Experimental and Numerical Analyses of Friction Factors in Offset Strip Fin Heat Exchangers

2007 ◽  
Author(s):  
Aihua Wang ◽  
Samir F. Moujaes ◽  
Yitung Chen ◽  
Valery Ponyavin
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Experimental Measurements ◽  
Test Rig ◽  
Compact Heat Exchangers ◽  
Friction Factors ◽  
Offset Strip Fin

Heat transfer in compact heat exchangers is augmented by the introduction of the offset strip fins. With the breakdown of the thermal and hydro boundary layers to boost heat transfer, the fins increase the friction power. Two heat exchangers of different fin geometries structures were built and tested. The results of the study show that the round-edge-fin heat exchanger has the smaller friction factor. A test rig was constructed to measure the friction factor of the offset strip fin heat exchangers with air. A modified hydraulic diameter was used to calculate the main parameters. The computational fluid dynamics package FLUENT was used to predict the flow in the heat exchanger. The numerical investigation was conducted and compared with experimental measurements.

Heat Transfer Performance of Different Nanofluids Flows in a Helically Coiled Heat Exchanger

2013 ◽  
Vol 832 ◽  
pp. 160-165 ◽  
Author(s):  
Mohammad Alam Khairul ◽  
Rahman Saidur ◽  
Altab Hossain ◽  
Mohammad Abdul Alim ◽  
Islam Mohammed Mahbubul
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Transfer Performance

Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide excellent thermal performance of this type of heat exchangers. In the present study, the effect of different nanofluids on the heat transfer performance in a helically coiled heat exchanger is examined. Four different types of nanofluids CuO/water, Al2O3/water, SiO2/water, and ZnO/water with volume fractions 1 vol.% to 4 vol.% was used throughout this analysis and volume flow rate was remained constant at 3 LPM. Results show that the heat transfer coefficient is high for higher particle volume concentration of CuO/water, Al2O3/water and ZnO/water nanofluids, while the values of the friction factor and pressure drop significantly increase with the increase of nanoparticle volume concentration. On the contrary, low heat transfer coefficient was found in higher concentration of SiO2/water nanofluids. The highest enhancement of heat transfer coefficient and lowest friction factor occurred for CuO/water nanofluids among the four nanofluids. However, highest friction factor and lowest heat transfer coefficient were found for SiO2/water nanofluids. The results reveal that, CuO/water nanofluids indicate significant heat transfer performance for helically coiled heat exchanger systems though this nanofluids exhibits higher pressure drop.

Experimental Investigation of Coil Curvature Effect on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger

2014 ◽  
Vol 7 (1) ◽  
Author(s):  
M. R. Salem ◽  
K. M. Elshazly ◽  
R. Y. Sakr ◽  
R. K. Ali
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Average Nusselt Number ◽  
Transfer Coefficients ◽  
Nusselt Numbers ◽  
Fanning Friction Factor ◽  
Coil Heat

The present work experimentally investigates the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to friction factor for fully developed flow through the helically coiled tube (HCT). The majority of previous studies were performed on HCTs with isothermal and isoflux boundary conditions or shell and coil heat exchangers with small ranges of HCT configurations and fluid operating conditions. Here, five heat exchangers of counter-flow configuration were constructed with different HCT-curvature ratios (δ) and tested at different mass flow rates and inlet temperatures of the two sides of the heat exchangers. Totally, 295 test runs were performed from which the HCT-side and shell-side heat transfer coefficients were calculated. Results showed that the average Nusselt numbers of the two sides of the heat exchangers and the overall heat transfer coefficients increased by increasing coil curvature ratio. The average increase in the average Nusselt number is of 160.3–80.6% for the HCT side and of 224.3–92.6% for the shell side when δ increases from 0.0392 to 0.1194 within the investigated ranges of different parameters. Also, for the same flow rate in both heat exchanger sides, the effect of coil pitch and number of turns with the same coil torsion and tube length is remarkable on shell average Nusselt number while it is insignificant on HCT-average Nusselt number. In addition, a significant increase of 33.2–7.7% is obtained in the HCT-Fanning friction factor (fc) when δ increases from 0.0392 to 0.1194. Correlations for the average Nusselt numbers for both heat exchanger sides and the HCT Fanning friction factor as a function of the investigated parameters are obtained.

