Development of magnetically-driven cooling device with concentric pipe structure

Abstract

Temperature-sensitive magnetic fluid is a smart material for energy carrier. The most interesting aspect of temperature-sensitive magnetic fluid is that the thermal flow behavior is actively controlled by means of magnetic field. Based on the effect of the temperature-dependent magnetization, temperature-sensitive magnetic fluid can be utilized as an energy conversion system, which can automatically transfer the thermal energy. The advantage in the engineering application can be derived from the fact that there would be entirely no external energy consumption, with which large amount heat can be transported for a long distance without any external power consumption. Taking into account of the advantage, a magnetically-driven cooling device is newly designed for recovering of low- to high-temperature waste heat in the present study. The basic performance of the cooling device with concentric pipe structure is investigated experimentally and data gained in the device is examined in detail in view of magneto-hydrodynamics. In the present study, electromagnet is used as an external magnetic field for the purpose of investigating basic heat transfer characteristics of the present experimental device, so that the magnetic field can be continuously altered. However, it can be easily replaced to a permanent for the practical device without additional electrical energy. The results show that the binary temperature-sensitive magnetic fluid can be circulated freely with a high flow rate of 2.0 × 10−3 m3/min by imposing the magnetic field of 55.8 kA/m. It is found that the newly designed device can transfer thermal energy more than 250 W with overall system efficiency of 11.0% at air temperature of 623 K.