Showing papers on "Latent heat published in 2021"

A review of phase change heat transfer in shape-stabilized phase change materials (ss-PCMs) based on porous supports for thermal energy storage

Abstract: Latent heat thermal energy storage (LHTES) uses phase change materials (PCMs) to store and release heat, and can effectively address the mismatch between energy supply and demand. However, it suffers from low thermal conductivity and the leakage problem. One of the solutions is integrating porous supports and PCMs to fabricate shape-stabilized phase change materials (ss-PCMs). The phase change heat transfer in porous ss-PCMs is of fundamental importance for determining thermal-fluidic behaviours and evaluating LHTES system performance. This paper reviews the recent experimental and numerical investigations on phase change heat transfer in porous ss-PCMs. Materials, methods, apparatuses and significant outcomes are included in the section of experimental studies and it is found that paraffin and metal foam are the most used PCM and porous support respectively in the current researches. Numerical advances are reviewed from the aspect of different simulation methods. Compared to representative elementary volume (REV)-scale simulation, the pore-scale simulation can provide extra flow and heat transfer characteristics in pores, exhibiting great potential for the simulation of mesoporous, microporous and hierarchical porous materials. Moreover, there exists a research gap between phase change heat transfer and material preparation. Finally, this review outlooks the future research topics of phase change heat transfer in porous ss-PCMs.

Phase change material-integrated latent heat storage systems for sustainable energy solutions

Abstract: Thermal energy plays an indispensable role in the sustainable development of modern societies. Being a key component in various domestic and industrial processes as well as in power generation systems, the storage of thermal energy ensures system reliability, power dispatchability, and economic profitability. Among the numerous methods of thermal energy storage (TES), latent heat TES technology based on phase change materials has gained renewed attention in recent years owing to its high thermal storage capacity, operational simplicity, and transformative industrial potential. Here, we review the broad and critical role of latent heat TES in recent, state-of-the-art sustainable energy developments. The energy storage systems are categorized into the following categories: solar-thermal storage; electro-thermal storage; waste heat storage; and thermal regulation. The fundamental technology underpinning these systems and materials as well as system design towards efficient latent heat utilization are briefly described. Finally, the exciting research opportunities available to further improve the overall energy efficiency of integrated TES systems are discussed.

Numerical investigation on thermal behaviour of 5 × 5 cell configured battery pack using phase change material and fin structure layout

Abstract: Lithium-ion battery, the indispensable part of electric vehicles or hybrid electric vehicles because of their high energy capacity and power density but usually suffer from a high temperature rise due to heat generation within a battery. This heat generation is mainly a function of the state of charge and charge/discharge rate. A passive technique like phase change material cooling has receiving a wide recognition due to its high latent heat, compact nature, and lightweight without consuming any external power. In this article, the thermal performance of the battery module containing 5 × 5 lithium-ion battery arranged in series and parallel is evaluated using phase change material. Initially, the performance of a battery module is examined with and without PCM at different discharge rate. It was found that more heat is accumulated at the interior portion of the battery pack due to mutual heating and low heat dissipation ability of PCM at a higher discharge rate. To improve such interior heat dissipation, different fin structure layout like Type I, Type II, Type III and Type IV are proposed and analysed using maximum temperature and average temperature distribution in a PCM based battery pack. It reveals that fin structure layout of Type III minimizes heat accumulation at the interior with adequate melting time among all. Furthermore, charge and discharge characteristics are investigated at different rate using rest time, convection effect and fin structure. The results indicated that use of rest time and increasing convection effect not only reduces maximum temperature but also recover melting fraction of PCM. Results also illustrate that the thermal performance of PCM based battery pack slightly get affected with the use of fin structure at lower convection, but decreases the maximum temperature by 8.17% at higher convection. Heat source a function of the state of charge and charge/discharge rate are given using Ansys-Fluent code and results are reported in the form of maximum temperature, average temperature and melting fraction.

Melting heat transportation in radiative flow of nanomaterials with irreversibility analysis

