Triplex Tube Research Articles

Modeling of the damage and fracture behaviors of a SiC triplex tube during the burst test with elastomeric insert

The Silicon Carbide (SiC) triplex cladding tube has been regarded as one of the leading structures for the next-generation light water reactors, because of its larger safety margins under beyond-design basis transient conditions. In this study, a numerical simulation method is developed to reproduce the damage and fracture behaviors of a nuclear-grade SiC triplex cladding tube during the burst test. Especially, a three-dimensional continuum damage mechanics based (CDM-based) constitutive model is developed and validated for the SiCf/SiC composites, with the predictions agreeing well with the experimental data under different loading conditions. By introducing cohesive surfaces in the monolithic layers of a SiC triplex tube, cracking of the monolithic layers and the subsequent local damage behaviors within the SiCf/SiC composite layer are captured. The local tensile strength of ∼402 MPa is identified for the monolithic layers, corresponding to the first load drop during the burst test. The simulation results indicate that cracking of the monolithic layers leads to sharp increases in the locally enhanced hoop stresses and damage factors for the SiCf/SiC composite layer, with slight influences on the field variables far away from the main crack; after the fast increase the evolution velocity of local damage factors slows down, reflecting the toughening effects of SiCf/SiC composite. An assessment strategy for the gas leak tightness and structural integrity of the SiC triplex cladding during the accident sceneries is proposed to predict failure of the SiCf/SiC composites with the critical damage factor, and it is necessary to simulate the damage and fracture behaviors in the multi-layer models with the cracking process of monolithic layers involved.

Melting Behavior Effect of MXene Nanoenhanced Phase Change Material on Energy and Exergy Analysis of Double and Triplex Tube Latent Heat Thermal Energy Storage

Abstract The impacts of melting behavior on the thermal performance of triple tube thermal energy storage (TT-TES) and double tube thermal energy storage (DT-TES) systems employing cetyl alcohol and 3% v/v. MXene nano-enhanced PCM (NEPCM) are compared and numerically evaluated in this work. For both the DT-TES and TT-TES systems, the following were investigated in connection to melting time: system efficiency, discharged energy, heat transfer rate, exergy destruction, entropy generation number, exergetic efficiency, melting fraction, and melting temperature contours. In addition, the effect of Stefan, Rayleigh, and Nusselt numbers on Fourier numbers are compared for the DT-TES and TT-TES systems with MXene NEPCM. MXene-based nano-enhanced PCM melting in TT-TES displayed 6.53% more Stefan number than cetyl alcohol. DT-TES with pure cetyl alcohol phase change material (PCM) consumes 0.4% more energy at 7800 s than MXene NEPCM. Pure melting of MXene-based nano-enhanced PCM in a TT-TES had 4.16% higher storage exergy than cetyl alcohol. The entropy generation number of pure melting of MXene-based nano-enhanced PCM in TT-TES is 7.93% lower than that of cetyl alcohol. Pure melting of MXene-based nano-enhanced PCM in TT-TES reduces storage energy by 1.95% over cetyl alcohol. Pure cetyl alcohol has 76.99% optimal system efficiency at 5400 s melting time and MXene NEPCM 77.04% at 4800 s in DT-TES. The charging temperature for pure cetyl alcohol PCM in TT-TES is 0.7% lower than in DT-TES. Furthermore, pure melting of MXene-based nano-enhanced PCM in a TT-TES has 1.95% lower storage energy than cetyl alcohol. For a given volume of MXene-based nano-enhanced cetyl alcohol PCM, melting occurs more rapidly in a TT-TES system.

