Debendra K. Das

Specific Heat Measurement of Three Nanofluids and Development of New Correlations

This paper presents the specific heat measurements of three nanofluids containing aluminum oxide, zinc oxide, and silicon dioxide nanoparticles. The first two are dispersed in a base fluid of 60:40 by mass of ethylene glycol and water (60:40 EG/W) and the last one in deionized water. Measurements were conducted over a temperature range of 315–363 K, which is the normal range of operation of automobile coolants and building heating fluids in cold regions. The nanoparticle volumetric concentrations tested were up to 10%. The measured values were compared with existing equations for the specific heat of nanofluids. A close agreement with the experimental data was not observed. Therefore, a new general correlation was developed for the specific heat as functions of particle volumetric concentration, temperature, and the specific heat of both the particle and the base fluid from the present set of measurements. The correlation predicts the specific heat values of each nanofluid within an average error of about 2.7%.

Convective Heat Transfer and Fluid Dynamic Characteristics of SiO2 Ethylene Glycol/Water Nanofluid

Nanofluids comprised of silicon dioxide (SiO2) nanoparticles suspended in a 60:40 (% by weight) ethylene glycol and water (EG/water) mixture were investigated for their heat transfer and fluid dynamic performance. First, the rheological properties of different volume percents of SiO2 nanofluids were investigated at varying temperatures. The effect of particle diameter (20 nm, 50 nm, 100 nm) on the viscosity of the fluid was investigated. Subsequent experiments were performed to investigate the convective heat transfer enhancement of nanofluids in the turbulent regime by using the viscosity values measured. The experimental system was first tested with EG/water mixture to establish agreement with the Dittus-Boelter equation for Nusselt number and with Blasius equation for friction factor. The increase in heat transfer coefficient due to nanofluids for various volume concentrations has been presented. Pressure loss was observed to increase with nanoparticle volume concentration. It was observed that an increase in particle diameter increased the heat transfer coefficient. Typical percentage increases of heat transfer coefficient and pressure loss at fixed Reynolds number are presented.

Density Measurement of Different Nanofluids and Their Comparison With Theory

Abstract Density measurements were performed on three different nanofluids containing aluminum oxide (Al2O3), antimony-tin oxide (Sb2O5:SnO2), and zinc oxide (ZnO) nanoparticles in a base fluid of 60:40 ethylene glycol/water by mass. First, a benchmark test for the density of the base fluid is presented showing excellent agreement with the data presented in the handbook of the American Society of Heating, Refrigerating, and Air Conditioning Engineers. Next, density measurements of the above-mentioned nanofluids over a temperature range of 0°C to 50°C for several particle volume concentrations are presented. These measured results were compared with a widely used theoretical equation and good agreements between the theoretical equation and measurements were obtained for the Al2O3 and Sb2O5:SnO2 nanofluids. However, the deviation was observed to be higher with the ZnO nanofluid and it increased with particle volume concentration.

Determination of Rheological Behavior of Aluminum Oxide Nanofluid and Development of New Viscosity Correlations

Abstract Experimental investigations have been carried out to study the rheological behavior of aluminum oxide nanofluid. Nanoparticles with average particle size of 53 nm were dispersed in a base fluid of 60% (by mass) of ethylene glycol and water. Nanofluids of volumetric concentrations 1 to 10% were tested for determining the viscous properties. It was found that this nanofluid behaved as non-Newtonian at lower temperatures (-35°C to 0°C) and Newtonian at higher temperatures (0°C to 90°C). The data showed that the viscosity increases with an increase in concentration and decreases with increase in temperature. Two new correlations were developed expressing viscosity as a function of temperature and concentration.

Measurement of the Thermal Conductivity of Silicon Dioxide Nanofluid and Development of Correlations

Experimental investigations were carried out for the determination of thermal conductivity of silicon dioxide (SiO2) nanoparticles dispersed in 60% ethylene glycol and 40% water by mass. Experiments conducted in a temperature range of 20 C to 90 C and for several particle volumetric concentrations up to 10% showed that the ratio of thermal conductivity of nanofluid to that of the base fluid increased with an increase in temperature and volumetric concentration. As an example, as much as a 20% enhancement in thermal conductivity was evidenced for a particle volumetric concentration of 10% at 87 C. Comparison of experimental results of this nonmetallic nanoparticles suspension with the well-known model developed by Hamilton and Crosser for microparticles suspensions, exhibits that this model underpredicts the thermal conductivity of nanofluids. Therefore, a new correlation has been derived following recent models developed for metallic nanoparticles suspensions, which is a combination of the Hamilton–Crosser model plus a term due to the Brownian motion. This new correlation expresses the thermal conductivity of silicon dioxide nanofluid as a function of temperature, volumetric concentration and the properties of the base fluid and the nanoparticles. [DOI: 10.1115/1.4024003]

