scholarly journals Numerical Analysis of Airside Characteristics in Plain and Wavy Heat Exchangers in the Turbulent Flow Regime

2011 ◽  
Author(s):  
M. Ruhul Amin ◽  
Santhosh K. Ramachandran
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Heat Exchangers ◽  
High Heat ◽  
Efficiency Index ◽  
Turbulent Regime ◽  
High Heat Transfer ◽  
Colburn Factor ◽  
Fin Tube

Numerical investigation has been performed to study the heat transfer and pressure drop characteristics of plain-fin-tube and wavy-fin tube heat exchangers. Performance results are presented in terms of non-dimensional parameters, friction factor and Colburn factor. The flow rate is varied over the range of 2000 ≤ ReH ≤ 7000 in the turbulent regime. The analysis was performed using a finite volume method. Comparisons with experimental data are performed to validate the code. Parametric study is performed to investigate the effects of transverse pitch and wavy angle. It is observed that an increase in transverse pitch results in a decrease in thermal and hydraulic characteristics. On the other hand with the increase of wavy angle, resulting in the increase of the number of corrugations, both the friction factor and Colburn factor increased. The critical balance between high heat transfer and pressure drop is analyzed using the efficiency index. The tube layout in the staggered form is seen to have better heat transfer characteristics than the in-lined layout for both the configurations.

Heat Transfer Enhancement of Double-Tube-Type Heat Exchanger by Petal-Shaped Tube (Study on Optimum Tube Shape)

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Toshihiko Shakouchi ◽  
Yusuke Matsumoto ◽  
Koichi Tsujimoto ◽  
Toshitake Ando
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
High Heat ◽  
Practical Applications ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Tube Shape ◽  
Tube Type ◽  
Wetted Perimeter ◽  
Fin Tube

Abstract Heat exchangers are used widely in many fields, and various kinds of exchanger have been developed according to the requirement of the practical applications. Recently, heat exchangers that are highly efficient or compact have become more desirable from the viewpoint of energy conservation, and several new types have been developed, such as a compact fin tube type and a double tube type having an inner pipe with a special geometry. In this study, the flow and heat transfer characteristics of a petal-shaped double tube with a large wetted perimeter of six and five petals and five shallow petals and the effect of tube shape on the heat transfer and heat transfer efficiency were examined experimentally. The heat transfer of the double tube with a petal-shaped inner tube was increased because of the large wetted perimeter, but the pressure loss by friction increased. The optimal shape of the petal-shaped double tube with a high heat transfer performance and the greatest efficiency is discussed.

scholarly journals Experimental Investigation of the Flow and Heat Transfer Characteristics in Microchannel Heat Exchangers with Reentrant Cavities

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 403 ◽  
Author(s):  
Binghuan Huang ◽  
Haiwang Li ◽  
Tiantong Xu
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Volume Ratio ◽  
High Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
The Impact

The application of microchannel heat exchangers is of great significance in industrial fields due to their advantages of miniaturized scale, large surface-area-to-volume ratio, and high heat transfer rate. In this study, microchannel heat exchangers with and without fan-shaped reentrant cavities were designed and manufactured, and experiments were conducted to investigate the flow and heat-transfer characteristics. The impact rising from the radius of reentrant cavities, as well as the Reynolds number on the heat transfer and the pressure drop, is also analyzed. The results indicate that, compared with straight microchannels, microchannels with reentrant cavities could enhance the heat transfer and, more importantly, reduce the pressure drop at the same time. For the ranges of parameters studied, increasing the radius of reentrant cavities could augment the effect of pressure-drop reduction, while the corresponding variation of heat transfer is complicated. It is considered that adding reentrant cavities in microchannel heat exchangers is an ideal approach to improve performance.

scholarly journals Flow and Heat Transfer Simulation Analysis of 3D Compact Heat Exchanger

2021 ◽  
Vol 88 (3) ◽  
pp. 71-87
Author(s):  
G. Sashwin Nair ◽  
Ahmed N. Oumer ◽  
Azizuddin Abd Aziz ◽  
Januar Parlaungan Siregar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Inclination Angle ◽  
Heat Exchangers ◽  
Simulation Analysis ◽  
Three Dimensional ◽  
High Heat ◽  
Ansys Fluent ◽  
High Heat Transfer ◽  
Fin Spacing

Compact heat exchangers (CHEs) are one of the most commonly used heat exchangers in the industry due to their superior advantages over other types of heat exchangers. Various geometric (fin spacing, tube inclination angle, etc) and process (such as flow velocity, temperature, etc) parameters affect the performance of such compact HEs. This research aims to examine the effects of fin spacing, tube inclination angle, and airflow velocity on heat transfer and pressure drop performance of CHE in both inline and staggered configurations. A three-dimensional (3D) numerical method with the aid of Ansys FLUENT software was carried out for the laminar flow condition. Based on the obtained results, the highest average heat transfer coefficient was observed at 120° for both tube arrangements while the lowest average pressure drop penalty is at 30°. Therefore, the recommended inclination angle when high heat transfer is needed is at 120° while if the pumping power is the major problem, 30 °or 150° is recommended. based on the London area goodness factor (j/f), 30° and 150° show the highest value for both configurations. The j/f factor decreases with the increase of Reynolds number for both configurations. In addition, 120° shows the lowest j/f which can be due to the high pressure drop.

