Study of Paraffin wax as a phase change material for heating and cooling load
Vandan Zendekar, Sagar Sonawale, Ashwini Dhadge, Nikita Takawane
Mechanical Department, Savitri Bai Phule Pune University 1186/A, Off J.M. Road Shivaji Nagar, Pune-05, India.
*Corresponding Author E-mail: vandanzendekar@gmail.com, sagarsonawale2@gmail.com, dhadgeash2@gmail.com, takawane.niki6@gmail.com
Abstract:
A significant amount of amount of heat is wasted in electricity general, manufacturing, chemical and industrial process. Phase change material are utilized in different engineering field such as thermal storage building structures, heating and cooling systems, electronics products, drying technologies, refrigeration and cold storage. Paraffin wax (Melting Point 54C) is used as storage media due to its low cost and large-scale availability in Indian Markets. The further experimental study will show the flexibility of using paraffin wax PCMs as a storage medium in heat recovery system. This is because paraffin wax maintains its properties even after thousands of charging and discharging (melting and solidification of paraffin wax) cycles. In this paper, a heat exchanger will be designed for low temperature heat transfer fluid using paraffin wax as a phase change material. Experiments will be performed for different mass flow rates and temperature of heat transfer fluids. The effect of same on the performance of system is to be studied.
KEYWORDS: Phase change material, Paraffin wax, charging, discharging.
Various renewable energy sources are used all over the world due to rising prices of fuel and increase in the level of the green house emission. Engineers and Scientist all over the world are concentrating on renewable energy sources but most important is to store the energy for later purpose when direct energy is not available. The use of Phase Change Material for storing thermal energy is unique way of storing thermal energy, as pcm have high energy storage density and isothermal nature of process.
Due to the increasing gap between the global energy supply and demand, reaching to a thermally efficient and cost optimized thermal energy storage system has received a considerable attention among researchers. There are three methods for storing thermal energy: sensible, latent and thermal– chemical. Among these methods, latent heat thermal storage (LHTS) using phase change materials (PCMs) is known as the most favourable for its high energy storage density with small temperature variation (Mehling and Cabeza, 2007). In other words, PCMs are attractive as they are capable of absorbing and releasing a considerable amount of energy at a nearly constant temperature during melting and solidification processes. Latent heat energy storage systems can be used to store a considerable amount of available thermal energy to be utilized during energy demand period, hereafter providing a promising solution for smoothing the discrepancy between energy supply and demand.
Fins, or more generally extended surfaces, are used to provide additional heat transfer surface in thermal systems. In LHTS systems, various researchers extensively studied the role of different configurations of fins on the performance improvement characteristics of LHTS systems. Subsequently, different numerical studies looking at the impact of fins on overall PCM melting and solidification can be found in literature, (Ogoh and Groulx, 2012; Seeniraj and Narasimhan, 2008; Shatikian et al., 2005); typically, those studies still neglect natural convection in the liquid PCM phase. Although the cited numerical studies provide the tool to determine optimum fins geometry and LHTS configuration; the defect in natural convection simulations brings about the need to perform experimental studies
In Latent Heat storage system (LHT), energy is stored during melting and recovered during solidification of a phase change material (pcm). (Constantin Luca1, 2015) Heat input into the PCM changes its phase from solid to liquid by storing the heat as latent heat of fusion. When stored heat is recovered from a working fluid, the material will change again its phase from liquid to solid. In low temperatures domain, paraffin wax is a good heat storage material. Paraffin Wax is chemical stabile, non- corrosive and have a high latent heat.
The Objective are:
· To plot solidification and liquification characteristic curve of paraffin wax with respect to time.
· To measure various temperatures and calculate the heat transfer coefficient, of designed PCM heat exchanger.
· To analyse behaviour of paraffin wax as Phase change material.
II. LITERATURE REVIEW:
P Vinod Kumar Naidu et al (2018), Study focused on an efficient thermal storage system by using paraffin wax as PCM. Experimentation results show that paraffin wax requires 3 hours for charging and 15 hours for discharging. In order to improve performance of paraffin wax suitable amount of Nano particles can be added.
S. Senthilkumar et al (2016), The experimental results of the paper shows the feasibility of using PCM as a storage media in heat recovery systems. Experiment with flow rate 0.003kg/s gives better efficiency than with 0.001kg/s flow rate.
Daniel Dragomir Stanciu et al (2015), This paper focus on the melting point of paraffin wax. Paraffin wax melts at 42 deg Celsius and ends at 55 deg Celsius. Density decreases in the transition from the solid to the liquid phase.
Vahit Saydam et al (2019), In this paper, a prototype PCM heat exchanger with a helical coil tube is designed, fabricated, and experimentally analyzed for its thermal storage performance under different operational conditions. Paraffin wax is used as PCM and Ethylene glycol (EG)-water mixture is used as heat transfer fluid (HTF). Different HTF inlet temperatures, flow direction, and flowrates were tested to find out the effects of these parameters on the performance, including charging and discharging time, of the thermal storage unit.
