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Employing phase change materials (PCMs) for latent heat storage (LHS) application has a great potential to improve a solar thermal system performance. Despite this fact, the use of PCM in this area is quite limited due to the poor thermal conductivity of available PCMs. Therefore, heat transfer enhancement is one of the essential strategies that ca...
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... a fully detailed drawing was completed based on the proposed design, the manufacturing process took place. As shown in Fig. 3, after folding and welding the mild steel sheet, eight holes were drilled at the bottom of the container. The spiral-wired tubes were laid off in the container and the bottom ends of the spiral-wired tubes were soldered to the container body. A thermistor was placed inside the tank close to the middle to measure the internal ...
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Solar energy occupies one of the most important types of renewable energy sources . It is the energy provide by the sun .Solar radiation data are fundamental inputs for solar energy applications , such as photovoltaic , and solar thermal systems . The design of a solar energy conversion system requires knowledge regarding the availability of global...
In this study, basalt stone availability as storage material in the sensible heat storage method and the effect of heat transfer fluid flow rate were investigated. The experiments were carried out at three different flow rates, and measurements were taken at intervals of ten minutes for three days for each flow rate. Analytical results also show th...
Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual...
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... On this basis, the enthalpy-porosity model is used to mathematically describe the PCM before and after the phase change and the melting and solidification process [15,16]. The model uses the porosity ε to represent the phase change state, which is solid at ε = 0, liquid at ε = 1, and molten at 0 < ε < 1, where the phase change material is considered as a porous media material. ...
The implementation of heat sinks in high-power pulse electronic devices within hypersonic aircraft cabins has been facilitated by the emergence of innovative phase change materials (PCMs) characterized by excellent thermal conductivity and high latent heat. In this study, a representative material, layered porous media filled with paraffin wax, was utilized, and a three-dimensional numerical model based on the enthalpy-porosity approach was employed. A thermal response research was conducted on the Phase Change Heat Exchange Unit with Layered Porous Media (PCHEU-LPM) with different cooling methods. The results indicate that water cooling proved to be suitable for the PCHEU-LPM with a heat flux of 50,000 W/m2. Additionally, parametric studies were performed to determine the optimal cooling conditions, considering the inlet temperature and velocity of the cooling flow. The results revealed that the most suitable conditions were strongly influenced by the coolant inlet parameters, along with the position of the PCM interface. Finally, the identification of the parameter combination that minimizes temperature fluctuations was achieved through the Response Surface Analysis method (RSA). Subsequent verification through simulation further reinforced the reliability of the proposed optimal parameters.
... Further, the melting process using multiple PCMs with a fully turbulent flow was performed for the optimal length of each PCM in the horizontal direction [14]. The impact of HTF mass flow rate and temperature was extensively investigated for the phase change process [10][11][12]15,16]. Most studies were conducted on TES for the pipe model, and the cylindrical model has not been well explored. ...
Phase change material (PCM) based thermal energy storage (TES) offers high energy density and better heat transfer performance by encapsulating PCM within a specifically designed container, i.e., shell and tube type TES. In this work, the PCM is packed in multiple cylindrical tubes, and heat transfer fluid (HTF) flows in the annulus. Such arrangement of PCM and HTF in the TES system is termed a cylindrical model, and the one opposite to the cylindrical model is called a pipe model. This work conducts the performance evaluation for PCM-based shell and tube TES using an experimentally validated numerical model. The 3D cyclic periodic model for TES has been developed based on hexagonal circle packing, and the effective energy storage ratio as a performance index under varying geometrical and operating parameters has been investigated. The variation in parameters includes tube length (0.5–7 m), diameter (10–50 mm), initial temperature (293.15–303.15 K), volumetric flow rate (10–500 l/min), inlet temperature (323.15–393.15 K). Using a conjugate heat transfer model, the influence of parameters was investigated, and the performance index was evaluated using the effectiveness-NTU theory. It was found that TES was effective for geometrical parameters diameter d ≤ 30 mm and length L ≥ 2 m. The performance index of 1.54 was optimum and achieved when the inlet temperature was 333.15 K. This optimum performance index value was compared with existing work and found to be performing comparatively well.
