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Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

39237675
71848
10.1038/s41598-024-71848-8
Article
Enhancing the performance of paraffin's phase change material through a hybrid scheme utilizing sand core matrix
Nabwey Hossam A. eng_hossam21@yahoo.com

12
Tony Maha A. 23
1 https://ror.org/04jt46d36 grid.449553.a 0000 0004 0441 5588 Department of Mathematics, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, 11942 Al-Kharj, Saudi Arabia
2 https://ror.org/05sjrb944 grid.411775.1 0000 0004 0621 4712 Basic Engineering Science Department, Faculty of Engineering, Menoufia University, Shebin El-Kom, 32511 Egypt
3 https://ror.org/05sjrb944 grid.411775.1 0000 0004 0621 4712 Advanced Materials/Solar Energy and Environmental Sustainability (AMSEES) Laboratory, Faculty of Engineering, Menoufia University, Shebin El-Kom, 32511 Egypt
5 9 2024
5 9 2024
2024
14 207558 7 2024
31 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Smart waste management and valorisation is presented in the current investigation. Iron is collected from mining wastewater stream and augmented with sand as a supporting material to produce sand core. The sand core pellets encapsulated in paraffin’s to enhance its feasibility as phase change material (PCM). Sand core was characterized using X-ray diffraction and Scanning Electron Microscope (SEM) augmented with energy dispersive X-ray spectrum analysis. Experimental test is achieved by mixing sand core/iron and paraffin that is signified as an encapsulated phase change material. The encapsulated sand core-PCM is embedded in varies mass weights of percentages of 0.5, 1.0, 1.5 and 2.0% and labeled as 0.5%-sand core-PCM, 1.0%-sand core-PCM, 1.5%-sand core-PCM and 2.0%-sand core-PCM. The encapsulated sand core-PCM is embedded into a heat exchanger of the vertical type model that is connected with a flat plate solar collector. Such collector is heating the heat transfer carrier, which is exposed to the heat exchanger for melting the PCM. The experimental work is conducted across the solar noon where the solar intensity in the region is reached to 1162 W/m2 at the time of conducting experiments. Water is applied and supposed as the working heat transfer fluid transporter and pumped into the system at the rate of 0.0014 kg per second. The experimental result revealed that the heat gained recorded an enhancement from 7 to 48 kJ/min when the 1.5%-sand core-PCM system is applied. Thus, the results showed the system is a good candidate by increasing the system efficiency with 92% as a potential solution of solar energy storage at the off-time periods.

Keywords

Mining waste valorisation
Phase change material (PCM)
Solar energy storage
Sustainability
Sand core-PCM
Subject terms

Environmental sciences
Environmental chemistry
http://dx.doi.org/10.13039/100009392 Prince Sattam bin Abdulaziz University PSAU/2024/01/921606 Nabwey Hossam A. issue-copyright-statement© Springer Nature Limited 2024
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pmcIntroduction

Globally, there is a plentiful upsurge in energy demand with depletion in the conventional fossil fuel. Also, modernization and industrialization are leading to the upsurge in energy depletion as well as the carbon discharges into the environment in the form of emissions that cause environmental pollution1,2. The consumption of energy in the last decades is in increase with a significance of 20% deduction3. In this regard, the role of academia and researchers is looking for an alternative energy source.

Amongst the numerous thermal energy storage (TES) facilities, latent heat TES arrangements are attaining a massive concern2. Phase change materials (PCM) is of vast significance because a kind of advanced thermal energy storage necessities since they possess excessive density of TES facility as well as their isothermal nature through the phase change routine. The technique might store massive quantities of thermal energy through changing the physical state transition of the substance4–6. Because of its economic cost, chemical stability, the wide-ranging of melting temperatures outline and high heat of fusion/solidification, organic PCM based paraffin is signified as the numerous used organic PCM substance7,8. But their drawbacks are still standing their applications since their molten state leakage that requires a PCM confinement through encapsulation9,10. Recent advances in the such field announced cupper nanoparticles into paraffin wax PCM11,12. Also, alumina nanoparticles are introduced and showed an additional time savings13–16. Further, multi walled carbon nanotubes augmented base PCM is introduced17 and showed an enhancement in the thermal performance. Nevertheless, nanoparticles’ cost of preparation is still not economic18–20. Thus, the design of the cost efficient PCM is essential.

