scholarly journals Development of Heat Transfer Surface Area Enhancements: A Test Facility for New Heat Exchanger Designs

Energies ◽  
2018 ◽  
Vol 11 (5) ◽  
pp. 1322 ◽  
Author(s):  
Hannes Fugmann ◽  
Paolo Di Lauro ◽  
Aniket Sawant ◽  
Lena Schnabel
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Surface Area ◽  
Performance Testing ◽  
Heat Transfer Surface ◽  
Test Facility ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pin Fins ◽  
Louvered Fins

Enhancing the heat transfer surface by usage of cellular metal structures, such as foams or wire structures, might allow enlarging the surface area, increasing the heat transfer coefficients, decreasing the material utilization, and enabling the flexibility of different geometrical dimensions. However their manufacturing and assembling in a large heat exchanger for performance testing and optimizing can be costly. Therefore a test rig was constructed for experimental characterization of heat transfer surface area enhancements. Heat exchanger samples with dimensions in the centimeter range can be measured. The fluid flow and heat transfer features of a micro pin fin wire structure made from copper by soft-soldering were experimentally characterized under steady-state forced air convection. The results are compared to performance characteristics of louvered fins. Heat transfer coefficients of the pin fins are twice as high as for the louvered fins. The relative expanded uncertainty of the Nusselt number is ±7%.

A Novel Concept to Improve the Performance of LED Panel Using Drilled Holes

2005 ◽  
Author(s):  
S. B. Chiang ◽  
C. C. Wang
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Heat Sink ◽  
Maximum Temperature ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Pin Fins ◽  
Overall Performance ◽  
Novel Concept

In this study, the concept of the thermal module of LEDs cooling by use of drilled hole to entrain air flow was examined. It is found that the drilled hole does not necessarily improve the overall performance. It depends on the size of the drilled hole, the number of drilled holes, and the locations. The heat transfer coefficients are generally increased with the number of drilled holes and the diameter of the drilled hole. In this paper, the plate fin heat sink has a higher heat transfer coefficients than pin fins, but the overall performance of the LED panel having pin fin outperforms that of plate fin. This is because the pin fin provides much larger surface area. For decrease the maximum temperature of the LED panel, placement of the drilled holes along the hot region will be more effective.

Periodically Converging-Diverging Tubes and Their Turbulent Heat Transfer, Pressure Drop, Fluid Flow, and Enhancement Characteristics

1984 ◽  
Vol 106 (1) ◽  
pp. 55-63 ◽  
Author(s):  
P. Souza Mendes ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Surface Area ◽  
Equal Mass ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Friction Factors

A comprehensive experimental study was performed to determine entrance region and fully developed heat transfer coefficients, pressure distributions and friction factors, and patterns of fluid flow in periodically converging and diverging tubes. The investigated tubes consisted of a succession of alternately converging and diverging conical sections (i.e., modules) placed end to end. Systematic variations were made in the Reynolds number, the taper angle of the converging and diverging modules, and the module aspect ratio. Flow visualizations were performed using the oil-lampblack technique. A performance analysis comparing periodic tubes and conventional straight tubes was made using the experimentally determined heat transfer coefficients and friction factors as input. For equal mass flow rate and equal transfer surface area, there are large enhancements of the heat transfer coefficient for periodic tubes, with accompanying large pressure drops. For equal pumping power and equal transfer surface area, enhancements in the 30–60 percent range were encountered. These findings indicate that periodic converging-diverging tubes possess favorable enhancement characteristics.

scholarly journals Heat transfer rates in hot shell, cold tube inclined baffled small shell, and tube heat exchanger using CFD and experimental approach

2021 ◽  
Vol 9 (4B) ◽  
Author(s):  
Devanand D. Chillal ◽  
◽  
Uday C. Kapale ◽  
N.R. Banapurmath ◽  
T. M. Yunus Khan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Liquid Flow ◽  
Cfd Analysis ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Tube Heat Exchanger ◽  
Heat Transfer Coefficients ◽  
Shell And Tube ◽  
Cold Liquid

The work presented is an effort to realize the changes occurring for convective coefficients of heat transfer in STHX fitted with inclined baffles. Effort has been undertaken using Fluent, a commercially available CFD code ona CAD model of small STHX with inclined baffles with cold liquid flowing into the tubes and hot liquid flowing in the shell. Four sets of CFD analysis have been carried out. The hot liquid flow rate through shell compartments varied from 0.2 kg/sec to 0.8 kg/sec in steps of 0.2 kg/sec, while keeping the cold liquid flow condition in tube at 0.4 kg/sec constant. Heat transfer rates, compartment temperatures, and overall heat transfer coefficients, for cold liquid and hot liquid, were studied. The results given by the software using CFD approach were appreciable and comparatively in agreement with the results available by the experimental work, which was undertaken for the same set of inlet pressure conditions, liquid flow rates, and inlet temperatures of liquid for both hot and cold liquids. The experimental output results were also used to validate the results given by the CFD software. The results from the CFD analysis were further used to conclude the effect of baffle inclination on heat duty. The process thus followed also helped realize the effects of baffle inclination on convective heat transfer coefficient of the liquid flow through the shell in an inclined baffle shell and tube heat exchanger. The temperature plots for both cold and hot liquid were also generated for understanding the compartmental temperature distributions inclusive of the inlet and outlet compartments. The heat duty for a heat exchanger has been found to increase with the increase in baffle inclinations from zero degree to 20 degrees. Likewise, the convective heat transfer coefficients have also been found to increase with the increase in baffle inclinations.

scholarly journals Experimental Study of Forced Convective Heat Transfer in a Coiled Flow Inverter Using TiO2–Water Nanofluids

