Analysis of Solar Water Heater with Modification Absorber Plate Integrated Thermal Storage

In various countries worldwide, solar water heater systems (SWHs) are utilized as devices that harness solar energy as a primary energy source. This study investigates the performance of SWHs numerical simulation by integrating phase change material (PCM) paraffin wax onto an absorber plate collector at the bottom for thermal storage. This study presents the thermal performance of a SWHs that uses an absorber plate with PCM for thermal energy storage. In this test, four variations of the model tested, namely a) standard flat plate (SFP), b) standard flat plate with PCM storage thickness 10mm (SFP+PCM 10mm), c) standard flat plate with PCM storage thickness 7mm (SFP+PCM 7mm), and d) standard flat plate with PCM storage thickness 4mm (SFP+PCM 4mm), were investigated using numerical simulation. Initially, an analytical investigation was conducted to examine the material qualities of paraffin wax utilised for phase change material (PCM) storage. The SWH systems were subsequently imported and simulated under three different levels of continuous solar radiation: 400 W/m2 700 W/m2 and 1000 W/m2. The simulation incorporates the use of computational fluid dynamics (CFD) tools. The results of the study revealed that the collector of the SWH system, which utilised an absorber plate containing phase change material (PCM) storage, demonstrated exceptional performance. Models with a thickness of 7mm PCM or SFP+PCM 7mm have the highest efficiency compared to other models with an efficiency value of 64%. There is a 3-4% increase in efficiency with variations in models that use PCM thermal storage compared to models that do not use PCM thermal storage.


Introduction
In various countries worldwide, solar water heater systems (SWHs) are utilised as devices that harness solar energy as a primary energy source.Nevertheless, due to the presence of several limitations in traditional solar water heaters, extensive study has been undertaken.The aforementioned study constituted an empirical inquiry into a solar water heating system employing a V-shaped absorber panel.At low discharge (0.5 L/min) and high release (2 L/min), two solar water heating systems were constructed and assessed.The findings of the study indicate that the solar water heating system incorporating a V-shaped absorber plate exhibited a performance improvement of 3.6 -4.4% compared to the system utilising a flat absorber plate.[1].
On the other hand, the high temperature on the surface of the V-shaped plate generates a significant heat loss on the collector's surface, necessitating heat energy storage that can maximize the solar collector's efficiency.Pisut Thantong [2] conducted experimental performance studies on solar phase change material (PCM) in tropical settings and described his findings.Empirical evidence has demonstrated that collectors incorporating phase change material (PCM) exhibit enhanced efficiency in reducing heat accumulation and conserving energy.In a study undertaken by Palacio [3], a comparative experimental investigation was carried out to compare conventional flat plate solar collectors with identical prototypes of phase change material (PCM) thermal storage.The results suggest that the efficient performance of solar collectors, as compared to solar plate collectors, is significantly influenced by the choice of phase change material (PCM) and the level of conduction contact between the absorber and PCM.Conventional flat.Kee [4] has recently researched and analyzed the usage of PCM polymer/porous material compositions for heat storage.Saddegh [5] also investigated the thermal properties of vertical and horizontal shell-and-tube energy storage devices that employ phase change material (PCM).The experiment undertaken by Shalaby [6] involved the utilisation of a solar water heater that incorporated a latent heat storage device including a shell and finned-tube.The results suggest that the most effective daily efficiency of 65% is attained by employing a setup that combines a phase change material (PCM) and a water storage tank.
The concept of the thermosyphon is also employed in contemporary solar water heating technology.The solar heating system was investigated by Ka-Kui Tse [7] using a series of tests and simulations.Implementing additional physical design optimisation approaches can enhance the overall efficiency of the solar water heating system, as indicated by the outcomes of this study.In the interim, the comparative analysis of data obtained from both mathematical and experimental approaches reveals that the highest recorded temperature of hot water is observed at 16.00, 65.25 0 C, 71.19 0 C, and 69.46 0 C, respectively [8].The research undertaken by Garnier [9] utilised computational fluid dynamics (CFD) methods to examine the internal flow and heat transport arrangements within the collector.Empirical testing was conducted to compare the performance of the collector with that of a previously designed prototype.Badiei and Eslami [10] investigated the modelling of solar water heating using a flat plate collector embedded into the phase change material (PCM) layers.The temperature distribution in Shiraz, Iran was examined on two distinct days, namely summer and winter.The findings indicate that the PCM system exhibits a reduced exit temperature during the early hours, while it can provide hot water for an extended period during the night when utilised.
As a result, it is critical to design solar water heater (SWH) using numerical simulation and computational fluid dynamic (CFD) analysis, and then compare it to experimental testing before delivering a product prototype.This study employs numerical modelling to investigate the integration of a solar water heater with phase change material (PCM) storage as a thermal energy storage (TES) system, as well as a thermosyphon system.A total of four modelling solid-water heat transfer (SWH) systems were simulated, each consisting of two distinct heat collectors: an absorber plate with and without phase change material (PCM) storage.Additionally, three alternative PCM thicknesses, specifically 10mm, 7mm, and 4mm, were included in the simulations.

