Specific Heat of Salt Water 1

[d23]

Hello All:

I need some help with a formula for specific heat. The Specific Heat of fresh water at 60 degree F is 1 Btu/lb F. Fresh water has a specific gravity of 1.00. Sea water has a specific gravity of 1.0257 and a specific heat of 0.94. Is there some calculation that will give me the specific heat of salt water at various amounts of salinity, say 1.05, 1.10 etc. average specific gravity? Would this only be a linear calc depending on average specific gravity?

Please help
D23

 

[ardilesd]

Having two or three point you could guess a linear relationship between Cp and density, it depends on your requirements. In Perry 6° Ed. You have
TABLE 2-215 Sodium Chloride
Specific heat, cal/g °C

Mole % 6°C 20 C 33 C 57 C
0.249 0.99
0.99 0.96 0.97 0.97
2.44 0.91 0.915 0.915 0.923
9.09 0.805 0.81 0.81 0.82

and there is something similar for density. However, just as a tool for prediction in a given range and not as a general correlation .
Regards

 

[25362]

Although I couldn't find salt water specific heat variations with salinity I did find seawater Cp changes with temperature. For a 35 salinity(about 35 gr of dissolved salts per kg seawater) with a density of 1.025973 g/cubcm @ 15C:

deg. C kcal/(kg.K)
10 0.9520
20 0.9539
30 0.9555
40 0.9562

 

[d23]

25362

I was looking for the info so I could write a spread sheet to calc dt through a pump. I finally did find a chart that went up to saturatioin.

Thanks for your help

David

 

[203RBC]

Good morning.

I see where d23 found a chart of % salinity versus specific heat. Could you please post where the chart can be found?

Thank you for your time.

 

[d23]

203RBC

I did find a chart on line, but I don’t remember the link. I should be home by Nov 13 or 14. I will find the chart and post it then.

D23

 

[d23]

203RBC

The numbers I found are:

Water Specific Gravity Specific Heat
1 1
1.0257 0.94
1.044 0.927
1.058 0.906
1.073 0.887
1.088 0.869
1.104 0.853
1.119 0.839
1.135 0.825
1.151 0.813
1.167 0.801
1.184 0.791

This gets you to saturation.

It should not be a problem to make a set of coefficients for this, but I never did.

Hope this helps!
D23