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Article
Publication date: 17 October 2018

Stephen Loh Tangwe and Michael Simon

The purpose of this paper is fourfold: to experimentally determine the standby thermal energy losses in various hot water cylinders in both scenarios, without isotherm

Abstract

Purpose

The purpose of this paper is fourfold: to experimentally determine the standby thermal energy losses in various hot water cylinders in both scenarios, without isotherm blanket installation and with isotherm blanket installation; to analytically evaluate the performance of either the geyser, split- or integrated-type ASHP water heaters based on the number of heating up cycles and total electrical energy consumptions over a 24-h period without isotherm blankets and with isotherm blankets installed; to demonstrate the impact of the electrical energy factors of the split- and integrated-type ASHP water heaters under both the scenarios (without and with the isotherm blankets installed); and to use statistical tests (one way ANOVA and multiple comparison procedure tests) to verify whether any significant difference in the standby thermal energy losses occurred for each of the heating devices under both the scenarios.

Design/methodology/approach

The methodology was divided into monitoring of the performance of the electrical energy consumptions and ambient conditions of the hot water heating technologies without isotherm blanket installation and with isotherm blanket installation.

Findings

The results reveal that the average standby thermal energy loss of the geyser without the installation of an isotherm blanket was 2.5 kWh. And this standby loss can be reduced to over 18.5 per cent by just installing a 40-mm thick isotherm blanket on the tank. The statistical tests show a significant mean difference in the group electrical energy consumed to compensate for the standby losses under both scenarios. In contrast, the average standby thermal energy losses for the split- and integrated-type ASHP water heaters were 1.33 kWh and 0.92 kWh, respectively. There was a reduction of 15.5 per cent and 3.5 per cent in the electrical energy consumed in compensating for standby losses for both the split and integrated types, respectively, but there was no significant mean difference in the standby losses under both scenarios for the two systems. Again, without any loss of generality, the electrical energy factor of both the ASHP water heaters decreased upon installation of the isotherm blanks.

Research limitations/implications

The experiments were conducted only for a 150-L geyser and 150-L split- and integrated-type ASHP water heaters. The category of the different types of ASHP water heaters was limited to one because of the cost implication.

Practical implications

The experiments were not conducted with various hot water storage tanks installed in different positions (roof, inside or outside of a building wall, etc.) so that actual real-life observations could be obtained. The challenges of easy disassembling and deployment of systems and DAS to different positions were also a real concern.

Social implications

The findings can help homeowners and ESCO in deciding whether to install isotherm blankets on storage tanks of ASHP water heaters on the basis of the impact of standby losses and its potential viability.

Originality/value

The experimental design and methodology are the first of its kind to be conducted in South Africa. The results and interpretation were obtained from original data collected from a set of experiments conducted. The findings also show that the installation of isotherm blanket on an electric geyser can result in a significant mean reduction in the standby losses. In contrast, an installation of the isotherm blankets on the storage tanks of ASHP water heaters can reduce the standby losses, but there exists no significant mean difference.

Details

Journal of Engineering, Design and Technology, vol. 16 no. 5
Type: Research Article
ISSN: 1726-0531

Keywords

Article
Publication date: 22 February 2021

Juan Carlos Lucas Aguirre, German Antonio Giraldo Giraldo and Misael Cortés Rodríguez

In order to understand interactions aw vs equilibrium moisture content (EMC) in fortified coconut powder, moisture sorption isotherms were constructed under different…

Abstract

Purpose

In order to understand interactions aw vs equilibrium moisture content (EMC) in fortified coconut powder, moisture sorption isotherms were constructed under different storage conditions in order to predict the changes in their physical, chemical and microbiological properties that occur during storage and processing, which are unique to each food.

Design/methodology/approach

For which the moisture sorption isotherms were determined at three different temperatures (15, 25 and 35 °C), in a range of water activity from 0.1 to 0.90. Nine models, namely, the GAB, BET, Oswin, Smith, Halsey, Henderson, Chung and Pfost, Peleg and Caurie equations, were fitted to the sorption data. Various statistical tests were adopted as criteria to evaluate the fit performance of the models.

Findings

Of the models tested, the Peleg model gave the best fit to experimental data (R2 = 0.997; RMSE = 0.276), across the full range of water activities and at different temperatures. Humidity of the monolayer (mo) was found between 2.54 and 2.34%, a fundamental parameter to define the storage and control conditions, given that it is considered the value at which the product is more stable. The net sorption isosteric heat (Qst) increased to maximum and then diminished with increased moisture content (Xw); maximum values were obtained in the Xw interval between 0.48 and 2.87% (db), being between 35.72 and 99.26 kJ/mol, where the maximum value indicates coverage of the strongest bond sites and higher adsorbate-adsorbent interaction.