Melting performance of PCM with MoS2 and Fe3O4 nanoparticles using leaf-based fins with different orientations in a shell and tube-based TES system

Phase change materials (PCMs) are frequently utilized in the thermal sector, especially for thermal energy storage (TES) applications. The purpose of this study was to analyze the thermal efficiency and melting characteristics of a leaf-vein-shaped fin in a triplex tube heat exchanger. The analysis focused on the use of pure molten salt PCM and a combination of molten salt PCM with MoS2 and Fe3O4 nanoparticles. The study utilized ANSYS Fluent software to conduct numerical simulations and analyze seven distinct fin arrangements. The simulations were employed to visualize and examine the liquid fraction, temperature, and fluid velocity. The findings indicated that the leaf-vein fin shape greatly improved the dispersion of liquid fraction, average temperature, and velocity in comparison to alternative fin designs. The addition of MoS2 and Fe3O4 nanoparticles significantly enhanced the melting and thermal characteristics of the PCM as a result of heightened thermal conductivity. This showcases the capability of the leaf-vein fin design and PCM nanocomposites to enhance the efficiency of thermal energy storage in triplex tube systems. About 2500 s PCM melt about 36% for case A, but melting rate enhance up-to 55% using nano particles. Melting rate enhance 91% in 1000 s in case of G using 8 fins as compare to case A having no fins.

Expression of Concern for article entitled “Entropy generation characteristics of phase change material in a variable wavy walled triplex tube latent heat storage unit for battery thermal management system”

Expression of Concern for article entitled “Entropy generation characteristics of phase change material in a variable wavy walled triplex tube latent heat storage unit for battery thermal management system”

Computational study on transient thermal performance enhancement of phase change materials in triplex tube heat exchanger through novel annular-finned configurations

The introduction of highly conductive media to enhance the thermal performance of phase change materials (PCM) is an efficient method to counter the inherently low thermal conductivity of PCMs while retaining its benefits. This article reports the transient thermal performance of PCM in novel finned configurations based on Triplex Tube Heat Exchangers (TTHX). The shape, size, and placement of the constituent fins in the PCM domain are varied, and their effect on the transient melting rate of PCM is studied. Two PCM formulations, RT-82 and RT-35 are evaluated. Pockets within the encapsulation geometry wherein a vortex-like melting pattern of PCM can be facilitated, are identified as factors for expediting the melting process. The best performing configuration resulted in ∼17% (RT-82) and ∼9% (RT-25) reduction in melt duration compared to the baseline configuration. The effects of gravity conditions on the PCM melt process of the best performing and baseline configurations were also studied.

Exploring the impact of inner and middle channel geometries on the melting rate of PCM-metal foam composition in a triplex tube heat exchanger

Triplex tube heat exchangers (TTHXs) are devices suitable for storing thermal energy with PCM because they shorten the melting and solidification periods. Studies in literature have revealed that pipe geometries significantly affect the melting performance of PCM in thermal energy storage with TTHX. In the pipe designs carried out in these studies, convection in the heat transfer fluid (HTF) and the heat transfer surface areas of the pipes were considered. However, in addition to convection in the HTF, heat transfer by conduction and convection within the PCM also significantly affects the melting performance. The novelty of this study was to investigate the effects of inner and middle channel combinations with different geometries in TTHX on conduction and natural convection mechanisms in PCM combined with metal foam. Numerical analyses were carried out for nine inner-middle channel combinations with three different metal foam porosity values (ε = 0.85, 0.90 and 0.95). At porosity values of 0.85 and 0.90, the highest melting rate was achieved with the triangle-triangle inner-middle channel combination within a certain period, and the charging time was shortened by 16.67 % and 14.44 %, respectively, compared to the base case (circle-circle). For the porosity value of 0.95, it was observed that the most suitable channel combination for melting performance was circle-circle, as natural convection flow became more dominant in heat transfer in liquid PCM. At the porosity value of 0.95, the charging time with TTHX containing the circle-circle combination decreased by values ​​ranging from 29.75 % to 59.86 % compared to other combinations.

Enhancement of solar evacuated tube unit filled with nanofluid implementing three lobed storage unit equipped with fins

