Numerical Investigation on the Thermal Performance Enhancement in a Latent Heat Thermal Storage Unit

2012 ◽  
Author(s):  
Adriano Sciacovelli ◽  
Vittorio Verda ◽  
Francesco Colella
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Volume Fraction ◽  
Nano Particles ◽  
Symmetric Model ◽  
Tube Heat Exchanger ◽  
Charging Time ◽  
Standard Design

The present paper describes the application of computational fluid-dynamics (CFD) for the analysis of the melting process in a single vertical shell-and-tube heat exchanger. The computations are based on a 2D axial-symmetric model that takes in account the phase change phenomenon by means of the enthalpy method. The numerical studies aimed at clarifying the importance of the different heat transfer mechanisms with a particular focus on natural convection demonstrating its fundamental importance on the phase change process by enhancing the heat transfer between HTF and solid PCM. the paper discusses the effect of two different common performance enhancement techniques: dispersion of high conductive nano-particles in the PCM and the introduction of radial fins. An extensive thermo-fluid dynamic study has been undertaken exploring the effect on the thermal performance enhancement of particle volume fraction and fins. The analysis shows that in comparison to the standard design, the performances of the LHTS unit in terms of charging time could be improved by up to 40 % for nano-particle enhancement. When fins are considered charging time can be reduced to one-third of its original value. Significant improvements are also achieved during the solidification process: discharge time is reduced of 33% with fins enhancement.

scholarly journals Thermal Charging Optimization of a Wavy-Shaped Nano-Enhanced Thermal Storage Unit

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1496
Author(s):  
Mohammad Ghalambaz ◽  
S.A.M. Mehryan ◽  
Ahmad Hajjar ◽  
Mohammad Yacoub Al Shdaifat ◽  
Obai Younis ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Phase Change ◽  
Volume Fraction ◽  
Thermal Storage ◽  
Wave Number ◽  
Storage Unit ◽  
Charging Time ◽  
Phase Change Heat Transfer ◽  
The Impact

A wavy shape was used to enhance the thermal heat transfer in a shell-tube latent heat thermal energy storage (LHTES) unit. The thermal storage unit was filled with CuO–coconut oil nano-enhanced phase change material (NePCM). The enthalpy-porosity approach was employed to model the phase change heat transfer in the presence of natural convection effects in the molten NePCM. The finite element method was applied to integrate the governing equations for fluid motion and phase change heat transfer. The impact of wave amplitude and wave number of the heated tube, as well as the volume concertation of nanoparticles on the full-charging time of the LHTES unit, was addressed. The Taguchi optimization method was used to find an optimum design of the LHTES unit. The results showed that an increase in the volume fraction of nanoparticles reduces the charging time. Moreover, the waviness of the tube resists the natural convection flow circulation in the phase change domain and could increase the charging time.

scholarly journals The Thermal Charging Performance of Finned Conical Thermal Storage System Filled with Nano-Enhanced Phase Change Material

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1605
Author(s):  
Mohammad Ghalambaz ◽  
Hassan Shirivand ◽  
Kasra Ayoubi Ayoubloo ◽  
S.A.M. Mehryan ◽  
Obai Younis ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Phase Change ◽  
Inclination Angle ◽  
Conical Shell ◽  
Volume Fraction ◽  
Small Radius ◽  
Design Parameters ◽  
Small Aspect Ratio ◽  
Charging Time

A latent heat thermal energy storage (LHTES) unit can store a notable amount of heat in a compact volume. However, the charging time could be tediously long due to weak heat transfer. Thus, an improvement of heat transfer and a reduction in charging time is an essential task. The present research aims to improve the thermal charging of a conical shell-tube LHTES unit by optimizing the shell-shape and fin-inclination angle in the presence of nanoadditives. The governing equations for the natural convection heat transfer and phase change heat transfer are written as partial differential equations. The finite element method is applied to solve the equations numerically. The Taguchi optimization approach is then invoked to optimize the fin-inclination angle, shell aspect ratio, and the type and volume fraction of nanoparticles. The results showed that the shell-aspect ratio and fin inclination angle are the most important design parameters influencing the charging time. The charging time could be changed by 40% by variation of design parameters. Interestingly a conical shell with a small radius at the bottom and a large radius at the top (small aspect ratio) is the best shell design. However, a too-small aspect ratio could entrap the liquid-PCM between fins and increase the charging time. An optimum volume fraction of 4% is found for nanoparticle concentration.

