchanger effectiveness and on the energy recovered by the heat exchanger have been the main focus of this investigation. A typical air conditioning cooling coil which incorporates an enthalpy heat exchanger has been modelled for tropical climate. Under test conditions, results have shown that latent effectiveness and the moisture resistance coefficient have strong dependency on the inlet air humidity ratio. Moreover, the latent effectiveness has been found to be strongly dependent on the moisture resistance coefficient rather than the convective mass transfer coefficient. Finally, annual energy analysis for Singapore weather conditions have also shown that energy recovered under variable inlet air conditions is 15% less than that recovered under constant inlet air conditions for the same heat exchanger. 相似文献
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Seong-Yeon Yoo Jin-Hyuck Kim Myoung-Seok Jie 《Journal of Mechanical Science and Technology》2010,24(4):887-892
When circulated air passes through the cooling coil in an air-conditioning system, the air is over-cooled to eliminate the
moisture and decrease the temperature. The cooled air is then reheated to recover the temperature. The purpose of the present
study was to evaluate the performance of a cooling/reheating system with regard to both cooling and reheating energy savings
affected by exchanging heat between the cooled air and the reheated air with a compact heat exchanger. The thermal and dehumidification
behaviors of the system were evaluated experimentally and then compared with simulation data. The results show that the energy
saving rate was as high as 50% under the present experimental conditions and was affected by the face velocity of the heat
exchanger, the inlet temperature, the inlet humidity ratio, and the effectiveness of heat exchanger. Furthermore, the experimental
data were found to be in fairly good agreement with the simulation data. 相似文献
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Yong Sun Cho Seon Chang Kim Young Lyoul Kim Yong Tae Kang 《Journal of Mechanical Science and Technology》2013,27(6):1875-1880
Liquid desiccant systems have been paid attention because of its advantages in energy saving and an environmental friendliness. The use of liquid desiccant systems offers design and performance advantages over the solid desiccant systems, especially when solar energy is used for regeneration. The objective of this paper is to analyze the simultaneous heat and mass transfer characteristics of lithium chloride aqueous solution for the plate type dehumidification system. The effects of process air and solution inlet conditions on the dehumidification performance are studied in this study. It is found that the heat transfer coefficient of the air side gives much more significant effect on the absorption rate and dehumidification effectiveness than those of the solution and the coolant sides while the mass transfer coefficient of the solution side gives more significant effect than that of the air side. It is also found that the solution concentration is the most important factor for absorption performance improvement during the dehumidification process. 相似文献
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To overcome the fouling problem that is common in heat exchangers for waste heat recovery, a new type of fluidized heat exchanger
was devised and tested. Fluidized bed heat exchangers are considered to be a good candidate for waste heat recovery flue gases
due to their demonstrated ability to avoid fouling or to clean out deposition on heat transfer surfaces, but have a major
drawback with significant pressure losses. These pressure drops typically associated with the distributor plate, which is
a key component in constructing any conventional fluidized bed system, limit the applicability of fluidized bed heat exchangers
for use as an energy saving device. In a new design, however, dilute gassolid particulate is maintained without having a distributor
plate. The main feature of this no-distributor-fluidized (NDF) heat exchanger is the self-cleaning action by ingested circulating
particles at minimal additional pressure loss. In the present study, a multi riser NDF heat exchanger of 7,000 kcal/hr capacity
was built to evaluate its heat transfer performance and fouling reduction characteristics. To experimentally simulate the
fouled condition, fuel rich combustion gas with soot was introduced to the heat exchanger, then a cleaning test was performed
by introducing glass bead particles (600μm) inside the gas passage of the heat exchanger unit. Through the present experimental
study, the performance degradation due to fouling was successfully demonstrated and the cleaning role of particle circulation
was identified. It was also demonstrated that small amounts of circulating particles contribute not only to the fouling reduction
on the gas side, but also to the heat transfer enhancement. Experimental operation data for 50 hours including accelerated
fouling are obtained to simulate the long-term behavior of the system. 相似文献
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介绍了一种复合式热管换热器,在高温段采用螺旋槽翅片管换热器,在低温段采用热管换热器进行2级逆流换热,成功地应用于燃气钢瓶调质炉的余热回收利用领域,并讨论了强化传热措施和工业炉燃料的节约率等相关内容。用燃料废气热量来预热空气是燃烧炉最有效的节能措施,例如废气温度为700℃,废气带走的热损失率为40%,若把空气预热到300℃就可以节约燃料达到15%。 相似文献
