Heat-transfer media having improved thermal stability and based on higher polyglycols

Abstract

The present invention relates to heat-transfer concentrates for solar installations, containing a) from 92 to 99% by weight of at least one polyglycol of the formula R—O—(CH2—CH2—O)n—H, in which n is an integer of from 3 to 500 and R is H, a C1- to C4-alkyl group or an aromatic radical having 6 to 12 carbon atoms,b) from 1 to 8% by weight of at least one corrosion inhibitor, with the proviso that its content of ethylene glycol and 1,2-propylene glycol is less than 0.2% by weight.

Description

Claims

1. A heat-transfer concentrate for solar installations, containing a) from 92 to 99% by weight of at least one polyglycol of the formula R—O—(CH2—CH2—O)n—H, in which n is an integer of from 3 to 500 and R is H, a C1- to C4-alkyl group or an aromatic radical having 6 to 12 carbon atoms,b) from 1 to 8% by weight of at least one corrosion inhibitor,

2. The heat-transfer concentrate as claimed in claim 1, wherein the at least one corrosion inhibitor is selected from the group consisting of borates, silicates, amines, triazoles, thiazoles, molybdates, nitrates, sodium benzoate, and a salt of a mono-, di- or tricarboxylic acid.

3. The heat-transfer concentrate as claimed in claim 1, wherein the content of the corrosion inhibitor ranges from 2 to 7% by weight.

4. The heat-transfer concentrate of claim 1, wherein the polyglycol content ranges from 94 to 98% by weight.

5. The heat-transfer concentrate of claim 1, wherein n is an integer from 3 to 20.

6. The heat-transfer concentrate of claim 1, wherein R is H or methyl.

7. The heat-transfer concentrate of claim 1, wherein the polyglycol is a mixture of triethylene glycol and tetraethylene glycol in the mixing ratio of from 3:1 to 1:3.

8. The heat-transfer concentrate of claim 1, wherein the content of ethylene glycol and 1,2-propylene glycol is less than 0.1% by weight.

9. A heat-transfer medium for solar installations, containing from 30 to 70% by weight of the heat-transfer concentrate of claim 1 and water to 100% by weight.

10. The heat-transfer medium as claimed in claim 9, containing said concentrate and water wherein said heat-transfer medium contains a) from 45 to 55% by weight of at least one polyglycol of the formula R—O—(CH2—CH2—O)n—H, in which n is an integer from 3 to 500 and R is H, a C1- to C4-alkyl group or an aromatic radical having 6 to 12 carbon atoms,b) from 1 to 4% by weight of at least one corrosion inhibitor andc) from 45 to 55% by weight of water,

11. A method for transporting heat or cold in a thermal solar installation, said method comprising circulating a heat-transfer medium in said thermal solar installation, wherein the heat-transfer medium contains a heat-transfer concentrate and water, said heat-transfer medium consisting of a) from 45 to 55% by weight of at least one polyglycol of the formula R—O—(CH2—CH2—O)n—H,in which n is an integer from 3 to 500, andR is H, a C1- to C4-alkyl group or an aromatic radical having 6 to 12 carbon atoms,b) from 1 to 4% by weight of at least one corrosion inhibitor andc) from 45 to 55% by weight of water,