heat capacity

[tringen1]

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?

 

[m777182]

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.
m777182

 

[25362]

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 c^0.4 G^0.8​

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 K_s, and a unit of pumping power K_p, are included, the value of h is approximately proportional to

(K_s/K_p)^0.3 [κ]^0.6 [η]^-0.5 c^0.4 [ρ]^0.6​

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.