Aytunç Erek

A New Approach to Energy and Exergy Analyses of Latent Heat Storage Unit

In this article, a new approach for energy and exergy efficiencies and effectiveness of latent heat storage systems is developed and applied to a shell-and-tube type latent heat storage system for its charging process. First, a numerical model is introduced to study the heat transfer and thermodynamic parameters and aspects (shell radius and pipe length, Reynolds number, inlet temperature of heat transfer fluid [HTF], etc.), and solved through the governing equations for HTF, pipe wall, and phase change material. Second, some extensive parametric studies are conducted to investigate how the solidification fronts, stored heat, heat transfer rates, entropy generation number, and both energy and exergy efficiencies change with time, particularly in the dimensionless form as the Fourier number. Third, both energetic and exergetic effectiveness concepts are newly developed and applied to a latent heat storage system. The results show that energy and exergy efficiency and effectiveness concepts appear to be significant tools for assessment and optimization of the thermal energy storage systems.

Solidification and Melting Periods of an Ice-on-Coil Latent Heat Thermal Energy Storage System

This paper presents experimental investigations of charging (solidification) and discharging (internal/external melting) periods of an ice-on-coil type latent heat thermal energy storage system. Experimental investigations are performed for various constant heat loads and inlet temperatures with several flow rates of the heat transfer fluid. In experiments, variations of the solid/liquid interfaces around the tubes are monitored with the aid of 15 interface measurement cards for both solidification and melting periods. Energy variations obtained from the measurement cards are validated by conservation of energy, and the mean difference is obtained as 5%. The parametric results indicated that the inlet temperature and the flow rate of the secondary coolant are significant both on the charging and discharging capability of the system. It is also introduced that, for the current experimental conditions, external melting mode can supply relatively lower outlet temperatures for a longer period in comparison with the internal melting mode.

A correlation for planar solidification of water

This study presents a correlation for planar phase change under third kind of boundary condition. The correlation is obtained from the numerical results of the solution of the problem. The aim of the study is to show the obtainability of such correlations for different kind of phase change materials, in the situations where no analytical or approximate solutions exist.

SÜT SOĞUTMA TANKININ BUHAR SIKIŞTIRMALI VE GÜNEŞ ENERJİLİ ABSORPSİYONLU (LiCl-H2O) SOĞUTMA SİSTEMLERİYLE SOĞUTMA PERFORMANSININ DENEYSEL İNCELENMESİ

Bu calismada ciftlik tipi bir sut sogutma tankinin, klasik buhar sikistirmali sogutma sistemiyle sogutulmasina alternatif olarak, gunes enerjili bir absorpsiyonlu sogutma sistemiyle sogutulmasi deneysel olarak incelenmistir. Calismada 1000 litre kapasiteli 2BII sinifi ciftlik tipi bir sut sogutma tanki kullanilmistir. Tank tabani klasik buhar sikistirmali sogutma yapabilecek ozellikte olup, tank cevresi ise absorpsiyonlu sogutma sistemine uygun ozel isi degistirici (rollbond) sistemiyle donatilmis olarak imal edilmistir. Deneysel calismalarda, klasik buhar sikistirmali sogutma sistemi ve hibrit yontem (icsel enerji depolamali LiCl-H 2 O ciftiyle calisan absorpsiyonlu sogutma ile ardindan klasik buhar sikistirmali sogutma sistemi) kullanilarak, sut sogutma tankinin ilk ve son sagim sogutma performanslari Uluslararasi ve Turk standartlarina gore ortaya konulmustur. Her iki sistemle yapilan sogutmada, ilk sagim sogutmasi sinir kabul edilen sure icinde tamamlanmistir. Son sagim sogutmasi ise, buhar sikistirmali sogutma sistemi ile zamaninda tamamlanirken, hibrit yontemle sinir kabul edilen sureden daha fazla zaman almistir. Genel olarak, ayni sogutma kapasitesi icin klasik buhar sikistirmali sogutma sisteminin ozgul enerji ihtiyaci 21,06 Wh/L olurken absorpsiyonlu sogutma sistemi ilaveli hibrit yontemin ozgul enerji ihtiyaci 18,01Wh/L olarak bulunmustur. Ulkemizin avantajli konumda oldugu gunes enerjisi, jeotermal enerji gibi yenilenebilir enerji kaynaklarinin kullanildigi absorpsiyonlu sogutma sistemlerinin farkli sogutma uygulamalarinda daha fazla yer almasiyla onemli duzeyde enerji tasarruflari saglamak mumkun olabilecektir.

Correlations for planar solidification of some phase change materials

Abstract This study presents correlations for one dimensional phase change in cartesian coordinates under the third kind of boundary condition. The correlations are obtained from the numerical results of the solution of the problem defined above and can be used in the related engineering applications with high reliability.