The 23-year-old is to spend the campaign in Scotland in order to hopefully obtain regular first-team football and continue his development between the posts.
It is the fifth loan move of his career, following spells with Rochdale, Belenenses, Vitoria Setubal and Kortrijk.
United defender Demi Mitchell has benefited from two stints with the Tynecastle outfit, working under manager Craig Levein, and it is hoped Joel will also prove a success in Edinburgh.
The keeper was part of the Reds' Tour 2019 squad and appeared in the 2-0 victory over Perth Glory, before facing Leeds United in the 4-0 win in Australia
The latest deal means United now have four keepers out on loan - after Alex Fojticek (Stalybridge Celtic), Dean Henderson (Sheffield United) and Kieran O'Hara (Burton Albion) agreed temporary transfers during the English transfer window.