Latent heat storage and applications

ABSTRACTDOCTORAL THESISLATENT HEAT STORAGE AND APLICATIONSDERYA DİKİCİMuhsin MAZMANÇUKUROVA UNIVERSITYINSTITUTE OF NATURAL AND APPLIED SCIENCESCHEMISTRY DEPARTMENTSupervisor:Prof. Dr. Halime PAKSOYYear:2003, Pages:190Jury: Prof.Dr. Halime PAKSOYProf Dr. Hunay EVLİYAProf. Dr. Serdar ÖZTEKİNProf. Dr. Sermin ÖRNEKTEKİNProf. Dr. Sultan GİRAYDomestic storage of solar energy in hot water systems usually use inorganic phasechange materials (PCM) to exploit their high storage density and low cost. In passive solarapplications; however, organic compounds are more suitable because these can easily beimpregnated into common construction materials. Organic PCMs are self-nucleating andexhibit none or negligible subcooling. This study attempts to find new PCMs that can beutilized in hot water systems with solar energy storage and enhance their thermalconductivity. Binary mixtures of commercial grade paraffin (Rubitherm-RT54), sodiumacetate trihydrate (CH3COONa·3H2O), and different analytical grade fatty acids (stearic,palmitic, myristic, and lauric acids) were investigated to determine their performance inmixtures. Most PCMs have low thermal conductivities. This is a major drawback thatdecreases thermal performance of the thermal energy storage system. Second step of thestudy focused on enhancing heat transfer between PCM and heat carrier fluid by addition ofstainless steel and copper pieces to PCM (at two different flow rates; 0.05 L/s and 0.025 L/s)and using graphite-PCM composite material (at three different flow rates; 0.05 L/s, 0.025 L/sand 0.01 L/s). In domestic hot water supply by solar energy, water is stored in a tank forshort term. This system stored sensible heat of water by stratification. In the third step addingPCM (Phase Change Material) modules at the top of the water tank would give the systemhigher storage density and compansate heat loss in top layer because of latent heat of PCM.Tests were performed under real operating conditions in a complete solar heating system thathas been constructed at the University of Lleida, Spain.Keywords: Fatty acids, Paraffin, Phase change materials, Thermal energy storage (TES),Stratification.