Theoretical analysis of compact heat exchanger using Nanofluids

Abstract

Cooling is indispensable for maintaining the desired performance and reliability of a wide variety of products, such as computers, car engines and high-powered laser. With the increase of heat loads and heat fluxes caused by more power and smaller sizes for these products, cooling is one of the top technical challenges faced by the industries like microelectronics, transportation, manufacturing, metrology and defense. Recently, single-phase liquid cooling techniques such as microchannel heat sink and two-phase liquid cooling technologies like heat pipes, thermosyphons, direct immersion cooling and spray cooling for chip or package level cooling have emerged. However, with continued miniaturization, increasing heat dissipation and inherently low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for ultrahigh-performance cooling in new generations of products. Therefore, the cooling issue will intensify in many industries from electronics and photonics to transportation, energy supply, defense and medical. Development of the nanomaterials technology has made it possible to structure a new type of heat transfer fluids formed by suspending nanoparticles (diameter less than 100nm) in conventional base fluids like water and ethylene glycol. Choi (1995) coined the term Nanofluids to refer to this new class of fluids that exhibits thermal properties superior to those of their base fluids. The nanoparticles suspended in a base liquid are in random motion under the influence of several acting forces, such as Langevin force which is a random function of time, and reflects the atomic structure of the medium. The exact role of this stochastic motion on the morphology of nanofluids and energy transport inside the nanofluids is not well understood. Due to rapid fluid mixing effects strengthens the energy transport inside the nanofluids by modifying the temperature profiles.