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Thermal energy storage using the latent heat of phase change materials (PCMs) is a promising technique to solve the time mismatch between the availability and usage of flue gas heat in distributed generation systems (DGSs). A diesel-engine-powered DGS integrated with two-stage tube-type PCM modules for exhaust gas heat recovery was developed and st...
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The APR1400 Nuclear Heat Storage and Recovery (NHS&R) System described here represents the conceptual design and interface of a tertiary cycle with the secondary system of the Korean nuclear reactor plant APR1400. The system is intended to reliably and efficiently store and recover thermal energy from a Nuclear Power Plant (NPP) steam system in ord...
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... The LHTES systems using phase change materials (PCMs) have been applied in several engineering applications such as concentrating solar plants, thermal isolation, groundwater infiltration, solar energy, building sectors, nuclear reactors, and so on thanks to the phase transition process [1,2]. However, the only issue of these systems is the low thermal conductivity of PCM. ...
In this investigation, a comprehensive numerical analysis of the flow involved in an open-ended straight channel fully filled with a porous metal foam saturated and a phase change material (paraffin) has been performed using a single relaxation time lattice Boltzmann method (SRT-LBM) at the representative elementary volume (REV) scale. The enthalpy-based approach with three density functions has been employed to cope with the governing equations under the local thermal non-equilibrium (LTNE) condition. The in-house code has been validated through a comparison with a previous case in literature. The pore per inch density (10≤PPI≤60) and porosity (0.7≤ε≤0.9) effects of the metal structure were analyzed during melting/solidifying phenomena at two Reynolds numbers (Re = 200 and 400). The relevant findings are discussed for the LTNE intensity and the entropy generation rate (Ns). Through the simulations, the LTNE hypothesis turned out to be secure and valid. In addition, it is maximum for small PPI value (=10) whatever the parameters deemed. On the other hand, high porosity (=0.9) is advised to reduce the system’s irreversibility. However, at a moderate Re (=200), a small PPI (=10) would be appropriate to mitigate the system irreversibility during the charging case, while a large value (PPI = 60) might be advised for the discharging case. In this context, it can be stated that during the melting period, low porosity (=0.7) with low PPI (=10) improves thermal performance, reduces the system irreversibility and speeds up the melting rate, while for high porosity (=0.9), a moderate PPI (=30) should be used during the melting process to achieve an optimal system.
... Li et al. [127] conducted energy and exergy analysis for exhaust gas heat recovery system of a diesel engine-powered generator integrated with cascaded two stages PCM modules (see Fig. 33). The experiments were conducted during charging and discharging stages. ...
... Demonstration system of diesel engine with cascaded PCM modules[127].A.A.M. Omara ...
... Li et al.[88] Theoretical study Diesel engine• NaOH.H 2 O Exhaust system 2 • C •The PCM increased the warming-up time by 40%. Li et al.[127] The two-stage storage system stored input energy and exergy of flue gas by 56.4% and 48.3%, respectively.• ...
Since most of the energy consumed by an internal combustion engine (ICE) is wasted, heat recovery from the exhaust and coolant is considered as a promising technology for improving the engine efficiency. The systems that used for recovering wasted thermal energy are called waste heat recovery (WHR) systems. However, most WHR methods suffer from main drawbacks such as difficult implementation, low thermal controllability and poor thermal storability. These drawbacks could be overcome by integrating thermal energy storage (TES) systems with ICEs. TES relies on sensible heat, latent heat and thermochemical storage. Latent heat storage method with phase change materials (PCMs) is the most utilized in ICEs because of its good controllability and high storage capacity. Therefore, this review presents the applications of TES with PCMs for recovering waste energy in ICEs. The literature shows that PCMs could be incorporated into different ICEs systems including exhaust recovery systems, cooling recovery systems, catalytic converters, diesel generators, evaporator and pressure regulators, additional diesel heaters, and cylinder's body. The previous studies on these systems show the potential of TES with PCMs in storing and recovering waste heat. Moreover, it is shown that the recovered heat by PCMs is mainly used for purposes of engine pre-heating during cold-start, maintaining hot temperature of catalysts for better conversion efficiency, and heating domestic and industrial water. Finally, the problems of PCMs with ICEs such as bulky system problem, high initial cost, corrosion issues, and poor stability; are also discussed in this review.
