On Fluid Flow and Heat Transfer in a Pipe With a U-Bend

2013 ◽  
Author(s):  
Christopher G. Cvetkovski ◽  
Hoda S. Mozaffari ◽  
Stanley Reitsma ◽  
Tirupati Bolisetti ◽  
David S.-K. Ting
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Pumps ◽  
Heat Transfer Fluid ◽  
Heated Wall ◽  
Dean Number ◽  
Ground Source Heat Pumps ◽  
Ground Source

Vertical ground source heat pumps operate by pumping a heat transfer fluid through a pipe buried in the ground. There is a U-Bend at its deepest point to return the fluid to the surface. Incidentally, the U-Bend does more than packing the extensive length of the heat transferring conduit within a single compact borehole. Large flow structures called Dean’s vortices are generated in the bend and these, along with the resulting turbulence produced, are known to significantly enhance the heat transfer processes, and hence, shorten the required length. This study examines the specific roles of Reynolds and Dean numbers on the flow structure and the resulting heat transfer in a pipe with a U-Bend. Water flowing in a pipe without and with heated wall was simulated using FLUENT. The model was verified based on available data in the literature. The efficacy of the local heat transfer rate along the pipe was cast with respect to the subtle changes in the flow characteristics under varying Reynolds number and Dean number.

scholarly journals Local Heat Transfer and Flow Characteristics in Two-Pass Channels with an Inclined Divider Wall.

2002 ◽  
Vol 68 (669) ◽  
pp. 1523-1530
Author(s):  
Masafumi HIROTA ◽  
Hiroshi NAKAYAMA ◽  
Lei CAI ◽  
Hideomi FUJITA ◽  
Tatsuhito KATOH ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat

Numerical Prediction of Flow and Heat Transfer Past a Circular Tube With Annular Fins

2003 ◽  
Author(s):  
D. Chakraborty ◽  
G. Biswas ◽  
P. K. Panigrahi
Keyword(s):  
Heat Transfer ◽  
Circular Tube ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Stagnation Line ◽  
Flow And Heat Transfer ◽  
Annular Fin ◽  
Annular Fins

A numerical investigation was carried out to study the flow and heat transfer behavior of a vertical circular tube, which is situated between two annular fins in cross-flow. The flow structure of the limiting streamlines on the surface of the circular tube and the annular fins was analysed. A finite volume method was employed to solve the Navier-Stokes and energy equations. The numerical results pertaining to heat transfer and flow characteristics were compared with the available experimental results. The following salient features were observed in this configuration. A horseshoe vortex system was formed at the junction of the stagnation line of the circular tube and the annular fin. The separation took place at the rear of the tube. The influence of the horseshoe vortices on local heat transfer was substantial. The ratio of the axial gap between two annular fins (L) to the radial protrusion length of the annular fin (LR) was identified as an important parameter. The flow and heat transfer results were presented for different L/LR ratios for a Reynolds number of 1000.

scholarly journals Analysis of Backward and Forward Effects on a Grooved Co-axial Heat Exchanger by Response Surface Methodology

2019 ◽  
Vol 111 ◽  
pp. 01092
Author(s):  
Şahin GÜNGÖR ◽  
Levent AYDIN ◽  
Umut CEYHAN ◽  
Büşra KAYA ◽  
Ziya Haktan KARADENİZ
Keyword(s):  
Heat Transfer ◽  
Response Surface Methodology ◽  
Response Surface ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heated Wall ◽  
Transfer Coefficients ◽  
Pipe Model ◽  
Energy Equations

In the literature, it is proved that grooved pipe models are thermally more efficient than the smooth pipe model. Different than the previous studies in which the groove dimensions are constant along the pipe, we study the effect of groove radius and the gap between adjacent grooves on the local heat transfer coefficients using computational fluid dynamics software. The grooved section consists of three sub-sections to see the effects of groove dimension in stream-wise flow direction. We vary the radius of circular grooves parametrically in each section to optimize the local groove radius throughout the pipe. We couple the fluid flow (1200<Re<24000) with energy equations, and the grooved sections are set as heated wall at constant temperature of 350 K. The optimal mesh has been selected by performing mesh independence study and finer mesh has been used in heated wall section. The radii of grooves are varied from 2 to 6 mm with an increment of 0.2 mm considering the manufacturability of the pipe, to do so we use the design of experiments (DOE). All DOE tools in ANSYS software are examined and compared with full factorial results. After DOE process, local heat transfer coefficient values of all groove parts are examined by response surface methodology (RSM).

