Companies like Pick make direct steam injection systems, these are combination diffusers and control devices.
So you can see I checked the company's profile. As they offer very precise outlet hot water temperature, this application isn't the very best match+it's expensive. Does exist another option?
You could consider a packed bed with steam running countercurrent to water. Simple. Read heat transfer text for corresponding htc values or ask the random packing vendor (Norton etc), and keep to max 80% flood factor. Extract the hot water on level control. You could get some measure of temp control by installing a sparger at tank bottom.
You may find this arrangement in your heat transfer or mass transfer textbook from Uni days. In layman's language, an even simpler configuration is one without a packed for increased heat transfer; these are called quench towers. So basically, this is a packed bed type quench tower. Packing factors used to derive flood factors for various types of traditional random packing are also in your mass transfer textbook.