3 research outputs found
Investigation of hydrogen plasma activation of the magnesium-nickel alloy powder surface and influence on the hydrogenation.
No full textMetal hydrides are one of the most promising and widely studied methods for hydrogen storage. Metal hydrides attract the large interest of scientists because of high safety standards and high hydrogen gravimetric densities. However, the synthesis of metal hydrides poses certain challenges to the thermodynamic and sorption kinetic properties of related metal hydrides. Therefore, it is necessary to search for optimal ways to improve these properties. This project focuses on the investigation of the magnesium-nickel alloy powder surface activation under hydrogen plasma treatment and its influence on the hydrogen absorption kinetics. Performed plasma activation technical parameters are: 172 W plasma power, 7 cm working distance from the sample to the magnetron, 0.6 mbar working pressure of hydrogen gas, process duration 1–3 h. In this work, the hydrogenation kinetics of the initial and plasma modified powder were investigated using a Sievert-type apparatus. The elemental composition of the surface and chemical bonds analysis was performed by an X-ray photoelectron spectrometer. Changes in surface energy were assessed by measuring the water contact angle. Morphological studies were performed using a scanning electron microscope. Structure changes of the magnesium-nickel alloy powder after the plasma treatment and hydrogenation measurements were analysed by an X-ray diffractometer. The depth of plasma modification was estimated theoretically. In the final thesis, it is observed that the activated powder has higher surface energy and better hydrogenation kinetics properties
Investigation of the influence of mass flow rate on phase change material behaviour
No full textThe paper presents an experimental study of the influence of heat transfer fluid (HTF) mass flow rate on phase change materials (PCM) behaviour. The experimental study was performed on a specially designed test bench. Research object – PCM based thermal energy storage unit which consists of a stainless steel tank with dual circuit tube-fin copper heat exchanger. The tank (storage volume) was filled with phase change material RT82. The experiment was carried out using three different mass flow rates of HTF: high – 0.25 kg/s, medium – 0.125 kg/s, low – 0.05 kg/s. The analysis showed that in the case of high and medium mass flow rates the melting/solidification process highly depends on the temperature of inlet HTF. Influence of mass flow rate is higher in the case of low mass flow rate.
Article in Lithuanian.
Šilumnešio debito įtakos fazinio virsmo medžiagos veikimui tyrimas
Santrauka
Straipsnyje pateikiamas šilumnešio masės debito įtakos šilumai kaupti naudojamų fazinio virsmo medžiagų (FVM) veikimui eksperimentinis tyrimas. Tyrimas buvo atliekamas specialiai pagamintame testavimo stende. Tiriamasis objektas – FVM šilumos kaupimo įrenginys, sudarytas iš nerūdijančiojo plieno talpyklos ir dviejų kontūrų varinio šilumokaičio (vamzdelių) su varinėmis plokštelėmis. Talpykla užpildyta fazinio virsmo medžiaga RT82. Tyrimas atliekamas keičiant šilumnešio masinį debitą. Pasirinktos trys vertės: didžiausia – 0,25 kg/s, vidutinė – 0,125 kg/s ir mažiausia – 0,05 kg/s. Nustatyta, kad, esant didžiausiam ir vidutiniam debitams, FVM lydymosi / kietėjimo proceso trukmei didžiausią įtaką turi tiekiamojo šilumnešio temperatūra, esant mažiausiam debitui vyksta didesnė debito įtaka proceso trukmei.
Reikšminiai žodžiai: šilumos kaupimas, fazinio virsmo medžiaga (FVM), fazinio virsmo šiluma, šilumokaitis, šilumnešio srautas, testavimo stendas
