scholarly journals Experimental Approach on a Swirl Flow and Heat Transfer Coefficient Using a 3-D Stereo-PIV and Liquid Crystals

2018 ◽  
Author(s):  
Daisy Galeana ◽  
Asfaw Beyene
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystals ◽  
Transfer Coefficient ◽  
Experimental Approach ◽  
Swirl Flow ◽  
Flow And Heat Transfer

Flow and Heat Transfer of Supercritical Co2 in a Vertical Tube Under Ocean Rolling Motion

2021 ◽  
Author(s):  
Dechao Liu ◽  
Shulei Li ◽  
Gongnan Xie ◽  
Youqian Chen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Waste Heat ◽  
Static Condition ◽  
Vertical Tube ◽  
Rolling Motion ◽  
Flow And Heat Transfer ◽  
Maximum Improvement

Abstract In order to explore the fluid flow and heat transfer features of supercritical fluids used in Brayton cycle for waste-heat utilization of marine gas turbines, the effects of ocean rolling motion on thermo-fluidic characteristics of supercritical carbon dioxide (SCO2) in a circular tube are computationally investigated based on a verified turbulence model. It can be found that at a given rolling period, compared to that under static condition, the time-averaged heat transfer capacity is improved by 7.9%, but the onset of the heat transfer recovery is delayed so that the range of the heat transfer deterioration becomes widened. Under the action of the inertial forces, the heat exchange between cooler/denser and warmer/lighter fluids is enhanced, a secondary circulation formed at t/tc = 0.325 and the maximum improvement of section-averaged heat transfer coefficient is 71% at this time. For various periods, the variation trend of time-averaged heat transfer coefficient for SCO2 shows a parabolic, which is distinguishing from conventional fluids. A polarization phenomenon for instantaneous thermal performance can be observed under severe rolling. With rise of the layout height, the time-average heat transfer performance of tube increases monotonously, and the maximum increment is 10.64% in study range.

Fluid Flow and Heat Transfer Analysis of Automotive Radiator Using CFD Tools

2005 ◽  
Author(s):  
V. P. Malapure ◽  
A. Bhattacharya ◽  
Sushanta K. Mitra
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Temperature Drop ◽  
Three Dimensional ◽  
Heat Transfer Analysis ◽  
Coolant Temperature ◽  
Flow And Heat Transfer ◽  
Optimization Study

This paper presents a three-dimensional numerical analysis of flow and heat transfer over plate fins in a compact heat exchanger used as a radiator in the automotive industry. The aim of this study is to predict the heat transfer and pressure drop in the radiator. FLUENT 6.1 is used for simulation. Several cases are simulated in order to investigate the coolant temperature drop, heat transfer coefficient for the coolant and the air side along with the corresponding pressure drop. It is observed that the heat transfer and pressure drop fairly agree with experimental data. It is also found that the fin temperature depends on the frontal air velocity and the coolant side heat transfer coefficient is in good agreement with classical Dittus–Boelter correlation. It is also found that the specific dissipation increases with the coolant and the air flow rates. This work can further be extended to perform optimization study for radiator design.

Influence of Surface Roughness on Heat Transfer and Effectiveness for a Fully Film Cooled Nozzle Guide Vane Measured by Wide Band Liquid Crystals and Direct Heat Flux Gages

2000 ◽  
Vol 122 (4) ◽  
pp. 709-716 ◽  
Author(s):  
S. M. Guo ◽  
C. C. Lai ◽  
T. V. Jones ◽  
M. L. G. Oldfield ◽  
G. D. Lock ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Transfer Coefficient ◽  
Rough Surface ◽  
Guide Vane ◽  
Wide Band ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The influence of surface roughness on heat transfer coefficient and cooling effectiveness for a fully film cooled three-dimensional nozzle guide vane (NGV) has been measured in a transonic annular cascade using wide band liquid crystal and direct heat flux gages (DHFGs). The liquid crystal methods were used for rough surface measurements and the DHFGs were used for the smooth surfaces. The measurements have been made at engine representative Mach and Reynolds numbers and inlet free-stream turbulence intensity. The aerodynamic and thermodynamic characteristics of the coolant flow have been modeled to represent engine conditions by using a heavy “foreign gas” (30.2 percent SF6 and 69.8 percent Ar by weight). Two cooling geometries (cylindrical and fan-shaped holes) have been tested. The strategies of obtaining accurate heat transfer data using a variety of transient heat transfer measurement techniques under the extreme conditions of transonic flow and high heat transfer coefficient are presented. The surfaces of interest are coated with wide-band thermochromic liquid crystals, which cover the range of NGV surface temperature variation encountered in the test. The liquid crystal has a natural peak-to-peak roughness height of 25 μm creating a transitionally rough surface on the NGV. The time variation of color is processed to give distributions of both heat transfer coefficient and film cooling effectiveness over the NGV surface. The NGV was first instrumented with the DHFGs and smooth surface tests preformed. Subsequently the surface was coated with liquid crystals for the rough surface tests. The DHFGs were then employed as the means of calibrating the liquid crystal layer. The roughness of 25 μm, which is the typical order of roughness for the in-service turbine blades and vanes, increases the heat transfer coefficient by up to 50 percent over the smooth surface level. The film cooling effectiveness is influenced less by the roughness. [S0889-504X(00)00804-7]

