For the injection molding simulation, the heat transfer coefficient is an important parameter affecting the validity of the simulation results. However, since the heat transfer coefficient depends on numerous influencing factors, the exact value is usually not known. In this work, input values for the heat transfer coefficient in the injection molding simulation of a micro gap during the injection phase are determined by data fitting. The simulations are carried out with the injection molding software SIGMASOFT. The simulations are based on measurement results from wear gap experiments, in which a polymer melt is injected through a micro gap formed by two planar platelet-shaped steel samples. During the tests, the temperatures in the samples near the interface are measured with the use of thermocouples. In the injection molding simulation, the heat transfer coefficients are then adjusted in such a way that the simulation results match the measured temperatures as accurately as possible. Furthermore, the factors that influence the heat transfer coefficient in the simulations are determined and the temperature conditions in the wear gap and in the sample are examined.