Adsorption type refrigeration development data center waste heat recovery system

Abstract

The invention discloses an adsorption type refrigeration development data center waste heat recovery system, and relates to the technical field of waste heat recovery, the adsorption type refrigeration development data center waste heat recovery system comprises a plurality of liquid cooling racks, and each liquid cooling rack is provided with a server and a water-cooling cold plate on a central processing unit; the at least one rack water heat exchanger is used for transferring heat collected from the liquid cooling rack to inlet water of a building cooling system; an intermediate heat exchanger for partially recovering heat discharged by the liquid cooling rack; the steam compression cooling machines are used for providing cooling water for the inter-row cooling units; and the adsorption type cooling machine is used for driving a refrigeration process by utilizing waste heat discharged by the liquid cooling rack and generating cooling water to be supplied to the inter-row cooling unit. By introducing the adsorption type refrigeration technology, waste heat of the data center can be used for driving the refrigeration process, so that extra cooling capacity is generated, consumption of external energy is reduced, and the overall energy utilization efficiency of the data center can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery, and in particular to a waste heat recovery system for a data center using adsorption refrigeration. Background Art

[0002] With the rapid development of technologies such as cloud computing, big data, and artificial intelligence, the scale and number of data centers are growing rapidly. As core facilities for information processing, data centers account for a significant proportion of global electricity consumption, and this proportion continues to rise. According to literature 1, the total electricity consumption of China's data centers reached 160 billion kWh in 2018, accounting for 2.5% of the country's total electricity consumption; it is expected that by 2030, this figure may exceed 400 billion kWh. The main source of energy consumption in data centers is servers and other IT equipment, which generate a lot of heat during operation and need to be dissipated through cooling systems to ensure normal operation.

[0003] Traditional data center cooling methods mainly rely on air cooling or water cooling systems, but these methods are often inefficient and have energy waste problems. For example, data center waste heat is usually discharged directly into the environment without being effectively utilized. This not only increases operating costs, but also has a negative impact on the environment. Therefore, improving data center energy efficiency and effectively utilizing waste heat has become one of the focuses of current research. Summary of the invention

[0004] In view of the problems existing in the waste heat recovery of data centers using existing adsorption refrigeration, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is that the generated waste heat cannot be utilized.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides an adsorption refrigeration data center waste heat recovery system, which includes:

[0008] multiple liquid cooling racks, each equipped with water-cooled cold plates on servers and central processing units;

[0009] at least one rack water heat exchanger for transferring heat collected from the liquid cooled racks to incoming water of a building cooling system;

[0010] An intermediate heat exchanger, used for partially recovering the heat discharged by the liquid cooling rack;

[0011] one or more vapor compression coolers to provide cooling water to the inter-row cooling units;

[0012] an adsorption chiller that utilizes waste heat from the liquid cooling rack to drive a refrigeration process and produces cooling water for the row cooling unit;

[0013] a wet cooling tower for discharging heat generated by the adsorption chiller condenser;

[0014] one or more in-row cooling units for cooling the air-cooled server racks;

[0015] One or more fans and pumps are used to support the operation of the cooling system.

[0016] As a preferred solution of the adsorption refrigeration for data center waste heat recovery system of the present invention, it also includes an energy balance model for calculating the temperature of warm water discharged from the liquid cooling rack, the energy balance model is based on the water temperature entering the liquid cooling rack, the total heat dissipation of the server, the total water flow, the density and specific heat capacity of water;

[0017] The energy balance model can also predict the average CPU temperature of the liquid cooling server according to the change of the server inlet water temperature, wherein the calculation formula is expressed as:

[0018]

[0019] Where A1 = 28.81 and A2 = 0.88 are applicable to the server water inlet temperature scope;

[0020] The energy balance model provides the temperature of the exhaust warm water, which is specifically expressed as:

[0021]

[0022] In the formula, and are the inlet and outlet temperatures of water, is the sum of the heat dissipated by all liquid cooling servers. is the total flow of all servers, ρ w is the density of water, C p,w is the specific heat of water.