Numerical and experimental analysis of microchannel heat transfer for nanoliquid coolant using different shapes and geometries

2014 ◽  
Vol 229 (11) ◽  
pp. 2056-2065 ◽  
Author(s):  
Harry Garg ◽  
Vipender Singh Negi ◽  
Nidhi Garg ◽  
AK Lall
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Transfer Coefficient ◽  
Experimental Analysis ◽  
High Heat ◽  
Heat Transfer Analysis ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
High Heat Transfer Coefficient

As part of the liquid cooling, most of the work has been done on fluid flow and heat transfer analysis for flow field. In the present work, the experimental and numerical studies of the microchannel the fluid flow and heat transfer analysis using nanoliquid coolant have been discussed. The practical aspects for increasing the high heat transfer coefficient from conventional studies and the different geometries and shapes of the microchannel are studied. The Aspect Ratio has significant effect on the microchannels and has been varied from AR 2, 4 and 8 to choose the optimum one. Three different fluids, i.e. de-ionized water, ethylene glycol, and a custom nanofluid are chosen for study. The proposed nanofluid almost interacts as another solid and has reduced thermal resistance, friction effect, and thus it almost vanishes high hot spots. Experimental analysis shows that the proposed nanofluid is excellent fluid for high rate heat removals. Moreover, the performance of the overall system is excellent in terms of high heat transfer coefficient, high thermal conductivity, and high capacity of the fluid. It has been reported that the heat transfer coefficient can be increased to 2.5 times of the water or any other fluid. It was also reported that the AR 4 rectangular-shaped channels are the optimum geometry in the Reynolds number ranging from 50 to 800 considering laminar flow. Examination and identification is based upon the practical result that includes fabrication constraints, commercial application, sealing of the system, ease of operation, and so on.

Blade Tip Leakage Flow and Heat Transfer With Pressure-Side Winglet

2003 ◽  
Author(s):  
Arun K. Saha ◽  
Sumanta Acharya ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Leakage Flow ◽  
Pressure Side ◽  
Average Heat Transfer Coefficient ◽  
Tip Leakage Flow ◽  
Average Heat ◽  
Flow And Heat Transfer ◽  
Blade Tip

A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure side winglet exhibits a significant reduction in the leakage flow strength and an associated reduction in the aerodynamic loss. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. The winglet reduces the average heat transfer coefficient by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and only a 0.5% reduction in the pressure ratio is achieved with the winglet with virtually no reduction in the average heat transfer coefficient.

3D Numerical Simulation of Fluid Flow and Heat Transfer in Tube with Spiral-Flange Insert

2011 ◽  
Vol 236-238 ◽  
pp. 1508-1515
Author(s):  
Qun Song Li ◽  
Qian Yang ◽  
Zhi Song Li ◽  
Tian Lan Yu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Transfer Coefficient ◽  
Turbulence Intensity ◽  
Convective Heat Transfer Coefficient ◽  
3D Numerical Simulation ◽  
Flow And Heat Transfer ◽  
Smooth Tubes

With the help of Fluent 6.2 and supporting software, 3D numerical simulation of fluid flow and heat transfer enhancement of plastic spiral tubes were performed on computer, and the velocity, turbulence intensity and improvement of convective heat transfer coefficient distribution in plastic spiral tubes were analyzed and compared with those in smooth tubes, and characteristics of fluid flow and heat transfer were obtained. The results showed that there were obvious axial, tangential and radial velocities in spiral space, and they were bigger than those in smooth tubes. The turbulence intensity was also increased greatly because of the existence of spiral channels. The dirt production was prevented and the tube's convection heat transfer was effectively strengthened. Its surface average heat transfer coefficient had been enhanced by about 20% compared with the smooth tubes; The pressure drop caused by plastic spiral flange was in the permissible range of engineering application. It was suitable for the heat exchanger at a flow velocity lower than 0.8m/s.

