Investigation of thermal-hydraulic performance in flat tube heat exchangers at various tube inclination angles

Abstract

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.

Flow and Heat Transfer Simulation Analysis of 3D Compact Heat Exchanger

“…[8]. As predicted, the heat transfer coefficient value for 30° and 60° were almost the same with 150° and 120° respectively which is the same as the results claimed by Adam et al [15]. Apart from that, the average heat transfer coefficient for inline arrangement is higher than the staggered arrangement.…”

“…This clearly shows that the outlet temperature value of the present study lies within the allowable range of error as several previous research error shows more than 9.8% and they assume the model is valid. [7,8,15]. Therefore, good acceptance between the present study and previous research study shows that the numerical model is valid.…”

“…Square-shaped fins were used with the dimension of 110 mm x 110 mm and 0.6 mm thickness while Table 1 shows the other geometric parameters of the HE whereas Table 2 shows the properties of air. In this study, the geometric parameters of the HE are considered as previous work done by Adam et al, [15].…”

“…In comparison with inline and staggered, inline arrangement shows a higher average heat transfer coefficient than staggered arrangement. This could be because the tube around the staggered configuration has an uneven flow [15].…”

“…Many types of research work on tube arrangement on heat transfer performance were done by many researchers [7,8,13,14]. Moreover, numerous studies have been conducted on the effect of various tube angles on CHE heat transfer performance [3,4,12,15]. The study related to the tube arrangement and tube angle has been done separately.…”