In the building sector and heat soring opportunities, paraffin as an organic phase change material (PCM) that has been signified as an effective PCM in various applications21,22. Domestic water heating and hot water storage is in signified as inescapable and essential use23. The presentation of renewable energy in the method of solar energy storage through PCM storing facility is a viable opportunity24,25. PCM might store the solar energy at the off-sun periods then could release them at the peak periods. Such material displayed significant results16,26. But, the unfortunate thermal conductivity of PCM is nevertheless the topmost drawback since its low thermal conductivity27–29.

Numerous investigators have introduced the addition of various fillers into the paraffin’s to improve its thermal properties. The performance in all cases is improved than the pristine PCM system with some limitations including the cost of the process30. Thus, searching for cost-efficient substances as filler into PCM is attaining the scientists’ attention. On the other hand, with the concept of “Sustainable Society Approach”, waste management and valorization is essential for attaining a novel PCM system for a non-polluting model31–33. Such concept could be realized through using natural clean materials as well as valorizing the waste streams. For instance, previous investigators have already concluded that elemental recovery from waste stream could be valorized and introduced in numerous applications such as wastewater treatment34–37. But, to the best of the author’ knowledge, such materials are not applied so far in energy storage systems.

To date, numerous literatures cited are based on PCM enhancement through fresh chemicals use. However, the particularity alternative elemental recovery source is still limited. To the best of the authors’ knowledge, PCM designs projected in the previously published literature articles do not investigate the performance of using sand augmented with iron s a core sand supporting paraffin’s is not applied so far.

Phase change materials (PCMs) are such substances that are proficient in storing thermal energy through the absorption or may be releasing the signified term of latent heat by changing in the materials’ physical state for instance their melting and freezing process. PCM materials can be categorized by the existence in at least two structurally distinct solid phases, i.e. amorphous phase and one or may be more in its crystalline phase15. Several materials16,18 have been used to improve the heat storage capacity and the thermal behavior of the paraffin’s PCM38. Notably, Sand is previously reported that might improve the diffusivity of the PCM, which is enhanced by sand addition. Various chemical bonding occurs among pure and paraffin material. The addition of additive material could be signified as simple and cheap technique that is applied to enhance the paraffin’s’ based PCM substances since their improvement in the performance in thermal energy storage. For lower temperature applications, the addition of sensible heat material like water, rock and sand is considered as the easiest and cheapest way to enhance the paraffin performance. Thus, such combination is showing an increase in temperature since its lower thermal conductivity and high heat capacity, which allows it to retain heat. However, such systems are not combined for thermal energy storage. In this regard, high sustainability and efficiency is attained through such commination of iron5 and sand39 as a storage materials in harnessing the full potential of thermal energy storage solution in a sustainable win–win routine since iron is collected from a waste stream.

Herein, in the current study, the recovery of iron from wastewater streams is applied and the recovered iron is supported sand to be a core-sand. The core sand is inserted into the paraffin’s as a PCM material. The energetic performances of the PCM system is investigated and the experimental considerations are studied. Hence, the system is in agreement with the line of sustainable energy tools, since using green and economically well organized environmentally energy storage system.

Experimental section

Materials

A commercial organic Paraffin wax that possess a melting temperature ranged from 48–53 °C is used as the base phase change material (PCM). The melting latent heat of fusion of such wax is 190 kJ/kg and the value of the thermal conductivity recorded is 0.21 kJ/kg °C. The full characterization of paraffin PCM is exhibited in Table 1.Table 1 Paraffin wax thermo-physical properties.

