Performance analysis of nanosilica-in-fluid dispersion (nanofluid) derived from rice hull ash as coolant in heat exchanger

Date

2016

Abstract

The development of performance-enhancing nano-materials from renewable, readily available sources for a variety of value-added applications is one attractive area of research in our institution. This study aimed to find alternative ways of enhancing the thermal properties of heat transfer fluids and to utilize agricultural by-products like rice hull ash (RHA), which has been proven to be viable and low-cost alternative source of nanosilica particles with 92.85% purity and 82% recovery. Fluids with nano-scaled particles form a stable suspension and provide impressive improvements in the thermal properties of base fluid s. The nanofluid was prepared by dispersing the nanosilica powder from the rice hull ash into deionized water and ethylene glycol:deionized water (EG:dW) mixtures (25:75, 50:50 and 75:25) as base fluids. AFM analysis of the nanosilica powder gave a size range of 46.5nm. The stability of the nanofluids based on sediment photography and UV-Vis spectrophotometry showed that 0.5% deionized water-based nanofluids was stable for 10 days and 0.25% of 50:50 EG:dW mixture-based nanofluids was stable and without significant sedimentation for 7 to 10 days compared to other EG:dW mixture-based nanofluids. Measured density of the nanofluids did not vary much relative to the base fluids. An increase in dynamic viscosity was observed in deionized water-based nanofluid by as much as 159.90%. it was observed that the 25:75 EG:dW ratio has the fastest flow rate while the 75:25 has the slowest. Thus, the concentration of ethylene glycol greatly affects the flow rate of the solution. Measured specific heat of the nanofluids formulated in different volume concentrations decreased compared to base fluids. The increase of thermal conductivity of water-based nanofluids compared to deionized water reached 45% after dispersing nanosilica powder at different volume concentrations measured at temperatures ranging 30-70 deg C while 55.12% for EG:dW mixture-based nanofluids. The performance of the most stable deionized water (0.5% volume concentration) in a heat exchanger was determined to be 0.57% to 6.02% and 13.49 to 35.40%, respectively. The enhancement of thermophysical properties and heat transfer of nanosilica-in-fluid dispersion suggests the potential use of the nanofluids as a heat transfer fluid.

Language

English

Document Type

Article

Pages /Collation

284 leaves

En – AGROVOC descriptors

RICE HUSKS; HEAT EXCHANGERS; FLUIDS; ETHYLENE GLYCOL; AGRICULTURAL PRODUCTS; THERMAL PROPERTIES; HEAT TRANSFER

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