Originality/value

These results provide reliable experimental data on water absorption isotherms of the CP + FAC important to determine optimal processing, storing and packaging conditions.

Details

British Food Journal, vol. 123 no. 7
Type: Research Article
ISSN: 0007-070X

Keywords

Article
Publication date: 10 December 2018

Ahad Abedini, Saeed Emadoddin and Taher Armaghani

This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum…

Abstract

Purpose

This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum oxide, copper, silver and titanium oxide. Numerical solution is performed using a finite-volume method based on the SIMPLE algorithm, and the discretization of the equations is generally of the second order. Inner and outer cylinders have a constant temperature, and the inner cylinder temperature is higher than the outer one. The two cylinders can be rotated in both directions at a constant angular velocity. The effect of parameters such as Rayleigh, Richardson, Reynolds and the volume fraction of nanoparticles on heat transfer and flow pattern are investigated. The results show that the heat transfer rate increases with the increase of the Rayleigh number, as well as by increasing the volume fraction of the nanoparticles, the heat transfer rate increases, and this increase is about 8.25 per cent for 5 per cent volumetric fraction. Rotation of the cylinders reduces the overall heat transfer. Different directions of rotation have a great influence on the flow pattern and isotherms, and ultimately on heat transfer. The addition of nanoparticles does not have much effect on the flow pattern and isotherms, but it is quantitatively effective. The extracted results are in good agreement with previous works.

Design/methodology/approach

Studying mixed convection heat transfer in the horizontal annulus in the presence of a water-based fluid with aluminum oxide, copper, silver and titanium oxide nanoparticles is carried out quantitatively using a finite-volume method based on the SIMPLE algorithm.

Findings

Increasing the Rayleigh number increases the Nusselt number. Increasing the Richardson number increases heat transfer. Adding nanoparticles does not have much effect on the flow pattern but is effective quantitatively on heat transfer parameters. The addition of nanoparticles sometimes increases the heat transfer rate by about 8.25 per cent. In constant Rayleigh numbers, increasing the Reynolds number reduces heat transfer. The Rayleigh and Reynolds numbers greatly affect the isotherms and streamlines. In addition to the thermal conductivity of nanoparticles, the thermo-physical properties of nanoparticles has great effect in the formation of isotherms and streamlines and ultimately heat transfer.

Originality/value

Studying the effect of different direction of rotation on the isotherms and streamlines, as well as the comparison of different nanoparticles on mixed convection heat transfer in annulus.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 19 August 2022

Hanieh Shaki

In this study, the removal of a series of acid dyes by hybrid polymer adsorbent was investigated. Textile industry wastewater is mainly consisted of suspended solid…

Abstract

Purpose

In this study, the removal of a series of acid dyes by hybrid polymer adsorbent was investigated. Textile industry wastewater is mainly consisted of suspended solid particles and organic compounds with complex and nondecomposable structures. Treatment of such wastewaters has received much attention by researchers because of high water consumption and the presence of various chemical compounds, especially dyes. The use of polymers has recently attracted much attention for the treatment of textile wastewaters. According to the literature, hybrid polymers are highly capable of adsorbing dyes. In this research work, polyacrylamide/iron sulfate (PAM-FeSO4) hybrid polymer was successfully synthesized through solution polymerization of acrylamide with ammonium persulfate and sodium thiosulfate and gradual addition of iron sulfate. The hybrid polymeric adsorbent was then used for removing acidic dyes with different chemical structures.

Design/methodology/approach

The effects of various experimental conditions and parameters, such as initial concentrations of dye and adsorbent, on the adsorption capacity of the adsorbent were investigated. The dye concentration was measured by an UV–vis spectrophotometer. The adsorption equilibrium was studied by plotting adsorption isotherms. The experimental data was fitted to Langmuir and Freundlich isotherms.

Findings

The adsorption experiments indicated that the PAM-FeSO4 hybrid polymer has a high adsorption capacity (117.64 mg g−1 for the Orange ІІ and 80.64 mg g−1 for the Sunset Yellow [SY]) when 80 mg of adsorbent was immersed in the dye solution (1 g L−1) with a pH of 11 at 25°C. The analysis of the equilibrium isotherms using the Langmuir and Freundlich isotherms indicated that the Langmuir model fit well to the experimental data.

Originality/value

To the best of the authors’ knowledge, this study is original. The removal of acid dyes such as Sunset Yellow and Methyl Orange using PAM-FeSO4 hybrid polymer as flocculant was done for the first time.

