A growing challenge in modern electronics, electric vehicles and space systems is how to manage heat efficiently when multiple components generate heat simultaneously.
In a loop heat pipe (LHP), the heat causes the working fluid to vaporise in the evaporator. The gas formed then flows to the condenser, where it condenses as heat is removed by the radiator, before being circulated back to the evaporator mainly through capillary action. Therefore, there is no need for pumps or compressors, making it a much simpler system that other cooling devices. They are commonly used in satellite applications for cooling electronic equipment.
Traditional LHPs have a single evaporator, and struggle to handle uneven or complex heat sources, leading to reduced performance or system failure. In this study, published in the International Journal of Heat and Mass Transfer, the researchers investigated a dual-evaporator loop heat pipe (DE-LHP) system. This was designed to efficiently manage multiple heat sources, like those present in advanced electronics and electric vehicle battery systems.
The research group from Indonesia came to ISIS to use the neutron radiography capability on IMAT, supported by beamline scientist Ranggi Ramadhan. This meant they could study the dynamics of the working fluid in their DE-LHP during startup and operation, revealing key performance-limiting phenomena such as vapor backflow and liquid carryover.
Neutrons are highly sensitive to hydrogen, making them excellent at detecting the working fluid, which in this case is deionised water, even when it's hidden inside the metal components of the DE-LHP. Unlike X-rays, neutrons can pass through thick metals like copper and stainless steel, enabling the group to observe the system in real-time without modifying it to make it transparent. The ISIS Electrical and Electronic User Support Group and the Pressure and Furnace team were also involved in the preparation of the experiment.
Neutron imaging helped them to identify when the vapour was moving in the wrong direction, when any liquid went into the vapor line, if there were any heat leaks through components and any incomplete fluid evaporation and condensation.
“Our results show that a balanced heat input significantly improves system stability and thermal efficiency, achieving a low thermal resistance," explains Professor Nandy Putra from the University of Indonesia. “In contrast, uneven heat distribution leads to incomplete startup and higher thermal resistance," he adds.
They also found that system orientation plays a vital role, with slight tilts helping reduce flow disturbances. Their DE-LHP demonstrated effective operation without needing help from gravity, highlighting its potential for compact and orientation-independent thermal management applications.
“In the future, one key direction for the research is the development of improved wick structures with optimised porosity and permeability to minimise issues like liquid carryover and vapor backflow," says Professor Putra. “Additionally, refining the working fluid filling ratio could help enhance startup stability and heat transfer efficiency."
The group also plan to integrate computational tools such as computational fluid dynamics and machine learning to predict the system behaviour more accurately.
The visit by the
Indonesian research team was partly supported by the International Science
Partnerships Fund (ISPF) and the full research can be found at DOI: 10.1016/j.ijheatmasstransfer.2025.127053
