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.

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.

Numerical analysis of compact plate-fin heat exchangers for aerospace applications

2018 ◽  
Vol 28 (2) ◽  
pp. 395-412 ◽  
Author(s):  
Ranganayakulu Chennu
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Conduction ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Design Data ◽  
Content Type ◽  
Compact Heat Exchangers ◽  
Performance Deterioration

Purpose The purpose of this study is to find the thermo-hydraulic performances of compact heat exchangers (CHE’s), which are strongly depending upon the prediction of performance of various types of heat transfer surfaces such as offset strip fins, wavy fins, rectangular fins, triangular fins, triangular and rectangular perforated fins in terms of Colburn “j” and Fanning friction “f” factors. Design/methodology/approach Numerical methods play a major role for analysis of compact plate-fin heat exchangers, which are cost-effective and fast. This paper presents the on-going research and work carried out earlier for single-phase steady-state heat transfer and pressure drop analysis on CHE passages and fins. An analysis of a cross-flow plate-fin compact heat exchanger, accounting for the individual effects of two-dimensional longitudinal heat conduction through the exchanger wall, inlet fluid flow maldistribution and inlet temperature non-uniformity are carried out using a Finite Element Method (FEM). Findings The performance deterioration of high-efficiency cross-flow plate-fin compact heat exchangers have been reviewed with the combined effects of wall longitudinal heat conduction and inlet fluid flow/temperature non-uniformity using a dedicated FEM analysis. It is found that the performance deterioration is quite significant in some typical applications due to the effects of wall longitudinal heat conduction and inlet fluid flow non-uniformity on cross-flow plate-fin heat exchangers. A Computational Fluid Dynamics (CFD) program FLUENT has been used to predict the design data in terms of “j” and “f” factors for plate-fin heat exchanger fins. The suitable design data are generated using CFD analysis covering the laminar, transition and turbulent flow regimes for various types of fins. Originality/value The correlations for the friction factor “f” and Colburn factor “j” have been found to be good. The correlations can be used by the heat exchanger designers and can reduce the number of tests and modification of the prototype to a minimum for similar applications and types of fins.

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.

INVESTIGATION ON HEAT TRANSFER ENHANCEMENT IN A CORRUGATED FIN-AND-TUBE COMPACT HEAT EXCHANGER

2016 ◽  
Vol 78 (10-2) ◽  
Author(s):  
Ahmadali Gholami ◽  
Mazlan A. Wahid ◽  
Hussein A. Mohammed ◽  
A. Saat ◽  
M. Y. M. Fairus ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Loss ◽  
Boundary Layer Separation ◽  
Performance Criteria ◽  
Recirculation Region ◽  
Moderate Pressure ◽  
Compact Heat Exchangers ◽  
Heat Transfer Augmentation

Heat transfer augmentation and pressure loss penalty in the fin-and-tube compact heat exchangers (FTCHEs) with the corrugated shape as a special form of the fin are numerically investigated to improve heat transfer performance criteria in low Reynolds numbers. The corrugated fin as the newly design of fin pattern is presented in this study. The influence of applying corrugated design adjustments on the thermal and hydraulic characteristics of air flow are analyzed on the in-line tube arrangements. The performance of air-side heat transfer and fluid flow is investigated by numerical simulation for Reynolds number ranging from Re = 400 to 800 based on the tube collar diameter, with the corresponding frontal air velocity ranging from 0.35 to 0.72 m/s. The outcomes of simulation revealed that the corrugated fin could significantly improve the heat transfer augmentation of the FTCHEs with a moderate pressure loss penalty. The computational results indicated that some eddies were developed behind the fluted domain of corrugated finwhich produce some disruptions to fluid flow and enhance heat transfer compared with plain fin. The corrugated form of fins could enhance the thermal mixing of the fluid, delay the boundary layer separation, and reduce the size of the wake and the recirculation region behind tubes compared with the conventional form of the fin at the range of Reynolds number used in this study. In addition, the results showed that the average Nusselt number for the FTCHE with corrugated fin increased by 7.05–10.0% over the baseline case and the corresponding pressure loss decreased by 5.0–6.2%.

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