A new experimental approach for heat transfer coefficient and adiabatic wall temperature measurements on a Nozzle Guide Vane with inlet temperature distortions

2021 ◽  
pp. 1-33
Author(s):  
Tommaso Bacci ◽  
Alessio Picchi ◽  
Bruno Facchini ◽  
Simone Cubeda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Gas Turbines ◽  
Experimental Approach ◽  
Guide Vane ◽  
Adiabatic Wall ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Abstract Modern gas turbines lean combustors are used to limit NOx pollutant emissions; on the other hand, their adoption presents other challenges, especially concerning the combustor-turbine interaction. Turbine inlet conditions are generally characterized by severe temperature distortions and swirl degree, which is responsible for very high turbulence intensities. Past studies have focused on the description of the effects of these phenomena on the behavior of the high pressure turbine. Nevertheless, very limited experimental results are available when it comes to evaluate the heat transfer coefficient (HTC) on the nozzle guide vane surface, since relevant temperature distortions present a severe challenge for the commonly adopted measurement techniques. The work presented in this paper was carried out on a non-reactive, annular, three-sector rig, made by a combustor simulator and a NGV cascade. It can reproduce a swirling flow, with temperature distortions at the combustor-turbine interface plane. This test apparatus was exploited to develop an experimental approach to retrieve heat transfer coefficient and adiabatic wall temperature distributions simultaneously, to overcome the known limitations imposed by temperature gradients on state-of-the-art methods for HTC calculation from transient tests. A non-cooled mockup of a NGV doublet, manufactured using low thermal diffusivity plastic material, was used for the tests, carried out using IR thermography with a transient approach. In the authors' knowledge, this presents the first experimental attempt of measuring a nozzle guide vane heat transfer coefficient in the presence of relevant temperature distortions and swirl.

A New Experimental Approach for Heat Transfer Coefficient and Adiabatic Wall Temperature Measurements on a Nozzle Guide Vane With Inlet Temperature Distortions

2021 ◽  
Author(s):  
T. Bacci ◽  
A. Picchi ◽  
B. Facchini ◽  
S. Cubeda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Experimental Approach ◽  
Guide Vane ◽  
Adiabatic Wall ◽  
Turbine Inlet ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Abstract Modern gas turbines lean combustors allow to limit NOx pollutant emissions by controlling the flame temperature, while maintaining high turbine inlet temperatures. On the other hand, their adoption presents other challenges, especially concerning the combustor-turbine interaction. Turbine inlet conditions are generally characterized by severe temperature distortions and swirl degree, which, in turn, is responsible for very high turbulence intensities. Several past studies have focused on the description of the effects of these phenomena on the behavior of the high pressure stages of the turbine, both considering them as separated aspects, and, in very recent years, accounting for their combined impact. Nevertheless, very limited experimental results are available when it comes to evaluate the heat transfer coefficient (HTC) on the nozzle guide vane external surface, since relevant temperature distortions present a severe challenge for the commonly adopted measurement techniques. The work presented in this paper was carried out on a non-reactive, annular, three-sector test rig, made by a combustor simulator and a NGV cascade. Making use of three real hardware burners of a Baker Hughes heavy-duty gas turbine, operated in similitude conditions, it can reproduce a representative swirling flow, with temperature distortions at the combustor-turbine interface plane. This test apparatus was exploited to develop an experimental approach to retrieve reliable heat transfer coefficient and adiabatic wall temperature distributions simultaneously, in order to overcome the known limitations imposed by temperature gradients on state-of-the-art methods for HTC calculation from transient tests. A non-cooled mockup of a NGV doublet, manufactured using low thermal diffusivity plastic material, was used for the tests, carried out using IR thermography with a transient approach. In the authors’ knowledge, this presents the first experimental attempt of measuring a nozzle guide vane heat transfer coefficient in the presence of relevant temperature distortions and swirl.

Shell Side Flow and Heat Transfer Performances of Trisection Helical Baffle Heat Exchangers

2013 ◽  
Author(s):  
Yaping Chen ◽  
Cong Dong ◽  
Jiafeng Wu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Incline Angle ◽  
Shell Side ◽  
Single Vortex ◽  
Flow And Heat Transfer ◽  
Helical Baffle ◽  
Side Flow

The flow and heat transfer performances of three trisection helical baffle heat exchangers with different baffle shapes and assembly configurations, and a continuous helical baffle scheme with approximate spiral pitch were numerically simulated. The four schemes are two trisection helical baffle schemes of baffle incline angle of 20° with a circumferential overlap baffle scheme (20°TCO) and a end-to-end helical baffle scheme (20°TEE), a trisection mid-overlap helical baffle scheme with baffle incline angle of 36.2° (36.2°TMO), and a continuous helical baffle scheme with baffle helix angle of 16.8° (18.4°CH). The pressure or velocity nephograms with superimposed velocity vectors for meridian slice M1, transverse slices f and f1, and unfolded concentric hexagonal slices H2 and H3 are presented. The Dean vortex secondary flow field, which is one of the key mechanisms of enhancing heat transfer in heat exchangers, is clearly depicted showing a single vortex is formed in each baffle pitch cycle. The leakage patterns are demonstrated clearly on the unfolded concentric hexagonal slices. The results show that the 20°TCO and 18.4°CH schemes rank the first and second in shell-side heat transfer coefficient and comprehensive indexes ho/Δpo and ho/Δpo1/3. The 20°TEE scheme without circumferential overlap is considerably inferior to the 20°TCO scheme. The 36.2°TMO scheme is the worst in both shell-side heat transfer coefficient and comprehensive index ho/Δpo1/3.

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