Liquid chiller evaporator
A shell and coil type heat exchanger evaporator provides cooling for industrial coolants characterized by high viscosity and a poor heat transfer coefficient. A large heat transfer surface area is provided within a limited volume, and without a high coolant pressure drop. A short initial cool down period is provided due to minimized heat exchanger mass and minimized volume of liquid coolant in the heat exchanger during initial cool down.
1. A liquid chiller for cooling very low temperature coolant, said coolant being cooled to outlet temperature T 2 from inlet temperature T 1 at a predetermined mass flow and with limited pressure drop, comprising:
a cylindrical outer casing having an initial internal volume, and including a coolant inlet and a coolant outlet, said coolant inlet and outlet communicating with said initial internal volume, said outer casing further including a refrigerant inlet and refrigerant outlet;
an inner cylinder within said outer casing and having a common longitudinal axis with said outer casing, said inner cylinder occupying a substantial portion of said initial internal volume;
a finned tubing of extended length connected between said refrigerant inlet and said refrigerant outlet for refrigerant flow therethrough, said finned tubing being wrapped around and contacting said inner cylinder and further occupying said initial internal volume, fins of said tubing extending toward an inner surface of said outer casing;
in operation, coolant entering said volume at said coolant inlet flowing over said finned tubing to said coolant outlet, a cold refrigerant flowing through said finned tubing from said refrigerant inlet to said refrigerant outlet absorbing heat from said coolant,
said outer casing and inner cylinder being constructed in materials and dimensions, and said fins and tubing being selected, to provide low mass and a coolant flow passage between the outer casing and inner cylinder around the finned tubing,
said chiller providing rapid cool down of said coolant at start up and, in steady state operation, reducing the inlet temperature T 1 of said coolant to said outlet temperature T 2 , at a predetermined mass flow, and with limited pressure drop and,
said coolant has a kinematic viscosity of at least 10 centistokes at −80 degrees C.
2. A liquid chiller as in claim 1 , wherein said outer casing and said inner cylinder are circular cylinders.
3. A liquid chiller as in claim 1 , wherein closeness of said fins to said inner surface of said outer casing prevents any substantial bypass of said fins by said coolant flow during operation of said chiller.
4. A liquid chiller as in claim 3 , wherein said chiller is sized for use with a refrigerant that is selected from the group consisting of a single refrigerant and a mixed refrigerant.
5. A liquid chiller as in claim 3 , wherein said coolant can flow counterflow crossflow to said refrigerant for heat transfer.
6. A liquid chiller as in claim 3 , wherein said chiller is sized for use with a coolant that is one of a liquid and a gas.
7. A liquid chiller as in claim 6 , wherein said coolant is Galden TH 70.
8. A liquid chiller as in claim 4 , wherein said refrigerant is a mixture of at least two components having normal boiling points at least 90 degrees C. apart.
9. A liquid chiller as in claim 4 , wherein said refrigerant is a mixed refrigerant that is approximately 22% R-14, approximately 9% R-23, approximately 9% R-125, and approximately 60% R-236fa.
10. A liquid chiller as in claim 5 , wherein the temperature increase of refrigerant passing through said chiller in operation is equal to or less than three times the temperature change in the coolant flow.
11. A liquid chiller as in claim 3 , wherein said coolant when flowing over said finned surface has a Reynolds number of approximately 3 to 30.
12. A liquid chiller as in claim 1 , wherein said inner cylinder is at least partially hollow and sealed off from said initial internal volume.
13. A liquid chiller as in claim 3 , wherein said inner cylinder is at least partially hollow and sealed off from said initial internal volume.
14. A liquid chiller as in claim 7 , wherein said inner cylinder is at least partially hollow and sealed off from said initial internal volume.
