"Heat" is a typical Imagist poem. It's short, concise, and it's got some pretty intense and evocative images. It's also written in free verse, which means that it doesn't have a regular rhyme scheme or meter. There's none of that fancy-pants poetry stuff here.
But "Heat" is not some crazy disorganized mess. It's actually a really tight, precise, and sonically dense poem. There are just so many repeated sounds—"heat" and "rend" are all over the first stanza, and the poem is filled with alliteration (the Fs in "fruit cannot fall") and consonance (the Ts in "cut apart the heat").
"Heat" is thus held together by a web of repeating sounds. We feel a little caught in this web when we read the poem—it's like there's no escape from the little world that H.D. creates in which sounds are bouncing all around.
We can't escape the bounds of the poem! The speaker can't escape the heat! The poem's form puts its readers (us) in the same position as its speaker. Kinda impressive, don'tcha think?