Experimental Research on the Flow Resistance and Heat Transfer Characteristics in Rod Bundle Channel

2018 ◽  
Author(s):  
Zhiqiang Zhu ◽  
Chunping Tian ◽  
Changqi Yan ◽  
Jianjun Wang ◽  
Tingting Ren ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Resistance ◽  
Single Phase ◽  
Natural Circulation ◽  
Resistance Coefficient ◽  
Flow Transition ◽  
Heat Transfer Characteristics ◽  
Rod Bundle ◽  
Local Resistance Coefficient

Single-phase natural circulation experiments were conducted to study the flow resistance and heat transfer characteristics in a 3 × 3 rod bundle channel with the ratio of rod pitch and rod outer diameter (P/D) 1.38. The range of inlet subcooling degree is 30∼90K and the heating power is 1∼20kW. The rods are heated with constant heat flux. According to the experimental results, the flow regime under natural circulation condition is divided and the transition Reynolds number is considered as 800. The flow transition is recognized by the slope change of friction factor curve since the flow transition in the rod bundle channel is not as obvious as that in round pipe. Simultaneously, the flow transition in the rod bundle is much earlier and the upper critical Reynolds number is much larger compared to regular channel like round pipe and rectangular channel. Two correlations for laminar and transition regime are fitted to calculate the friction factor. As for the grid spacer local resistance coefficient, there is slight change at Reynolds number 800 and similarly two correlations are fitted to calculate the local resistance coefficient. The Nusselt number tendency changes at around Reynolds number 4000 but keep unchanged at transition point, which means the flow transition has no obvious effect to the heat transfer. The heat transfer results are compared with different single-phase convective heat transfer correlations. D-B and Gnielinski correlations are not suitable for the heat transfer prediction in rod bundle channel and the relative deviation is more than 20%. Weisman, Presser and Markoczy correlations predict relatively well in high Reynolds number region, and Markoczy correlation is the best of them. In low Reynolds number region, most experimental results are larger than the correlations. D-B correlation based methods may be unsuitable for the heat transfer prediction in rod bundle channel and a new correlation needs to be proposed.

Local Single-Phase Heat Transfer Research of Natural Circulation in Narrow Rectangular Channel

2017 ◽  
Author(s):  
Zhiqiang Zhu ◽  
Xiaxin Cao ◽  
Changqi Yan ◽  
Chunping Tian
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Inclination Angle ◽  
Local Nusselt Number ◽  
Single Phase ◽  
Natural Circulation ◽  
Rectangular Channel ◽  
Inlet Temperature

In order to explore and analyze the heat transfer characteristics in narrow rectangular channel, experiments on local single-phase heat transfer of natural circulation in a one-side heating narrow rectangular channel have been conducted under vertical and inclined condition. The thermotechnical parameters such as inlet temperature, heat flux and inclination angle varies during the experiments. The width of the flow channel is 40 mm and the narrow gap is 2 mm. It is heated from one side with a homogeneous and constant heat flux and the working medium is deionized water. Based on the experimental results, under vertical condition, the driving force in the loop goes up and the Reynolds number also increases when the inlet temperature is elevated, which causes an increase in local Nusselt number. When the heat flux rises, the local Nusselt number increases and the heat transfer temperature difference increases. The local Nusselts number is influenced by entrance effect and the entrance region length is computed for laminar and turbulent flow. Under inclined condition, with the inclination angle from −30° to 30°, it is found that when the inclination angle is positive, the local Nusselt number in fully developed region is larger than that under vertical condition and increases with the angle value, even though the Reynolds number decreases by the effect of incline. This phenomenon is explained by giving an analysis of the natural convection, which is characterized by the normal Grashof number, in the direction perpendicular to the heating plat. Moreover, the variation of heat transfer is also interpreted on the basis of field coordination principle. However, when the inclination angle is negative, the heat transfer shows no obvious difference between vertical condition and inclined condition.

Heat Transfer Augmentation in 3D Inner Finned Helical Tube

Volume 3 ◽  
2004 ◽  
Author(s):  
Longjian Li ◽  
Wenzhi Cui ◽  
Quan Liao ◽  
Mingdao Xin ◽  
Tien-Chien Jen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Boiling Heat Transfer ◽  
Flow Resistance ◽  
Single Phase ◽  
Flow Boiling ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Helical Tube ◽  
Helical Tubes

Experiments were performed to investigate the performance enhancement of single-phase flow and boiling heat transfer in the 3D inner finned helical tubes. The tests for single-phase flow and heat transfer were carried out in the helical tubes with a curvature of 0.0663 and a length of 1.15m, the range of the Reynolds number examined varies from 1000 to 8500. In comparison to the smooth helical tube, the experimental results of two finned helical tubes with different inner fin geometry showed that the heat transfer and flow resistance in the 3D inner finned helical tube gains greater augmentation. Within the measured range of Reynolds number, the average augmentation ratio of heat transfer of the two finned tubes are 71% and 103%, compared with the smooth helical tube, and 90% and 140% for flow resistance, respectively. The tests for flow boiling heat transfer was carried out in the 3D inner finned helical tube with a curvature of 0.0605 and a length of 0.668m. Compared with that in the smooth helical tube, the boiling heat transfer coefficient in the 3D inner finned helical tube is increased by 40%∼120% under varied mass flow rate and wall heat flux conditions, meanwhile, the flow resistance coefficient increased by 18%∼119%.

