The analysis of heat transfer and pressure loss for the air flow through heated cylinders with concave delta winglet vortex generators in rectangular channel: an experimental study

Heat transfer rate, pressure loss and efficiency are considered as the most important parameters in designing compact heat exchangers. Despite different types of heat exchangers, fin-and-tube compact heat exchangers are still common device in different industries due to the diversity of usage and the low space installation need. The efficiency of the compact heat exchanger can be increased by introducing the fins and increasing the heat transfer rate between the surface and the surroundings. Numerous modifications can be applied to the fin surface to increase heat transfer. Delta-winglet vortex generators (VGs) are known to enhance the heat transfer between the energy carrying fluid and the heat transfer surfaces in plate-fin-and-tube banks, but they have drawbacks as well. They increase the pressure loss and this should be considered. In this paper, the thermal efficiency of compact heat exchanger with VGs is investigated in different variations. The angle of attack, the length and horizontal and vertical position of winglet are the main parameters to consider. Numerical analyses are carried out to examine finned tube heat exchanger with winglets at the fin surface in a relatively low Reynolds number flow for the inline tube arrangements. The results showed that the length of the winglet significantly affects the improvement of heat transfer performance of the fin-and-tube compact heat exchangers with a moderate pressure loss penalty. In addition, the results show that the optimization cannot be performed for one criterion only. More parameters should be considered at the same time to run the process properly and improve the heat exchanger efficiency.

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Thermal-Hydraulic Performance Analysis by Means of Rectangular Winglet Vortex Generators in a Channel: An Experimental Study

European Journal of Engineering and Technology Research ◽

10.24018/ejers.2021.6.3.2424 ◽

2021 ◽

Vol 6 (3) ◽

pp. 150-153

Author(s):

Oktarina Heriyani ◽

Mohamad Djaeni ◽

. Syaiful

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Performance Evaluation ◽

Heat Exchangers ◽

Transfer Rate ◽

Rectangular Channel ◽

Evaluation Criteria ◽

Hydraulic Performance ◽

Vortex Generators ◽

Fluid Flow Velocity

Vortex generators (VGs) are one of the effective passive models used to increase the heat transfer rate in heat exchangers. In this experiment, heat transfer from six cylinders heated to the airflow was improved by attaching rectangular winglet vortex generators (RWVGs) to a plate in a rectangular channel. The installation aimed to increase the value of the thermal-hydraulic performance evaluation criteria in the line. This experimental study was carried out by varying the fluid flow velocity from 0.4 m/s to 2 m/s with an interval of 0.2 m/s in the channel. Three pairs of VGs were arranged in both in-line and staggered configurations. The experimental results show that the thermal-hydraulic performance evaluation criteria for three pairs of vortex generators in the staggered configuration was 15.17% higher than the baseline, while the thermal-hydraulic performance of the in-line arrangement was 1.54% higher than the staggered one.

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Efek vortex generators terhadap peningkatan perpindahan panas pada aliran melewati heated tubes

Turbo Jurnal Program Studi Teknik Mesin ◽

10.24127/trb.v9i2.1303 ◽

2020 ◽

Vol 9 (2) ◽

Author(s):

Yafid Effendi ◽

Ali Rosyidin

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Friction Factor ◽

Rectangular Channel ◽

Evaluation Criteria ◽

Vortex Generators ◽

High Thermal Resistance ◽

Flow Pressure ◽

Delta Winglet

In this decade, improving the rate of heat transfer has become a big challenge. The high thermal resistance of the gas side of the heat exchanger has an impact on the low rate of heat transfer. Therefore, an experimental study was carried out aimed at looking at conditions of hot temperature and decreased air flow pressure through a heated tube in a rectangular channel using artificial surfaces, namely the concave delta winglet and delta winglet vortex generators. Concave delta winglet vortex generators (CDW VGs) are installed in-line and staggered with one, and two pairs are arranged in common-flow-down (CFD) in the direction of flow with an angle of attack of 15o. The experimental results show that the best thermal performance is observed in the use of two rows CDW VGs staggered, where the value of performance evaluation criteria (PEC) is 28.88% higher than the use of CDW VGs in-line, DW VGs staggered and DW VGs in-line at the same Reynolds number. At the same Reynolds number, the Nusselt number ratio and the friction factor ratio increased 45.25% and 152.05% respectively, occurring in two rows of CDW VGs staggered compared to other vortex generators.Keywords: vortex generators, heat transfer, Nusselt number, friction factor, PEC

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