Theoretical Analysis of Resonance Tube End Wall Heating: Solution of Unsteady Fluid Dynamic and Energy Equations

2015 ◽  
Author(s):  
Ramlala P. Sinha
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamic ◽  
Stable Solution ◽  
Heat Conducting ◽  
Cross Sectional ◽  
Arbitrary Boundary ◽  
Resonance Tube ◽  
Unsteady Fluid ◽  
Energy Equations ◽  
End Wall

A solution of the highly complex unsteady compressible flow field inside a cylindrical resonance tube has been obtained numerically, assuming one dimensional, viscous, and heat conducting flow, by solving the appropriate fluid dynamic and energy equations. The resonance tube is approximated by a right circular cylinder closed at one end with a piston oscillating at resonant frequency at the other end. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for transport properties. For the example considered herein, the solution predicts a rise of 95°F in the mean end wall temperature, from 60°F to 155°F, in 14.313 milliseconds which is in good agreement with the experimentally observed values. The solution would also be valid for tapered tubes if the variations in the cross-sectional area are small. In successfully predicting the resonance tube results, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide ranging research, development, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid-structure interaction heat transfer enhancement, and fluidic pyrotechnic initiation devices.

Solution of Unsteady Fluid Dynamic and Energy Equations for High-Speed Oscillating Compressible Flows and Blast Wave Propagations

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Ramlala P. Sinha
Keyword(s):  
Heat Transfer ◽  
Blast Wave ◽  
High Speed ◽  
Fluid Dynamic ◽  
Stable Solution ◽  
Heat Conducting ◽  
Arbitrary Boundary ◽  
One Dimensional ◽  
Unsteady Fluid ◽  
Energy Equations

Abstract A solution of the highly complex unsteady high-speed oscillating compressible flow field inside a cylindrical tube has been obtained numerically, assuming one-dimensional, viscous, and heat conducting flow, by solving the appropriate fluid dynamic and energy equations. The tube is approximated by a right circular cylinder closed at one end with a piston oscillating at very high resonant frequency at the other end. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for transport properties. The solution would also be valid for tapered tubes if the variations in the cross-sectional area are small. In successfully predicting the time-dependent results, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide-ranging research, design, development, analysis, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid–structure interaction heat transfer enhancement, and fluidic pyrotechnic initiation devices. It can further be easily extended to cover muzzle blasts and nuclear explosion blast wave propagations in one-dimensional and/or radial spherical coordinates with or without including energy generation/addition terms.

Time-Dependent Solution of Unsteady Fluid Flow Equations for High Speed Oscillating Compressible Flows and Blast Wave Propagations

2020 ◽  
Author(s):  
Ramlala P. Sinha
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Blast Wave ◽  
High Speed ◽  
Fluid Dynamic ◽  
Time Dependent ◽  
Arbitrary Boundary ◽  
One Dimensional ◽  
Unsteady Fluid ◽  
Energy Equations

Abstract A solution of the highly complex unsteady high speed oscillating compressible flow field inside a cylindrical tube has been obtained numerically, assuming one dimensional, viscous, and heat conducting flow, by solving the appropriate fluid dynamic and energy equations. The tube is approximated by a right circular cylinder closed at one end with a piston oscillating at very high resonant frequency at the other end. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for transport properties. The solution would also be valid for tapered tubes if the variations in the cross-sectional area are small. In successfully predicting the time dependent results, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide ranging research, design, development, analysis, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid-structure interaction heat transfer enhancement, and fluidic pyrotechnic initiation devices. It can further be easily extended to cover muzzle blasts and nuclear explosion blast wave propagations in one dimensional and/or radial spherical coordinates with or without including energy generation / addition terms.

Unsteady Heat Transfer in Baffled Channels

1996 ◽  
Vol 118 (3) ◽  
pp. 585-591 ◽  
Author(s):  
G. Wang ◽  
K. Stone ◽  
S. P. Vanka
Keyword(s):  
Heat Transfer ◽  
Critical Reynolds Number ◽  
Reynolds Numbers ◽  
Process Industry ◽  
Unsteady Heat Transfer ◽  
Enhancement Of Heat Transfer ◽  
Compact Heat Exchangers ◽  
Unsteady Fluid Flow ◽  
Unsteady Fluid ◽  
Energy Equations

