Research

We are an interdisciplinary research group that focuses on several aspects of nanotechnology (environmental, economical, health and medical) as well as its applications in various fields such as energy sustainability and improvement in efficiency of existing systems with the overall aim of improving the living standards of societies. Details of some of the specific projects/papers that our group is currently working/has worked recently:

Radiative Heat Transfer Within Nanofluids

Dispersing trace amounts of nanoparticles into the base-fluid has significant impact on the optical as well as thermo-physical properties of the base-fluid. This characteristic can be utilized in effectively capturing as well as transporting the solar radiant energy. Enhancement of the solar irradiance absorption capacity of the base fluid scales up the heat transfer rate resulting in higher and more efficient heat transfer. In order to theoretically analyze the nanofluid-based concentrating parabolic solar collector is being mathematically modeled, and the governing equations are numerically solved using finite difference technique. The results of the model will be compared with the experimental results of conventional concentrating parabolic solar collectors under similar conditions as well as with actual parabolic trough collectors operating with nanofluids (direct absorption).

Design and Analysis of Parabolic Trough Collectors Using Nanofluids

The actual operation of a nanofluid-based collector entails a lot of preparation as well as careful measurements. The primary objective is to absorb sunlight directly within the absorber tube which contains the nanofluid. Once the nanofluid is heated to a sufficient temperature its thermal energy may be put to use for various applications. Research is being conducted to improve the overall efficiency as well as the output temperature of nanofluid based solar collectors. At the same time several liquids are being studied which may withstand very high temperatures day after day and do not disintegrate. Such liquids may consists of high temperature heavy oils or molten salts, with the primary concern that the nanoparticle remain suspended during the operation period.

Applications of Solar Energy (Air Conditioning, Water Desalination)

A solar-energy based vapor absorption refrigeration system is potentially an excellent alternative air-conditioning system. However, there are several research challenges to ensure sufficient efficiency and reliability for ensuring widespread implementation. Integration of a parabolic trough solar collector utilizing a mixture of nanoparticles and water with a vapor absorption system has the potential to significantly enhance the efficiency of the system. Such a system makes use of the superior thermo-physical properties of the nanofluid compared to the base fluid. Moreover, the direct absorption phenomenon of solar radiation through interaction with the participating medium (nanofluid) results in a higher temperature rise of the medium in conjunction with higher operating efficiencies as well. At the same time there are certain challenges that need to be identified and addressed in the implementation of this novel concept. For instance, to make it reliable, the system further needs to be integrated with a thermal storage system which facilitates air-conditioning even during non-sunshine hours. Integration of vapor absorption refrigeration technology, parabolic trough with water-nanoparticles mixture as the absorbing medium and a thermal storage facility is the uniqueness of this design which under certain conditions and locations may prove to be an efficient and reliable substitute to the conventional electrical air-conditioning systems.

Heat Transfer Applications in Biological Systems

Thermal therapy, involving exchange of heat with body tissues, has numerous clinical applications. One especially promising application is hyperthermia or thermal ablation. Hyperthermia can be used alone or in combination with other standard modalities such as radiotherapy and chemotherapy. Cancer cells are prone to preferential heating as compared to normal cells due to hypoxia and low pH content. For these treatments, nanotechnology can play an important role. Preferential heating of tumor region can be enhanced by utilizing light absorbing nanoparticles. Nanoparticles of different material, size and shape are currently being used for this purpose, examples include: gold nanoshells, gold nanorods (GNR), carbon nanotubes and gold nanocages. Thermal therapy, using light absorbing nanoparticles, is sometimes referred to as 'plasmonic photothermal therapy' as it makes use of plasmonic properties of nanoparticles and serves to distinguish it from conventional photothermal therapy (without nanoparticles). Gold is the material of choice as it is biocompatible and its toxicity has been studied. The primary concern in this field is the development of numerical models and tools to predict the methodology of application of hyperthermia which would result in maximum tumor ablation as well as highest amount of healthy tissue sparing.

Ignition Properties of Fuels Containing Nano-Particles

The addition of nanoparticles to solid fuels and propellants offers multiple advantages such as shortened ignition delay, increased energy density, and high burn rates. It is also observed that addition of nanoparticles to a fluid can enhance its physical properties. As a result, it is possible in principle to achieve the desired properties of a fluid by adding some specifically tailored nanoparticles. Since the nanoparticles are small enough to approach molecular dimensions, their properties can be significantly different from those of larger, micrometer-sized particles. At such dimensions, the surface-area-to-volume ratio of the particle increases considerably and hence allow more fuel to be in contact with the oxidizer.Furthermore, because of the small distances (interparticle as well as particle size) involved with nanoparticles, the time scales of the chemical reactions are very different compared with those associated with larger size particles, and as a result, the ignition delay time for nanosized particles would be much shorter than those of micrometer-sized particles.

Design of Cooling Systems for High-Heat-Flux Miniature electronics

The removal of very high-heat fluxes, up to 1000 W/cm², is increasingly being required by several electronics applications. At the same time it is generally desired that the electronic device temperature may be maintained below some threshold value (usually at less than 65^oC). The combination of an extremely high-heat flux removal and low device temperatures necessitates the use of refrigeration to maintain satisfactory performance. In order to cool the electronic component (chip), several types of refrigeration cycles may be utilized. To being with an evaporator is placed in thermal contact with the chip. This evaporator contains microchannels through which subcooled refrigerant flows. This way the heat from the chip is removed by boiling the refrigerant (R-134a) flowing through the evaporator.