Review: Observation on CFD Analysis of ZnO and TiO2 Nanofluid with Oil and Ethylene Glycol in Square and Helical Coil Heat Exchanger

Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide the excellent thermal performance in helical coil heat exchangers. Research studies on heat transfer enhancement have gained serious momentum during recent years and have been proposed many techniques by different research groups [1]. A fluid with higher thermal conductivity has been developed to increase the efficiency of heat exchangers. The dispersion of 1-100nm sized solid nanoparticles in the traditional heat transfer fluids, termed as nanofluids, exhibit substantial higher convective heat transfer than that of traditional heat transfer fluids. Nanofluid is a heat transfer fluid which is the combination of nanoparticles and base fluid that can improve the performance of heat exchanger systems. In this present paper the efforts are made to understand that how to compare the heat transfer rate in Copper helically coiled tube and squared coiled tube heat exchanger using Zinc Oxide and Titanium Dioxide Nano fluid by studying research papers of various authors. Keywords: Helical Coil, Nano-fluid, Heat Exchanger, CFD, Pressure Drop, Temperature Distribution.

Selection of the Design of a Contact Condenser of a Gas-Steam Plant with Steam Injection into the Combustion Chamber

Due to the importance of the problems of implementing energy-saving technologies in modern conditions, one of the promising areas is the use of gas turbines for combined heat and power generation. One of the areas of effective development and technical re-equipment is the widespread use of highly economical combined steam and gas plants and gas turbines. The operation of the gas turbine unit “Aquarius” SE NPCG “Zorya-Mashproekt” with the injection of steam into the combustion chamber, which operates on the advanced cycle A-STIG and has in its circuit equipment for water regeneration, condensed from a vapor-gas mixture is considered. For condensation of steam from the vapor-gas mixture, a contact condenser-gas cooler is used, which is a mixing heat exchanger of complex design. The efficiency of heat transfer is determined by the design of the nozzle, namely, the developed heat transfer surface, small hydraulic supports, high heat transfer coefficients. An important aspect is the overall dimensions, which must be within certain limits. In the work it is offered to execute a design of the condenser in the form of a packed column. Different types of nozzles are considered to choose the best option. As a result of thermal design calculation of the contact capacitor, it is proposed to use Rashiga rings (15152) as a nozzle, which provide the lowest height of the nozzle at the required diameter of the device.

CFD Simulation of Helical Shell and Tube Heat Exchanger Using Optimization Techniques

The objective of this study is to simulate the performance of helical tube shell and tube heat exchanger with several optimization techniques using computational fluid dynamics CFD. To check the performance of a designed model of heat exchanger various techniques are available. In this study, the various possible model of the heat exchanger to enhance the performance of the device have been designed. Firstly, the straight tube is replaced by helical tube in the heat exchanger and used 10, 12, 14 number of helical baffles with 50% baffle cut. Total ten models have been developed. These models are model-I 4-turns without baffle, model-II 4-turns with 10 number baffles, model-III 5-turns without baffle, model-IV 5-turns with 12 number baffles, model-V 6-turns without baffle, model-VI 6-turns with 10 number baffles 0.083m baffle space, model-VII 6-turns with 12 number 0.083m baffle space, model-VIII 6-turns with 14 number baffles 0.064m baffle space, model-IX 7-turns without baffle, model-X 7-turns with 14 number baffles, different number of baffles and baffle space with 50% baffle cut and used CUO nanofluid model-XI 6-turns with 14 number baffle CUO fluid 0.083m baffle space CFD analysis simulation done on ANSYS FLUENT 18. The simulated result shows that the model XI is approximately 40% more optimized as compared to model-I and approximately 24% than model-VIII. It also found that the high heat transfer obtains with increased number of baffles.

Flow and Heat Transfer Characteristics of a Swirling Impinging Jet Issuing from a Threaded Nozzle of 45 Degrees

In order to achieve uniform and effective impingement cooling, a swirling jet with a swirling angle of 45° (SIJ 45°) is put forward in this paper. Namely, there are four 45° spiral grooves equipped on the inner wall of the circular hole. The difference in the flow field and heat transfer characteristics between the conventional impinging jet (CIJ) and SIJ 45° is compared and analyzed. The spiral channels can increase the heat transfer rate and cooling uniformity because of the action of superimposed airflow. In addition, the thread nozzle brings lower pressure loss, which can reduce the airflow friction while effectively ensuring high heat transfer in the center area of the jet. An experimental system is built to investigate the heat transfer and flow characteristics of the impingement surface. Smoke flow visualization technology is used to explore the complex flow field of the CIJ and SIJ 45°, and the heat transfer rate of the target surface is analyzed based on thermocouple data. When 6000≤Re≤30,000, and 1≤h/dj≤8, the averaged Nusselt number (Nu) correlation for SIJ 45° is established, which is in good agreement with the experimental results. SIJ 45° is an effective measure to replace the CIJ, and the research herein provides some reference for designing the structure of new jets.

Impact of Stefan blowing and magnetic dipole on bio-convective flow of Maxwell nanofluid over a stretching sheet

The features of ferromagnetic fluids make it supportive for an extensive usage in loudspeakers, magnetic resonance imaging, computer hard drives, directing of magnetic drug and magnetic hyperthermia. Owing to all such potential applications, the current investigation is to understand the relationship between the thermal distribution, magnetic field and resulting fluid flow of Maxwell liquid over a stretching sheet. Investigation of thermal energy and concentration is carried out in the presence of thermal radiation, non-uniform heat sink/source, chemical reaction, Stefan blowing, magnetic dipole, thermophoresis and Brownian motion. Also, microorganisms are considered just to stabilize the suspended nanoparticles. Boundary layer approximation is employed during mathematical derivation. Based on a new constitutive relation, the governing equations are formulated and are reduced into a coupled non-linear system of equations using appropriate transformations. Further, these equations are solved numerically using fourth-order Runge–Kutta method with shooting technique. The impact of involved parameters is discussed and analysed graphically. Outcomes disclose that Newtonian liquid shows high heat transfer when compared to non-Newtonian (Maxwell) liquid for increased values of Brownian motion and thermophoresis parameters. Increased values of Peclet number declines the rate of gyrotactic microorganisms. Finally, an increase in Brownian and thermophoresis motion parameters declines the rate of heat transfer.

Nanofluidic thermal-fluid transport in a split-driven porous system working under a magnetic environment

Purpose This study aims to focus on a thermo-fluid flow in a partially driven cavity (PDC) using Cu-water nanoliquid, magnetic field and porous substance. The cooling and sliding motion are applied on the upper half of the vertical walls and the bottom wall is heated. Thermal characteristics are explored to understand magnetohydrodynamic convection in a nanoliquid filled porous system from a fundamental viewpoint. The governing parameters involved to cater to the moving speed of the sidewalls and partial translation direction are the relative strength of thermal buoyancy, porous substance permeability, magnetic field intensity, nanoparticle suspension and orientation of the cavity. Design/methodology/approach The coupled transport equations of the problem are solved using an in-house developed finite volume-based computing code. The staggered nonuniform grids along the x and y directions are used. The SIMPLE algorithm technique is considered for the iterative solution of the discretized equations with the convergence check of the continuity mass defect below 10–10. Findings The present study unveils that the heat transfer enhances at higher Ri with the increasing value of Re, irrespective of the presence of a porous substance or magnetic field or the concentration of nanofluid. Apart from different flow controlling parameters, the wall motions have a significant contribution to the formation of flow vortices and corresponding heat transfer. Orientation of the cavity significantly alters the transport process within the cavity. The upward wall velocity for both the sidewalls could be a better choice to enhance the high heat transfer (approximately 88.39% at Richardson and Reynolds numbers, respectively, 0.1 and 200). Research limitations/implications Considering other multi-physical scenarios like porous layers, conducting block, microorganisms and the present investigation could be further extended to analyze a problem of complex flow physics. Practical implications In this study, the concept of partially driven wall motion has been adopted under the Cu-water nanoliquid, magnetic field, porous substance and oblique enclosure. All the involved flow-controlling parameters have been experimented with under a wide parametric range and associated thermo-flow physics are analyzed in detail. This outcome of this study can be very significant for designing as well as controlling thermal devices. Originality/value The convective process in a partially driven cavity (PDC) with the porous medium has not been investigated in detail considering the multi-physical scenarios. Thus, the present effort is motivated to explore the thermal convection in such an oblique enclosure. The enclosure is heated at its bottom and has partially moving-wall cold walls. It consists of various multi-physical conditions like porous structure, magnetic field, Cu–H2O nanoliquid, etc. The system performance is addressed under different significant variables such as Richardson number, Reynolds number, Darcy number, Hartmann number, nanoliquid concentration and orientation of cavity.

Flow and Heat Transfer Simulation Analysis of 3D Compact Heat Exchanger

Compact heat exchangers (CHEs) are one of the most commonly used heat exchangers in the industry due to their superior advantages over other types of heat exchangers. Various geometric (fin spacing, tube inclination angle, etc) and process (such as flow velocity, temperature, etc) parameters affect the performance of such compact HEs. This research aims to examine the effects of fin spacing, tube inclination angle, and airflow velocity on heat transfer and pressure drop performance of CHE in both inline and staggered configurations. A three-dimensional (3D) numerical method with the aid of Ansys FLUENT software was carried out for the laminar flow condition. Based on the obtained results, the highest average heat transfer coefficient was observed at 120° for both tube arrangements while the lowest average pressure drop penalty is at 30°. Therefore, the recommended inclination angle when high heat transfer is needed is at 120° while if the pumping power is the major problem, 30 °or 150° is recommended. based on the London area goodness factor (j/f), 30° and 150° show the highest value for both configurations. The j/f factor decreases with the increase of Reynolds number for both configurations. In addition, 120° shows the lowest j/f which can be due to the high pressure drop.