Executive Summary : | IIT Patna proposes to develop a high heat dissipation boiling module. Specifically, we propose to demonstrate heat transfer coefficient (HTC) values large than 90 kW/m²-K while ensuring a very high critical heat flux (CHF) value in excess of 1.5 MW/m². As a reference, these numbers imply a 100% enhancement in HTC and around 50% enhancement in CHF in comparison to the standard case of boiling with water typically used in practical applications. We propose to achieve this metrics via the use of ionic liquids (ILs) as additives in water. ILs basically are molten salts typically liquid at room temperature. They have a very low vapor pressure, are non-volatile, non-flammable, and stable at higher temperatures. Due to these properties, they have emerged as a potential replacement of surfactants in various applications such as enhanced oil recovery, separation science, and biomedical applications such as drug delivery, among others. In particular, ILs containing longer alkyl chain belong to an important category of amphiphiles known as surface-active ionic liquids (SAILs). SAILs exhibit better surface activity compared to conventional surfactants containing the same alkyl chains. To the best of our knowledge, ours is the first group to demonstrate the potential of surface-active ionic liquids for improving the energy efficiency of boiling based energy and thermal management systems. Our preliminary experimental results published in the Journal of Molecular Liquids demonstrate that ionic liquid additives in water can simultaneously enhance the HTC and the CHF in comparison to surfactants. Our characterization efforts attribute this promising trend to the improvement in surface wettability due to the deposition of ionic liquids on the boiling surface. Please note that this trend is diagonally opposite to what is typically observed with surfactant solutions. While the HTC was also larger in comparison to the baseline case of boiling with pure water, a slight deterioration in CHF was however reported. In this proposed project, we intend to explore many of this new class of additives to explore the area of simultaneous fluid and wettability modification. The eventual aim is to tune this strategy to facilitate simultaneous HTC and CHF enhancement even in comparison to the boiling with pure water. We believe that the outcomes from this project will enable the development of a novel heat dissipation strategy for energy efficient boiling systems. Such steps are crucial to minimize the burden on our energy resources for ensuring a sustainable future. |