A Correlation for Laminar Hydrodynamic Entry Length Solutions for Circular and Noncircular Ducts

1978 ◽  
Vol 100 (2) ◽  
pp. 177-179 ◽  
Author(s):  
R. K. Shah
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchangers ◽  
Circular Tube ◽  
Parallel Plates ◽  
Entry Length ◽  
Compact Heat Exchangers ◽  
Friction Factors ◽  
Proper Design ◽  
Flow Devices

Laminar hydrodynamic entry length solutions for circular and noncircular ducts are essential in proper design of compact heat exchangers and other heat transfer and fluid flow devices. A closed form equation has been proposed to present these solutions for the circular tube, parallel plates, rectangular, equilateral triangular, and concentric annular ducts. The necessary constants are evaluated and it is shown that the proposed correlation predicts the apparent friction factors within ± 2.4 percent.

The Technical Derivation of Heat Transfer Performance of the Airside of a Novel Pin Design Heat Exchanger Using Computational Fluid Dynamics

2012 ◽  
Author(s):  
Tosha Churitter
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Diameter Ratio ◽  
Transfer Performance ◽  
Extended Surface

Pins are a common type of extended surface used in the field of heat transfer; their main application being in the electronics field. Historically, pins used in heat exchangers have diameters that are considered negligible in comparison to their lengths and are therefore termed as tubes. In this report, the use of pins as an extended surface is investigated for the heat transfer on the airside (cold) of the Compact Advanced Pin Surface Heat Exchanger. The pins are circular in cross section and follow a staggered arrangement. The uniqueness of the pin design is such that they cannot be treated as tubes. Key Pin Design features are as follows: • Pins have a maximum Length: Diameter ratio of 3. • Pin Spacing to Pin Diameter ratio is greater than in traditional arrangements. • Pins function as a primary as well as secondary surface. The heat transfer performance of extended surfaces possessing the above features has not been characterized, using commercially available Computational Fluid Dynamics (CFD) software, in any research specifically focused on applications for the aerospace industry. Based on actual test results, this study specially develops a unique approach that can predict the outlet temperature of the heat exchanger to within 1% accuracy. This ‘developed’ approach is applied over cold-side mass flow rates ranging from 0.05 kg/s to 0.23 kg/s, while keeping the hot side mass flow rate constant at 0.05 kg/s. At worst, the simulation results lie within 5% accuracy and at best the simulation accuracy is 1%, a significant improvement on traditional derivations. This article specifically discusses the methodology developed to analyse the heat transfer performance of the novel pin design using Fluent 6.2. It highlights the current limitations of existing equations as well as the theoretical knowledge gap that currently exists in the analysis of pins as extended heat transfer surfaces in heat exchangers.

The Effect of Fin Geometry on Design of Compact Off-Set Strip Fin High Temperature Heat Exchanger

2005 ◽  
Author(s):  
Sundaresan Subramanian ◽  
Valery Ponyavin ◽  
Clayton Ray De Losier ◽  
Yitung Chen ◽  
E. Hechanova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Transfer Enhancement ◽  
Heat Exchanger Design ◽  
Helium Gas ◽  
Temperature Heat ◽  
Overall Performance ◽  
Offset Strip Fin

This paper deals with the development of a three-dimensional numerical model to predict the overall performance of an advanced high temperature heat exchanger design, up to 1000°C, for the production of hydrogen by the sulfur iodine thermo-chemical cycle used in advanced nuclear reactor concepts. The design is an offset strip-fin, hybrid plate compact heat exchanger made from a liquid silicon impregnated carbon composite material. The two working fluids are helium gas and molten salt (Flinak). The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on heat transfer enhancement. The effects of the fin geometry on the flow field and heat transfer are studied in three-dimensions using Computational Fluid Dynamics (CFD) techniques. The pre-processor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT that is based on the finite volume method is used to produce the numerical results. Fin dimensions need to be chosen that optimize heat transfer and minimize pressure drop. Comparison of the overall performance between two fin shapes (rectangular versus curved edges) is performed using computational fluid dynamics techniques. Fin and channel dimensions need to be chosen such as to optimize heat transfer performance and minimize pressure drop. The study is conducted with helium gas and liquid salt as the working fluids with a variety of Reynolds number values and fin dimensions. Both laminar and turbulent modeling is performed for the helium side fluid flow. The effect of the fin geometry is performed computational fluid dynamics techniques and optimization studies are performed. The model developed in this paper is used to investigate the heat exchanger design parameters in order to find an optimal design.

