An experimental investigation in forced convective heat transfer and friction factor of air flow over aligned round and flattened tube banks (original) (raw)
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2020
One of the most common equipment that are used in all types of power plants and engines are heat exchangers. FTHEs are widely used in various applications, e.g. ventilating and air-conditioning systems, refrigeration, and car radiators etc. as they own high performance and low space requirement. In this study, the characteristics of the forced convective heat transfer and pressure drop in both inline and staggered arrangements of circular fin cross flow heat exchanger are Experimentally investigated and the effect of mass flow rate on parameters such as Nusselt number, overall heat transfer coefficient, and heat transfer is studied. The air was blown with the velocities 0.2m/s, 1m/s, and 2.3m/s and the corresponding changes in inlet and outlet temperature of hot and cold air was measured. It was found that the Heat transfer (Q), Heat transfer coefficient(h), and Nusselt number(Nu) all increase with the increase in mass flow rate for both the inline and staggered arrangement and inli...
Heat Transfer and Fluid Flow Characteristic in banks Flat Tubes, 2009
In this research a study effect of the length ratio (L/Da) and the height ratio (H/Da) for banks flat tube heat exchanger In-Line and staggered arrangement on force convection heat transfer and friction coefficient by (Fluent-CFD) numerical program. The governing equations (mass, momentum and energy) are solving by using Finite Volume (Fluent-CFD) software for considering steady state, two dimensional, at constant heat flux with Reynold’s number (100≤Re≤8000). The results show that increasing (H/Da), (L/Da) lead to decreasing friction coefficient and enhancement of (Nu) is at (H/Da=2) for all (L/Da) values Inline arrangement and at (H/Da =2, L/Da =5) for staggered arrangement.
Numerical Investigation of Thermal-Flow Characteristics in Heat Exchanger with Various Tube Shapes
Applied Sciences, 2021
In this study, eight configurations of oval and flat tubes in annular finned-tube thermal devices are examined and compared with the conventional circular tube. The objective is to assess the effect of tube flatness and axis ratio of the oval tube on thermal-flow characteristics of a three-row staggered bank for Re (2600 ≤ Re ≤ 10,200). It has been observed that the thermal exchange rate and Colburn factor increase according to the axis ratio and the flatness, where O1 and F1 provide the highest values. O1 produces the lowest friction factor values of all the oval tubes at all Re, and F4 gives 13.2–18.5% less friction than the other tube forms. In terms of performance evaluation criterion, all of the tested tubes outperformed the conventional circular tube (O5), with O1 and F1 obtaining the highest values. The global performance criterion of O1 has been found to be 9.6–45.9% higher as compared to the other oval tube geometries at lower values of Re, and the global performance criter...
Heat Transfer and Fluid Flow Characteristic in banks Flat Tubes
Tikrit Journal of Engineering Sciences
In this research a study effect of the length ratio (L/Da) and the height ratio (H/Da) for banks flat tube heat exchanger In-Line and staggered arrangement on force convection heat transfer and friction coefficient by (Fluent-CFD) numerical program.The governing equations (mass, momentum and energy) are solving by using Finite Volume (Fluent-CFD) software for considering steady state, two dimensional, at constant heat flux with Reynold’s number (100≤Re≤8000).The results show that increasing (H/Da), (L/Da) lead to decreasing friction coefficient and enhancement of (Nu) is at (H/Da=2) for all (L/Da) values In-line arrangement and at (H/Da =2, L/Da =5) for staggered arrangement.
International Journal of Automotive and Mechanical Engineering, 2013
This paper presents an experimental investigation into the heat transfer and pressure drop characteristics of air flow in a staggered flat tube bank in crossflow with laminarforced convection. Measurements were conducted for sixteen tubes in the direction of flow and four tubes in rows. The air velocity varies between 0.6-1.0 m/s and the Reynolds number varied from 373 to 623. The total heat flux supplied in all tubes are changed from 967.92 to 3629.70 W/m 2. The results indicate that the average Nusselt number for all the flat tubes increased by 11.46-46.42%, with the Reynolds numbers varying from 373 to 623 at the fixed heat flux. The average Nusselt number increased by 21.39-84%, and the total heat flux varyied between 967.92-3629.70 W/m 2 with a constant Reynolds number Re = 498. In addition, the pressure drop decreased with an increase in the Reynolds number. A new mean Nusselt number-Reynolds number correlation was found, and the correlation yielded good predictions for the measured data with a confidence interval of 98.9%.
Crossflow and Heat Transfer Characteristics Across a Cam-Shaped Tube Bank: A Numerical Study
Front. Heat Mass Transf.