Conjugate heat transfer analysis for laminar flow in pipes having a step change in boundary conditions and wall conductivity

2007 ◽  
Vol 221 (8) ◽  
pp. 919-925 ◽  
Author(s):  
M E Arici ◽  
M E Kaya
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Solid Wall ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Step Change ◽  
Heat Transfer Analysis ◽  
Heated Wall ◽  
Surface Boundary ◽  
Wall Conductivity

The current procedure is to examine the effects of wall axial conduction on heat transfer for laminar flow in pipes. The procedure combines the analytical solution of the problem of the fluid region with a numerical approximation of conduction of the solid wall and has the capability of handling the step change in outer surface boundary condition and wall thermal conductivity. The pipe under investigation is divided into two sections: non-heated and heated ones, and the conductivities of the sections are assumed to be different. The obtained results show that the local heat transfer parameters such as wall and fluid temperatures, and Nusselt number are greatly influenced by the step change in wall conductivity and the partially heated wall arrangement. The results of the present study may have applications in the design of heat transfer devices.

scholarly journals Field Test and Numerical Simulation on Heat Transfer Performance of Coaxial Borehole Heat Exchanger

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5471
Author(s):  
Peng Li ◽  
Peng Guan ◽  
Jun Zheng ◽  
Bin Dou ◽  
Hong Tian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Heat Exchanger ◽  
Flow Rate ◽  
Thermal Response ◽  
Heat Pumps ◽  
Inlet Temperature ◽  
Borehole Heat Exchanger ◽  
Ground Source Heat Pumps ◽  
Ground Source

Ground thermal properties are the design basis of ground source heat pumps (GSHP). However, effective ground thermal properties cannot be obtained through the traditional thermal response test (TRT) method when it is used in the coaxial borehole heat exchanger (CBHE). In this paper, an improved TRT (ITRT) method for CBHE is proposed, and the field ITRT, based on the actual project, is carried out. The high accuracy of the new method is verified by laboratory experiments. Based on the results of the ITRT and laboratory experiment, the 3D numerical model for CBHE is established, in which the flow directions, sensitivity analysis of heat transfer characteristics, and optimization of circulation flow rate are studied, respectively. The results show that CBHE should adopt the anulus-in direction under the cooling condition, and the center-in direction under the heating condition. The influence of inlet temperature and flow rate on heat transfer rate is more significant than that of the backfill grout material, thermal conductivity of the inner pipe, and borehole depth. The circulating flow rate of CBHE between 0.3 m/s and 0.4 m/s can lead to better performance for the system.

Application of Artificial Neural Networks to Predict Heat Transfer From Buried Pipe for Ground Source Heat Pump Applications

2013 ◽  
Author(s):  
Hakan Demir ◽  
Ş. Özgür Atayılmaz ◽  
Özden Agra ◽  
Ahmet Selim Dalkılıç
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Energy Resource ◽  
Heat Pumps ◽  
Burial Depth ◽  
Buried Pipe ◽  
Ground Source Heat Pumps ◽  
Ground Source ◽  
Artificial Neural

The earth is an energy resource which has more suitable and stable temperatures than air. Ground Source Heat Pumps (GSHPs) were developed to use ground energy for residential heating. The most important part of a GSHP is the Ground Heat Exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the GSHP. Soil composition, density, moisture and burial depth of pipes affect the size of a GHE. Design of GSHP systems in different regions of US and Europe is performed using data from an experimental model. However, there are many more techniques including some complex calculations for sizing GHEs. An experimental study was carried out to investigate heat transfer in soil. A three-layer network is used for predicting heat transfer from a buried pipe. Measured fluid inlet temperatures were used in the artificial neural network model and the fluid outlet temperatures were obtained. The number of the neurons in the hidden layer was determined by a trial and error process together with cross-validation of the experimental data taken from literature evaluating the performance of the network and standard sensitivity analysis. Also, the results of the trained network were compared with the numerical study.