Properties	Value	Unit	
Melting temperature	48–53	°C	
Latent heat of fusion	190	kJ/kg	
Solid density	930	kg/m3	
Liquid density	830	kg/m3	
Thermal conductivity	7.1	W/mK	
Solid specific	2.1	kJ/kg°C	

Iron source is precipitated from coal mining wastewater through a selective precipitation route. Then, iron core sand is prepared using beach sand and the iron is precipitated through the previous method37 by mixing iron with sand prior to oven drying (103ºC) and then repeated three times and afterwards is calcined in an electric oven (500 °C). The amount of iron on the sand surface was 13.5 mg-Fe/gm-sand. The attained material is called core sand. The addition of high thermal conductivity material might elevate the thermal conductivity of paraffin PCM and increase the melting temperature of paraffin. Subsequently, 15 g of pristine Paraffin is mixed with the core sand then subjected for ultrasonic dispersed procedure at 60 °C through the exposure into the ultrasonic technique of a bath type at 40 K Hz using a model (DAIHAN Wisd WUC-A03H). The addition of the core sand into paraffin’s is ranged from 0.5, 1.0, 1.5 and 2.0% and labeled as 0.5%-sand core-PCM, 1.0%-sand core-PCM, 1.5%-sand core-PCM and 2.0%-sand core-PCM.

Experimental methodology

Vertical type of heat exchanger of a double pipe is linked to a flat plate type of solar concentrator and collector as seen in Fig. 1 is used as the PCM system. The flat plate collector is applied to heat the heating fluid by passing it in a flowing rate of 0.0013 kg/s into the collector. Water is selected to be the heat transfer fluid that is flowing through the collector to be the heat carrier. The system is used around the solar noon at the place of conducting experiment that is located at 30°58′N and 31°01′E. Core sand-PCM Paraffin composite is inserted in the tube of the heat exchanger. The PCM is subjected to charging/discharging cycles for melting and solidification processes to store the heat in the form of hot water through the discharging cycle. The gained heat is stored in the form of hot water, which is stored in a hot water tank that is well insulated to prevent or reduce the heat losses as possible to their minimal values. The hot water storage insulated container is connected on parallel to the heat exchanger.Fig. 1 Schematic graphical design of the core sand-PCM Paraffin system illustration.

In order to thoroughly discuss the influence of the modified phase change energy storage system and the heat released through the discharging system and stored in the form of hot water, intuitive comparison of such modified PCM with the pristine paraffin wax PCM is supported. The comparison is based on the analysis of effective accumulated temperature in the form of the discharged hot water to analyze the regenerative heat storage and release change. Also from the point of thermal analysis of the material, the charging and discharging temperature release through a time interval of a one minute are recorded and compared to investigate the modified system effect (core sand incorporated paraffin) and also recorded the optimal core-sand material addition. Thereby, the data is represented as a relation between temperatures at various time intervals.

Experimental analysis and material characterization

The incident solar radiation intensity at the time of conducting experiment is monitored using Eppley Black and White solar-meter (type 1 8–48) which is mounted beside the solar collector and the sun rays’ intensity is explored from 9.00 am to 5.00 pm.

In order to thoroughly discuss the influence of the modified phase change energy storage system and the heat released through the discharging system and stored in the form of hot water, intuitive comparison of such modified PCM with the pristine paraffin wax PCM is supported. Also, the inlet and outlet temperatures of the heat transfer fluid (water), ambient temperature, phase change composite substance concentrator in the heat exchanger temperature, the air temperatures inside the flat plate collector and the stored hot water gained for the system temperature, all are investigated using thermocouples. The comparison is based on the analysis of effective accumulated temperature in the form of the discharged hot water to analyze the regenerative heat storage and release change. Also, from the point of thermal analysis of the material, the charging and discharging temperature release through a time interval of a one minute are recorded and compared to investigate the modified system effect (core sand incorporated paraffin) and also recorded the optimal core-sand material addition. Thereby, the data is represented as a relation between temperatures at various time intervals.

The prepared material is characterized through X-ray diffraction (XRD), which is signified by by XRPhillips X’pert (MPD3040) X-ray diffractometer supported by a monochromatic source CuKa (k = 1.5406οA) with step-scan mode of 0.02° mode and characterized in the range of 10°–80°. Also, the morphology of the composite is identified by field-emission scanning electron microscope (SEM) (FE-SEM, Quanta FEG 250) that is augmented with energy-dispersive spectrum (EDX).

