Computational Fluid Dynamics and Heat Transfer Analysis for a Novel Heat Exchanger

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Haolin Ma ◽  
Dennis E. Oztekin ◽  
Seyfettin Bayraktar ◽  
Sedat Yayla ◽  
Alparslan Oztekin
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Turbulent Flows ◽  
Flow Structure ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Heat Transfer Analysis ◽  
Two Dimensional

Computational fluid dynamics (CFD) and heat transfer simulations are conducted for a novel heat exchanger. The heat exchanger consists of semi-circle cross-sectioned tubes that create narrow slots oriented in the streamwise direction. Numerical simulations are conducted for Reynolds numbers (Re) ranging from 700 to 30,000. Three-dimensional turbulent flows and heat transfer characteristics in the tube bank region are modeled by the k-ε Reynolds-averaged Navier–Stokes (RANS) method. The flow structure predicted by the two-dimensional and three-dimensional simulations is compared against that observed by the particle image velocimetry (PIV) for Re of 1500 and 4000. The adequate agreement between the predicted and observed flow characteristics validates the numerical method and the turbulent model employed here. The three-dimensional and the two-dimensional steady flow simulations are compared to determine the effects of the wall on the flow structure. The wall influences the spatial structure of the vortices formed in the wake of the tubes and near the exit of the slots. The heat transfer coefficient of the slotted tubes improved by more than 40% compare to the traditional nonslotted tubes.

scholarly journals Effect of buried depth on thermal performance of a vertical U-tube underground heat exchanger

Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 327-330
Author(s):  
Li Yang ◽  
Bo Zhang ◽  
Jiří Jaromír Klemeš ◽  
Jie Liu ◽  
Meiyu Song ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Simplified Model ◽  
Two Dimensional ◽  
Construction Sites ◽  
Full Size ◽  
Unit Depth ◽  
Research Show

Abstract Many researchers numerically investigated U-tube underground heat exchanger using a two-dimensional simplified pipe. However, a simplified model results in large errors compared to the data from construction sites. This research is carried out using a three-dimensional full-size model. A model validation is conducted by comparing with experimental data in summer. This article investigates the effects of fluid velocity and buried depth on the heat exchange rate in a vertical U-tube underground heat exchanger based on fluid–structure coupled simulations. Compared with the results at a flow rate of 0.4 m/s, the results of this research show that the heat transfer per buried depth at 1.0 m/s increases by 123.34%. With the increase of the buried depth from 80 to 140 m, the heat transfer per unit depth decreases by 9.72%.

Optimized Chaotic Heat Exchanger Configurations for Process Industry: A Numerical Study

2013 ◽  
Author(s):  
Akram Ghanem ◽  
Thierry Lemenand ◽  
Dominique Della Valle ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Process Intensification ◽  
Point Of View ◽  
Square Duct ◽  
Square Channel ◽  
Duct Geometry

A numerical investigation of chaotic laminar flow and heat transfer in isothermal-wall square-channel configurations is presented. The computations, based on a finite-volume method with the SIMPLEC algorithm, are conducted in terms of Péclet numbers ranging from 7 to 7×105. The geometries, based on the split-and-recombine (SAR) principle, are first proposed for micromixing purposes, and are then optimized and scaled up to three-dimensional minichannels with 3-mm sides that are capable of handling industrial fluid manipulation processes. The aim is to assess the feasibility of this mass- and heat-transfer technique for out-of-laboratory commercial applications and to compare different configurations from a process intensification point of view. The effects of the geometry on heat transfer and flow characteristics are examined. Results show that the flux recombination phenomenon mimicking the baker’s transform in the SAR-1 and SAR-2 configurations produces chaotic structures and promotes mass transfer. This phenomenon also accounts for higher convective heat transfer exemplified by increased values of the Nusselt number compared to the chaotic continuous-flow configuration and the baseline plain square-duct geometry. Energy expenditures are explored and the overall heat transfer enhancement factor for equal pumping power is calculated. The SAR-2 configuration reveals superior heat-transfer characteristics, enhancing the global gain by up to 17-fold over the plain duct heat exchanger.