This study discusses an evacuated tube collector-type solar water heater (ETCSWH) using a phase change material (PCM) chamber with fins, nanofluid, and nano-enhanced phase change material (NEPCM). First, the charging phenomena in a horizontal triplex tube heat exchanger (TTHX) equipped with fins, natural convection, and an ETCSWH system without PCM is simulated to validate the solution. The impact of adding fins and nanoparticles with a volume fraction of 3% of Al2O3 and Cu to paraffin wax and water-based fluid, respectively, on the unit's efficiency has been examined. The proposed system for the PCM melting process, heat storage, fluid flow behavior in the system, and velocity distribution and temperature contour in the storage tank and three parts of the absorber tube have been evaluated using ANSYS FLUENT software in a three-dimensional and transient simulation. The results show that Case 8 has improved by 39.7% compared to Case 1 and Case 4 by 5.2% compared to Case 1 within 4 h of the melting process. Also, Case 8 with a 43% and 6.4% shorter melting time than Cases 1 and 5 has the best performance and the greatest heat transfer rate. The productivity of the ETCSWH system is considerably enhanced by the use of fins, NEPCM, and nanofluid.

Analysis of energy and exergy of eutectic phase change material solidification for various configuration-based triplex tube

This study delves into the energy and exergy analysis of eutectic PCM solidification within a triplex tube latent heat storage unit featuring inner tubes of triangular, pentagonal, square, and circular configurations, analyzed numerically. Results encompassing the impacts of mean temperature, solidification temperature, melting fraction, exergetic efficiency, exergy destruction, heat transfer rate, entropy generation number, and system efficiency on solidification time are presented and compared using contour maps and figures. The research also scrutinizes the effects of Fourier numbers on Stefan, Rayleigh, and Nusselt numbers for TES systems based on inner configurations. Past studies primarily concentrated on cylindrical shapes for all three tubes within triplex-tube heat exchangers, disregarding varied internal tube configurations. This investigation introduces novelty by investigating diverse innermost tube geometries (triangular, square, pentagonal, circular) within a triplex tube heat exchanger. The tangible advantages encompass enhanced thermal efficiency relevant to industries such as oil and gas, chemical processing, food and beverage, and power generation. The inner triangular triplex tube thermal energy storage (TES) system exhibits superior performance over pentagonal topologies, boasting stronger Stefan and Rayleigh numbers by 22.52% and 22.86%, respectively, at Fo = 0.0023. Eutectic PCM solidifies 50%, 65%, and 66% faster within triangular configurations than the triplex tube's pentagonal, square, and circular interiors.However, the pentagonal inner tube topology outperforms the triangular one by 13.36 % at a solidification time of 300 seconds. Eutectic PCM solidifies faster in triangular TTTES systems due to their 0.3%, 1.02%, and 1.10% lower heat transfer temperatures than pentagonal, square, and circular systems. Furthermore, in 1800 seconds of solidification, the triangular inner tube discharges 20.16%, 4.92%, and 3.37% more than pentagonal, square, and circular TES systems. Pentagonal, square, and circular inner tube topologies are 13.36%, 3.01%, and 3.84% less efficient than triangular TTTES systems. TES systems with triangular shapes achieve rapid solidification of eutectic PCM at 305.24K, establishing their efficiency over pentagonal, square, and circular configurations.

Energy and exergy investigation of a eutectic phase change material for a triplex tube thermal energy storage with various configurations

This study investigates the energy and exergy analysis of eutectic PCM melting (80% melting) within a numerically simulated triplex tube latent heat storage unit. The unit features inner pipes arranged in triangle, pentagon, square, and circular configurations. The parameters examined include mean melting temperature, melting fraction, exergetic efficiency, exergy destruction, heat transfer rate, entropy generation number, and system efficiency, all of which influence melting time. Previous research predominantly focused on cylindrical forms for all three tubes in triple-tube heat exchangers, neglecting diverse inner tube configurations. The study innovates by exploring various innermost tube shapes (triangular, square, pentagonal, circular) in a triple tube heat exchanger. The practical benefits include superior thermal performance for industries like oil and gas, chemical, food and beverage, and power generation. The pentagonal inner triplex tube thermal energy storage (TTTES) system outperforms triangular topologies with higher Stefan and Rayleigh numbers by 11.54% and 11.53%, respectively, at Fo=0.000254. In the pentagonal configuration, the eutectic phase change material (EPCM) experiences a melting rate of 75%, 200%, and 225% faster than triangular, square, and circular configurations within the TTTES. Additionally, the pentagonal inner tube stores 2.28%, 6.90%, and 5.60% more energy than its triangular, square, and circular counterparts after 200 seconds of melting. Thus, TES systems based on pentagonal configurations are more efficient in melting, surpassing triangular, square, and circular counterparts with eutectic PCM.