Results and discussion

Characterization of composite

XRD

The XRD diffractogram of the core sand material, the paraffin PCM and the core sand/paraffin PCM are investigated and explored in Fig. 2a,b and c, respectively. The crystalline phase of core sand substance is recognized and the XRD pattern displays numerous diffraction peaks. Hematite and quartz crystal structures are recognized in the material diffraction pattern. Figure 2a shows strong broadening peaks from the small crystalline areas of such phases. Therefore, it might be deduced that the silica reinforced iron material comprises of a crystalline silica core augmented hematite shell possess barely precise small crystalline domain. The signified phases of silicon oxide, iron oxide, iron, iron aluminium oxide and iron silicate. Intense peaks of silicon oxide are assigned in the graph since the sand is mainly compromises of silica and that may be the source of those quartz particles. Also, the suspended materials in the iron-based waste are mainly the source of iron and iron oxides that appear as iron oxide, iron and aluminium oxide and iron silicate. Due to the calcination iron augmented with silica and formed iron silicate38,39.Fig. 2 XRD pattern of (a) the prepared core sand composite, (b) paraffin PCM and (c) core sand/paraffin PCM composite.

Also, the crystallization of paraffin wax is investigated through XRD and the data displayed in Fig. 2b. It is clear from the data exhibited in such Figure that paraffin wax has two sharp diffraction peaks at 2θ values of 21.6° and 24.0° that are attributed to the typical diffractions crystal planes of [110] and [200] that signified paraffin wax, respectively41. Furthermore, Fig. 2c is representing the core sand/paraffin PCM composite. The sharp peaks indicate that the composite has a crystalline structure. The XRD pattern of the core sand/paraffin PCM composite shows the same peaks as that of paraffin wax. Also, the other peaks can be observed are for the core sand phase presented in the pristine material. Such results confirm the presence of the iron core sand material with the paraffin wax PCM.

SEM and EDX

Figure 3a,b,c and d illustrates the SEM micrographs images at different magnification of the prepared core sand composite substance to explore its morphology. The SEM micrograph illustrates that mixed shape of the sand particles that is augmented semi-spherical dispersed particles of the iron material on the surface of the core sand.Fig. 3 SEM micrographs of core sand composite at different magnifications (a–d) and EDX analysis (e and f).

Additionally, elemental analysis of the organized core sand composite substance is exposed through the Energy Dispersive X-Ray Analysis (EDX). The data displayed in Fig. 3e and f exposed the composite sample compromises of the dominant elements of O, Si, Al and Fe which conforms their presence in the improvement the PCM system.

Thermal analysis of flat plate collector and the PCM system

As previous studies13,16,40 projected, the city that the study is carried out on is in the North of Egypt, Shebin El-Kowm city, Menoufia governorate, is well gifted with high intensity of renewable solar radiation, thereby such place is signified this geographical collection as a superior candidate for gaining a high implementations of solar-energy systems. The location of the study in the north of Egypt is categorized as one of the predominant and plentiful of solar energy towns in the country of Egypt throughout all the seasons especially in the summer periods. The daylight time is ranged from nine to eleven hours per day at the place of the study. The place is located on the latitude of 30.516. Experimental data from the recorded solar energy intensity of the sun radiation in the city of the study of experiment through the hot months of the season of summer is displayed (Fig. 4) and the recorded highest solar radiation is around the solar noon and recorded 1162 w/m2. Furthermore, the monitored ambient temperature, Ta, is explored and recorded an average value of 35 °C.Fig. 4 Thermal behavior of solar irradiance on the place of study.

The air, PCM, water temperatures are measured using digital processing thermocouples thermometers at six locations. Two measuring points are arranged for the inlet and outlet solar collector as well as the air temperature under the glass cover of the collector that is recorded with extra thermocouple. Ambient air temperature surrounding the collector is taken to represent the air temperature at the place of the study. In addition, one thermocouple thermometer was mounted inside the heat exchanger to monitor the PCM temperature through time intervals. The recording interval is one minute. Hot water collected after the discharging cycle is also observed and its temperature is recorded. Furthermore, the solar meter that records the solar radiation intensity is mounted above the ground in the east-south direction at the open area of the location where the solar collector is mounted using Eppley Black-and-White Pyranometer.

Heat charging/discharging of PCM system

In such part, the results achieved from the current work are examined for the concept of investigating and proposing a proficient TES design. The data investigated are explored in expressions of heat transfer improvement and advancement that attained from melting/solidification cycles. Analysis upgrading by applying the implementation indicator for different proportions of core sand supported PCM systems using various concentrations.

