Numerical analysis of a coupled solar collector latent heat storage unit using various phase change materials for heating the water (original) (raw)
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Journal of Solar Energy Engineering-transactions of The Asme, 2009
The present work investigates, theoretically and experimentally, the thermal performance of a packed bed combined sensible and latent heat storage unit, integrated with the solar water heating system. A one-dimensional porous medium approach with the finite difference technique is used to develop the numerical model to obtain the temperature profiles of both the phase change material (PCM) and heat transfer fluid (HTF), and the molten mass fraction of the PCM at any axial location of the cylindrical storage tank during the charging process. The model also incorporates the effect of the varying fluid inlet temperature to accommodate the actual conditions that prevails in the solar collector. Experimental apparatus utilizing paraffin as PCM, which is filled in high-density polyethylene spherical capsules, is constructed and integrated with a solar flat plate collector to conduct the experiments. The water used as HTF to transfer heat from the solar collector to the storage tank also acts as a sensible heat storage (SHS) material. The results of the numerical model are compared into the experimental results of the temperature profile for various porosities and HTF flow rates. It is found that the results of the numerical model are in good agreement with the experimental results. The performance parameters, such as instantaneous heat stored, cumulative heat stored, and charging rate are also studied in detail.
The present work has been undertaken to study the feasibility of storing solar energy using phase change materials (PCMs) and utilizing this energy to heat water for domestic applications during nighttime. This ensures that hot water is available through out the day. The storage system consists of two simultaneously functioning heat-absorbing units. One of them is a solar water heater and the other a heat storage unit consists of PCM. The solar water heater functions normally and supplies hot water during the day. The storage unit stores the heat in PCM's during the day and supplies hot water during the night and overcast periods. The storage unit utilizes small cylinders made of aluminium filled with paraffin (PCM) as the heat storage medium and integrated with a solar collector to absorb solar energy. The performance of this PCM based thermal energy storage system is compared with conventional sensible heat storage system and the conclusions drawn from them are presented.
Journal of energy storage, 2020
In this work, a new design of shell and finned tube latent heat storage system was designed, constructed and tested when it was integrated with the flat plate solar water heater. This design not only provides large heat transfer area between the storage material and the heat transfer fluid, but also it overcomes the problem of low thermal conductivity of paraffin wax (PW) by dividing it into tens of thin slices. Three configurations of storage techniques were proposed; where water, PW as phase change material (PCM) and both water and PW were used as thermal storage materials. The proposed systems were tested at different mass flow rates of heat transfer fluid (0.08-0.16 kg/s). The experimental results showed that the highest daily efficiency of 65% was achieved when the configuration that combines the PCM and water storage tank was used. Moreover, this configuration was capable of providing hot water of temperature ranging from 50 to 60.4°C through 24 h/day. The results of this configuration showed also that the released energy from PW constitutes 52% of the total stored energy; while the remaining energy of 48% was considered backup stored energy that may help in any sudden thermal loads during night.
Journal of Contemporary Urban Affairs, 2017
An exergy analysis has been performed to determine the potential for useful work in a latent heat storage system with phase change material (PCM) for a flat-plate solar collector. Commercial paraffin wax is used as PCM to store and release energy in the solid-liquid transformation; this material is located in metal containers under the absorber plate on the bottom insulation of the collector. The exergy analysis is performed in outdoor conditions for days of low, medium and high radiation taken from October 2016 to March 2017 at Barranquilla city (latitude: 10º 59' 16" N, longitude: 74º 47' 20" O, Colombia). The system is evaluated throughout charge and discharge periods. The energy and exergy balance equations based on the first and second law of thermodynamics is formulated and solved for each element of the collector system as well as for the PCM. Results obtained show the energy distribution and energetic destruction for each system component and its variation as a time function. It was observed that the average energy and energetic efficiency are 28.7 %, 13.2 % for of low radiation days. 26.9%, 20.56% for of medium radiation days, and 23.2%, 18.6% for of high radiation days, respectively. Results of the analysis are shown in detail in the present paper.
Solar Energy, 1998
The cylindrical latent heat storage tanks considered here are part of a domestic heating system. In this study, the performances of such energy storage tanks are optimized theoretically. Two different models describing the diurnal transient behaviour of the phase change unit were used. The first is suited to tanks where the phase change material (PCM ) is packed in cylinders and the heat transfer fluid (HTF ) flows parallel to it (mode 1). The second is suited to tanks where pipes containing the fluid are embedded in the PCM (mode 2). The problem (treated as two-dimensional ) is tackled with an enthalpy-based method coupled to the convective heat transfer from the HTF. A series of numerical tests are then undertaken to assess the effects of various PCMs, cylinder radii, pipe radii, total PCM volume in the tank, mass flow rates of fluid, and inlet temperatures of the HTF on the storing time. In addition, optimal geometric design of the store depending on these parameters and PCMs is presented. © 1997 Elsevier Science Ltd.
international journal of chemical sciences, 2016
The energy storage leads to saving premium fuels and makes the system more cost effective by reducing the wastage of energy. Solar is being a renewable energy, which is used to store heat in the storage tank and PCM encapsulated copper tubes are kept inside the storage tank called PCM storage tank. Thealmost 90 copper tubes is used and phase change materials are filled in each tube. The varieties of PCM materials are analyzed, and suitable material is to be selected for thermal storage system. Copper tube encapsulated with paraffin wax (PCM) is going to be designed and fabricated to store the heat energy in PCM storage tank. Large quantity of solar thermal energy is absorbed in the day time. During charging process heat can be stored in copper tube as latent heat, the same heat can be stored during discharging process by applying cold water. The PCM used is intended to enhance the heat storage capacity of the conventional solar tanks used in domestic solar heaters and to measure inl...