2020 ◽  
Vol 10 (15) ◽  
pp. 5225
Author(s):  
Barbara Arevalo-Torres ◽  
Jose L. Lopez-Salinas ◽  
Alejandro J. García-Cuéllar
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convective Thermal ◽  
Convective Heat Transfer Coefficients

The curved geometry of a coiled flow inverter (CFI) promotes chaotic mixing through a combination of coils and bends. Besides the heat exchanger geometry, the heat transfer can be enhanced by improving the thermophysical properties of the working fluid. In this work, aqueous solutions of dispersed TiO2 nanometer-sized particles (i.e., nanofluids) were prepared and characterized, and their effects on heat transfer were experimentally investigated in a CFI heat exchanger inserted in a forced convective thermal loop. The physical and transport properties of the nanofluids were measured within the temperature and volume concentration domains. The convective heat transfer coefficients were obtained at Reynolds numbers (NRe) and TiO2 nanoparticle volume concentrations ranging from 1400 to 9500 and 0–1.5 v/v%, respectively. The Nusselt number (NNu) in the CFI containing 1.0 v/v% nanofluid was 41–52% higher than in the CFI containing pure base fluid (i.e., water), while the 1.5 v/v% nanofluid increased the NNu by 4–8% compared to water. Two new correlations to predict the NNu of TiO2–water nanofluids in the CFI at Reynolds numbers of 1400 ≤ NRe ≤ 9500 and nanoparticle volume concentrations ranges of 0.2–1.0 v/v% and 0.2–1.5 v/v% are proposed.

scholarly journals Thermal-Hydraulic Studies on the Shell-and-Tube Heat Exchanger with Minijets

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3276 ◽  
Author(s):  
Jan Wajs ◽  
Michał Bajor ◽  
Dariusz Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Waste Heat ◽  
Experimental Studies ◽  
Convection Heat Transfer ◽  
Test Facility ◽  
Experimental Investigations ◽  
Transfer Coefficients ◽  
Tube Heat Exchanger ◽  
Shell And Tube

In this paper a patented design of a heat exchanger with minijets, with a cylindrical construction is presented. It is followed by the results of its systematic experimental investigations in the single-phase convection heat transfer mode. Based on these results, validation of selected correlations (coming from the literature) describing the Nusselt number was carried out. An assessment of the heat exchange intensification level in the described heat exchanger was done through the comparison with a shell-and-tube exchanger of a classical design. The thermal-hydraulic characteristics of both units were the subjects of comparison. They were constructed for the identical thermal conditions, i.e., volumetric flow rates of the working media and the media temperatures at the inlets to the heat exchanger. The experimental studies of both heat exchangers were conducted on the same test facility. An increase in the heat transfer coefficients values for the minijets heat exchanger was observed in comparison with the reference one, whereas the generated minijets caused greater hydraulic resistance. Experimentally confirmed intensification of heat transfer on the air side, makes the proposed minijets heat exchanger application more attractive, for the waste heat utilization systems from gas sources.

Simulation of Heat Transfer to Turbulent Nanofluid Flow in an Annular Passage

2014 ◽  
Vol 925 ◽  
pp. 625-629 ◽  
Author(s):  
C.S. Oon ◽  
A. Badarudin ◽  
S.N. Kazi ◽  
M. Fadhli
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Titanium Oxide ◽  
Convective Heat Transfer Coefficient ◽  
Hot Water ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients

The heat transfer in annular heat exchanger with titanium oxide of 1.0 volume % concentration as the medium of heat exchanger is considered in this study. The heat transfer simulation of the flow is performed by using Computational Fluid Dynamics package, Ansys Fluent. The heat transfer coefficients of water to titanium oxide nanofluid flowing in a horizontal counter-flow heat exchanger under turbulent flow conditions are investigated. The results show that the convective heat transfer coefficient of the nanofluid is slightly higher than that of the base fluid by several percents. The heat transfer coefficient increases with the increase of the mass flow rate of hot water and also the nanofluid.

Periodic Streamwise Variations of Heat Transfer Coefficients for Inline and Staggered Arrays of Circular Jets with Crossflow of Spent Air

1980 ◽  
Vol 102 (1) ◽  
pp. 132-137 ◽  
Author(s):  
L. W. Florschuetz ◽  
R. A. Berry ◽  
D. E. Metzger
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Surface ◽  
Test Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Circular Jets ◽  
Impinging Flow

Heat transfer characteristics were measured for inline and staggered arrays of circular jets impinging on a surface parallel to the jet orifice plate. The impinging flow was constrained to exit in a single direction along the channel formed by the jet plate and the heat transfer surface. In this configuration the air discharged from upstream transverse rows of jet holes imposes a crossflow of increasing magnitude on the succeeding downstream jet rows. Streamwise heat transfer coefficient profiles were determined for a streamwise resolution of one-third the streamwise hole spacing, utilizing a specially constructed test surface. These profiles are characterized by significant periodic variations. The downstream amplitudes are diminished by the increasing crossflow magnitude, but can persist for at least ten rows of holes. Results were obtained for streamwise hole spacings of 5, 10, and 15 hole diameters; transverse hole spacings of 4, 6, and 8 diameters; and channel heights of 1, 2, and 3 diameters. The number of transverse hole rows was fixed at ten for all configurations. The characteristics of the periodic variations are presented and discussed as a function of the geometric parameters, including the effect of hole pattern.

scholarly journals Design of heat exchanger network with uncertainty in overall heat transfer coefficients.

1988 ◽  
Vol 21 (4) ◽  
pp. 375-381 ◽  
Author(s):  
HIROKAZU NISHITANI ◽  
YOSHINORI KUTSUWA ◽  
Komi SHIMIZU ◽  
EIICHI KUNUGITA
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Transfer Coefficients ◽  
Heat Exchanger Network ◽  
Heat Transfer Coefficients
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