Experimental Analysis of a Dual-Evaporator Thermosyphon Cooling System for CPUs and GPUs

Thermosyphon cooling systems have great potential to be widely adopted for electronics cooling applications. They combine highly effective heat transfer with passive circulation triggered by the density difference between the liquid and vapour phases. It is not uncommon to have several processing units on a single motherboard, such as the Central Processing Units (CPUs) and Graphics Processing Units (GPUs) in electronic devices, such us desktop computers, servers, telecommunications equipment, etc. Thus, designing a thermosyphon cooling system with multiple evaporators and a single condenser is critical for practical implementations and broad market adoption. In this study, a thermosyphon-based system composed of two evaporators and a single air-cooled condenser is designed and tested for the layout of a desktop computer, removing heat from a CPU and a GPU. Specifically, the vertical CPU evaporator occupies the highest position, while the GPU evaporator is horizontal and located at the bottom of the loop. Both evaporators are in a parallel scheme in the proposed thermosyphon design. The total power dissipation of the thermosyphon-based system is 650 W and is split nonuniformly between the two evaporators (CPU power of 350 W and GPU power of 300 W). The results show that the thermosyphon can effectively cool both processing units without instabilities, with an overall thermal resistance varying between 0.055 and 0.061 K/W in steady-state operating conditions. Overall, the results demonstrate a thermosyphon system’s feasibility, reliability, and high efficiency in a dual-evaporator configuration as a starting point for future and more complex hardware arrangements.