... C mush is a mushy zone morphology constant that defines a decrease of velocity towards zero as PCM solidifies, i.e., the higher value results in a sharper velocity decrease to zero. Conventionally, the C mush constant is between 10 4 to 10 7 kg m − 3 s − 1 , [35]. Thus, it was found that the upper value of 10 7 kg m − 3 s − 1 well describes the lard phase transition. ...
... Similarly, Youssef et al. [25] explored the potential of PCMs for latent heat storage (LHS) to enhance the performance of solar thermal systems. They investigated the use of various nano-additives to improve the thermophysical properties of pure PCMs. ...
In this study, an investigation was conducted on four distinct configurations, designated as Case-1, Case-2, Case-3, and Case-4, focusing on parametric analysis. Each configuration features a cylindrical enclosure containing pure Gallium, a phase change material (PCM). The solid-to-liquid phase transition of the encapsulated material was examined using a 2D CFD methodology. Additionally, the effect of applying three temperatures, $T_1 = 32°C$, $T_2 = 39°C$, and $T_3 = 42°C$, along the generator of the enclosure, with or without fins, was also studied. To accurately model the melting process of the PCM, the Enthalpy- Porosity Method was employed, and meticulous detailing of underlying assumptions was under- taken to ensure precise representation. The validation process involved comparing outcomes of the physical solidification/melting model with reference data from a state-of-the-art study. The specific cases comprised Case-1 - a slender finless cylinder; Case-2 - a thin finned cylinder ($l = 10mm$, $t = 0.6mm$); Case-3 - featuring larger fins ($l = 20mm$, $t = 0.6mm$); and Case-4 - incorporating the largest fins ($l = 30mm$, $t = 0.6mm$). Strategically incorporating thin fins accelerates Gallium melting significantly, reducing times by up to 89\%. This enhancement is driven by a 96\% increase in the heat transfer coefficient (h), leading to faster melting rates. In addition, fins boost the Nusselt number (Nu) by 91\%, indicating improved convective heat transfer and enhanced melting. Melting rates increase by around 30\%, notably in Case-3. Temperature $T_1$ shifts dominant heat transfer from convection to conduction, as seen in 2D CFD contours with stratified patterns in Case-3 at $t = 240s$ and Case-4 at $t = 240s$ and $t = 300s$. A localized cold spot at t = 300s in Case-4 signals localized heat transfer effects.
... It has been observed that the use of PCM in the underfloor heating system can reduce the electricity consumption between 42% and 67%, thus reducing the heating load by approximately 40% and variable costs by 20%. A PCM heat exchanger (HX) was integrated into a specially designed and indirect solar assisted heat pump test system with spiral cable pipes and investigated by Youssef et al. [4] was performed the effects of different inlet heat transfer rates and temperatures on PCM melting/solidification time are demonstrated. Plytaria et al. [5] studied three different solar-assisted heat pump as underfloor heating systems, with and without PCM. ...
... Their study revealed that an increase in the HTF inlet temperature and mass flow rate reduced the time required to complete the phase change of paraffin wax. Among the different heat transfer enhancement techniques, adding fins has proved to be the most feasible solution, due to their ease of manufacturing and low cost, together with their high efficiency [40]. Different types of fins have been studied extensively, including such geometrical solutions as radial fins [41][42][43][44] and longitudinal ones [33,[45][46][47][48]. Agyenim et al. [49] conducted an experimental study to compare heat transfer enhancement using circular or longitudinal fins with a control system without fins. ...
... where, A mush is the mushy zone constant used to measure the damping amplitude (1 × 10 5 ) [55,56], and its value is associated with the shape and fine structure of the paste region; δ is a small arbitrary constant value to avoid division by zero (1 × 10 − 3 ) [57,58]; u → p is the traction speed away from the mushy zone; h ref is the reference enthalpy; L a is the latent heat; f l is the liquid fraction; T sol and T liq represent solidus temperature and liquidus temperature of PCMs, respectively. The difference in the solidus and liquidus temperatures defines the transition from solid to liquid phases during the melting of PCMs [59]. ...
