Sustainable energy devices such as light emitting diodes (LEDs), solar cells, and batteries are of great importance. LEDs and solar cells, being reliable and clean energy sources, are important for the future. Batteries are very important energy storage devices.
It is therefore of great importance that these devices be utilized to their maximum efficiency. Unfortunately, one of the major drawbacks of these devices is that energy in the form of heat, or, thermal energy, is dissipated which reduces the efficiency, lifespan, and reliability of these devices.
It makes sense to look into this matter as a 10-degree Celsius increase in the junction temperature of LEDs, above its threshold temperature, that reduces its lifespan by about 50 percent. Solar cells need to be cooled as the concentration of light on the solar cells raises their temperature significantly and causes 20 to 25 percentage loss in photovoltaic efficiency. Thermal management of batteries too is important as heat affects the performance and reduces the lifespan of the batteries.
Ways to cool sustainable energy devices include convection of gases and liquids, and liquid-vapour phase change. Of these, liquid-vapour phase change is the preferred cooling technique. This is because of its large latent energy.
Usually heat pipes and devices known as thermosyphons are used in the liquid-vapour phase cooling method. Also advantageous is the fact that these devices do not need external power for working fluid transport.
Thermosyphons work on the principle of gravity. Normal cylindrical thermosyphons have three sections – a condenser, an adiabatic, and an evaporator section. Vapour and liquid form of the working fluid circulate through the system and causes cooling of the device.
Until now, only cylindrical and loop thermosyphons have been used and studied. To the best of this paper’s authors’ knowledge, the concept of a flat thermosyphon has not been considered.
Mr. Praveen Dhanalakota 
Mr. Laxman Kumar Malla 
Mr. Hemanth Dileep 
Prof. Pallab Sinha Mahapatra 
Prof. Arvind Pattamatta
In this paper, the authors, which include Mr. Praveen Dhanalakota, Mr. Laxman Kumar Malla, Mr. Hemanth Dileep, Prof. Pallab Sinha Mahapatra, and Prof. Arvind Pattamatta, from the Department of Mechanical Engineering. Indian Institute of Technology (IIT) Madras, Chennai, India, use and study a compact flat thermosyphon (CFT) to be used as a potential heat transfer device for the effective thermal management of multiple heat sources.
This is a comprehensive, experimental and numerical study that is performed to investigate the thermal performance of a two-phase horizontal CFT. The CFT is manufactured with copper.
The following factors were taken into consideration for the CFT – the filling ratio of the working fluid, i.e. acetone, ethanol, water (20 percent, 50 percent, 80 percent), the number of heat sources, and the condenser surface wettability.
The best filling ratio of the working fluid was found to be 50 percent. The best working fluid was found to be water. This is because of its high heat capacity, latent heat, and low vapour pressure. Up to 4 heat sources of size 12 x 24 mm2 area could be cooled safely by the CFT. It was also found that the lifespan of the devices could be increased by using the CFT to cool multiple sources instead of a cold plate. The superhydrophobic condenser surface used also improved the thermal performance of the CFT.
Thus it was proven in this study that a compact flat thermosyphon (CFT) could be used for the effective thermal management of multiple heat sources in sustainable energy devices like LEDs, solar cells, and batteries. Future studies could involve experimental studies on CFTs with multiple heat sources and superhydrophobic condenser surfaces under cyclic heat load conditions.
Dr. Srikanth Rangarajan, Assistant Research Professor and Research Scientist from the Department of Mechanical Engineering, Binghamton University, State University of New York, appreciated the importance of this work by giving the following comments: “Heterogeneous integration (HI) is a promising method for the next-generation electronic systems to sustain Moore’s law by combining multiple functionalities into a single module/package. HI has translated to multi-chip modules with differentially heated zones in real-time products. Thermal management of such multi-chip modules is essential for improved reliability of next-generation electronic devices. This recent article by Prof Arvind Pattamatta and his team has proposed an energy-efficient passive thermal management solution for multi-chip modules. The work is timely and advances the state of the art of thermal management technologies. Furthermore, Prof. Arvind Pattamatta is one of the world leaders in developing advanced and energy-efficient thermal management technologies for energy-intensive electronics. The compact flat thermosyphon (CFT) solution proposed in this manuscript significantly contributes to the sustainable energy-smart next-generation electronic systems.”
Article by Akshay Anantharaman
Here is the original link to the paper:
https://www.sciencedirect.com/science/article/abs/pii/S0196890422008317
