3 replies to this topic

[gunjan]

Hello........

I got some confusion regarding specific heat of water. We know that specific heat of water is 4.186 KJ/Kg C. Now while calculating by the equation Cp = A + BT + CT^2 + DT^3 I am getting around 1.88 KJ/Kg C at 323 K. I have recheck the values of constants and everything. Please let me know why there is such discrepancy ???
Or the data which is given in all data sheets are for vapor phase only.????????

Thanking You in anticipation.

Regards,

Gunjan

[gvdlans]

1.88 KJ/kg C is the heat capacity of water in the ideal gas state at 323 K, while 4.18 KJ/kg C is the heat capacity of liquid water.

[Ritesh Suratwala]

I have also checked these values and agrees that 1.88 kJ/kgC is for water in Vapor state (or we can say, it is for steam).

[Art Montemayor]

Gunjan:

You should state what pressure (and/or what phase) you are dealing with.

Go to:

http://webbook.nist......*s&STUnit=N/m

Now, you can see how the Cp for water varies with pressure at the constant temperature of 323 ^oK.

The specific heat is not constant even for the liquid water phase - albeit, the variance is small.