Enhancing sustainability of heating systems in humid regions: A framework for flue system design based on thermal-acoustic-aerodynamic performance

Software	Main capabilities	Advantages	Limitations
Kesa-aladin	Thermal, aerodynamic, and acoustic simulation of flue systems under real operating conditions	− Accurate modeling of chimney systems − Includes real-world parameters − Specialized in chimney/flue analysis	− Proprietary and license-based − Limited applicability outside chimney/flue systems
ANSYS Fluent	Computational fluid dynamics (CFD) for heat transfer and fluid flow	− High precision in fluid dynamics − Extensive material and flow databases − Widely used in academia	− Requires high computational resources − Steep learning curve
Energy Plus	Building energy modeling including HVAC and envelope components	− Open-source and widely supported − Integrates with multiple platforms (e.g., OpenStudio, DesignBuilder)	− Limited detail for flue-specific components − Requires customization for chimney modeling
COMSOL multiphysics	Multiphysics simulation, including heat transfer and structural performance	− Flexible and modular − Capable of coupling thermal and structural analyses	− Expensive license − Less intuitive interface for beginners
Solid works flow	Thermal and fluid dynamics simulation inside CAD-integrated environment	− User-friendly interface − Integrated with CAD − Useful for early design exploration	− Limited for complex fluid flow scenarios − Less advanced than dedicated CFD tools
Simulation
Autodesk CFD	Simulation of airflow and temperature distribution	− Strong visualization tools − Good for iterative design − Integration with other Autodesk tools	− Limited to thermal and fluid domains − Subscription-based
Open FOAM	Open-source CFD platform for customized simulations	− Free and customizable − Highly accurate − Strong community support	− Requires coding skills − Steep learning curve for beginners
Wufi Plus	Hygrothermal simulation of building components including airflows	− Excellent for humidity-focused design − Suitable for regions with high moisture (e.g., Rize)	− Not specifically designed for flue systems − Commercial license
TRNSYS	Transient system simulation for HVAC and energy systems	− Modular and extensible − Suitable for dynamic simulations	− Less intuitive for geometric modeling − Complex setup for flue-specific analysis

Source: Refs. 36–45.

Table 2

Key output parameters in flue system analysis by simulation software

Software	Thermal parameters	Fluid dynamics parameters	Structural/acoustic parameters	Additional features
Kesa-aladin	Flue gas temperature	Pressure drop	Acoustic transmission	Material compatibility
	Heat loss	Flow velocity	Vibration behavior	Real-climate simulation
	Condensation risk	Turbulence levels	Vibration behavior	Real-climate simulation
ANSYS Fluent	Heat transfer rate	Velocity vectors	Thermal stress (with coupling)	Soot deposition modeling
	Temperature gradients	Velocity vectors
		Pressure distribution
		Pressure distribution		Combustion gas flow
		CFD turbulence		Combustion gas flow
EnergyPlus	Seasonal heating demand	Ventilation flow rates (simplified)	—	Energy efficiency metrics
	Seasonal heating demand			Carbon emission estimates
	Fuel consumption			Carbon emission estimates
COMSOL multiphysics	Heat flux	Flow resistance	Structural deformation	Coupled heat-structure-flow analysis
	Thermal conductivity		Structural deformation
			Material stress
		Airflow patterns	Material stress
SolidWorks flow simulation	Surface temperature	Internal airflow	—	Design iteration with CAD-based geometry
	Surface temperature	Pressure gradients
	Thermal loss	Pressure gradients
Autodesk CFD	Cooling/heating loads	Laminar/turbulent flow paths	—	Cloud-based computing
	Thermal comfort mapping			Cloud-based computing
	Thermal comfort mapping			Design visualization
OpenFOAM	Temperature field	Dynamic pressure	– (can be extended with custom models)	Advanced scripting for transient and turbulent flow
OpenFOAM	Wall heat transfer rates	Flow separation	– (can be extended with custom models)	Advanced scripting for transient and turbulent flow
Wufi Plus	Dew point	Air leakage	—	Hygrothermal risk analysis
Wufi Plus	Water vapor diffusion	Moisture-related airflow	—	Climate-responsive simulations
TRNSYS	Time-based heat gain/loss	System airflow rates (HVAC)	—	Scenario simulation
TRNSYS	Time-based heat gain/loss	System airflow rates (HVAC)	—	Integration with renewable systems

* Thermal Parameters: Chimney wall temperature, flue gas cooling, condensation thresholds, etc.

