In this paper, heat transfer between a cold plane next to awire is studied. We measured phase distribution around the wire near the cold plane, using superimposing the waves diffracted from two similar wires of diameter 320 µm in a Mach-Zehnder interferometer. Also by passing electrical current through the wire, the phase distributionin this case is also determined. In this work an 8bit detector is used and achievable accuracy for phase is about π/200.