Enhancement Of Heat Transfer Rate Research Articles

Optimal position of square cylinder vortex generator in channel is not a function of ordinate only – A heat transfer and optimization study

Wall heat transfer enhancement of a channel by introducing an adiabatic square cylinder as a vortex generator is investigated numerically and reported. An open-source computational fluid dynamics toolbox, OpenFOAM is used for the present numerical investigation where a base solver icoFOAM is modified by incorporating the energy equation for analyzing the heat transfer characteristics. The cylinder position; axial (in the direction of flow) and transverse (normal to the flow direction) both the locations are varied to analyze the effect of these parameters on the wall heat transfer performance of the channel. In addition, the effect of change of channel length and height along with Reynolds number on the heat transfer characteristics are investigated. The present result indicates that the position of an adiabatic cylinder for enhancing the wall heat transfer in a channel may not be presumed a priori. It is observed that axial and transverse location of cylinder has significant influence on the enhancement of heat transfer rate. An optimum location of cylinder is observed based on maximum Nusselt number. Further, the Nusselt number is noticeably affected by the channel length and height along with Reynolds number. Thus, the location of a cylindrical vortex generator in a channel needs to be optimized for maximum thermal performance and cannot be ascertained a priori. For this purpose, a correlation of thermal performance with cylinder location, channel dimension, and Reynolds number is presented in the present study, and then the optimized location of the adiabatic cylinder is found for maximum thermal performance by using Particle Swarm Optimization (PSO).

Parametric analysis of the heat transfer behavior of the nano-particle ionic-liquid flow between concentric cylinders

This paper investigates the enhanced viscous behavior and heat transfer phenomenon of an unsteady two di-mensional, incompressible ionic-nano-liquid squeezing flow between two infinite parallel concentric cylinders. To analyze heat transfer ability, three different type nanoparticles such as Copper, Aluminum [Formula: see text], and Titanium oxide [Formula: see text] of volume fraction ranging from 0.1 to 0.7 nm, are added to the ionic liquid in turns. The Brinkman model of viscosity and Maxwell-Garnets model of thermal conductivity for nano particles are adopted. Further, Heat source [Formula: see text], is applied between the concentric cylinders. The physical phenomenon is transformed into a system of partial differential equations by modified Navier-Stokes equation, Poisson equation, Nernst-Plank equation, and energy equation. The system of nonlinear partial differential equations, is converted to a system of coupled ordinary differential equations by opting suitable transformations. Solution of the system of coupled ordinary differential equations is carried out by parametric continuation (PC) and BVP4c matlab based numerical methods. Effects of squeeze number ( S), volume fraction [Formula: see text], Prandtle number (Pr), Schmidt number [Formula: see text], and heat source [Formula: see text] on nano-ionicliquid flow, ions concentration distribution, heat transfer rate and other physical quantities of interest are tabulated, graphed, and discussed. It is found that [Formula: see text] and Cu as nanosolid, show almost the same enhancement in heat transfer rate for Pr = 0.2, 0.4, 0.6.

Experimental Investigation of Double Pipe Heat Exchanger Performance based on Alumina and Copper Oxide Working Nanofluids

The heat transfer performance of heat exchanger is greatly depending on the thermal conductivity and heat transfer capacity of the working fluid. One of the important methods to improve the thermal conductivity of the heat transfer fluid is by adding nano particles of materials with high thermal conductivity. In the present study, an experimental work was conducted to investigate the performance enhancement of double pipe heat exchanger using Alumina (Al2O3) and Copper oxide (CuO) nano particles mixed with engine oil as a working fluid. The thermal performance of heat exchanger was investigated at particles concentrations 0.05% and 0.1% of Al2O3 and CuO nano particles to determine the most effective factors on heat transfer enhancement. The results revealed that, the enhancement percentage in Nusselt number (Nu) for nanofluid at 0.05% particles concentration compared to pure oil was 9% and 6% for CuO and Al2O3 nanofluids respectively. While at 0.1% concentration, the enhancement percentage in Nu was about 17% and 15% for CuO and Al2O3 nanofluids respectively. The enhancement percentage in value of overall heat transfer coefficient for CuO nanofluid was 6.5% compared to Al2O3 nanofluid at 0.1% concentration. The enhancement percentage in the heat exchanger effectiveness was about 12% for CuO nanofluid compared with that for Al2O3 at 0.1% concentration. Adding the CuO and Al2O3 nano particles has improved the thermal conductivity of base fluid (oil) and led to a significant enhancement in heat transfer rate and thermal performance of the heat exchanger.

Magneto-nanofluid coolants past heated shrinking/stretching surfaces: Dual solutions and stability analysis

Recent advancement in nanotechnology has provides a veritable platform for the emergence of a better ultrahigh-performance coolant known as nanofluid for many engineering and industrial technologies. In this study, we examine the influence of magnetic field on heat transfer enhancement of nanofluids coolants consisting of Cu-water, Al2O3-water, and Fe3O4-water over a slippery but convectively heated shrinking and stretching surfaces. Based on some realistic assumptions, the nonlinear model differential equations are obtained and numerically tackled using shooting procedure with Runge-Kutta-Fehlberg integration scheme. The existence dual solutions in the specific range of shrinking surface parameters is found. Temporal stability analysis to small disturbances is performed on these dual solutions. It is detected that the upper solution branch is stable, substantially realistic with positive smallest eigenvalues while the lower solution branch is unstable with negative smallest eigenvalues. Influence of numerous emerging parameters on the momentum and thermal boundary layer profiles, skin friction, Nusselt number and heat transfer enhancement rate are depicted graphically and quantitatively discussed.

Heat transfer characteristics of an impinging swirling inverse diffusion butane/air flame jet

This paper presents an experimental study to explore the feasibility of utilizing a swirling inverse diffusion flame (IDF) jet for impingement heating. The investigation concentrates on the impinging flame structure and impingement heat transfer. The effects of air swirling, the air jet Reynolds number, Rea, the global equivalence ratio, Φ, and the non-dimensional burner-to-plate distance, H/da, on the impinging flame shape and impingement heat transfer are investigated experimentally. The Experiments show that introduction of air swirling can either enhance or reduce the heat transfer rate depending on operating condition. Under-swirling produces no evident heat transfer enhancement due to insufficient air/fuel mixing, while over-swirling reduces heat transfer rate because of the dilution of the entrained cold ambient air. Heat transfer enhancement is achieved with the appropriate level of air swirling when the complete combustion occurs in the inner reaction zone around a stoichiometric condition. The investigation shows that the impinging inverse flame jet with an appropriate level of air swirling possesses the advantages of both premixed and diffusion flame jets with blue appearance, ultra-low NOx emission, high flame temperature, good self-stabilization capability, and enhanced heat transfer rate. Therefore, it is a desirable option for impingement heating applications.

Thermo-economic and entropy generation analyses of magnetic natural convective flow in a nanofluid-filled annular enclosure fitted with fins

A numerical analysis on the thermo-natural convection as well as entropy generation of Al2O3-H2O nanofluid enclosed by two circular cylinders in the presence of magnetic fields was performed. The internal hot cylinder is fitted with rectangular fins of different lengths. Irreversibilities related to the thermal effects, friction effects, magnetic effects were considered. FEM was selected as solving method. Results described the impact of active parameters on the thermo-natural convective flow and heat transfer behaviour as well as entropy generation characteristics. In addition, a basic economic analysis has been proposed to consider the cost of nanofluids in comparison to their contribution in enhancing heat transfer rate. Results show that significant effects of pertinent parameters e.g. Rayleigh, Hartmann, and fins' size on flow, heat transfer, and irreversibilities within annulus. It is also found that for low Rayleigh, irreversibility related to thermo-effects is predominant within the annulus, and by augmenting Rayleigh values, the irreversibility due to the thermo-effects is no longer the key contributor to overall entropy production. The magnetic forces help to increase thermo-effects irreversibility contribution to overall irreversibilities. Finally, thermal transfer enhancement in case of the presence of magnetic forces is found to be more costly in terms of nanofluid utilization.

Effect of Hybrid Controller on a Heat Exchanger for Enhancing Heat Transfer Rate of Al2O3 Nanofluid

In this research paper, a hybrid controller is designed and developed which maintains the outlet temperature of a shell and tube heat exchanger by varying the cold water flow rate in such a way that conform the desired set value. Al2O3 nanofluid is mixed with water is to be used as the cooling fluid to increase the rate of heat transfer. PID controller only is not suitable for precise and a wide range of temperature control requirement. So that hybrid controller is designed and implemented by combining methods of fuzzy logic and PID controller’s concepts using Labview. Experiments were done on parallel flow shell and tube heat exchanger in a closed cycle system. The performance of the heat exchanger system is improved by a hybrid controller and the heat transfer rate is enhanced by aluminum oxide nanofluid.

Performance evaluation of simple DPHX with helical baffles in annulus side

In this paper, turbulent thermo-hydraulic analysis of water-to-water passively augmented DPHX with helical baffles is studied by varying the parameters, mass flow rate and baffle spacing. The baffles in annulus side of the inner pipe augments the rate of heat transfer on comparing with the simple DPHX. The influence of spacing between baffles on the heat transfer rate is investigated by varying the governing parameters. The Reynolds number is varied between 22,000 and 12, 5000 for three different baffle spacing (β) values of 75 mm, 100 mm and 125 mm. The thermo-hydraulic performance parameters pressure drop, Nusselt number and friction factor are examined and put forth corresponding to experimental data. From the results, it is inferred that the effect of baffles on the annulus side of the hot fluid flows through the inner pipe enhances heat transfer rate with increase in the Nu and decreases as the baffle spacing increases.

Carbon nanotubes suspended dusty nanofluid flow over stretching porous rotating disk with non-uniform heat source/sink

The current paper explores the flow of dusty nanoliquid over a rotating and stretchable disk with non-uniform heat sink/source. Further, we have done a comparative study on Single wall carbon nanotubes (SWCNT)-water and multi wall carbon nanotubes (MWCNT)-water based dusty fluid flows. By means of apt similarity variables, the governing equations are converted to set of nonlinear ordinary differential equations and then they are numerically tackled using Runge–Kutta–Fehlberg’s fourth fifth order (RKF45) method by adopting shooting technique. The influence of non-dimensional parameters on the heat transfer fields are incorporated and extensively discussed by means of appropriate graphs. Further, the reduced shear stresses at the disk in the tangential direction, in the radial direction and the heat transference rates of the fluid and particles are deliberated graphically. Results reveal that, the escalating values of space and temperature dependent heat source/sink parameters improves the heat transference of both liquids. The SWCNT-water based fluid shows improved shear stress in tangential and radial direction when compared to MWCNT-water based fluid for both the phases. The SWCNT-water based fluid shows enhanced heat transfer rate than MWCNT-water based fluid for both fluid and dust phases.

A critical review on nanorefrigerants: Boiling, condensation and tribological properties

A major amount of domestic energy consumption is spent on refrigeration and space cooling appliances. The performance of the refrigeration system depends on the thermophysical properties of the refrigerant. Altering the properties by additives such as nanoparticles has proven to be an effective solution to improve the performance of the system. This work swivels around flow boiling, pool boiling, tribological and condensation characteristics of nanorefrigerants in Vapour Compression Refrigeration System (VCRS) and Vapour Absorption Refrigeration System (VARS). An evolutionary timeline of nanorefrigerants is presented. Energy savings on compressor work by addition of nanolubricants is discussed. A sum of thirteen refrigerants and twelve nanoparticles in various combinations were encountered during this review process. CNTs performed better than metallic (Al, Cu, Au, Ag) and ceramic (Al 2 O 3 , TiO 2 , SiO 2 , ZnO) counterparts. Majority of the work reported enhancement in heat transfer rate and coefficient of performance (COP), however, few studies presented that CuO nanoparticles have shown negative correlation between HF, COP and volume fraction of nanoparticle. The review presents a broad idea on dispersion techniques, stability, properties of boiling and condensation, migration phenomenon of nanoparticles and various novel techniques to improve the performance of the refrigeration systems.

Numerical simulation for Arrhenius activation energy on the nanofluid dissipative flow by a curved stretching sheet

In this paper, we have analysed a binary chemical nanofluid dissipative flow (in two cases i.e., 50% EG $$ + $$ 50% water/silica and 50% EG $$ + $$ 50% water/graphene oxide) due to a curved stretching sheet with activation energy. Appropriate transformations yield the nonlinear ordinary differential system. Shooting procedure (R-K 4th order based) is executed to solve the resultant equations. Graphical illustrations thoroughly demonstrate the features of the involved pertinent parameters. We have deliberated the behaviour of the alike parameters on the rate of transfers (heat and mass) and surface drag force (skin friction coefficient) by means of tables. This investigation reveals that (a) reaction rate parameter and temperature difference parameter are helpful to ameliorate the mass transfer rate (b) concentration enhances for higher estimation of activation energy variable (c) increasing the volume fraction of nanoparticles reflects an escalation in temperature (d) heat transfer rate enhancement is recognized for the influence of heat transfer Biot number. At the end this study, we came to know that the EG-Water $$ + $$ Graphene Oxide mixture has more heat transfer rate compared to EG-Water $$ + $$ Silica mixture. This outcome helps to conclude that, whenever the more heat transport required in manufacturing and industries, we can take the EG-Water $$ + $$ Graphene Oxide mixture.

Experimental analysis of heat transfer coefficient in counter flow shell and helical coil tube heat exchanger with hybrid nanofluids to enhance heat transfer rate using in food processing industries

The impact of overall heat transfer coefficient and the pressure drop on performance of a counter flow helical tube heat exchanger with Cu-Ni-water hybrid nanofluid are computed. To evaluate heat transfer rate for a mix of base fluid with copper and nickel nanoparticles of volume concentrations 0.02,0.04 and 0.06 are added. To control the sedimentation of nanoparticles in the base fluid Ultrasonication followed by magnetic stirrer method is used. In this work experiments are conducted with to enhance heat transfer rate rather than stability of nanoparticles. Experiments are conducted for different concentrations and coil turns under laminar flow regime. The results are shown that 0.04 % vol of Cu-Ni/H2O with 12 turns is more predominate foe food processing applications due to its consistency in maintaining a constant temperature.

Effect of Spatially Varying Magnetic Field on the Cooling of an Electronic Component by Natural Convection With Magnetic Nanofluids

AbstractNatural convection cooling of an electronic component in an electronic device using water-based Fe3O4 magnetic nanofluids is studied under the presence of the magnetic field. The heated vertical electronic component in an enclosure type electronic device with a magnetic field source is used as a model for the study. Different samples of Fe3O4-water nanofluid are prepared using different surfactants and the stability of those samples are estimated using visualization and zeta potential technique. Thermal properties of the stable sample of magnetic nanofluid are precisely measured. The experimentally measured properties are used for further theoretical study. The natural convection is characterized in terms of the relative position of the magnetic source and the electronic component, the strength of the magnetic field, and the magnetization of the nanofluids. Nine different combinations of the position of the magnetic source and the electronic component have been compared with the case in which there is an absence of the magnetic field. The dimensionless number used in this investigation are Rayleigh number (103 ≤ Ra ≤ 106), magnetic numbers (Mn = 100, 500, and 1000), and Hartmann Number (0 ≤ Ha ≤ 100). The position of the magnetic source with respect to the electronic component significantly affects the rate of heat transfer. The effect is more pronounced when the magnetic source is placed below any of the two vertical walls of the enclosure. The fluid flow is observed distorted near the magnetic source when the Ha is increased. The increment in the magnetic number strengthens the flow, which leads to the enhanced heat transfer rate.

Numerical investigation on air-cooling enhancement of a motor cycle engine by varying fins geometry

Two-wheeler vehicles are equipped with an air-cooled cooling system. Internal combustion engines generate heat to obtain mechanical energy but non-convertible heat energy is dissipated from engine heat and walls. Air-cooled fins provide extra material with an extended surface area to enhance heat transfer rate. The performance of fins can be increased by changing different parameters like material, geometry, number of fins etc. Present work combines the changes in the fin geometry, shape, and pitch to maximize the heat transfer rate as compared to earlier available works. Modelling of 100 cc engine with cooling fins is recreated using CAD software SOLIDWORKS. A heat thermal analysis of original and modified models was done with Mechanical ANSYS and Fluent. In the thermal analysis, temperature variation along the length of the fins was analyzed. The modified model was able to achieve an 8.5 % increase in heat transfer rate with air-motion as compared to the existing original 100 cc engine cylinder.

Analysis the Enhancement of Heat Transfer Rate in Heat Pipe with Various Wick Materials for Effective Utilization of Waste Heat in Industries

Analysis the Enhancement of Heat Transfer Rate in Heat Pipe with Various Wick Materials for Effective Utilization of Waste Heat in Industries

An experimental study on heat transfer performance of GO and rGO-CuO nanofluids in a heat exchanger

In the present work, we have reported the synthesis and characterization of graphene oxide (GO) and copper oxide functionalized reduced graphene oxide (rGO-CuO) nanomaterials and studied their heat transfer properties. The synthesized materials are characterized using FTIR, XRD, UV–vis spectrophotometry, STM, EDX, SEM, and TEM analysis. Both GO and rGO-CuO nanomaterials are used as water-based NFs to study the heat transfer performance. The maximum enhancement of heat transfer rate and effectiveness of GO-water NF are found to be 18.51% and 24.58% concerning Di-water, respectively. Whereas, in the rGO-CuO-water NFs, maximum enhancement in the heat transfer rate and the effectiveness is obtained as 24.07% and 37%, compared to the Di-water, respectively. The maximum increase in Nusselt number for GO-water NF is found to be 16.48% as compared to Di-water. Whereas, for rGO-CuO-water NF is found to be 23.84% and 6.3% compared to Di-water and GO-water NFs at Reynold numbers 806.67, 1210.48, and 1617.21, respectively. These NFs may be useful in the future for heat exchanger applications.

Comparative numerical investigation of rectangular and elliptical fins for air cooled IC engines

In the present numerical examination, thermal characteristics of a rectangular and elliptical fin are compared. The problem considered is assessed with convective tip in a realistic manner. The basic conservation equations are solved by employing SIMPLE scheme in FLUENT 15.0. The numerical results shown 5% enhancement in heat transfer rate through elliptical fin than that of rectangular fin. Also, the attained numerical results are compared with the analytical values and are found to be in good accordance. Moreover, this study forms a basic paradigm for young researchers to understand the importance of CFD in the field of IC engines.

Effect of alumina nanoparticle shape in a triangular porous array of heated periodic pin-fins

Forced convective flow of alumina-water nanofluid with different shapes of nanoparticles through pin-fins of circular cross-section aligned in an equilateral triangular array was analyzed using finite volume methodology. The effect of the shape of alumina nanoparticles on heat transfer across the periodic equilateral triangular array has never been studied in the past. Four different shapes of nanoparticles were considered: spherical, cylindrical, bricks, and platelets. Using non-spherical (cylindrical, bricks, and platelets) nanoparticles resulted in a thinning thermal boundary layer, which resulted in a significant enhancement in heat transfer rates across the array. The mean Nusselt number was augmented by 22% when platelet shaped nanoparticles were utilized in place of spherical shaped nanoparticles. Likewise, the mean Nusselt number was augmented by 17% when cylindrical nanoparticles were used, in place of spherical nanoparticles, at the highest values of other parameters. The increment in effective viscosity of the nanofluid was the highest for platelet-shaped nanoparticles, which resulted in a greater pressure drop compared to other shapes of nanoparticles such as cylindrical, bricks, and spherical for all values of particle concentration. The results in the present article are validated extensively with accessible experimental and numerical studies.

Investigating the effect of inserting longitudinal fins on the overall thermal performance of spirally coiled tubes

Flow in curved pipes have been considered as a well-known technique of passive enhancement of heat transfer rate. However, there exists a lack of research considering the impact of geometrical modifications on heat transfer properties of spiral coils. In the present study, thermal and hydrodynamic behavior of the flow in spirally coiled tubes equipped with longitudinal internal fins are numerically studied. Steady three dimensional flow of water is simulated. The geometrical parameters in the present study include fin number, fin height, and fin width. Results reveal that for the spirals with a pair of horizontal fins, the increase in fin protrusion leads to PEC as high as 2.99. However, inappropriate orientation of longitudinal fins severely deteriorates the heat absorption capability of the spiral while imposing excessive pressure drop. This inefficiency is attributed to the disruption in formation of Dean vortices due to the presence of radial bumps. Thus, four-fin and three-fin configurations are generally inefficient. Changing the fin orientation in the two-fin geometries from horizontal to vertical lead to a similar inefficiency with the PEC falling as low as 0.24. Finally, the effect of local curvature on the thermal behavior of the spiral tube is investigated.

Design improvement of compact double-pipe heat exchangers equipped with tube-side helical insert and annulus-side helical strip: Hydrothermal and exergy analyses

Hydrothermal and exergy characteristics are numerically studied for the laminar flow in compact double-pipe heat exchangers (DPHXs) equipped with tube-side helical insert and annulus-side helical strip. Helical screw-type tape inserts are placed in the tube-side of the heat exchanger, along with four different configurations of helical strip in the annulus-side. Heat transfer enhancement is observed for all studied configurations of DPHX compared to the plain DPHX. The helical inserts and strips increase the effective surface area, and also create secondary flows and higher mixing in tube- and annulus-side. Considering the overall heat transfer coefficient of the DPHXs as the comparison criterion, the optimum configuration is selected. A comprehensive parametric analysis is conducted on the optimum configuration to study the effect of relevant operating and geometrical parameters. Increasing the number of helical periods and helical fins in the tube- and annulus-side leads to enhanced overall heat transfer coefficient of DPHXs. The effect of using alumina–water nanofluid flowing in the tube-side is investigated for the optimum configuration. The rate of overall heat transfer enhancement is found to be higher in configurations with more intense mixing, due to more uniform nanoparticle distribution. Exergy analysis is performed to obtain the exergy efficiency of the DPHXs with different configurations. The effect of different operating and geometrical parameters on the exergy efficiency is investigated for the optimum configuration.