Experimental Investigation of Flow and Heat Transfer Characteristics of Latent Functionally Thermal Fluid in Mini-Tube

2009 ◽  
Author(s):  
Jinli Lu ◽  
Yingli Hao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Single Phase ◽  
Deionized Water ◽  
Working Fluid ◽  
Experimental Measurements ◽  
Heat Transfer Characteristics ◽  
Latent Functionally Thermal Fluid ◽  
Flow And Heat Transfer ◽  
Phase Water

An experimental research using the latent functionally thermal fluid of n-hexadecane microcapsules in deionized water was conducted in order to investigate the flow and heat transfer characteristics of microencapsulated phase change material (MEPCM) slurry. Experimental measurements were done for a large region of Reynolds number in the mini-tube with a constant wall heat flux. Experimental measurements were also conducted using deionized water as the working fluid under the same conditions. Some important parameters such as pressure, temperatures of wall and fluid were obtained experimentally. The relationships between pressure drop and mass flow rate, dimensionless outlet temperature of working fluid and Reynolds number, mean convective heat transfer coefficient and Nusselt number and Reynolds number were obtained. Results show that the using of MEPCM particle increases the pressure drop and then close to that of single phase water with increasing mass flow rate. The outlet and wall temperatures decrease 50% comparing with single phase water under the same conditions. The Nusselt number of slurry containing small concentration MEPCM particle is about 2.0–2.3 times greater than that of single phase water in the minitube. The experimental data might be helpful in the design of thermal-energy transportation systems in small scale using MEPCM slurry.

Single-Phase Heat Transfer and Fluid Flow in Micropipes

2003 ◽  
Author(s):  
Gian Piero Celata
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Transfer Rate ◽  
Single Phase ◽  
Flow Transition ◽  
Laminar And Turbulent Regimes ◽  
Good Agreement

The objective of the present paper is to provide a general overview of the research carried out so far in single-phase heat transfer and flow in capillary (micro) pipes. Laminar flow and laminar-to-turbulent flow transition are analyzed in detail in order to clarify the discrepancies among the results obtained by different researchers. Experiments performed in the ENEA laboratory indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 600–800. For higher values of Reynolds number, experimental data depart from the Hagen-Poiseuille law to the side of higher f values. The transition from laminar-to-turbulent flow occurs for Reynolds number in the range 1800–2500. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional (macro) tubes, are not properly adequate for heat transfer rate prediction in microtubes.

scholarly journals Time Averaged and Fluctuating Heat Transfer Measurements in an Atomising Mist Jet Nozzle

2009 ◽  
Author(s):  
Oisn F. P. Lyons ◽  
Darina B. Murray ◽  
Gerard Byrne ◽  
Tim Persoons
Keyword(s):  
Heat Transfer ◽  
Internal Structure ◽  
Research Group ◽  
Single Phase ◽  
Water Mist ◽  
Phase Behaviour ◽  
Heat Transfer Characteristics ◽  
Air Jets ◽  
Mist Flow ◽  
Jet Nozzle

Much is already known about the heat transfer characteristics of impinging air jets, and they are widely used in many engineering applications. There currently exist many correlations describing such characteristics. However, the complex internal structure of many nozzles can lead these to produce results which deviate from those predicted by correlations. One such nozzle is currently used in this research group to produce a water mist flow and this paper describes the experimental characteristics of its single phase behaviour.

Numerical Simulation on Heat Transfer Characteristics of Turbulent Gas Flow in Micro-Tubes

2011 ◽  
Author(s):  
Kyohei Isobe ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Ichiro Ueno
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Wall Temperature ◽  
Gas Flow ◽  
Tube Diameter ◽  
Turbulence Energy ◽  
Stagnation Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Turbulent Gas Flow

Numerical simulations were performed to obtain for heat transfer characteristics of turbulent gas flow in micro-tubes with constant wall temperature. The numerical methodology was based on Arbitrary-Lagrangian-Eulerinan (ALE) method to solve compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was employed to evaluate eddy viscosity coefficient and turbulence energy. The tube diameter ranges from 100 μm to 400 μm and the aspect ratio of the tube diameter and the length is fixed at 200. The stagnation temperature is fixed at 300 K and the computations were done for wall temperature, which ranges from 305 K to 350 K. The stagnation pressure was chosen in such a way that the flow is in turbulent flow regime. The obtained Reynolds number ranges widely up to 10081 and the Mach number at the outlet ranges from 0.1 to 0.9. The heat transfer rates obtained by the present study are higher than those of the incompressible flow. This is due to the additional heat transfer near the micro-tube outlet caused by the energy conversion into kinetic energy.

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