Figure 10 - uploaded by Lavinia Socaciu
Content may be subject to copyright.
Source publication
Thermal energy storage (TES) systems provide several alternatives for efficient energy use and conservation. Phase change materials (PCMs) for TES are materials supplying thermal regulation at particular phase change temperatures by absorbing and emitting the heat of the medium. TES in general and PCMs in particular, have been a main topic in resea...
Context in source publication
Context 1
... PCM utilized in PCM assisted sun-shading system is hydrated salt CaCl 2 ·6H 2 O. This system is very suitable to be utilized under the hot summer climate, especially for those areas with signifiant daytime and nighttime temperature fluctuations [27]. In figure 9 is presented conventional and PCM sun-shading system. During the daytime with high temperatures (compared to the thermal comfort value), the face of the inner blind integrated with PCM is rotated to be exposed to the solar radiation so that excess solar energy is stored in PCM, attenuating the temperature fluctuations inside the room. During the night time with relatively low temperatures (compared to the thermal comfort value), the face of the inner blind integrated with PCM is rotated to be exposed to the room air so that the stored energy is released back to the room, avoiding over-reduction of the room temperature below the thermal comfort value. In order to investigate the thermal performance of the under-floor electric heating system with the shape-stabilized PCM plates, an experimental house with this system was set up in Tsinghua University, Beijing, China. The experimental house was equipped with the under-floor electric heating system including shape stabilized PCM plates. It had a double- glazed window facing south, covered by black curtain. The roof and walls were made of polystyrene wrapped by metal board. The under-floor heating system included polystyrene insulation, electric heaters, PCM, some wooden supporters, air layer and wood floor [19]. Under-floor electric heating system with shape-stabilized PCM plates is presented in figure 10. Different from conventional PCM, shape-stabilized PCM can keep the shape unchanged during phase change process. Therefore, the PCM leakage danger can be avoided. This system can charge heat by using cheap nighttime electricity and discharge the heat stored at daytime [25]. A roof-integrated solar air heating/storage system uses existing corrugated iron roof sheets as a solar collector for heating air. A PCM thermal storage unit is used to store heat during the day so that heat can be supplied at night or when there is no sunshine. The system operates in three modes. During times of sunshine and when heating is required, air is passed through the collector and subsequently into the home. When heating is not required air is pumped into the thermal storage facility, melting the PCM, charging it for future use. When sunshine is not available, room air is passed through the storage facility, heated and then forced into the house. When the storage facility is frozen, an auxiliary gas heater is used to heat the home. Adequate amounts of fresh air are introduced when the solar heating system is delivering heat into the home as shown figure 11 [23]. PCM asisted ceiling was investigated at the University of Nottingham (2002). This is a replacement of a full air conditioning system by the new system that is a nighttime cooling system, which is also easy to retrofit. The proposed module (figure 12) it is ceiling-mounted with a fan to throw air over the exposed ends of heat pipes. The other end of the heat pipes is in a PCM storage module. During the day, the warm air generated in the room is cooled by the PCM i.e. heat is transferred to the PCM. During the night, the fan is reversed and the shutters are opened such that cool air from the outside passes over the heat pipes and extracts heat from the PCM. The cycle is then repeated next day [19]. The Sustainable Energy Centre at University of South Australia (2000) started work with PCMs in the mid 1990’s with the development of a storage unit that can be used for both space heating and cooling. The night time charging and day time utilization process during both heating and cooling seasons for a storage system comprising of two different PCMs integrated into a reverse cycle refrigerated heat pump system utilizing off peak power. As the air is forced through the system it undergoes a two-stage heating or cooling process. It first goes through one PCM and then the second as shown in figure 13 [23]. The melting / freezing point of the first material are below comfort temperature, while the second material has a melting/freezing point above comfort temperature. During the winter, the airflow is adjusted so that the system stores heat at night (by both materials melting) and releases heat at a temperature above comfort conditions (by freezing) at daytime. During summer, the airflow direction is reversed and the system stores cold energy at night and it releases the cool air below comfort temperature at daytime [23]. The incorporation of PCMs into building elements takes the advantage of latent TES for additional energy savings. The development of energy-storing building is a solution to the on-going quest for energy conservation, and also to improving the indoor environment in which people work and live. In terms of thermal comfort, it is envisaged that the indoor environment of a building which uses PCM construction materials will have significantly lower mean radiant temperatures and more thermal stability, having less likelihood of overheating and fewer temperature fluctuations. Thermal improvements in a building due to the inclusion of PCMs depend on the type of PCM, the melting temperature, the percentage of PCM mixed with conventional material, the climate, design and orientation of the construction of the building. The optimization of these parameters is fundamental to demonstrate the possibilities of success of the PCMs in building ...
