Thermal loading test of a Wendelstein 7-X pumping gap panel

•The function of the panels is to protect the wall of the plasma vessel behind the pumping gap between the vertical and horizontal divertor plates against radiative heat loads.•New water cooled pumping gap panels have been designed for the steady state operation OP2 of the stellarator Wendelstein 7‐X.•A panel prototype has been cycled in the SIRHEX facility of KIT at about 100 kW/m² and water cooling conditions: Tin=20 °C, P = 0.35 MPa, flow rate = 0,13 and 0,26 kg/s.•The deposited heat load was measured by calorimetry and thermocouples were installed at different location.•A good agreement was found between calculations and test results, and thus the thermohydraulic panel design was well validated.