Thermal enhancement of paraffin as a phase change material with nanomagnetite

Paraffin is a common phase-change-material (PCM) exploited in many thermal and solar energy storage applications. Its relatively large latent heat with a stable phase change, nontoxicity and noncorrosivity are the main reasons. Paraffin's low thermal conductivity may become a drawback for high power applications. In this study, the effect of adding nanomaterials to enhance paraffin's thermal performance is investigated. Nanomagnetite (Fe 3O4) particles were prepared by sol-gel method for this investigation. Once characterization of nanomagnetite was done, it was added at 1%, 5%, 10%, and 15% ratios to paraffin (melting range: 46-48 °C) to obtain a paraffin nanocomposite. Thermal characterization with Differential Scanning Calorimeter (DSC) shows that the latent heat storage capacity of paraffin has been increased for 10% nanomagnetite composite, while the melting temperature range remained the same. © 2014 Elsevier B.V.TU0802 110M032The authors would like to acknowledge the support provided by TUBITAK under the Project no. 110M032 and COST Action TU0802 —Next generation cost-effective phase-change-materials for increased energy efficiency in renewable energy systems in buildings (NeCoE-PCM)

The Preparation and Characterization of Chitosan-Gelatin Microcapsules and Microcomposites with Fatty Acids as Thermal Energy Storage Materials

After cellulose, chitosan is the second-most-abundant natural resource and can be used as shell material during microencapsulation. In this study, chitosan-gelatin (CG) microcapsules and microcomposites containing either caprylic or decanoic acid were prepared according to the complex coacervation method and cross-linked by glutaraldehyde. To study the influence of the glutaraldehyde mass ratio upon encapsulation, as well as both the physical and thermal properties of the resulting microcapsules, the properties of microencapsulated phase-change materials (microPCMs) were analyzed by using scanning electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Results show the successful synthesis of microPCMs and melting temperatures of approximately 11.5 and 24.2°C with latent heat storage capacities of 79 and 73Jg-1 for microPCMs containing caprylic acid and those containing decanoic acid, respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Calculations of thermodynamic derivative properties from the NRTL and UNIQUAC models

The local composition models NRTL and UNIQUAC with temperature-dependent parameters have been employed to calculate the surfaces of excess heat capacity, CE p, excess enthalpy, hE and thermodynamic factor, ? for binary liquid mixtures. These thermodynamic properties represent the derivatives of the models with respect to temperature, CE p, hE and composition, ?. The parameters used in evaluating CE p and hE are directly obtained from separate CE p and hE data at different isotherms. Experimental gE and hE data at more than one different isotherm are used simultaneously to estimate the parameters in the evaluation of ?. The following mixtures are considered: methanol(1)-methyl acetate(2); 2-propanol(2)-n-heptane(2); methanol(1)-water(2); benzene(1)-n-heptane(2) and ethanol(1)-water(2). These mixtures show close deviations between experimental and calculated values obtained from both models and also include associating mixtures. Performances of the models based on different types of experimental data have been compared. The models show considerable regional discrepancies of the same thermodynamic property over the entire composition and temperature ranges for the mixtures that show small overall deviations between the calculated and experimental data. © 1997 Elsevier Science B.V

Phase change material sandwich panels for managing solar gain in buildings

In this study, a phase change material (PCM) sandwich panel was developed and tested to evaluate the resulting decrease in heating and cooling loads of a test cabin in Adana, Turkey, where Mediterranean climate prevails. The panel was formed by a macropackage of microencapsulated PCM layer together with an insulation panel. Two different PCMs, with melting points 26°C and 23°C, were used in the panel. Temperature distribution in he cabin was measured for four different cases. In summer, the maximum average temperature reduction achieved in the cabin was 2.5°C when only the PCM was used. This corresponded to a summer cooling load reduction of 7%. In winter, the maximum average temperature increase achieved in the cabin was 2.2°C with the PCM sandwich panel. The winter heating load was decreased by 17%. Energies conserved in cooling and heating were calculated as 186 kWh/year and 206 kWh/year, respectively. Copyright © 2009 by ASME

Nanoencapsulation of n-alkanes with poly(styrene-co-ethylacrylate) shells for thermal energy storage

In this work, we synthesized a series of four nanocapsules containing n-alkanes (CnH2n+2), namely tetradecane, pentadecane, hexadecane, and heptadecane, in poly(styrene-co-ethylacrylate) using an emulsion copolymerization method. The nanocapsules were characterized according to their geometric profiles, phase transition temperatures, phase transition heats, mean particle sizes, and chemical stabilities by means of scanning electron microscopy, differential scanning calorimetry, thermal gravimetric analysis and Fourier transform infrared spectroscopy. Furthermore, we also focused on the effect of the core/shell mass ratio on the phase change properties of the nanocapsules. We found that microcapsules were synthesized successfully and that the best core/shell mass ratio was 3:1 for this study. These results indicate that encapsulated n-alkanes with poly(styrene-co-ethylacrylate) have an excellent potential for energy storage. © 2014 Elsevier Ltd.111M614We would like to thank The Scientic & Technical Research Council of Turkey (TUBITAK) (The Project Code: TUBITAK 111M614 ) for their financial support for this study. And also we would like to thank Mr. Suleyman Konuklu for his technical support for this study. Finally, we would like to extend special thanks to the editor and the anonymous reviewers for their constructive comments and suggestions in improving the quality of this paper

Microencapsulation of caprylic acid with different wall materials as phase change material for thermal energy storage

In this study, caprylic acid (octanoic acid) suitable for thermal energy storage applications was microencapsulated with different wall materials, including urea-formaldehyde resin, melamine-formaldehyde resin, urea+melamine-formaldehyde resin. Microcapsules were prepared using coacervation method. Hardening process of microencapsulated phase change material (PCM) was done with formaldehyde. The morphology and particle sizes of microencapsulated PCM were analyzed by scanning electron microscopy, (SEM). The latent heat storage capacities of caprylic acid and microencapsulated caprylic acid were determined with differential scanning calorimetry (DSC). The chemical characterization of microcapsules was determined by Fourier transformed infrared (FTIR) spectroscopy. It is concluded that urea-formaldehyde resin was the best capsule wall material for caprylic acid. Based on all results, it can be considered that the microcapsules were synthesized successfully and that, the phase change enthalpies of melting and freezing were about 93.9 J/g and 106.1 J/g, respectively, the particle diameter was 200 nm-1.5 µm. © 2013 Elsevier B.V.111M614 Firat University Scientific Research Projects Management Unit: FEB2011118We would like to thank The Scientific & Technical Research Council of Turkey ( TUBITAK ) (The Project Code: TUBITAK 111M614 ) and Research Projects Unit of Nigde University (The Project code: FEB2011118 ) for their financial support for this study. And also we would like to thank Mr. Suleyman Konuklu for his technical support for this study

Microcapsulation and macrocapsulation of phase change materials by emulsion co-polymerization method

In this study, decanoic acid suitable for thermal energy storage applicationswas microencapsulated with poly(styrene-co-ethyl acrylate) by emulsion copolymerizationmethod. Chemical structures, morphological characteristics, andthermal properties of microcapsules and macrocapsules were determined usingFourier Transfer Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy(SEM), and Differential Scanning Calorimeters (DSC) respectively. The microPCMsand macroPCMs were synthesized successfully and the encapsulation ratio wasabout up to 65.5 %. As a result, the as-prepared microcapsules show good potentialsfor thermal energy storage and could be used in many applications. © Springer International Publishing Switzerland 2015

The performance of UNIFAC and related group contribution models part II. Prediction of Henry's law constants

Henry's law constants for 24 different systems have been determined using UNIFAC and related group contribution models. The results obtained from original, modified and free-volume effect UNIFAC models are compared with experimental results. Empirical relationships for the temperature-dependency of Henry's constant for the chloroform(1)-water(2) system are also determined

Greenhouse heating with solar energy and phase change energy storage

A Phase-Change Energy Storage (PCES) system was used to heat a greenhouse of 180 m2. For the seasonal heat storage unit, paraffin was used as the phase change material (PCM). The system consists mainly of four units: solar air heaters, the seasonal heat storage unit, the greenhouse and a computerized data-acquisition/control unit. The absorber surface of the installed air heaters is 0.15 m2 per square meter of greenhouse ground surface. The storage tank volume is 0.055 m3 per square meter of greenhouse ground surface, and the storage volume is about 0.37 m3 per square meter of the solar air heaters. The storage tank contains 6 000 kg of paraffin PCM, of which the thermal properties, as measured with a Differential Scanning Calorimeter (DSC), were: melting temperature range of 48 - 60 °C and latent heat of melting 190 kJ/kg. All the temperatures at the inlet and outlet of the storage tank, the solar air heaters, and in the tank and the greenhouse were measured by thermistors each second, and the 15-minute averages were recorded and fed into the data-logger and computer control system. In this paper, the preliminary results obtained during the charging period of the storage tank, August and September 1994 in the first year of the experiment are presented. During the charging periods of August and September of 1994, an average values of the air temperature at the outlet of the collectors were 59.6 and 56.7 °C, respectively. The average temperature of the paraffin reached 46.8 °C and 49.3 °C during August and September 1994, respectively

Improving performance of household refrigerators by incorporating phase change materials

Abstract Efforts to increase energy efficiency of refrigerators shall directly reduce energy consumption in residential buildings. Incorporating phase change materials (PCM) is a new approach to improve the performance of refrigerators. In this study, we have tested four different PCMs in two different refrigerator models. Compressor on/off time was optimized and better energy efficiency was achieved. Increasing condenser surface area by 20% enhanced the PCM effect. The use of only 0.95 kg of PCM has resulted in a 9.4% energy saving. Economic analyses show that using PCMs in household refrigerators is clearly a cost effective method that saves energy and reduces harmful emissions. © 2015 Elsevier Ltd and IIR