600913 Disclosed herein is an agent when used in a heat-transfer fluid of a heat exchange system or a coolant of a cooling system, for enhancing the heat conductivity thereof, comprising a nano-scale powder of a first material and a micro-scale powder of a different second material, wherein each particle of the nano-scale powder having a particle size smaller than 100 nanometers, and each particle of the micro-scale powder having a particle size between 100 nanometers and 500 micrometers. The ma...