We don’t know if the fire in Hell is literal or just a vivid image of the torment suffered by the damned.
The Catholic teaching on the particular and general judgments means that damned souls first experience Hell without their bodies (just as most saints first experience Heaven that way). That would seem to imply that the “fire” can’t be only the physical kind, just as the pleasures of Heaven cannot be limited to the physical images of golden streets, clear water, and delicious fruit.
Classical Catholic theology affirms that Hell includes “the pain of sense” as well as “the pain of loss [of God],” but I’m not certain if that has been firmly declared by the Church or is merely a common understanding.
Recent thinking on Heaven and Hell (and, I’m sure, strains of thought going all the way back to the beginning) tends to emphasize the “state of soul” part (immediate proximity to, or total separation from, God) over the images that reflect enhanced versions of earthly pleasures and pains. That’s not to say that the latter might not also exist, especially as most of our experience of Heaven or Hell will be as body-soul composites, glorified versions of the way we exist here and now.
Much of Christian thought seems to have gotten away from the notion of the pains of Hell being punishment deliberately inflicted by God (lest He be painted as a sadist), in favor of the notion that the suffering is a self-inflicted, natural consequence of the decisions that put one in Hell. That has naturally been accompanied by the aforementioned shift from emphasis on external torments like fire to emphasis on the internal pain of separation.
One theory I’m particularly fond of (though of course it is not in any way certain or binding, and may meet with hearty disagreement) is that the afterlife for everyone is essentially the same objective experience – direct exposure to God, the ultimate underlying truth of the universe, without the obstacles and disguises that currently get in the way of our apprehension of Him. Those whose souls are prepared for such an experience know the infinite love of God and reflect it back to him eternally. Those whose souls are still slightly warped experience some painful “straightening out” (Purgatory) before settling into the same experience. Those whose souls are completely occluded are stuck with the same eternal reality, but can only experience it as the terrible torments of Hell. In other words, whether the final experience of God is one of Light or Heat depends on the quality of the “receptor” (the individual soul). Of course, that still uses a lot of physical imagery and so undoubtedly does not approach the reality of the situation.