Akademik Veri Yönetim Sistemi
5th INTERNATIONAL ANATOLIAN ENERGY SYMPOSIUM, Trabzon, Türkiye, 24 - 26 Mart 2021, ss.48
Cooling /heating technologies have great importance for sustaining and maintaining the comfort of life in modern
societies such as long-term food storage, home and office air conditioning [1]. The problems of global warming
caused by damages to nature of materials used in existing cooling technologies operating in traditional vapor
compression cycle increase the concerns about environmental issues in society. For this reason, worldwide vapor
compression technologies are being abandoned gradually according to developing technology. Systems based on
solid state-caloric effects which are an alternative to existing cooling technology have been attracting attention
with the studies carried out in recent years [2]. In solid-state cooling technologies of magnetocaloric and
electrocaloric requires a high driving external field to achieve very uniform thermal entropy changes. Among
these, elastocaloric can be defined as different from others because having a stress-induced phase transitions. This
mechanical stress field can be easily produced with the current technological possibilities and the relatively cheaper
than related to the initial investment, maintenance and repair costs [3].
In this study, direct temperature changes under stress based on the elastocaloric effect near room temperature of
systems obtained in NiTi alloy were investigated. NiTi alloy was obtained through an arc melting furnace under
vacuum with Ni and Ti elements and then heat-treated. Surface and composition measurements were performed
by electron microscopy and the crystal structures were determined before and after heat treatment by X-ray powder
diffraction technique. Alloy transforms from B2 (Pm3m) ordered cubic structure to a monoclinic B19 P2 (P2/m)
martensitic phase. The phase transition temperatures of the materials were measured by the temperature-dependent
resistivity measurement system. A home-made system that sensed the temperature change of the material under
mechanical stress fields from 300 to 400 K was used to examine the elastocaloric temperature changes of the
materials in different stress values.
Keywords: Elastocaloric, Ni-Ti, Phase transition