Trdninska toplotna stikala v sistemih s cikličnim spreminjanjem temperature

doktorsko delo

Nada Petelin (Author), Mitjan Kalin (Author), Andrej Kitanovski (Mentor)

Abstract

V sklopu doktorskega dela smo se osredotočili na analizo enostopenjske magnetokalorične hladilne naprave s toplotnimi stikali. V prvem delu smo razvili enodimenzionalni numerični model, ki je popisoval delovanje dveh kontaktnih elektrostatičnih trdninskih toplotnih stikal v magnetokalorični hladilni napravi. Osredotočili smo se na vpliv lastnosti materialov ter na vpliv geometrijskih in obratovalnih parametrov na dosežen temperaturni razpon in gostoto hladilne moči magnetokalorične hladilne naprave. Z ovrednotenjem dosežene temperaturne razlike med hladnim in toplim prenosnikom toplote smo določili parametre, ki najbolj vplivajo na delovanje naprave. Eksperimentalno smo določili vpliv temperature in tlačne obremenitve na toplotno kontaktno upornost med posameznimi elementi. Zasnovali smo prototipno eksperimentalno napravo, na kateri smo izvedli parametrično eksperimentalno analizo delovanja toplotnega stikala, ki je vzpostavljal in prekinjal kontakt v odvisnosti od elektrostatičnega polja. Eksperimentalno doseženi rezultati naprave s toplotnim stikalom ne dosegajo primerljivih obratovalnih frekvenc in hladilnih moči glede na obstoječe aktivne magnetne regeneratorje, pri čemer so glavni razlog visoka toplotna kontaktna upornost, toplotni dobitki iz okolice, toplotni dobitki preko zračne reže in toplotni dobitki zaradi segrevanja jedra magnetne strukture. Ugotovitve doktorskega dela niso omejene zgolj na (magneto)kalorične tehnologije, temveč veljajo za poljuben toplotni sistem, kjer sta ključna časovno in krajevno nadzorovanje toplotnega toka med komponentami, ki vzpostavljajo in prekinjajo kontakt in s tem vplivajo na optimalno delovanje naprave.

Keywords

disertacije;toplotno stikalo;toplotni kontrolni elementi;magnetokalorično hlajenje;vodenje toplote;prenos toplote;

Data

Language:	Slovenian
Year of publishing:	2024
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FS - Faculty of Mechanical Engineering
Publisher:	[N. Petelin]
UDC:	621.565.8:66.045:536.24(043.3)
COBISS:	207772675
Views:	17
Downloads:	8
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Solid state thermal switches in systems with cyclic temperature changes
Secondary abstract:	This doctoral thesis focuses on the analysis of a single-stage magnetocaloric cooling device with thermal switches. In the first part, we developed a one-dimensional numerical model of the device with two solid-state electrostatic thermal switches. We focused on how material and geometry properties as well as operating parameters influence the temperature range and cooling power density of the magnetocaloric device. By evaluating the temperature difference between the cold and hot heat exchanger, we were able to identify the parameters that most affect the performance of the device. An experimental investigation was carried out to determine the effects of temperature and pressure load on the thermal contact resistance between the components in contact. A prototype was designed to perform an experimental parametric analysis of the operation of the thermal switch that changes the contact based on an electrostatic field. The experimental results obtained show that the device with a thermal switch does not achieve operating frequencies and cooling performances comparable to the existing active magnetic regenerators. The main reasons for this were the high thermal contact resistance, the heat gains from the surroundings, the heat gains through the air gap and the heat gains due to magnetic core heating. The findings of this doctoral thesis are not limited to (magneto)caloric technologies. They are applicable to any thermal management system where temporal and spatial control of the intensity and direction of heat flow between components is crucial for optimal performance.
Secondary keywords:	dissertations;thermal switch;thermal control elements;magnetocaloric cooling;thermal management;heat transfer;
Type (COBISS):	Doctoral dissertation
Study programme:	0
Thesis comment:	Univ. v Ljubljani, Fak. za strojništvo
Pages:	XXIV, 153 str.
ID:	25050591