scholarly journals Numerical Study of Shell and Tube Heat Exchanger Performance Enhancement Using Nanofluids and Baffling Technique

2021 ◽  
Vol 80 (2) ◽  
pp. 42-55
Author(s):  
Lahcene Bellahcene ◽  
Djamel Sahel ◽  
Aissa Yousfi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Performance Enhancement ◽  
Volume Fraction ◽  
Numerical Study ◽  
Fluid Flows ◽  
Physical Parameters ◽  
Minimum Entropy ◽  
Tube Heat Exchanger ◽  
Maximum Improvement

The aim of this work is to investigate the forced convective heat transfer phenomena and fluid flows of water-based Al2O3 nanofluids in the baffled shell and tubes heat exchanger (STHE). Water as a hot fluid flows in the side of the tubes, and Al2O3 nanofluids as cooling fluid flow in the shell side. Numerical investigations have been carried out based on the continuity, momentum, and energy equations which are solved by using the finite element method with the help of the COMSOL 5.4 CFD software. The obtained results were presented by average Nusselt number, streamlines, isotherms, and various physical parameters which are a volumetric fraction of nanoparticles (1%? Cv ?3%). The results are found that the heat transfer increases with the rise of inlet velocity and volume fraction. In addition, the presence of baffles inside tubular heat exchangers can create a better mixture of fluids which is augmenting heat transfer execution. The choice of these parameters is important to get the maximum improvement of heat transfer with minimum entropy consumption.

scholarly journals Augmented thermal performance in a non-uniform heat flux circular tube with twisted tape insert using hybrid nanofluid

2021 ◽  
Vol 321 ◽  
pp. 04009
Author(s):  
Arvind Kumar ◽  
Kunal Dey ◽  
Suvanjan Bhattacharyya ◽  
Akshoy Ranjan Paul ◽  
Ali Cemal Benim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Circular Tube ◽  
Nano Particles ◽  
Hybrid Nanofluid ◽  
Twisted Tape ◽  
Uniform Heat

The influence of non-uniform heat transfer on a circular tube with a twisted tape insert using nanofluid (NF) is examined. The circular tube had an inner diameter 20 mm, with 0.5 mm thickness and 2 m of length. Wall heat flux conditions were examined for Reynolds number ranging from 5 000 to 25 000. Heat flux distribution included partial heating at different circumferential positions. Water was used as a base fluid, while single and multi-nano particles are used for simple and hybrid nanofluids (HNF). The goal of this study is to augment the thermal performance by incorporating non-uniform heating, using a twisted tape insert and by using nanoparticle of different volume fraction. NF act as a fluid additive and twisted tape act as a turbulence promoter and they enhance the heat transfer rate. However, major disadvantage in this investigation is the pressure drop incurred due to the twisted tape and NFs. Hence, a series of simulation are carried out to find out the optimum configuration of the set-up for which heat transfer will be enhanced with minimum pressure drop.

Modeling of Newtonian and non-Newtonian-based coolants for deployment in industrial length-scale shell and tube heat exchanger

2021 ◽  
pp. 2150085
Author(s):  
S. Anitha ◽  
Tiju Thomas ◽  
V. Parthiban ◽  
M. Pichumani
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Numerical Procedure ◽  
Point Of View ◽  
Hybrid Nanofluid ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Hybrid Nanofluids