* Fluid Dynamics Parameters: Pressure drop, flow uniformity, backdraft risk, air velocity, etc.

* Structural/Acoustic Parameters: Material stress under heat, sound propagation in ducts, vibration impacts.

* Additional Features: Usability, climate data integration, energy and emission forecasting, CAD/BIM support.

Source: Refs. 36–45.

Table 3

Coverage of chimney components in simulation software

Software	Cap	Flue pipe	Wall penetration	Shaft	Base/connection	Insulation layer
Kesa-aladin	✓	✓	✓	✓	✓	✓
ANSYS Fluent	✓	✓	∼	✓	✓	∼
EnergyPlus	×	∼	×	∼	∼	∼
COMSOL Multiphysics	✓	✓	✓	✓	✓	✓
SolidWorks Flow Sim.	✓	✓	∼	∼	✓	×
Autodesk CFD	✓	✓	∼	∼	✓	×
OpenFOAM	✓	✓	✓ (custom)	✓	✓ (custom)	✓ (custom)
Wufi Plus	×	∼	✓	∼	×	✓
TRNSYS	×	∼	×	∼	∼	×
	✓ (Full Support): The software can analyze this component directly and in detail. ∼ (Partial/Conditional): Support is available only with additional modules, custom modeling, or external data. × (Not Supported): Direct analysis is not possible.

Source: Refs. 36–45.

Table 4

Computations and input and output parameters of Kesa-aladin simulation software [35]

Software computations	Flue gas temperature profile
	Flue gas velocity and density
	Pressure losses and draft behavior
	Sound levels generated by flue flow
	Heat losses through inner and outer chimney walls
	Wind speed effects under different external temperatures (±15°C)
Input parameters	Boiler combustion data (fuel type, output power, exhaust temperature)
	Chimney geometry and height
	Internal surface roughness coefficients for each material
	Outdoor air temperature and wind speed scenarios
	Insulation properties (Rockwool layer, stainless steel exterior, etc.)
Output parameters	Mouth cross-sectional area (cm²)
	Flow velocity (m/s)
	Flue gas density (kg/m³)
	Draft sound level (dBA)
	Wind interference velocity (m/s) at −15 and +15°C
	Stagnant pressure (Pa)
	Flue gas exit velocity (m/s)
	Maximum negative draft pressure (Pa)
	Flue gas temperature (°C)
	Inner wall and material surface temperature (°C)
	Insulation and outer wall temperature (°C)
	Direct airflow temperature and sidewall (R12) temperature (°C)

Source: Author’s contribution.

Comparison of rectangular and square form chimney mouth cross-section.

Comparison of stack flow velocity in rectangular and square form.

Comparison of flue gas density from rectangular and square stacks.

Comparison of chimney flow sound in rectangular and square forms.

−15°C wind speed comparison for rectangular- and square-shaped chimneys.

Comparison of wind speed (+15°C) of rectangular- and square-shaped chimney.

Comparison of stagnant pressure in rectangular- and square-shaped chimneys.

Comparison of flue gas velocity in rectangular- and square-shaped chimneys.

Comparison of maximum negative pressures of rectangular- and square-shaped chimneys.

Temperature comparison of exhaust gases of rectangular- and square-shaped chimneys.

Temperature comparison of the inner wall of rectangular- and square-shaped exterior and interior chimneys.

Comparison of temperature for rectangular and square flue materials.

Temperature comparison of the material used in rectangular and square chimney insulation.

Temperature comparison of materials used in the outer wall coating of rectangular- and square-shaped chimneys.

Comparison of air temperature in direct current of rectangular- and square-shaped chimneys.

Rectangular- and square-shaped chimney sidewall (R12) temperature comparison.

