heat exchanger

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A device, such as an automobile radiator, used to transfer heat from a fluid on one side of a barrier to a fluid on the other side without bringing the fluids into direct contact.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics Any device (such as a radiator) that transfers heat from one fluid to another via a separating wall

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun device that transfers heat from one liquid to another without allowing them to mix