Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Abstract
Full-field quantitative visualization of freezing interfaces requires the introduction of high
resolution noninvasive methods. Magnetic Resonance Imaging (MRI) is a versatile tool for mapping the
distribution of liquids (primarily water) in three-dimensional space, and is the only practical solution in
systems that are strongly refracting or opaque to visible light. MRI is employed to visualize freezing in
water-saturated packed beds consisting of spherical beads cooled from below. Imaging of the stagnant
interstitial water is accomplished by exploiting the strong contrast in MRI signal between interstitial ice and
liquid water. Our implementation of MRI allows fully three-dimensional reconstruction of the solidification
front and adequate time resolution to quantify the freezing of the pore water. The wall effect, as expressed
by the ratio of bed to bead diameter, is examined with respect to the shape and propagation rate of the
freezing interface. MRI can.be effective only in media that do not affect the imposed magnetic fields. In
heat transfer applications, extra provisions in terms of design and choice of materials of the test section are
np.~essary to accommodate the special environment of the MRI scanner.Air Conditioning and Refrigeration Center Project 5