To evaluate the heat transfer performance (HTP) of hybrid nanofluids, numerical simulations are carried out in an industrial length single pass shell and tube heat exchanger. In shell, ISO VG 68 oil enters with [Formula: see text]C and with [Formula: see text]C, the coolant passes into the tube. CNT-[Formula: see text]/water and CNT-[Formula: see text]/sodium alginate (SA) are used as Newtonian and non-Newtonian hybrid nanofluid, respectively. The influence of base fluid and nanoparticles on thermal performance of heat exchanger is studied. The chosen nanoparticles are reliable to the industrial deployment. The current numerical procedure is validated with the earlier experimental results. Volume fraction of nanoparticles is optimized for an effective HTP of the heat exchanger. About 60% increment in heat transfer coefficient is observed when hybrid nanofluid is employed. By using Newtonian hybrid nanofluid, 50% improvement in Nusselt number is marked out. Effectiveness and heat transfer rate of heat exchanger are higher with the employment of Newtonian hybrid nanofluid. Results indicated that, even though Newtonian hybrid nanofluid shows higher thermal performance, non-Newtonian hybrid nanofluid is preferable for energy consumption point of view.

scholarly journals Latent Heat Thermal Storage in Non-Uniform Metal Foam Filled with Nano-Enhanced Phase Change Material

2021 ◽  
Vol 13 (4) ◽  
pp. 2401
Author(s):  
Mohammad Ghalambaz ◽  
S. A. M. Mehryan ◽  
Ahmad Hajjar ◽  
Mehdi A. Fteiti ◽  
Obai Younis ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Phase Change ◽  
Pore Size ◽  
Metal Foam ◽  
Volume Fraction ◽  
Heated Surface ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Charging Time

The melting heat transfer of CuO—coconut oil embedded in a non-uniform copper metal foam—was addressed. Copper foam is placed in a channel-shaped Thermal Energy Storage (TES) unit heated from one side. The foam is non-uniform with a linear porosity gradient in a direction perpendicular to the heated surface. The finite element method was applied to simulate natural convection flow and phase change heat transfer in the TES unit. The results showed that the porosity gradient could significantly boost the melting rate and stored energy rate in the TES unit. The best non-uniform porosity corresponds to a case in which the maximum porosity is next to a heated surface. The variation of the unit placement’s inclination angle is only important in the final stage of charging, where there is a dominant natural convection flow. The variation of porous pore size induces minimal impact on the phase change rate, except in the case of a large pore size of 30 pore density (PPI). The presence of nanoparticles could increase or decrease the charging time. However, using a 4% volume fraction of nanoparticles could mainly reduce the charging time.

Figure of Merit-Based Optimization Approach of Phase Change Material-based Composites for Portable Electronics Using Simplified Model

2021 ◽  
Author(s):  
Ayushman Singh ◽  
Srikanth Rangarajan ◽  
Leila Choobineh ◽  
Bahgat Sammakia
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Figure Of Merit ◽  
Volume Fraction ◽  
Simplified Model ◽  
Transient Temperature ◽  
Change Material

Abstract This work presents an approach to optimally designing a composite with thermal conductivity enhancers (TCEs) infiltrated with phase change material (PCM) based on figure of merit (FOM) for thermal management of portable electronic devices. The FOM defines the balance between effective thermal conductivity and energy storage capacity. In present study, TCEs are in the form of a honeycomb structure. TCEs are often used in conjunction with PCM to enhance the conductivity of the composite medium. Under constrained composite volume, the higher volume fraction of TCEs improves the effective thermal conductivity of the composite, while it reduces the amount of latent heat storage simultaneously. The present work arrives at the optimal design of composite for electronic cooling by maximizing the FOM to resolve the stated trade-off. In this study, the total volume of the composite and the interfacial heat transfer area between the PCM and TCE are constrained for all design points. A benchmarked two-dimensional direct CFD model was employed to investigate the thermal performance of the PCM and TCE composite. Furthermore, assuming conduction-dominated heat transfer in the composite, a simplified effective numerical model that solves the single energy equation with the effective properties of the PCM and TCE has been developed. The effective thermal conductivity of the composite is obtained by minimizing the error between the transient temperature gradient of direct and simplified model by iteratively varying the effective thermal conductivity. The FOM is maximized to find the optimal volume fraction for the present design.

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