Inner grooved copper tubes have been widely applied as a kind of enhanced heat transfer tube. Annealing in a copper-tube pit furnace has a relatively high cost to performance ratio, and its operation at elevated temperature and the temperature uniformity of workpieces inside the furnace are difficult to control. Considering the structural characteristics of a pit furnace and using the wall function method, we establish a three-dimensional turbulent flow fluid-structure interaction heat transfer model and compute and analyze the flow field and temperature field inside the furnace. Methods for improving the fan speed, the heights of the gas-guiding cylinder, and the load frame are given. The temperature of critical points inside the furnace during annealing of the copper tubes has been measured and then compared with simulated values, directly validating the accuracy of the computation results. This study not only offers specific methods for improving the annealing quality of inner grooved copper tubes but will serve as a reference basis for quantifying pit furnace improvement. (C) 2016 Elsevier Ltd. All rights reserved.