scholarly journals Numerical analysis of heat transfer enhancement in pulsating flow pipes

2021 ◽  
Vol 2133 (1) ◽  
pp. 012034
Author(s):  
Jianfeng En ◽  
Ziyao Ma ◽  
Siran Jia ◽  
Jie Mu ◽  
Zhenbang Gao
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
The Finite Element Method ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Exchange Effect ◽  
Transfer Characteristics ◽  
Smooth Flow ◽  
Accumulation Effect ◽  
Effect Of Impurities

Abstract In this paper, a rectangular flow runner is used as the research object to study the influence of adding a spoiler on the wall of the flow runner on its heat transfer characteristics and flow characteristics. Using the finite element method to analyse the influence of different spoiler’s structures and parameters of the spoilers on the heat transfer characteristics and flow characteristics of the flow runner, the study found that: by the comparison of the smooth flow runner and the rectangular spoiler flow runner, the comprehensive heat exchange effect of the spoiler runner is the best when the arc is arranged in the flow runner, and the accumulation effect of impurities in the runner is the slowest.

scholarly journals Heat transfer and flow region characteristics study in a non-annular channel between rotor and stator

2012 ◽  
Vol 16 (2) ◽  
pp. 593-603 ◽  
Author(s):  
M. Nili-Ahmadabadi ◽  
H. Karrabi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Characteristics ◽  
Annular Channel ◽  
Flow Region ◽  
Air Gap ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Slip Ring

This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000<Rez<30000. Heat transfer and pressure drop coefficients are deduced from the obtained data based on a theoretical investigation and are expressed as a formula containing effective Reynolds number. To confirm the results, a comparison is presented with Gazley?s (1985) data report. The presented method and established correlations can be applied to other electric machines having similar heat flow characteristics.

Experimental Study of Flow and Heat Transfer Characteristics in Silicon-Based Corrugated Microchannels

2009 ◽  
Author(s):  
Huimin Tang ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
High Efficiency ◽  
Cooling System ◽  
Width Ratio ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Total Thermal Resistance ◽  
Transfer Characteristics ◽  
Silicon Based

In this paper, the silicon-based corrugated microchannels used for the heat transfer enhancement were fabricated by MEMS technology for the first time. Both the flow and convective heat transfer characteristics of the deionized water through these corrugated microchannels were investigated experimentally, and comparisons were performed between corrugated microchannels and straight microchannels with the same cross-sectional aspect ratio (height-to-width ratio) and same hydraulic diameter. Experimental results showed that both the flow friction and Nusselt number in corrugated microchannels increased considerably compared with those in straight microchannels, and this increase became enlarged with the increase in the Reynolds number. With the same pumping power, using corrugated microchannels instead of straight microchannels caused the reduction in the total thermal resistance. The heat transfer enhancement mechanism of the corrugated microchannels was discussed. The results presented in this paper help to design the high efficiency integrated chip cooling system.

Flow and Heat Transfer Characteristics in Channels With Groove–Protrusions and Combination Effect With Ribs

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Lu Zheng ◽  
Yonghui Xie ◽  
Di Zhang ◽  
Haoning Shi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Leading Edge ◽  
Small Scale ◽  
Combination Effect ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Passive flow control and heat transfer enhancement technique has become an attractive method for device internal cooling with low resistance penalty. In the present paper, the flow and heat transfer characteristics in the small scale rectangular channel with different groove–protrusions are investigated numerically. Furthermore, the combination effect with ribs is studied. The numerical results show that on the groove side, the flow separation mainly occurs at the leading edge, and the reattachment mainly occurs at the trailing edge in accordance with the local Nusselt number distribution. On the protrusion side, the separation mainly occurs at the protrusion back porch and enhances the heat transfer at the leading edge of the downstream adjacent groove. The rectangle case provides the highest dimensionless heat transfer enhancement coefficient Nu/Nu0, dimensionless resistance coefficient f/f0, and thermal performance (TP) with the highest sensitivity of Re. When ribs are employed, the separation bubble sizes prominently decrease, especially inside the second and third grooves. The Nu/Nu0 values significantly increase when ribs are arranged, and the one-row case provides the highest heat transfer enhancement by ribs. Besides, the two-row case provides the highest Nu/Nu0 value without ribs, and the three-row case shows the lowest Nu/Nu0 value whether ribs are arranged or not.

