Abstract:A three dimensional (3D) computational fluid dynamics (CFD) simulation and a neural network model are presented to estimate the behaviors of the Colburn factor (j) and the Fanning friction factor (f) for wavy fin - and - flat tube (WFFT) heat exchangers. Effects of the five geometrical factors of fin pitch, fin height, fin length, fin thickness, and wavy amplitude are investigated over a wide range of Reynolds number (600 Show more
“…According to our previous studies [31][32][33], enhancement of flow path and generation of swirl flows along/perpendicular to the flow direction are the remarkable phenomena in the wavy channels. It seems that the geometry of the cross-section can considerably affect the number, strength, and location of these swirl flows inside the WMC.…”
Section: Effect Of Cross-section Geometry On Performance Of Wmcmentioning
“…According to our previous studies [31][32][33], enhancement of flow path and generation of swirl flows along/perpendicular to the flow direction are the remarkable phenomena in the wavy channels. It seems that the geometry of the cross-section can considerably affect the number, strength, and location of these swirl flows inside the WMC.…”
Section: Effect Of Cross-section Geometry On Performance Of Wmcmentioning
“…Some researchers have studied the effects of some of the aforementioned parameters on the thermal-hydraulic performance of flat tube HE. Numerous numerical and experimental studies have been done to determine the air-side thermal and flow performances using different types of tubes and fins [10,[18][19][20][21][22]. Nascimento and Garcia [23] reported that flat tube with a shallow square dimple enhanced the heat transfer considerably.…”
The performance of compact fin-and-flat tube heat exchangers (HE) can be affected by many geometrical and processing factors and one of them is tube inclination angle. However, the effect of flat tube inclination angle on the thermal-hydraulic performance of the HE is not fully examined. This paper investigates the effects of flat tube inclination angles on heat transfer and pressure drop characteristics of fined flat tube HE when the tubes are deployed in in-line and staggered arrangements. A symmetric numerical method based on FLUENT software was carried out with six different tube inclination angles (0°, 30°, 60°, 90°, 120°, and 150°) in moderately high Reynolds number. From the results, it was observed that heat transfer coefficient increased with the augmentation of the tube inclination angle from 0 o to 90 o and decreased for 120 o and 150 o . With the increase of tube inclination angle, the average Nusselt number rose by 36.3%. This might be due to the reason that the tube surface area increases with the inclination angle, which also results in the largest increment of the pressure drop by 42.0%. Overall, the 90 o tube inclination angle showed the highest enhancement in heat transfer for both inline and staggered configurations with a maximum enhancement of 41.2% for in-line and 32.2% for staggered arrangements. However, the heat transfer enhancements were accompanied by high-pressure drop penalties of up to 44.2% and 42.6% for in-line and staggered arrangements, respectively. Therefore, inclining the tubes at 90 o is recommended where high heat transfer is required. On the other hand, 0 o tube inclination angle is recommended where pumping power is a crucial issue.
“…Wavy fin was another type of fin. Khoshvaght et al [9] established the mathematical model of the wavy fin-and-flat-tube heat exchanger to analyze the heat transfer and resistance performance. Of course, there were improvements around fins in recent years.…”
Energy conservation is a key concern for countries around the world. Enhanced heat exchange is one of the important ways to save energy. The heat transfer process of wet gas is a special heat transfer process, accompanied by a mass transfer phenomenon. Improving the thermal hydraulic performance of wet gas can greatly improve the energy utilization rate. The thermal hydraulic characteristic of finned elliptical tubes with different elliptical axis ratios (0.9 to 0.5) was numerically studied under wet air conditions. Chilton & Colburn factor was chosen as assessment parameters for the thermal performance. The mass transfer effect was characterized by a dehumidifying coefficient. The flow resistance coefficient was adopted to judge the flow characteristic and the London area goodness factor was evaluated for the overall performance. The simulations indicated the superior performance of the finned elliptical tube, j factor of the finned elliptical tube was greater and the flow resistance coefficient was less than that of the finned circular tube. Comparison between different finned elliptical tubes showed that the JF factor increased with the decrease of the elliptical axis ratio. Under the same inlet conditions, the JF factor increases by approximately 50% as the elliptical axis ratio changed from 1 to 0.5.
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