A novel rotating coil-shaped spiral gas. solid contacting device was proposed. JIS 20(A) size 180 degrees long elbows made of stainless steel were connected to form a five-cycle spiral. This metal model spiral was continuously driven by a motor to transport particles. The external surface of the spiral was heated by use of flexible heaters and the temperature was maintained constant. From the difference in temperature of particles between the inlet and the outlet of the spiral, heat transfer rate was determined. The heat transfer coefficient increased with increasing rotation rate. An empirical equation to estimate the heat transfer coefficent using thermal properties of solids and rotaton rate was obtained. From the results of visual observation of a transparent cold model of the spiral, a packet renewal model of heat transfer was proposed. The model assumed periodical exchange of solids attached to the reactor wall. The heat transfer rate was estimated with this model using the thermal properties of the solid samples. The experimental results of heat transfer coefficent were 0.38-0.50 times the predicted value.