The temperature of charging, Tc, and the corresponding temperature of discharging, Td, for the varied PCM systems are consistence for the melting and solidification cycles are demonstrated and exhibited in Fig. 5a and b, respectively at distinctive time profiles. Different mass segments of core sand/PCM systems are attained by adding various proportions of core sand materials, 0.5, 1.0, 1.5 and 2.0% and labeled as 0.5%-sand core-PCM, 1.0%-sand core-PCM, 1.5%-sand core-PCM and 2.0%-sand core-PCM are embedded for the base organic paraffin wax material to assess the optimal mass addition (%) to the pristine PCM.Fig. 5 Temperature profile of the pure PCM material and embedded PCM with core sand for both (a) charging and (b) discharging cycle.

Notably, as displayed in Fig. 5a, the fraction of sand core embedded into the PCM system explores a diverse range of melting temperatures profile. A thermal enhancement is detected via the supplement of core sand into the wax up to 1.5%. But, extra addition of core sand into the PCM-system retards the temperature elevation. The Tc of the system extended to 71 °C in comparison to 54 °C for the pristine wax. Exceptionally, according to the previous work cited by various researchers in literature24,33,41, the addition of materials into the pristine was PCM supports in a persuade alteration in the profile of the heat flow compared to the pure PCM based wax material. Hence, such change might adapt the significance of the melting temperature of the PCM-phase change wax substance than compromised with core sand. Furthermore, it is projected that the compromised core sand in wax substance improves its latent heat. Moreover, it might be stated that the presence of hematite/silica materials in the phase change substances controls its photodegradation due to it concessions of various components as achieved from EDX examination (Fig. 3e and f), that suggests the representative signals of iron, silica and aluminum materials that are indicated with their photoactivity27,42.

The results of the discharging cycle of the different kinds of pure wax PCM as well as wax augmented with varies quantities of core sand is displayed in Fig. 5b. It is notably from such curves displayed in the figure that elevating the PCM melting temperature, subsequently increases the solidification temperature of its corresponding PCM by 19 °C. However, it is noteworthy to mention that PCM wax embedded with core sand material in comparison to the pristine wax possesses a higher solidification temperature. Also, the temperature variation is dependable on the varied amount of the embedded core sand.

Additionally, according to the results distinguished in Fig. 5b and a remarkable comparative improvement with the core sand amount addition is linked to the increase in the composite-PCM solidification time. Consequently, the heat attained and acquired through the solidification cycle is additionally elevated. The various system enhancements are achieved through the discharging temperatures of corresponding to the 1.5% mass proportions. This might be associated with the existence of the core sand discrete in the host paraffin organic PCM wax that delivering more inorganic sites that enhances the possibility of absorbing heat that is leading to intensification of the latent heat of fusion of the paraffin wax implanted substance.

But, it is significant that extra upsurge in the added material mass portion leading to a decline in the solidification temperature that makes the procedure undesirable. Previous investigators are previously mentioned such results in their PCM system14,22,31,42. This can be demonstrated by the extra supplement of the enhancement materials can decrease the constancy of the PCM rather refining it. In this case the consequence is agglomeration/sedimentation, which might further deduce the PCM effectiveness. Consequently, selecting the optimal enhancers value is vital for charging/discharging system performance to reach to the optimum global system routine. Notably, it is estimated according to the data in Fig. 4b that the discharging time is increased for the 1.5% core sand addition compared to the other proportions and the pristine PCM. Hence, this takes longer time to complete the discharging cycle.

Transient temperature profiles of core sand PCM existing an extra-designated to represent the melting process. Heat transfer is lasted during conduction from the beginning of the heating cycle till the wax temperature ranges the melting temperature. Thereby, the preliminary melting of core-sand Wax-PCM is fashioned via a complex combination of conduction and convection heat transfer together. But, with the processing of the melting system, the temperature elevation is relatively augmented. This might be investigated and explored by the enhancement in natural convection of the melted wax substance. Previous work is reported previously by other workers21,43.

The above-mentioned experimental data suggest that the heat storage density is associated with the quantity of the proportions of core sand embedded into the system and the perfect amount portion is recorded at 1.5 wt%. Previous work is previously published in literature44.