Numerical study of the melting rate enhancement of nano phase change material in a modified shell and tube heat exchanger

The current investigation employs numerical analysis using ANSYS Fluent software to explore the melting behaviour of phase change material (PCM) and nano-PCM in a semi-circular shell and tube heat exchanger, utilizing dual side heating for enhanced conduction and convection rates of heat transfer. The study incorporates aluminium oxide nanoparticles at volume concentrations of 2 %, 4 % and 6 % within paraffin wax and assessing their impact on melting and thermal energy storage rates. Notably, the 2 % nanoparticle volume concentration exhibits an enhanced storage rate as compared to higher concentrations. The increase in nanoparticle concentration from 0 % to 2 %, 2 % to 4 % and 4 % to 6 % results in percentage reduction in melting time of 21 %, 3.51 % and 2.8 % respectively. Semi-circular configuration shows significant improvement in the energy storage rate as compared to the circular triplex tube configuration. The maximum energy storage rate of PCM for the semi-circular and circular configurations is 1.15 kW and 1.04 kW respectively, marking a 9.56 % increase over the circular configuration. Moreover, the semi-circular and circular configurations using nano-PCM achieve a maximum energy storage rate of 1.19 kW and 1.14 kW, representing a 4.20 % increase over the circular configuration.

Improving the charging rate and energy recovery of triplex tube heat storage-based pcm with mono/hybrid nanoparticles

Improving the charging rate and energy recovery of triplex tube heat storage-based pcm with mono/hybrid nanoparticles

Accelerated solidification of PCM via Al2O3/CuO hybrid nanoparticles in triplex tube heat storage

Accelerated solidification of PCM via Al2O3/CuO hybrid nanoparticles in triplex tube heat storage

Geometric optimization of fin structures for accelerated melting of phase change material in a triplex tube heat exchanger

This study aims to optimize the thermal energy storage performance of a novel Triplex Tube Heat Exchanger (TTHX) embedded with Phase Change Material (PCM). The PCM is placed in the inner tube and the outer annulus, while the heat transfer fluid (HTF) flows through the middle annulus section. This TTHX configuration outperforms conventional designs by effectively dividing the PCM volume into two distinct sections, consequently enhancing the interaction between HTF and PCM. The experimental results show that the PCM placed in the inner tube melts faster than the PCM in the outer annulus, indicating a need for fins to enhance heat transfer in the outer annulus. In this regard, several designs of the branched fin structures are proposed for the outer annulus region. Taguchi optimization method is used to identify the optimum fin design configuration by considering branched fin designs (F), their angular placement around the periphery of the middle tube (α), and the branch angle (β) as the independent design factors. The objective is to optimize the fin configuration so as to decrease the melt time of the PCM. All the cases of the L16 Taguchi design array are simulated numerically using the enthalpy-porosity model in ANSYS Fluent 2021 R2. The target parameters are the melt time, average temperature, and the energy storage features which are continuously recorded. The main effects plots of the Taguchi analysis suggest an optimum geometry as the one having fin design of F4 (containing angled and straight branches), α as 60° and β equal to 50°. The optimum fin configuration reduces the melt time by 35 % in comparison to the reference base case design. The energy storage characteristics are also improved with the optimum design storing 267 kJ/kg energy at 71.92 min, while the base case stores 208 kJ/kg at the same time. This gain has been achieved due to faster energy transfer rate which is increased to a value of 0.062 kW/kg for the optimum design as compared to 0.042 kW/kg for the base case, reporting an increase of 47.6 % in the energy transfer rate.

