In subsequent studies (Wang, 1998), the switched flow systems was replaced by a fine, fast response mesh heater fitted to the duct inlet that produces a step change in gas temperature. This approach avoids the complexity of operating fast acting valves and model positioning activators and thus simplifies the construction facility. Ekkad et al. (1997, 1998, 1998) used this heated stream approach for film cooling measurements. Here, two transients were necessary to obtain the heat transfer coefficient and the film effectiveness.

Other approaches to introducing a step response in temperature include rapidly inserting a heated model into the wind tunnel or using the preheated wall of the wind tunnel and initiating flow using a diverter door. O'Brien et al. (1986) used a preheated cylinder and inserted it in place across a channel that carried fluid at the ambient temperature. Jones and Hippensteele (1987) preheated the wall of their wind tunnel and then initiated flow by using a diverter door. Baughn and Yan (1991a) described a preheated wall method for the study of heat transfer from a surface to an impinging jet. Baughn (1991b) also developed a duct insertion technique to measure the local heat transfer coefficient.