Fluid In Tube Research Articles

Optimizing phase change composite thermal energy storage using the thermal Ragone framework

Optimal design of thermal energy storage devices can allow systems to approach specific design objectives while maintaining desired levels of performance. The thermal Ragone framework has been applied to the design of thermal energy storage heat exchangers, specifically identifying relationships between their power and energy capabilities. In this paper, a finite-difference model is used to optimize thermal storage heat exchanger designs for three objectives given a discharge power constraint. The three objectives are maximizing energy density, minimizing energy-specific capital costs, and minimizing the levelized cost of storage. This study focuses on the design of planar thermal energy storage heat exchangers with phase change materials and thermal conductivity additives. Key design parameters identified included the conductivity additive volume fraction, spacing between heat transfer fluid tubes, and the phase transition temperature. The optimal design is found to depend strongly on the required thermal power, with higher powers requiring transition temperatures further from the use temperature, more conductivity additives, and closer tube spacing. There is also a trade-off between these design parameters, where changing one (e.g., closer tube spacing) can allow another parameter to be relaxed (e.g., less conductivity additive). To aid in future device design, models of reduced complexity were developed and evaluated for their ability to predict optimal designs. These simplified models can predict the performance of thermal energy storage heat exchangers up to 5000 times faster than the finite-difference model. For the design objectives of maximizing energy density, minimizing costs, and minimizing levelized cost of storage, the simplified models predicted optimal designs with average absolute deviations below 2 % in relation to the optimal designs chosen by the finite difference model optimization. These models can serve as tools to further study thermal storage heat exchangers incorporating the realistic trade-off between the device's power and energy.

Three-dimensional flows of incompressible Navier–Stokes fluids in tubes containing a sinus, with varying slip conditions at the wall

The objective of this study is to understand the formation of vortices and other flow characteristics associated with the three-dimensional motions of an incompressible Navier–Stokes fluid in tubes containing a sinusoidal extension. The study has some bearing on two conjectures that da Vinci made concerning the flow of blood through the aortic root. We investigate how the flow attributes change with increasing sinus radius and with the nature of the slip at the tube wall characterized by the parameter θ , 0 ≤ θ ≤ 1 , with θ values being 0 for free slip and 1 for the “no-slip” (adherence) condition. Two time-dependent solvers – one fully three-dimensional and the other based on the assumption that admissible flows are axially symmetric – are used to solve the equations governing the flow in a geometry associated with the inflow velocities and the other conditions closely related to flows of blood in a blood vessel containing the aortic root. Both these solvers passed a benchmark test based on steady flow in a cylinder with different slip conditions. Computing the flows systematically using both solvers, focusing first on problems with constant-in-time inflow, we have found that for the circular cylinder with constant cross-section, serving as the reference domain, the flow is steady and unidirectional for all boundary conditions that are considered, with maximal vorticity and dissipation for no-slip. For tubes with the sinus radius up to 16 mm the flow remains steady and axially symmetric, but the vorticity and the bulk dissipation in the sinus are maximal for θ between 0.6 and 0.7. For a tube with the sinus radius of 20 mm the flow remains steady and axially symmetric only for θ greater or equal than 0.9 including the case of no-slip. For θ below this value, not only does the solution become unsteady (oscillatory or even chaotic), it does not converge to the steady state and is thus different from the corresponding axially symmetric flows, and also the total dissipation and the vorticity depend on θ in a non-monotone manner. In particular, for a tube with sinus radius of 20 mm, the bulk dissipation and the vorticity are the highest for θ = 0 , i.e. for (free) slip of the fluid at the wall. For tubes with the sinus radius of 20 mm and for θ below 0.9, we computed two different solutions (one steady, axially symmetric, the other unsteady, fully three-dimensional) to three-dimensional evolutionary incompressible Navier–Stokes equations for the same set of the initial and boundary data. This last result supports the idea that, under the conditions considered, the axially symmetric solution looses its stability. Finally, we computed the problems with a pulsatile inflow. For the tube with the largest sinus radius of 20 mm, we observed that the full problem is axially symmetric for the slip parameter θ ≥ 0 . 9 , while for more significant slip, i.e. for θ < 0 . 9 , we again obtained two different solutions under the same initial and boundary conditions.

Laminar convective heat transfer in helical twisted multilobe tubes

Augmentation of heat transfer performance has long been the main interest in thermal fluid engineering sector. Some commonly adopted thermal enhancement methods are adoption of helical tubes, twisted tubes and multilobe cross-sections. Several studies reported further enhancement when combination of these methods were implemented. Despite their promising potential, no investigation on the performance of heat transfer in helical twisted multilobe tubes has been reported. Therefore, present study is conducted with the main objective to study the laminar convective heat transfer of Newtonian fluid in a helical twisted multilobe tube through computational fluid dynamics (CFD) simulations. A three-dimensional model was developed with accordance to principles of fundamental conservation. The model was validated against available experimental data for which a good agreement was achieved. The model was thus utilised to investigate the fluid flow and heat transfer in the studied tube within a range of certain parameters, such as, number of lobes, number of twists, inlet Reynolds number as well as the geometry of the pipe (straight and helical). The performances of heat transfer of the investigated configuration are evaluated using the typical Nusselt number, friction factor and performance index (PI), which is a ratio between average Nusselt number and friction factor under constant pumping work condition. The results reveal that adding the number of lobes alone has negligible effect on the performance. However, combination of number of lobes and tube twisting result in considerable changes on the heat transfer coefficient with marginal effect on the friction factor. This is especially pronounced for tube with even number of lobe (bilobe and quadrilobe). Overall, helical coiled tube performs better within the range of Re 500 to Re 2000 as the performance index averagely increase by 18.4% as compared to straight tube, whereas below Re 500, straight tube is slightly outperforming the helical tube (3.65%). Twisting of the tubes result in the opposite effect, i.e. it improves the performance of straight tube but deteriorate the performance of helical tube. Thus, twisting is recommended primarily for straight tubes. Highest performance index yielded is 7.01 by bilobe helical tube without twist at Re 2000. Lastly, correlations for friction factor and Nusselt number are developed for straight and helical multilobe twisted tube within studied range. This correlation can serve as quick design tools for non-conventional heat exchanger utilizing twisting multilobe tubes.

Study on temperature drop and cooling effect of cold wall for backfill body with embedded cold fluid tube

In recent years, the thermal damage in deep mine has become an urgent problem to be solved. A three-dimensional heat transfer model of backfill body with embedded cold fluid tube was established, the influence of tube spacing, the inlet temperature and velocity of cold fluid and the thermal conductivity of backfill body on the temperature distribution and cooling capacity of cold wall were analyzed. The results show the cooling capacity at steady deceases from 11.72 kW to 4.16 kW when tube spacing increases from 0.5 m to 1.5 m, the cooling capacity increases by 2.06 kW when inlet temperature decreases by 4 °C. When thermal conductivity increases from 0.5 W/(m•°C) to 2.0 W/(m•°C) in 0.5 W/(m•°C) increment, the increment of cooling capacity is about 3.22 kW, 2.17 kW and 1.52 kW successively on average in 20 days–60 days. Comparison shows the wall temperature of backfill body obviously decreases and quickly forms the cold wall as cold fluid passing through tube, the cold will be released rapidly from cold wall to airflow. The research can provide the theoretical basis for the application of radiation cooling of backfill body in the control of mine thermal damage.

Analysis on the heat transfer performance of supercritical liquified natural gas in horizontal tubes during regasification process

The submerged combustion vaporizer (SCV) is an indispensable peak-shaving heat exchanger in the regasification process of liquified natural gas (LNG). This paper mainly studies the trans-critical heat transfer performance of LNG in the horizontal tube of SCV under the convective heating condition. To this end, the conditions of fluid temperature, mass flux, and tube diameter are comprehensively investigated through numerical simulation. Based on the simulation results, the influence of the buoyancy on total and local heat transfer performance is analyzed from the distribution of flow field and thermal-physical property in the boundary layer. The results indicate that the buoyancy leads to a significant difference in convection thermal resistance around the circumference. Tube diameter and mass flux affect the degree of heat transfer strengthening in the lower part and heat transfer deterioration in the upper part of the tube, as well as the occupied circumferential proportion of the corresponding region. Considering the effects of local heat transfer strengthening and deterioration, buoyancy shows an enhancement effect overall on the heat transfer process, especially under the conditions of low mass flux and large diameter. Based on the mechanism analysis of the convective heat transfer, two correlations are proposed to calculate the local convection thermal resistance in the buoyancy strengthening and buoyancy deterioration region, respectively.

Numerical Analysis of Flow-Induced Vibration of Heat Exchanger Tube Bundles Based on Fluid-Structure Coupling Dynamics

According to the needs generated by the industry, there is an urgent need to investigate the flow vibration response law of the elastic tube bundle of heat exchangers subjected to the coupling effect of shell and tube domain at different inlet flow velocities. In this paper, based on the continuity equation, momentum equation, turbulence model, and dynamic grid technology, the vibration response of the elastic tube bundle under the mutual induction of shell and tube fluids is studied by using pressure-velocity solver and two-way fluid-structure coupling (FSC) method. The results show that the monitoring points on the same connection block have the same vibration frequency, while the vibration amplitude is different. Monitoring point A is the most deformed by the impact of fluid in the shell and tube domain. When the inlet velocity( v shell = v tube = 0.15 , 0.4, 0.5 m/s) of shell and tube is low, the amplitude of tube bundle vibration in the Y direction is greater than that in X and Z direction, and the tube bundle produces periodic vibration in the vertical direction. The vibration equilibrium position of the tube bundle along the shell flow direction gradually moves up with the increase of the inlet velocity. The amplitude in the Y -direction of the elastic bundle decreases with the increase of shell-side and tube-side velocity. The relationship between the vibration amplitude in the Y direction and the entrance velocity is a linear function.

Numerical analysis of solar energy storage within a double pipe utilizing nanoparticles for expedition of melting

The current work proposes the combination of thermal storage and solar concentrating systems. To improve the low conduction mode of pure paraffin, not only the new style of fins but also dispersing ZnO nano-powders were suggested. The numerical procedure has been verified with the reported outputs in previous literature and good accommodation has been demonstrated. The utilized technique for modeling transient charging phenomena is enthalpy-porosity in which homogeneous model for prediction of paraffin properties were proposed. To determine the efficacy of angle of star-spline fins, simulations for all three proposed configurations have been done and outputs have been summarized in contours and plots. In existence of sunlight, the reflector makes the sun rays to concentrate along absorber tube and temperature of testing fluid augments. Such hot fluid flows within the inner pipe of double pipe system which contains paraffin in annulus region. With change of θ from 30° to 45° and 60°, the melting period saved to 13.14% and 18.61%, respectively. Adding ZnO nanoparticles help to augment the conduction mode and melting period declines around 4.79%. The lowest needed time for melting is about 4.88 h which is associated to case with φ = 0.035 and θ = 60°. • The combination of thermal storage and solar concentrating unit was proposed. • Dispersing ZnO nanoparticles and installing star-spline fins were applied. • With change of θ from 30° to 60°, the melting period saved to 18.61%. • Adding ZnO nanoparticles help to reduce melting period around 4.79%. • The quickest process occurs when φ = 0.035 and θ = 60°.

Melting and solidification characteristics of a semi-rotational eccentric tube horizontal latent heat thermal energy storage

• Effect of eccentricity was investigated for the latent heat thermal energy storage. • Bottom eccentricity significantly improved the melting process. • Top eccentricity showed the potential to enhance the solidification process. • A novel semi-rotation of the storage system was proposed. • An optimum eccentricity was justified, and key parameters were investigated. Research showed that bottom eccentricity improved the melting performance in the horizontal shell-and-tube latent heat thermal energy storage (LHTES) system. However, it largely reduced the solidification performance. To solve this problem, this study investigated the effects of different eccentric positions of the inner heat transfer fluid (HTF) tube on the thermal performance of a horizontal shell-and-tube LHTES system during the melting and solidification processes. A novel technique with the intermittent rotation of the LHTES device was proposed to take the advantage of eccentric tube configurations for enhancing both the melting process during charging and the solidification process during discharging. Numerical simulations were conducted and validated in the FLUENT application of ANSYS software by utilizing the enthalpy-porosity method. Liquid fraction, average temperature, energy storage rate, and velocity distribution were used to evaluate the LHTES system thermal performance. Results showed that the bottom eccentricity significantly improved the melting process, however, it slowed down the solidification process. But the further study found that the top eccentricity could enhance the solidification process. Based on the average energy storage rate, the optimum bottom eccentricity laid between 0.60 and 0.75 for the charging process, which improved the melting rate by 64–74%. However, the optimal top eccentricity was between −0.15 and −0.30 for the discharging process. The proposed novel rotational technique well adapted the bottom eccentricity to improve the melting process during charging and the top eccentricity to enhance the solidification process during discharging. It was found that an optimal eccentricity of 0.30 could well tradeoff between the bottom eccentricity for charging and top eccentricity for discharging process in the proposed approach. Both the HTF cooling temperature and shell-to-tube radius ratio did not show a significant impact on the optimal eccentricity of the LHTES system.

Melting dynamics analysis of a multi-tube latent heat thermal energy storage system: Numerical study

This numerical study investigates the melting dynamics of paraffin wax as a phase change material (PCM) in a multi-tube latent heat thermal energy storage system (MT-LHTESS). The performance of an arrangement with four tubes is compared with a concentric single tube arrangement keeping the same cross-section area of heat transfer fluid tubes and the same PCM quantity. Four longitudinal fins of two types are also incorporated to further improve the melting. Thirteen cases with different arrangements of tubes and fins are compared in this study. The study attempts to select a suitable arrangement of the tubes. A two-dimensional enthalpy-porosity model in ANSYS-Fluent is used to solve the governing equations. The melting results are depicted as the contours of liquid fraction, temperature, and flow streamlines. The transient performance is assessed based on progress plots of liquid fraction and average domain velocity. It is observed that splitting into multiple tubes and using fins enhance the melting performance. The generation and coalescence of small vortices in the molten PCM accelerate the melting performance. The staggered array, larger eccentricity, and (+ type) finned tubes outperform their counterparts. The lowest melting time is observed in Case 2(+), having four staggered tubes, at 30 mm eccentricity, and with (+ type) fins. This case takes 75 min for complete melting, and 1411.1 kJ/m heat at a rate of 322 W/m is stored. The melting time gets reduced by 53.3–71.1% using four tubes and by 65.78–83.33% using finned four tubes as compared to the single tube case.

A comprehensive study on melting enhancement by changing tube arrangement in a multi-tube latent heat thermal energy storage system

In this study, the paraffin wax's melting dynamics in a multi-tube latent heat thermal energy storage system are investigated. The performance of ten arrangements of five heat transfer fluid tubes is compared. The radial eccentricity of four planetary tubes is varied around a fixed central tube. The study aims to find an appropriate arrangement of multiple HTF tubes keeping the same PCM content and heating surface. A simplified two-dimensional computational domain was considered, an enthalpy-porosity based melting model was designed, and the governing equations were solved using ANSYS-Fluent. The melting sequence in various cases is represented as the liquid fraction contours, flow streamlines, and temperature contours. The performance of proposed designs is assessed on the basis of transient plots of liquid fraction, average domain velocity, and heat flux at the outer surface of the heat transfer fluid tube. It is observed that the melting dynamics are greatly influenced by the tube arrangement. The coalescence of small vortices and the intermixing of different temperature layers accelerate the melting. It is found that the tubes in the top half should be placed closer to the center to delay thermal stratification, and in the bottom half should be placed deeper into the poor melting zone. The staggered arrangement of planetary tubes outperforms the inline arrangement at given eccentricities. The fastest and slowest melting is realized by Case 9 and Case 1, which take 128 and 269 min, respectively, for melting. The proposed designs can store 1450 kJ/m of energy with 98 % theoretical efficiency.