Details

Pigment & Resin Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 3 August 2022

Nargess Yousefi-Limaee, Behzad Shirkavand Hadavand and Zahra Rahmani

Methylene blue (MB) is classified as a cationic dye which is widely used as chemical indicator, coloring agent and biological stain. The discharge of this dye to the water…

Abstract

Purpose

Methylene blue (MB) is classified as a cationic dye which is widely used as chemical indicator, coloring agent and biological stain. The discharge of this dye to the water streams is harmful to the human beings. For this reason, this study investigated the removal of MB from aqueous solution by hydrogel nanocomposite.

Design/methodology/approach

In experimental part, at first, ultraviolet (UV)-curable hydrogel/chitosan nanocomposite, which improves its elasticity by urethane acrylate, was synthesized and characterized by FTIR and SEM analysis. Afterward, the synthesized hydrogel nanocomposite was applied for the removal of MB and the influence of operational condition including nanocomposite loading, dye concentration, contact time and pH of solution was specified. Moreover, isotherm studies as well as kinetics survey were performed.

Findings

Langmuir, Freundlich, Brunauer, Emmett and Teller and Tempkin adsorption isotherms were assessed for the analysis of experimental data indicating the Freundlich isotherm was the best fitted one. The adsorption kinetics data was examined indicating the adsorption kinetics appropriate to pseudo-second-order kinetics model.

Originality/value

The predominant water absorption property of the UV-curable hydrogel/chitosan nanocomposite to 8.5 steps and outstanding adsorption capacity for the elimination of MB on hydrogel nanocomposite subscribed that the synthesized hydrogel could be a favorable adsorbent for simultaneous absorption of water and removal of cationic dyes.

Details

Pigment & Resin Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 27 May 2014

Ahmad Mashal, Jehad Abu-Dahrieh, Ashraf A. Ahmed, Lukumon Oyedele, No’man Haimour, Ahmad Al-Haj-Ali and David Rooney

The purpose of this paper is to investigate the performance of natural Jordanian zeolite tuff to remove ammonia from aqueous solutions using a laboratory batch method and…

Abstract

Purpose

The purpose of this paper is to investigate the performance of natural Jordanian zeolite tuff to remove ammonia from aqueous solutions using a laboratory batch method and fixed-bed column apparatus. Equilibrium data were fitted to Langmuir and Freundlich models.

Design/methodology/approach

Column experiments were conducted in packed bed column. The used apparatus consisted of a bench-mounted glass column of 2.5 cm inside diameter and 100 cm height (column volume = 490 cm3). The column was packed with a certain amount of zeolite to give the desired bed height. The feeding solution was supplied from a 30 liter plastic container at the beginning of each experiment and fed to the column down-flow through a glass flow meter having a working range of 10-280ml/min.

Findings

Ammonium ion exchange by natural Jordanian zeolite data were fitted by Langmuir and Freundlich isotherms. Continuous sorption of ammonium ions by natural Jordanian zeolite tuff has proven to be effective in decreasing concentrations ranging from 15-50 mg NH4-N/L down to levels below 1 mg/l. Breakthrough time increased by increasing the bed depth as well as decreasing zeolite particle size, solution flow-rate, initial NH4+ concentration and pH. Sorption of ammonium by the zeolite under the tested conditions gave the sorption capacity of 28 mg NH4-N/L at 20°C, and 32 mg NH4-N/L at 30°C.

Originality/value

This research investigates the performance of natural Jordanian zeolite tuff to remove ammonia from aqueous solutions using a laboratory batch method and fixed-bed column apparatus. The equilibrium data of the sorption of Ammonia were plotted by using the Langmuir and Freundlich isotherms, then the experimental data were compared to the predictions of the above equilibrium isotherm models. It is clear that the NH4+ ion exchange data fitted better with Langmuir isotherm than with Freundlich model and gave an adequate correlation coefficient value.

Details

World Journal of Science, Technology and Sustainable Development, vol. 11 no. 2
Type: Research Article
ISSN: 2042-5945

Keywords

Article
Publication date: 14 November 2019

Leo Lukose and Tanmay Basak

The purpose of this paper is to study thermal (natural) convection in nine different containers involving the same area (area= 1 sq. unit) and identical heat input at the…

Abstract

Purpose

The purpose of this paper is to study thermal (natural) convection in nine different containers involving the same area (area= 1 sq. unit) and identical heat input at the bottom wall (isothermal/sinusoidal heating). Containers are categorized into three classes based on geometric configurations [Class 1 (square, tilted square and parallelogram), Class 2 (trapezoidal type 1, trapezoidal type 2 and triangle) and Class 3 (convex, concave and triangle with curved hypotenuse)].

