ACADEMIC RESEARCH IN MODERN SCIENCE
International scientific-online conference
162
NUMERICAL ANALYSIS OF HEAT TRANSFER USING A BUTTERFLY-
SHAPED DIMPLE IN A RECTANGULAR AIR DUCT
Askarov Dilmurod Bakhtiyor ugli
PhD student
Namangan State Technical University
Babakhodjaev Rakhimjan Pachexanovich
Professor Tashkent State Technical University
Named after Islam Karimov
https://doi.org/10.5281/zenodo.15754117
Abstract:
In this paper, the heat transfer processes using butterfly-shaped
cavities placed in the wall of a rectangular air duct were numerically analyzed.
The CFD (Computational Fluid Dynamics)-based ANSYS Fluent program was
used. The models were built in 3D under the condition of hot air flow, the
Nusselt number, heat transfer coefficient and pressure losses were studied. The
geometry of the cavity was placed perpendicular to the flow. The results were
compared with a smooth-walled duct and the efficiency was evaluated.
Keywords:
Heat transfer, butterfly cavity, CFD, ANSYS Fluent, Nusselt
number, air duct, pressure loss
1. Introduction
Increasing the energy efficiency of air ducts in ventilation, air conditioning,
and industrial heat exchange systems is an important task. Compared with
simple smooth-surfaced ducts, deformed (e.g., grooved) surfaces increase the
turbulence of the flow and enhance heat transfer. In recent years, butterfly-
shaped grooves have attracted attention, as they increase heat transfer
efficiency, but can also increase pressure loss. In this paper, the effect of a
butterfly-shaped groove in a rectangular air duct on heat transfer processes is
numerically analyzed.
2. Methodology
2.1 Geometry and dimple shape
The dimensions of the rectangular air duct were taken as 200 mm × 100
mm × 800 mm. Butterfly-shaped indentations were made in the middle of the
duct wall, one every 5 mm.
2.2 Creating CFD Model
The 3D geometry was drawn in ANSYS Fluent using Comsol Multiphysics
6.2 and imported. The mesh structure was chosen to be denser in areas with
large gradients. The final model contains over 1.2 million elements.
ACADEMIC RESEARCH IN MODERN SCIENCE
International scientific-online conference
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Figure 1. a) 3D view of a butterfly shape; b) Meshed state of a
rectangular air duct.
2.3 Boundary conditions
- Inlet: air temperature – 60°C, velocity – 2 m/s
- Outlet: atmospheric pressure (0 Pa)
- On the walls: constant temperature – 30°C
2.4 Equations
The main heat transfer parameters were calculated as follows:
𝑵
𝒖
=
𝒉𝑳
𝒌
ɳ=
𝑁𝑢
𝑁𝑢0
(
𝛥𝑃
𝛥𝑃0
)
1
3
3. Results and Discussion
3.1 Nusselt Number Variation
The butterfly-shaped grooves increased the heat transfer by 35–42%
compared to the smooth channel. The graph below shows a comparison of the
average Nusselt number for the smooth-walled channel and the butterfly-
ACADEMIC RESEARCH IN MODERN SCIENCE
International scientific-online conference
164
shaped
grooved
channel.
Figure 2. Variation of Nusselt number with channel length.
4. Conclusion
The results of the study showed that butterfly-shaped cavities significantly
improve the heat transfer process. Compared with a smooth channel, the overall
efficiency increases at the expense of a higher Nusselt number and acceptable
pressure loss. This geometric approach has shown promise for application in air
heating, ventilation and other heat exchange systems.
Future plans: In the future, it is planned to study various combinations of
cavity shape, location and size. In particular, studies will be conducted on the
use of optimization algorithms (e.g. genetic algorithm) to further improve heat
transfer efficiency, as well as verification of CFD results through experimental
tests.
References:
1. Bejan, A. (2013). Convection Heat Transfer. Wiley.
2. Incropera, F. P., & DeWitt, D. P. (2007). Fundamentals of Heat and Mass
Transfer. Wiley.
3. ANSYS Fluent Theory Guide, 2023.
4. Jang, D., et al. (2018). "Heat transfer enhancement using dimple and
protrusion geometries in channel flow", Applied Thermal Engineering.
5. Tiwari, S., & Kumar, P. (2020). "Optimization of dimple shape for heat
exchanger", International Journal of Thermal Sciences.