15. A closed cycle very low temperature refrigeration system comprising:
a refrigeration unit for delivering low temperature, low pressure refrigerant to the refrigerant inlet of the evaporator, and receiving a return flow of said refrigerant at a higher temperature from the refrigerant outlet of the evaporator;
a liquid chiller for cooling low temperature coolant, said coolant in steady state operation being cooled to outlet temperature T 2 from inlet temperature T 1 at a predetermined mass flow and with limited pressure drop, said liquid chiller including:
a cylindrical outer casing having an initial internal volume, and including a coolant inlet and a coolant outlet, said coolant inlet and outlet communicating with said initial internal volume, said outer casing further including a refrigerant inlet receiving said refrigerant from said refrigeration unit and a refrigerant outlet returning said refrigerant to said refrigeration unit;
an inner cylinder within said outer casing and having a common longitudinal axis with said casing, said inner cylinder occupying a substantial portion of said initial internal volume;
a finned tubing of extended length connected between said refrigerant inlet and said refrigerant outlet for refrigerant flow therethrough, said finned tubing being wrapped around and contacting said inner cylinder and further occupying said initial internal volume, fins of said tubing extending toward an inner surface of said outer casing;
in operation, coolant entering said volume at said coolant inlet flowing over said finned tubing to said coolant outlet, said cold refrigerant flowing through said finned tubing from said refrigerant inlet to said refrigerant outlet absorbing heat from said coolant,
said outer casing and inner cylinder being constructed in materials and dimensions, and said fins and tubing being selected, to provide low mass and a coolant flow passage between the outer casing and inner cylinder around the finned tubing,
said chiller providing rapid cool down of said coolant at start up and, in steady state operation, reducing the inlet temperature T 1 of said coolant to said outlet temperature T 2 , at a predetermined mass flow, and with limited pressure drop and, said coolant has a kinematic viscosity of at least 10 centistokes at −80 degrees C.
16. A refrigeration system as in claim 15 , wherein said outer casing and said inner cylinder are circular cylinders.
17. A refrigeration system as in claim 15 , wherein closeness of said fins to said inner surface of said outer casing prevents any substantial bypass of said fins by said coolant flow during operation of said chiller.
18. A refrigeration system as in claim 17 , wherein said refrigerant is one of a single refrigerant and a mixed refrigerant.
19. A refrigeration system as in claim 17 , wherein said coolant flows counterflow to said refrigerant for heat transfer.
20. A refrigeration system as in claim 17 , wherein said coolant is one of a liquid and a gas.
21. A refrigeration system as in claim 20 , wherein said coolant is Galden TH 70.
22. A refrigeration system as in claim 18 , wherein said refrigerant is a mixture of at least two components having component boiling points at least 90 degrees C. apart.
23. A refrigeration system as in claim 18 , wherein said refrigerant is a mixed refrigerant that is approximately 22% of R-14, approximately 9% of R-23, approximately 9% of R-125, and approximately 60% of R-236fa.
24. A refrigeration system as in claim 17 , wherein the temperature increase of refrigerant passing through said chiller in operation is equal to or less than three times the temperature change in the coolant flow.
25. A refrigeration system as in claim 17 , wherein said coolant when flowing over said finned surface has a Reynolds number of approximately 3 to 30.
26. A refrigeration system as in claim 15 , wherein said inner cylinder is at least partially hollow and sealed off from said initial internal volume.
27. A refrigeration system as in claim 17 , wherein said inner cylinder is at least partially hollow and sealed off from said initial internal volume.
28. A refrigeration system as in claim 21 , wherein said inner cylinder is at least partially hollow and sealed off from said initial internal volume.