... Thermal Energy Storage (TES) has been recognised as a low-cost remedy for applications that require thermal energy (e.g., heating buildings, washing/sterilisation, manufacturing processes), in which heat is directly used as opposed to other types of energy storage such as batteries. Among TES options, systems that utilise the high latent heat of phase change by employing phase change materials (PCMs), are characterised by high-energy storage density [4] and suitability to a diverse working temperature range [5,6]. In fact, phase change materials (PCMs) are available for target working temperatures from as low as − 100 • C to as high as 900 • C [7][8][9][10][11]. ...
... As a trade-off to these advantages, most PCMs suffer from low thermal conductivity, which makes it hard to charge and discharge effectively [5,12]. To overcome this issue, several methods have been proposed in the literature, including using nano-additives [13,14], metal foams [15,16], solid fins [17], heat pipes [18], metallic meshes [19][20][21]. ...
... − ε i ρ PCM L sf ∂η ∂t (5) Energy equation for the solid copper walls: ...
Due to the intermittent/volatile nature of renewable energy resources, they may periodically fail to provide enough energy to complete the charging/discharging processes of Latent Heat Thermal Energy Storage (LHTES) systems. However, only a limited understanding is available for the implications of partial charging/discharging. To address this knowledge gap, the present study numerically analysed the performance of a circular LHTES under partial charging/discharging modes. Three sheets of aluminium foam (all spaced equally at 120°) were added to enhance the thermal response of the storage. Sixteen different storage configurations were studied and revealed that the angle of the right-most metal foam sheet (θ) and their thickness (wmf) considerably affect the charging/discharging process. According to the proposed capacity-based and time-based charging/discharging powers, it was found that the configuration with maximum complete charging power (case no.7, θ = π/6 and wmf = 7 mm) does not necessarily exhibit the best performance during partial charging mode. Instead, case no.7 has up to 6% lower charging power than the other cases when partially charged. Finally, it was revealed that a Y-shaped design can achieve optimal performance if it is charged in the upright orientation, but rotated 60° (i.e., to a ⅄-shaped orientation) to maximise the discharging process.
... Phase change material (PCM) can resolve this issue and can supply heat energy at a constant rate for different thermal applications. Work reported on PCM heat storage by various authors is listed in table 1. 1D and 2D enthalpy Analytical [2] 2D fixed-grid enthalpy Finite volume approach [3] 2D fixed-grid enthalpy Gauss-Seidel iteration [4] -Experimental [5] Review - [6] -Experimental [7] There are many PCM available for thermal applications but among all the PCM, NaOH is mediumtemperature range PCM having cost-effective, and good heat storage capacity. Therefore, NaOH is choosen as area of the present work. ...
... For modelling, a three-dimensional heat transfer 3-D enthalpy based model has been used. Many authors have used enthalpy based model in 1D or 2D [1][2][3][4]. In this work, we have used 3D enthalpy model in which all three dimensions are considered for simulation. ...
There is a mismatch between energy demand by consumers and supply from the sun. Therefore, we store Solar Energy in the phase change material (PCM) for storage energy. We used medium temperature range salt, Sodium hydroxide (NaOH), melting temperature at 591 K and heat of fusion 160 kJ/kg. We did the numerical simulation using COMSOL Multiphysics®, we kept radially variable surface flux at the bottom of the container. Linearly variable flux at the centre is 78 kW/m ² and 18 kW/m ² at the periphery. For numerical analysis, we used 3D enthalpy based model. We found that the bulk temperature of NaOH reaches about 800 K after 6 hours and total energy stored by the PCM is about 21 MJ. This amount of energy is very useful for domestic and small industrial process.
