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Showing papers on "Latent heat published in 2020"


Journal ArticleDOI
TL;DR: In this paper, the change in latent heat and thermal conductivity of nanoparticle dispersed phase change material (NDPCM) between the operating temperature range of 20°C and 37°C as required in low-temperature applications is analyzed.

235 citations


Journal ArticleDOI
17 Jul 2020
TL;DR: In this article, different methods of thermal energy storage including sensible heat storage, latent heat storage and thermochemical energy storage, focusing mainly on phase change materials (PCMs) as a form of suitable solution for energy utilisation to fill the gap between demand and supply to improve the energy efficiency of a system.
Abstract: The achievement of European climate energy objectives which are contained in the European Union's (EU) “20–20–20″ targets and in the European Commission's (EC) Energy Roadmap 2050 is possible, among other things, through the use of energy storage technologies. The use of thermal energy storage (TES) in the energy system allows to conserving energy, increase the overall efficiency of the systems by eliminating differences between supply and demand for energy. The article presents different methods of thermal energy storage including sensible heat storage, latent heat storage and thermochemical energy storage, focusing mainly on phase change materials (PCMs) as a form of suitable solution for energy utilisation to fill the gap between demand and supply to improve the energy efficiency of a system. PCMs allow the storage of latent thermal energy during phase change at almost stable temperature. The article presents a classification of PCMs according to their chemical nature as organic, inorganic and eutectic and by the phase transition with their advantages and disadvantages. In addition, different methods of improving the effectiveness of the PCM materials such as employing cascaded latent heat thermal energy storage system, encapsulation of PCMs and shape-stabilisation are presented in the paper. Furthermore, the use of PCM materials in buildings, power generation, food industry and automotive applications are presented and the modelling tools for analysing the functionality of PCMs materials are compared and classified.

223 citations


Journal ArticleDOI
TL;DR: In this article, a comparative study is carried out for the wall coupled with PCM and the wall with phase stabilised PCM to reveal the contribution of latent heat to the thermal performance of the wall and to determine the location, thickness and melting temperature of PCM for the maximum exploitation of the latent heat for different climatic conditions.

181 citations


Journal ArticleDOI
TL;DR: In this article, an innovative fractal-tree-shaped structure is introduced to construct the metal fin of a shell-tube LHS unit, and the effect of length ratio and width index on energy discharge performance is examined and analyzed.

180 citations


Journal ArticleDOI
Xiaohu Yang1, Junfei Guo1, Bo Yang1, Haonan Cheng1, Pan Wei1, Ya-Ling He1 
TL;DR: In this article, the effect of fin pitch and position on the thermal performance of the melting process was quantified via analyzing the melting front evolution, temperature and velocity distribution, melting rate and temperature uniformity.

179 citations


Journal ArticleDOI
TL;DR: In this article, an extensive overview of the research progress obtained in the field of phase change material (PCM) integrated with solar thermal applications is presented, along with the material problems and possible solutions.

167 citations


Journal ArticleDOI
TL;DR: In this article, the configuration of photothermal materials, as well as warm and cold evaporation surfaces, was designed to improve the performance of solar-steam generation in desalination and wastewater treatment.
Abstract: Interfacial solar-steam generation is a promising and cost-effective technology for both desalination and wastewater treatment. This process uses a photothermal evaporator to absorb sunlight and convert it into heat for water evaporation. However solar-steam generation can be somewhat inefficient due to energy losses via conduction, convection and radiation. Thus, efficient energy management is crucial for optimizing the performance of solar-steam generation. Here, via elaborate design of the configuration of photothermal materials, as well as warm and cold evaporation surfaces, performance in solar evaporation was significantly enhanced. This was achieved via a simultaneous reduction in energy loss with a net increase in energy gain from the environment, and recycling of the latent heat released from vapor condensation, diffusive reflectance, thermal radiation and convection from the evaporation surface. Overall, by using the new strategy, an evaporation rate of 2.94 kg m−2 h−1, with a corresponding energy efficiency of solar-steam generation beyond theoretical limit was achieved.

156 citations


Journal ArticleDOI
TL;DR: In this article, a numerical study was carried out through 3D lattice Boltzmann method with respect to different pin-fin configurations, expanded graphite (EG) content, PCM melting temperature, and heat flux conditions.

119 citations


Journal ArticleDOI
TL;DR: In this article, a novel latent heat thermal energy storage unit filled by metal foams with gradient in pore parameters was proposed to enhance thermal energy store performance, and the numerical results demonstrated that the positive gradient in porosity can provide the better heat transfer enhancement than the uniform and negative gradient cases, while simultaneously a better temperature uniformity was also obtained in comparison with the other arrangements.