In this paper, the enhancement of heat transfer due to unsteady flow in channels with in-line and staggered baffles is investigated through the numerical solution of the governing unsteady fluid flow and energy equations with periodicity in the stream wise direction. For the inline configuration, the flow becomes naturally unsteady at a critical Reynolds number (Q/v) around 110. For the staggered case, this value is around 200. Significant increases in heat transfer rate are observed once the flow becomes unsteady. Results for several Reynolds numbers up to 500 are presented. The present results can be valuable to the design and operation of compact heat exchangers used in process industry.

scholarly journals JUSTIFIKASI CFD KEDALAMAN GROOVE BAN PADA PROSES PERAWATAN HARIAN PESAWAT B737-800 AKIBAT HYDROPLANING (B737-800 TIRE GROOVE DEPTH CFD JUSTIFICATION ON ITS DAILY MAINTENANCE PROCESS DUE TO HYDROPLANING)

2017 ◽  
Vol 15 (1) ◽  
pp. 29 ◽  
Author(s):  
Vicky Wuwung ◽  
Nelli Anggreyni ◽  
Valeri Maria Hitoyo ◽  
Carolus Bintoro
Keyword(s):  
Numerical Simulation ◽  
Rigid Body ◽  
Lift Force ◽  
Flat Surface ◽  
Fluid Dynamic ◽  
Groove Depth ◽  
Cross Sectional ◽  
Unsteady Fluid ◽  
Short Time ◽  
Maintenance Process

As a reference in daily maintenace process of Boeing 737-800 air plane, The tire groove depth influence justification which is moving on the contaminated runway that could be potential to hydroplaning phenomenon must be reviewed. Tire groove is a pattern on the tire surface that has a function to flow the water in front of the tire to the aft of the tire smoothly through the bottom of the tire. This mechanism let the tire less of a lift force that can be meant as a hydroplaning prevention. To understand hydroplaning phenomenon and groove depth tire influence, a numerical simulation is performed by using a CFD software Numeca Fine/Marine. This simulation is 3D, unsteady fluid dynamic simulation, with an assumption a rigid body tire at a short time after the airplane touch down to the runway (after skidding process) with velocity V = 62.27 m/s. The contaminated runway is modelled as a pool water (flood) on the flat surface runway with its height of 2.54 mm. Numerical simulation on this B 737-800 tire result shows that a hydroplaning phenomenon will happen for tire with groove depth less than 0.4”. This concludes that a lesser groove depth of tire will reduce a tire groove cross sectional area, and will increase a compression force in the bottom at the front of the tire, that will result in increasing a lift force to the tire and finally increasing a chance to hydroplaning process. From this result, furthermore, the influence of this groove depth of B 737-800 tire variation that is run on a contaminated runway can be used as a reference on B 737-800 tire daily maintenance. AbstrakGroove atau ‘kembang” pada ban pesawat merupakan sarana untuk mengalirkan air dari bagian depan menuju bagian belakang melalui bagian bawah ban, tanpa mengangkat ban sehingga dapat mencegah terjadinya hydroplaning. Sehingga, pengaruh nilai kedalaman groove terhadap gaya angkat pada ban pesawat B737-800 yang bergerak di landasan dengan genangan air perlu dijustifikasi dalam proses perawatan harian. Penelitian ini menyimulasikan proses mengalirnya air pada bagian bawah ban dengan menggunakan simulasi numerik (CFD Numeca Fine/Marine) 3-D unsteady sebagai metode untuk menjustifikasi pengaruh groove. Simulasi dilakukan untuk kondisi gerakan ban pesawat pada saat proses landing (V = 62,275 m/s) beberapa saat setelah touch down (setelah skidding) dengan ban pesawat dianggap rigid body sebagai kondisi batas. Selanjutnya tinggi genangan air dipilih pada saat runway dinyatakan dalam kondisi flood (tinggi genangan air = 2,54mm). Simulasi tersebut menampilkan hasil perhitungan ban pesawat Boeing 737-800, dengan hydroplaning mulai terjadi ketika kedalaman groove ban berada dibawah 0,4 inch. Hal ini menunjukkan bahwa semakin kecil kedalaman groove, maka semakin kecil luas penampang groove dan semakin besar gaya kompresi yang terjadi pada bagian bawah ban dan semakin memperbesar kemungkinan terjadinya fenomena hydroplaning. Dengan diketahuinya hasil dari simulasi tersebut, maka hasil penelitian ini dapat digunakan sebagai masukan bagi proses maintenance harian pesawat B737-800 dan mampu memberikan suatu hal baru dalam pembelajaran khususnya mengenai fenomena hydroplaning.

