Калоричні властивості нанофлюїдів, перспективних для застосування в холодильній техніці
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2019-12-09
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.14.06 «Технічна теплофізика та промислова теплоенергетика».
Дисертація присвячена експериментальному дослідженню термодинамічних властивостей модельної системи ізопропіловий спирт/наночастинки Al₂O₃, реального робочого тіла холодильних машин (розчини холодоагенту R600a/компресорне масло), а також багатокомпонентних теплоносіїв на основі водних розчинів пропіленгліколю з домішками наночастинок Al₂O₃. У дисертаційній роботі вивчено вплив наночастинок Al₂O₃ на тиск і густину ізопропілового спирту, проведена оцінка впливу фулеренів С_60 на теплоємність компресорного масла.
Проведені експерименти показали, що домішки наночастинок Al₂O₃ сприяють зменшенню теплоємності ізопропілового спирту як в рідкій, так і твердій фазах, а також призводять до підвищення значення температури плавлення і зниження теплоти плавлення.
З використанням отриманої експериментальної інформації розроблена трифазна модель прогнозування теплоємності і густини нанофлюїдів і розраховані термодинамічні властивості розчинів холодоагенту R600a з компресорним маслом.
На підставі проведених експериментально-розрахункових досліджень показано, що домішки компресорного масла істотно впливають на теплоємність, ентальпію і ентропію холодоагенту R600a.
Встановлено, що домішки наночастинок Al₂O₃ знижують теплоємність багатокомпонентних теплоносіїв (пропіленгліколь/вода/одноатомний спирт/наночастинки Al₂O₃).
Аналіз температурних і концентраційних залежностей надлишкових функцій для густини і теплоємності нанофлюїдів на основі ізопропілового спирту дозволив розробити нову «трифазну» модель прогнозування термодинамічних властивостей нанофлюїдів.
Thesis for a degree of a candidate of technical sciences, specialty 05.14.06 - Technical Thermophysics and Industrial Thermal Power Engineering. The thesis is devoted to experimental investigation of the thermodynamic properties of the model system of isopropyl alcohol (IPA) / Al₂O₃ nanoparticles, the real working fluid of vapor compression refrigeration systems (solutions of R600a coolant / compressor oil), as well as multicomponent fluids based on aqueous propylene glycol solutions with the additives of Al₂O₃ nanoparticles. In thesis, the effect of Al₂O₃ nanoparticles on the pressure and density of isopropyl alcohol was experimentally studied, and effect of C60 fullerenes on the heat capacity of compressor oil was evaluated. For obtained experimental data, an analysis of uncertainties was performed, the temperature and concentration dependences of the research objects were examined. Using obtained experimental information, a three-phase model for predicting the heat capacity and density of the nanofluids was developed and the thermodynamic properties of R600a coolant solutions with compressor oil were calculated. The experiments have shown that addition of Al₂O₃ nanoparticles contributes to a decrease in the heat capacity of isopropyl alcohol in both liquid and solid phases, and also lead to an increase of the melting temperature and decrease in the heat of fusion. The excess molar heat capacity of isopropyl alcohol / Al₂O₃ nanofluids increases with temperature, this effect is observed for the different concentrations of the studied nanofluids. For the first time, the influence of Al₂O₃ nanoparticles on the parameters of the phase transitions of crystalline phase - liquid, glassy state - metastable liquid in IPA was determined. Based on the obtained data for the saturated vapor pressure, temperature and concentration dependences of isopropanol / Al₂O₃ nanofluids were analyzed. It was found that at the low concentrations (up to 2 wt%), Al2O3 additives lead to decrease in the saturated vapor pressure. On the contrary, at the concentration of 3.94 wt.% Al2O3 additives contribute to increase in the saturated vapor pressure of IPA to 4.63%. Based on the performed experimental and computational studies, it was shown that the additives of compressor oil significantly affect the heat capacity, enthalpy and entropy of the R600a coolant. Based on obtained experimental data, reference data tables on the thermodynamic properties of R600a coolant / compressor oil solutions have been developed. It was established that the additives of Al₂O₃ nanoparticles reduce the heat capacity of multicomponent fluids (propylene glycol / water / monohydric alcohol / Al₂O₃ nanoparticles). It was shown that the multicomponent water – propylene solutions with nanoparticle additives have prospect for practical application both as the nanocoolants and working liquids for cold accumulators. The performed study has shown that the thermodynamic properties of the base liquids can be affected not only by the nanoparticle additives, but also by the adsorption layer forming on them (a surface phase), that determines the magnitude of the excess thermodynamic functions. An analysis of the temperature and concentration dependences for the excess functions for the density and heat capacity of the nanofluids based on isopropyl alcohol makes it possible to develop a new “three-phase” model for predicting the thermodynamic properties of the nanofluids on the boiling line.
