Methods and systems for determining phase state or subcooling state

Patent metadata

Field	Value
Publication number	US-11933528-B2
Application number	US-202117456999-A
Country	US
Kind code	B2
Filing date	Nov 30, 2021
Priority date	Nov 30, 2021
Publication date	Mar 19, 2024
Grant date	Mar 19, 2024

Abstract

Methods and systems provided for determining a phase state and/or for determining a degree of subcooling in a fluid. An exemplary method for operating a refrigeration cycle includes flowing a refrigerant through a metering device and calculating a pressure differential of the refrigerant across the metering device. Further, the method includes determining whether the refrigerant is a saturated liquid based on the pressure differential. The method includes, when the refrigerant is not a saturated liquid, cooling the refrigerant upstream of the metering device.

First claim

What is claimed is:

1. A method for operating a refrigeration cycle, the method comprising:
flowing a refrigerant through a metering device, wherein the metering device is an expansion valve having an inlet and an outlet;
calculating a pressure differential of the refrigerant across the metering device by measuring an inlet pressure of the refrigerant at the inlet and measuring an outlet pressure of the refrigerant at the outlet;
determining that the refrigerant is not a saturated liquid based on the pressure differential by estimating a density correction factor; and
in response to determining that the refrigerant is not a saturated liquid, cooling the refrigerant upstream of the metering device.

2. The method of claim 1 wherein determining that the refrigerant is not a saturated liquid based on the pressure differential comprises estimating the density correction factor Δ from equation (1):
m=A √(2(1+Δ)ρ( P in− P out))

where: m represents expansion valve mass flow rate;
A represents expansion valve effective flow area;
ρ represents liquid refrigerant density at saturation condition;
P in represents pressure at the inlet; and
P out represents pressure at the outlet.

3. The method of claim 2 wherein determining that the refrigerant is not a saturated liquid based on the pressure differential comprises:
querying whether the density correction factor Δ is less than 0; and
when the density correction factor Δ is less than 0, determining that the refrigerant is not a saturated liquid.

4. The method of claim 2 wherein estimating the density correction factor Δ comprises estimating the density correction factor Δ based on an estimation algorithm.

5. The method of claim 2 wherein the refrigeration cycle includes a compressor having a compressor flow rate, and wherein the expansion valve mass flow rate is assumed to be equal to the compressor flow rate, and wherein the expansion valve effective flow area is calibrated.

6. The method of claim 1 wherein no measurement of temperature of the refrigerant is obtained when determining that the refrigerant is not a saturated liquid.

7. The method of claim 1 wherein the metering device is an expansion valve in a refrigerant cycle further including an evaporator, a compressor, and a condenser.

8. The method of claim 1 wherein cooling the refrigerant upstream of the metering device comprises exchanging heat between a coolant and the refrigerant upstream of the metering device.

9. The method of claim 8 further comprising cooling the coolant by exchanging heat between the coolant and the refrigerant downstream of the metering device.

10. A refrigeration system comprising:
a refrigeration cycle including:
a compressor configured to compress a refrigerant;
a condenser configured to condense the refrigerant received from the compressor;
an expansion valve configured to expand the refrigerant received from the condenser,

wherein the expansion valve has an expansion valve inlet and an expansion valve outlet; and
an evaporator configured to evaporate the refrigerant received from the expansion valve;
a heat exchanger configured to selectively cool the refrigerant at the expansion valve inlet;
a pressure sensor device configured to calculate a pressure differential of the refrigerant between the expansion valve inlet and expansion valve outlet; and
a system control module configured to determine that the refrigerant is not a saturated liquid based on the pressure differential, and configured to cool the refrigerant upstream of the expansion valve in response to determining that the refrigerant is not a saturated liquid.

11. The system of claim 10 wherein the pressure sensor device is configured to detect an inlet pressure of the refrigerant at the expansion valve inlet and an outlet pressure of the refrigerant at the expansion valve outlet to calculate the pressure differential of the refrigerant between the expansion valve inlet and expansion valve outlet.

12. The system of claim 11 wherein the system control module is configured to determine that the refrigerant is not a saturated liquid based on the pressure differential by estimating a density correction factor Δ from equation (1):
m=A √(2(1+Δ)ρ( P in− P out))

where: m represents expansion valve mass flow rate;
A represents expansion valve effective flow area;
ρ represents liquid refrigerant density at saturation condition;
P in represents pressure at the expansion valve inlet; and
P out represents pressure at the expansion valve outlet; and
wherein the system control module further comprises an estimation module, including a data processor, for estimating the density correction factor A.

13. The system of claim 10 further comprising a coolant cycle for circulating a coolant, wherein the heat exchanger is configured to selectively cool the refrigerant at the expansion valve inlet by exchanging heat from the refrigerant to the coolant.

14. A method for operating a refrigeration cycle, the method comprising:
flowing a refrigerant through a metering device;
calculating a pressure differential of the refrigerant across the metering device; and
determining whether the refrigerant is a saturated liquid based on the pressure differential by estimating a density correction factor.

15. The method of claim 14 wherein determining whether the refrigerant is a saturated liquid based on the pressure differential by estimating a density correction factor comprises determining that the refrigerant is not a saturated liquid, and wherein the method further comprises cooling the refrigerant upstream of the metering device.

16. The method of claim 14 wherein estimating a density correction factor comprises estimating a density correction factor Δ from equation (1):
m=A √(2(1+Δ)ρ( P in− P out))

where: m represents expansion valve mass flow rate;
A represents expansion valve effective flow area;
ρ represents liquid refrigerant density at saturation condition;
P in represents pressure at an expansion valve inlet; and
P out represents pressure at an expansion valve outlet.

17. The method of claim 1 , further comprising determining a degree of subcooling in the refrigerant based on the pressure differential.

18. The method of claim 17 wherein determining the degree of subcooling in the refrigerant based on the pressure differential comprises estimating a density correction factor Δ from equation (1):
m=A √(2(1+Δ)ρ( P in− P out))

where: m represents device mass flow rate;
A represents device effective flow area;
ρ represents fluid density at saturation condition;
P in represents pressure at a device inlet; and
P out represents pressure at a device outlet.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Shidore Neeraj S
• Sun Min
• Hopper Ryan D
• Smith Cameron Paul

Classifications

• F25B49/02 Primary

  for compression type machines, plants or systems · CPC title

• G01N9/26

  by measuring pressure differences · CPC title

• F25B2700/191

  near an expansion valve · CPC title

• G01N25/12 Primary

  of critical point; of other phase change · CPC title

• G01L13/00

  Devices or apparatus for measuring differences of two or more fluid pressure values · CPC title