117 citations


Journal ArticleDOI
TL;DR: In this article, nano-encapsulated phase change material (NEPCM) nanoparticles with particle sizes in the range of 250-350nm are synthesized and used as the working fluid for heat removal from a microchannel heatsink.

109 citations


Journal ArticleDOI
TL;DR: In this paper, the free convection phase change heat transfer of a suspension comprising nano-encapsulated phase change materials (NEPCMs) in a porous space is theoretically addressed, where the core of the nanoparticles is made of a phase change material and encapsulated in a thin shell.

Journal ArticleDOI
TL;DR: In this article, the effect of applying perforated fins on the thermal performance enhancement of a vertical shell and tube latent heat energy storage heat exchanger is experimentally investigated and the results are compared with those of the unfinned and solid finned heat exchangers as the base cases.

Journal ArticleDOI
Rui Huang1, Zhi Li1, Hong Wenhua1, Wu Qichao1, Xiaoli Yu1 
TL;DR: In this paper, the thermal performance of a battery module with 25-parallel 18650 lithium-ion battery has been numerically and experimentally investigated by adopting phase change cooling with phase change material (PCM).

Journal ArticleDOI
TL;DR: In this paper, passive cooling systems were constructed with a heat pipe and phase change material (PCM), and their performances were investigated with battery simulators with a temperature range of 25-55°C.

Journal ArticleDOI
Abstract: Latent heat storage (LHS) is considered to be a promising technique for thermal energy storage, due to its high energy storage density and nearly constant working temperature. However, the phase change materials (PCMs) used in LHS usually suffer from low thermal conductivity. In this work, the expanded graphite (EG) was applied to support n-eicosane (C20) via vacuum impregnation to prepare C20/EG composite PCMs. The DSC analysis indicated that the C20/EG15 has latent heat values of 199.4 J g−1 for melting and 199.2 J g−1 for freezing, exhibiting a large thermal storage capacity. The effect of EG on thermal performance was investigated and results suggested that the thermal conductivity of the composite with 15 wt.% EG (3.56 W m−1 K−1) is 14.4 times than that of pure C20 (0.25 W m−1 K−1), and the heating and cooling curves confirmed the EG has substantially improved the thermal transfer rate of samples. Furthermore, the electro-to-heat conversion measurement was carried out under small voltage (1.9–2.1 V), and the C20/EG15 exhibits high electro-to-heat storage efficiency (65.7%) under the voltage of 2.1 V. In all, the composite C20/EG15 is a potential candidate not only for electro-to-heat conversion but also for other thermal storage applications due to large latent heat capacity and high thermal conductivity.

Journal ArticleDOI
TL;DR: In this paper, phase change material (PCM) is filled to hollow bricks to improve thermal behavior by latent thermal storage, and a full-scale experiment was done to verify this model.
Abstract: Light-weight materials are comprehensively used to reduce the building weight in high-rise or super high-rise buildings, but they will reduce building thermal inertia remarkably, which can increase the air-conditioning load fluctuation and reduce indoor thermal comfortable. According to this condition, phase-change material (PCM) is filled to hollow bricks to improve thermal behavior by latent thermal storage. A numerical model with the heat transfer process of melting-solidifying was built, and a full-scale experiment was done to verify this model. Due to the filled PCM, the thermal performance of hollow bricks was improved obviously from experimental and numerical results. Under suitable phase-change temperature, the filled PCM can reduce the attenuation rate from 13.07% to 0.92%–1.93% and increase the delay time from 3.83 h to 8.83h–9.83 h. Meanwhile, the filled PCM can reduce the peak heat flux from 45.26 W/m2 to 19.19 W/m2-21.4 W/m2, but cannot reduce the average value. In addition, inner cavities were the better choice for PCM and there was an extra phase-change extent of close to 90% in favor of the different outdoor thermal environment. Finally, influence rules of latent heat and thermal conductivity coefficient of PCM were analyzed on temperature and heat flux in inner surfaces.

Journal ArticleDOI
TL;DR: In this article, a shape-stabilized composite phase change material (PCM) with encouraging thermal performances and effective encapsulation for applying to the building envelope is proposed. But, the leakage of molten PCM, the low thermal performances (latent heat and thermal conductivity) and the inappropriate melting temperature limit the application of PCM in buildings.

