## 3 Present Method for Determining the Heat Transfer Coefficient  
### Experimental Setup  
The experimental setup for analysing the forced convective heat transfer of the impingement jet on a metal strip is shown in Figure 3. The forced heat transfer coefficient is calculated by performing an energy balance based on temperatures measured using an IR thermal camera (InfrTec GmbH Infrarotsensorik und Messtechnik, Dresden, Germany), as described in Section 3.2. The test setup consists of a fan, an inlet section with a volume flow measurement, a distribution chamber, a variable nozzle array and a conductive heated strip. The fluid is drawn in by the fan, which can achieve a maximum pressure increase of \(\Delta p\) = 22,800 Pa at a maximum fan speed of \(r\) = 3000 min\({}^{-1}\). The maximum achievable volume flow is \(\dot{V}\) = 15,000 m\({}^{3}\)/h, the maximum motor-connected load of the fan is \(P\) = 90 kW. The fan is connected to a tube that leads to the distribution chamber. Here, a volume flow measurement in the form of a Wilson measurement grid is included. The measurement grid has a diameter of \(D_{grid}\) = 388.8 mm. The inlet and outlet sections of the volume flow measurement are designed in accordance to DIN 5167 [18]. Accordingly, the length of the inlet section is five times larger than the grid diameter while the length of the outlet section is two and half times the grid diameter in order to ensure a fully developed undisturbed flow at the measuring point. Various nozzle systems can be easily installed onto the \begin{table}
\begin{tabular}{c c c c c} \hline \hline
\begin{tabular}{c} Thermocouple, \\ heated surface \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Studies on determining the heat transfer coefficient for round nozzle systems according to [10]. distribution chamber to analyse different nozzle geometries and nozzle pitches s. The nozzle box has a maximum area of 1480 \(\times\) 1560 mm\({}^{2}\). Located above the nozzle field, there is a conductive heated strip with an area of 630 \(\times\) 1160 mm\({}^{2}\) representing the impingement surface. The strip is resistance-heated via three transformers, each with an electrical power of \(P\) = 12.5 kVA. Each transformer provides an equal proportion of the total power. The distance between the electrically heated strip and the nozzle system \(H\) can be adjusted between \(H\) = 0 and 250 mm using an electric motor. During the measurement, an impingement flow causes convective heat transfer that locally cools the strip. This, together with the electric heating of the strip, creates a specific temperature field. This temperature field is measured using an IR thermal camera. With a resolution of 640 \(\times\) 480 pixels (total 307,200 pixel), it determines an individual temperature \(T_{xy}\) for each pixel. For the area of the heated strip and with a distance of 1.3 m between the camera lens and the strip, each pixel describes a strip area of 1.28 \(\times\) 1.28 mm\({}^{2}\). Additional plates are mounted on all four sides of the strip to increase the impingement surface area. These plates extend the surface area to 930 \(\times\) 1500 mm\({}^{2}\). Without these edge plates, the impinging flow would be diverted over the strip edges, potentially causing cooling on the top side of the strip and leading to incorrect temperature distribution measurements. To investigate edge effects, the edge plates of the strip can be removed. Edge effects in forced convection cooling refer to changes in heat transfer caused by flow at the edges of the strip. The temperature profiles at the edges may differ from those in the rest of the strip, depending on the nozzle system used. The experimental setup is also equipped with Pitot tubes at the nozzle outlets and several pressure and temperature measuring points. The flow from the inlet section to the nozzle outlet can be characterised due to the multiple measurement points. This is particularly necessary for the exact determination of the fluid performance of each nozzle system.