a fluid with a higher heat capacity is a good coolant, but what about heating up a fluid. would a higher heat capacity fluid make a good heating medium?
Heat capacity of a medium is not the only property you are taking into account when choosing a heating medium. It would be too simple. Take a look into a heat transfer text.
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From just a heat-transfer point of view when the (single phase) fluid is heating, and flows turbulently through the tubes of a given heat exchanger, the convection coefficient, h, is proportional to
[κ]0.6 [η]-0.4 c0.4 G0.8
where
[κ] = thermal conductivity
[η] = viscosity
c = specific heat capacity or simply specific heat
G = mass velocity
When the density, [ρ], the annualized costs of a unit of heat exchanging surface Ks, and a unit of pumping power Kp, are included, the value of h is approximately proportional to
Thus, when selecting fluids for heating purposes one can use a similar formula for comparison.
There are, of course, other factors to contemplate such as:
[•] low cost,
[•] compatibility with materials of construction,
[•] low vapor pressure,
[•] thermal stability,
[•] ability to tolerate contaminants,
[•] fire safety,
[•] low toxicity,
[•] low reactivity in case of leakage,
[•] easy reclamation or disposal
Thus, it appears that specific heat capacity is just one of the factors to look for in heat-transfer fluids and not necessarily the most important one.
