Thermal Performance Analysis of a Closed-Loop Thermosyphon Using Ethanol and Acetone as Working Fluids

Abstract

Closed-loop thermosyphons (CLTs) are widely used in thermal management systems due to their efficient passive heat transfer capabilities. However, achieving optimal performance is challenging due to the complex relationship between working fluid properties, heat input, vapor (adiabatic) length, and filling ratio, all of which significantly impact thermal resistance and heat transfer characteristics. The lack of a comprehensive parametric investigation limits the ability to develop high-efficiency thermosyphon designs for advanced thermal applications. This study systematically examines the thermal performance of a CLT using ethanol and acetone as working fluids. The effects of heat input (0.5–2.0 kW), vapor (adiabatic) lengths (200, 500, and 800 mm), and filling ratio (0.3–0.7) are analyzed to assess their impact on thermal resistance and heat transfer characteristics. A parametric investigation is conducted to evaluate thermal resistance, evaporator and condenser heat transfer coefficients, and overall thermal effectiveness. A numerical model based on empirical correlations is developed and validated against experimental data for improved predictive accuracy. Results indicate that thermal resistance decreases with increasing heat input, leading to enhanced heat transfer efficiency. The selection of ethanol or acetone significantly influences system performance, with optimal filling ratios improving heat transfer characteristics. The vapor (adiabatic) length plays a critical role in system behavior, affecting overall heat transport capability. The developed numerical model exhibits strong agreement with experimental data, offering a reliable predictive tool for optimizing thermosyphon design. These findings contribute to the advancement of high-efficiency CLT systems for industrial and electronic cooling applications.