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Heat transfer fluid concentrates include: a freezing point depressant, water, or a combination thereof; a carboxylate; an inorganic phosphate; an azole compound; calcium ions; and a water-soluble polymer. Ready-to-use heat transfer fluids and methods for preventing corrosion in heat transfer systems

Heat transfer fluid concentrates include: a freezing point depressant, water, or a combination thereof; a carboxylate; an inorganic phosphate; an azole compound; calcium ions; and a water-soluble polymer. Ready-to-use heat transfer fluids and methods for preventing corrosion in heat transfer systems are described.

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1. A heat transfer fluid concentrate comprising: a freezing point depressant, water, or a combination thereof;a carboxylate;an inorganic phosphate;an azole compound;calcium ions in a concentration ranging from about 1 mg/L to about 60 mg/L based on a total weight of the heat transfer fluid concentra

1. A heat transfer fluid concentrate comprising: a freezing point depressant, water, or a combination thereof;a carboxylate;an inorganic phosphate;an azole compound;calcium ions in a concentration ranging from about 1 mg/L to about 60 mg/L based on a total weight of the heat transfer fluid concentrate; anda water-soluble polymer; wherein the heat transfer fluid concentrate is free of calcium molybdate. 2. The heat transfer fluid concentrate of claim 1 wherein the water comprises de-ionized water, de-mineralized water, softened water, or a combination thereof. 3. The heat transfer fluid concentrate of claim 1 wherein a hardness of the water due to CaCO3 is less than about 20 ppm and/or wherein an electrical conductivity of the water is less than about 300 μS/cm. 4. The heat transfer fluid concentrate of claim 1 wherein the freezing point depressant comprises an alcohol. 5. The heat transfer fluid concentrate of claim 1 wherein the freezing point depressant is selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, glycerol, and a combination thereof. 6. The heat transfer fluid concentrate of claim 1 wherein the freezing point depressant comprises from about 15 wt. % to about 99% wt. % based on the total weight of the heat transfer fluid concentrate. 7. The heat transfer fluid concentrate of claim 1 wherein the freezing point depressant comprises from about 20 wt. % to about 98% wt. % based on the total weight of the heat transfer fluid concentrate. 8. The heat transfer fluid concentrate of claim 1 wherein the freezing point depressant comprises from about 20 wt. % to about 96% wt. % based on the total weight of the heat transfer fluid concentrate. 9. The heat transfer fluid concentrate of claim 1 wherein the carboxylate comprises a plurality of carboxylates. 10. The heat transfer fluid concentrate of claim 1 wherein the carboxylate comprises an aliphatic mono-carboxylate, an aliphatic di-carboxylate, an aromatic mono-carboxylate, an aromatic di-carboxylate, or a combination thereof. 11. The heat transfer fluid concentrate of claim 1 wherein the carboxylate comprises one or a plurality of C6-C20 carboxylates, and wherein each of the one or the plurality of C6-C20 carboxylates is individually selected from the group consisting of an aliphatic mono-carboxylate, an aliphatic di-carboxylate, an aromatic mono-carboxylate, an aromatic di-carboxylate, and a combination thereof. 12. The heat transfer fluid concentrate of claim 1 wherein the carboxylate comprises 2-ethyl hexanoic acid, neodecanoic acid, or a combination thereof. 13. The heat transfer fluid concentrate of claim 1 wherein the carboxylate comprises a compound selected from the group consisting of benzoic acid, octanoic acid, heptanoic acid, and a combination thereof. 14. The heat transfer fluid concentrate of claim 1 wherein the carboxylate comprises from about 1 wt. % to about 10 wt. % based on the total weight of the heat transfer fluid concentrate. 15. The heat transfer fluid concentrate of claim 1 wherein the inorganic phosphate comprises an orthophosphate, phosphoric acid, or a combination thereof. 16. The heat transfer fluid concentrate of claim 1 wherein the inorganic phosphate comprises a water-soluble alkaline metal phosphate salt, phosphoric acid, or a combination thereof. 17. The heat transfer fluid concentrate of claim 1 wherein a phosphate ion concentration in the heat transfer fluid concentrate ranges from about 0.002 wt. % to about 5 wt. % based on the total weight of the ready-to-use heat transfer fluid. 18. The heat transfer fluid concentrate of claim 1 wherein a phosphate ion concentration in the heat transfer fluid concentrate ranges from about 0.01 wt. % to about 1 wt. % based on the total weight of the ready-to-use heat transfer fluid. 19. The heat transfer fluid concentrate of claim 1 wherein the azole compound comprises a benzotriazole, a tolyltriazole, or a combination thereof. 