Solar Water Heater Collector with Pcm Thermal Storage and Its Performance
Energy can be stored in various forms, including sensible heat, latent heat, and chemical energy products.The recuperated energy is utilised for the twin purposes of thermal energy transfer, hence ensuring the maintenance of a stable temperature inside a fluid.Currently, the main emphasis of research on heat storage materials is on studying sensible heat and latent heat [11].The concept of latent heat pertains to the occurrence when a substance experiences a modification in its temperature due to the transmission of heat between the entity and its immediate surroundings.In a certain scenario, the heat transfer does not result in any alteration to the temperature.This phenomenon arises when the material experiences a transition in its phase.As an illustration, a solid undergoes decomposition into a liquid (melts), the liquid transforms into vapour (boils), and alterations occur in the crystal structure (solid).The energy necessary for a certain process is commonly referred to as the heat of transformation, or alternatively, the heat of transformation.The amount of heat necessary to induce a phase transition in a material with a mass of m is: [12]: Q represents the latent heat of the material (J), m represents the mass of the substance (kg), and Le is the specific latent heat capacity (J/kg).

Figure 1. SWH with PCM
Selection of suitable PCM for solar water heaters is an essential method to be carried out in research on SWH, especially for thermosiphon systems.This statement is in line with the results of previous research, namely the integration of paraffin wax and air as heat storage materials that have been carried out experimentally on a thermosiphon type solar water heater where the use of PCM was developed that the heat exchanger is quite effective so that it provides thermal benefits [13].
The energy balance of a solar collector plays a crucial role in determining its steady-state performance.This balance demonstrates how incident solar energy is distributed among useful energy gain, thermal losses, and optical losses.The disparity between the absorbed solar radiation and the thermal loss serves as an indicator of the extent to which an area collector (  ) can generate usable energy [14]: Equation ( 3) is utilised to estimate the usable energy by including temperature measurement data from the incoming and outflow water of the collector,   [14].
The variables representing the mass flow rate (kg/s), specific heat (kJ/kg.K), temperature of the fluid departing the collector ( o C), and temperature of the fluid entering the collector ( o C) are denoted as m, To, and Ti, respectively.
The efficiency of the collector is determined by dividing the useable gain during a specific time frame by the incident solar energy over that same time frame [15].
I T is the solar intensity (W/m 2 ), and A  is the collector surface area (m 2 ).