Thesis for a degree of a candidate of technical sciences, specialty 05.14.06 - Technical Thermophysics and Industrial Thermal Power Engineering. The thesis is devoted to experimental investigation of the thermodynamic properties of the model system of isopropyl alcohol (IPA) / Al₂O₃ nanoparticles, the real working fluid of vapor compression refrigeration systems (solutions of R600a coolant / compressor oil), as well as multicomponent fluids based on aqueous propylene glycol solutions with the additives of Al₂O₃ nanoparticles. In thesis, the effect of Al₂O₃ nanoparticles on the pressure and density of isopropyl alcohol was experimentally studied, and effect of C60 fullerenes on the heat capacity of compressor oil was evaluated. For obtained experimental data, an analysis of uncertainties was performed, the temperature and concentration dependences of the research objects were examined. Using obtained experimental information, a three-phase model for predicting the heat capacity and density of the nanofluids was developed and the thermodynamic properties of R600a coolant solutions with compressor oil were calculated. The experiments have shown that addition of Al₂O₃ nanoparticles contributes to a decrease in the heat capacity of isopropyl alcohol in both liquid and solid phases, and also lead to an increase of the melting temperature and decrease in the heat of fusion. The excess molar heat capacity of isopropyl alcohol / Al₂O₃ nanofluids increases with temperature, this effect is observed for the different concentrations of the studied nanofluids. For the first time, the influence of Al₂O₃ nanoparticles on the parameters of the phase transitions of crystalline phase - liquid, glassy state - metastable liquid in IPA was determined. Based on the obtained data for the saturated vapor pressure, temperature and concentration dependences of isopropanol / Al₂O₃ nanofluids were analyzed. It was found that at the low concentrations (up to 2 wt%), Al2O3 additives lead to decrease in the saturated vapor pressure. On the contrary, at the concentration of 3.94 wt.% Al2O3 additives contribute to increase in the saturated vapor pressure of IPA to 4.63%. Based on the performed experimental and computational studies, it was shown that the additives of compressor oil significantly affect the heat capacity, enthalpy and entropy of the R600a coolant. Based on obtained experimental data, reference data tables on the thermodynamic properties of R600a coolant / compressor oil solutions have been developed. It was established that the additives of Al₂O₃ nanoparticles reduce the heat capacity of multicomponent fluids (propylene glycol / water / monohydric alcohol / Al₂O₃ nanoparticles). It was shown that the multicomponent water – propylene solutions with nanoparticle additives have prospect for practical application both as the nanocoolants and working liquids for cold accumulators. The performed study has shown that the thermodynamic properties of the base liquids can be affected not only by the nanoparticle additives, but also by the adsorption layer forming on them (a surface phase), that determines the magnitude of the excess thermodynamic functions. An analysis of the temperature and concentration dependences for the excess functions for the density and heat capacity of the nanofluids based on isopropyl alcohol makes it possible to develop a new “three-phase” model for predicting the thermodynamic properties of the nanofluids on the boiling line.
Опис
Мотовий І. В. Калоричні властивості нанофлюїдів, перспективних для застосування в холодильній техніці : автореф. дис. ... канд. техн. наук : спец. 05.14.06 "Технічна теплофізика та промислова теплоенергетика" / Мотовий Ігор Віталійович ; наук. кер. В. П. Желєзний ; Одес. нац. акад. харч. технологій. - Одеса, 2019. - 20 с.
Ключові слова
теплоємність, густина, тиск насичених парів, ентальпія, ентропія, нанофлюїд, наночастинки, ізопропіловий спирт, компресорне масло, холодоагент, багатокомпонентні холодоносії, моделі розрахунку, heat capacity, density, saturated vapor pressure, enthalpy, entropy, nanofluid, nanoparticles, isopropyl alcohol, compressor oil, coolant, multicomponent coolants, calculation models