The objective of this thesis is to find the optimum time cycle of the regenerator system. The temperature distributions of the overall heat recovery process in a fireclay brick regenerator are investigated by experiments and numerical simulation. The experiments were conducted at Thailand Smelting and Refining Co., Ltd. (Thaisarco), a tin smelting factory, in order to measure and record essential data, such as the fluid temperature, heat storage element temperature, exhaust gas composition and fuel consumption. In the numerical side, the finite difference method is employed to calculate the temperature distribution and the maximum heat recovery. Effects of both axial and transverse conductions on the sensible heat storage element were considered. The developed computer program for optimum time cycle was validated by comparing with the experimental data. From the validation, it was found that the result was in good agreement with exact solution and experiment data. Therefore, present computer program yieldsfairly satisfactory results of calculation. The computer program was developed for operating on Microsoft Windows OS and employed to find the optimum time cycle and the maximum heat recovery for the regenerator of Thailand Smelting and Refining Co., Ltd. The time cycle for changing periods currently used in smelting process Is 30 minutes, which can recover about 32.80% of exhaust heat. From the calculation, the optimum time cycle is 6 minutes, which can recover exhaust heat of 33.26% or 0.46% increase compared to the present time cycle. Thus, in view of field practice, it way be concluded that the factory has already been operating at a suitable condition.