scholarly journals NGNP Process Heat Utilization: Liquid Metal Phase Change Heat Exchanger

2008 ◽  
Author(s):  
Piyush Sabharwall ◽  
Mike Patterson ◽  
Vivek Utgikar ◽  
Fred Gunnerson
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Pressure Drop ◽  
Liquid Metal ◽  
Phase Change ◽  
Heat Exchangers ◽  
Liquid Metals ◽  
Compact Heat Exchangers ◽  
Process Heat

One key long-standing issue that must be overcome to fully realize the successful growth of nuclear power is to determine other benefits of nuclear energy apart from meeting the electricity demands. The Next Generation Nuclear Plant (NGNP) will most likely be producing electricity and heat for the production of hydrogen and/or oil retrieval from oil sands and oil shale to help in our national pursuit of energy independence. For nuclear process heat to be utilized, intermediate heat exchange is required to transfer heat from the NGNP to the hydrogen plant or oil recovery field in the most efficient way possible. Development of nuclear reactor-process heat technology has intensified the interest in liquid metals as heat transfer media because of their ideal transport properties. Liquid metal heat exchangers are not new in practical applications. An important rationale for considering liquid metals as the working fluid is because of the higher convective heat transfer coefficient. This explains the interest in liquid metals as coolant for intermediate heat exchange from NGNP. The production of electric power at higher efficiency via the Brayton Cycle, and hydrogen production, requires both heat at higher temperatures and high effectiveness compact heat exchangers to transfer heat to either the power or process cycle. Compact heat exchangers maximize the heat transfer surface area per volume of heat exchanger; this has the benefit of reducing heat exchanger size and heat losses. High temperature IHX design requirements are governed in part by the allowable temperature drop between the outlet of NGNP and inlet of the process heat facility. In order to improve the characteristics of heat transfer, liquid metal phase change heat exchangers may be more effective and efficient. This paper explores the overall heat transfer characteristics and pressure drop of the phase change heat exchanger with Na as the heat exchanger coolant. In order to design a very efficient and effective heat exchanger one must optimize the design such that we have a high heat transfer and a lower pressure drop, but there is always a tradeoff between them. Based on NGNP operational parameters, a heat exchanger analysis with the sodium phase change is presented to show that the heat exchanger has the potential for highly effective heat transfer, within a small volume at reasonable cost.

scholarly journals Obtaining Closure for Fin-and-Tube Heat Exchanger Modeling Based on Volume Averaging Theory (VAT)

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Feng Zhou ◽  
Nicholas E. Hansen ◽  
David J. Geb ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Volume Averaging ◽  
Averaging Theory ◽  
Length Scale ◽  
Tube Heat Exchanger ◽  
Volume Averaging Theory

Modeling a fin-and-tube heat exchanger as porous media based on volume averaging theory (VAT), specific geometry can be accounted for in such a way that the details of the original structure can be replaced by their averaged counterparts, and the VAT based governing equations can be solved for a wide range of heat exchanger designs. To complete the VAT based model, proper closure is needed, which is related to a local friction factor and a heat transfer coefficient of a representative elementary volume. The present paper describes an effort to model a fin-and-tube heat exchanger based on VAT and obtain closure for the model. Experiment data and correlations for the air side characteristics of fin-and-tube heat exchangers from the published literature were collected and rescaled using the “porous media” length scale suggested by VAT. The results were surprisingly good, collapsing all the data onto a single curve for friction factor and Nusselt number, respectively. It was shown that using the porous media length scale is very beneficial in collapsing complex data yielding simple heat transfer and friction factor correlations and that by proper scaling, closure is a function of the porous media, which further generalizes macroscale porous media equations. The current work is a step closer to our final goal, which is to develop a universal fast running computational tool for multiple-parameter optimization of heat exchangers.