Transient analysis of PCM discharging in a rotary triplex tube with wave-shaped fins

Phase change material (PCM) based thermal storage units have attracted attention in energy storage technology. To improve its effectiveness, researchers have introduced various techniques. In this study, a novel rotary triplex tube with sinusoidal wave-shaped fin design is proposed as a PCM based thermal storage unit, and its performance is compared with a conventional straight fin design. A two-dimensional numerical model is developed for the transient analysis of discharging process of PCM. The discharging process is modelled using enthalpy porosity technique. The validation of the model is done against the experimental result from the literature. The discharging process of PCM is analyzed at different rotational speeds. Thermal performance and fluid flow dynamics are evaluated by analyzing the molten portion, temperature, and velocity variation. The result showed that an increase in rotational speed led to an increase in the discharging rate of the PCM. When there is no rotation or slow rotation (0.05 and 0.1 RPM), the discharging is faster in the unit with straight fins compared to the unit with wave-shaped fins. However, at higher rotational speeds (0.2, 0.3 and 0.4 RPM), discharging is faster in the unit with wave-shaped fins. Overall, this study provides insights into the design and performance of PCM based thermal storage unit and suggests the use of wave-shaped fins for higher rotational speeds to enhance the discharging rate of PCM.

Numerical investigation of the process of melting and solidification within a parabolic trough solar collector using nanoparticles and fins

This study investigates the integration of heat storage and solar concentrating systems utilizing phase-change material (PCM) in a triplex tube parabolic trough solar collector (TTPTSC). The simulated system contains a middle region filled with PCM (RT82), with Syltherm 800 flowing via the inner and outer tubes. The finite volume technique was used to simulate this laminar flow with variable heat flux on the outer wall. This numerical study aims to assess the impacts of adding Alumina and Single-Walled Carbon Nano Tube (SWCNT) nanoparticles at volume fractions of 0 and 0.025, as well as the effects of fin installation, geometry, rim angles (φR), and other relevant parameters on these processes. The addition of nanomaterials in different cases led to significant reductions in melting times, ranging from 7.39% to 8.1%, compared to cases without nanoparticles. In addition, the fins in various cases improved the melting performance compared to the simple case. The melting time reductions ranged from 26.2% to 30.14%, demonstrating how fins can improve heat transfer and accelerate the melting process. The case with seven longitudinal outer fins and a rim angle of 60 had the shortest melting time among the studied configurations.

Accelerating melting time in a triplex tube heat exchanger thermal energy storage unit with micro-channels

This article studies optimal conditions to maximize heat transfer efficiency within a triplex tube heat exchanger (TTHX) filled with phase-change material. In this context, micro-channels (MCs) incorporated into TTHX for the first time for acceleration melting time. A two-dimensional numerical model has been developed, and pure conduction and natural convection are both simulated. The Reynolds numbers range from 1 to 100. The types of temporal velocity profiles into micro-channels were uniform, step, elliptic, sinusoidal, and power. The effect of gravity states, namely no gravity, with gravity, and (MCHE), has been studied with different numbers of microchannels (4, 6, 8, 10, 12, and 14). The results showed that there was no variation in melting duration observed when increasing the Re number from 50 to 100. Thus, the maximum reduction in melting period occurred at Re = 50. Moreover, sinusoidal velocity profiles were more effective and could help the process finish sooner. In addition, micro channel tube exchanger (MCTE) fitted or equipped with 10 micro-channels has an optimum condition considering pressure drop and complete melting time. Using the sinusoidal profile reduced the total fusion time by 325 s compared to uniform flow (8.47 % reduction). This indicates that the sinusoidal profile is an effective way to reduce the melting period.

Numerical Investigation of phase transition in different latent heat storage systems in the presence of natural convection and porous media

Securing a reliable supply of energy is critical given the ever-increasing demand for energy and the challenges posed by a growing population. Latent energy storage is being introduced as one of the most efficient solutions to harness renewable and waste energy and ensure a constant supply. The phase change material (PCM) in this type of energy storage suffers from low responsiveness, which slows down the industrialization of latent storage. This study succinctly identifies the influencing factors that affect the efficiency of PCM-based latent energy storage, including fluid temperature, the role of natural convection and the benefits of porous media. It also provides new insights through comprehensive configuration analysis, ultimately contributing to the understanding of the field and addressing sustainable energy demands. For the numerical computations, enthalpy-porosity methodology via ANSYS Fluent 18.2 is employed a rigid grid for precise dual-phase simulation. The working fluid temperature is of similar importance for three types of units, as an improvement of 22% has been obtained by increasing the inlet temperature by 5 degrees, while the pipe model has benefited from an improvement of 26% under the same condition. The Triplex Tube Heat Exchanger (TTHX) outperforms the other units in all scenarios, as the heat transfer surface of this type is greater than that of its counterparts. Natural convection phenomenon is most effective in the pipe model, as its absence slows the melting rate by 236%. The inclusion of porous media produced on average 93% faster systems due to the additional heat transfer surface, although it suppressed the gravitational movement.