Experimental Study
The study was carried out in the Renewable Energy Laboratory, situated under the Department of Mechanical Engineering, as part of the Faculty of Engineering at Hasanuddin University (5°13'50.8"S119°30'05.5"E).A PC with Windows 10 Pro 64-bit operating system, a CPU core i7-7700, and 32 GB of RAM memory is used to conduct the numerical simulation.The present computer possesses the capability to execute computational fluid dynamics (CFD) software and geometric modelling software, namely ANSYS Fluent and Autodesk Fusion 360.The simulation method illustrated in Figure 2 utilises an absorber plate, both with and without phase change material (PCM) modelling, to produce water introduction and sustain consistent radiation variations of 400 W/m 2 , 700 W/m 2 , and 1000 W/m 2 .The simulation will yield contour variations that facilitate the identification of temperature disparities between the intake and exit, as well as between the absorber plate, phase change material (PCM), and water within the pipe.Model absorber plate with PCM The simulation runout-based project schematic of fluid flow (fluent) is often conducted using ANSYS Fluent.Each step in the simulation is appropriately labelled with the corresponding sign upon completion.The first stage of the simulation involves the creation or importation of the geometry from an external drawing software, under the assumption that the file format of the geometry is compatible with ANSYS Fluent software, namely in the.iges or.step file format [16].The next phase in the simulation is meshing the geometry; in this step, the total number of elements must be less than 512000 cells due to ANSYS Student software's fluid physics issue size limit [17].Hence, the simulated SWH system must comprise a singular sequence, specifically a conduit, an absorber plate with or without phase change material (PCM), and the movement of water via the conduit.This is done to minimize a total cell of elements while maintaining simulation accuracy because one series is deemed to be typical of others..The simulation test kit comprises two form models that exhibit differences in absorber plate configurations for SWH collectors.These variations include: a) absorber plates without phase change material (PCM) storage, and b) absorber plates with PCM storage, as depicted in Figure 2. The system also includes three distinct kinds of SWH collectors with varying thicknesses of PCM storage, specifically 10mm, 7mm, and 4mm, as depicted in figure 3 (a, b, and c).

Results And Discussion
This research was conducted using a simulation method.The collector plate used in the test is a flat collector plate that has been integrated with PCM thermal storage.Then it was compared with a flat collector plate without adding thermal storage with the same treatment.The study involves conducting simulation tests on two-shape model SWH collectors with and without phase change material (PCM) storage.Additionally, three-shape model SWH collectors are examined, incorporating an absorber plate with varying PCM storage thickness.These experiments are performed while both collectors are operating concurrently.In this investigation, simulations provided continuous direct sun radiation at 400, 700, and 1000 W/m 2 .
The simulation study's results can be accessed via contours, which represent temperature differences.Figure 4 displays temperature contours for the absorber plate with and without phase change material (PCM) storage (a), as well as temperature contours for water in the pipe on the absorber plate with and without PCM storage of 7mm thickness (b).  5 shows the temperature absorbed by the SFP and SFP+PCM absorber plates throughout each test.Three variations of radiation intensity were used during the simulation, namely 400 W/m 2 , 700 W/m 2 , and 1000 W/m 2 .In the test with an intensity of 400 W/m 2 , it can be seen that the SFP+PCM 4mm model is 2-4 0 C higher than other models.Meanwhile, the trend for the test with an intensity of 700 W/m 2 is almost the same as the test of 400 W/m 2 .Meanwhile, the radiation intensity of 1000 W/m 2 for SFP+PCM 7mm seems to increase even more with a temperature difference of about 8 0 C from the SFP+PCM 10mm model.This shows that the use of paraffin-wax PCM thermal storage with a size of 7mm can increase the thermal absorption of the plate compared to the SFP model without PCM.For PCM thicknesses of 4mm and 10mm, it can be seen that the thermal absorption that occurs on the absorber plate is lower than that of SFP+PCM 7mm.This happens because the thickness of the PCM in thermal storage significantly affects the thermal absorption of the absorber plate.A large PCM volume can be a high loss for the absorber plate, while a small PCM volume may not be optimal for absorption.6 presents a graphical representation that compares the temperatures at the entrance and departure of each data collection, while maintaining a constant flow rate of 0.0026 m/s.A constant inlet temperature of 40°C is maintained for each adjustment.Hence, drawing from the data depicted in Figure 6, it is evident that the data outlets connecting SFP and SFP+PCM 7mm exhibit a high degree of similarity across various intensity variations.In the context of intensity variations of 400 W/m 2 , 700 W/m 2 , and 1000 W/m 2 , it can be observed that the SFP+PCM 4mm and SFP+PCM 10mm data exhibit a high degree of similarity.Thus, it is evident that the maximum temperature is reached by SFP+TES 4mm when the radiation intensity is 1000W/m 2 , resulting in a temperature of around 47.0°C.