RANCANG BANGUN DAN ANALISA PERFORMA ALAT PENUKAR PANAS DOUBLE PIPE MENGGUNAKAN METODE LMTD: SEKALA LABORATORIUM

A heat exchanger is a tool that is used to increase or reduce fluid temperatures. One type of this tool is a type of double pipe, this type is the simplest if compared to other types of heat exchanging devices, where hot fluid flows in the inner tube and cold fluid flows in the anulus. This study aims to analyze the efficiency of laboratory scale heat exchanging devices with water hot and cold fluids. The result shows the average effectiveness of this equipment is 20% this result is better when compared to several other studies which on the laboratory scale only show maximum efficiency at 17%. The fouling factor is an obstacle that causes a decrease in the effect of heat exchangers, the greater the fouling factor, the greater the heat resistance caused by the pipe. This study shows the amount of Fooling factor of 0.006, the value is greater than the available Fouling Factor constant. The results stated that there is a relationship between remediable numbers (Reynold numbers) with the amount of heat transferred by heat fluid. The greater the value of Reynold the greater the expressed heat. Even though it has high efficiency, this equipment can still not be used because of some considerations such as low efficiency and efficient..

Thermal Performance Analysis of a Linear Fresnel Concentrating Solar Collector Absorber Tube

Linear Fresnel solar collectors are suitable for a wide range of applications, which include steam generation for power generation, industrial process heat, solar cooling, institutional and domestic hot water production etc. The thermal performance of a linear Fresnel solar collector absorber tube was investigated in this study for different fluid mass flow rates, heat flux intensities, heat transfer fluid inlet temperatures, ambient air temperatures and external loss heat transfer rate. Turbulent flow liquid water heat transfer fluid and uniform circumferential heat flux distribution boundary were considered under steady-state conditions. The fluid flow was considered incompressible. This study was limited to a first order model approximation for thermal performance of a linear Fresnel solar collector absorber tube. The heat transfer fluid and absorber tube material properties were considered constant and independent of temperature. The results indicated that the absorber tube outlet heat transfer fluid temperature decreased with an increase in the Reynolds number and increased with the heat flux intensities. Thermal efficiency increased with an increase in the heat transfer fluid mass flow rate and however, decreased with increase in pressure drop and the consequent pumping power requirement. It was also found that the thermal efficiency of the collector decreased with an increase in the fluid bulk inlet temperature and decreased with an increase in the external loss heat transfer rate.

Numerical simulation of the heat transfer process of a coiled tube for viscous fluids

This study presents the results of a numerical simulation in a helical coiled tube for Newtonian and non-Newtonian fluids in laminar regime. As a practical contribution, the numerical simulations use non-Newtonian fluids, the rheological properties of which are experimentally measured. In both non-Newtonian fluids, at the helical section, the heat transfer rate was higher than that at the straight section. For the fruit juice, the heat transfer coefficient ( h w ) reached values of 1000 and 1350 W/m 2 K at the coil, which were 73% and 126% higher than in the straight section, for an Re g of 255 and 634, respectively. For the carboxyl methyl cellulose solution, these differences ranged between 76% ( Re g = 255) and 210% ( Re g = 634), reaching h w values at the coil of 1950 and 2700 W/m 2 K. In all non-Newtonian cases, fluid mixing was improved at the coil section. This influenced the viscosity variability along the coil, especially for the fruit juice, with a pronounced pseudoplastic behaviour (flow behaviour index of 0.5). This viscosity variation was more influenced by the strain rate than the viscosity change with temperature, as the fruit juice showed a moderate energy activation (8.2 kJ/mol). • High computational cost model used for helical coiled tube. • Numerical simulation of Newtonian fluids validated with experimental setup. • Good agreement obtained between numerical and experimental results. • Local Nusselt number increased at the coiled section up to 210%.

Enhanced electroosmotic flow, conductance and ion selectivity of a viscoplastic fluid in a hydrophobic cylindrical pore

We have studied the electroosmotic flow (EOF) of a non-Newtonian viscoplastic fluid, modeled as a Herschel-Bulkley (H-B) fluid, through a single hydrophobic nanopore in a uniformly charged solid hydrophobic membrane separating two identical reservoirs. An interfacial slip velocity develops when the viscoplastic fluid is strained over a hydrophobic surface. It is well established in the context of Newtonian fluid that the interfacial slip at the charged surface augments the EOF. For the viscoplastic fluid, the EOF depends on the fluid behavioral index and the yield stress. We have illustrated the impact of the interfacial slip on the EOF, conductance and ion selectivity of the cylindrical nanopore at different yield stresses for both the shear thinning and the shear thickening cases of the H-B fluid. The slip velocity, characterized by the slip length, enhances the average flow and conductance of the pore and this impact is pronounced for the shear thinning case. The unyielded zone, which develops along the central line of the pore, contracts as the slip length is increased. The ion concentration polarization enhances for the shear thinning fluid, however, the slip length creates a marginal increment. The counterion selectivity of the pore is found to be significant for the Newtonian case as compared to the non-Newtonian fluid and the velocity slip enhances the ion selectivity further. We have determined an analytic solution for the EOF of a power-law fluid in a long hydrophobic tube. Our computed solution for the case of a long tube effectively coincides with this analytic solution. An increment in the pore length reduces its conductance but enhances the ion selectivity. The increment of the average EOF for the hydrophobic pore as compared to the no-slip case grows as the pore length is increased.

