Space- and time-resolved interferometric measurements of the thermal boundary layer at a periodically magnetized gadolinium plate. (August 2015)

• Record Type: Journal Article
• Authors: Lei, Z.; Yang, X.; Haberstroh, Ch.; Pulko, B.; Odenbach, S.; Eckert, K.
• Is Part Of: International journal of refrigeration. Volume 56(2015:Aug.)
• Page Start: 246
• Page End: 255
• Publication Date: 2015-08
• Subjects: Magnetic cooling -- Gadolinium -- Mach-Zehnder interferometer -- Parallel-plate magnetic regenerator; Froid magnétique -- Gadolinium -- Interféromètre de Mach-Zehnder -- Régénérateur magnétique à plaques parallèles; Refrigeration and refrigerating machinery -- Periodicals; 621.56
• DOI: 10.1016/j.ijrefrig.2015.01.004
• Languages: English
• ISSNs: 0140-7007

Abstract

Abstract: By means of a Mach-Zehnder interferometer we examine the transient dynamics of heat transfer from two periodically magnetized gadolinium (Gd) plates into a heat transfer fluid (n-decane). We demonstrate that the propagation of the thermal fronts emanating from the Gd plates after magnetization or demagnetization obeys a t -dependence. A finite time required for magnetization and demagnetization causes a spatially delayed propagation of the thermal fronts. The diffusive heat flux, derived from the temperature profiles, experiences a drop down by about 80% after first 3 s while the percentage of thermal energy transferred into n-decane experiences a maximum there. Although limited to heat transfer into a stagnant fluid, the present works provides reasons for lower bounds of geometry and operation frequency of a simplified parallel-plate structure in the diffusive limit. In this way, the results are instructive for an efficient design of a parallel-plate magnetic regenerator with forced convection. Highlights: Two thin flat gadolinium (Gd) plates immersed into n-decane are periodically magnetized. A Mach-Zehnder interferometer is used to monitor the 2D transient temperature field. The thermal fronts emanating from the Gd plates after magnetization obey a t 1/2 -dependence. A finite time of de-/magnetization causes a spatially delayed propagation of the thermal fronts. The evolution of temperature profiles and heat flux into n-decane is provided in detail.