İsmail Gürkan Demirkıran

Bio: İsmail Gürkan Demirkıran is an academic researcher from İzmir Institute of Technology. The author has contributed to research in topics: Thermal energy storage & Phase-change material. The author has an hindex of 1, co-authored 1 publications receiving 2 citations.

Emergence of rectangular shell shape in thermal energy storage applications: Fitting melted phase changing material in a fixed space

Abstract: Here we document the effect of heat transfer fluid (HTF) tube position and shell shape on the melting time and sensible energy requirement for melting a phase change material (PCM) in a multitube latent heat thermal energy storage (LHTES) application. Tube location and shell shape are essential as the shape of the melted region, i.e. similar to the boundary layer, affects convective heat transfer performance. HTF tube total area is fixed in all cases to have the same amount of PCM. In order to eliminate the effect of heat transfer surface area variation, results of two- and four-tube configurations were compared within themselves. Liquid fraction, sensible enthalpy content, and latent/sensible enthalpy ratio relative to time were documented for two and four HTF configurations in various shell shape and tube locations. Results show that eccentric two tubes with rectangular shell decreases melting time and sensible energy requirement from 67 min to 32 min and from 161.8 kJ/kg to 136.3 kJ/kg for 72.3% liquid fraction, respectively, in comparison to the concentric tubes with the circular shell. When the number of HTF tubes increases to four, then the required melting time and sensible energy decrease 80% and 3.8%, respectively, for PCM to melt completely as the concentric tubes and circular shell is replaced with eccentric tubes and rectangular shell. Results of liquid fraction variation relative to time show that S-curve of melting becomes steeper if PCM distribution is such that the intersection of melted regions is delayed. Therefore, melted PCM regions could be packed into a shell that minimizes melting time and required sensible energy. Even rectangular shell shape increases the heat transfer surface (increased heat loss rate) because melting time has decreased greatly, total energy lost to the ambient from the surfaces of shell decreases. Eccentricity slows down the solidification process but due to increased heat loss rate from the surface, rectangular shell enables faster solidification than circular shell shape. There is a trade off in between solidification time and heat loss energy for rectangular channels which can be optimized by selecting proper insulation thickness. Overall, the results show that without any thermal conductivity enhancement (TCE) method, melting performance and latent heat storage capability can be significantly enhanced as decreasing the sensible heat storage by fitting the melted PCM regions into a fixed space for the applications where charging speed is lot faster than discharging.

Computation time reduction of PCM melting process by changing modeling parameters

Abstract: Abstract This study can be considered as a helpful reference for whom endeavor to boost the computation efficiency of the PCM melting process. Researchers sacrifice accuracy to decrease computation time since computational fluid dynamics (CFD) solutions of PCM melting processes require comparatively very long time, i.e., from hours to days or weeks, depending on the system geometry. The present study compares the approaches recommended in the literature in terms of their influence on computation time reduction and accuracy. A horizontally finned tube LHTES unit is modeled in 2-D space using ANSYS Fluent, the most common commercial CFD software for the considered problem in the literature. The outcomes obtained from the attempts to boost the computation efficiency are as follows: adaptive time step size approach causes 72% enhancement in computation time (from 90 hours to 25 hours), frozen flux algorithm and constant thermophysical properties have almost no influence on computation time. Even though low convergence criteria and neglecting natural convection reduces computation time drastically, the errors in accuracy are not in acceptable level.

The technology roadmap

Abstract: The International Energy Agency (IEA), an autonomous agency, was established in November 1974. Its mandate is twofold: to promote energy security amongst its member countries through collective response to physical disruptions in oil supply and to advise member countries on sound energy policy. The IEA carries out a comprehensive programme of energy cooperation among 28 advanced economies, each of which is obliged to hold oil stocks equivalent to 90 days of its net imports. The Agency aims to: n Secure member countries' access to reliable and ample supplies of all forms of energy; in particular, through maintaining effective emergency response capabilities in case of oil supply disruptions. n Promote sustainable energy policies that spur economic growth and environmental protection in a global context – particularly in terms of reducing greenhouse-gas emissions that contribute to climate change. n Improve transparency of international markets through collection and analysis of energy data. n Support global collaboration on energy technology to secure future energy supplies and mitigate their environmental impact, including through improved energy efficiency and development and deployment of low-carbon technologies. n Find solutions to global energy challenges through engagement and dialogue with non-member countries, industry, international organisations and other stakeholders. The European Commission also participates in the work of the IEA. Please note that this publication is subject to specific restrictions that limit its use and distribution. The terms and conditions are available online at Foreword Current trends in energy supply and use are patently unsustainable – economically, environmentally and socially. Without decisive action, energy-related emissions of CO 2 will more than double by 2050 and increased oil demand will heighten concerns over the security of supplies. We must – and can – change our current path; we must initiate an energy revolution in which low-carbon energy technologies play a lead role. If we are to reach our greenhouse-gas emission goals, we must promote broad deployment of energy efficiency, many types of renewable energy, carbon capture and storage, nuclear power and new transport technologies. Every major country and sector of the economy must be involved. Moreover, we must ensure that investment decisions taken now do not saddle us with sub-optimal technologies in the long term. There is a growing awareness of the urgent need to turn political statements and analytical work into concrete action. To spark this movement, at the request of the G8, the International Energy Agency (IEA) is developing a …

Strategies for phase change material application in latent heat thermal energy storage enhancement: Status and prospect

Abstract: The use of phase change materials (PCMs) has enormous potential to store thermal energy from a low-temperature heat source as well as from waste heat as latent heat. The amount of latent heat in PCM is much higher than sensible heat. Therefore, this significant latent heat supply can partially fulfil the energy demand for certain applications. PCMs can supply energy during the power crisis. PCMs are also helping to meet the basic need of life during natural calamities. The enhancement of the thermal properties of PCM can improve the use of PCM as a sustainable resource. In this study, the different processes of thermal property enhancement according to the application are reported and presented in a compiled form. The study reflects that using additives and encapsulation, a change in thermal conductivity, phase change temperature, and latent heat of solid-liquid phase change can be achieved. The changes in size and shape of the PCM container cavity are also reported. There is an improvement in thermal energy storage capacity with an increase in the heat transfer area of the cavity. The review reveals that the encapsulated PCM and PCM composite can give a better performance in latent heat thermal energy storage compared to complicated shaped energy storage devices. Therefore, this complied study will help to select the PCM or PCM composite and in design of LHTES for a specific application. • Review on application of phase change materials • Review on latent heat thermal storage capacity improvement using PCM composite • Review on effect of the shape of LHTES unit