The Thermodynamics of Magnetocaloric Energy Conversion - Magnetocaloric Energy Conversion: From Theory to Applications - page 8

Fig. 1.3 H h T s diagram for the magnetocaloric material gadolinium for magnetic

elds

- - -

between 0 and 10 T

1.3 Magnetocaloric Thermodynamic Cycles

We will start here with some basic equations that relate to cyclic thermodynamics.
We will also represent basic magnetic thermodynamic cycles without regeneration.
In any thermodynamic cycle, the cyclic integral of the state function equals zero.
This holds true for speci c enthalpy, the internal energy, as well as for the magnetic

“ fl H).

Since the internal energy represents the state function, then Eq. ( 1.1 ) for a
thermodynamic cycle can be rewritten in the following form:
I

ow ” work denoted by product (M

·

I I

dw ¼ dq ¼ T ds ð 1 : 22 Þ

Since the cyclic (net) work in the closed system is equal to:
I

¼l 0 I H dM

ð 1 : 23 Þ

dw

And the cyclic integral of the state function, the product of the magnetization and
the magnetic

eld (MH), equals zero: