자성유체의 밀폐공간내의 열전달 특성에 관한 실험적 연구

Abstract

자성유체의 자연대류는 부력 이외에 자기체적력이 존재하기 때문에 뉴턴유체와 다르다. 본 연구에서는 좌측 및 우측 벽면이 고온 및 저온으로 설정된 정방형 케비티 공간내에서 자성유체의 자연대류를 실험하였다 실험은 열전대에 의한 온도측정과 감온액정에 의한 가시화를 실시하였다. 그 결과 케비티 공간내 자성유체의 전열특성 및 외부에서 가하는 자장의 방향과 세기에 따라 자연대류가 제어됨을 알 수 있었다. Natural convection of a magnetic fluid is different from that of Newtonian fluids because magnetic-body force exists in addition to gravity and buoyancy. In this paper, natural convection of a magnetic fluids (W-40) in a cubic cavity was examined by experimental method. One side wall was kept at a constant temperature (25 <TEX>$^{\circ}C$</TEX>), and the opposite side wall was also held at a constant but lower temperature (20 <TEX>$^{\circ}C$</TEX>). The magnetic fields of various magnitude were applied up and down by permanent magnets. We measured temperatures at 5 points which are the most suitable places in cavity by the analysis record. The thermo-sensitive liquid crystal film (R20C5A) was utilized in order to visualize wall-temperature distributions. Several kinds of experiments were carried out in order to clarify the influence of direction and intensity of magnetic fields on the natural convection. It was found that the natural convection of a magnetic fluids could be controlled by the direction and intensity of the magnetic fields.