Effects of arrow-shape fins on the melting performance of a horizontal shell-and-tube latent heat thermal energy storage unit

A numerical investigation was carried out to analyze the melting characteristics of phase change materials (PCM, specifically n-octadecane) in a horizontal shell-and-tube latent heat thermal energy storage (LHTES) system that exhibit low-speed melting of the PCM within the lower half of the unit, thus limiting its utilization in practical applications. Novel arrow-shape longitudinal fins were added to improve the overall heat transfer, including both conduction and natural convection. A two-dimensional symmetric simulation model featuring the Boussinesq approximation and an enthalpy-porosity model was employed. The case with bare heat transfer fluid (HTF) tube was compared with finned tube cases of 6 configurations. Three different fin branch angles (θ = 40°, 50°, and 60°) and four fin length ratios (ϒ = 0, 0.222, 0.571, and 1.198) were studied, with ϒ related to the gap distance between the bottom of the heated tube surface and the fin branch. The trends of the liquid fraction, average temperature of the PCM, and total heat transfer rate through the outer surface of the inner tube with the fins featuring two distinct fluctuating stages were presented. Progression of the melt front, temperature distribution and velocity vector/streamline fields were also provided. Common to all cases, persistence of a time-dependent rising thermal plume originating from the top surface of the heated inner tube was observed. Depending on the orientation of the branched fin and its distance from the inner tube, similar thermal plumes rising from the top surface of the branched fin cooperated with the molten PCM in the top one half of the annulus in realizing expedited melting. These cases exhibited a variety of recirculating vortices and enhanced natural convection within both halves of the unit. The results showed that increasing the fin angle while using a fixed fin length ratio of ϒ = 0 improved the melting rate of the PCM. When the fin ratio was varied from 0 to 1.198 while the fin angle was invariant (θ = 60°), the melting time was observed to prolong. The case with θ = 60° and ϒ = 0 exhibited the highest heat transfer enhancement than other arrangements. In effect, when the branch fin angle is increased and the fin length ratio is reduced, greater amount of PCM is subjected to natural convection. At the same time, heat conduction is enhanced below the branched fin since less volume of the solid layer PCM existed there.

Non-Contact And Non-Steady Rheo-Optical Measurement Of Hydrodynamic Stress Fields Inside A Cylindrical Tube

For measuring non-contact and non-steady rheo-optical measurement of hydrodynamic stress fields, we utilize a high-speed polarization camera that captures an unsteady phase-retardation field. It is known that the retardation has a proportional relationship to secondary principal stress difference. A solution of sodium iodide including crystal polymers (CNCs, cellulose nano crystals) was used as the working fluid. We have successfully measured the retardation induced by flow birefringence of CNCs without compromising the Newtonian fluid properties of the solution. In this paper, we propose a visualization technique for the retardation field of fluid in a cylindrical glass tube that incorporates index matching and discuss its comparison with the spatial intensity distribution of theoretical hydrodynamic stress field. Experimental results show that the retardation increases with an increase in flow rate. In addition, by utilizing the orientation angle data measured with the high-speed polarization camera, the vector field of principal stress difference is visualized, which is suggested to be useful for confirming the effects of direction of stresses. To investigate whether the measured retardation filed agrees with the theoretical secondary principal stress difference, the spatial intensity distribution of the two was compared. The overall trend agrees well while the retardation at the center of the tube is different, possibly owing to the effect of structure-induced retardation due to self-assembly of CNCs. The structure-induced retardation data were obtained by a combined measurement of a rotational rheometer and the high-speed polarization camera. As a result, the theoretical secondary principal stress difference distribution with considering structure-induced retardation showed better agreement with the retardation field than the case without considering it.

