Hull had never before won their two opening matches in a top-flight season but they followed up last weekend's triumph over champions Leicester City in style.
The visitors went in front when Curtis Davies headed Robert Snodgrass's corner into the path of substitute Maloney in the 79th minute.
Hernandez added a second for Mike Phelan's men in stoppage time with a composed sidefooted finish after being played in by Maloney.
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(Reporting by Ed Dove; Editing by Tony Jimenez)
