Impact of reattachment surface characteristics on the flow field generated by slot jet reattachment nozzle – A numerical study
Impact of reattachment surface characteristics on the flow field generated by slot jet reattachment nozzle – A numerical study
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DOI：
10.1080/07373937.2022.2150862
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发表时间：
2022-12
影响因子：
3.3
通讯作者：
M. E. Asar;Mengqiao Yang;J. Yagoobi
中科院分区：
文献类型：
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作者：
M. E. Asar;Mengqiao Yang;J. Yagoobi
摘要缝隙射流再附着喷嘴是一种新型的喷嘴设计，在湿物料的传热和干燥、加热或冷却应用中，它的性能优于常规的冲击喷嘴或多孔板。SJR喷嘴是一种可行的设计，用于干燥食品和纸张等易碎产品。网式输送带通常用于食品工业。有必要了解SJR喷嘴如何与网状输送带一起使用，因为以前的研究仅考虑固体表面。因此，我们使用COMSOL Multiphysics®（不包括传热）进行了广泛的数值研究，以求解SJR喷嘴的流场，喷嘴出口角为+45°，位于网状带顶部，有无产品。采用k-ε湍流模型对SJR喷管的湍流流动进行了理论模拟.数值预测与实验数据进行了验证静止表面。研究了六种不同的情况，以捕捉产品在带上的存在和传送带速度的影响。此外，SJR喷嘴的存在下，带的底部有和没有横向偏移进行了研究。将皮带下方逸出的质量流率与喷嘴出口处的总质量流率进行比较，在三种不同的表面速度下比较剪切应力，并报告产品行进时的最大力值。结果表明，无论表面运动如何，流动都可以重新附着到产品表面，但重新附着特性取决于产品相对于SJR喷嘴的方向。虽然大量的质量流通过传送带逃逸，但产品的存在减轻了这种损失。此外，加倍的带速度增加了由表面施加的剪切应力，并降低了平均质量流损失。此外，即使喷嘴之间存在横向偏移，在皮带底部的附加SJR喷嘴也几乎消除了这种质量流损失。
Abstract Slot jet reattachment (SJR) nozzle is a novel nozzle design that overperforms the regular impingement nozzles or perforated plates for heat transfer and drying, heating or cooling applications of moist materials. The SJR nozzle is a viable design to dry fragile products such as food and paper. Mesh-type conveyor belts are commonly used in the food industry. There is a need for understanding how the SJR nozzle performs with mesh-type conveyor belts because prior studies have solely considered solid surfaces. Therefore, an extensive numerical study is performed to solve the flow field of the SJR nozzle with an exit angle of +45° on top of a mesh-type belt with and without products using COMSOL Multiphysics® without including heat transfer. Turbulent fluid flow is theoretically modeled using the k-ɛ turbulence model for the SJR nozzle. The numerical predictions are validated with experimental data for stationary surface. Six different cases are studied to capture the effects of the presence of products on the belt and the conveyor belt speed. Additionally, the presence of an SJR nozzle on the bottom of the belt with and without a lateral offset is studied. The mass flow rate escaping underneath the belt is compared to the total mass flow rate at the nozzle exit, shear stresses are compared at three different surface velocities, and maximum force magnitudes as product travels are reported. The results show that the flow can reattach to the product surface regardless of surface motion, but reattachment characteristics depend on product orientation with respect to the SJR nozzle. Although significant mass flow escapes through the belt, the presence of products mitigates this loss. In addition, doubling the belt speed increases the shear stresses applied by the surface and decreases the average mass flow loss. Also, an additional SJR nozzle on the bottom of the belt almost cancels this mass flow loss even when there is a lateral offset between the nozzles.