Numerical Investigation of Forced Convection From Small Rectangular Coiled Pipes

2006 ◽  
Author(s):  
Ibrahima Conte ◽  
Zhen Yang ◽  
Xiaofeng Peng
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Numerical Investigation ◽  
Forced Convection ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Inlet Velocity ◽  
Small Pitch ◽  
Pitch Distance

Investigations are done to numerically analyze forced convection from rectangular coiled pipes using commercial CFD software Fluent 6.0. The problems considered were three-dimensional laminar flow with water inside and outside the pipe. Calculations are done for two rectangular coiled pipes of different values of pitch (distance between two adjacent coils centers). The shift of location of the water flow maximum velocity was significantly observed in the case of smaller pitch. It is expected that the higher pitch value reduces the effects of the torsion. The shift of the flow maximum velocity area allows the fluid to be mixed well inside the pipe. For the outside flow, the flow behavior and the heat transfer should be improved by increasing the outside inlet velocity for the case of small pitch.

Heat Transfer for Laminar Flow in Spiral Ducts of Rectangular Cross Section

2005 ◽  
Vol 127 (3) ◽  
pp. 352-356 ◽  
Author(s):  
Michael W. Egner ◽  
Louis C. Burmeister
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Aspect Ratios ◽  
Small Pitch

Laminar flow and heat transfer in three-dimensional spiral ducts of rectangular cross section with aspect ratios of 1, 4, and 8 were determined by making use of the FLUENT computational fluid dynamics program. The peripherally averaged Nusselt number is presented as a function of distance from the inlet and of the Dean number. Fully developed values of the Nusselt number for a constant-radius-of-curvature duct, either toroidal or helical with small pitch, can be used to predict those quantities for the spiral duct in postentry regions. These results are applicable to spiral-plate heat exchangers.

Numerical Investigations of Forced Convection From Rectangular Coiled Pipes

2007 ◽  
Author(s):  
Ibrahima Conte´ ◽  
Xiao-Feng Peng ◽  
Zhen Yang
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Secondary Flow ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Heat Transfer Process ◽  
Single Vortex ◽  
Staggered Arrangement ◽  
Inclination Angles ◽  
Turbulent Air Flow

Investigations are done to numerically study forced convective heat transfer from the flow inside a rectangular coiled pipe, as micro-scale heat exchange device with staggered arrangement, to the external flow around the pipe. The commercial CFD software Fluent 6.0 is used as the solver. The problems considered were three-dimensional laminar flow of the refrigerant R141B through the tube and turbulent air flow exterior to the tube. The studied coiled pipe was composed of four rows among which two rows were encompassed in a large rectangular coil and the other two were in an inner smaller rectangular coil. The results showed remarkable differences in the flow behavior and heat transfer for different rows of tubes. The secondary flow in the tubes bends of the larger rectangular coil is very weak compared to that of the inner rectangular coil. Better heat transfer process occurred through the tubes of the second row where the higher values of the fluid temperatures were observed in the pipe. The results showed the effects of the straight tubes inclination angle on the flow behavior in rectangular coiled pipes. The shape of the secondary flow is changed from a couple of vortices in the case of smaller angle (α = 9°) to a single vortex in the case of larger angle (α = 45°). The results also showed the rotation of the maximum axial velocity due to the increase in the straight tubes inclination angles. The results are in good agreement with previous numerical and experimental works on laminar flow in helical coil pipe.

Laminar Flow and Heat Transfer in Spiral Ducts of Rectangular Cross Section

2004 ◽  
Author(s):  
Michael W. Egner ◽  
Louis C. Burmeister
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Small Pitch

Laminar flow and heat transfer in three-dimensional spiral ducts of rectangular cross section with aspect ratios of 1, 4, and 8 were determined with the aide of the FLUENT computational fluid dynamics program. Peripherally-averaged coefficients of friction and Nusselt numbers are presented as a function of distance from the inlet and of the Dean number. Fully-developed values of friction coefficient and Nusselt number for a constant-radius-of-curvature duct, either toroidal or helical with small pitch, can be used to predict those quantities for the spiral duct in post-entry regions. These results are applicable to spiral-plate heat exchangers.

Computational and Experimental Study of Enhanced Laminar Flow Heat Transfer in Three-Dimensional Sinusoidal Wavy-Plate-Fin Channels

2003 ◽  
Author(s):  
Jiehai Zhang ◽  
Arun Muley ◽  
Joseph B. Borghese ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Flow Behavior ◽  
Computational Simulation ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Staggered Grid ◽  
Uniform Heat Flux ◽  
Complex Flow ◽  
Constant Property ◽  
Fin Efficiency

Enhanced heat transfer characteristics of low Reynolds number airflows in three-dimensional sinusoidal wavy plate-fin channels are investigated. For the computational simulation, steady state, constant property, periodically developed, laminar forced convection is considered with the channel surface at the uniform heat flux condition; the wavy-fin is modeled by its two asymptotic limits of 100% and zero fin efficiency. The governing equations are solved numerically using finite-volume techniques for a non-orthogonal, non-staggered grid. Computational results for velocity and temperature distribution, isothermal Fanning friction factor f and Colburn factor j are presented for airflow rates in the range of 10 ≤ Re ≤ 1500. The numerical results are further compared with experimental data, with excellent agreement, for two different wavy-fin geometries. The influence of fin density on the flow behavior and the enhanced convection heat transfer are highlighted. Depending on the flow rate, a complex flow structure is observed, which is characterized by the generation, spatial growth and dissipation of vortices in the trough region of the wavy channel. The thermal boundary layers on the fin surface are periodically disrupted, resulting in high local heat fluxes. The overall heat transfer performance is improved considerably, compared to the straight channel with the same cross-section, with a relatively smaller increase in the associated pressure drop penalty.

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