Dynamic response of Maxwell fluid in an elastic cylindrical tube

In the present study, the dynamic response of Maxwell fluid in an elastic cylindrical tube is considered. Focusing on the viscoelastic flow through a thin-walled slender elastic cylindrical shell and neglecting inertia in the liquid and solid, a non-homogeneous linear diffusion equation controlling the coupled viscous–elastic system is obtained. The fluid pressure and deformation fields are obtained by numerical Laplace inversion. The results show that the relaxation time of Maxwell fluid has a significant effect on the flow and deformation fields of the viscoelastic system. This research can be used for the design and control of complex time-varying deformation fields and has a certain value for the applications of soft actuators, micro-autonomous systems, and soft robotics.

Novel usage of the curved rectangular fin on the heat transfer of a double-pipe heat exchanger with a nanofluid

The convection heat transfer in a countercurrent double-tube heat exchanger with various fins in a turbulent flow is investigated. The suitable heating or cooling process of fluids is the effective use of the double-pipe heat exchanger. We use water-aluminum oxide nanofluid and water-titanium dioxide at four concentrations (0.4%, 2%, 4%, 6%) as the cold fluid in the inner tube and water as the hot fluid in the annular space. The single-phase model for nanofluid modeling and the standard k-ε model with scalable wall function for simulating the turbulent flow is utilized. To better examine this novel geometry, its performance is compared with simple and rectangular-finned geometries. The results show that the water aluminum oxide nanofluid has a better convection heat transfer coefficient than water titanium dioxide and pure water. Raising the nanofluid concentration from 0.4% to 6% increases the convection heat transfer coefficient by 12%. Heat exchangers with a rectangular and curved fin have 81% and 85% better efficiency than the heat exchanger without a fin. The novel geometry causes a smaller pressure drop despite its higher convection heat transfer coefficient. Also, it is shown that with raising the Reynolds number and nanofluid concentration, the pressure drop increases.

Numerical investigation of energy desorption from magnesium nickel hydride based thermal energy storage system

The use of dual metal hydride system for thermal energy storage consists of high and low-temperature metal hydrides. In this study, a 3D cylindrical Magnesium Nickel hydride bed is analyzed for thermal energy discharge. The energy discharge from metal hydride bed initially at temperature of 400 K, a heat transfer fluid at 500 K temperature is supplied to extract the heat generated due to exothermic chemical reaction. In this article, variation of the number of heat transfer fluid tubes and effect of variation of aspect ratio (ratio of diameter to height) on energy desorption and heat transfer from metal hydride bed is performed. The optimal number of heat transfer fluid tubes is determined for various aspect ratios. The temperature variation of the metal hydride bed with an increase in the number of heat transfer fluid tubes is analyzed. The study of aspect ratio variation on energy desorption and heat transfer characteristics is analyzed for three aspect ratios 0.5, 1, and 2. The variation of thermal energy desorbed, net heat transfer and temperature variation of metal hydride bed are analyzed. The adequate number of heat transfer fluid tubes for AR 0.5, 1, and 2 is identified as 32, 48, and 72, respectively. The cumulative heat released from MH bed with AR 0.5, 1, and 2 is 350.94 kJ, 330.56 kJ, and 310.42 kJ, respectively. The study will be useful in designing the optimized metal hydride bed reactor for thermal energy storage applications.

Combined convective and viscous dissipation effects on peristaltic flow of Ellis fluid in non uniform tube

Abstract:&#x0D; This paper investigates the peristaltic transport of Ellis fluid in a non-uniform tube with combined/individual effects of convective and viscous dissipation analytically. Low Reynolds number and long-wavelength approximation assumptions are considered in the analysis. An examination of the properties of the walls is also carried out. The expressions for velocity, temperature profile, and stream function are obtained subjected to convective boundary conditions. The peristaltic transport's significant characteristics are delineated with plots for various Ellis fluid parameter values. The viscous dissipation effects are found to be related to the Brinkman number, so it leads to rising fluid temperature in all cases.