COLD WATER CIRCULATION SYSTEM

• US 20150354851A1
• Filed: 12/26/2013
• Published: 12/10/2015
• Est. Priority Date: 12/28/2012
• Status: Active Grant

• Current Assignee: NTT Facilities Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Facilities Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Kaneko, Shinichiro, Yoshii, Ari, Tashiro, Kanji
• Granted Patent: US 10,203,128 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F24F 11/83 by controlling the supply of heat-exchange fluids to heat-exchangers
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 11/85 using variable-flow pumps
• CPC Class Codes: F24F 3/06 characterised by the arrangements for the supply of heat-exchange fluid for the subsequent treatment of primary air in the room units
• CPC Class Codes: F24F 5/0003 Exclusively-fluid systems
• CPC Class Codes: H05K 7/2079 within rooms for removing heat from cabinets

Abstract

A cold/chilled water circulation system comprises a thermal source, an AHU, a pump, and a control section. The thermal source cools chilled water to a specified temperature. The AHU is an air conditioner that cools air by heat exchange with the chilled water. The pump feeds the chilled water having a flow rate corresponding to an operating frequency of a power inverter to the AHU from the thermal source. The control section calculates a degree of surplus, which indicates surplus capacity of the AHU to cool air, on the basis of information indicating the state of the AHU. The control section controls the operating frequency of the power inverter, to decrease the flow rate of the fed chilled water if the degree of surplus is not lower than the specified threshold, and to increase the flow rate if the degree of surplus is lower than the specified threshold.

Claims

1. A chilled water circulation system comprising:

a thermal source that cools chilled water to a specified temperature;

at least one AHU (Air Handling Unit), which is an air conditioner that cools air by heat exchange with the chilled water;

a pump that feeds the chilled water from the thermal source to the AHU, the chilled water having a flow rate corresponding to an operating frequency of a power inverter; and

a control section configured such that;

a degree of surplus, indicating the surplus capacity of the AHU to cool air, is calculated on the basis of information indicating the state of the AHU;

operating frequency of the power inverter is controlled to decrease the flow rate of the chilled water fed out from the pump when the degree of surplus is equal to or higher than a specified threshold, and to increase the flow rate of the chilled water fed out from the pump when the degree of surplus is smaller than the specified threshold.

2. The chilled water circulation system according to claim 1, further comprising a two-way valve that controls the flow rate of the chilled water flowing in the AHU, and a fan that blows the air to be heat-exchanged in the AHU, wherein information indicating the state of the AHU is at least one or more of the following:

a degree of opening of the two-way valve, a rotating frequency of the fan, or an air temperature difference between a temperature set for the air released from the AHU and a measured temperature of the air, or a combination thereof.

3. The chilled water circulation system according to claim 2, the control section is configured to control the degree of opening of the two-way valve such that an outlet temperature, which is the measured temperature of the air released from the AHU, is equal to a desired value set for the outlet temperature.

4. The chilled water circulation system according to claim 2, wherein the control section is configured to control the operating frequency of the fan such that the temperature in a specific section where the AHU is arranged is lower than a specified set threshold.

5. The chilled water circulation system according to any one of claims 2 to 4 claim 2, comprising a plurality of AHUs, wherein the AHUs are separately arranged in a plurality of sections, and wherein the control section is configured to perform control such that when at least either the respective degrees of opening of two-way valves or the respective rotating frequencies of fans satisfy upper limit threshold in all the AHUs arranged in the sections, the flow rate of the chilled water fed out from the pump is increased.

6. The chilled water circulation system according to claim 2, comprising a plurality of AHUs, wherein the AHUs are separately arranged in a plurality of sections, and wherein the control section is configured to perform control such that when at least either the respective degrees of opening of two-way valves or the respective rotating frequencies of fans satisfy corresponding upper limit threshold in a certain number of the AHUs arranged in the sections, the flow rate of the chilled water fed out from the pump is increased.

