Thermal Properties of Ionic Liquids and Ionanofluids

The current world economy and energy situation demands the search for alternative energies to conventional fuels, the optimization of current energy technologies, and the search for new and clean working fluids. In the field of heat transfer, all current liquid coolants used at low and moderate temperatures exhibit very poor thermal conductivity and heat storage capacities, as the classical equipments for heat transfer use working fluids that were developed, tested and applied in a world of positive economical growth. In contrast, the uses of chemical technologies today are considered unsustainable. Although increased heat transfer can be achieved creating turbulence, increasing surface area and so on, ultimately the transfer will still be limited by the low thermal conductivity of the conventional fluids. Therefore, there is a need for new and efficient heat transfer liquids that can meet the cooling challenges for advanced devices as well as energy conversion for domestic and industrial applications. Ionic liquids (IL) have proven to be safe and sustainable alternatives for many applications in industry and chemical manufacturing. Their success arises mainly from their thermophysical and phase-equilibria properties, and the versatility of their synthesis, manageable to be tailored for a given application. Their solvent properties as well as their heat transfer or heat storage and surface properties make this class of fluids possible to use in a high plethora of applications (Earle & Seddon, 2007; Nieto de Castro & Santos, 2007). Other advantages of ionic liquids include high ionic conductivity, high chemical and thermal stabilities, negligible vapor pressure and an ability to dissolve a wide range of inorganic and organic compounds. Due to all of these fascinating characteristics they have been investigated extensively as alternatives to molecular solvents for liquid phase reactions (Wasserscheid & Welton,2007; Pârvulescu & Hardacre, 2007). Ionic liquids are of great interest to scientists as well as chemical companies, not only because of their interesting properties, but also for their actual and potential applications in the chemical process industries. In the past, the values of their thermophysical properties found to have significant effect on the design of physico-chemical processing and reaction units, influencing directly the design parameters and performance of equipments like heat exchangers, distillation columns and reactors (Franca et al., 2009). Their thermophysical properties justify the replacement of several of the chemical processes now under exploitation, and some of the solvents used, because they can, in certain conditions, be