Experiments were performed to study heat transfer enhancement in a round tube using wire coils as turbulators. The present study investigates the effect of the clearance between the inner wall of the tube and the wire coil (epsilon/D-1=0.007, 0.05, 0.15, 0.21,and 0.30). The wire coils were made from 1.50 mm diameter copper wire. The test fluid was water. Both heat transfer and pressure drop are measured, and were compared with data for empty tube case. As a result, the heat transfer and the pressure drop decrease with the increasing clearance. A heat transfer correlation is given as Nu(H)={0.231-0.456 (epsilon/D-i)}.Re-H(0.64).Pr-13.