7. The chilled water circulation system according to claim 1, comprising a temperature sensor that measures the temperature in a room where the AHUs are provided, wherein the control section is configured to perform control such that when the temperature in the room measured by the temperature sensor exceeds a temperature threshold, the flow rate of the chilled water fed out from the pump is increased.

8. The chilled water circulation system according to claim 7, wherein the control section is configured to perform control such that, if the degree of surplus is not lower than the specified threshold even after the room-air temperature measured by the temperature sensor exceeds the temperature threshold, the flow rate of the chilled water fed out from the pump is increased after a lapse of a specified period.

9. The chilled water circulation system according to claim 7, wherein the control section is configured to perform control such that if the room-air temperature measured by the temperature sensor exceeds the alarm threshold, which is higher than the temperature threshold, a target temperature for the chilled water cooled by the thermal source/thermal sources is altered to a specific temperature, which is lower than the specified temperature.

10. The chilled water circulation system according to claim 1, wherein the control section is configured to perform control such that in a case where the operating frequency of the power inverter is controlled so that a target pressure for the chilled water fed out from the pump is equal to a specified pressure, the flow rate of the chilled water is increased or decreased by altering a pressure setting, instead of controlling the operating frequency of the power inverter.

11. The chilled water circulation system according to claim 1, wherein the control section is configured such that the operating frequency of the power inverter is controlled so that the target pressure of the chilled water fed out from the pump is equal to the specified pressure, and such that control for decreasing the flow rate of the chilled water is performed by altering the specified pressure after a specified interval of control and the specified pressure after the alteration is stored.

12. The chilled water circulation system according to claim 1, wherein the control section is configured such that the operating frequency of the power inverter is controlled so that a target value for a chilled water temperature difference between a feed temperature, which is the temperature of the chilled water fed to the AHU, and a return temperature, which is the temperature of the chilled water flowing out from the AHU, is equal to a specified temperature difference, and such that control for decreasing the flow rate of the chilled water is performed by altering the specified pressure after a specified interval of control and the specified pressure difference after the alteration is stored.

13. The chilled water circulation system according to claim 2, wherein the control section is configured to calculate:

1−

(the average value of the degrees of opening of the two-way valves);

1−

[the average value of (the rotating frequencies of the fans/the maximum frequency)]; and

the average value of (the set temperatures−

the measured temperatures), and to obtain at least one of these averages as the degree of surplus.

14. The chilled water circulation system according to claim 13, wherein the plurality of AHUs are arranged separately in a sectioned space, and wherein the degree of surplus is obtained on the basis of the AHU arranged in each of the sections.

15. The chilled water circulation system according to claim 13, wherein the control section is configured such that, if the degree of surplus is 1−

(the average value of the degrees of opening of the two-way valves), or 1−

[the average value of (the rotating frequencies of the fans/the maximum frequency)], the specified threshold of the degree of surplus is set to (the number of AHUs for normal use/(the number of AHUs for normal use+the number of AHUs for backup use).

16. The chilled water circulation system according to claim 1, wherein the control section is configured such that, when the degree of surplus is lower than the specified threshold, an operation setting used for each of the corresponding pumps is stored, and wherein, when the flow rate of the chilled water fed out from the pump is decreased in the vicinity of the operation setting that is stored, the amount by which the flow rate of the chilled water is decreased is made smaller than that used during the previous control.

17. The chilled water circulation system according to claim 1, further comprising:

a feed header, into which the chilled water fed out from the thermal source flows, and a return header, which feeds out the chilled water that has flowed into the thermal source;

a primary chilled water circuit that connects the thermal source, the feed header, and the return header so that the chilled water can circulate; and

secondary chilled water pipes that connects the feed header, the AHU and the return header so that the chilled water can circulate,

wherein the pump comprises;

a primary pump that feeds out the chilled water from the thermal source to the feed header; and

a secondary pump that feeds the chilled water having a flow rate corresponding to the operating frequency of the power inverter, from the feed header to the AHU.