An experimental test facility has been designed, constructed, and commissioned for studying the convective heat transfer of an array of 55 impingement jets. Spatial variation in time averaged Nusselt number as well as spanwise time averaged Nusselt number are presented for jet Reynolds numbers of 4,000, 8,000, 12,000, and 15,000 for jet to target standoff distances of z/D=3, 4, and 5. For each of these configurations the exit flow configuration has also been varied to include both a single exit and double exit configuration. For each jet standoff distance and exit configuration, time and overall area averaged Nusselt number is presented as a function of jet Reynolds number. Animations of measured unsteady Nusselt number are presented for selected cases. Numerical simulations have been conducted using the Fluent Computational Fluid Dynamics software package. The three dimensional, compressible, Navier Stokes equations are solved. Results for Nusselt number are presented for a grid dependency study of a steady, single impingement jet impacting a target surface at a standoff distance of z/D=3, at jet Reynolds numbers of 4,000 and 15,000. In the single jet grid dependency study flow is exhausted in all directions after impacting the target surface. Grids ranging from 1.2 million to 13.2 million grid points are evaluated. Unsteady simulations were conducted of a single impingement jet at a jet Reynolds number of 4000, a jet to target standoff distance of z/D=3, flow exiting in two directions, and a pair of repeating boundaries in the other two directions. Two cases were studied. The first with a spacing between the two repeating boundaries of y/D=6 and the second with a spacing of y/D=3. For both cases, contour plots of time averaged, as well as animations of unsteady in plane velocity magnitude, normal component of vorticity, and Nusselt number are presented. Unsteady simulations were also conducted of eleven impingement jets at a jet Reynolds number of 4,000, a jet to target standoff distance of z/D=3, and a double exit configuration. Two cases were studied. The first with a spacing between the two repeating boundaries of y/D=4.03 and the second with a spacing of y/D=3. For both cases, contour plots of time averaged in plane velocity magnitude, normal component of vorticity, pressure, temperature, and Nusselt number are presented. Animations of contours of in plane velocity magnitude, normal component of vorticity, and Nusselt number are also presented. Spanwise time average Nusselt number for both eleven jet numerical cases is compared to that of the central row of an experimental case with a double exit configuration. Comparisons are also made between spanwise average Nusselt number for the central jet of an experimental case, a single jet numerical, the single jet numerical cases with the repeating boundaries, as well as the central jet of the eleven jet numerical cases.