Influence of Geometrical Parameters on Heat Transfer of Transversely Corrugated Helically Coiled Tube for Deicing Fluid

In order to ensure flight safety in cold winter, aircraft ground deicing is crucial and necessary. In Chinese deicing fluid heating system, the helically coiled tube is paramount exchanger to heat deicing fluid. The deicing fluid is ethylene-glycol-based mixture with high viscosity. Aiming at heat transfer enhancement of deicing fluid, ring rib is formed by an embossed tube wall toward the internal of the tube; thus, transversely corrugated helically coiled tube (TCHC) is achieved. Depth and width are two key geometrical parameters of ring rib. Based on field synergy principle, the influence of depth–diameter ratio (H/D) and width-diameter ratio (w/D) is investigated through numerical simulation. The results show that outlet temperature, mean convection heat transfer coefficient, and Nusselt number have similar trends, which first increase and then decrease nonlinearly. The variation of flow resistance coefficient is inversely proportional to Reynolds number. Especially, the effect of H/D is more significant than that of w/D. Field synergy angle and velocity field are also analyzed to reveal the mechanism of heat transfer. TCHC performs better than the original tube. Orthogonal experiment calculates the outlet temperature of TCHC when H/D and w/D change. The combination of H/D=0.075 and w/D=0.5 is best solution. TCHC effectively enhances heat transfer of deicing fluid. Therefore, TCHC is beneficial to improve the deicing efficiency and ensure the flight punctuality.

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Research on the Heating of Deicing Fluid in a New Reshaped Coiled Tube

Mathematical Problems in Engineering ◽

10.1155/2017/3254631 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9 ◽

Cited By ~ 7

Author(s):

Mengli Wu ◽

Chiyu Wang ◽

Yunpeng Li ◽

Qi Nie

Keyword(s):

Heat Transfer ◽

Ethylene Glycol ◽

Heating System ◽

High Viscosity ◽

Negative Influence ◽

Heating Time ◽

Temperature Fields ◽

Outlet Temperature ◽

Coiled Tube ◽

Deicing Fluid

Aircraft ground deicing operation is significant to ensure civil flight safety in winter. Helically coiled tube is the important heat exchanger in Chinese deicing fluid heating system. In order to improve the deicing efficiency, the research focuses on heat transfer enhancement of deicing fluid in the tube. Based on the field synergy principle, a new reshaped tube (TCHC) is designed by ring-rib convex on the inner wall. Deicing fluid is high viscosity ethylene-glycol-based mixture. Because of the power function relation between high viscosity and temperature, viscosity has a negative influence on heat transfer. The number of ring-ribs and inlet velocity are two key parameters to the heat transfer performance. For both water and ethylene glycol, the outlet temperature rises when the number of ring-ribs increases to a certain limit. However, the increasing of velocity reduces heating time, which results in lower outlet temperature. The heating experiment of the original tube is conducted. The error between experiment and simulation is less than 5%. The outlet temperature of TCHC increases by 3.76%. As a result, TCHC efficiently promotes the coordination of velocity and temperature fields by changing the velocity field. TCHC has enhanced heat transfer of high viscosity deicing fluid.

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Numerical Simulation of Interfacial Phenomenon of Air-Water Adiabatic Intermittent Flow in Helically Coiled Tubes

Volume 4: Computational Fluid Dynamics (CFD) and Coupled Codes; Decontamination and Decommissioning, Radiation Protection, Shielding, and Waste Management; Workforce Development, Nuclear Education and Public Acceptance; Mitigation Strategies for Beyond Design Basis Events; Risk Management ◽

10.1115/icone24-60221 ◽

2016 ◽

Author(s):

Guangyu Zhu ◽

Hongye Zhu

Keyword(s):

Heat Transfer ◽

Centrifugal Force ◽

Two Phase Flow ◽

Intermittent Flow ◽

Geometrical Parameters ◽

Phase Flow ◽

Two Phase ◽

Coiled Tube ◽

Helically Coiled Tube ◽

Coil Diameter

Helically coiled tube are widely used as the basic heat transfer elements in steam generators of the next generation reactors, such as HTR-PM (High Temperature Gas-cooled Reactor), IRIS (International Reactor Innovative and Secure) and SMART (System-integrated Modular Advanced Reactor), because of the advantages in reducing space, enhancing heat transfer, accommodating thermal stress and preventing two-phase flow instabilities. Owing to the presence of gravity and centrifugal force that being perpendicular to the main flow, two-phase flow in helically coiled tubes has different features with either vertical flow or horizontal flow. To ensure safety and reliability of the plant, it is necessary to carry out detail investigation on the two-phase flow phenomena and mechanisms in helically coiled tubes. However, less research has been carried out on this subject than on straight tubes. In this work, the upward air-water slug and plug flows in helically coiled tubes have been numerically analyzed based on the computational fluid dynamics (CFD) techniques. Three dimension models of helically coiled tubes with inner diameter of 16 mm, coil diameter of 0.1 and 0.4m, pitch of 0.08 and 0.16m are constructed, for which the structural meshes are generated by software ANSYS ICEM. The gas-liquid interface is captured by the volume of fluid (VOF) approach adopting geo-reconstruction scheme for interface interpolation, which is solved by a pressure-based transient solver in the commercial CFD software ANSYS FLUENT 14.5. Bubble chord length, slug/plug frequency, bubble velocity and void fraction under different superficial velocities have been investigated. The numerical results meet well with the pictures recorded by a high speed camera. It is revealed that in slug regime, the bubbles mainly migrate towards the top and inner wall of the tube due to the combined action of gravity and centrifugal force, leading to a highly asymmetrical internal phase distributions. Meanwhile, the secondary flow in the cross section introduced by the centrifugal force enhances the turbulence and prevents small bubbles to coalescent into enlarged bubbles. Accordingly the intermittent flow regime in helically coiled tubes is narrower than that in straight horizontal tubes. Furthermore, the influences of geometrical parameters on phase distribution characteristics are predicted. The results show that the bubble length will increase along with the increase of the coil diameter or the pitch of the helically coiled tube. And the bubble frequency will increase with the decreasing of the tube coil diameter.

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