Collector Efficiency
Collector efficiency was used to assess SWH system performance.The collector efficiency of an absorber plate-based SWH system with and without PCM storage is displayed in Figure 7.As solar radiation increases, so does the collector efficiency.At 400 W/m2 low solar radiation, the SFP+PCM 4mm variation has the highest collector efficiency of about 54%.Likewise, the intensity variation of 700 W/m2 for 4 mm SFP+PCM is slightly higher than that for 7 mm SFP+PCM.Meanwhile, for variations in the solar intensity of 1000 W/m2, models with a thickness of 7 mm PCM or SFP+PCM 7 mm have the highest efficiency compared to other models with an efficiency value of 64%.According to the results, there is a 3-4% increase in efficiency with variations in models that use PCM thermal storage compared to models that do not use PCM thermal storage.It has been demonstrated that adding paraffin-wax material to PCM thermal storage increases the collector plate's efficiency.

Conclusion
The efficiency of the SWH system collector was investigated by researchers through the utilisation of an absorber plate without phase change material (PCM) storage, as well as various PCM thicknesses on an absorber plate with PCM storage.The absorber plate with a 7mm thickness of PCM (SFP+PCM 7mm) demonstrated greater efficiency when compared to the absorber plate without PCM storage (SFP) and various PCM thicknesses at the absorber plate with PCM storage.The simulation investigation utilised an absorber plate with and without phase change material (PCM) storage of varying thicknesses.
Numerical simulations were conducted on three form models of SWH collectors, each with varying thicknesses of PCM storage (10mm, 7mm, and 4mm).Additionally, two shape models of SWH collectors were examined, one featuring an absorber plate with PCM storage and the other without PCM storage.The findings of the study revealed that the SWH system collector, which utilises an absorber plate with phase change material (PCM) storage, exhibited superior performance.variants with a thickness of 7 mm PCM or SFP+PCM 7 mm outperform other variants, with an efficiency value of 64%.For all variations in intensity radiation, models that employ PCM thermal storage outperform those that do not use PCM thermal storage by 3-4%.

Figure 2 .
The numerical simulation schematic, (a) Model absorber plate without PCM and (b)

Figure 3 .
Shape model of variations PCM storage thickness (a) 10mm, (b) 7mm, and (c) 4mm In this test there are 4 variations of the model tested, i.e. a) standard flat plate (SFP), b) standard flat plate with PCM storage thickness 10mm (SFP+PCM 10mm), c) standard flat plate with PCM storage thickness 7mm (SFP+PCM 4mm), and d) standard flat plate with PCM storage thickness 4mm (SFP+PCM 4mm).

Figure 5 .
Figure 5. Absorber plate temperature 4.2.Inlet And Outlet Water Temperature Figure6presents a graphical representation that compares the temperatures at the entrance and departure of each data collection, while maintaining a constant flow rate of 0.0026 m/s.A constant inlet temperature of 40°C is maintained for each adjustment.Hence, drawing from the data depicted in Figure6, it is evident that the data outlets connecting SFP and SFP+PCM 7mm exhibit a high degree of similarity across various intensity variations.In the context of intensity variations of 400 W/m 2 , 700 W/m 2 , and 1000 W/m 2 , it can be observed that the SFP+PCM 4mm and SFP+PCM 10mm data exhibit a high degree of similarity.Thus, it is evident that the maximum temperature is reached by SFP+TES 4mm when the radiation intensity is 1000W/m 2 , resulting in a temperature of around 47.0°C.

Figure 6 .
Figure 6.Inlet and outlet temperature