... In many industrial processes maintaining a constant temperature is crucial for operations, in particular, to ones with stringent temperature requirements. With the interest in reducing emissions, the inclusion of renewable heat sources or recovered process heat has garnered considerable interest [1]. Under these conditions, however, fluctuations in supply temperature are to be expected, for example, when using solar collectors supply temperature will vary with solar irradiation or when recovering heat from an intermittent process [2]. ...
In many heat transfer related applications, there is a need for a stable, constant supply temperature. As a result, the integration of intermittent renewable sources of heat into these processes can prove to be challenging, requiring special temperature smoothing devices or strategies. This study focuses on the application of phase change materials integrated into a double tube heat exchanger as a possible thermal smoothing device. The objective of this study is to evaluate the ability of the exchanger to smoothen out temperature variations within the cold stream outlet while the hot stream is subject to oscillating inlet conditions. A computational fluid dynamics approach is used where a numerical model is developed, validated and then used to model the conjugate heat transfer within the heat exchanger. Four organic phase change materials (PCM) with different phase change temperatures were selected for investigation (myristic, octadecane, eicosane, and wax) to study the relationship between melting temperature and stabilization performance. A parametric study was then conducted by varying the Reynolds number of the flow as well as temperature oscillation period and amplitude to study the sensitivity of the system. The results confirm the potential of a phase change material-based thermal capacitor at dampening oscillations across the heat exchanger.
... This allows removing temperature peaks due to the intermittent high power demand and storing a large amount of solar energy without significantly increasing the system temperature. Furthermore, LHTESS using phase change materials (PCMs) are widely used in various engineering applications such as building temperature regulation, waste heat recovery, compact heat exchangers, solar energy storage, concentrating solar plants, etc. [2,3]. However, their low thermal conductivity is one of their weaknesses because it restricts thermal transport by giving rise to slow heat dissipation during charging/discharging periods. ...
In this work, the two-dimensional laminar flow and the heat transfer in an open-ended rectangular porous channel (metal foam) including a phase change material (PCM; paraffin) under forced convection were numerically investigated. To gain further insight into the foam pore effect on charging/discharging processes, the Darcy–Brinkmann–Forchheimer (DBF) unsteady flow model and that with two temperature equations based on the local thermal non-equilibrium (LTNE) were solved at the representative elementary volume (REV) scale. The enthalpy-based thermal lattice Boltzmann method (TLBM) with triple distribution function (TDF) was employed at the REV scale to perform simulations for different porosities (0.7≤ε≤0.9) and pore per inch (PPI) density (10≤PPI≤60) at Reynolds numbers (Re) of 200 and 400. It turned out that increasing Re with high porosity and PPI (0.9 and 60) speeds up the melting process, while, at low PPI and porosity (10 and 0.7), the complete melting time increases. In addition, during the charging process, increasing the PPI with a small porosity (0.7) weakens the forced convection in the first two-thirds of the channel. However, the increase in PPI with large porosity and high Re number limits the forced convection while improving the heat transfer. To sum up, the study findings clearly evidence the foam pore effect on the phase change process under unsteady forced convection in a PCM-saturated porous channel under local thermal non-equilibrium (LTNE).
... This allows removing temperature peaks due to the intermittent high power demand and storing a large amount of solar energy without significantly increasing the system temperature. Furthermore, LHTESS using phase change materials (PCMs) are widely used in various engineering applications such as building temperature regulation, waste heat recovery, compact heat exchangers, solar energy storage, concentrating solar plants, etc. [2,3]. However, their low thermal conductivity is one of their weaknesses because it restricts thermal transport by giving rise to slow heat dissipation during charging/discharging periods. ...
