volume expansivity of ethylene glycol vs temp (ercanbaser) 1

[bornlate]

All,

Some time ago there was a discussion about properties of ethylene glycol. I am looking at using a 50/50 EG/H20 mixture for a circulating heat exchanger system. I am looking for expansivity properties of such a mixture over a range of temperatures (-30 to 70C) to be able to calculate how much the fluid will swell and shrink. In the past, Ercanbaser told someone he could email property tables from the ASHRAE fundamentals volume. Is the offer still good?

If the fluid shrinks by much more than the volume of the hard piping, I assume there is a risk of creating vapor bubbles, and sucking in atmosphere from the surroundings?

Thanks for any comments.

 

[25362]

http://www.engineeringtoolbox.com/24_146.html

 

[MJCronin]

born,

Your system should have a properly sized expansion tank to pervent system overpressure...

The size of the tank depends on:

- Total system liquid volume
- Percentage of EG
- Expected temperature operating range

Some "off the shelf" tanks have a flexible bladder, some don't.....all should have a pressure gauge.

For most industrial systems I have seen, the tank size should be somewhere between 2 and 50 gallons.

Dow chemical had written a couple of nice guidelines for EG newbies, one (the "Enginering and Operating Guide")contains a methodology and example for expansion tanks sizing

Although you cannot download it, you can request it from DOW here:

http://www.dow.com/ambitrol/liter.htm

Tell us more about your system...


MJC

 

[bornlate]

Thanks 25362 and MJCronin for being helpful. I will convert the density data from Engineer's toolbox to volume expansivity. I will request the DOW document. Here is more detail on the system.

I have a small system, consisting of a pump, heat exchanger, and direct contact cooler. The heat exchanger will be built by drilling holes in an aluminum block, and there will be about 2 foot of rubber tubing (Swagelock push on multipurpose hose, 1/4" i.d., 1/2" o.d., number PB4) between the outlet of the HX and the direct contact cooler, and the outlet of the direct contact cooler and the inlet of the pump.

The total volume of liquid will be less than 0.25 Liters. Operation will be between -30 and +80C, so we've spec'd a 50/50 mix of H2O/EG. Assuming we fill the system at 20C, there is 60C of heating and 50C of cooling to contend with.
I haven't worked it out yet, but the total volume change will be pretty small, on the order of less than a cubic inch. The system must operate in any orientation, so a standard expansion chamber with an air space isn't really an option. Also, the surroundings will be pressurized, (25 psig N2) so to keep the seals on the direct contact exchanger from a negative dP, we have planned to use a spring-loaded, diaphragm type of expansion chamber.

Anyone have any experience with these?

 

[ercanbaser]

here the tables;

Table 6 Density of Aqueous Solutions of Ethylene Glycol
Concentrations in Volume Percent Ethylene Glycol

Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
0 1018.73 1035.67 1051.78 1066.80 1081.08 1094.64 1107.50 1119.82 1131.62
5 1017.57 1034.36 1050.33 1065.21 1079.33 1092.73 1105.43 1117.58 1129.20
10 1016.28 1032.94 1048.76 1063.49 1077.46 1090.70 1103.23 1115.22 1126.67
15 1014.87 1031.39 1047.07 1061.65 1075.46 1088.54 1100.92 1112.73 1124.01
20 1013.34 1029.72 1045.25 1059.68 1073.35 1086.27 1098.48 1110.13 1121.23
25 1011.69 1027.93 1043.32 1057.60 1071.11 1083.87 1095.92 1107.40 1118.32
30 1009.92 1026.02 1041.26 1055.39 1068.75 1081.35 1093.24 1104.55 1115.30
35 1008.02 1023.99 1039.08 1053.07 1066.27 1078.71 1090.43 1101.58 1112.15
40 1006.01 1021.83 1036.78 1050.62 1063.66 1075.95 1087.51 1098.48 1108.89
45 1003.87 1019.55 1034.36 1048.05 1060.94 1073.07 1084.46 1095.27 1105.50
50 1001.61 1017.16 1031.81 1045.35 1058.09 1070.06 1081.30 1091.93 1101.99
55 999.23 1014.64 1029.15 1042.54 1055.13 1066.94 1078.01 1088.48 1098.36
60 996.72 1011.99 1026.36 1039.61 1052.04 1063.69 1074.60 1084.90 1094.60
65 994.10 1009.23 1023.45 1036.55 1048.83 1060.32 1071.06 1081.20 1090.73
70 991.35 1006.35 1020.42 1033.37 1045.49 1056.83 1067.41 1077.37 1086.73
75 988.49 1003.34 1017.27 1030.07 1042.04 1053.22 1063.64 1073.43 1082.61
80 985.50 1000.21 1014.00 1026.65 1038.46 1049.48 1059.74 1069.36 1078.37
85 982.39 996.96 1010.60 1023.10 1034.77 1045.63 1055.72 1065.18 1074.01
90 979.15 993.59 1007.09 1019.44 1030.95 1041.65 1051.58 1060.87 1069.53
95 975.80 990.10 1003.45 1015.65 1027.01 1037.55 1047.32 1056.44 1064.92
100 972.32 986.48 999.69 1011.74 1022.95 1033.33 1042.93 1051.88 1060.20
105 968.73 982.75 995.81 1007.71 1018.76 1028.99 1038.43 1047.21 1055.35
110 965.01 978.89 991.81 1003.56 1014.46 1024.52 1033.80 1042.41 1050.38
115 961.17 974.91 987.68 999.29 1010.03 1019.94 1029.05 1037.50 1045.29
120 957.21 970.81 983.43 994.90 1005.48 1015.23 1024.18 1032.46 1040.08
125 953.12 966.59 979.07 990.38 1000.81 1010.40 1019.19 1027.30 1034.74
Note: Density in kg/m³