Journal ArticleDOI
TL;DR: In this paper, the sensible heat-based packed bed solar thermal energy storage systems for low temperature applications are discussed and the economic feasibility of the PBSS and comparison of sensible heat based PBSS with latent heat based PSS has also been discussed in detail.

Journal ArticleDOI
TL;DR: A wood-based 3D solar evaporator constructed via regulating the hydrophilicity of a surface burnt wood and adjusting the height of wood above water surface works efficiently in a water collection device, yielding 2.2 times more water than a common interfacial evaporator.
Abstract: Solar-driven interfacial evaporation with heat localization is an efficient method for large-scale water purification. However, due to the high latent heat of water evaporation and dilute solar flu...

Journal ArticleDOI
TL;DR: In this paper, the thermal performance of a glass window composed of glass, silica aerogel and phase change material (PCM) is investigated, which concurrently provides storage and restitution of heat, super thermal insulation and daylighting to the interior environment.

Journal ArticleDOI
TL;DR: In this paper, thermal performance of a conventional brick incorporating phase change material (PCM) is studied, and the influence of brick containing PCM on heating and cooling loads is examined considering different fusion temperatures, locations and quantities of PCM.
Abstract: In this work, thermal performance of a conventional brick incorporating phase change material (PCM) is studied. The influence of brick containing PCM on heating and cooling loads is examined considering different fusion temperatures, locations and quantities of PCM. Seasonal and annual thermal performance analysis of brick filled with PCM is evaluated and quantified for climatic conditions of Marmara region, Turkey, by an established and verified numerical model. The obtained results are compared with those of conventional brick and brick filled with phase stabilized material to identify the contribution of latent heat to energy saving. The results showed that filling the gaps of brick near the indoor ambient provides a higher energy conservation. The optimum fusion temperature of PCM varied from season to season in the range of 18–26 °C. An adverse effect of the latent heat activation was observed in summer season, causing higher cooling energy demand by an inappropriate selection of phase transition temperature. Then, an annual analysis was performed to determine the optimum melting temperature which was found to be 18 °C. By incorporating PCM to the brick, the annual thermal load decreased by 17.6%, 13.2% of which was attained due to the utilization of latent heat. The outcomes of this study suggest that the integration of PCM with optimum fusion temperature into the brick can reduce heating and cooling loads considerably in every season of the year and provide thermal comfort for the occupants.

Journal ArticleDOI
TL;DR: In this paper, a comb-like structural phase-change composite with high latent heat was designed by using poly (ethylene glycol) (PEG) chain, which tightly intertwines with a structural phasechange supporting material under induced dipole force due to structural compatibility.

Journal ArticleDOI
TL;DR: In this paper, the thermal performance during the melting process for phase change material (RT-50) in a horizontal LHTS unit was studied numerically with a view to optimizing the fin configuration.
Abstract: It has previously been proven that fins can significantly enhance the thermal performance of latent heat thermal energy storage (LHTS) units. Nevertheless, the magnitude of improvement, especially in a horizontal LHTS, is still less than that required to address some of the existing challenges in solar energy applications. The tendency of the phase change material (PCM) at the bottom of the horizontal storage to remain solid because of the absence of convection currents to promote heat transfer must be tackled practically for this technology to be viable in different thermal applications. Thus, the fin configuration around the circumference of the horizontal storage must be optimised to enhance the melting rate and therefore improving efficiency. In the present paper, the thermal performance during the melting process for PCM (RT-50) in a horizontal LHTS unit was studied numerically with a view to optimizing the fin configuration. The baseline case of bare heat transfer fluid (HTF) tubes was compared with finned surfaces with four different fin angles ( θ = 72 o , 60 o , 45 o and 30 o ) with four different heights (0.2, 0.4, 0.6 and 0.8 of the hydraulic radius of the annulus (Rh)). The average temperature of the PCM, its liquid fraction, and velocity distribution during the melting process were investigated. The numerical results showed that increasing fin height (using a fixed fin configuration: θ = 72 o ) significantly improved the thermal performance of the horizontal LHTS. When the fin height was varied from 0 (bare HTF tube) to 0.8 of Rh, a shortening of the total melting time by approximately 50% was observed. For this fin height 0.8 Rh, it was shown that having a smaller angle between the fins, with all of them mounted below the horizontal axis of the LHTS unit, led to significant enhancement in the thermal performance of the storage. This is because the enhanced heat transfer surfaces are targeted to the regions of the LHTS unit where heat transfer is poorest in the bare tube configuration, as mentioned above. Thus, the total PCM melting time was reduced by 6.7%, 14.3%, 16.7% and 10.0% when the fin angle was changed respectively from 72o to 60o, from 60o to 45o, from 45o to 30o, and finally from 30o to 15o.