Similar publications
In this paper, experimental and numerical investigations are performed for heat transfer enhancement in a horizontal Latent Thermal Energy Storage System using multiple heat transfer tubes and modified shell designs. Stearic acid is used as phase change material and it is placed in the annulus of steel shell and copper tubes carrying water as the h...
This paper studies the influence of material thermal properties on the charging dynamics in a low temperature Thermal Energy Storage, which combines sensible and latent heat. The analysis is based on a small scale packed bed with encapsulated PCMs, numerically solved using COMSOL Multiphysics. The PCMs studied are materials constructed based on typ...
In the last years, the ability to absorb and release a large amount of thermal energy during their phase transition has led that Phase Change Materials (PCM) have been more and more used for thermal energy storage (TES) in buildings. In fact, thanks to their proprieties it is now possible to shift the power demand of the building to off-peaks perio...
Thermal energy storage with phase change materials (PCM) provides high storage capacities in small temperature intervals. For the design of storage systems, the enthalpy curve of the used PCM has to be known with high precision.
The T-History method has evolved to a widely used method for the measurement of the enthalpy as a function of temperature...
Phase Change Materials (PCM) can absorb energy while heating as it undergoes a change in phase and emits the absorbed energy to the environment in a reverse cooling process. Organic PCMs have been extensively used for thermal energy storage in building applications due to its phase transition temperature within the human comfort temperature zone. I...
Citations
... Thermal energy storage (TES) systems can be categorized into sensible heat storage [2,3], latent heat storage [4,5], and thermochemical energy storage systems [6,7]. Sensible heat storage systems utilize heat directly, but their low energy density requires more space. ...
The energy and exergy analyses were performed for a laboratory-scale latent heat thermal energy storage (LTES) using hexahydrate calcium chloride (CC6) as phase change material (PCM) in a staggered tube array configuration , placed horizontally. The PCM melting and solidification process within the tube array was investigated by performing a numerical analysis using transient two-dimensional Navier-Stokes equations and Realizable k-ε turbulence model to predict flow and heat transfer. The enthalpy-porosity technique was applied to model PCM melting and solidification. The accuracy of the numerical model was validated against experimentally obtained data where the numerically predicted and measured air temperature at the tube array outlet and PCM temperatures were compared. Additionally, the pressure drop in the array and the average peripheral heat transfer coefficient calculated from the numerical results were compared to the well-known Zukauskas correlation (Zu). The results show that the melting and solidification process of PCM in the tubes of the array is asymmetric in nature, with the PCM melting taking slightly longer compared to the solidification process. It was also observed that the energy quantity was higher compared to the exergy quantity, as exergy considers entropy generation and accounts for irreversibility within the system.
... During phase changes, thermal energy is either absorbed (melting, evaporation) by the considered material, or released (solidification, condensation), at a constant temperature. Thermal energy storage (TES) involves storing energy by heating, freezing, solidifying, melting, or evaporating a specific material [6]. The energy is available to use when the process is repeated in the reversed mode. ...
Phase-change materials (PCMs) are becoming more widely acknowledged as essential elements in thermal energy storage, greatly aiding the pursuit of lower building energy consumption and the achievement of net-zero energy goals. PCMs are frequently constrained by their subpar heat conductivity, despite their expanding importance. This in-depth research includes a thorough categorization and close examination of PCM features. The most current developments in nanoencapsulated PCM (NEPCMs) techniques are also highlighted, along with recent developments in thermal energy storage technology. The assessment also emphasizes how diligently researchers have worked to advance the subject of PCMs, including the creation of devices with improved thermal performance using nano-enhanced PCMs (NEnPCMs). This review intends to highlight the progress made in improving the efficiency and efficacy of PCMs by providing a critical overview of these improvements. The paper concludes by discussing current challenges and proposing future directions for the continued advancement of PCMs and their diverse applications.
