1 Answer

Conduction of heat is across a cross section and we talk of conduction when both sides of a thick block of the material are at different temperatures. If we consider a metal block The heat from one side of the block to the other is conducted very easily. We have to compare the thermal conductivity values to check whether a substance is a good or bad conductor. water has a thermal conductivity of 0.0014 (cal/sec)/(cm C) whereas glass has 0.0025(cal/sec)/(cm C)and silver is 1.01(cal/sec)/(cm C). So it can be seen that water is not as good conductor of heat as any of the metals. But still it is used in radiators due to the forced pumping used to convection cooled mechanism. Source: http://www.engineershandbook.com/Tables/thermalconductivity.htm