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采用有限元法,应用ANSYS软件的热分析功能对翅片热板散热器的传热性能进行了数值模拟,并计算出该散热器表面的瞬态温度变化曲线,与实验测试结果吻合得较好.最后的研究结果表明:所研制的新型功率电子元器件翅片热板散热器散热性能良好,具有良好的启动性能和等温性能. 相似文献
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为了保证汽车空调热交换器生产过程中的产品质量,针对汽车空调热交换器生产过程中质量检测方面存在着的问题,以汽车空调热交换器质量指标-散热性能为研究对象,提出了面向生产过程质量控制的汽车空调热交换器散热性能检测装置的设计原理,完成了热交换器散热性能检测装置的硬件和软件的设计与实现;最后对该检测装置进行了实验验证。实验及研究结果表明,所设计完成的检测装置能够用于判定热交换器生产过程是否发生异常情况,从而可以为汽车空调热交换器生产过程质量保证系统的构建奠定一定的基础。 相似文献
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同轴套管式深井换热器是一种开采地热能的有效方式,为了提高其换热器的换热性能,采用有限体积分析方法,开展了同轴套管式深井换热器传热性能研究。通过建立近地热源区域的同轴套管式深井换热器三维传热模型,分析了入口流速、入口温度以及保温管距井底距离等关键因素对换热器采热功率的影响,结果表明:入口流速由0.1 m/s增加到1 m/s,采出温度降低了9.82 K,采热功率增加了7倍;入口温度从288 K增加到308 K,采出温度增加了13.61 K,采热功率下降了17.2%;距井底900 mm距离降低到 100 mm,采出温度增加1.91 K,采热功率增加了6.57%。 相似文献
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An experimental study of the effects of various factors (fin pitch, fin arrangement, air temperature, air humidity, and air velocity) on the frost growth and thermal performance of a fin-tube heat exchanger has been conducted under the frosting condition. It is found that the thermal performance of a heat exchanger is closely related to the blockage ratio of the air flow passages due to the frost growth. The maximum allowable blockage ratio is used to determine the criteria for the optimal operating conditions of a fin-tube heat exchanger. It is also shown that heat transfer rate of heat exchanger with staggered fin arrangement increases about 17% and the time required for heat transfer rate to reach a maximum value becomes longer, compared with those of an inline fin-tube heat exchanger under the frosting condition. The energy transfer resistance between the air and coolant decreases with the increase of inlet air temperature and velocity and with decreasing inlet air humidity. 相似文献
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介绍了在乳胶手套烘烤过程中对废热和冷凝液进行的回收利用,这样不但节省了能源,还可以净化环境。采用热管换热器是行之有效的方法,它把回收的热量用于加热导热油炉助燃空气或者作为烘烤的热源,对回收的冷凝液进行重复利用,实践证明,该方法可节能28%,并且具有投资小、无风险的特点。 相似文献
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Ho-Seong Lee Jong-Phil Won Choong-Won Cho Yong-Chan Kim Moo-Yeon Lee 《Journal of Mechanical Science and Technology》2012,26(7):2065-2071
The objective of this study is to investigate the performance characteristics of a stack coolant source heat pump using R744 with a stack coolant heat source for fuel cell electric vehicles under cold weather conditions. Electric heaters are currently used in fuel cell electric vehicles, and the high levels of energy consumption involved lead to lower fuel efficiency and a reduction in the vehicle??s driving range. In order to improve the efficiency of the fuel cell electric vehicles in this study, a heat pump using R744 as a refrigerant and making use of wasted heat from the stacks is developed to cover the heating capacity. This heat pump is tested and performance optimized for stack coolant heat recovery under the compressor speeds, air temperatures, and flow rates of the interior heat exchanger, as well as the coolant flow rates of the CO2-coolant heat exchanger. In addition, the heating capacity of the tested system was sufficiently attained over 5.0 kW at the coolant flow rate of 5.0 l/min under extremely cold weather conditions of ?20°C. 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
18.
The operation performance measurement of the air source heat pumps in the field, in which conditions are complicated and the accuracy could not be ensured, is very crucial for its performance evaluation and improvement. In this investigation, a novel method for measuring the heating capacity of the air source heat pump is established. An auxiliary electric heater is installed along the pipeline between the compressor and the condenser, and the refrigerant temperature difference caused by the heater is gathered to calculate the refrigerant mass flow rate based on the energy conservation. The heating capacity is calculated with the measured data of the refrigerant enthalpy at the inlet and outlet of the condenser and the refrigerant mass flow rate of the compressor discharge pipe. The validation results in laboratory tests show that the measured heating capacity accuracy is within 9.2%. It is also found that the impact of the novel test method on the heating capacity of the air source heat pumps is below 1.7%, and the power consumption of the tested units is increasing of within 1.8% compared with it when the electric heater is off. The refrigerant enthalpy difference method with an electric heater presented in this research can be applied to measure the heating capacity of different air source heat pump air heaters accurately in the field, which will be much helpful to improve the performance for cleaning heating in northern China. 相似文献
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An experimental study was performed to reduce the condensation under very humid conditions for a total heat exchanger. The hydrochromic ink was used to detect the condensation within the total heat exchanger. Condensation in a total heat exchanger can be reduced by decreasing the flow rate of the supply air. The other method of decreasing the flow rate of the exhaust air can also be used to reduce condensation. However the flow rate of the exhaust air has to be less than half of the supply air flow rate for the tested total heat exchanger. 相似文献