In this work, the development of a computer program is presented in order to determine the thermal behaviour in multilayer products with simple geometry, hollow or solid by means of the Response Factors method. We can establish a methodology in order to determine heat flows for hollow multilayer products, and heat flows and inner temperatures for solid multilayer products. The program which was developed is designed for variable intervals and it allows the inclusion of the superficial convection coefficient in the cases in which it remains constant, or ifs exclusion from the mathematical model in the cases in which this coefficient does not remain constant, as well as in the cases in which it does not exist (heating or cooling by superficial contact). The method has been used in order to determine the inner temperatures of oranges and lemons in cooling and heating processes. The orange diameters ranged from 7.62 cm to 7.79 cm, the lemon diameters from 6.54 cm to 6.82 cm. The thickness of the peel was between 4.7 mm and 6.8 mm for the oranges and between 5.3 mm and 7.2 mm for the lemons. The comparison between the experimental and estimation temperatures showed good results.