Design/methodology/approach

The governing equations are solved by using the Galerkin finite element method for various processing fluids (Pr = 0.025 and 155) and Rayleigh numbers (103 ≤ Ra ≤ 105) involving nine different containers. Finite element-based heat flow visualization via heatlines has been adopted to study heat distribution at various sections. Average Nusselt number at the bottom wall ( Nub¯) and spatially average temperature (θ^) have also been calculated based on finite element basis functions.

Findings

Based on enhanced heating criteria (higher Nub¯ and higher θ^), the containers are preferred as follows, Class 1: square and parallelogram, Class 2: trapezoidal type 1 and trapezoidal type 2 and Class 3: convex (higher θ^) and concave (higher Nub¯).

Practical implications

The comparison of heat flow distributions and isotherms in nine containers gives a clear perspective for choosing appropriate containers at various process parameters (Pr and Ra). The results for current work may be useful to obtain enhancement of the thermal processing rate in various process industries.

Originality/value

Heatlines provide a complete understanding of heat flow path and heat distribution within nine containers. Various cold zones and thermal mixing zones have been highlighted and these zones are found to be altered with various shapes of containers. The importance of containers with curved walls for enhanced thermal processing rate is clearly established.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 18 August 2022

Dipak Kumar Mandal, Nirmalendu Biswas, Nirmal K. Manna, Rama Subba Reddy Gorla and Ali J. Chamkha

This study aims to numerically examine the influence of various geometric parameters of a novel W-shaped porous cavity undergoing hybrid nanofluid-based…

Abstract

Purpose

This study aims to numerically examine the influence of various geometric parameters of a novel W-shaped porous cavity undergoing hybrid nanofluid-based magnetohydrodynamic mixed convection. The W-shaped cavity is modified from the classical trapezoidal cavity by constructing a triangular shape at its bottom. This cavity is isothermally active at the bottom, with different numbers and heights of the triangular peak (or undulation). The heated hybrid nanofluid (Cu–Al2O3–H2O) flow is cooled through the translating top wall. Inclined sidewalls are thermally insulated. To compare the impacts of change in geometric parameters, a square cavity under similar boundary conditions is also simulated. This study is carried out systematically addressing the various influences from a range of parameters like side angles (γ), number (m) and height (λ) of the bottom undulation, Reynolds number (Re), Richardson number (Ri), Darcy number (Da), Hartmann number (Ha), hybrid nanoparticles volume fraction (φ) on the overall thermal performance of the cavity.

Design/methodology/approach

Applying the finite volume approach, the transport equations involving multiphysical conditions like porous substance, hybrid nanofluid, magnetic field and shearing force are solved numerically by using a written FORTRAN-based code following the SIMPLE algorithm. The algebraic equations are solved over all the control volumes in an iterative process using the alternate direction implicit scheme and the tri-diagonal matrix algorithm. The converged solution of the iterative process is obtained when the relative error levels satisfy the convergence criterion of 10–8 and 10–10 for the maximum residuals and the mass defect, respectively.

Findings

It is revealed that an increase in the bottom undulation height always improves the thermal energy transfer despite the reduction of fluid volume. Thermal energy transfer significantly depends on the heating and cooling surface lengths, fluid volume in the cavity and the magnitude of the bottom undulation height of the W-shaped cavity. With the increase in bottom undulation height, effective heating length increases by ∼28%, which leads to a ∼15% reduction in the effective volume of the working fluid and a gain in heat transfer by ∼56.48%. In general, the overall thermal energy transport is improved by increasing Re, Ri and Da; whereas it is suppressed by increasing Ha.

Research limitations/implications

There are many opportunities for future research experimentally or numerically, considering different curvature effects, orientations of the geometry, working fluids, boundary conditions, etc. Furthermore, this study could be extended by considering unsteady flow or turbulent flow.

Practical implications

In many modern systems/processes pertaining to materials processing, continuous casting, food processing, chemical reactors, biomedical applications, etc. fine control in the transport process is a major concern. The findings of this analysis can effectively be useful for other applications for getting more control features in terms of achieving the operational objectives. The approach of the system analysis (considering geometrical size parameters to delve into the underlying transport physics) and the obtained simulated results presented in the work can usefully be applicable to similar thermal systems/devices such as materials processing, thermal mixing, chemical reactors, heat exchangers, etc.