Heat Transfer in a Radially Rotating Four-Pass Serpentine Channel With Staggered Half-V Rib Turbulators

2000 ◽  
Vol 123 (1) ◽  
pp. 39-50 ◽  
Author(s):  
G. J. Hwang ◽  
S. C. Tzeng ◽  
C. P. Mao ◽  
C. Y. Soong
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Enhancement ◽  
Serpentine Channel ◽  
Ribbed Channel ◽  
Flow Parameters ◽  
Rib Turbulators ◽  
Rib Arrangement

The present work is concerned with experimental investigation of the convective heat transfer in a radially rotating four-pass serpentine channel. Two types of staggered half-V rib turbulators are considered to examine their effects on heat transfer enhancement. The coolant air is pressurized and pre-cooled to compensate for the low rotating rate and low temperature or density difference in key parameters of thermal and flow characteristics. The geometric dimensions are fixed, whereas the ranges of the thermal and flow parameters in the present measurements are 20,000⩽Re⩽40,000,0⩽Ro⩽0.21, and Gr/Re2∼O10−2. The present results disclose the effects of the pressurized flow, rib arrangement, channel rotation, and centrifugal buoyancy on the local heat transfer in each passage of the channel. Finally, the present data are fitted on correlation equations for evaluation of local heat transfer in the rotating four-pass ribbed channel configurations considered.

A Study of Condensation Heat Transfer in a Single Mini-Tube and a Review of Korean Micro- and Mini-Channel Studies

2003 ◽  
Author(s):  
M. H. Kim ◽  
J. S. Shin ◽  
C. Huh ◽  
T. J. Kim ◽  
K. W. Seo
Keyword(s):  
Heat Transfer ◽  
Flow Boiling ◽  
Flow Characteristics ◽  
Saturation Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Round Tube ◽  
Two Phase

This paper reviews recent Korean studies of flow characteristics, flow boiling, and flow condensation in micro- and mini-channels. The characteristics of local heat transfer and pressure drops were experimentally investigated using condensing R134a two-phase flow, in a single round tube, with an inner diameter of 0.691 mm. New experimental techniques were developed to measure the condensation heat transfer coefficient. Tests were performed for a mass flux of 100 to 600 kg/m2s, a heat flux of 5 to 20 kW/m2, and a saturation temperature of 40°C. The experimental local condensation heat transfer coefficients and two-phase frictional pressure gradients are shown. Comparisons of experimental data with existing models reveal that the correlations failed to predict the present data. This study contains the unique sub-millimeter-diameter, single round tube, condensation data reported in the literature.

Natural Convection in Vertically Vented Enclosures

1991 ◽  
Vol 113 (4) ◽  
pp. 912-918 ◽  
Author(s):  
D. M. Sefcik ◽  
B. W. Webb ◽  
H. S. Heaton
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Visualization ◽  
Flow Structure ◽  
Control Volume ◽  
Local Maximum ◽  
Separated Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heated Wall

Steady, laminar natural convection in vertically vented two-dimensional enclosures has been investigated both experimentally and analytically. A vertically vented enclosure is one in which the buoyancy-driven flow and heat transfer are restricted by vents in the top and bottom bounding walls of the enclosure. The local heat transfer along the heated wall was determined using Mach-Zehnder interferometry, and the flow structure was determined using a smoke generation flow visualization technique. Analytically, the governing conservation equations were solved numerically using a control volume-based finite difference technique. The results reveal strongly nonuniform local heat transfer along the isothermal wall as a result of the blockage at the inlet. A local maximum and minimum occur in the lower half of the enclosure. The flow visualization and analytical predictions for the flow field reveal that these heat transfer extrema are attributed to separated flow effects near the inlet gap with the associated primary inlet flow impingement and bifurcation at the heated wall. The analysis predicts well the flow structure and local and average heat transfer data. The results show asymptotic behavior to the classical vertical parallel plate result in the limit as the vent gap approaches the enclosure width.

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