Numerical Heat Transfer and Fluid Flow Modeling of a Nano-Robot Inside the Blood Stream of an Aorta

2007 ◽  
Author(s):  
M. Ghassemi ◽  
M. Varmarzyar ◽  
M. K. Ebrahimi ◽  
M. Zare
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamic ◽  
Nonlinear Partial Differential Equations ◽  
Blood Stream ◽  
Nano Technology ◽  
Medical Treatments ◽  
Numerical Heat Transfer ◽  
Promising Area ◽  
Energy Equations ◽  
Fluid Flow Modeling

The idea of nano-technology started in 1959. It has been used in different applications since its creation. One of its new areas of applications is in medicine. From medical instruments (i.e. sensors etc) to medical treatments nano-technology is playing a major role. Application of nano-robot inside human blood for health purposes is a promising area. The purpose of this study is to investigate the flow field and heat transfer modeling of a nano-robot inside the biggest human vein, Aorta. In our formulation of governing nonlinear partial differential equations, momentum and energy equations are applied to the blood and the nano-robot. The equations are solved by a computational fluid dynamic code. The velocity profile, pressure and temperature distribution of the nano-robot in direction of the blood stream as well as in opposite direction of the blood stream are calculated. Results are verified with a known experimental condition. Results show that the nano-robot does not disturb the blood stream significantly. Therefore it is safe to use such devices inside blood stream for medical purposes.

scholarly journals Experimental performance comparison between circular and elliptical tubes in evaporative condensers

2021 ◽  
Author(s):  
Giuseppe Starace ◽  
Lorenzo Falcicchia ◽  
Pierpaolo Panico ◽  
Maria Fiorentino ◽  
Gianpiero Colangelo
Keyword(s):  
Heat Transfer ◽  
Experimental Approach ◽  
Fluid Dynamic ◽  
Major Axis ◽  
Performance Comparison ◽  
Operating Conditions ◽  
Condensation Temperature ◽  
Air Cooled Condensers ◽  
Reduced Scale ◽  
Dynamic Phenomena

AbstractIn refrigeration systems, evaporative condensers have two main advantages compared to other condensation heat exchangers: They operate at lower condensation temperature than traditional air-cooled condensers and require a lower quantity of water and pumping power compared to evaporative towers. The heat and mass transfer that occur on tube batteries are difficult to study. The aim of this work is to apply an experimental approach to investigate the performance of an evaporative condenser on a reduced scale by means of a test bench, consisting of a transparent duct with a rectangular test section in which electric heaters, inside elliptical pipes (major axis 32 mm, minor axis 23 mm), simulate the presence of the refrigerant during condensation. By keeping the water conditions fixed and constant, the operating conditions of the air and the inclination of the heat transfer geometry were varied, and this allowed to carry out a sensitivity analysis, depending on some of the main parameters that influence the thermo-fluid dynamic phenomena, as well as a performance comparison. The results showed that the heat transfer increases with the tube surface exposed directly to the air as a result of the increase in their inclination, that has been varied in the range 0–20°. For the investigated conditions, the average increase, resulting by the inclination, is 28%.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

Experimental Measurements of the Flow and Heat Transfer of a Square Jet Impinging on an Array of Square Pin Fins

2002 ◽  
Author(s):  
Johnny S. Issa ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flow Behavior ◽  
Jet Impingement ◽  
Tip Clearance ◽  
Heat Sinks ◽  
Clearance Ratio ◽  
Cross Sectional ◽  
Pressure Loss Coefficient ◽  
Air Jet

An experimental investigation was conducted to explore the flow behavior, pressure drop, and heat transfer due to free air jet impingement on square in-line pin fin heat sinks (PFHS) mounted on a plane horizontal surface. A parametrically consistent set of aluminum heat sinks with fixed base dimension of 25 × 25 mm was used, with pin heights varying between 12.5 mm and 22.5 mm, and fin thickness between 1.5 mm and 2.5 mm. A 6:1 contracting nozzle having a square outlet cross sectional area of 25 × 25 mm was used to blow air at ambient temperature on the top of the heat sinks with velocities varying from 2 to 20 m/s. The ratio of the gap between the jet exit and the pin tips to the pin height, the so-called tip clearance ratio, was varied from 0 (no tip clearance) to 1. The stagnation pressure recovered at the center of the heat sink was higher for tall pins than short pins. The pressure loss coefficient showed a little dependence on Re, increased with increasing pin density, and pin diameter, and decreased with increasing pin height and clearance ratio. The overall base-to-ambient thermal resistance decreased with increasing Re number, pin density and pin diameter. Surprisingly, the dependence of the thermal resistance on the pin height and clearance ratio was shown to be mild at low Re, and to vanish at high Re number.

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