Direct Design of Ducts

2003 ◽  
Vol 125 (1) ◽  
pp. 158-165 ◽  
Author(s):  
A. Ashrafizadeh ◽  
G. D. Raithby ◽  
G. D. Stubley
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Distribution ◽  
Design Method ◽  
Three Dimensional ◽  
Viscous Flows ◽  
Simple Extension ◽  
Two Dimensional ◽  
Direct Design ◽  
Dependent Variables

This paper describes a method for calculating the shape of duct that leads to a prescribed pressure distribution on the duct walls. The proposed design method is computationally inexpensive, robust, and a simple extension of existing computational fluid dynamics methods; it permits the duct shape to be directly calculated by including the coordinates that define the shape of the duct wall as dependent variables in the formulation. This “direct design method” is presented by application to two-dimensional ideal flow in ducts. The same method applies to many problems in thermofluids, including the design of boundary shapes for three-dimensional internal and external viscous flows.

Variable pitch control for vertical-axis wind turbines

2018 ◽  
Vol 42 (2) ◽  
pp. 128-135 ◽  
Author(s):  
S Horb ◽  
R Fuchs ◽  
A Immas ◽  
F Silvert ◽  
P Deglaire
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Two Dimensional ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Variable Pitch ◽  
Pitch Control

NENUPHAR aims at developing the next generation of large-scale floating offshore vertical-axis wind turbine. To challenge the horizontal-axis wind turbine, the variable blade pitch control appears to be a promising solution. This article focuses on blade pitch law optimization and resulting power and thrust gain depending on the operational conditions. The aerodynamics resulting from the implementation of a variable blade pitch control are studied through numerical simulations, either with a three-dimensional vortex code or with two-dimensional Navier-stokes simulations (two-dimensional computational fluid dynamics). Results showed that the three-dimensional vortex code used as quasi-two-dimensional succeeded to give aerodynamic loads in very good agreement with two-dimensional computational fluid dynamics simulation results. The three-dimensional-vortex code was then used in three-dimensional configuration, highlighting that the variable pitch can enhance the vertical-axis wind turbine power coefficient ( Cp) by more than 15% in maximum power point tracking mode and decrease it by more than 75% in power limitation mode while keeping the thrust below its rated value.

Forced Convection Computational Fluid Dynamics Analysis of Architected and Three-Dimensional Printable Heat Sinks Based on Triply Periodic Minimal Surfaces

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Oraib Al-Ketan ◽  
Mohamed Ali ◽  
Mohamad Khalil ◽  
Reza Rowshan ◽  
Kamran A. Khan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Transfer Coefficient ◽  
Minimal Surfaces ◽  
Heat Sink ◽  
Three Dimensional ◽  
Heat Sinks ◽  
Triply Periodic Minimal Surfaces ◽  
Triply Periodic

Abstract The drive for small and compact electronic components with higher processing capabilities is limited by their ability to dissipate the associated heat generated during operations, and hence, more advanced heat sink designs are required. Recently, the emergence of additive manufacturing techniques facilitated the fabrication of complex structures and overcame the limitation of traditional techniques such as milling, drilling, and casting. Therefore, complex heat sink designs are now easily realizable. In this study, we propose a design procedure for mathematically realizable architected heat sinks and investigate their performance using the computational fluid dynamics (CFD) approach. The proposed heat sinks are mathematically designed with topologies based on triply periodic minimal surfaces (TPMSs). Three-dimensional CFD models are developed using the starccm+ platform for uniform heat sinks and topologically graded heat sinks to study the heat transfer performance in forced convection domains. The overall heat transfer coefficient, surface temperature, and pressure drop versus the input heat sources as well as the Reynolds number are used to evaluate the heat sink performance. Moreover, temperature contours and velocity streamlines were examined to analyze the fluid flow behavior within the heat sinks. Results showed that the tortuosity and channel complexity of the Diamond solid-networks heat sink result in a 32% increase in convective heat transfer coefficient compared with the Gyroid solid-network heat sink which has the comparable surface area under the examined flow conditions. This increase is at the expense of increased pressure drops which increases by the same percentage. In addition, it was found that expanding channel size along flow direction using the porosity grading approach results in significant pressure drop (27.6%), while the corresponding drop in convective heat transfer is less significant (15.7%). These results show the importance of employing functional grading in the design of heat sinks. Also, the manufacturability of the proposed designs was assessed using computerized tomography (CT) scan and scanning electron microscopy (SEM) imaging performed on metallic samples fabricated using powder bed fusion techniques. A visible number of internal manufacturing defects can affect the performance of the proposed heat sinks.

Sign in / Sign up

Export Citation Format

Share Document