Session: 11-16-02: Oscillating Heat Pipes and Thermosiphons

Paper Number: 109452

109452 - Thermal Analysis of Thermosyphon for Waste Heat Recovery From Auto Exhaust Using Limited Fluid Charge 

Internal combustion engine (ICE) cannot efficiently convert chemical energy into mechanical energy. Most of the energy is dissipated in the exhaust as wasted heat, which can be recovered through thermosyphons to heat the auto subsystem fluids, improving fuel efficiency and reducing emission. The thermosyphon is a wickless heat pipe that can transfer heat from its evaporator to its condenser through phase transition of a working fluid such as water inside the thermosyphon. In this work, an experimental and numerical study has been conducted to investigate the thermal performance of a thermosyphon for recovering waste heat from auto exhaust using limited fluid charge. The thermosyphon is made of Inconel alloy 625 because of its high thermal-fatigue strength and excellent corrosion resistance. The thermosyphon has an outer diameter of 1.05 inches, a thickness of 0.103 inches, and a total length of 19 inches, including a 7-inch evaporator, a 3-inch adiabatic section and a 9-inch condenser. The exhaust gas was blown onto the evaporator end cap at a flow rate of 10-100 g/sec at the temperature of 300-900°C. The effects of inclination angle (5°-45°), the amount of water mass (3g-5.3g) and the amount of non-condensable gas Argon (0g-0.6g) on the thermal resistance and response time of the thermosyphon were studied. The experimental results show that the maximum temperature of the condenser can reach around 200°C under the load of 3g water and 0.05g Argon in the thermosyphon. As the inclination angle increases, the amount of water flowing to the condenser increases, the temperature of the condenser decreases, and the thermal resistance of the thermosyphon increases. Reducing the amount of argon and increasing the amount of water shortened the response time but had little effect on the temperature of the condenser and the thermal resistance of the thermosyphon. Numerical analysis is performed to optimize the thermosiphon design and improve the thermal performance of the thermosiphon. The numerical model using VOF model in FLUENT is validated by the experimental results. The contours of boiling and evaporation profiles under different inclination angles, different amount of water and different thicknesses of the thermosyphon have been compared and analyzed. The temperature-based surface tension of the water on the inner wall of the thermosyphon is assumed in FLUENT. Axial and radial temperature gradient plots in the thermosyphon are presented for bettering understanding the heat transfer from the evaporator to the condenser due to the natural convection and boiling water convection. By comparing the thermal resistance and the response time of the thermosyphon under different working conditions, an optimized design of the thermosyphon is obtained.

Presenting Author: Bin Xiao Texas State University

Presenting Author Biography: Dr. Bin Xiao received a PhD degree in mechanical engineering from the University of Missouri at Columbia. Dr. Xiao joined the department of engineering technology at Texas State University as a full-time lecturer in Spring 2019. Prior to joining the Texas State University, he was a team leader at the Astronautics Corporation of America in Madison, Wisconsin. Dr. Xiao has over fifteen years of industry and academic experience in thermal-fluid science and has published more than twenty papers in the peer-reviewed journals and conferences.

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