Laminar Flow and Heat Transfer Characteristics of Colloid Suspensions in Water: A Numerical Study

2009 ◽  
Author(s):  
Khalid N. Alammar ◽  
Lin-wen Hu
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Flow Rate ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Numerical analysis is performed to examine axisymmetric laminar flow and heat transfer characteristics of colloidal dispersions of nanoparticles in water (nanofluids). Effect of volume fraction on flow and heat transfer characteristics is investigated. Four different materials, Alumina, Copper, Copper Oxide, and Graphite are considered. Heat transfer and property measurements were conducted previously for Alumina nanofluid. The measurements have shown that nanofluids can behave as homogeneous mixtures. It is found that oxide-based nanofluids offer the least heat transfer enhancement compared to elements-based nanofluids. When normalized by friction pressure drop, it is shown that graphite can have the highest effective heat transfer enhancement. For a given volume flow rate, all nanofluids exhibited linear increase in heat transfer enhancement with increasing colloids volume fraction, up to 0.05.

A Parametric Experimental Study on the Heat Transfer Characteristics of Supercritical Kerosene in Active Cooling Channels of Scramjets

2013 ◽  
Vol 774-776 ◽  
pp. 252-257
Author(s):  
Ning Wang ◽  
Jin Zhou ◽  
Yu Pan ◽  
Hui Wang
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Sharp Increase ◽  
Film Boiling ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Heat Transfer Deterioration ◽  
Cooling Channels ◽  
Transfer Characteristics ◽  
The Heat Transfer Coefficient

Heat transfer characteristics of China RP-3 kerosene under supercritical state were experimentally investigated. Results showed that at sub-critical pressures, heat transfer deterioration happens, and the wall temperature rises from approximately 350°C to 750°C. This is thought to be resulted from film boiling when kerosene begins to transfer from liquid to gas. At supercritical pressures, heat transfer enhancement was observed. And it is mainly caused by the sharp increase of specific heat of kerosene when the wall temperature is approaching the critical temperature of kerosene. The heat transfer coefficient doesnt increase with velocity for kerosene, because the thermal properties and residence time of kerosene have changed when velocity is changed.

Numerical Study on the Flow and Heat Transfer Characteristics in Rectangular Channels With Grooves and Different Protrusions

2017 ◽  
Author(s):  
Feng Zhang ◽  
Xinjun Wang ◽  
Jun Li ◽  
Daren Zheng ◽  
Junfei Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rectangular Channels

The present work represents a numerical study on the flow and heat transfer characteristics in rectangular channels with protrusion-grooved turbulators. The Reynolds averaged Navier-Stokes equations, coupled with SST turbulence model, are adopted and solved. In this paper, six geometric protrusion shapes (circular, rectangular, triangular, trapezoidal, circular with leading round concave and circular with trailing round concave) are selected to perform the study. The flow structure, heat transfer enhancement, friction factor as well as thermal performance factor of the rectangular channel fitted with combined groove and different protrusions have been obtained at the Reynolds number ranging from 5000 to 20000. The results indicate that the protrusion shapes affect the velocity distribution near the groove surface. The case of circular protrusion with leading round concave provides the highest overall heat transfer enhancement, while it also causes the highest pressure loss penalty. The case of rectangular protrusion has the lowest overall heat transfer enhancement with high pressure loss penalty. The case of circular protrusion has similar overall heat transfer enhancement with cases of trapezoidal protrusion as well as circular protrusion with trailing round concave, but the pressure loss penalty of the case of circular protrusion is the lowest. In addition, the best overall thermal performance can be observed for circular protrusion-grooved channel.

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