20. The heat transfer fluid concentrate of claim 1 wherein the azole compound comprises from about 0.01 wt. % to about 3 wt. % based on the total weight of the heat transfer fluid concentrate. 21. The heat transfer fluid concentrate of claim 1 wherein the calcium ions are derived from a water-soluble calcium salt. 22. The heat transfer fluid concentrate of claim 1 wherein the calcium ions are derived from a water-soluble calcium salt that is configured to at least partially disassociate in an aqueous solution at room temperature. 23. The heat transfer fluid concentrate of claim 1 wherein the concentration of the calcium ions ranges from about 3 mg/L to about 40 mg/L. 24. The heat transfer fluid concentrate of claim 1 wherein the concentration of the calcium ions ranges from about 4 mg/L to about 30 mg/L. 25. The heat transfer fluid concentrate of claim 1 wherein the water-soluble polymer comprises an acrylate-based polymer. 26. The heat transfer fluid concentrate of claim 1 wherein the water-soluble polymer comprises an acrylate-based homopolymer, an acrylate-based copolymer, an acrylate-based terpolymer, or a combination thereof. 27. The heat transfer fluid concentrate of claim 1 wherein the water-soluble polymer comprises an acrylate-based polymer, and wherein a ratio of a concentration of the acrylate-based polymer to the concentration of the calcium ions is greater than about 4 and less than about 110. 28. The heat transfer fluid concentrate of claim 1 wherein the water-soluble polymer comprises an acrylate-based polymer, and wherein a ratio of a concentration of the acrylate-based polymer to the concentration of the calcium ions is greater than about 7 and less than about 80. 29. The heat transfer fluid concentrate of claim 1 wherein a pH of the heat transfer fluid concentrate is between about 6.8 and about 9.5. 30. The heat transfer fluid concentrate of claim 1 wherein a pH of the heat transfer fluid concentrate is between about 7.0 and about 9.0. 31. The heat transfer fluid concentrate of claim 1 further comprising a component selected from the group consisting of colorants, antifoam agents, pH-adjusting agents, water-soluble molybdate salts, lithium salts, phosphonates, phosphinates, biocides, and a combination thereof. 32. A ready-to-use heat transfer fluid comprising: water; andthe heat transfer fluid concentrate of claim 1 in an amount ranging from about 40 vol. % to about 60 vol. % based on a total volume of the ready-to-use heat transfer fluid. 33. A heat transfer fluid concentrate comprising: a freezing point depressant, water, or a combination thereof, wherein the freezing point depressant comprises from about 15 wt. % to about 99% wt. % based on a total weight of the heat transfer fluid concentrate;a C6-C20 carboxylate comprising from about 1 wt. % to about 10 wt. % based on the total weight of the heat transfer fluid concentrate, wherein the C6-C20 carboxylate is selected from the group consisting of an aliphatic mono-carboxylate, an aliphatic di-carboxylate, an aromatic mono-carboxylate, an aromatic di-carboxylate, and a combination thereof;an inorganic phosphate selected from the group consisting of an orthophosphate, phosphoric acid, and a combination thereof, wherein a phosphate ion concentration in the heat transfer fluid concentrate ranges from about 0.002 wt. % to about 5 wt. % based on the total weight of the heat transfer fluid concentrate;an azole compound comprising from about 0.01 wt. % to about 3 wt. % based on the total weight of the heat transfer fluid concentrate;calcium ions in a concentration ranging from about 1 mg/L to about 60 mg/L based on a total weight of the heat transfer fluid concentrate; andan acrylate-based polymer; wherein a ratio of a concentration of the acrylate-based polymer to the concentration of the calcium ions is greater than about 4 and less than about 110. 34. A method of preventing corrosion in a heat transfer system, the method comprising: contacting at least a portion of the heat transfer system with a ready-to-use heat transfer fluid;wherein the ready-to-use heat transfer fluid comprises: a freezing point depressant, water, or a combination thereof;a carboxylate;an inorganic phosphate;an azole compound;calcium ions in a concentration ranging from about 1 mg/L to about 60 mg/L based on a total weight of the ready-to-use heat transfer fluid; andan acrylate-based polymer; wherein the heat transfer fluid concentrate is free of calcium molybdate. 35. The method of claim 34 wherein the portion of the heat transfer system comprises a component made by controlled atmosphere brazing. 36. The method of claim 34 wherein a ratio of a concentration of the acrylate-based polymer to the concentration of the calcium ions in the ready-to-use heat transfer fluid is greater than about 4 and less than about 110.