# US 7,743,615 B2 · Buffered heat transfer fluid for secondary refrigeration systems comprising a formate salt > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,743,615 B2 - Document ID: US7743615B2 - Status: Granted - Kind: B2 - Application number: 10/545,830 - Filed: 2004-02-17 - Published: 2007-08-23 - Granted: 2010-06-29 - Earliest claimed: 2003-02-28 - Assignees: The Lubrizol Corporation - Inventors: Gilbert R. Malone; Stephen H. Stoldt - Web page: https://patentgrep.com/patent/US7743615B2 ## CPC - C23F 11/06: in markedly alkaline liquids - C09K 5/10: Liquid materials - C09K 5/20: Antifreeze additives therefor, e.g. for radiator liquids (for application to surfaces C09K3/18; inhibiting corrosion by liquids C23F11/00) - C23F 11/10: using organic inhibitors - C23F 11/164: {containing a -SO2-N group} - C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25 - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE ## Abstract A formate salt based heat transfer fluid having a pH containing a phosphate for a secondary refrigeration loop is disclosed. The formate based heat transfer fluid generally is a more effective heat transfer medium than a glycol based fluid designed to operate in the same temperature range. The formate based fluid also has lower toxicity and environmental risks than the glycol fluid. ## Claims ### Claim 1 In a heat pump system comprising of a) a primary refrigerant contained in a compression or absorption refrigeration equipment to pump heat between a target and heat sink (towards or from) and b) a potassium and/or sodium salt of formic acid in water used as heat transfer fluid to transport heat away from or towards said refrigeration equipment, the improvement comprising including an alkali nitrite; 0.1 wt. % or more of a buffer component having a pH as a 1 wt. % solution in water above 10, selected from alkali metal borate, alkali metal carbonates, and alkali metal phosphates; and from at least 0.01 weight percent sulfamic acid based on the weight of said heat transfer fluid for said heat transfer fluid. ### Claim 2 (depends on 1) A system according to claim 1, wherein said heat transfer fluid includes less than 10 mole % acetate based on the total moles of formate. ### Claim 3 (depends on 1) A system according to claim 1, wherein said salt of formic acid is present from about 15 to about 75 wt. % based on the weight of said heat transfer fluid. ### Claim 4 (depends on 1) A system according to claim 1, wherein said heat transfer fluid further includes at least one of a salt of acetic acid, an alkylene glycol, and contaminants from a tap water source. ### Claim 5 (depends on 1) A system according to claim 1, wherein the amount of said buffer component having a pH above 10 is from about 0.1 to about 10 wt. %. ### Claim 6 (depends on 5) A system according to claim 5, wherein said buffer is present from about 0.5 to about 5 weight percent. ### Claim 7 (depends on 5) A system according to claim 5, wherein said buffer comprises a mixture of phosphate components giving the heat transfer fluid a pH above 9. ### Claim 8 (depends on 1) A system according to claim 1, wherein said system is a geothermal heating and/or cooling system. ### Claim 9 (depends on 1) A system according to claim 1, wherein said heat transfer fluid has a reserve alkalinity from about 5 mL to about 40 mL of 0.100 N HCl per 10 mL of sample according to ASTM D1121. ### Claim 10 (depends on 1) A system according to claim 1, wherein said system employs a compression refrigeration equipment and said refrigerant is an organic or halogenated organic refrigerant. ### Claim 11 A method for providing cooling and/or heating comprising; a) passing a primary refrigerant through a refrigeration cycle to transfer heat from the evaporator side to the condenser side, b) contacting a heat transfer fluid with said evaporator side or said condenser side of said refrigeration cycle and thereby cooling or heating said heat transfer fluid, c) pumping said heat transfer fluid from said evaporator or condenser side to another location and transferring heat from between said location and said heat transfer fluid, and d) pumping said heat transfer fluid from step c back to said evaporator or condenser side of said refrigeration cycle, wherein the improvement comprises said heat transfer fluid comprising 15 to 75 wt. % of formic acid salt; an alkali nitrite; 0.1 wt. % or more of a buffer component having a pH as a 1% solution in water above 10, selected from alkali metal borate, alkali metal carbonates, and alkali metal phosphates; and from at least 0.01 weight percent sulfamic acid based on the weight of said heat transfer fluid. ### Claim 12 A heat transfer composition comprising water, potassium formate, an alkali nitrite, sulfamic acid, and 0.1 wt. % or more of a buffer component having a pH as a 1% solution in water above 10, selected from alkali metal borate, alkali metal carbonates, and alkali metal phosphates based on the weight of said heat transfer fluid. ### Claim 13 (depends on 12) A heat transfer composition according to claim 12, wherein said buffer component is present from about 0.1 to about 10 wt. %. ### Claim 14 (depends on 12) A heat transfer composition according to claim 12, wherein said buffer component is present from about 0.5 to about 5 wt. %.