Heat Transfer in Thin, Compact Heat Exchangers With Circular, Rectangular, or Pin-Fin Flow Passages

1992 ◽  
Vol 114 (2) ◽  
pp. 373-382 ◽  
Author(s):  
D. A. Olson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Rectangular Channel ◽  
Fluid Temperature ◽  
Compact Heat Exchangers ◽  
Pin Fin

We have measured heat transfer and pressure drop of three thin, compact heat exchangers in helium gas at 3.5 MPa and higher, with Reynolds numbers of 450 to 36,000. The flow geometries for the three heat exchanger specimens were: circular tube, rectangular channel, and staggered pin fin with tapered pins. The specimens were heated radiatively at heat fluxes up to 77 W/cm2. Correlations were developed for the isothermal friction factor as a function of Reynolds number, and for the Nusselt number as a function of Reynolds number and the ratio of wall temperature to fluid temperature. The specimen with the pin fin internal geometry had significantly better heat transfer than the other specimens, but it also had higher pressure drop. For certain conditions of helium flow and heating, the temperature more than doubled from the inlet to the outlet of the specimens, producing large changes in gas velocity, density, viscosity, and thermal conductivity. These changes in properties did not affect the correlations for friction factor and Nusselt number in turbulent flow.

Air Cooled Compact Heat Exchanger Design for Avionics Thermal Management Using Published Test Data

2003 ◽  
Author(s):  
George Hall ◽  
James Marthinuss
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Thermal Management ◽  
Test Data ◽  
Heat Exchangers ◽  
Optimized Design ◽  
Compact Heat Exchanger ◽  
Compact Heat Exchangers ◽  
Heat Exchanger Design

This paper will discuss air-cooled compact heat exchanger design using published data. Kays & London’s “Compact Heat Exchangers” [1] contains measured heat transfer and pressure drop data on a variety of circular and rectangular passages including circular tubes, tube banks, straight fins, louvered fins, strip or lanced offset fins, wavy fins and pin fins. While “Compact Heat Exchangers” is the benchmark for air cooled heat exchanger test data it makes no attempt to summarize the results or steer the thermal designer to an optimized design based on the different factors or combination of heat transfer, pressure drop, size, weight, or even cost. Using this reduced data and the analytical solutions provided highly efficient compact heat exchangers could be designed. This paper will guide a thermal engineer toward this optimized design without having to run trade studies on every possible heat exchanger design configuration. Typical applications of published fin data in the aerospace and military electronics include electronics cold plates, card rack walls and air-to-air heat exchangers using fan driven and ECS driven air. Airborne electronics often require extremely dense packaging techniques to fit all the required functions into the available volume. While leaving little room for cooling hardware this also drives power densities up to levels (20 W/sq-cm) that require highly efficient heat transfer techniques. Several design issues are discussed including pressure drop, heat transfer, compactness, axial conduction, flow distribution and passage irregularities (bosses). Comparisons between fin performance are made and conclusions are drawn about the applicability of each type of fin to avionics thermal management.

Experimental Study and Genetic-Algorithm-Based Correlation on Shell-Side Heat Transfer and Flow Performance of Three Different Types of Shell-and-Tube Heat Exchangers

2006 ◽  
Vol 129 (9) ◽  
pp. 1277-1285 ◽  
Author(s):  
Qiu-wang Wang ◽  
Gong-nan Xie ◽  
Bo-tao Peng ◽  
Min Zeng
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Shell Side ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Shell And Tube

The heat transfer and pressure drop of three types of shell-and-tube heat exchangers, one with conventional segmental baffles and the other two with continuous helical baffles, were experimentally measured with water flowing in the tube side and oil flowing in the shell side. The genetic algorithm has been used to determine the coefficients of correlations. It is shown that under the identical mass flow, a heat exchanger with continuous helical baffles offers higher heat transfer coefficients and pressure drop than that of a heat exchanger with segmental baffles, while the shell structure of the side-in-side-out model offers better performance than that of the middle-in-middle-out model. The predicted heat transfer rates and friction factors by means of the genetic algorithm provide a closer fit to experimental data than those determined by regression analysis. The predicted corrections of heat transfer and flow performance in the shell sides may be used in engineering applications and comprehensive study. It is recommended that the genetic algorithm can be used to handle more complicated problems and to obtain the optimal correlations.

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