29. A liquid chiller for cooling very low temperature coolant, said coolant being cooled to outlet temperature T 2 from inlet temperature T 1 at a predetermined mass flow and with limited pressure drop, comprising:
a cylindrical outer casing having an initial internal volume, and including a coolant inlet and a coolant outlet, said coolant inlet and outlet communicating with said initial internal volume, said outer casing further including a refrigerant inlet and refrigerant outlet;
an inner cylinder within said outer casing and having a common longitudinal axis with said outer casing, said inner cylinder occupying a substantial portion of said initial internal volume;
a finned tubing of extended length connected between said refrigerant inlet and said refrigerant outlet for refrigerant flow therethrough, said finned tubing being wrapped around and contacting said inner cylinder and further occupying said initial internal volume, fins of said tubing extending toward an inner surface of said outer casing;
in operation, coolant entering said volume at said coolant inlet flowing over said finned tubing to said coolant outlet, a cold refrigerant flowing through said finned tubing from said refrigerant inlet to said refrigerant outlet absorbing heat from said coolant,
said outer casing and inner cylinder being constructed in materials and dimensions, and said fins and tubing being selected, to provide low mass and a coolant flow passage between the outer casing and inner cylinder around the finned tubing,
said chiller providing rapid cool down of said coolant at start up and, in steady state operation, reducing the inlet temperature T 1 of said coolant to said outlet temperature T 2 , at a predetermined mass flow, and with limited pressure drop and,
said coolant is a liquid coolant having a kinematic viscosity of at least 0.2 centistokes at 25 degrees C. and 2 centistokes at −80 degrees C. and a pressure drop of 2 PSI or less.
30. A liquid chiller for cooling very low temperature coolant, said coolant being cooled to outlet temperature T 2 from inlet temperature T 1 at a predetermined mass flow and with limited pressure drop, comprising:
a cylindrical outer casing having an initial internal volume, and including a coolant inlet and a coolant outlet, said coolant inlet and outlet communicating with said initial internal volume, said outer casing further including a refrigerant inlet and refrigerant outlet;
an inner cylinder within said outer casing and having a common longitudinal axis with said outer casing, said inner cylinder occupying a substantial portion of said initial internal volume;
a finned tubing of extended length connected between said refrigerant inlet and said refrigerant outlet for refrigerant flow therethrough, said finned tubing being wrapped around and contacting said inner cylinder and further occupying said initial internal volume, fins of said tubing extending toward an inner surface of said outer casing;
in operation, coolant entering said volume at said coolant inlet flowing over said finned tubing to said coolant outlet, a cold refrigerant flowing through said finned tubing from said refrigerant inlet to said refrigerant outlet absorbing heat from said coolant,
said outer casing and inner cylinder being constructed in materials and dimensions, and said fins and tubing being selected, to provide low mass and a coolant flow passage between the outer casing and inner cylinder around the finned tubing,
said chiller providing rapid cool down of said coolant at start up and, in steady state operation, reducing the inlet temperature T 1 of said coolant to said outlet temperature T 2 , at a predetermined mass flow, and with limited pressure drop and,
said coolant when flowing over said finned surface has a Reynolds number of approximately 3 to 30.
31. A liquid chiller for cooling very low temperature coolant, said coolant being cooled to outlet temperature T 2 from inlet temperature T 1 at a predetermined mass flow and with limited pressure drop, comprising:
a cylindrical outer casing having an initial internal volume, and including a coolant inlet and a coolant outlet, said coolant inlet and outlet communicating with said initial internal volume, said outer casing further including a refrigerant inlet and refrigerant outlet;
an inner cylinder within said outer casing and having a common longitudinal axis with said outer casing, said inner cylinder occupying a substantial portion of said initial internal volume;
a finned tubing of extended length connected between said refrigerant inlet and said refrigerant outlet for refrigerant flow therethrough, said finned tubing being wrapped around and contacting said inner cylinder and further occupying said initial internal volume, fins of said tubing extending toward an inner surface of said outer casing;
in operation, coolant entering said volume at said coolant inlet flowing over said finned tubing to said coolant outlet, a cold refrigerant flowing through said finned tubing from said refrigerant inlet to said refrigerant outlet absorbing heat from said coolant,
said outer casing and inner cylinder being constructed in materials and dimensions, and said fins and tubing being selected, to provide low mass and a coolant flow passage between the outer casing and inner cylinder around the finned tubing,
said chiller providing rapid cool down of said coolant at start up and, in steady state operation, reducing the inlet temperature T 1 of said coolant to said outlet temperature T 2 , at a predetermined mass flow, and with limited pressure drop and,
said refrigerant is a mixed refrigerant that is approximately 22% of R-14, approximately 9% of R-23, approximately 9% of R-125, and approximately 60% of R-236fa.