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Paper
Location:
DATE:
Paper: A loop heat pipe for vehicle CPU cooling: peak performance, partial flooding and dryout regimes.
On the 11 July 2022, Julio Ferreira from the University if Michigan presented a paper on using a loop heat pipe for vehicle CPU cooling, analysing the peak performance, partial flooding and dryout regimes. The paper was presented at the ASME Summer Heat Transfer Conference in Philadelphia, USA. The paper was a collaboration between the University of Michigan (UoM), General Motors (GM) and Calyos.
Calyos was responsible for the design and production of the loop heat pipe solution as per the specification created by the UoM and GM. The solutions was designed to cool two 480W processors, transporting the heat over two metres to a remote cold source. The goal of the project was to evaluate the feasibility of using loop heat pipes to cool processors used for Advanced Driver Assistance Systems (ADAS).
The UoM undertook extensive testing of the unit to validate the performance of the system in relation to Calyos' simulations. The UoM found that the final prototype very closely reflected the simulated performance by Calyos, validating the accuracy of Calyos' simulation tools.
People:
Julio Ferreira - University of Michigan
Massoud Kaviany - University of Michigan
Erik Yen - General Motors
Olivier de Laet - Calyos
Vincent Dupont - Calyos
Thomas Nicolle - Calyos
Abstract:
A Loop Heat Pipe (LHP) is assembled and tested for removing up to 400 W from two vehicle CPUs, while keeping their temperature under 95°C and using a 2 m-distanced, 45°C-air cooled condenser, and working fluid R1233zd(E). The capillary evaporator wick uses a liquid artery wick supplying liquid to a sawtooth copper wall evaporator. This novel sawtooth structure extends the evaporation area, spreads the liquid, and allows for the vapor escape space, while minimizing the evaporator resistance. For the application flexibility, it is preferred to place the condenser away from the CPUs. The air-cooled condenser fan-power consumption is also important, influencing the condenser thermal resistance. The loop thermal-hydraulics are analyzed (including the wick effective thermal conductivity, permeability, and maximum capillary pressure) and modeled. These include the role of the liquid accumulation on the evaporator, and the partial, local wick dryout under statistical variation in the microlayer wick thickness. The condenser thermal resistance and pressure drop, the transfer lines pressure drops, and the accumulator volume, which can dominate and limit the overall performance, are addressed in the design selection. The model predictions are compared with the performance of the fabricated LHP under variable thermal load and CPU-condenser separation distance. Good agreements are found, under partial flooding at low thermal load, under partial dryout at high thermal load, as well as under thermal loads with peak evaporator performance. Further improvements realized in the second-generation evaporator wick is expected to raise the peak performance and the maximum thermal load significantly.
Further reading:
Summer Heat Transfer ConferenceWho We Are
Calyos is a leader in the design and manufacture of two-phase thermal management systems. Building on our heritage from Euro Heat Pipes (EHP) and their space technology expertise, we specialize in innovative cooling solutions that tackle the thermal challenges of tomorrow.
What We Do
We engineer advanced cooling technologies, including loop heat pipes, micro-channel heat pipes, and pulsating heat pipes, to optimize thermal performance across a variety of applications. Typically these include: power electronics, processors, and batteries, but we don't stop there we are continuing to develop and produce fully customizable solutions for other specific needs, for example e-motors and fuel cells.
Where We Operate
Calyos is headquartered in Charleroi, Belgium, where our engineering and production teams work side by side in a state-of-the-art facility. From this base, we serve a global clientele, providing our cutting-edge solutions across North America, Asia, Europe, and South America.
When We Started
Calyos was incorporated in 2014 as a spin-off from Euro Heat Pipes (EHP), which was established in 2001 and has become a major player in the European satellite market. Since then, Calyos has been adapting and evolving EHP's space-grade cooling technologies for terrestrial applications.
Why We Matter
Our mission is to lead the industry towards adopting the most effective and sustainable thermal management solutions. We aim to address the most pressing thermal challenges in the data-driven and electrified environments of today, leveraging passive cooling technologies to achieve superior efficiency and environmental stewardship.
How We Succeed
Our success is driven by our commitment to four core values:
1. Applied Knowledge - Transforming deep technical expertise into market-ready solutions.
2. Better Together - Emphasizing collaboration with all stakeholders to enhance our collective success.
3. Inherent Flexibility - Adapting our solutions and practices to keep pace with evolving market demands.
4. Continuous Research - Persistently innovating to maintain our leadership in thermal technology.
Ben Sutton
Marketing & Business Development Manager