Abstract: Melting phenomenon of PCMs (phase change materials) is mostly complemented with resilient variation in density of thermal heat. Thermal energy created from numerous sources can be stored in form of latent heat combination throughout melting process of a phase change materials. Thermal energy can be unconfined during the solidification processes. MPCS (microencapsulated phase change slurry) has noteworthy advantages particularly in high energy density and narrow temperature range for various heat energy application. Melting heat transportation has attracted the consideration of scientists and engineers due to its tremendous applications of technological, solidification, casting and industrial processes. A variety of phase change materials with low cost are commercially accessible and do significant work in different circumstances of temperature. Main motivation here is to investigate irreversibility in MHD convection flow of viscous liquid with melting effect over a stretched surface. Slip condition and Lorentz force behaviors are accounted. Energy expression is developed through dissipation, heat radiation and Joule heating. Irreversibility exploration is modeled through second law of thermodynamics. Brownian diffusion and thermophoresis are taken. First order chemical reaction is deliberated. Nonlinear expressions are reduced to ordinary one employing transformation. The obtained systems are solved for the convergent solutions through ND-solve method. Variation of velocity field, entropy rate, temperature, Bejan number and concentration distribution are scrutinized. Velocity filed rises versus higher melting variable. Larger melting parameter decreases the temperature distribution. Concentration and temperature have similar effects against thermophoresis variable. Bejan number and entropy rate have opposite outcome via melting parameter. Higher radiation parameter reduces the entropy rate. For higher radiation both entropy rate and Bejan number have same effect. Main observations are concluded.

Performance investigation of a passive battery thermal management system applied with phase change material

Abstract: Lithium-ion batteries will produce a lot of heat during working, which can increase the temperature and temperature difference in the battery module, and seriously impair the capacity, life, and safety of the batteries. Therefore, an effective thermal management system should be implemented to control the temperature of the batteries, while reducing the energy consumption and cost of the system as much as possible. In this paper, a passive, low-cost battery thermal management system consisting of pouch lithium-ion cells and phase change material units is designed. Based on the heat production process of the battery and heat transfer theory of the phase change material, a numerical model is built and the performance of the thermal management system is analyzed. It is found that the phase change material units can effectively decrease the maximum temperature and the maximum temperature difference on the cell at the end of discharge, and thus have good heat storage capability and temperature equalization capability. After insulating heat dissipation from the surfaces of the phase change material units, a temperature retaining function can also be achieved. The effects of the design parameters of the phase change material unit on its thermal management performance are further investigated, including the thermal conductivity, viscosity, and latent heat of the phase change material, the thickness of the phase change material unit, and the thermal conductivity of the unit shell. It could provide theoretical references and technical means for the design and implementation of passive, low-cost battery thermal management systems applied with phase change materials.

Phase change materials in solar domestic hot water systems: A review

Abstract: In this work, technologies related to the storage of solar energy, utilizing the latent heat content of phase change materials for the production of domestic hot water are reviewed. Many researchers have been involved in this field in order to accomplish the targets of environmentally friendly solutions and higher efficiency. For domestic use, materials with melting temperature between 40 and 80 °C are commonly studied, with paraffins, fatty acids, salt hydrates and alcohols being the most popular. For harvesting the solar radiation, usually flat plate or evacuated tubes solar collectors are used, either commercial ones or modified. The storage unit may include only phase change material or it can have a hybrid form combined with water. The outcome of the most studies, is that the addition of phase change materials in comparison to systems without latent storage, increases the duration of heat release towards the domestic water at the end of the day and also increases the solar collector's efficiency because it does not experience large temperature fluctuations. However, difficulties emerge during the selection of the appropriate storage material as this must have a high melting temperature in order to provide hot enough domestic water, but not higher than the temperature that the solar collector can produce, in order to fully melt the material. Moreover, investigation is necessary for the selection of the optimum water flow rate that minimizes the charging duration and maximizes the system efficiency and hot water amount. Another challenge that researchers face is the low thermal conductivity of many phase change materials. For this purpose, methods for improving the performance of the systems have been examined and they are also reported.

Exploiting radiative cooling for uninterrupted 24-hour water harvesting from the atmosphere

Abstract: Atmospheric water vapor is ubiquitous and represents a promising alternative to address global clean water scarcity. Sustainably harvesting this resource requires energy neutrality, continuous production, and facility of use. However, fully passive and uninterrupted 24-hour atmospheric water harvesting remains a challenge. Here, we demonstrate a rationally designed system that synergistically combines radiative shielding and cooling-dissipating the latent heat of condensation radiatively to outer space-with a fully passive superhydrophobic condensate harvester, working with a coalescence-induced water removal mechanism. A rationally designed shield, accounting for the atmospheric radiative heat, facilitates daytime atmospheric water harvesting under solar irradiation at realistic levels of relative humidity. The remarkable cooling power enhancement enables dew mass fluxes up to 50 g m-2 hour-1, close to the ultimate capabilities of such systems. Our results demonstrate that the yield of related technologies can be at least doubled, while cooling and collection remain passive, thereby substantially advancing the state of the art.

