Note: this is in fact the value of the ‘international steam table calorie’ and corresponds
to the specific heat at 14C. The specific heat of water is very slightly higher at each
end of the liquid phase range: 4.21 kJ/kg K at 0C and at 95C, but these variations
may be neglected.
The use of antifreeze (ethylene glycol) as an additive to water permits operation
over a wider range of coolant temperatures. A 50 per cent by volume solution of
ethylene glycol in water permits operation down to a temperature of −33C. Such
an antifreeze also raises the boiling point of the coolant and a 50 per cent solution
will operate at a temperature of 135C with pressurization of only 1.5 bar.
The specific heat of ethylene glycol is about 2.28 kJ/kg K and, since its density
is 1.128 kg/l, the specific heat of a 50 per cent by volume solution is: