Ali Karaipekli

Thermal Characteristics of Paraffin/Expanded Perlite Composite for Latent Heat Thermal Energy Storage

Abstract This study focuses on the preparation and thermal properties of paraffin/expanded perlite composite as novel form-stable phase change material for latent heat thermal energy storage by vacuum impregnation method. The paraffin could be absorbed in pores of expanded perlite as much as 55 wt% without melted phase change material seepage from the composite and this mixture was described as form-stable composite phase change material. The melting and freezing temperatures and latent heats of form-stable composite phase change material were measured using differential scanning calorimetry analysis. The thermal cycling test indicated that the form-stable composite phase change material had good thermal reliability in terms of the changes in thermal properties after 5,000 thermal cycling. Thermal conductivity of the form-stable composite phase change material was increased by about 46% by adding 5 wt% expanded graphite. The results indicated that the prepared form-stable paraffin/expanded perlite/expanded graphite composite phase change material has a great potential for latent heat thermal energy storage systems solar passive heating purposes due to suitable phase change temperature, high latent heat capacity, good thermal reliability, and thermal conductivity.

Thermal Properties and Thermal Reliability of Capric Acid/Stearic Acid Mixture for Latent Heat Thermal Energy Storage

Abstract This study focuses on the preparation of capric acid/stearic acid mixture as novel phase change material for latent heat thermal energy storage and determination of its thermal properties and thermal reliability by using differential scanning calorimetry analysis technique. The differential scanning calorimetry results indicated that the capric acid/stearic acid mixture with eutectic composition (83/17 wt%) was suitable phase change material for latent heat thermal energy storage applications in terms of phase change temperatures (Tm: 24.68°C; Tf: 24.71°C) and latent heat capacities (𝛅 Hm: 178.64 J/g; 𝛅 Hf: 178.86 J/g). Accelerated thermal cycling test showed that the changes in phase change temperatures and the latent heats of the phase change material with increasing thermal cycling number were irregular. The probable reason of the changes in thermal properties of the phase change material with thermal cycling were also investigated using Fourier transform infrared spectroscopy method. Based on all results, it was concluded that thermal properties and long term thermal reliability of the prepared capric acid/stearic acid mixture makes it potential phase change material for heating and cooling purposes using a latent heat thermal energy storage system.

Capric Acid and Myristic Acid for Latent Heat Thermal Energy Storage

Abstract The present study was focused on three aims: (1) preparation of the phase-change gypsum wallboard as novel phase-change wallboard incorporated with the eutectic mixture of capric acid (CA) and myristic acid (MA) for latent heat thermal energy storage (LHTES); (2) determination of thermal properties and thermal reliability of prepared phase-change wallboard using differential scanning calorimetry (DSC) technique; and (3) estimation of thermal performance of the phase-change wallboard in a simple building envelope. The maximum proportion of CA/MA eutectic mixture as phase-change material (PCM) absorbed in gypsum wallboard was about 25 wt% of total weight. No leakage of the PCM from the phase-change wallboard was observed after 1,000 thermal cycling. The melting and freezing temperatures and latent heats of phase-change wallboard were measured as 21.12°C and 21.46°C, 36.23 and 38.28 J/g, respectively, by DSC analysis. These properties make it functional as LHTES medium, which can be applied to peak load shifting, improving the use of waste heat and solar energy, as well as more efficient operation of heating and cooling equipment. In addition, the phase-change wallboard has good thermal reliability in terms of the changes in its thermal properties after 500 and 1,000 thermal cycling. Furthermore, thermal performance test indicated that the phase-change wallboard can be considered as an effective building element because of reducing the indoor temperature of the room approximately 4°C and thereby improving thermal comfort of a building envelope.

Thermal Properties and Long-term Reliability of Capric Acid/Lauric Acid and Capric Acid/Myristic Acid Mixtures for Thermal Energy Storage

Abstract This study was aimed at preparing the capric acid (CA)/lauric acid (LA) and capric acid (CA)/myristic acid (MA) mixtures as novel phase change materials (PCMs) for low-temperature latent heat thermal energy storage (LHTES) and to determine their thermal properties and long-term thermal reliability by using differential scanning calorimetry analysis technique. The DSC results indicated that the CA/LA and CA/MA mixtures with eutectic composition were suitable PCMs for low-temperature LHTES applications in terms of melting temperature (18.51°C for CA/LA and 21.70°C for CA/MA mixture) and latent heat of fusion (162.85 J/g CA/LA and 168.37 J/g for CA/MA mixture). Accelerated thermal cycling test showed that the phase change temperatures and the latent heats of the PCMs were in decreasing trend, but the variations with increasing thermal cycling number were irregular. The probable reasons of the changes in thermal properties of the PCMs with increasing thermal cycling number were also investigated using Fourier transform infrared spectroscopy method. Based on all results, it was concluded that the prepared and tested CA/LA and CA/MA mixtures as novel PCMs have good thermal properties and long-term thermal reliability for low-temperature LHTES systems used in solar passive heating and cooling applications.

Polyethyl Methacrylate (PEMA)/Fatty Acids Blends as Novel Phase Change Materials for Thermal Energy Storage

This study deals with the preparation and characterization of polyethyl methacrylate/fatty acid blends as a novel form-stable phase change material for latent heat thermal energy storage applications. In the blends, fatty acids act as a phase change material when polyethyl methacrylate is operated as a supporting material. The fatty acids could be retained by 50 wt% into polyethyl methacrylate without melted phase change material seepage from the blends. Therefore, these blends are called form stable composite phase change materials and they have utility advantage without encapsulation in passive latent heat thermal energy storage applications. The prepared fatty acid/polyethyl methacrylate blends (50/50 w/w%) as form-stable phase change material was characterized using optic microscopy and Fourier transform infrared spectroscopy methods and the results showed that the polyethyl methacrylate was physically and chemically compatible with the fatty acids. Thermal properties and thermal stabilities of the form-stable phase change materials were measured using differential scanning calorimetry. Differential scanning calorimetry results indicated that the melting temperatures and latent heats of the prepared phase change materials are in the range of 30.67–61.09°C and 86.93–107.75 J/g, respectively. The thermal cycling test, including 5,000 cycling processes, was conducted to determine the thermal reliability of the synthesized form-stable phase change materials, and it is found that phase change materials were thermally and chemically stable after thermal cycling. On the basis of all the results, it was concluded that form stable polyethyl methacrylate/fatty acids composite phase change materials had important potential for practical latent heat thermal energy storage applications, such as under floor space heating of buildings and passive solar space heating of buildings by using wallboard, plasterboard, or floors impregnated with a form stable phase change material.