Abstract
There is a significant enhancement of the heat transfer rate with the usage of nanofluid. This article describes a study of the combination of using nanofluid with inserts, which has proved itself in attaining higher benefits in a heat exchanger, such as the radiator in automobiles, industries, etc. Nanofluids are emerging as alternative fluids for heat transfer applications due to enhanced thermal properties. In this paper, the thermal hydraulic performance of ZrO2, awater-based nanofluid with various volume concentrations of 0.1%, 0.25%, and 0.5%, and staggered conical strip inserts with three different twist ratios of 2.5, 3.5, and 4.5 in forward and backward flow patterns were experimentally tested under a fully developed laminar flow regime of 0–50 lphthrough a horizontal test pipe section with a length of 1 m with a constant wall heat flux of 280 W as the input boundary condition. The temperatures at equidistant position and across the test section were measured using K-type thermocouples. The pressure drop across the test section was measured using a U-tube manometer. The observed results showed that the use of staggered conical strip inserts improved the heat transfer rates up to that of 130.5%, 102.7%, and 64.52% in the forward arrangement, and similarly 145.03%, 116.57%, and 80.92% in the backward arrangement with the twist ratios of 2.5, 3.5, and 4.5 at the 0.5% volume concentration of ZrO2 nanofluid. It was also seen that the improvement in heat transfer was comparatively lower for the other two volume concentrations considered in this study. The twist ratio generates more swirl flow, disrupting the thermal hydraulic boundary layer. Nanofluids with a higher volume concentration lead to higher heat transfer due to higher effective thermal conductivity of the prepared nanofluid. The thermal performance factor (TPF) with conical strip inserts at all volume concentrations of nanofluids was perceived as greater than 1. A sizable thermal performance ratio of 1.62 was obtained for the backward-arranged conical strip insert with 2.5 as the twist ratio and a volume concentration of 0.5% ZrO2/deionized water nanofluid. Correlations were developed for the Nusselt number and friction factor based on the obtained experimental data with the help of regression analysis.
Highlights
There are several heat transfer augmentation techniques that were developed to achieve enhanced heat transfer rate and compact design in various heat exchanger applications for both engineering and industrial purposes, such as manufacturing systems, air-conditioning systems, solar heating systems, refrigeration systems, microelectronics, etc., to attain material, energy, and cost savings
The results revealed that the Peclet number (Pe) had a greater contribution to the heterogeneity of the nanofluids
The experimental results of the convective heat transfer and pressure drop of the uniformly heated pipe with working fluid deionized water (DI) water under laminar flow were validated in terms of the Nusselt number and friction factor in order to assess the reliability of the experimental set-up. These parameters were compared to the standard correlation of Shah and Hagen–Poiseuille under the laminar flow regime in a plain tube
Summary
There are several heat transfer augmentation techniques that were developed to achieve enhanced heat transfer rate and compact design in various heat exchanger applications for both engineering and industrial purposes, such as manufacturing systems, air-conditioning systems, solar heating systems, refrigeration systems, microelectronics, etc., to attain material, energy, and cost savings. There are umpteen numbers of investigations that have been carried out numerically and experimentally on the heat transfer augmentation of commonly working fluids, such as water, oil, ethylene glycol, etc. Suganthi and Rajan [1] suggested guidelines for selecting appropriate nanofluids for enhancement of heat transfer, which include the selection of nanomaterials having higher values of specific heat, thermal conductivity, and surface area; and lower values of the density, aspect ratio, and viscosity. Many experimental investigations on water-based nanofluids, such as graphene/water [6], silica/water [7], TiO2 /water [8], and Al2 O3 /water [9], promoted increased heat transfer in terms of the Nusselt number and without much penalty on the pumping power
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