Superior Performance of Nanofluids in an Automotive Radiator

This study compares the performance of three different nanofluids containing aluminum oxide, copper oxide, and silicon dioxide nanoparticles dispersed in the same base fluid, 60:40 ethylene glycol and water by mass, as coolant in automobile radiators. The computational scheme adopted here is the effectiveness-number of transfer unit (e − NTU) method encoded in matlab. Appropriate correlations of thermophysical properties for these nanofluids developed from measurements are summarized in this paper. The computational scheme has been validated by comparing the results of pumping power, convective heat transfer coefficients on the air and coolant side, overall heat transfer coefficient, effectiveness and NTU, reported by other researchers. Then the scheme was adopted to compute the performance of nanofluids. Results show that a dilute 1% volumetric concentration of nanoparticles performs better than higher concentration. It is proven that at optimal conditions of operation of the radiator, under the same heat transfer basis, a reduction of 35.3% in pumping power or 7.4% of the surface area can be achieved by using the Al2O3 nanofluid. The CuO nanofluid showed slightly lower magnitudes than the Al2O3 nanofluid, with 33.1% and 7.2% reduction for pumping power or surface area respectively. The SiO2 nanofluid showed the least performance gain of the three nanofluids, but still could reduce the pumping power or area by 26.2% or 5.2%. The analysis presented in this paper was used for an automotive radiator but can be extended to any liquid to gas heat exchanger.

Measurements of pH of Three Nanofluids and Development of New Correlations

In this study the pH levels of aluminum oxide (Al2O3), silicon dioxide (SiO2), and zinc oxide (ZnO) nanoparticles dispersed in propylene glycol and water mixture were measured in the temperature range of 0°C to 90°C. The volumetric concentration of nanoparticles in these fluids ranged from 0 to 10% for different nanofluids. The average particle sizes (APS) considered were from 10 nm to 70 nm. The pH measuring apparatus and the measurement procedure were validated by measuring the pH of a calibration fluid, whose properties are known accurately. The measured pH values agreed within less than ±0.5% with the published data reported by the manufacturer. Following the validation, the pH values of different nanofluids were measured. The measurements showed that pH of nanofluids decreased with an increase in temperature and increased with an increase in particle volumetric concentration. For the same nanofluid at a fixed volumetric concentration, the pH was found to be higher for larger particle sizes. From the experimental data, empirical models were developed for three nanofluids to express the pH as functions of temperature, volumetric concentration, and the size of the nanoparticles.

Design, construction and testing of a low‐cost hybrid rocket motor

Small hybrid rocket motors using solid propellant and gaseous oxidizer are becoming increasingly popular as a propulsion device. This paper describes the development of a one‐dimensional flow model for the design of a small rocket motor. Combustion of polyethylene as solid propellant with oxygen is used as a candidate hybrid fuel to test and evaluate the performance of this hybrid system. To assess the performance under different operating conditions, a computer program has been developed, which facilitates inputs to be varied and effects assessed. A system of governing equations is summarized in the main body of this paper and is numerically solved by the computer program. The results of the modelling are then used to design and build a small low‐cost rocket motor for experimental verification. Therefore, the materials presented herein could be used in the future design of hybrid rocket motors.

Measurements of Specific Heat and Density of Al2O3 Nanofluid

This paper presents measurements of specific heat and density of aluminum oxide (Al2O3) nanoparticles suspended in 60:40 (by mass) ethylene glycol and water mixture (EG/W). These property values are necessary to determine the fluid dynamic and heat transfer characteristics of nanofluids. These properties have been measured over a range of temperatures for nanoparticle volumetric concentrations of 0 to 10%. From the experimental results, empirical correlations have been developed as a function of temperature and particle volume concentration. These correlations will be valuable in studying the heat transfer performance and the pumping power requirement of Al2O3 nanofluid in various applications such as industrial heat exchangers, building heating and automotive cooling.

A Computational Scheme for Fluid Flow and Heat Transfer Analysis in Porous Media for Recovery of Oil and Gas

Abstract A finite-element scheme has been formulated, which is capable of solving transient analysis of both conductive and convective heat transfers due to fluid flow in porous media. The model also includes the latent heat effect to consider the phase change aspect of a frozen medium. To test the validity of the model, it was applied to six cases for which analytical solutions are available. The test cases cover (i) single-phase fluid flow through porous media, (ii) radial conduction with and without phase change, (iii) conductive and convective heat transfer in an aquifer, and (iv) two-phase immiscible flow in porous media. In all these cases, good agreement with analytical solutions are observed validating the computational scheme. This computational scheme should be useful in solving frozen ground problems, thermal stimulation technique for natural gas recovery from hydrates, and single-phase and two-phase convective heat transfer problems in enhanced oil recovery scheme in petroleum engineering.