Wyniki wyszukiwania - BazTech

1

Simplified numerical model of magnetocaloric cooling device

Płuszka Paweł, Lewandowski Daniel, Malecha Ziemowit M.

Journal of Power Technologies

|

2019

|

Vol. 99, nr 2

58--66

EN

In the present paper the laboratory scale test stand of a magnetic cooling device is briefly introduced. One set of measurements, for a given geometry of a magnetic bed filled with gadolinium, are presented and used as reference results for developing a zero-dimensional (0D) mathematical model. The 0D model assumes adiabatic heat transfer in the magnetic bed and thermal interaction of the system with surrounding ambient air. Moreover, it takes into consideration the basic dimensions of the bed geometry. Its results give a theoretical upper limit of a temperature span of the proposed magnetic cooling device. The ultimate goal of the proposed 0D numerical model is to gain insight into the basic physics needed to build a full CFD model and optimize system efficiency so as to approach the theoretical temperature limits.

2

Wytwarzanie niskich temperatur metodą chłodzenia magnetycznego

Kotynia K.

Technical Issues

|

2015

|

nr 2

24--31

EN

The discussed process of lowering temperature (below 1 K) concerns the utilization of the magnetic properties of paramagnetic materials. The most important achievements and the progress in the field of low temperatures have been presented. The use of the effect of adiabatic paramagnetic material demagnetization known for over a hundred years has brought about numerous evident benefits. Although the magnetic cooling process is still not commonly used it is applied, for example, as an auxiliary way of attaining low temperatures of around 0 K, but its application is not common. This is due to the fact that the scientists are still searching for an appropriate material which would provide the capability to reduce the temperature to a sufficiently low level. So far, paramagnetic salts and alums, among others, have been used in the adiabatic demagnetization process, but the efficiency of those compounds is too low as against the needs.

3

Ekologiczne chłodziarki magnetyczne

Sulima R.

Prace Instytutu Elektrotechniki

|

2013

|

Z. 261

117--128

PL

Artykuł opisuje cykl przemiany energii w materiałach magnetokalorycznych, prototypy wybranych konstrukcji układów chłodzących, ich wady i zalety. Przedstawiono również tło polityczne i warunki środowiskowe wymagane przez UE w stosunku do urządzeń chłodniczych i klimatyzacyjnych.

EN

The magnetocaloric effect (MCE) is a thermodynamic process in which the temperature changes of a paramagnetic material are the effect of an external magnetic field changing in cycles. The refrigeration occurs in two stages: the first one is the isothermal magnetizing of the material, during which the intensity of the magnetic field rises from H0 to H3 (Fig. 1 process 1-2); during the magnetizing the dipoles of the paramagnetic material become arranged parallely to the intensity of the external magnetic field and the entropy of the material decreases from S1 to S2. As a result of magnetizing, heat is transferred to the surroundings in a quantity proportional to the work executed by the magnetic field. The second stage is the adiabatic demagnetization of the paramagnetic material to the value of the field intensity of H0, during which there occures a decrease in temperature of the material from Tp to T12 (Fig. 2 process 2-3).

4

Efektywne wykorzystanie energii i czyste środowisko - główne kierunki rozwoju w branży chłodniczej i klimatyzacyjno-wentylacyjnej

Skrzypulec W., Konopka-Cupiał G.

Polityka Energetyczna

|

2008

|

T. 11, z. 2

97-106

PL

Wymogi konkurencji na światowych rynkach oraz coraz wyższe wymagania środowiskowe stymulują ciągłe zmiany oraz udoskonalanie istniejących rozwiązań. Równocześnie następuje dynamiczny rozwój ekologicznych technik, alternatywnych w stosunku do chłodnictwa tradycyjnego jak choćby chłodnictwo magnetyczne czy termoakustyczne. W artykule tym omówione zostały główne kierunki rozwoju przemysłu chłodniczego i klimatyzacyjnego w kontekście efektywności energetycznej oraz zagadnień ochrony środowiska które związane są z bieżącą działalnością Centralnego Ośrodka Chłodnictwa COCH.

EN

Competition on world markets and rising environmental requirements enforce development of existing cooling technologies. At this same time rapidly increase develop of new ecological and alternative solutions to conventional refrigeration techniques like thermoacoustic or magnetic refrigeration. In this paper were specified principal development directions of refrigeration and air-conditioning industry in context of energy efficiency and environmental protection which are connected with present Refrigeration Research and Development Centre COCH activity

5

Large magnetocaloric effect in perovskite manganites: magnetic entropy changes above 300 K

Phan M. H., Yu S. C., Ulyanov A. N., Lachowicz H. K.

Materials Science

|

2003

|

Vol. 21, No. 1

133-139

EN

We present here, the results of an investigation of the large magnetic entropy change, M S D , above 300 K in a series of La0.65Sr0.35MnO3, La0.6Sr0.2Ca0.2MnO3, La0.6Sr0.2Ba0.2MnO3, La0.7Ba0.3MnO3 and La0.7Ba0.24Ca0.06MnO3 perovskite manganites. Among the studied compositions, La0.6Sr0.2Ba0.2MnO3 exhibits a highest value of 2.26 J/kg/K for |ASMmax| at the Curie temperature, TC = 354 K, when the field is changed from 0 to 10 kOe. The adiabatic temperature change, ATad, of this sample is ~ 1.1 K and ~ 4.95 K in the fields of 10 kOe and 50 kOe, respectively. Since the large magnetocaloric effect was found in the present materials with above 300 K Curie temperature, these materials seem to be attractive for above room temperature magnetic refrigeration applications.