Air-Side Flow and Heat Transfer in Compact Heat Exchangers: A Discussion of Enhancement Mechanisms

1998 ◽  
Vol 19 (4) ◽  
pp. 29-41 ◽  
Author(s):  
ANTHONY M. JACOBI ◽  
RAMESH K. SHAH
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Compact Heat Exchangers ◽  
Flow And Heat Transfer ◽  
Side Flow

Computational Insights Into Air-Side Flow and Heat Transfer in Compact Heat Exchangers

2005 ◽  
Author(s):  
D. K. Tafti
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Computer Experiments ◽  
Transfer Coefficients ◽  
Substantial Impact ◽  
Compact Heat Exchangers ◽  
Thermal Phenomena ◽  
Side Flow

The paper describes two- and three-dimensional computer simulations which are used to study fundamental flow and thermal phenomena in multilouvered fins used for air-side heat transfer enhancement in compact heat exchangers. Results pertaining to flow transition, thermal wake interference, and fintube junction effects are presented. It is shown that a Reynolds number based on flow path rather than louver pitch is more appropriate in defining the onset of transition, and characteristic frequencies in the louver bank scale better with a global length scale such as fin pitch than with louver pitch or thickness. With the aid of computer experiments, the effect of thermal wakes is quantified on the heat capacity of the fin as well as the heat transfer coefficient, and it is established that experiments which neglect accounting for thermal wakes can introduce large errors in the measurement of heat transfer coefficients. Further, it is shown that the geometry of the louver in the vicinity of the tube surface has a large effect on tube heat transfer and can have a substantial impact on the overall heat capacity.

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.

Simulation of Shell-Side Performance of Novel Heat Exchanger

2012 ◽  
Vol 201-202 ◽  
pp. 107-110
Author(s):  
Xing Cao ◽  
Wen Jing Du ◽  
Lin Cheng
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Characteristics ◽  
Shell Side ◽  
Flow And Heat Transfer ◽  
Triangle Zone ◽  
Comprehensive Performance ◽  
Shell And Tube ◽  
Side Flow ◽  
Unit Pressure

Numerical simulation of shell-and-tube heat exchangers with novel helical baffles was carried out by using commercial codes to study shell-side flow and heat transfer characteristics. The results show that compared with shell-and-tube heat exchangers with conventional helical baffles, the ones with novel helical baffles can efficiently reduce the leakage from triangle zone so that the distributions of both the velocity field and heat transfer on tubes are more uniform. The comparison of comprehensive performance which is evaluated by heat transfer coefficient per unit pressure drop between conventional helical baffles and novel ones indicates that the latter performs better.

Study of Compact Heat Exchangers Operating In Self-Sustained Oscillatory Flows

2020 ◽  
pp. 1-37
Author(s):  
Tracy Fullerton ◽  
N. K. Anand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchangers ◽  
Control Volume ◽  
Flow Analysis ◽  
Compact Heat Exchangers ◽  
Flow And Heat Transfer ◽  
Turbulent Flow Regime ◽  
Flat Tubes ◽  
Computer Codes

Abstract Computer codes were developed to study the performance of compact heat exchangers (CHEs) operating in self-sustained oscillatory flow (SSOF) regimes. The methods were based on a Control Volume Based Finite Volume (CVFVM) method for geometric discretization and the Explicit first stage, Single diagonal coefficient, Diagonally Implicit, Runge-Kutta (ESDIRK) method for temporal discretization. The developed codes were validated for both steady and unsteady cases. A study of nine geometrically related domains of flat tubes in staggered configurations was performed. Grid independence was established subject to double cyclic conditions – periodically fully developed flow and heat transfer in the stream-wise direction and cyclic or repeating flow and heat transfer in the cross-stream direction. The maximum Reynolds number was established at approximately 2,000 for the cases studied to avoid the turbulent flow regime. Parameters of interest like Nusselt number, friction factor, and pumping power were calculated for steady and SSOF regimes. An approach was proposed to determine critical Reynolds number (Recrit) for the SSOFs such that for Reynolds number below Recrit the flow remains steady and above Recrit the flow exhibits the characteristics of SSOFs before finally transitioning to fully turbulent conditions. The results indicated a sensitivity of performance parameters to transverse spacing but not to longitudinal spacing. The relative magnitudes of errors associated with simulating an SSOF with a steady flow analysis were also documented.

Computational Fluid Dynamics and Optimization of Flow and Heat Transfer in Coiled Tube-in-Tube Heat Exchangers Under Turbulent Flow Conditions

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Wael I. A. Aly
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Heat Exchangers ◽  
Design Parameters ◽  
Coiled Tube ◽  
Flow And Heat Transfer ◽  
Coil Diameter ◽  
Side Flow

The present computational fluid dynamics (CFD) study was performed to investigate the 3D turbulent flow and heat transfer of coiled tube-in-tube heat exchangers (CTITHEs). The realizable k-ε model with enhanced wall treatment was used to simulate the turbulent flow and heat transfer in the heat exchangers. Temperature dependent thermophysical properties of water were used and heat exchangers are analyzed considering conjugate heat transfer from hot fluid in the inner-coiled tube to cold fluid in the annulus region. After simulations, Taguchi method was used for finding the optimum condition for some design parameters in the range of coil diameter from 0.18 to 0.3 m, tube and annulus flow rates from 2 to 4 and 10 to 20 LPM, respectively. Results show that the Gnielinski correlation used extensively for predicting Nusselt number for turbulent flow in ducts can be used to predict Nusselt number for both inner-coiled tube and annular coiled tube using the friction factor correlation for helical tubes of Mishra and Gupta. Contribution ratio obtained by Taguchi method shows that annulus side flow rate, tube side flow rate, coil diameter, and flow configuration are the most important design parameters in coiled tube-in-tube heat exchangers, respectively.

Laminar Fully Developed Flow and Heat Transfer in Triangular Plate-Fin Ducts

1986 ◽  
Vol 108 (1) ◽  
pp. 24-32 ◽  
Author(s):  
B. R. Baliga ◽  
R. R. Azrak
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Cross Section ◽  
Heat Exchangers ◽  
Conjugate Problem ◽  
Fully Developed Flow ◽  
Compact Heat Exchangers ◽  
Flow And Heat Transfer ◽  
Conductance Parameter ◽  
Local Results

This paper presents a numerical investigation of fully developed flow and heat transfer in triangular cross section plate-fin ducts encountered in compact heat exchangers. Heat conduction in the fin and convection in the fluid are analyzed simultaneously as a conjugate problem. Overall and local results are presented for representative values of the duct aspect ratio and a fin conductance parameter.

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