Session: K10-02: Heat transfer equipment

Paper Number: 184339

184339 - CFD-Based Thermal Hotspot Identification and Mitigation in V-Shaped Air-Cooled Condenser Coils 

Abstract: 

Expanded Abstract (500 Words)

Thermal hotspot identification and mitigation in air-cooled condenser systems represents a critical engineering challenge that directly impacts system reliability, energy efficiency, and operational costs in industrial refrigeration and HVAC applications. Under extreme ambient conditions characteristic of desert and tropical climates—where outdoor temperatures routinely exceed 50°C—conventional air-cooled heat rejection equipment experiences severe performance degradation. These harsh environmental conditions impose extraordinary thermal loads that lead to localized overheating, accelerated component fatigue, refrigerant-side pressure elevation, and catastrophic reductions in system Coefficient of Performance (COP). Field observations indicate that poorly designed condenser assemblies operating in such climates can experience COP reductions exceeding 25-30% compared to rated performance, alongside significantly increased compressor discharge pressures that threaten mechanical integrity and shorten equipment lifespan. The economic consequences of this thermal management failure include elevated energy consumption, frequent maintenance interventions, and premature system replacement—challenges that are particularly acute in regions experiencing rapid infrastructure development and increasing cooling demand.

This study addresses these operational challenges through a comprehensive three-dimensional Computational Fluid Dynamics (CFD) investigation specifically focused on V-configured condenser coil assemblies, which are widely deployed in large-capacity cooling systems due to their compact footprint and enhanced air-side heat transfer characteristics. The numerical framework employs advanced turbulence modeling techniques, specifically the k-ω SST (Shear Stress Transport) turbulence model selected for its superior accuracy in predicting flow separation and adverse pressure gradient effects that dominate recirculation zones within V-geometry heat exchangers. The simulation methodology integrates conjugate heat transfer analysis to capture thermal conduction through tube walls and fin structures, coupled with detailed refrigerant-side boundary conditions representing two-phase condensation processes including desuperheating, phase-change heat transfer, and subcooling zones. Mesh independence studies and validation against experimental correlation data established solution accuracy within 5% for local heat transfer coefficients and 3% for overall pressure drop predictions.

Simulation results reveal pronounced non-uniform temperature distributions across the V-shaped coil geometry, with critical hotspots forming at specific locations influenced by complex interactions between airflow recirculation patterns, refrigerant maldistribution effects, and localized heat flux intensities. Thermal mapping identified peak coil surface temperatures exceeding 85°C in baseline configurations—temperatures that surpass material degradation thresholds and approach refrigerant critical pressure conditions. These thermal anomalies concentrate primarily in three distinct regions: the apex junction where upstream and downstream coil banks meet and create stagnant air pockets; outer peripheral zones experiencing reduced air velocity and diminished convective heat transfer coefficients below 30 W/m²·K; and tube-row transitions where boundary layer separation disrupts effective surface utilization. Flow visualization demonstrates that these hotspots correlate strongly with areas exhibiting air-side Reynolds numbers below 3,000, indicating transitional flow regimes with degraded heat transfer performance.

Detailed parametric optimization studies systematically evaluated geometric modifications including apex angle variation (60° to 90°), enhanced fin density distributions (8 to 14 fins per inch), strategic tube spacing adjustments, and targeted surface area augmentation in thermally deficient regions. Results demonstrate that optimized configurations incorporating a 75° apex angle, variable fin spacing with increased density at peripheral zones, and 15% additional surface area allocation reduce peak temperatures by 18-22°C while improving system COP by 14-17% under 50°C ambient conditions. Pressure drop penalties remained within acceptable limits at 8-12% increases. This CFD-based diagnostic and optimization methodology provides quantitative design guidelines for developing thermally robust condenser systems capable of sustained operation in the world's harshest climates, with direct applications in petrochemical facilities, data centers, and commercial buildings in extreme-climate regions.

Presenting Author: Ali Al-Hinaai Sultan Qaboos University

Presenting Author Biography: N/A

Authors:

Ali Al-Hinaai Sultan Qaboos University
Khalid Al Yahyai Sultan Qaboos University
Moosa Al-Kharusi Sultan Qaboos University