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.

An Analytical Study of the Optimized Performance of an Impingement Heat Sink

2004 ◽  
Vol 126 (4) ◽  
pp. 528-534 ◽  
Author(s):  
S. B. Sathe ◽  
B. G. Sammakia
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
High Performance ◽  
Cross Flow ◽  
High Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Flow Through

The results of a study of a new and unique high-performance air-cooled impingement heat sink are presented. An extensive numerical investigation of the heat sink performance is conducted and is verified by experimental data. The study is relevant to cooling of high-power chips and modules in air-cooled environments and applies to workstations or mainframes. In the study, a rectangular jet impinges on a set of parallel fins and then turns into cross flow. The effects of the fin thickness, gap nozzle width and fin shape on the heat transfer and pressure drop are investigated. It is found that pressure drop is reduced by cutting the fins in the central impingement zone without sacrificing the heat transfer due to a reduction in the extent of the stagnant zone. A combination of fin thicknesses of the order of 0.5 mm and channel gaps of 0.8 mm with appropriate central cutout yielded heat transfer coefficients over 1500 W/m2 K at a pressure drop of less than 100 N/m2, as is typically available in high-end workstations. A detailed study of flow-through heat sinks subject to the same constraints as the impingement heat sink showed that the flow-through heat sink could not achieve the high heat transfer coefficients at a low pressure drop.

A study of non-redirection louvre fin-and-tube heat exchangers

1998 ◽  
Vol 212 (1) ◽  
pp. 1-14 ◽  
Author(s):  
C-C Wang ◽  
Y-P Chang ◽  
K-Y Chi ◽  
Y-J Chang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Wind Tunnel ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Geometrical Parameters ◽  
Tube Size ◽  
Collar Diameter ◽  
Fanning Friction Factor

Extensive experiments on the heat transfer and pressure drop characteristics of louvre finand-tube heat exchangers were carried out. In the present study, 14 samples of non-redirection louvre fin-and-tube heat exchangers with different geometrical parameters, including the number of tube row, fin pitch and tube size, were tested in a wind tunnel. Results are presented as plots of the Fanning friction factor f and the Colburn j factor against Reynolds number based on the tube collar diameter in the range of 300–8000.

Review of the Development of Compact, High Performance Heat Exchangers for Gas Turbine Applications

2006 ◽  
Author(s):  
Neal R. Herring ◽  
Stephen D. Heister
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
High Performance ◽  
High Heat ◽  
Swirl Flow ◽  
Acoustic Oscillations ◽  
Transfer Coefficients ◽  
High Heat Transfer

This study provides a review of the current state-of-the-art in compact heat exchangers and their application to gas turbine thermal management. Specifically, the challenges and potential solutions for a cooled cooling air system using the aircraft fuel as a heat sink were analyzed. As the sensible heat absorbed by the fuel in future engines is increased, the fuel will be exposed to increasingly hotter temperatures. This poses a number of design challenges for fuel-air heat exchangers. The most well known challenge is fuel deposition or coking. Another problem encountered at high fuel temperatures is thermo-acoustic oscillations. Thermo-acoustic oscillations have been shown to occur in many fluids when heated near the critical point, yet the mechanism of these oscillations is poorly understood. In some cases these instabilities have been strong enough cause failure in the thin walled tubes used in heat exchangers. For the specific application of a fuel-air heat exchanger, the advantages of a laminar flow device are discussed. These devices make use of the thermal entry region to achieve high heat transfer coefficients. To increase performance further, heat transfer enhancement techniques were reviewed and the feasibility for aerospace heat exchangers was analyzed. Two of the most basic techniques for laminar flow enhancement include tube inserts and swirl flow devices. Additionally, the effects of these devices on both coking and instabilities have been assessed.

scholarly journals Cooling of High Heat Flux Flat Surface with Nanofluid Assisted Convective Loop: Experimental Assessment

2017 ◽  
Vol 64 (4) ◽  
pp. 519-531 ◽  
Author(s):  
Amir Arya ◽  
Saeed Shahmiry ◽  
Vahid Nikkhah ◽  
Mohamad Mohsen Sarafraz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
High Heat ◽  
High Heat Flux ◽  
Overall Heat Transfer Coefficient ◽  
Cooling Loop ◽  
The Heat Transfer Coefficient

Abstract Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. % = 0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.

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