Effect of ternary hybrid nanoparticles (GO-MgO-TiO2) and radiative heat transfer on the solidification process of PCM inside a triplex tube with hollow fins

Nowadays, due to the features such as high latent heat and constant phase transition temperature, the utilization of phase change materials (PCMs) in energy storage and thermal management systems has attracted scholars' attention. However, the low thermal conductivity and solidification process of these materials has always been a challenge for widespread implementation of them in disparate industries. The current research investigates the characteristics of the PCM solidification process within a triplex tube Latent Heat Thermal Energy Storage System (LHTESS) with innovative hollow fins in the presence of ternary hybrid nanoparticles (THNPs) and radiative heat transfer. The governing equations are solved using Galerkin Finite Element Method (GFEM) with various boundary conditions in the outer wall, such as constant temperature, adiabatic, and coolant fluid temperature (triplex), through FlexPDE software. Furthermore, the effect of key parameters, including shape factor and volume fraction of THNPs, and radiative heat transfer on thermal storage performance is scrutinized. Ultimately, the Taguchi method is adopted to determine the optimal point at which the full solidification time (FST) is lowest. Results show that at 400000 s, the triplex case improved total discharging energy by 23% and 4% in comparison to the constant temperature and the adiabatic case, respectively. Additionally, by including THNPs with a volume percentage of 0.1 and a shape factor of 16.1 instead of 3, the required time for FTS reduces by approximately 13.1% and 21.9%, respectively. Also, the overall solidification times of the PCMs decrease to 36% by enhancing the radiation parameter from 0 to 1. These outcomes illustrate THNPs and considered fins are effective for reducing the FST and the shape factor of THNPs and radiation are key parameters that should be considered by designers.

Simulation of melting paraffin with graphene nanoparticles within a solar thermal energy storage system

In this paper, applying new structure and loading Graphene nanoparticles have been considered as promising techniques for enhancing thermal storage systems. The layers within the paraffin zone were made from aluminum and the melting temperature of paraffin is 319.55 K. The paraffin zone located in the middle section of the triplex tube and uniform hot temperatures (335 K) for both walls of annulus have been applied. Three geometries for the container were applied with changing the angle of fins (α = 7.5°, 15° and 30°). The uniform concentration of additives was assumed involving a homogeneous model for predicting properties. Results indicate that loading Graphene nanoparticles causes time of melting to decrease about 4.98% when α = 7.5° and the impact of ϕ improves about 5.2% with reduce of angle from 30° to 7.5°. In addition, as angle declines, the period of melting decreases around 76.47% which is associated with augmentation of driving force (conduction) in geometry with lower α.

Magnetocalorically accelerated charging of latent thermal energy storage systems

In the present research, the phase change behavior of a latent thermal energy storage system in the presence of a uniform magnetic field (MF) is numerically studied via a detailed three-dimensional simulation of the melting process. The thermal energy storage unit consists of a triplex tube heat exchanger (TTHX) filled with a phase change material (PCM) in its middle annulus surrounded by the streams of heat transfer fluid (HTF) in the middle tube and the outer annulus. The exclusive exertion of the MF on the PCM or the HTF zone is shown to have a positive influence on the thermal response. This is due to the formation of excessive vortical flow in the melted PCM zone in the first case or the formation of swirling flow in the HTF zone in the second case. Exerting the MF on all zones results in a profound acceleration of the charging process due to the synergy between the two mentioned heat transfer (HT) enhancement mechanisms. Compared to the base case without nanoparticles, the total melting time of the PCM is reduced by 30%, 27%, and 57% when the MF is imposed on the PCM zone, the HTF zones, and all zones, respectively.