Parallel capillary expansion tube systems and methods

Patent metadata

Field	Value
Publication number	US-2018094841-A1
Application number	US-201715718282-A
Country	US
Kind code	A1
Filing date	Sep 28, 2017
Priority date	Oct 5, 2016
Publication date	Apr 5, 2018
Grant date	—

Abstract

A cooling system includes an expansion valve configured to exert a first pressure drop on refrigerant circulated through the cooling system. The cooling system also includes a plurality of capillary expansion tubes fluidly coupled in parallel to an output of the expansion valve and configured to exert a second pressure drop on the refrigerant circulated through the cooling system. The cooling system also includes a controller communicatively coupled to the expansion valve, wherein the controller is configured to control magnitude of the first pressure drop by instructing the expansion valve to adjust the valve position based at least in part on refrigerant mass flow expected to be supplied to the expansion valve to facilitate substantially uniformly distributing the refrigerant mass flow between each of the plurality capillary expansion tubes.

First claim

1 . A cooling system, comprising:
an expansion valve configured to exert a first pressure drop on refrigerant circulated through the cooling system; a plurality of capillary expansion tubes fluidly coupled in parallel to an output of the expansion valve and configured to exert a second pressure drop on the refrigerant circulated through the cooling system; and a controller communicatively coupled to the expansion valve, wherein the controller is configured to control magnitude of the first pressure drop by instructing the expansion valve to adjust the valve position based at least in part on refrigerant mass flow expected to be supplied to the expansion valve to facilitate substantially uniformly distributing the refrigerant mass flow between each of the plurality capillary expansion tubes.

2 . The cooling system of claim 1 , wherein the expansion valve comprises a first open cross-sectional area when the expansion valve is at a fully open position that is approximately equal to a second open cross-sectional area of a conduit to be fluidly coupled to an input of the expansion valve.

3 . The cooling system of claim 1 , comprising an evaporator heat exchanger fluidly coupled to the plurality of expansion tubes, wherein:
the evaporator heat exchanger comprises a plurality of evaporator paths; each of the plurality of evaporator paths is fluidly coupled to a corresponding one of the plurality of capillary expansion tubes; each of the plurality of evaporator paths is configured to facilitate heat exchange between the refrigerant circulated through the evaporator heat exchanger and a surrounding fluid; and the controller is configured to control magnitude of the first pressure drop across the expansion valve to facilitate substantially uniformly distributing the refrigerant mass flow between each of the plurality of evaporator paths.

4 . The cooling system of claim 1 , comprising a compressor configured to drive circulation of the refrigerant through the cooling system;
wherein the controller, to control magnitude of the first pressure drop, is configured to:
determine the refrigerant mass flow expected to be supplied to the expansion valve based at least in part on an operating capacity at which the compressor is expected to be operating;
instruct the expansion valve to decrease the valve position from a fully open position when the operating capacity is less than a threshold operating capacity; and
instruct the expansion valve to maintain the valve position in the fully open position when the operating capacity is not less than the threshold operating capacity.

5 . The cooling system of claim 4 , wherein each of the plurality of capillary expansion tubes is sized to enable the expansion valve to substantially uniformly distribute the refrigerant mass flow between each of the plurality of capillary expansion tubes when:
the expansion valve is in the fully open position; and the operating capacity of the compressor is not less than the threshold operating capacity.

6 . The cooling system of claim 4 , comprising an accumulator fluidly coupled to an input of the compressor, wherein the accumulator comprises a reservoir configured to:
enable gas refrigerant to pass through the accumulator to the input of the compressor; and collect liquid refrigerant supplied to the accumulator to reduce likelihood of the liquid refrigerant being supplied to the compressor.

7 . The cooling system of claim 4 , wherein the compressor comprises a variable speed compressor or a plurality of tandem compressor.

8 . The cooling system of claim 1 , wherein:
the cooling system comprises a distributor fluidly coupled between the expansion valve and the plurality of capillary expansion tubes; the expansion valve is configured to produce the first pressure drop to cause a decrease in subcooling of the refrigerant or an increase in flow quality of the refrigerant; and the distributor is configured to facilitate substantially uniformly distributing the refrigerant between each of the plurality capillary expansion tubes.

9 . The cooling system of claim 1 , comprising a sensor communicatively coupled to the controller, wherein:
the sensor is configured to generate sensor data based at least in part on measured refrigerant mass flow in the cooling system, speed of a motor driving a compressor in the cooling system, a number of tandem compressors operating in the cooling system, or any combination thereof; and the controller is configured to determine the refrigerant mass flow expected to be supplied to the expansion valve based at least in part on the sensor data.

10 . The cooling system of claim 1 , wherein the cooling system comprises an air conditioning system, a chiller system, or a refrigeration system.

11 . The cooling system of claim 1 , comprising a compressor configured to drive circulation of the refrigerant through the cooling system;
wherein the controller is configured to control magnitude of the first pressure drop based at least in part on superheat of the refrigerant expected to be supplied to the compressor, and is configured to:
determine the superheat of the refrigerant expected to be supplied to the compressor based at least in part on an operating capacity at which the compressor is expected to be operating;
instruct the expansion valve to decrease the valve position from a fully open position when the operating capacity is less than a threshold operating capacity; and
instruct the expansion valve to maintain the valve position in the fully open position when the operating capacity is not less that the threshold operating capacity.

12 . A method for operating a cooling system, comprising:
determining, using a controller of the cooling system, an expected mass flow of refrigerant to be supplied to an expansion valve in the cooling system as the refrigerant is circulated through the cooling system; instructing, using the controller, an actuator of the expansion valve to maintain valve position at a first open position greater than or equal to a threshold position to produce a first pressure drop across the expansion valve that facilitates substantially uniformly dividing the refrigerant output from the expansion valve between a plurality of parallel capillary expansion tubes when the expected mass flow of refrigerant is greater than or equal to a threshold mass flow; and instructing, using the controller, the actuator to adjust the valve position from the first open position to a second open position less than the threshold position to produce a second pressure drop across the expansion valve that facilitates substantially uniformly dividing the refrigerant output from the expansion valve between the plurality of parallel capillary expansion tubes when the expected mass flow of refrigerant is less than the threshold mass flow, wherein the second pressure drop is greater than the first pressure drop.

13 . The method of claim 12 , wherein determining the expected mass flow of the refrigerant comprises:
determining an operating capacity at which a compressor that drives circulation of the refrigerant through the cooling system is expected to be operating; and determining the expected mass flow of the refrigerant based at least in part on the operating capacity at which the compressor is expected to be operating.

14 . The method of claim 13 , wherein determining the operating capacity at which the compressor is expected to be operating comprises:
determining speed of a motor driving the compressor; determining a number of compressors in operation when the compressor comprises a plurality of tandem compressors; a

Assignees

• Johnson Controls Tech Co

Inventors

• Kester Douglas A
• Caskey Curtis W
• Spitzer James K
• Yelamanchili Chandra
• Mislak Nicholas P
• Karkhanis Rajiv K

Classifications

• F25B2700/1931

  Discharge pressures · CPC title

• F25B2400/13

  Economisers · CPC title

• F25B2500/19

  Calculation of parameters · CPC title

• F25B49/02

  for compression type machines, plants or systems · CPC title

• F25B2700/21163

  of the refrigerant at the outlet of the condenser · CPC title