There is described a spray chamber for cooling a computer processor on a circuit board. The spray chamber comprises: a wall assembly for sealable mounting on an exposed cooling surface of the computer processor defining an enclosure having a top opening and a bottom opening which opens on the top surface of the computer processor; and a lid for covering the top opening of the wall assembly in a sealable manner, the lid having a nozzle which sprays coolant that impinges on the exposed cooling surface of the computer processor.