From 1919 to 1923 he studied electrical engineering in Munich. He worked there from 1923 to 1929 as assistant of Prof. Max Dieckmann, with whom he operated a television station at the Verkehrsausstellung (lit.: Traffic exhibition) in Munich in 1925. In the same year Hell invented an apparatus called the Hellschreiber, an early forerunner to the fax. Hell received a patent for the Hellschreiber in 1929.
In the year 1929 he founded his own company in Babelsberg, Berlin. After World War II he re-founded his company in Kiel. He kept on working as engineer and invented machines for electronically controlled engraving of printing plates and an electronically photo lettering system called digiset.
He has received numerous awards such as the Knight Commander's Cross of the Order of Merit of the Federal Republic of Germany, the Gutenberg Prize awarded by the City of Mainz and the Werner von Siemens Ring.
He died in Kiel, Germany.