In this work, the two-dimensional laminar flow and the heat transfer in an open-ended rectangular porous channel (metal foam) including a phase change material (PCM; paraffin) under forced convection were numerically investigated. To gain further insight into the foam pore effect on charging/discharging processes, the Darcy–Brinkmann–Forchheimer (DBF) unsteady flow model and that with two temperature equations based on the local thermal non-equilibrium (LTNE) were solved at the representative elementary volume (REV) scale. The enthalpy-based thermal lattice Boltzmann method (TLBM) with triple distribution function (TDF) was employed at the REV scale to perform simulations for different porosities (0.7 ≤ " ≤ 0.9) and pore per inch (PPI) density (10 ≤ PPI ≤ 60) at Reynolds numbers (Re) of 200 and 400. It turned out that increasing Re with high porosity and PPI (0.9 and 60) speeds up the melting process, while, at low PPI and porosity (10 and 0.7), the complete melting time increases. In addition, during the charging process, increasing the PPI with a small porosity (0.7) weakens the forced convection in the first two-thirds of the channel. However, the increase in PPI with large porosity and high Re number limits the forced convection while improving the heat transfer. To sum up, the study findings clearly evidence the foam pore effect
on the phase change process under unsteady forced convection in a PCM-saturated porous channel under local thermal non-equilibrium (LTNE).
... This makes the latent TES very promising for energy collection and reuse, which is beneficial to energy conservation and emission reduction. Consequently, it can be found in many industrial fields, like concentrating solar power plants, waste heat recovery, temperature regulation of buildings, compact heat exchangers, thermal management of electric devices, etc. [3][4][5]. However, the key disadvantage of PCM is its intrinsically low thermal conductivity, which limits the heat transfer rate during the charging and discharging cycles. ...
The energy transport inside a phase change material (PCM) based thermal energy storage system using metal foam as an enhancement technique is investigated numerically. The paraffin is used as the PCM and water as the heat transfer fluid (HTF). The transient heat transfer during the charging and discharging processes is solved, based on the volume averaged conservation equations. The flow in PCM/foam and HTF/foam composites is modelled by the Forchheimer-extended Darcy equation, while the two-temperature model is employed to account for the local thermal non-equilibrium effect between the foam matrix and fluid phase. The results show that the overall performance is greatly improved by inserting metal foam in both HTF and PCM sides. A nearly 84.9% decrease in the time needed for the total process is found compared with the case of pure PCM, and 40% compared with the case of metal foam insert only in the PCM side. Foam porosity and HTF inlet temperature greatly affect the dynamic heat storage/release process.
Developing phase change materials (PCMs) with excellent thermal properties and low cost is of great significance for accelerating the applications of the latent heat storage technology in waste heat recovery. In this work, a novel composite PCM based on sodium acetate trihydrate (SAT), expanded graphite (EG) and carbon nanotubes (CNTs) was prepared and optimized for efficient heat storage and release effect. To confirm the phase change effect of composite PCM was acted above 50 °C, urea was introduced to improve the melt uniformity of SAT and its proportion was optimized in the range of 0–10 wt% based on the DSC results. The nucleating promotion of disodium hydrogen phosphate dodecahydrate (DHPD) on the SAT-Urea mixture crystals was characterized by a metallographic microscope. EG was used as the porous carrier to eliminate the liquid mobility of melted PCM. CNTs were introduced to further enhance the thermal conductivity of the composite PCM. It is shown that 4 wt% urea can effectively inhibit the phase segregation of SAT and keep the phase change temperature of mixture above 55 °C. The melting enthalpy of SAT-Urea mixture is as high as 250.5 kJ/kg. It is observed from the microscope images that 4 wt% DHPD can promote the rapid formation of small crystals of SAT-Urea mixture, thereby providing more nuclei and accelerating the crystal growth rate. And the supercooling degree can be reduced to 0.6 °C. The porous network provided by EG and the addition of CNTs can significantly enhance the thermal conductivity of SAT-Urea mixture. As a result, the SAT-Urea/EG/CNTs composite PCM exhibits a high enthalpy of 180.1 kJ/kg, a high thermal conductivity of 6.904 W/(m·K), and excellent thermal reliability after 300 cycles of melt-solidification experiments.