Table 7 Specific Heat of Aqueous Solutions of Ethylene Glycol
Concentrations in Volume Percent Ethylene Glycol
Temperature
°C 10% 20% 30% 40% 50% 60% 70% 80% 90%
0 3.937 3.769 3.589 3.401 3.203 2.997 2.782 2.556 2.322
5 3.946 3.780 3.603 3.418 3.223 3.018 2.806 2.583 2.351
10 3.954 3.792 3.617 3.435 3.242 3.040 2.830 2.610 2.380
15 3.963 3.803 3.631 3.451 3.261 3.062 2.854 2.636 2.409
20 3.972 3.815 3.645 3.468 3.281 3.084 2.878 2.663 2.438
25 3.981 3.826 3.660 3.485 3.300 3.106 2.903 2.690 2.467
30 3.989 3.838 3.674 3.502 3.319 3.127 2.927 2.716 2.496
35 3.998 3.849 3.688 3.518 3.339 3.149 2.951 2.743 2.525
40 4.007 3.861 3.702 3.535 3.358 3.171 2.975 2.770 2.554
45 4.015 3.872 3.716 3.552 3.377 3.193 3.000 2.796 2.583
50 4.024 3.884 3.730 3.569 3.396 3.215 3.024 2.823 2.612
55 4.033 3.895 3.745 3.585 3.416 3.236 3.048 2.850 2.641
60 4.042 3.907 3.759 3.602 3.435 3.258 3.072 2.876 2.670
65 4.050 3.918 3.773 3.619 3.454 3.280 3.097 2.903 2.699
70 4.059 3.930 3.787 3.636 3.474 3.302 3.121 2.929 2.728
75 4.068 3.941 3.801 3.653 3.493 3.324 3.145 2.956 2.757
80 4.077 3.953 3.816 3.669 3.512 3.345 3.169 2.983 2.786
85 4.085 3.964 3.830 3.686 3.532 3.367 3.193 3.009 2.815
90 4.094 3.976 3.844 3.703 3.551 3.389 3.218 3.036 2.844
95 4.103 3.987 3.858 3.720 3.570 3.411 3.242 3.063 2.873
100 4.112 3.999 3.872 3.736 3.590 3.433 3.266 3.089 2.902
105 4.120 4.010 3.886 3.753 3.609 3.454 3.290 3.116 2.931
110 4.129 4.022 3.901 3.770 3.628 3.476 3.315 3.143 2.960
115 4.138 4.033 3.915 3.787 3.647 3.498 3.339 3.169 2.989
120 4.147 4.045 3.929 3.804 3.667 3.520 3.363 3.196 3.018
125 4.155 4.056 3.943 3.820 3.686 3.542 3.387 3.223 3.047
Note: Specific heat in kJ/(kg •K)

(c) 1997 ASHRAE Handbook, Fundamentals, Chapter 20

 

[bornlate]

Ercanbaser,

thanks for the data.

 

[yartes]

There is also some useful information about sizing of expansion tanks for glycol/water heating systems at:

http://www.pmengineer.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2732,109000,00.html

On the other hand, the best ratio for freezing protection is 60% Ethylene Glycol, 40% Water. Whit that, it withstands temp.up to -60F useful for arctic weathers.
Normally it is used 50% which gives freezing protection about -40F or less. More than 60% and the curve shifts up losing dramatically protection.

Hope it helps. I'm on working on this so I though it might help someway, as well.

 

[jmw]

Good data on density and viscosity variation with concentration and temperature from Wintrex:

http://www.houghtonchemical.com/images/specificgravitydata.jpg

but thansk to ercanbaser for the data published above.

JMW

http://www.ViscoAnalyser.com