Investigation of the effect of adding nano-encapsulated phase change material to water in natural convection inside a rectangular cavity

Abstract: The present simulation aims to investigate adding NEPCM nanoparticles to water in the natural convection inside a cavity by using FVM method and SIMPLE algorithm Nano-encapsulated phase change material (NEPCM) consists of a shell and core with phase change property The NEPCM particles in base fluid have the ability to transfer heat by absorbing and dissipating heat in the liquid-solid phase change state In this study, the energy wall phenomenon due to the phase change of NEPCM core has appeared that the whose energy transfer strength is proportional to the latent heat of NEPCM core and the thickness of the energy wall Moreover, the relationship between the energy wall and the heat transfer rate is payed attention, and the effects of the energy wall parameters including strength, thickness, and event location of energy wall and volume fraction are studied on the energy wall and heat transfer rate According to the obtained results, adding NEPCM to the water enhances its heat transfer up to 48% in order to increase heat capacity of water-NEPCM mixture Also, best heat transfer rate happens when the energy wall is at the center of the cavity Moreover, a relation is presented for the thermal expansion coefficient of NEPCM, which considers the effects of the thermal expansion coefficient of the core and shell material

Sunlight-activated phase change materials for controlled heat storage and triggered release

Abstract: We report the design of photo-responsive organic phase change materials that can absorb filtered solar radiation to store both latent heat and photon energy via simultaneous phase transition and photo-isomerization. The activation of photo-switches by long wavelengths ≥530 nm in the visible light range at a low irradiance is achieved, in the absence of high-intensity light sources, by the ortho-substitution of azobenzene units. The facile transition from crystalline to liquid phase is enabled by appending an aliphatic group on the photochromic moiety. The sunlight-activated liquid phase exhibits an exceptionally long heat storage without crystallization for nearly two months, and the release of energy is triggered by a short irradiation at 430 nm. The successful demonstration of photo-controlled latent heat storage accomplished by solar irradiation opens a new horizon on solar energy harvesting by functional organic materials, as a complementary system to photocatalysts and photovoltaic materials.

Phase change material-based thermal energy storage

Abstract: Summary Phase change materials (PCMs) having a large latent heat during solid-liquid phase transition are promising for thermal energy storage applications. However, the relatively low thermal conductivity of the majority of promising PCMs (

Melting effect in triplex-tube thermal energy storage system using multiple PCMs-porous metal foam combination

Abstract: The study was performed on the melting performance of phase change materials (PCMs) inside a triplex heat exchanger with double-sided heat transfer. The purpose of numerical simulation in this paper was to investigate the effects of using three-layer PCM with different melting temperatures instead of single-layer PCM and also the effect of their combination with Al6061 metal foam to compensate for the major problem of low thermal conductivity of PCMs. According to research, despite the reduction of melting rate in pure three-layer PCM compared to pure single-layer PCM, the addition of Al-6061 metal foam to them caused the melting rate of three-layer PCM to be superior. By identifying porous three-layer PCM as a better case, the effect of changing the porosity arrangement of layers with constant average porosity of 0.95 was investigated. In the next step, this study was performed on different porosity numbers. As expected, with decreasing the porosity, the melting rate increased due to increased heat transfer. To achieve higher efficiency, the effect of heat transfer fluid (HTF) temperature was also investigated and plotted. The relevant results showed the significant effect of temperature change at the melting time of the system. Therefore, every case or combination of any of the above studies, which increased the melting efficiency, can be of great help in optimizing energy storage heat exchangers based on latent heat.

Thermal energy storage performance of PCM/graphite matrix composite in a tube-in-shell geometry

Abstract: Melting heat transfer performance and measuring energy storage efficiency via total melting time of PCM/graphite matrix in a tube-in-shell for solar thermal energy storage and recovering waste heat applications is studied experimentally. The phase change material (PCM)-organic/paraffin (P56-58), is impregnated into the graphite matrix, with the bulk density of 50 g/L. The effect of inlet temperature (Tinlet = 75 °C and 85 °C) of heat transfer fluid (HTF) on total melting time is obtained. The time-history of temperature measurements, thermal camera imaging, and liquid fraction are obtained to reveal the thermal performance of PCM/graphite matrix in a tube-in-shell latent heat thermal energy storage (LHTES) system in detail. The results show that the PCM/graphite matrix has a remarkable effect on the phase change heat transfer and total melting time. The thermal performance of the PCM/graphite matrix is presented comparatively with the conventional tube-in-shell storage unit. Effective thermal conductivity which enhances the heat transfer rate is shown to increase 35 times compared to that of pure paraffin. The total melting time decreases by about 92% compared to the conventional tube-in-shell unit. Uniform melting behaviour is observed based on highly conductive abundant thermal paths for PCM/graphite matrix. Heat transfer takes place by dominant conduction for the PCM/graphite matrix. Leakage issue is prevented using graphite matrix encapsulation. Total melting time is decreased by about 31% with the increase in HTF inlet temperature for the PCM/graphite matrix.