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Investigation of the effect of magnetic field on the adsorption of carbon dioxide by different nanofluids in a bubble adsorption tower(part1)

In some researches in the field of use of nanofluids in mass transfer, it has been reported to increase and in some cases, decrease in mass transfer has been reported.

The purpose of this paper is to conduct a thorough and complete research to investigate and analyze the role of magnetic field strength and direction on the adsorption process by a magnetic nanofluid (water and iron oxide nanoparticles), a non-magnetic nanofluid (water and alumina nanoparticles) and a base fluid without It is a nanoparticle (deionized water). By comparing the results, a precise understanding of the role of the magnetic field on the mass transfer rate can be obtained.

materials and methods

A schematic of the laboratory system built for the experiments is shown in Figure 1. This device consists of a glass column with a diameter of 4 cm and a height of 25 cm that the adsorption process is performed in this chamber. The solvent, which can be ion-free or nanofluid water, is placed inside the tower, and the carbon dioxide gas enters the radial diffuser system through the capsule after passing through the rotameter from the top of the tower and is dispersed as fine bubbles in the liquid phase. In each test, 200 cc of nanofluid was used and the height of the fluid inside the column was about 16 cm.

Figure 1: Schematic of a bubble tower equipped with a magnetic field

In this research, by designing and fabricating a solenoid and adding it to the device, it was possible to study the effects of magnetic field on the process of carbon dioxide adsorption. Considering the
Important parameters in the design of the coil such as magnetic field strength, power supply, number of wire turns, height and thickness of the coil, diameter and material of the wire, ohmic resistance and finally the weight and price of the coil, the optimal state were selected. The coil was made of 5000 rounds of copper wire with a diameter of 0.85 mm in 55 layers, each layer containing about 90 turns and weighing 8.8 kg.

The tube has the ability to produce a direct magnetic field with an intensity of 1133 Gauss with a maximum current of 2.4 amps.

Biot-Savart law was used to calculate the magnetic field strength in coil. Equation 1 presents the field d → B relation of a current-carrying wire I created by the element d → l at a distance r from that element. This relationship is a law of inverse squares known as the law of bio-savar.

(1)

In this relation,μ0 it is called vacuum permeability and its value is equal to
4π × 10-⁷ T.m/A.The direction of the vector d→l in the direction of the wire and in the direction of the flow I and the vector of the field 𝔯 source is the current element is towards the desired point (𝔯=𝔯𝔯).the field at each point is equal to the sum of all magnetic The total magnetic fields of the current intensity elements. By integrating from equation 1 and having the number of wire turns, the number of layers And the diameter of the pipe wire, the field strength is obtained as follows from Equation 2.

(2)

The direction of the magnetic field can vary up or down according to the direction of the electric current. By generating a magnetic field in the coil, part of the electrical energy is converted to heat energy due to its significant resistance. According to the circular structure of the coil and the citizenship of the energy produced by the radius, the highest temperature at the surface of the coil is related to its inner radius.

For this purpose, a cylinder with a radius of 5.5 cm was placed around the bubble column so that the circulating water would take the heat transferred from the coil from the system. If the heat generated is not transferred to the environment, the amount of heat produced will increase over time and this increase will accelerate over time. A PV diode was used to convert the AC output current from the power supply to the DC current.

It should be noted that due to the low intensity of the magnetic field resulting from the wire, the side effects on the health of the experimenter are very small, while this field decreases with increasing distance to the second power. Three types of solvents including ion-free water, water nanofluid / aluminum oxide and nanofluid water / iron oxide with different concentrations were used to separate carbon dioxide gas.

In this study, ion-free water was used as the base fluid to prepare the nanofluid. Iron oxide nanofluid with oleic acid surface coating and initial concentration of 7% by volume made by Plasmachem Gmbh German company was selected and purchased for experiments.

The average diameter of nanoparticles is 8 nanometers and its density is 2.5 grams per cubic centimeter. Aluminum oxide nanoparticles were purchased from Nanoamor USA and converted to nanofluid indirectly or in two steps with the desired concentrations. The average diameter of nanoparticles is 80 nanometers and its density is 3.7 grams per cubic centimeter.

For uniform and suitable distribution of nanoparticles, after adding nanoparticles to the base fluid of the solution, it is placed under a mechanical stirrer for about one hour. Use this mixer to prevent lumps
Nanoparticles are used when added to the base fluid.

An ultrasonic stirrer is used to homogenize the solution. This device creates intense pressure waves in the solution, causing bubbles to burst and producing a shock wave with enough energy to break the bonds. The shear force from the bubble explosion as well as the turbulent currents caused by the acoustic vibration are used to homogenize the nanofluid.

After preparing the nanofluid for the preparation of sampling containers, the nanofluid is transferred into the bubble column and carbon dioxide gas enters from the top of the column. From the moment gas enters, time is measured because to obtain the mass transfer coefficient, the gas concentration within the nanofluid must be measured at different time intervals. At certain times, a sample is taken from the gas outlet by a 2 cc pipette and transferred to the sample container. In each test, 200 cc nanofluid was prepared and sampling was performed at intervals of 1, 2, 3, 5, 7 and 10 minutes from the time of gas entry.

Reference

Journal of Separation Science and Engineering / Investigation of the effect of magnetic field on the adsorption of carbon dioxide by different nanofluids in a bubble adsorption tower / Negin Mohammadzadeh-Farzaneh Rafieian-Massoud Haghshenas Fard-Mohsen Nasr Isfahani-Touraj Tavakoli

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