Refrigerating system and refrigerating method of data center machine room and data center
By introducing cooling tanks and electric valves into the refrigeration system of the data center computer room, the problem of interruption of cold source supply when the cooling unit is shut down is solved, and the stable operation and efficient refrigeration effect of the refrigeration system are achieved.
Patent Information
- Application Number
- CN202411803400.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-09
- Publication Date
- 2025-04-25
AI Technical Summary
The heat generated by the equipment in the data center computer room is difficult to effectively dissipate, resulting in excessive temperature and affecting the normal operation of the equipment. How to improve the refrigeration effect and stability has become a technical problem that needs to be solved urgently.
A refrigeration system in the data center computer room is designed, including a cooling unit, a cooling tank, a ring network, a liquid-cooled refrigeration module and an air-cooled refrigeration module. By monitoring the operating status of the cold unit, if the cold unit is in a shutdown state, a cold storage tank is used to provide a cold source to the ring network, thereby ensuring that the cold source is continuously provided to the refrigeration module.
It can maintain the stable operation of the refrigeration system when the cooling unit is shut down, improve the refrigeration effect and stability of the data center computer room, and reduce the investment cost of the refrigeration system.
Smart Images
Figure CN119893928A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the technical field of data centers, and in particular to the technical field of refrigeration of data centers, and specifically to a refrigeration system and a refrigeration method for a computer room of a data center, and a data center. Background Art
[0002] With the rapid development of Internet technology, the demand for data centers is increasing. The data center room includes not only computer systems and supporting equipment, but also redundant data communication connection equipment, environmental control equipment, monitoring equipment and various safety devices. The various devices included in the data center room will generate a lot of heat during operation. If the heat generated is not dissipated in time through the refrigeration system, the equipment included in the data center room will malfunction due to excessive temperature, affecting the normal operation of the data center. Therefore, how to improve the refrigeration effect and refrigeration stability of the data center room has become a technical problem that needs to be solved urgently. Summary of the invention
[0003] According to a first aspect of the present disclosure, a refrigeration system for a computer room in a data center is provided, the refrigeration system comprising a cold unit, a cold storage tank, a ring network, a liquid-cooled refrigeration module and an air-cooled refrigeration module; the cold unit and the cold storage tank are connected to the ring network to provide a cold source to the ring network; the ring network is connected to the liquid-cooled refrigeration module and the air-cooled refrigeration module to provide a cold source to the liquid-cooled refrigeration module and the air-cooled refrigeration module.
[0004] According to a second aspect of the present disclosure, a cooling method for a computer room in a data center is provided, comprising: monitoring the operating status of a cold unit in a refrigeration system of the computer room in the data center; in response to determining that the operating status is a shutdown state, opening an electric valve in the refrigeration system to provide a cold source to a ring network in the refrigeration system through a cold storage tank in the refrigeration system, the electric valve being located between the cold storage tank and the ring network; providing the cold source in the ring network to a liquid-cooled refrigeration module and an air-cooled refrigeration module in the refrigeration system to cool the computer room in the data center through the liquid-cooled refrigeration module and the air-cooled refrigeration module.
[0005] According to a third aspect of the present disclosure, a data center is provided, including a data center computer room and the refrigeration system in the above embodiment.
[0006] According to a fourth aspect of the present disclosure, an electronic device is provided, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method as described above.
[0007] According to a fifth aspect of the present disclosure, a non-transitory computer-readable storage medium storing computer instructions is provided, wherein the computer instructions are used to cause the computer to execute the method as described above.
[0008] According to a sixth aspect of the present disclosure, a computer program product is provided, comprising a computer program, wherein the computer program implements the method as described above when executed by a processor.
[0009] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present disclosure.
[0011] Figure 1 is a schematic diagram according to a first embodiment of the present disclosure;
[0012] Figure 2 is a schematic diagram according to a second embodiment of the present disclosure;
[0013] Figure 3 is a schematic diagram according to a third embodiment of the present disclosure;
[0014] Figure 4 The block diagram is a block diagram of an electronic device used to implement the cooling method for a data center computer room according to an embodiment of the present disclosure. DETAILED DESCRIPTION
[0015] The following is a description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, including various details of the embodiments of the present disclosure to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present disclosure. Similarly, for the sake of clarity and conciseness, the description of well-known functions and mechanisms is omitted in the following description.
[0016] Figure 1 Schematic diagram of the first embodiment of the present disclosure. Figure 1 As shown in , this embodiment shows a structural schematic diagram of a refrigeration system of a data center computer room.
[0017] In this embodiment, the refrigeration system of the data center computer room includes a cold unit 10, a cold storage tank 20, a ring network 30 connected to the cold unit 10 and the cold storage tank 20, a liquid cooling module 40 connected to the ring network 30, and an air cooling module 50.
[0018] In this embodiment, the cold unit 10 and the cold storage tank 20 are used to provide a cold source to the ring network 30, and the ring network 30 is used to provide a cold source to the liquid cooling module 40 and the air cooling module 50, so that the cooling module can perform air cooling and liquid cooling on the data center room according to the received cold source.
[0019] The refrigeration system in this embodiment, on the one hand, uses a liquid cooling module and an air cooling module to simultaneously perform air cooling and liquid cooling on the data center computer room. On the other hand, an additional cold storage tank is provided. When the cold unit cannot provide a cold source to the ring network, the cold storage tank provides the stored cold source to the ring network, and then the ring network provides it to the refrigeration module for cooling.
[0020] That is to say, this embodiment can not only improve the cooling effect of the refrigeration system on the data center computer room, but also ensure that the cold source can be continuously provided to the refrigeration module by providing the cold source stored in the cold storage tank to the ring network when the cold unit is in a shutdown state, thereby improving the stability of the refrigeration system when cooling the data center computer room.
[0021] In this embodiment, the cold unit 10 includes a cooling tower, a cooling pump, a plate heat exchanger and a freezing pump connected in sequence from top to bottom. The cold unit 10 is used to provide a cold source to the ring network 30, and the cold source can be chilled water in a low-temperature state; wherein, the number of cold units 10 in this embodiment can be multiple.
[0022] In this embodiment, the process of the cold unit 10 providing a cold source to the ring network 30 is explained: after receiving the hot water pumped by the cooling water pump, the cooling tower evaporates and dissipates heat, and the obtained cooling water after cooling is transported to the cooling water pump; the cooling water pump pumps the cooling water to the plate heat exchanger, and the plate heat exchanger performs heat exchange and transfers the heat of the cooling water to the chilled water, so that the chilled water reaches the low temperature state required for refrigeration; the plate heat exchanger transports the obtained low-temperature chilled water to the chilling pump, and the chilling pump pumps the low-temperature chilled water to the ring network 30.
[0023] In this embodiment, the cold storage tank 20 is used to store low-temperature chilled water on the one hand, and to provide the stored low-temperature chilled water to the ring network 30 on the other hand.
[0024] In actual application, in order to ensure that the cold unit 10 can continuously provide a cold source to the ring network 30 , the cold unit 10 needs to be equipped with a UPS (Uninterruptible Power Supply) and a battery, which results in a high investment cost.
[0025] In order to solve the problem of high investment cost, this embodiment arranges a cold storage tank 20 on one side of the ring network 30, thereby eliminating the need to equip the cold unit 10 with an uninterruptible power supply and a battery. Even when the cold unit 10 is in a shutdown state (for example, during a power switching process), the cold storage tank 20 replaces the cold unit 10 to provide a cold source to the ring network 30, thereby ensuring the cold source supply of the ring network 30, so that the liquid-cooled refrigeration module 40 and the air-cooled refrigeration module 50 connected to the ring network 30 can operate normally.
[0026] In this embodiment, an electric valve 201 is further provided between the cold storage tank 20 and the ring network 30 .
[0027] In this embodiment, if no low-temperature chilled water is stored in the cold storage tank 20 or the stored low-temperature chilled water is less, the electric valve 201 is controlled to open, and low-temperature cooling water is obtained through the ring network 30. Then, when it is determined that the low-temperature chilled water stored in the cold storage tank 20 meets the preset requirements (for example, when it is determined that the amount of stored low-temperature chilled water is greater than or equal to (the multiplication result between the preset downtime duration and the preset unit time flow rate, it is determined that the preset requirements are met), the electric valve 201 is controlled to close, and the acquisition of low-temperature chilled water through the ring network 30 is stopped.
[0028] In this embodiment, if it is detected that the cold unit 10 is in a shutdown state, the electric valve 201 is controlled to open, so that the stored low-temperature chilled water is provided to the ring network 30 .
[0029] In this embodiment, the ring network 30 is used to provide the low-temperature chilled water provided by the cold unit 10 or the cold storage tank 20 to the liquid-cooled refrigeration module 40 and the air-cooled refrigeration module 50 connected thereto, so that the liquid-cooled refrigeration module 40 performs liquid cooling on the data center computer room and the air-cooled refrigeration module 50 performs air cooling on the data center computer room.
[0030] That is to say, the refrigeration system of the data center computer room of the present embodiment, on the one hand, can greatly improve the refrigeration effect of the data center computer room by simultaneously performing air cooling and liquid cooling on the data center computer room, and on the other hand, a cold storage tank is arranged on one side of the ring network. When the cold unit is not equipped with an uninterruptible power supply and a battery, even if the cold unit is in a shutdown state, the cold storage tank will provide a cold source (i.e., low-temperature chilled water) to the ring network, which can ensure that the refrigeration system continuously cools the data center computer room, thereby improving the operating stability of the data center computer room.
[0031] Figure 2 is a schematic diagram according to the second embodiment of the present disclosure. Figure 2 As shown in , this embodiment shows a schematic diagram of a liquid cooling module and an air cooling module in a refrigeration system of a data center computer room.
[0032] In this embodiment, the refrigeration system includes a cold storage tank, an electric valve, a cold unit, a ring network, a liquid-cooled refrigeration module and an air-cooled refrigeration module; wherein the cold unit and the cold storage tank are used to provide a cold source to the ring network, the ring network is used to provide a cold source to the refrigeration module, and the refrigeration module is used to perform cooling through the cold source.
[0033] Among them, the liquid cooling module in this embodiment is used to perform liquid cooling according to the received cold source, and the air cooling module is used to perform air cooling according to the received cold source.
[0034] The cold storage tank in this embodiment is connected to the ring network through an electric valve. When the cold unit is in a shutdown state, the electric valve will open, and the cold storage tank will provide the stored cold source to the ring network, and then the ring network will provide the cold source to the refrigeration module for refrigeration, thereby achieving the purpose of continuously providing the cold source to the refrigeration module, which can improve the operating stability of the refrigeration system and the data center. In addition, this embodiment does not need to ensure that the cold unit continuously supplies cold to the ring network, and can also reduce the investment cost of the refrigeration system.
[0035] In this embodiment, the liquid cooling module 40 includes a CDU (Coolant Distribution Unit) connected to the ring network 30 .
[0036] In this embodiment, the CDU in the liquid cooling module 40 transports the cold source (i.e., chilled water in a low-temperature state) provided by the ring network 30 to the machines or components on the machines deployed in the cabinet (e.g., the liquid cooling cabinet), thereby achieving the purpose of liquid cooling of the data center computer room.
[0037] In this embodiment, the air-cooling refrigeration module 50 includes a pump cabinet connected to the ring network 30 and a wind wall (ie, a heat exchange end) connected to the pump cabinet.
[0038] In this embodiment, the pump cabinet in the air-cooling refrigeration module 50 first pumps the cold source provided by the ring network 30 to the wind wall, and then the wind wall returns the cold source to the air in the data center room for heat exchange, thereby achieving the purpose of air-cooling the data center room.
[0039] In this embodiment, the liquid cooling module 40 may include multiple CDUs, each CDU is used to perform liquid cooling on the corresponding row of cabinets; the air cooling module 50 may include multiple pump cabinets and multiple wind walls, one pump cabinet corresponds to two wind walls.
[0040] Figure 3 is a schematic diagram according to the third embodiment of the present disclosure. Figure 3 As shown, the cooling method for a data center computer room of this embodiment specifically includes the following steps:
[0041] S301, monitoring the operating status of a cooling unit in a refrigeration system of a data center computer room;
[0042] S302, in response to determining that the operating state is a shutdown state, opening the electric valve to provide a cold source to the ring network in the refrigeration system through the cold storage tank in the refrigeration system, the electric valve being located between the cold storage tank and the ring network;
[0043] S303: Provide the cold source in the ring network to the liquid-cooling refrigeration module and the air-cooling refrigeration module in the refrigeration system, so as to cool the data center computer room through the liquid-cooling refrigeration module and the air-cooling refrigeration module.
[0044] The cooling method for the data center computer room of the present embodiment, when it is determined that the cold unit in the refrigeration system of the data center computer room is in a shutdown state, opens the electric valve located between the cold storage tank and the ring network in the refrigeration system, and provides the cold source (i.e., chilled water in a low-temperature state) stored in the cold storage tank to the ring network, which then provides the obtained cold source to the liquid-cooled refrigeration module and the air-cooled refrigeration module for refrigeration. Therefore, when the cold unit is in a shutdown state, the present embodiment will not stop providing the cold source to the ring network, which can ensure that the liquid-cooled refrigeration module and the air-cooled refrigeration module continue to refrigerate, and can also effectively improve the operating stability of the data center computer room while reducing the cost required for the refrigeration system.
[0045] This embodiment may also include the following: in response to determining that the operating state of the cold unit in the refrigeration system of the data center computer room is normal and the cold source stored in the cold storage tank does not meet the preset requirements, the electric valve is opened to supplement the cold source to the cold storage tank through the ring network.
[0046] Among them, when determining whether the cold source stored in the cold storage tank meets the preset requirements, this embodiment can first obtain the current cold source amount of the cold storage tank, and then compare the obtained current cold source amount with the preset cold source amount threshold. Finally, when it is determined that the obtained cold source amount is less than the preset cold source amount threshold, it is determined that the cold source stored in the cold storage tank does not meet the preset requirements.
[0047] In this embodiment, the preset cold source quantity threshold can be the maximum storage capacity of the cold storage tank; or the multiplication result between the preset downtime duration (for example, the downtime duration of the cold unit obtained in advance when switching the power supply) and the preset unit time flow rate can be used as the preset cold source quantity threshold.
[0048] It can be understood that this embodiment can obtain the amount of cold source stored in the cold storage tank in real time during the cold source replenishment process of the cold storage tank, and then close the electric valve when it is determined that the obtained cold source amount meets the preset requirements, thereby completing the cold source replenishment process.
[0049] According to an embodiment of the present disclosure, the present disclosure also provides an electronic device, a readable storage medium and a computer program product.
[0050] like Figure 4 , is a block diagram of an electronic device for a cooling method for a data center computer room according to an embodiment of the present disclosure. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present disclosure described and / or required herein.
[0051] like Figure 4 As shown, the device 400 includes a computing unit 401, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 402 or a computer program loaded from a storage unit 408 into a random access memory (RAM) 403. In the RAM 403, various programs and data required for the operation of the device 400 can also be stored. The computing unit 401, the ROM 402, and the RAM 403 are connected to each other via a bus 404. An input / output (I / O) interface 405 is also connected to the bus 404.
[0052] A number of components in the device 400 are connected to the I / O interface 405, including: an input unit 406, such as a keyboard, a mouse, etc.; an output unit 407, such as various types of displays, speakers, etc.; a storage unit 408, such as a disk, an optical disk, etc.; and a communication unit 409, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 409 allows the device 400 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.
[0053] The computing unit 401 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 401 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 401 performs the various methods and processes described above, such as a cooling method for a data center computer room. For example, in some embodiments, the cooling method for a data center computer room may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit 408.
[0054] In some embodiments, part or all of the computer program may be loaded and / or installed on the device 400 via the ROM 402 and / or the communication unit 409. When the computer program is loaded into the RAM 403 and executed by the computing unit 401, one or more steps of the cooling method for the data center computer room described above may be executed. Alternatively, in other embodiments, the computing unit 401 may be configured to execute the cooling method for the data center computer room in any other appropriate manner (e.g., by means of firmware).
[0055] Various implementations of the systems and techniques described herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.
[0056] The program code for implementing the method of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a refrigeration device of a general-purpose computer, a special-purpose computer, or other programmable data center computer room, so that when the program code is executed by the processor or controller, the functions / operations specified in the flow chart and / or block diagram are implemented. The program code may be executed entirely on the machine, partially on the machine, partially on the machine as a stand-alone software package and partially on a remote machine, or entirely on a remote machine or server.
[0057] In the context of the present disclosure, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
[0058] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and a pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).
[0059] The systems and techniques described herein may be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), and the Internet.
[0060] A computer system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The relationship between the client and the server is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or a cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services ("Virtual Private Server", or "VPS" for short). The server may also be a server for a distributed system, or a server combined with a blockchain.
[0061] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this document does not limit this.
[0062] The above specific implementations do not constitute a limitation on the protection scope of the present disclosure. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.
Claims
1. A cooling system for a data center computer room, wherein: The refrigeration system includes a cold unit, a cold storage tank, a ring network, a liquid-cooled refrigeration module and an air-cooled refrigeration module; The cold unit and the cold storage tank are connected to the ring network to provide a cold source for the ring network; The ring network is connected to the liquid-cooled refrigeration module and the air-cooled refrigeration module, and is used to provide a cold source to the liquid-cooled refrigeration module and the air-cooled refrigeration module.
2. The refrigeration system according to claim 1, wherein: An electric valve is included between the cold storage tank and the ring network.
3. The refrigeration system according to claim 1, wherein: The liquid-cooling refrigeration module comprises a cooling liquid distribution unit, and the cooling liquid distribution unit is connected to the ring network.
4. The refrigeration system according to claim 1, wherein: The air-cooled refrigeration module includes a pump cabinet and a heat exchange terminal; The pump cabinet is connected to the ring network, and the heat exchange terminal is connected to the pump cabinet.
5. The refrigeration system according to claim 1, wherein: The cold unit includes a cooling tower, a cooling pump, a plate heat exchanger and a refrigeration pump connected in sequence; The refrigeration pump is connected to the ring network.
6. A cooling method for a data center computer room, comprising: Monitor the operating status of the cooling unit in the refrigeration system of the data center room; In response to determining that the operating state is a shutdown state, opening the electric valve in the refrigeration system to provide a cold source to the ring network in the refrigeration system through a cold storage tank in the refrigeration system, wherein the electric valve is located between the cold storage tank and the ring network; Providing the cold source in the ring network to the liquid cooling module and the air cooling module in the refrigeration system, so as to cool the data center computer room through the liquid cooling module and the air cooling module; Wherein, the refrigeration system is the refrigeration system according to any one of claims 1-5.
7. The method according to claim 6, further comprising: In response to determining that the operating state is a normal state and the cold source stored in the cold storage tank does not meet the preset requirements, the electric valve is opened to supplement the cold source to the cold storage tank through the ring network.
8. The method according to claim 7, wherein: The determining that the cold source stored in the cold storage tank does not meet the preset requirements includes: Obtaining the current cold source amount of the cold storage tank; Comparing the current cooling source amount with a preset cooling source amount threshold; When it is determined that the cold source amount is less than the preset cold source amount threshold, it is determined that the cold source stored in the cold storage tank does not meet the preset requirement.
9. A data center, comprising a data center computer room and a refrigeration system according to any one of claims 1 to 5.
10. An electronic device comprising: at least one processor; as well as a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 6 to 8.
11. A non-transitory computer-readable storage medium storing computer instructions, wherein: The computer instructions are used to cause the computer to execute the method according to any one of claims 6 to 8.
12. A computer program product comprising a computer program, which, when executed by a processor, implements the method according to any one of claims 6 to 8.