[0023] As a preferred solution of the adsorption refrigeration system for data center waste heat recovery according to the present invention, the adsorption cooling machine includes a high temperature cycle, a medium temperature cycle and a low temperature cycle, wherein:

[0024] A high temperature cycle connects the generator of the adsorption chiller to the exhaust water flow of the liquid cooling rack;

[0025] The medium temperature cycle connects the condenser of the adsorption chiller to the wet cooling tower to provide heat discharge;

[0026] The low temperature cycle is responsible for producing cooling water, which is supplied to the row cooling units installed in the air-cooled server racks;

[0027] The adsorption chiller and the steam compression chiller form an energy balance expressed as:

[0028]

[0029] In the formula, and are the cooling loads on the evaporators of the adsorption chiller and the vapor compression chiller, respectively, and α is a load sharing factor varying between 0 and 1.

[0030] As a preferred solution for the adsorption refrigeration waste heat recovery system for a data center described in the present invention, it also includes a heat recovery system, which transfers the waste heat discharged from the liquid cooling rack to the water flow leaving the adsorption cooler generator through an intermediate heat exchanger to increase the temperature on the generator side and drive adsorption cooling.

[0031] As a preferred solution for the adsorption refrigeration of the data center waste heat recovery system of the present invention, it also includes: a cost-benefit analysis system for evaluating the energy saving efficiency, operating expense savings and carbon dioxide emission penalty cost reduction of the new cooling system relative to the existing infrastructure;

[0032] The cost-benefit analysis system satisfies the formula:

[0033]

[0034] LCC=CAPEX+OPEX+CO2Cost;

[0035] Where OPRX OS is the annual operating expenditure of the original system, OPEX NS is the annual operating expense of the new system.

[0036] As a preferred solution for the adsorption refrigeration of the data center waste heat recovery system of the present invention, it also includes a cost recovery period calculation method for determining the shortest time required to make up for the capital expenditure from the savings in operating expenses. The method is based on the profit obtained by using the adsorption chiller and the cost of the initial investment. The cost recovery period CPP satisfies the formula:

[0037]

[0038] In the formula, CAPEX is the new capital expenditure and SAVINGS is the annual operating expenditure savings.

[0039] As a preferred solution of the adsorption refrigeration for data center waste heat recovery system of the present invention, it also includes: a flow network model for simulating an air cooling infrastructure with five racks and two inter-row cooling units, and the flow network model is used to predict the temperature distribution at different locations in the air-cooled data center and the fan power consumption in the inter-row cooling unit;

[0040] The input parameters of the flow network model include: the total air flow and water flow of the IRCU, the cooling water temperature entering the IRCU, and the total heat load distributed in all servers.

[0041] As a preferred solution for the adsorption refrigeration of the present invention to carry out the waste heat recovery system of the data center, it also includes: a Gordon-Ng single equation model for simulating the performance of the vapor compression chiller, which is based on the heat load of the chiller evaporator, the cooling water temperature generated by the chiller evaporator, the ambient air temperature entering the VCR chiller condenser, and the power consumption of the chiller in the compressor and the water circulation pump;

[0042] The Gordon-Ng single equation model simulates the non-standard performance of an adsorption chiller for a heat-driven chiller, specifically expressed as:

[0043]

[0044] In the formula, represents the cooling load on the chiller evaporator, is the waste heat added to the generator side, is the inlet temperature of hot water on the HT side, and is the inlet and outlet temperature of the LT cycle, It is the inlet water temperature supplied to the MT side of the wet cooling tower.

[0045] In a second aspect, an embodiment of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the processor executes the computer program, it implements any step of the above-mentioned adsorption refrigeration to carry out the data center waste heat recovery system.

[0046] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, any step of the above-mentioned adsorption refrigeration to carry out the data center waste heat recovery system is implemented.

[0047] The beneficial effects of the present invention are as follows: by introducing adsorption refrigeration technology, the waste heat of the data center can be used to drive the refrigeration process, thereby generating additional cooling capacity, which can not only reduce the consumption of external energy, but also improve the overall energy efficiency of the data center; the adsorption refrigeration system can utilize energy that was originally regarded as waste heat, reducing the demand for external cooling resources, thereby reducing power consumption and related operating costs. At the same time, due to the reduction in the use of mechanical cooling equipment, maintenance costs will also decrease accordingly.