Table 5

Maximum and minimum values of the outputs of the Kesa-aladin analysis

	Square section				Rectangular section
	Concrete form stones	Varnished inside ceramic	Chamotte form stones	Unvarnished ceramic	Concrete form stones	Varnished inside ceramic	Chamotte form stones	Unvarnished ceramic
Mouth section	331.2	309.8	316.8	307.3	329.6	307.6	317.2	307.6
Flow velocity	3.26	3.72	3.51	3.75	3.27	3.74	3.51	3.74
Fuel gas condensation	0.896	0.84	0.869	0.839	0.896	0.84	0.869	0.84
Flow noise	15.9	18.4	17.3	18.6	15.9	18.5	17.3	18.5
T – 15	6.86	7.34	7.16	7.39	6.88	7.38	7.16	7.38
T + 15	7.66	8.19	8	8.25	7.68	8.24	8	8.24
Static pressure	56.1	61.2	58.4	61.2	56.1	61.2	58.4	61.2
Fuel gas velocity	4.06	4.41	4.27	4.45	4.08	4.44	4.26	4.45
Maximum negative pressure	62	68.1	64.9	68.2	62.1	68.2	64.9	68.2
Fuel gas	195	202	197	202	195	202	197	202
Inner wall	156	173	161	173	156	173	161	173
Stainless steel	156	154	163	154	116	154	103	154
Rockwool	53	63	48	63	53	63	49	63
Outer wall, steel	53	63	48	63	53	63	49	63
Direction air	39	37	36	37	39	37	36	37
Sidewall (R12)	37	35	35	35	37	35	35	35

Source: Author’s contribution.

Table 6

Feature importance ranking for chimney performance based on random forest regression analysis

Rank	Feature	Importance
1	Maximum negative pressure	0.42
2	Flow velocity	0.31
3	Inner wall temperature	0.10
4	Insulation temperature	0.09
5	Flow sound	0.08

Source: Author’s contribution.

Table 7

Comparison of TOPSIS and VIKOR methodologies

Criteria	TOPSIS methodology	VIKOR methodology
Advantages	Considers both the ideal and anti-ideal solutions.	Balances group utility (majority rule) and individual regret (minority opposition).
	Simple, intuitive, and easy to implement.	Effective in compromise decision-making.
	Provides clear ranking of alternatives.	Suitable for problems with conflicting criteria.
	Computationally efficient for large datasets.	Flexible for decision contexts requiring trade-offs.
Disadvantages	Results are highly sensitive to the normalization method used.	Requires determining a compromise parameter (v), which may affect results.
	Does not explicitly address conflict between criteria.	More complex to explain to non-experts.
	Distances may not fully capture decision-maker preferences.	Can produce rank reversals depending on dataset changes.
Limitations	Assumes criteria weights are reliable and predetermined.	Sensitive to the selection of normalization and aggregation strategies.
Limitations	Ignores uncertainty and fuzziness in input data unless extended versions (e.g., Fuzzy TOPSIS) are applied.	Performance depends on the accuracy of criteria weights and compromise parameter.
Usage fields	Engineering design optimization.	Public policy and social decision-making.
	Supplier and vendor selection.	Conflict resolution in resource allocation.
	Energy system evaluation.	Sustainable development planning.
	Environmental management and sustainability studies.	Healthcare and risk management decisions.

Source: Author’s contribution.

Table 8

Comparative ranking of chimney alternatives using TOPSIS and VIKOR methods

Geometry	Material	TOPSIS score	TOPSIS rank	VIKOR Q	VIKOR rank
Square	Chamotte form stones	0.698	1	0.035	1
Rectangular	Chamotte form stones	0.685	2	0.044	2
Rectangular	Concrete form stones	0.498	3	0.984	7
Square	Concrete form stones	0.493	4	1.000	8
Square	Unvarnished ceramic	0.426	5	0.500	3
Rectangular	Unvarnished ceramic	0.426	6	0.504	4
Rectangular	Varnished internal ceramic	0.425	7	0.506	5
Square	Varnished internal ceramic	0.416	8	0.532	6

Source: Author’s contribution.

References

Authors

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Articles in this issue

DOI: https://doi.org/10.2478/acee-2026-0001 | Journal eISSN: 2720-6947 (formerly 1899-0142) | Journal ISSN: 1899-0142

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Language: English

Page range: 10 - 30

Submitted on: Aug 24, 2025

Accepted on: Sep 4, 2025

Published on: Aug 26, 2026

Published by: Silesian University of Technology

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

Chimney system optimization,

Chimney wall materials,

Energy efficiency in buildings,

Kesa-aladin software,

Machine learning,

TOPSIS-VIKOR methods

Related subjects:

Architecture and design,

Architecture,

Architects, buildings

© 2026 Figen Balo, Ahmet Karahan, published by Silesian University of Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Volume 19 (2026): Issue 1 (March 2026)

Enhancing sustainability of heating systems in humid regions: A framework for flue system design based on thermal-acoustic-aerodynamic performance

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