Tubes are commonly employed in heat exchangers for their ease of production and capacity to sustain high pressure. In this study, the heat and flow transfer behaviour of cam-shaped tube bank in staggered configuration at varying angles of attack 0° to 180° was numerically investigated. The study was carried out by solving the continuity, momentum, energy and realizable k-ε transport equations using the finite volume-based ANSYS Fluent solver. This was performed to acquire the friction factor and heat transfer characteristics in the air inlet velocity range of 9 to 15 m/s. The results showed that the cam-shaped tube bank at varying angles of attack provided enhanced heat transfer characteristics relative to the circular tube bank. Also, camshaped tube banks at angles of attack of 90° and 120° exhibited the maximum heat transfer with 33.9 and 32.1% increase in Nusselt number over the circular tubes. Their friction factor was higher by 183 and 140.7%, respectively. The cam-shaped tube banks generally exhibited higher performance than the circular tube bank. Tube banks at angles of attack of 150° and 180° demonstrated higher thermal-hydraulic performance by 167.6 and 284.3% than the circular tubes, respectively. However, the tube banks at angles 90° and 120° exhibited lesser performance by value of 52.6 and 45.1%.
Mechanics and Mechanical Engineering, 2018
As the effective selection of fin can greatly enhance the performance of heat exchanger, heat transfer and pressure drop performance on the air-side of annular and rectangular finned tube heat exchangers were numerically investigated. Two types of tube arrangement (in-line and staggered alignment) were examined for 6 different air flow rate for both the heat exchangers using computational fluid dynamics software package ANSYS FLUENT. Renormalization group theory (RNG) based k-ε turbulence model was employed to handle the unsteady three-dimensional flow and the conjugate heat transfer characteristics. The exit temperature were determined from the simulated results and then the LMTD, heat transfer rate and air-side heat transfer coefficient were calculated. The numerical flow visualization results revealed few important aspects, such as, the development boundary layers between the fins, the formation of the horseshoe vortex system, and the local variations of the velocity and temperat...
Processes
The heat transfer was experimentally and numerically studied in this article. Characteristics of circular fins over a bent tube at different tube orientations and air velocities were investigated, and then compared with analytical results from the literature. For the experimental investigation, a simple setup was compiled inside of a wind tunnel, where the velocity and the inlet temperature of the air; the volume flow rate; and the inlet and outlet temperatures of the water were measured. Three different orientations were investigated with the set-up: the bent tube in line with the air flow with the same and opposite water inlet positions, and the bent tube perpendicular to the air flow. According to the results, the position has a significant effect on the heat transfer coefficient. A numerical study was also performed in accordance with the measurements in ANSYS-CFX computational fluid dynamics (CFD) software. The results of the CFD showed an acceptable correlation with the result...
MECHANICS AND MECHANICAL ENGINEERING, 2018
As the effective selection of fin can greatly enhance the performance of heat exchanger, heat transfer and pressure drop performance on the air-side of annular and rectangular finned tube heat exchangers were numerically investigated. Two types of tube arrangement (in-line and staggered alignment) were examined for 6 different air flow rate for both the heat exchangers using computational fluid dynamics software package ANSYS FLUENT. Renormalization group theory (RNG) based k-ε turbulence model was employed to handle the unsteady three-dimensional flow and the conjugate heat transfer characteristics. The exit temperature were determined from the simulated results and then the LMTD, heat transfer rate and air-side heat transfer coefficient were calculated. The numerical flow visualization results revealed few important aspects, such as, the development boundary layers between the fins, the formation of the horseshoe vortex system, and the local variations of the velocity and temperature on the fin geometries. The result shows that as the air flow rate increased the exit temperature decreased but the overall heat transfer increased. Staggered configuration shows higher heat transfer characteristics over the in-line configuration. The rectangular finned tube shows 17 to 24% improvement in heat transfer over the annular finned tube.
International Journal of Heat and Mass Transfer, 2017
Numerical study on confined flow over circular tube isolated from the bundle of circular tubes in a compact and widely spaced heat exchangers, to explore the influence of flow shedding frequency under forced convection heat transfer. The flow and heat transfer characteristics such as pressure, frictional and total drag coefficients, skin friction coefficient, Strouhal number, volume goodness factor, convective heat transfer coefficient, Nusselt number and effectiveness are estimated for different dimensionless transverse pitch ratios and Reynolds numbers. The highly confined flow past a circular tube makes the flow steady, highly attached and postponed the flow separation, flow shedding and also advances the laminar to turbulent transition. The increases in flow attachments and transitions have been confirmed by observing the frictional drag and skin friction coefficients and also through various contours respectively. Three different flow shedding nature has been observed when Reynolds number increases at different blockage ratios. It is confirmed that the heat transfer enhancement in compact and widely spaced heat exchanger at blockage ratios less than or equal to 3 does not depend on flow shedding frequency. Also, at low Reynolds number region, the heat transfer enhancement is due to highly attached flow. But the gradual increase in Reynolds number advances laminar to turbulent transition and responsible in heat dissipation.