Journal ArticleDOI
TL;DR: In this paper, the effect of thermal cycling on the thermophysical properties, such as phase transition temperature, latent heat, chemical compatibility, thermal stability and thermal conductivity, was studied.

Journal ArticleDOI
01 May 2020
TL;DR: In this paper, the influence of enclosure size in latent heat thermal energy storage systems embedded in a porous medium for domestic usage of LHEs was studied, and the effect of the enclosure size on energy storage performance was investigated.
Abstract: The aim of this paper is to study the influence of enclosure size in latent heat thermal energy storage systems embedded in a porous medium for domestic usage of latent heat thermal energy storage ...

Journal ArticleDOI
TL;DR: In this article, the authors evaluate the surface energy partitioning over land in ERA5 and concentrate on the surface latent heat flux, surface sensible heat flux and Bowen ratio against different reference data sets and using different modelling tools.
Abstract: . Climate reanalyses provide a plethora of global atmospheric and surface parameters in a consistent manner over multi-decadal timescales. Hence, they are widely used in many fields, and an in-depth evaluation of the different variables provided by reanalyses is a necessary means to provide feedback on the quality to their users and the operational centres producing these data sets, and to help guide their development. Recently, the European Centre for Medium-Range Weather Forecasts (ECMWF) released the new state-of-the-art climate reanalysis ERA5, following up on its popular predecessor ERA-Interim. Different sets of variables from ERA5 were already evaluated in a handful of studies, but so far, the quality of land-surface energy partitioning has not been assessed. Here, we evaluate the surface energy partitioning over land in ERA5 and concentrate on the appraisal of the surface latent heat flux, surface sensible heat flux, and Bowen ratio against different reference data sets and using different modelling tools. Most of our analyses point towards a better quality of surface energy partitioning in ERA5 than in ERA-Interim, which may be attributed to a better representation of land-surface processes in ERA5 and certainly to the better quality of near-surface meteorological variables. One of the key shortcomings of the reanalyses identified in our study is the overestimation of the surface latent heat flux over land, which – although substantially lower than in ERA-Interim – still remains in ERA5. Overall, our results indicate the high quality of the surface turbulent fluxes from ERA5 and the general improvement upon ERA-Interim, thereby endorsing the efforts of ECMWF to improve their climate reanalysis and to provide useful data to many scientific and operational fields.

Journal ArticleDOI
TL;DR: This analysis suggests that, for a single-stage DCMD powered by a waste heat stream, whether implementing latent heat recovery or not affects conventional metrics for energy efficiency but not the specific yield, which presents an intuitive and important framework for evaluating and optimizing energy efficiency in DCMD.

Journal ArticleDOI
TL;DR: Based on the enthalpy-porosity method, a transient model of the solidification heat transfer in the heat exchangers with five tree-shaped fin is established and numerically analyzed.

Journal ArticleDOI
15 Jul 2020-Energy
TL;DR: In this paper, a multi-objective optimization of the ORC using R245fa is conducted considering both thermodynamic performance and economic factors simultaneously, by means of Non-dominated sorting genetic algorithm-Ⅱ.

Journal ArticleDOI
TL;DR: The proposed methodology is a promising solution to the lack of thermal data with high spatio-temporal resolution required for field-scale ET modelling and can fill this data gap until next generation of thermal satellites are launched.
Abstract: The Sentinel-2 and Sentinel-3 satellite constellation contains most of the spatial, temporal and spectral characteristics required for accurate, field-scale actual evapotranspiration (ET) estimation. The one remaining major challenge is the spatial scale mismatch between the thermal-infrared observations acquired by the Sentinel-3 satellites at around 1 km resolution and the multispectral shortwave observations acquired by the Sentinel-2 satellite at around 20 m resolution. In this study we evaluate a number of approaches for bridging this gap by improving the spatial resolution of the thermal images. The resulting data is then used as input into three ET models, working under different assumptions: TSEB, METRIC and ESVEP. Latent, sensible and ground heat fluxes as well as net radiation produced by the models at 20 m resolution are validated against observations coming from 11 flux towers located in various land covers and climatological conditions. The results show that using the sharpened high-resolution thermal data as input for the TSEB model is a sound approach with relative root mean square error of instantaneous latent heat flux of around 30% in agricultural areas. The proposed methodology is a promising solution to the lack of thermal data with high spatio-temporal resolution required for field-scale ET modelling and can fill this data gap until next generation of thermal satellites are launched.