... The inorganic salt hydrate PCMs, such as CaCl 2 ⋅6H 2 O [3][4][5][6][7], NaOH⋅3.5H 2 O [8][9][10], KF⋅4H 2 O [11,12], CaBr 2 ⋅6H 2 O [13], Na 2 SO 4 ⋅10H 2 O [14,15], LiClO 4 ⋅3H 2 O [16], have become prominent in LHS due to their low fire hazard properties, large latent heat of fusion, high volumetric energy densities, and the relatively elevated thermal conductivities amongst other PCMs [17]. Specifically, CaCl 2 ⋅6H 2 O has received extensive interest due to its low cost, wide availability, high volumetric storage density, and operational safety. ...
Calcium chloride hexahydrate (CaCl 2 ⋅6H 2 O) based phase change material (PCM) is promising for latent heat storage due to its favorable thermal properties, but supercooling and thermal cyclic instability limits its wider application. We examine the role of nucleation agents, in particular strontium chloride hexahydrate (SrCl 2 ⋅6H 2 O), as an additive to the PCM, on the degree of supercooling and the latent heat. Utilizing a water bath and a cooling chamber, we systematically evaluate the degree of supercooling in various PCM samples, while X-Ray diffraction and microscopic analysis are employed to characterize the role of the additive. The results suggest that particle shapes of the additives and their crystallographic phase contribute significantly to supercooling suppression. Optimizing a tradeoff between supercooling and latent heat reduction for long-term nucleation performance, we identify designer PCM composition with an optimal 3 wt% of SrCl 2 ⋅6H 2 O for an automated thermal cycling system by differential scanning as well as drop calorimetry. Incorporating 2 wt% potassium chloride (KCl) shifts the composition at the peritectic point away from the unfavorable CaCl 2 ⋅4H 2 O phase, enhancing the freeze-thaw cycle stability of CaCl 2 ⋅6H 2 O. Notably, the latent heat variation is ~0.08% over 1000 freeze-thaw cycles.
... It captures heat during peak daytime and releases it during cooler nighttime periods. TES systems comprise sensible heat storage systems [9,10], latent heat storage systems [11,12], and thermochemical energy storage systems [13,14]. Sensible heat storage utilizes sensible heat, but its low energy density demands more space. ...
While dry cooling systems excel in water conservation compared to wet cooling systems, their performance at high ambient temperatures remains subpar. This study explores a novel latent heat storage module, acting as a water-free pre-cooler to lower temperature of ambient air into the dry cooling system. Four module designs were constructed, based on a pervious concrete and a custom-made inorganic phase change material, calcium chloride hexahydrate, with stable latent heat over 1,000 freeze–thaw thermal cycles. This marks the first-time integration
of inorganic phase change material into pervious concrete through micro- and macro-encapsulation. A forced-air
heat transfer apparatus was used to evaluate the modules’ thermal performance and heat transfer characteristics,
revealing substantial thermal capacity increases of the modules- from 20.0 to 49.2 kWh/m3 charging and 20.3 to 43.6 kWh/m3 in discharging. The module with highest heat storage capacity investigated in this work is the pervious concrete module with micro-encapsulated phase change material and cast around a metal tube array filled with phase change material, which consistently reduces temperature of the airflow at 35℃ and 0.86 m/s by an average of 2℃ over three hours, showing potential as a pre-cooler in dry cooling applications.
... P. Naphon [52] proposed that the heat exchanger consists of a shell and helically coiled tube unit with two different coil diameters. Ashish [54] discussed about various thermal energy storage system and their significance in the thermal system. Syukri Himran et al [55] studied thermal energy storage in paraffin-wax using tube array on a shell and tube heat exchanger. ...
