Experimental Investigation on the Efficiency of a Control Dependent NiTi-Based Cooling Process

Abstract

Energy efficient systems and environmentally friendly solutions are the focus of many commercial development projects. Current refrigeration technology carries a significant share of global energy consumption and exploring alternative refrigeration principles has become increasingly important. Shape memory alloys (SMA’s), especially Nickel-Titanium (NiTi) alloys, generate a large amount of latent heat during solid-state phase transformations, which can lead to a significant cooling effect in the material. These materials not only provide the potential for an energy efficient cooling process, they also minimize the impact on the environment by reducing the need for conventional ozone-depleting refrigerants. This paper presents the first experimental results obtained in a project within the DFG Priority Programme SPP 1599 “Ferroic Cooling”. It focuses on the performance of a control-dependent process of a NiTi-based cooling system. First, a suitable cooling process is introduced and the underlying mechanisms of the process are explained. Then different process variations are developed, which influence the efficiency of the cooling process. These process variations are systematically analyzed with a novel, experimental testing system capable of tuning process parameters independently. The testing system is able to measure force, displacement, temperature distribution and heat simultaneously. The coefficient of performance (of the cooling process) can then be determined by which the influence of the control process on the efficiency can be observed.