[0048] By effectively recovering and utilizing the waste heat generated by data centers, greenhouse gas emissions can be significantly reduced. This is of great significance for addressing climate change and achieving sustainable development goals; the adsorption refrigeration system has a simple structure and no complex mechanical parts, so the failure rate is relatively low. In addition, the system can operate stably within different temperature ranges, enhancing the reliability and stability of the entire cooling system. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0050] Figure 1 Block diagram of a data center waste heat recovery system for adsorption cooling. DETAILED DESCRIPTION

[0051] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0052] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0053] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0054] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0055] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0056] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] Example 1

[0058] Reference Figure 1 , which is the first embodiment of the present invention, provides an adsorption refrigeration data center waste heat recovery system, comprising:

[0059] multiple liquid cooling racks, each equipped with water-cooled cold plates on servers and central processing units;

[0060] at least one rack water heat exchanger for transferring heat collected from the liquid cooled racks to incoming water of a building cooling system;

[0061] An intermediate heat exchanger, used for partially recovering the heat discharged by the liquid cooling rack;

[0062] one or more vapor compression coolers to provide cooling water to the inter-row cooling units;

[0063] an adsorption chiller that utilizes waste heat from the liquid cooling rack to drive a refrigeration process and produces cooling water for the row cooling unit;

[0064] a wet cooling tower for discharging heat generated by the adsorption chiller condenser;

[0065] one or more in-row cooling units for cooling the air-cooled server racks;

[0066] One or more fans and pumps are used to support the operation of the cooling system.

[0067] Also included is an energy balance model for calculating the temperature of warm water discharged from the liquid cooling rack, the energy balance model being based on the temperature of water entering the liquid cooling rack, the total heat dissipation of the server, the total amount of water flow, the density and specific heat capacity of water;

[0068] The energy balance model can also predict the average CPU temperature of the liquid cooling server according to the change of the server inlet water temperature, wherein the calculation formula is expressed as:

[0069]

[0070] Where A1 = 28.81 and A2 = 0.88 are applicable to the server water inlet temperature scope;

[0071] The energy balance model provides the temperature of the exhaust warm water, which is specifically expressed as:

[0072]

[0073] In the formula, and are the inlet and outlet temperatures of water, is the sum of the heat dissipated by all liquid cooling servers. is the total flow of all servers, ρ w is the density of water, C p,w is the specific heat of water.

[0075] The adsorption cooling machine includes a high temperature cycle, a medium temperature cycle and a low temperature cycle, wherein:

[0076] A high temperature cycle connects the generator of the adsorption chiller to the exhaust water flow of the liquid cooling rack;

[0077] The medium temperature cycle connects the condenser of the adsorption chiller to the wet cooling tower to provide heat discharge;

[0078] The low temperature cycle is responsible for producing cooling water, which is supplied to the row cooling units installed in the air-cooled server racks;

[0079] An air cooling infrastructure with five racks and two inter-row cooling units (IRCUs) was simulated using a previously experimentally validated flow network model (FNM). The five rack systems housed 125 1U servers generating a maximum of 50 kW of heat. FNM uses a zoning approach to predict the temperature at different locations within an air-cooled data center. The model inputs include: the total airflow volume of the IRCUs and water flow Cooling water temperature entering IRCU and the total heat load distributed across all servers Given these inputs, the model gives: Cold (front) room and hot (back) room Air temperature distribution, IRCU warm water temperature Cold air supply to IRCU and hot air return Temperature and power consumption of the fan in the RCU As The function of was experimentally determined in our previous work as follows [5, 37]:

[0081]

[0082] where NIRCU is the number of inter-row cooling units. The input and output parameters of the air-cooled rack FNM [5,37]. The heat generated by the air-cooled server rack in the new system (NS) is calculated by specifying the temperature The cooling water is emitted from two sources:

[0083] The adsorption chiller and the steam compression chiller form an energy balance expressed as:

[0084]

[0085] In the formula, and are the cooling loads on the evaporators of the adsorption chiller and the vapor compression chiller, respectively, and α is a load sharing factor varying between 0 and 1.

[0086] Also included is a heat recovery system that transfers waste heat discharged from the liquid cooling rack to the water flow leaving the adsorption chiller generator through an intermediate heat exchanger to increase the temperature on the generator side and drive adsorption cooling.

[0087] including a cost-benefit analysis system for evaluating the energy savings efficiency, operating expense savings, and carbon dioxide emission penalty cost reduction of the new cooling system relative to the existing infrastructure;

[0088] The cost-benefit analysis system satisfies the formula:

[0089]

[0090] LCC=CAPEX+OPEX+CO2Cost;

[0091] Where OPRX OS is the annual operating expenditure of the original system, OPEX NS is the annual operating expense of the new system.

[0092] A cost payback period calculation method is also included for determining the shortest time required to recover capital expenditures from savings in operating expenditures, the method being based on the profit obtained from using the adsorption chiller and the cost of the initial investment, the cost payback period CPP satisfying the formula:

[0093]

[0094] In the formula, CAPEX is the new capital expenditure and SAVINGS is the annual operating expenditure savings.

[0095] Also included is a flow network model for simulating an air cooling infrastructure with five racks and two row cooling units, the flow network model being used to predict temperature distribution at different locations within the air-cooled data center and fan power consumption within the row cooling units;

[0096] The input parameters of the flow network model include: the total air flow and water flow of the IRCU, the cooling water temperature entering the IRCU, and the total heat load distributed in all servers.

[0097] Also included is a Gordon-Ng single-equation model for simulating the performance of a vapor compression chiller based on the heat load of the chiller evaporator, the temperature of the cooling water produced by the chiller evaporator, the ambient air temperature entering the VCR chiller condenser, and the chiller power consumption in the compressor and water circulation pump;

[0098] The Gordon-Ng single equation model simulates the non-standard performance of an adsorption chiller for a heat-driven chiller, specifically expressed as:

[0099]

[0100] In the formula, represents the cooling load on the chiller evaporator, is the waste heat added to the generator side, is the inlet temperature of hot water on the HT side, and is the inlet and outlet temperature of the LT cycle, It is the inlet water temperature supplied to the MT side of the wet cooling tower.

[0101] In summary, by introducing adsorption cooling technology, the waste heat of the data center can be used to drive the cooling process, thereby generating additional cooling capacity, which can not only reduce the consumption of external energy, but also improve the overall energy efficiency of the data center; the adsorption cooling system can utilize energy that was originally regarded as waste heat, reducing the demand for external cooling resources, thereby reducing electricity consumption and related operating costs. At the same time, due to the reduction in the use of mechanical cooling equipment, maintenance costs will also decrease accordingly.

[0102] By effectively recovering and utilizing the waste heat generated by data centers, greenhouse gas emissions can be significantly reduced. This is of great significance for addressing climate change and achieving sustainable development goals; the adsorption refrigeration system has a simple structure and no complex mechanical parts, so the failure rate is relatively low. In addition, the system can operate stably within different temperature ranges, enhancing the reliability and stability of the entire cooling system.

[0103] Example 2

[0104] This embodiment also provides a computer device suitable for implementing a waste heat recovery system for a data center using adsorption refrigeration, including a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the waste heat recovery system for a data center using adsorption refrigeration as proposed in the above embodiment.

[0105] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0106] This embodiment also provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the adsorption refrigeration and data center waste heat recovery system as proposed in the above embodiment.

[0107] The storage medium proposed in this embodiment and the data storage system proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be found in the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0108] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An adsorption refrigeration data center waste heat recovery system, characterized by: include, multiple liquid cooling racks, each equipped with water-cooled cold plates on servers and central processing units; at least one rack water heat exchanger for transferring heat collected from the liquid cooled racks to incoming water of a building cooling system; An intermediate heat exchanger, used for partially recovering the heat discharged by the liquid cooling rack; one or more vapor compression chillers to provide cooling water to the inter-row cooling units; an adsorption chiller that utilizes waste heat from the liquid cooling rack to drive a refrigeration process and produces cooling water for the row cooling unit; a wet cooling tower for discharging heat generated by the adsorption chiller condenser; one or more in-row cooling units for cooling the air-cooled server racks; One or more fans and pumps are used to support the operation of the cooling system.