Energy is one of the most important factors affecting the stability of any system and therefore, dealing with different energy systems is very important to get the most out of energy resources. Energy sources are divided into conventional and renewable sources, and both are involved in securing the energy needed to meet the requirements of different engineering systems, and they also participate to a large extent in a number of supporting systems to complement the use of different types of energy. Heat exchangers are used to transfer heat between two process streams. Heat exchangers can be used for cooling, heating, condensing, boiling or evaporating purposes. Efficiency and efficiency can be measured by the amount of heat transfer using the least heat transfer area and pressure drop. The objective of this work was to manufacture two coil-in-tube heat exchangers with step1" and 2" and to analyze the thermal efficiency of the two heat exchangers.
... These materials are effectively combined with active heat control to minimize their work cycle and optimize their capacity. Latent thermal storage is one of the most effective methods of accumulating thermal energy [3]. PCMs have found various applications based on their state change temperature. ...
... One of the foremost broadly used of these algorithms is the velocity-Verlet algorithm (Eqs. [2][3][4] [39,40]: ...
... The main reason for adding NPs to the PCMs was these samples' low charge rate and discharge processes. A nanochannel with Fe type was modeled with a 100 × 100 × 200 nm 3 . In this atomic arrangement, periodic boundary Y.X. ...
... PCMs can be classified into four categories based on their phase transition: solid-liquid, solid-solid, liquid-liquid, and gas-liquid. Solidliquid PCMs are the most widely studied for cooling and heating applications [21]. ...
... The energy demand varies with time according to thermal drying system requirements. This change can be controlled through the integration of TEAs with PCMs [16]. The selection of TEAs for a drying plant depends on many factors, such as supply temperature requirement, economics, storage duration, heat losses, storage capacity, and available space [17]. ...
... Sensible TEA systems accumulate TE by modifying the temperature of the utilized storage medium, like soil, brine, water, rock, etc. Latent systems accumulate TE by phase change, e.g., the storage of heat through melting paraffin waxes and cold storage water/ice. In addition, TAs can be performed through chemical reactions [16,18]. Fig. 3 illustrates the categories of TEA units [19]. ...
Researchers worldwide are studying thermal energy storage with phase change materials because of their substantial benefits in the enhancement of energy efficiency of thermal drying systems. A two-stage convective-vacuum impulsive drying plant is a technology for the manufacturing of chemical and food products with high quality and low energy costs. Energy consumption during the drying process is the main indicator in terms of economy. In this paper, a brief and focused review of the peculiarities of TEAs with PPCMs and opportunities of their application in such drying systems is done and discussed. The paper described the mentioned manufacturing system. The advantages of paraffin wax and thermal conductivity improvement techniques were demonstrated for their use as heat storage materials in CVID drying units. The results of similar previous studies were presented. The results of the experimental studies conducted by the researchers proved that the use of heat accumulators with PCMs increased the overall energy efficiency of drying systems. Finally, integration of TEAs based on modified PPCMs in the CVID system was recommended to intensify thermal energy, reduce thermal influence on the main indicators of the vacuum pump during the evacuation process, and decrease production costs.
... Simone Raoux and Matthias Wuttig's book [2] presents the history of PCMs and their applications. Zalba et al. [3], Nkwetta and Haghighat [4], and Socaciu [5] reviewed the applications of different PCMs based on their properties and published their results in various reputed journals. Based on their results, system efficiency can be seen to mainly be affected by the physical and chemical properties of the PCM. ...
... Discharge time was lower compared to the melt time. Lavinia [15] have carried out study of thermal energy storage for different fields and applications. The study consists of parameters like climate; design and construction of the building which affects the thermal properties of PCM for building applications. ...
The latent heat energy storage using Phase Change Material (PCM) has an enormous appeal due to its profitable points associated with density and thermal characteristics. In this regard, a heat exchanger is modelled and analyzed to visualize the thermal behaviour and melting progression of PCM in a circular-shaped enclosed erect vessel via CFD tool. This work analyzes a multiphase transient study of a U-shaped copper tube placed in a closed cylindrical vessel through which heat transfer fluid flows for transferring heat to the PCM. This work shall be advantageous to the researchers to realize the thermal performance, time of PCM melting etc., to carry out research related to solar heat storage. The present study reports substantial decrease in the time taken to melt all the PCM filled in the container. Almost 32% of time is saved in the process of melting of PCM and thus improving the efficiency of the energy storage system.