Heat storage capacity

To attain the thermal consistency of the core sand PCM-Wax system, after discharging cycle, both the amount of heat (Qg) and the temperature gained (Tg) are monitored. According to the solar heating fluid, water, heating is being in increment. The optimal import to the phase change wax substance is comparably important concerning the quantity of heat multiplied. The data exhibited in Fig. 6a and b reveals that the augmented core sand wax-PCM might attain an elevated temperature range gained from the PCM that might be stored. The existence of core sand with paraffin wax in an optimized value addition fraction ratio (1.5%) might increase the heat storing temperature. Thereby, the heat stored in comparison to the pure wax is increased. According to the data displayed in Fig. 6b advancement in the heat achieved from the storing process in the preliminary time interval, which is extended only to 2.2 kJ/min for the pristine paraffin wax configuration.Fig. 6 Heat storage profile (a) temperature and (b) heat flow rate during discharging cycle from various PCM.

It is noteworthy to mention that such heat amount is increased to reach 7.4 kJ/min for augmented core-sand PCM system storing heat system. This might be illustrated by the role of hematite and silica, which are mainly compromising the core sand substance, the improving the thermal transfer tendency that is the key reliable of a remarkable prospective in enriching the global energy storage efficacy36.

According to data exhibited in Fig. 6b, base pristine wax-PCM scheme achieves minimal heat rate expanded examined through the attained collected hot working fluid “water” that is in comparison to the embedded core sand into the composite PCM system, which is elevated and increased, with the quantity of inserted substance added till the portion of 1.5% mass fraction. Such investigated might be illustrated by the superior thermal conductivity of the managed hybridized scheme42.

Overall PCM process efficiency

Generally, all the investigated PCM-systems in the present current study, the whole overall heat attained from the systems are calculated and the investigated data are clearly displayed in Fig. 7a. The heat rate gained by the PCM is the heat assigned by the working fluid “water” as the heat transfer carrier substance and is investigated through the following Eq. (1).1 Qυ=w˙CwTw

where w˙˙: mass flow rate of heat transfer fluid (g/s); T: Temperature range between inlet and outlet water entering and leaving the collector ad Cw: Specific heat capacity of the heat transfer fluid (4.18 kJ/kg K).Fig. 7 Overall PCM-system performance (a) comparison of heat gained and (b) overall effectiveness.

As the results displayed in Fig. 7a, the solo paraffin wax PCM system and that inserted system with the core sand filler elucidates the embedded system improves the global heat rate gained from the PCM configuration. The experimental data revealed that the useful rate of heat attained is greater for combination core sand paraffin wax substance (7 kJ/min), which exhibited a noticeable outcome than the heat attained by the pristine paraffin wax (48 kJ/min). Such comparative investigation revealed the noteworthy extra significant pronounced heat rate attained as a result of the enhancement in the heat transfer. This might be attributed by the higher thermal conductivity of the embedded filler in the hybridized PCM mixture, and the rate of heat attained is significant than the solo PCM wax. Moreover, it is important to mention that the heat rate gained could be rises equitably by the upsurge in the core sand weight fraction. Also, throughout the discharging cycle, the overall temperature difference and the quantities of hot water stored are greater. Consequently, the useful heat recorded from the system of the core sand paraffin wax process is higher. Aforementioned examiners in the literature described similar data9,13,36.

Similarly, the global solar energy thermal storing efficacy of such energy storing PCM embedded with the core sand filler system added at different weight mass fractions is investigated and competed as displayed in Fig. 7b. Concerning the amount of the heat gained via the stored water as the heat transfer carrier is calculated from Eq. (1) and the heat gained from the core sand substance that is attained from the relation described in Eq. (2). Thereby, the overall PCM efficacy, Y, can be calculated. Process efficacy is recorded from the calculations according to Eq. (3) that describes the useful energy achieved from the heat transfer fluid to that gained from the PCM45.2 QPCM=mPCMCPCMθPCM+mLf

where, mPCM is the mass of phase change material (Kg), CPCM is the specific heat capacity of PCM (kJ/kg.K), θPCM is consequent to the TPCM, temperature alteration of inlet and outlet temperatures of the heat exchanger involving core sand/Wax phase change material and Lf is the latent heat of fusion of PCM (kJ/kg)46,47.3 Y=QυQPCM×100

It is noticeable from Fig. 7b that the achieved efficacy is enhanced according to the mass fraction of the core sand supplemented to the pure paraffin’s wax-PCM. The highest overall efficacy, 92%, is corresponding to core sand/Wax compromised of 1.5% weight fraction added. Consequently, such data confirms the greatest storing capacity that is equivalent to the added 1.5% core sand of weight proportion embedded into the paraffin organic PCM wax48–50.