Packed-bed thermal energy storage (PBTES) systems utilizing phase change capsules have found extensive applications in thermal energy harvesting and management to alleviate energy supply-demand imbalances. Nevertheless, the sluggish thermal charging rate of phase change materials (PCMs) capsules remains a significant impediment to the rapid advancement of PBTES. Here, bionic PCMs capsules are proposed by mimicking the internal and external structure of chloroplast-granum. The heat transfer and flow characteristics of the bionic PCMs capsules in the packed-bed are analyzed by experiments and numerical simulations. The results illustrate that the chloroplast-fin type PCMs capsule exhibits significantly faster heat storage compared to the sphere type PCMs capsule. This improvement is attributed to the bionic folded shape and inner membrane structure, which generate multiple local vortices to enhance heat convection, and shorten the heat transfer distance between the capsule wall and center PCMs to facilitate heat conduction. The PCMs capsules are further filled into the packed-bed in a staggered arrangement, resulting in increased heat transfer area and enhanced disturbance flow as compared to an aligned arrangement. Consequently, the melting time of the packed-bed filled with chloroplast-fin type capsules is reduced by 33.2%, meanwhile the average exergy storage rate and exergy efficiency are enhanced by 48.4% and 8.3%, respectively, compared to the packed-bed filled with sphere type capsules. This research offers a novel approach for designing high-performance PBTES system utilizing bionic capsules.
... Rostami et al. [9] studied the use of nanoparticles to increase thermal conductivity in PCMs but the effects on living organisms are not fully understood [10,11]. Youssef et al. [12] suggested a heat exchanger with spiral-wired tubes arranged vertically to enhance natural convection in the container. Although the study showed an even buildup of liquid/solid phase during the melting/ solidification process, it did not analyze velocity distribution along the tubes. ...
Thermal energy storage in mobile applications, particularly battery of electric vehicles, is currently gaining a lot of importance. In this paper, a semi-theoretical time-dependent mathematical model of the phase change in a double shell thermal energy storage module has been developed where the inner tube is a heat exchange surface. An effective front region thickness for the melting and solidification process has been studied. The proposed model is calibrated based on our experimental data. The purpose of such a model is to enable the optimization of the geometry of the energy storage modules in terms of the PCM to the TES container mass ratio and enhancement of phase change rate. In addition, results obtained for a single tube can be used in the bundle of tubes in shell and tube TES design. The results have shown that for the larger diameter of the module (smaller difference between the working tube and shell diameter) the optimal working time is around 2000 s.
... It is noted from the literature reviewed that the improvement of heat transfer in the PCM is done in several ways, including fins with different designs. But W. Youssef et al (2018) explained that the PCM movement during the phase change is somewhat restricted by the presence of fins, which negatively affects the heat transfer in the PCM. So, they proposed an indirect solar assistant heat pump system consisting of a design that has not been used before to improve heat transfer in the PCM called a spiral-wired tube. ...
... Thermal performance characteristics of PCM based storage unit are defined in a different way, e.g.: time of charging/discharging, rate of these processes, power per unit mass of PCM during discharging, also detailed characteristic of melting process [5,6,10,11,12]. Specific research goals are: optimization of fin configuration [5,6,13], variation of PCM and heat transfer fluid temperatures during charging and discharging [8,12,14]. Reviewing literature it can be seen that the majority of studies, related to the performance of storage units, are focused on detailed analysis of heat transfer process during charging and discharging, especially on melting and solidification of PCM. The research is conducted both experimentally and/or using mathematical modelling and numerical techniques. ...
The paper presents the results of an experimental investigation of the thermal energy storage unit with phase change material (PCM) and finned tubes for heat transfer fluid (HTF). The research was focused on the discharge of the storage unit, mainly on the temperature variations of HTF at the outlet of the unit during this process. This temperature shows the quality of heat released from the storage unit and the exergy efficiency of the thermal energy storage process. In the research reported in this paper, the influence of HTF temperature at the inlet to the unit and HTF flow rate were analyzed. The experimental tests were performed at a specially developed stand allowing also for visualization of the process of PCM solidification. The results showed that the removal of heat from the storage unit is of relatively low intensity, even with the finned surface area on the PCM side, resulting in substantial losses of the quality (exergy) of accumulated heat. To reduce these losses temperature of HTF should be very close to the melting point of PCM or relatively small flow rates should be applied.
