In the present work, a simple numerical model for transient heat transfer phenomena involving the sensor tube of a thermal mass flow meter (TMFM) is presented. In order to validate the proposed model, extensive experimental investigations are performed. Based on the results of the proposed model, the transient heat transfer mechanism in the sensor tube is explained. Finally, a correlation for predicting the response time of the sensor tube is presented. This correlation can estimate the response time of the sensor tube quantitatively with errors of less than 30%. By using the proposed correlation, physical meanings and characteristics of the response time of the sensor tube are presented. (c) 2005 Elsevier Ltd. All rights reserved.