Comparative investigation

Numerous paraffin wax-PCM systems enhanced through various system fillers described by different researchers reported in the cited work that are previously published are compared with the current study. The type of system improvement achieved is described in Table 2. Moreover, the maximum temperatures’ recorded for charging PCM are presented in Table 2 to arrange the progress attained from the current investigation. According to the results exhibited, a significant improvement is attained through the core sand supplement enhancers. The temperatures form the current studied PCM-system accordingly is signified as the greatest values. By applying such metals capsulations as the supplement substance exhibited excellent thermal performance in comparison to the pristine paraffin thermal performance. Although, it is noteworthy to notate that a higher achievement is gained from other reported systems than the current core sand systems; the current study is based on waste by-product substances and naturally abundant materials. Thus, such material is signified as an economic pathway advances.Table 2 comparative investigation of solar energy storage performance between the recent studies in literature with the current study.

Filler	%, Additive	Yield	References	
Core sand-hematite	1.5	92% enhancement in the heat gained	Current study	
Aluminium oxide	1.0	85% enhancement in conduction heat of the system and reduction in the melting by 50%	42	
Zinc oxide	2.0	Increase on the temperature of discharging cycle	20	
Zeolite	-	38% enhancement in the melting temperature	45	
Graphite	1.0	enhancement in effective thermal conductivity	25	
Quartz	-	6% enhancement in the discharging cycle capacity	20	
Silicates	3.0	enhancement in latent heat	42	
Titanium dioxide	1.0	0.46% enhancement in phase-change heat	42	
Silicon nitride	10.0	77.4% enhancement in energy storage efficiency	44	
Aluminium nitride	5.0	37% enhancement charging cycle capacity	31	
Carbon nanofiber	0.45	0.45% decline in the temperature	11	
Cupper oxide	10.0	52% enhancement in system proficiency	21	

Conclusion

Core sand supported with hematite from industrial waste particles is prepared and supported paraffin wax. The properties of the core sand material are used to improve the performance of paraffinic PCM. Paraffin wax as base PCM system is applied for latent heat thermal solar energy storage technique. The heat stored through the charging/discharging cycles are assessed for pristine and composite PCM systems. The rate of charging for all composite PCM is better than pristine paraffin where the best charging rate is 80 min. The rate of discharging for all composite PCM is generally better than pristine paraffin where the best discharging rate is 18 min. It can be estimated that the embedded filler PCM based paraffin wax system inserted into a vertical type heat exchanger that is combined with a flat plate collector, possess upsurge thermal performance expressed in its thermal properties. Consequently, core sand dispersed in paraffin wax is an appropriate candidate for latent heat storage substance for further solar heating facility. The highest storing efficiency is corresponding to the addition of 3% core sand into the pristine paraffin’s. The heat attained is enhanced from 7 kJ/min for the solo paraffin wax into 48 kJ/min for the embedded core sand filler into the wax composite when the core sand portion is added in the percent of 1.5% by wt that is signified as the highest efficiency. This system exhibited a good alternative that might be adopted as a cost-efficient alternative. Also, the best operating system condition has been compared to other systems reported in the previous studies, which indicates the promising capabilities of the current study. It is noteworthy to state that excess work is essential to investigate the efficacy on using repeated melting/solidification cycles. However, Cost benefit analysis is required in order to advocate the suitability and sustainability of the material for the real PCM system application.

Acknowledgements

The authors extend their appreciation to Prince Sattam bin Abdulaziz University for funding this research work through the project number (PSAU/2024/01/921606).

Author contributions

Conceptualization, M.A.T.; Methodology, H.A.N. and M.A.T.; Software, H.A.N.; investigation, H.A.N.; Writing—Original Draft, H.A.N. and M.A.T.; Writing—Review and Editing, H.A.N.; Project Administration, H.A.N. All authors reviewed the manuscript.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Competing interests

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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