Environmental Engineering Reference
In-Depth Information
the temperature gradient of the
ow. Today, this is a well-known technique
in magnetic refrigeration at/near ambient temperature.
fl
uid
fl
The problem of low frequency in most case relates to an inef
cient heat-transfer
mechanism. Therefore, like in the case of magnetic refrigeration and magnetic
power generation, we should consider the application of a thermal diode
mechanism combined with a pyroelectric material. Such a principle has recently
been included in a patent application by the authors of this topic in collaboration
with the Josef Stefan Institute from Ljubljana, Slovenia (see also the chapter on
thermal diode mechanisms). This kind of mechanism could provide operating
frequencies in the range 20
200 Hz.
-
All mechanical movements (moving parts, except for those that can be used on
the microscale as thermal diodes) should be strictly avoided.
Besides the Ericsson (Olsen) cycle, other thermodynamic cycles that employ
regeneration should also be considered and evaluated.
10.2 Barocaloric Energy Conversion
In this subsection, we discuss barocaloric energy conversion. The domain of ba-
rocaloric energy conversion has not so far received much attention from the sci-
enti
c community, at least to the same extent as magnetocaloric and electrocaloric
energy conversion. For example, up to 2014, a total of 38 papers were found when
searching for the word
“
barocaloric
”
in the online database Web of Science. In
contrast, when searching for the words
, 273
and 2,876 results were found, respectively. Therefore, only a brief description of the
barocaloric effect is given in this chapter. In addition, some materials that exhibit
the barocaloric effect and their properties are presented.
“
electrocaloric
”
and
“
magnetocaloric
”
10.2.1 Introduction to the Barocaloric Effect and Barocaloric
Materials
Barocaloric energy conversion is based on the so-called barocaloric effect. The
barocaloric effect is a property of some magnetic materials and is expressed as the
temperature change of the material upon varying the pressure [
82
]. Analogously
with the magnetocaloric effect, the material exhibiting the barocaloric effect heats
up when subjected to an increase in the external pressure and cools down as the
external pressure is removed.
The barocaloric effect can be expressed as the adiabatic temperature or iso-
thermal entropy change of the material [
82
]. The isothermal entropy change can be
written as [
82
]:
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