Experimental investigation on pressure drop and friction factor of slush nitrogen turbulent flow in helically corrugated pipes

Cryogenics ◽  
2018 ◽  
Vol 94 ◽  
pp. 56-61 ◽  
Author(s):  
Yijian Li ◽  
Shuqin Wu ◽  
Tao Jin
Keyword(s):  
Experimental Investigation ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor

Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Henrique Stel ◽  
Rigoberto E. M. Morales ◽  
Admilson T. Franco ◽  
Silvio L. M. Junqueira ◽  
Raul H. Erthal ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Geometric Configurations ◽  
Corrugated Surfaces ◽  
Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

Effect of Groove Dimension on Thermal Performance of Turbulent Fluid Flow in Internally Grooved Tube

2016 ◽  
Author(s):  
Sogol Pirbastami ◽  
Samir Moujaes
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Kinetic Energy ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulent Kinetic Energy ◽  
Thermal Performance ◽  
Tube Length ◽  
Pitch Length

A Computational Fluid Dynamics (CFD) study of heat enhancement in helically grooved tubes was carried out by using a 3-dimensional simulation with the STARCCM+ simulation package software. The k-ε model selected for turbulent flow simulation and the governing equations were solved by using the finite volume method. Geometric models of the current study include 3 rectangular grooved tubes with different groove width (w) and depth (e) which varies from 0.2 mm to 0.6 mm for the same tube length of 2.0m and diameter of 7.1 mm. The simulations were performed in the Reynolds number (Re) range of 4000–10000 with a uniform wall heat flux of 3150 w/m2 applied as a boundary condition on the surface of each tube. The purpose of this research is to investigate the effect of different groove dimensions on the thermal performance and pressure drop of water inside the grooved tubes and clarify the structural nature of the flow in regards to flow swirl and turbulent kinetic energy distributions. It was found that the highest performance belongs to the groove with these dimensions (w = 0.2 mm and e = 0.2 mm) which was considered for further study. Then, for these same groove dimensions four pitch size to tube diameter (p/D) ratios ranging from 1 to 18 were simulated for the same 2.0 m length tube. The results for Nusselt number (Nu) and friction factor (f) showed that by increasing the (p/D) ratio both the Nu numbers and the friction factors (f) values decrease. With a smaller pitch length (p) the turbulence intensity generated by the internal groove was also found to increase. The physical behavior of the turbulent flow and heat transfer characteristics were observed by contour plots which showed an increasing swirl flow and turbulent kinetic energy as p/D decreases. With an increase of the Nu number for smaller p/D ratio, a penalty of a higher pressure drop was obtained. The results were validated with a previous experimental work and the average error between the experimental and CFD Nu numbers and f were 13% and 8% respectively. A higher level of turbulent kinetic energy is observed near the grooves, as compared to the smooth areas of the pipe surface away from the grooves, which are expected to lead to higher levels of heat transfer. The effect of pitch length (p) on the flow pattern were plotted by streamlines along the tubes, by decreasing the pitch size (p/D ratio) an increase in the swirl is noticed as evidenced by the plots of the path lines. Finally, empirical correlations for Nusselt number and friction factor were provided as a function of p/D and Re number. This study indicates that the incorporation of the internal groove, of particular dimensions, can lead to an improvement of performance in heat exchanger devices. A limited variation of the groove dimensions was conducted and it was found that the values of Nu and f do not improve with an increase of (w) nor with that of (e) from 0.2–0.6 mm.

Experimental Investigations on Heat Transfer Enhancement in a Horizontal Tube Using Converging and Diverging Conical Strip Inserts

2014 ◽  
Vol 592-594 ◽  
pp. 1590-1595 ◽  
Author(s):  
Naga Sarada Somanchi ◽  
Sri Rama R. Devi ◽  
Ravi Gugulothu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Heat Transfer Enhancement ◽  
Friction Factor ◽  
Working Fluid ◽  
Experimental Investigations ◽  
Transfer Enhancement ◽  
Enhancement Of Heat Transfer

The present work deals with the results of the experimental investigations carried out on augmentation of turbulent flow heat transfer in a horizontal circular tube by means of tube inserts, with air as working fluid. Experiments were carried out initially for the plain tube (without tube inserts). The Nusselt number and friction factor obtained experimentally were validated against those obtained from theoretical correlations. Secondly experimental investigations using three kinds of tube inserts namely Rectangular bar with diverging conical strips, Rectangular bar with converging conical strips, Rectangular bar with alternate converging diverging conical strips were carried out to estimate the enhancement of heat transfer rate for air in the presence of inserts. The Reynolds number ranged from 8000 to 19000. In the presence of inserts, Nusselt number and pressure drop increased, overall enhancement ratio is calculated to determine the optimum geometry of the tube insert. Based on experimental investigations, it is observed that, the enhancement of heat transfer using Rectangular bar with converging and diverging conical strips is more effective compared to other inserts. Key words: Heat transfer, enhancement, turbulent flow, conical strip inserts, friction factor, pressure drop.