S. Bakhshipour et al (2017), In this study, numerical simulation of refrigeration cycle incorporated with a PCM heat exchanger is carried out and also the refrigeration cycle without PCM has been simulated and then the performances coefficients of the refrigeration in either with and without PCM are evaluated. The PCM heat exchanger is located in refrigeration cycle at location after condenser and before the expansion valve. The utilized PCM is n-octadecane with fusion temperature of 27.5 degree Celsius. The stimulation of heat exchanger iS based on CFD. Stimulation results shows 9.58% increase in performance coefficient of refrigerator.
III. PARAFFIN WAX:
Paraffin wax (or petroleum wax) is a soft colourless solid, derived from petroleum, coal or shale oil, that consists of a mixture of hydrocarbon molecules containing between twenty and forty carbon atoms. Paraffin wax was first created by Carl Reichenbach in Germany in 1830 and marked a major advancement in candle making technology, as it burned more cleanly and reliably than tallow candles and was cheaper to produce. In chemistry, paraffin is used synonymously with alkane, indicating hydrocarbons with the general Chemical formula CnH2n+2.
It is solid at room temperature and begins to melt above approximately 37°C (99 °F), and its boiling point is above 370°C (698°F). Common applications for paraffin wax include lubrication, electrical insulation, and candles; dyed paraffin wax can be made into crayons. It is distinct from kerosene and other petroleum products that are sometimes called paraffin.
A. Properties of Paraffin Wax:
· Melting point (degree Celsius) 48.51
· Latent heat (KJ/kg) 210
· Solid Density (kg/m3) 860-900
· Liquid Density (kg/m3) 760-800
· Specific Heat (KJ/kg deg Celsius) 2.9(Solid) /2.1(Liquid)
· Thermal Conductivity (W/m deg Celsius) 0.24
· Viscosity (kg/m s) 0.15-0.205 eral formula CnH2n+2
Fig. 1 Functions of Paraffin Wax [10]
During phase change, remarkable thermal effects come into being dominantly associated with latent heat which can be stored, employed or transferred. Based on solid-liquid latent heat storage, paraffin waxes are the promising candidates in confining the temperature of photovoltaics and batteries, maintaining the temperature of buildings, as well as providing the thermal protection to cherry tomatoes, liquid food products and drugs, and so.
IV. EXPERIMENT SETUP
Fig. 2 Circuit Diagram
Experimental research aims to analyse the heat transfer from the energy storage medium, the paraffin wax, to the water, which recovers heat from the storage medium. Heaters are installed to supply the heat required for the wax to store heat by changing the state of aggregation of the solid phase in the liquid phase. The heat accumulated in the paraffin wax is used for heating water which flows through the coil. The coil is made of copper tube with an interior diameter 9 mm. For measuring the temperature of paraffin wax were used three calibrated thermocouples.
Fig. 3 CAD Model Diagram
Paraffin wax melting process begins at a temperature of 42°C and ends around 55°C. Density decreases in the transition from the solid phase to the liquid phase. It can be seen that between 42°C and 55°C the slope is less. (Constantin luca1, 2015) Phase change is done in a temperature range because paraffin wax changes is not a pure substance, it is generally a combination of various hydrocarbons.
Fig. 4 Paraffin Wax temperature in heating process.[3]
Fig. 5 Paraffin Wax in discharging process.[3]
It can be seen that between 80°C and 55°C, when the wax transfers its sensible heat, temperature decrease is faster. Between 55°C and 45° the paraffin wax transfers its latent heat and the rate of temperature decrease is smaller.
Fig. 6 Outlet Water Temperature[3]
Fig. 7 Heat Transfer Coefficient [3]
Heat exchange coefficient decreases over time due to solid wax deposition on the surface of water coil.
Paraffin wax is good PCM for energy storage in latent heat storage system. Charging and discharging processes were studied by varying the HTF flowrate, HTF inlet temperature and flow direction of the HTF. Temperature readings and images of the PCM revealed details of the phase change behaviors in the coil type PCM heat exchanger. Discharging processes were much longer than charging processes since only conduction exists as a main mode of heat transfer. Experiments have shown that the melting of paraffin wax is irregular in the volume. In order to improve the performance of the Paraffin wax by adding suitable amount of micro or nano particles in to it, the care should be taken that the micro and nano particles disperse homogenously throughout the sample otherwise the micro or nano particle settle at the bottom during the experimentation.
VI. ACKNOWLEDGMENT:
I take this opportunity to thank to all those who have contributed in successful completion of this paper, I would like to express my sincere thanks to our guide Prof. S R Dhavale who have encourage us to work on this topic and valuable guidance whenever required we also extend our gratitude to Prof. S Y Bhosale (HOD) Mechanical department. Who has provided to explore the subject to more enthusiasm I express my immense pleasure and thankful ness to all the teachers and staff of the department mechanical engineering, PES’s Modern college, Pune for there cooperation and support.
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Received on 08.06.2020 Modified on 23.06.2020 Accepted on 11.07.2020 ©AandV Publications All right reserved Research J. Science and Tech. 2020; 12(3):177-182. DOI: 10.5958/2349-2988.2020.00024.8 |
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