共查询到17条相似文献,搜索用时 78 毫秒
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连续螺旋折流板换热器动态特性研究 总被引:1,自引:1,他引:0
建立了可进行壳管式换热器动态特性试验研究系统,通过试验研究的方法对水-油为换热工质的连续螺旋折流板换热器动态特性进行了试验研究,进口流量扰动为等百分比流量特性,研究了四种流量扰动方式下水和油出口温度的动态响应。同时研究了在一定R e下,不同的流体扰动量对换热器进出口温升的影响,得到了换热器进出口温升与流体扰动量之间的关联式。实验表明,较于气体而言,液-液换热系统温度的动态响应时间比较长,研究发现在正负的流量扰动下,螺旋折流板换热器进出口温度变化呈现线性变化,进出口温升在正负流量扰动下其变化曲线具有对称特征。 相似文献
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对倾斜角20°有34根管子的周向重叠三分螺旋折流板换热器进行了数值模拟研究,通过在三分螺旋折流板换热器壳侧通道内偏心纵向切面和横切面以及六边形纵向切面上速度矢量流场和压力云图的叠加展示,不仅呈现了壳侧总体螺旋速度的周向分量的轨迹,而且从所呈现的轴向和径向速度分量揭示了二次流和相邻折流板V型缺口处逆向泄漏的踪迹.研究结果表明:流体在螺旋通道内在离心力作用下呈现向外扩张的流动趋势,然后在外围高、中心低的压力分布作用下沿着靠近折流板附近的流速较低的区域向心流动返回轴中心,形成单涡型迪恩二次流;二次流增强了流体的掺混,从而有利于强化传热. 相似文献
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建立了可进行壳管式换热器动态特性试验研究系统,通过试验研究的方法对水-油为换热工质的连续螺旋折流板管壳式换热器动态特性进行了试验研究,进口流量扰动为等百分比流量特性,研究了4种流量扰动方式下水和油出口温度的动态响应。同时研究了在一定Re数下,不同的流体扰动量对换热器进出口温升的影响,得到了换热器进出口温升与流体扰动量之间的关联式。实验表明,液液换热系统温度的动态响应时间比较长,研究发现在正负的流量扰动下,换热器进出口温度变化呈现线性变化,进出口温升在正负流量扰动下其变化曲线具有对称特征。分别建立了有限差分数值预测模型及人工神经网络模型对换热器油侧的出口温度进行了动态预测,预测结果与试验值符合良好,人工神经网络的预测结果要好于数值模拟预测,其偏差绝对值在1.3%以内,表明人工神经网络在进行复杂的系统辨识时具有一定的参考及应用价值。 相似文献
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In the present work, the shell and tube heat exchanger (STHX) is designed based on The Tubular Exchanger Manufacturers Association standards with hot fluid (water) flowing on the shell side and cold fluid on the tube side. A comparison is made between the Nusselt number and friction factor obtained from numerical and experimental results of segmental baffles (SBs) and helical baffles (HB) with different baffle inclinations. The results show that SB provided a higher Colburn factor (js) when compared with HBs STHXs (20°, 30°, 40°, and 50°), but shell side pressure drop is lower for 40° HBs STHXs for the same shell side fluid flow rates. 相似文献
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The aim of this study is to utilize waste thermal energy from industries into useful heat for water and air heating. In this paper, the thermal modeling and performance of three fluid heat exchangers (TFHE) have been experimentally investigated. The TFHE considered here is an enhanced version of the double-pipe heat exchanger. A novel TFHE having fin (1 mm thin copper wire of 10 mm pitch) acts as a roughness element, which is wrapped on the helical coil's outer surface for increasing heat transfer (HT) rate and the turbulence effect for normal water, and this outer surface finned helical coil is inserted between two concentric straight tubes. The innermost tube carries atmospheric air, the finned helical coil tube carries waste hot fluid while normal water flows in the inner annulus of the outermost tube. The coiled-side Reynolds number is varied in the range of 7000–30,000, while the curvature ratio of 0.1315, pitch-to-inside diameter ratio of 2.88 and wire-to-tube diameter of the helical tube is kept constant. A counterflow arrangement has been made for experimentation. Nusselt number is calculated using the traditional Wilson plot method that is compared and validated with results available in the literature. The overall HT coefficient is found to increase by increasing the volume flow rate of fluids, while effectiveness decreases or increases depending on residence time and capacity ratio. The percentage increment in the Nusselt number, maximum friction factor, overall HT coefficient between waste hot fluid to normal water, effectiveness is found to be 21.10%–23.88%, 90.91%, 3.40%–29.45%, 3.40%–25.33%, respectively, for the coil side. TFHE is thus proposed for heating water and space simultaneously. 相似文献
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Yonghua You Aiwu Fan Suyi Huang Wei Liu 《International Journal of Heat and Mass Transfer》2012,55(25-26):7561-7569
CFD simulation has become a powerful and popular tool for the thermal hydraulic design and analysis of heat exchangers. However, the computation load is usually too heavy to simulate a whole shell-and-tube heat exchanger (STHX) applying the traditional modeling method. In the present study, a numerical model based on the concepts of porosity and permeability is developed to obtain the shell-side thermal hydraulic performances. In this model, the distributed resistances and heat sources, as well as the distributed turbulence kinetic energy and its dissipation rate are introduced to account for the impacts of tubes on the fluid. The numerical model is solved over Re = 6813–22,326 for the shell side of a STHX with flower baffles, and reasonable accuracy is demonstrated by the comparison with test data (maximum relative deviation within 15%). With this model, the velocity and temperature fields, together with the distribution of convective heat transfer coefficient, are obtained and presented to help analyzing the underlying mechanism of shell-side thermal augmentation. The present work shows that this model is economic and effective in the thermal hydraulic design and analysis of a whole device. 相似文献
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Jeffrey D. Templeton Seyed Ali Ghoreishi-Madiseh Ferri P. Hassani Agus P. Sasmito Jundika C. Kurnia 《国际能源研究杂志》2020,44(12):9609-9616
The geothermal potential available from deep underground mines has yet to be utilized. However, stope-coupled heat exchangers (SCHE) are aiming to take advantage of the unused low-grade geothermal energy. Backfilled stopes provide a unique opportunity to install nonlinear heat exchangers, as the geometry is not limited to the shape of a borehole. Helical pipes deliver superior fluid mixing and heat exchange compared to straight pipes, due to the effect of the secondary flow within the helical pipe. The helical closed-loop geothermal heat exchanger enables the backfilled stopes of the mine to be repurposed as thermal energy storage units. This article delves into the experimental results from a unique state-of-the-art laboratory scale helical closed-loop heat exchanger with varying thermophysical parameters. Additionally, a novel conjugate numerical model is developed and its results are validated against the base case of the experimental studies. Additionally, the numerical model is validated in a spatial-temporal sense with thermocouple data from the experimental rig. The numerical model is also applied to a helical SCHE situated within a backfilled stope for the first time. The results of the numerical model suggest that the pumping rate through the SCHE has a significant effect on the heat exchange rate and the overall energy transfer between the SCHE and the backfill. Additionally, the temperature contours from the numerical model suggest that a decreased pitch/helical diameter will increase the storage capacity of the helical SCHE. Overall, an average of 2.5 MW can be stored over the first 4 days of geothermal charging with the investigated full-scale SCHE, boasting a pseudo-steady-state storage rate of 1.7 MW. 相似文献