Effect of Bend Geometry on Heat Transfer and Pressure Drop in a Two-Pass Coolant Square Channel for a Turbine

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Krishnendu Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Thermal Performance ◽  
Numerical Study ◽  
Solution Procedure ◽  
Internal Cooling ◽  
Square Channel ◽  
End Wall

This paper presents a comparative numerical study of turbulent flow inside a two-pass internal cooling channel with different bend geometries. The goal is to find a geometry that reduces the bend related pressure loss and enhances overall heat transfer coefficient. A square channel with a round U-bend is taken as a baseline case and the heat transfer and pressure drop for nine different bend geometries are compared with the baseline. Modifications for the bend geometry are made along the channel divider wall and at the end wall of the 180 deg bend. The bend geometries studied include: (1) a turning vane geometry, (2) an asymmetrical bulb, (3) three different symmetrical bulbs, (4) two different bow shaped geometries at the end wall, (5) a bend with an array of dimples in the bend region, and (6) finally a combination of bow geometry and dimples. The solution procedure is based on a commercial finite volume solver using the Reynolds averaged Navier–Stokes (RANS) equation and a turbulence model. A two equation realizable k-ɛ model with enhanced wall treatment is used to model the turbulent flow. It was found that the bend geometry can have a significant effect on the overall performance of a two-pass channel. The modified bend geometries are compared with the baseline using Nusselt number ratios, friction factor ratios, and thermal performance factors (TPF) as the metrics. All the modified bend geometries show increase in the TPF with the symmetrical bulb configuration showing nearly a 40% reduction in friction factor ratio and a 30% increase in thermal performance. The highest TPF (41% increase over baseline) is observed for the symmetrical bulb combined with a bow along the outer walls and surface dimples.

Heat transfer at low temperatures between tube walls and gases in turbulent flow

1947 ◽  
Vol 191 (1024) ◽  
pp. 6-21 ◽  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Low Temperatures ◽  
Reynolds Numbers ◽  
Internal Diameter ◽  
Fluid Temperature ◽  
External Diameter ◽  
Bulk Fluid

An apparatus was designed on the counter-flow system to study heat transfer between tube walls and gases at low temperatures in a region in which careful measurements had not previously been made. Oxygen, nitrogen and carbon dioxide were used, covering a temperature range from + 45° to –167° C, pressures up to 11 atm., and Reynolds numbers from 3000 to 60,000. Results were correlated by the use of dimensionless groups and a general equation ob­tained, independent of the nature of the gas and applicable over the whole range of experi­ments. With Reynolds numbers evaluated at mean film temperatures, the coefficient in the equation was found to be 5% lower than that obtained from measurements made at normal and high temperatures. This is regarded as justifying the extension of the ordinary equation to low-temperature regions. Determinations on friction accompanying heat transfer with gases in turbulent flow at low temperatures showed that the effect of heat transfer on the friction factor was small. Nomenclature C constant in Sutherland equation. D diameter of tube; equivalent diameter of annulus, i. e. internal diameter of outer tube minus external diameter of inner tube. F frictional force per lb. of fluid. L length of tube. T absolute temperature, ° K. V linear velocity of gas, as calculated from mass flow per unit time per unit of cross sectional area, divided by the mean density of the fluid. c specific heat of fluid at constant pressure. f friction factor, or coefficient of proportionality in pressure drop equation. g acceleration due to gravity. h coefficient of heat transfer between fluid and surface. k thermal conductivity of fluid. r, s constants (used as exponents). α, β constants. ϕ(x) function of x . μ absolute viscosity of fluid. ρ absolute density of fluid. Δp pressure drop in pipe. Subscripts a refers to annulus. i refers to inner tube. f refers to properties evaluated at film temperatures. Film temperature is taken as the arithmetic mean of the bulk fluid temperature and the tube-wall temperature.

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