Originality/value

From the well-documented and vast pool of literature survey, it is understood that there exists no such investigation on the considered geometry and study. This study contributes a lot to understanding magnetic field moderated thermofluid flow of a hybrid nanofluid in a porous medium filled W-shaped cavity, in consideration of different geometrical shape parameters (undulation peak numbers at bottom wall, peak heights, side angles and heating and cooling length). Findings brought by this study provide great insights into the design and operation under various ranges of multiphysical thermofluid-flow processing phenomena.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

Keywords

Open Access
Book part
Publication date: 4 May 2018

Intan Lestari

Purpose – The purpose of this paper to immobilization provides biosorbent particle with density and mechanichal strength, immobilization can save the cost of separating…

Abstract

Purpose – The purpose of this paper to immobilization provides biosorbent particle with density and mechanichal strength, immobilization can save the cost of separating from biomass, can be regeneration and to increase adsorption capacity for metal ions.

Design/Methodology/Approach – The parameters affecting the adsorption, such as initial metal ion concentration, pH, contact time, and temperature, were studied. The analysis of biosorbent functional group was carried out by Fourier Transform Infrared Spectroscopy, SEM-EDX, for elemental analysis.

Findings – Optimum pH condition for biosorption Cd(II) was pH 5, contact time was 45 min, and initial concentration was 250 mg/L. Biosorbent analysis was characterized using SEM-EDX and FTIR analysis. Kinetics adsorption was studied and analyzed in terms of the pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics models. The result showed that the biosorption for Cd(II) ion followed the pseudo-second-order kinetic model. Biosorption data of Cd(II) ion at 300°K, 308°K, and 318°K was analyzed with Temkin, Langmuir, and Freundlich isotherms. Biosorption of Cd(II) by durian seed immobilization in alginate according to the Langmuir isotherm equation provided a coefficient correlation of r2 = 0.939 and maximum capacity biosorption of 25.05 mg/g.

Details

Proceedings of MICoMS 2017
Type: Book
ISBN:

Keywords

Article
Publication date: 29 July 2021

Nirmalendu Biswas, Nirmal Kumar Manna, Dipak Kumar Mandal and Rama Subba Reddy Gorla

This study aims to investigate thermo-bioconvection of oxytactic microorganisms occurring in a nanofluid-saturated porous lid-driven cavity in the presence of the magnetic…

Abstract

Purpose

This study aims to investigate thermo-bioconvection of oxytactic microorganisms occurring in a nanofluid-saturated porous lid-driven cavity in the presence of the magnetic field. The heating is provided through a bell-shaped curved bottom wall heated isothermally. The effects of the peak height of the curved bottom wall, bioconvection Rayleigh number (Rb), Darcy number (Da), Hartmann number (Ha), Peclet number (Pe), Lewis number (Le) and Grashof number (Gr) on the flow structure, temperature and the iso-concentrations of oxygen and microorganisms are examined and explained systematically. The local and global, characteristics of heat transfer and oxygen concentration, are estimated through the Nusselt number (Nu) and Sherwood number (Sh), respectively.

Design/methodology/approach

The governing equations of continuity, momentum, energy and additionally consisting of species transport equations for oxygen concentration and population density of microorganisms, are discretized by the finite volume method. The evolved linearized algebraic equations are solved iteratively through the alternate direction implicit scheme and the tri-diagonal matrix algorithm. The computation domain has meshed in non-uniform staggered grids. The entire computations are carried out through an in-house developed code written in FORTRAN following the SIMPLE algorithm. The third-order upwind and second-order central difference schemes are used for handling the advection and diffusion terms, respectively. The convergence criterion for the iterative process of achieving the final solution is set as 10–8 and 10–10, respectively, for the maximum residuals and the mass defect.

Findings

The results show that the flow and temperature distribution along with the iso-concentrations of oxygen and microorganisms are markedly affected by the curvature of the bottom wall. A secondary circulation is developed in the cavity that changes the flow physics significantly. The Nu increases with the peak height of the curved bottom wall and Da; however, it decreases with Ha and Rb. The Sh increases with Da but decreases with Ha and the peak height of the curved wall.

Research limitations/implications

A similar study of bioconvection could be extended further considering thermal radiation, chemical attraction, gravity, light, etc.

Practical implications

The outcomes of this investigation could be used in diverse fields of multi-physical applications such as in food industries, chemical processing equipment, fuel cell technology and enhanced oil recovery.

Originality/value

The insights of bioconvection of oxytactic microorganisms using a curved bottom surface along with other physical issues such as nanofluid, porous substance and magnetic field are addressed systematically and thoroughly.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 12
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of over 1000