A. D. Parekh

Bio: A. D. Parekh is an academic researcher from Sardar Vallabhbhai National Institute of Technology, Surat. The author has contributed to research in topics: Vortex tube & Vortex. The author has an hindex of 9, co-authored 21 publications receiving 314 citations.

Experimental, computational and optimization studies of temperature separation and flow physics of vortex tube: A review

Abstract: A vortex tube is a very simplistic device capable of producing phenomenal temperature separation effect. Due to spontaneity of this effect coupled with diversified applications, vortex tube has remained a topic of various research studies among the scientific community. To begin with the research work, it is essential for a researcher to get acquainted with previous investigations carried out in the relevant domain. Hence, present review is intended to put-forward the experimental and numerical (or Computational Fluid Dynamics i.e. CFD) work carried out by various researchers. Also, review of various optimization studies using techniques such as Artificial Neural Network (ANN), Taguchi method is presented, which have not received due attention previously. The core objective is to give deliberate consideration to quality outcomes of fewer unattended research work on vortex tube.

Nanorefrigerants: A comprehensive review on its past, present and future

Abstract: Nanofluid as a heat transfer fluid has been gaining popularity ever since its inception. Consequently, the researchers and experimentalists from the refrigeration industry could not keep themselves away from the ever growing horizon of nanofluid applications. The research on the refrigerant based nanofluids or a nanorefrigerant is slowly but surely increasing. The boiling heat transfer coefficient data for nanofluids and nanorefrigerants have been inconsistent but, in general, researchers have observed a rise in the boiling heat transfer coefficient that encourages them to pursue their research further in this field. Numerous studies regarding nanorefrigerants have shown that the addition of nanoparticles lead to a better system performance and energy efficiency. This review paper is an attempt to summarise all the aspects of nanorefrigerants such as its preparation, thermophysical properties, pressure drop in nanorefrigerants, boiling heat transfer and performance of nanorefrigerants in various domestic refrigerators.

Experimental investigation of a vapour compression refrigeration system using R134a/Nano-oil mixture.

Abstract: The current research is focused on the application of nanoparticles in vapour compression refrigeration systems. The major aim of the study is to investigate the effects of nano-oil on various performance parameters of the vapour compression refrigeration systems such as refrigeration capacity, compressor power, compressor discharge temperature and last but not the least, the coefficient of performance (COP) of the refrigeration system. Nano-oil was prepared by dispersing Al2O3 nanoparticles in PAG oil. Al2O3 nanoparticles were chosen because of aluminium oxide's superior thermophysical properties and a low dielectric constant in comparison to other commonly used nanoparticles such as CuO and TiO2. The above-mentioned performance parameters were compared for broadly two different cases, viz., VCRS working on R134a/PAG mixture and VCRS working on R134a/PAG/Al2O3 (R134a/nano-oil) mixture. The system analysis was conducted at several evaporator temperatures ranging from -11 °C to 1 °C and at two different condenser temperatures, viz., 30 °C and 34 °C. The dispersion of nanoparticles into the compressor oil resulted in a higher degree of subcooling at the condenser exit. It was also found that the COP of the system increased by as much as 6.5 % due to the addition of nanoparticles in the system.

Thermal conductivity of nanoparticle suspensions

Abstract: We describe an optical beam deflection technique for measurements of the thermal diffusivity of fluid mixtures and suspensions of nanoparticles with a precision of better than 1%. Our approach is tested using the thermal conductivity of ethanol-water mixtures; in nearly pure ethanol, the increase in thermal conductivity with water concentration is a factor of 2 larger than predicted by effective medium theory. Solutions of C60–C70 fullerenes in toluene and suspensions of alkanethiolate-protected Au nanoparticles were measured to maximum volume fractions of 0.6% and 0.35vol%, respectively. We do not observe anomalous enhancements of the thermal conductivity that have been reported in previous studies of nanofluids; the largest increase in thermal conductivity we have observed is 1.3%±0.8% for 4nm diam Au particles suspended in ethanol.

Improving the performance of refrigeration systems by using nanofluids: A comprehensive review

Abstract: In view of energy security and environmental concern, the performance of refrigeration system needs to be improved, which can be done by modifying either the systems or the properties of primary and secondary working fluids. Recently, the nanofluids or hybrid nanofluids have gained interest in many engineering fields due to its excellent thermophysical properties, which can be easily used in refrigeration and air conditioning systems by many roles for performance improvement. This review summarizes the researches on preparation and characterization of nanofluids, various thermophysical and electrical properties (density, heat capacity, viscosity, thermal conductivity, surface tension, electrical conductivity, freezing characteristics, etc.) of nanofluids. Applications of nanofluids in the refrigeration systems as refrigerant, lubricant and secondary fluid are well-grouped and discussed. Finally, the challenges and opportunities for future research are identified, which will be useful for the newcomers and manufacturers in this field.

HFO refrigerants: A review of present status and future prospects.

Abstract: HFCs (Hydrofluorocarbons) are one of the most widely used refrigerants worldwide. But, HFCs are heading towards complete phase out in the near future due to environmental concerns. A high global warming potential (GWP) of HFCs is the main reason for its phase-out. As a result, researchers, engineers and technicians associated with the refrigeration sector are looking for a suitable environment-friendly alternative. Recent past has witnessed the emergence of a new group of environment-friendly refrigerants known as the HFOs (Hydrofluoro-olefins). The present review is focussed on addressing various aspects of HFO refrigerants such as the thermodynamic and transport properties, flammability and oil compatibility, boiling and condensation heat transfer performance and their performance in actual vapour compression refrigeration systems. Few suggestions for future research work related to HFO refrigerants are also discussed.