Experimental Analysis of Solar Water Heating System using Phase Change Material
International Journal For Reseacrh In Applied Science And Engineering Technology, 2020
Energy one of the basic need of human being for existence. It plays important role in development and progress. The main source of energy is fossil fuels but sources are depleting now days. So we are forced to move on to another renewable energy sources like sun, wind, tidal etc. India is also investing heavy amount of money into non-renewable energy sources. Considering about the solar energy it can be utilise in two ways either converting it into electrical energy using solar cell or use as a thermal energy. The second method is being use form ancient time for house hold purpose like drying food, cloths etc. in U.S. the use of solar water heater is dated back to 1900. Solar energy apparatus which we use need a efficient and proper thermal storage unit. Therefore, it largely depends on the method and apparatus which we will use to store thermal energy. The property of latent (PCM) should be such that it can store large amount of latent heat while changing its phase and also release the heat during night time. It is obvious that any energy storage systems incorporating PCM will comprise significantly smaller volume when compared to other materials storing only sensible heat. A further advantage of latent heat storage is that heat storage and delivery normally occur over a fairly narrow temperature range the phase change temperature. Solar water heater is one of the most popular methods to utilise the solar energy. Solar water heater accounts for 80% of the solar thermal market. But the limitation of solar thermal energy is that we can only use it in day time. So to overcome this limitation we can use the solar heating setup with additional setup of PCM (Phase Change material). The property of PCM is that is changes its phase during heat addition and store the heat in the form of latent heat and when temperature decreases it again changes the phase and release the heat energy. In this research we will analyse that this method is how much efficient. The following paper deals with the experimental investigation of effectiveness of a parabolic collector and its results have been verified experimentally.
Experimental and numerical study of a solar collector using phase change material as heat storage
Journal of Energy Storage, 2020
The present work present numerical and experimental investigations to study the performance of a small-scale parabolic trough solar concentrator integrated with thermal energy storage system. A new design of receiver which uses the phase change material to store the thermal energy is built. A parabolic-trough solar concentrator was proposed and constructed using a concentric absorber tube with phase change material. The absorber is considered as a temporary thermal heat storage component. The heat storage-recovery mechanism will act as a thermal compensator that allows the parabolic trough solar concentrator to stabilizing energy output during the absence of intense radiation or for short time cloudy conditions. The PCM used a binary salt composed of a mixture of 60% NaNO 3 and 40% KNO 3 , filling the annular space of the absorber tube. Solar energy is converted to heat, stored in the phase change material and is discharged to cold water, which is the final heat transfer fluid in the inner pipe of the receiver. The simultaneous testing of the receiver with and without phase change material is investigated. A commercial computational fluid dynamics model of the whole system is presented and numerical results are compared to experimental results, which were conducted with and without phase change material in the receiver tube. The maximum outlet water temperature achieved using phase change material in the receiver tube is about 16.80% and 14.86% higher than the simple tube for 21 July and 21 October respectively. The daily thermal efficiency of the parabolic trough solar concentrator increases by 6.56% and 8.32 respectively for a both days using a receiver with a phase change material concentric tube. The phase change material showed good heat retention of 2 h to 1 h 40 min for water inlet temperature 30°C and 40°C respectively.
Desalination, 2017
In this study, a novel idea of storing the latent heat of condensing vapor in solar stills by means of phase change materials (PCMs) as a thermal storage is experimentally investigated. During the daytime, the generated water vapor by the solar energy, is conducted to an external condenser filled with PCM to be condensed. The wasted latent heat is absorbed by PCM and thereby stored. It is worth noting that there is no direct contact between the saline water and the PCM, therefore, the solar energy is not directly stored in the PCM. In the evening, the energy stored in the PCM is transferred as heat to the saline water by heat pipes and enables the desalination process to continue. Several tests were run to investigate the performance of the system. The results revealed that the presence of an external condenser filled with PCM and equipped with heat pipes in a solar still with evacuated tube collectors, makes the desalination process continue after the sunset without causing a decrease in the yield during the daytime. The yield increases by 86% as compared to the yield of the system without PCM and reaches to 6.555 kg/m 2 day with the efficiency of 50%.
Investigation of Solar Water Heating System with Phase Change Materials
International journal of engineering research and technology, 2018
Thermal energy storage has always been one of the most critical components in residential solar water heating applications. Solar radiation is a time-dependent energy source with an intermittent character. The heating demands of a residential house are also time dependent. However, the energy source and the demands of a house (or building), in general, do not match each other, especially in solar water heating applications. The peak solar radiation occurs near noon, but the peak heating demand is in the late evening or early morning when solar radiation is not available. Thermal energy storage provides a reservoir of energy to adjust this mismatch and to meet the energy needs at all times. It is used as a bridge to cross the gap between the energy source, the sun, the application and the building. So, thermal energy storage is essential in the solar heating system. Therefore, in this paper, an attempt has been taken to summarize the investigation of the solar water heating system in...