2. The adsorption refrigeration data center waste heat recovery system according to claim 1, characterized in that: Also included is an energy balance model for calculating the temperature of warm water discharged from the liquid cooling rack, the energy balance model being based on the temperature of water entering the liquid cooling rack, the total heat dissipation of the server, the total amount of water flow, the density and specific heat capacity of water; The energy balance model can also predict the average CPU temperature of the liquid cooling server according to the change of the server inlet water temperature, wherein the calculation formula is expressed as: Where A1 = 28.81 and A2 = 0.88 are applicable to the server water inlet temperature scope; The energy balance model provides the temperature of the exhaust warm water, which is specifically expressed as: In the formula, and are the inlet and outlet temperatures of water, is the sum of the heat dissipated by all liquid cooling servers. is the total flow of all servers, ρ w is the density of water, C p,w is the specific heat of water.

3. The adsorption refrigeration data center waste heat recovery system according to claim 2, characterized in that: The adsorption cooling machine includes a high temperature cycle, a medium temperature cycle and a low temperature cycle, wherein: A high temperature cycle connects the generator of the adsorption chiller to the exhaust water flow of the liquid cooling rack; The medium temperature cycle connects the condenser of the adsorption chiller to the wet cooling tower to provide heat discharge; The low temperature cycle is responsible for producing cooling water, which is supplied to the row cooling units installed in the air-cooled server racks; The adsorption chiller and the steam compression chiller form an energy balance expressed as: In the formula, and are the cooling loads on the evaporators of the adsorption chiller and the vapor compression chiller, respectively, and α is a load sharing factor varying between 0 and 1.

4. The adsorption refrigeration data center waste heat recovery system according to claim 3, characterized in that: Also included is a heat recovery system that transfers waste heat discharged from the liquid cooling rack to the water flow leaving the adsorption chiller generator through an intermediate heat exchanger to increase the temperature on the generator side and drive adsorption cooling.

5. The adsorption refrigeration data center waste heat recovery system according to claim 4, characterized in that: Also included is a cost-benefit analysis system for evaluating the energy saving efficiency, operating expense savings, and reduction in carbon dioxide emission penalty costs of said new cooling system relative to existing infrastructure; The cost-benefit analysis system satisfies the formula: LCC=CAPEX+OPEX+CO2Cost; Where OPRX OS is the annual operating expenditure of the original system, OPEX NS is the annual operating expense of the new system.

6. The adsorption refrigeration data center waste heat recovery system according to claim 5, characterized in that: A cost payback period calculation method is also included for determining the shortest time required to recover capital expenditures from savings in operating expenditures, the method being based on the profit obtained from using the adsorption chiller and the cost of the initial investment, the cost payback period CPP satisfying the formula: In the formula, CAPEX is the new capital expenditure and SAVINGS is the annual operating expenditure savings.

7. The adsorption refrigeration data center waste heat recovery system according to claim 6, characterized in that: Also included is a flow network model for simulating an air cooling infrastructure with five racks and two row cooling units, the flow network model being used to predict temperature distribution at different locations within the air-cooled data center and fan power consumption within the row cooling units; The input parameters of the flow network model include: the total air flow and water flow of the IRCU, the cooling water temperature entering the IRCU, and the total heat load distributed in all servers.

8. The adsorption refrigeration data center waste heat recovery system according to claim 7, characterized in that: Also included is a Gordon-Ng single-equation model for simulating the performance of a vapor compression chiller based on the heat load of the chiller evaporator, the temperature of the cooling water produced by the chiller evaporator, the ambient air temperature entering the VCR chiller condenser, and the chiller power consumption in the compressor and water circulation pump; The Gordon-Ng single equation model simulates the non-standard performance of an adsorption chiller for a heat-driven chiller, specifically expressed as: In the formula, represents the cooling load on the chiller evaporator, is the waste heat added to the generator side, is the inlet temperature of hot water on the HT side, and is the inlet and outlet temperature of the LT cycle, It is the inlet water temperature supplied to the MT side of the wet cooling tower.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of implementing the data center waste heat recovery system using adsorption refrigeration as described in any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of implementing a data center waste heat recovery system using adsorption refrigeration as described in any one of claims 1 to 8 are implemented.

Images