According to the images posted on the official page, they seem to have an internal fan similar as the M1 models:
https://preview.redd.it/gxdt53pahixb1.jpeg?width=824&format=pjpg&auto=webp&s=c4ef471ff59703824123c0f61a86ba51ca27c1dc
Source: https://www.apple.com/imac/
According to the images posted on the official page, they seem to have an internal fan similar as the M1 models:
https://preview.redd.it/gxdt53pahixb1.jpeg?width=824&format=pjpg&auto=webp&s=c4ef471ff59703824123c0f61a86ba51ca27c1dc
Source: https://www.apple.com/imac/