This study examined transient heat transfer characteristics while frosting in order to clarify heat transfer mechanism by which a high heat flux is obtained at the frosting initial stage. For the purpose, a high-precise temperature measurement was carried out in the frost layer and outside of a horizontal cylinder. The thermocouples for the temperature measurement were composed of a chromel wire of 0.1 diameter and several constantan wires of 0.05mm diameter. The chromel wire was welded on the surface of the horizontal cylinder, and several constantan wires were welded in about a 1mm interval on the surface of the chromel wire. As a result, the surface temperature of the frost layer proportionally increased with the increase in the thickness of the frost layer. The time mean value of the measured local Nusselt number decreased in order of the value in the upper part of the cylinder, intermediate and lower parts, were respectively 11.5, 7.5 and 6.0. The measured thermal conductivity of the frost layer rose with the increase in the thickness of the frost layer, and the value was within 0.04-0.12 W/mK.
