Energy-saving free refrigeration system

Abstract

The utility model relates to the technical field of energy conservation and emission reduction, and particularly discloses an energy-saving free refrigerating system which comprises a refrigerating unit, a circulating pump set and a cooling tower, the refrigerating unit, the circulating pump set and the cooling tower are circularly connected, and the circulating pump set is connected with cooled equipment; the refrigerating unit consists of a condenser, an evaporator and a compressor; the cooling tower and the refrigerating unit are used for cooling equipment to be cooled through the circulating pump set respectively; according to the utility model, a single operation mode of the refrigerating unit with a unique cold source is changed into a multi-cold-source adjustable operation mode selected according to environment and load changes, and the refrigerating unit is no longer used as a unique cold source providing device; in the independent operation mode of the cooling tower, the cooling tower serves as the only cooling device to independently cool the cooled device, and free refrigeration of compressor-free operation is achieved; the system can adapt to working condition changes of cooled equipment, and the optimal and most energy-saving operation mode is switched.

Description

Technical Field

[0001] The utility model relates to the technical field of energy conservation and emission reduction, in particular to an energy-saving free refrigeration system. Background Art

[0002] Circulating cooling systems are widely used in various fields such as petrochemicals, thermal power, metallurgy, medicine, construction, HVAC, etc., and are an indispensable component for handling the heat load of equipment. Refrigeration units have become the preferred equipment for cold sources in many cooling systems due to their advantages such as low cooling temperature and stable performance. However, the compressor of the refrigeration unit consumes a lot of energy, and the matching chilled water pump and cooling water pump are also high-energy-consuming equipment. In addition, a cooling tower is also required to cool the condenser of the refrigeration unit.

[0003] Cooling towers are often used as independent cold sources, and their energy consumption is also low, but there are requirements for the target temperature and the ambient wet bulb temperature, and the difference is usually not less than 3°C. Considering economic factors, this limit will be higher. When this requirement is not met, the only option is the refrigeration unit. Therefore, the circulating cooling system with the refrigeration unit as the only cold source is widely used for its advantages such as simplicity and ease of control. In this type of system, the refrigeration unit is the only cold source, and there is only one operating mode, namely the refrigeration cycle of the refrigeration unit. Because there is no other replacement cold source, energy-consuming equipment such as the refrigeration unit operates with the cooled equipment under full working conditions. However, in actual operation, there are not many high humidity conditions. In many occasions where cooling towers could have been used for cooling, refrigeration units are still used, which makes the entire system operate in a high-energy-consuming and low-efficiency state in most cases. There is a serious phenomenon of "big horse pulling a small cart".

[0004] In response to the call, we will vigorously promote energy conservation and emission reduction, and accelerate the establishment of a sound green, low-carbon, circular development economic system. Energy conservation research in the field of circulating cooling is everywhere. However, traditional energy conservation research and practical methods have many shortcomings:

[0005] 1. Limited to energy saving of a single device. Equipment manufacturers act independently and only focus on their own equipment without considering the mutual influence and constraints between the equipment in the entire system. It may even result in energy saving of a single device but increase the overall energy consumption of the system.

[0006] 2. Theoretical research that focuses on improving equipment performance lacks practicality. Existing research focuses on how to improve the performance and efficiency of a single device, and the research targets are also some specific parts or modules in the equipment, such as fan efficiency, air duct structure, water pump performance curve, type and material of heat exchange module, etc. Although these studies are also very meaningful, their actual application is relatively complicated and difficult to put into practice.

[0007] 3. The practical means are too single and overly dependent on frequency conversion. Among the energy-saving means that can be truly implemented, frequency conversion control is widely used. Frequency conversion is the first to energy conservation and emission reduction, and frequency conversion seems to have become the pass and symbol of energy conservation and emission reduction. However, frequency conversion is usually only for a single device, and each device has its own frequency conversion, which is unrelated to each other, and it is impossible to achieve energy conservation through joint control of the entire system.

[0008] Traditional circulating cooling systems consume a lot of energy, and traditional energy-saving methods are single and impractical. It is urgent to find a truly effective and practical system energy-saving method to overcome the above difficulties. Utility Model Content

[0009] The purpose of the utility model is to provide an energy-saving free refrigeration system to solve the problems raised in the above background technology.

[0010] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: an energy-saving free refrigeration system, comprising a refrigeration unit, a circulating pump group and a cooling tower, wherein the refrigeration unit, the circulating pump group and the cooling tower are connected in a circulation manner, and the circulating pump group is connected to the cooled equipment; the refrigeration unit is composed of a condenser, an evaporator and a compressor, and the cooling tower and the refrigeration unit cool the cooled equipment respectively through the circulating pump group; the difference between the outlet temperature of the cooling tower and the ambient wet-bulb temperature is defined as the approximation degree, and the lowest approximation degree that can be achieved by the cooling tower is defined as the limit approximation degree.

[0011] Preferably, when the difference between the cooling demand temperature of the cooled equipment and the ambient wet-bulb temperature is greater than or equal to the limit approximation, the cooling tower is provided as a separate cold source to the cooled equipment.

[0012] Preferably, when the difference between the cooling demand temperature of the cooled equipment and the ambient wet-bulb temperature is less than the limit approximation, the refrigeration unit is started; the refrigeration unit and the cooling tower perform combined cooling, and the cooling tower serves as the main cooling equipment to provide a cold source for the cooled equipment, and at the same time serves as an auxiliary equipment to cool the condenser of the refrigeration unit.

[0013] Preferably, when the difference between the hot fluid temperature of the cooled equipment and the ambient wet-bulb temperature is less than or equal to the limit approximation, the refrigeration unit is provided to the cooled equipment as a separate cold source, and the cooling tower is used as an auxiliary equipment to cool the condenser of the refrigeration unit.

[0014] Preferably, the circulating pump group includes a main circulating water pump, a chiller refrigeration water pump, and a chiller cooling water pump, and the chiller refrigeration water pump and the chiller cooling water pump are intermittently operated in conjunction with the refrigeration unit.

[0015] Preferably, the cooling tower is an open cooling tower or a closed cooling tower.

[0016] Compared with the prior art, the beneficial effects of the utility model are as follows: the utility model changes the single operation mode in which the refrigeration unit is the only cold source into an adjustable operation mode with multiple cold sources selected according to the environment and load changes. The refrigeration unit is no longer used as the only cold source to provide equipment, but as an emergency or supplement under high temperature conditions: in the independent operation mode of the cooling tower, the cooling tower is the only cooling equipment to provide cooling for the cooled equipment alone, realizing "free cooling" without compressor operation; it can adapt to the changes in the working conditions of the cooled equipment, and switch to the optimal and most energy-saving operation mode at any time, thereby improving the adaptability and flexibility of the system; it makes maximum use of the cooling capacity and advantages of the cooling tower, greatly shortens the operation time of the refrigeration unit, reduces system energy consumption and saves operating costs under the premise of high stability and high operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the utility model;

[0018] Figure 2 A schematic diagram of a "three-mode" system of an embodiment;

[0019] Figure 3 This is a schematic diagram of the "three-mode" system of the embodiment - the main circulation pump also serves as a chilled water pump;

[0020] Figure 4 This is a schematic diagram of the "three-mode" system of the embodiment - the self-circulation of the cooled equipment;

[0021] Figure 5 is a schematic diagram of the "dual mode" system of the embodiment;

[0022] Figure 6 This is a simplified system diagram of the "dual mode" embodiment - the main circulation pump also serves as a chilled water pump;

[0023] Figure 7 This is a simplified system diagram of the "dual mode" embodiment - the chilled water pump or the cooling water pump also serves as the main circulation pump;

[0024] Figure 8 Example "dual mode" system - schematic diagram of self-circulation of cooled equipment;

[0025] Numbers in the figure: 1, refrigeration unit; 11, condenser; 12, evaporator; 13, compressor; 2, circulation pump group; 21, main circulation water pump; 22, chiller refrigeration water pump; 23, chiller cooling water pump; 3, cooling tower; 4, cooled equipment. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0027] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "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 be a mechanical connection or an electrical connection; it can be 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.

[0029] See also Figure 1 The utility model provides a technical solution: an energy-saving free refrigeration system, comprising a refrigeration unit 1, a circulating pump group 2 and a cooling tower 3, wherein the refrigeration unit 1, the circulating pump group 2 and the cooling tower 3 are cyclically connected, and the circulating pump group 2 is connected to a cooled device 4; the refrigeration unit 1 is composed of a condenser 11, an evaporator 12 and a compressor 13, and the cooling tower 3 and the refrigeration unit 1 cool the cooled device 4 respectively through the circulating pump group 2; the difference between the outlet temperature of the cooling tower 3 and the ambient wet-bulb temperature is defined as the approximation degree, and the lowest approximation degree that the cooling tower 3 can achieve is defined as the limit approximation degree.

[0030] The limit approximation divides the operation modes of the system into three types: cooling tower independent operation mode, i.e. winter mode, combined operation mode, i.e. transitional season mode, and refrigeration unit independent operation mode, i.e. summer mode. The combined operation mode operates selectively according to the system operation economy.

[0031] There is an independent operation mode of cooling tower 3, which can also be called "free cooling" mode: when the wet-bulb temperature is low and the difference between the target temperature and the wet-bulb temperature is greater than or equal to the limit approximation of cooling tower 3, cooling tower 3 can be used as the only cold source to cool the temperature of the main circulation cooling medium to the target temperature. This mode is mostly operated in winter when the ambient temperature is relatively low, so it can also be called "winter mode". The refrigeration unit 1 is shut down, and only the cooling tower 3 and the main circulation water pump 21 are operated, and the cooling tower 3 directly cools the cooled equipment 4. Compared with the refrigeration unit system, there is no compressor running, and the energy consumption is greatly reduced, so it can also be called "free cooling" mode.

[0032] There is a joint operation mode, that is, the joint operation mode of the cooling tower 3 and the refrigeration unit 1: as the wet-bulb temperature rises, the difference between the target temperature and the wet-bulb temperature is less than the limit approximation, and the difference between the temperature of the hot fluid (the main circulation cooling medium after being heated by the cooled equipment) and the wet-bulb temperature is greater than the limit approximation, the outlet temperature of the cooling tower 3 cannot reach the target temperature, and cannot provide sufficient cold source for the cooled equipment 4. At this time, the refrigeration unit 1 is started, and the cooling tower 3 and the refrigeration unit 1 are jointly cooled. The temperature of the main circulation cooling medium is first cooled to the intermediate temperature by the cooling tower 3, and then cooled to the target temperature by the refrigeration unit 1. At the same time, the cooling tower 3 also provides a cold source for the refrigeration unit 1 to cool the condenser 11. This mode is mostly operated in the transition season of spring and autumn, so it can also be called the "spring and autumn mode" or the "transition season mode".

[0033] There is an independent operation mode of the refrigeration unit 1: when the wet-bulb temperature rises further, the difference between the hot fluid temperature and the wet-bulb temperature is not higher than the limit of approximation, and the cooling tower 3 can no longer cool the main circulation cooling medium and cannot provide a cold source for the cooled equipment 4. The refrigeration unit 1 provides a cold source for the cooled equipment 4 alone, and the cooling tower 3 only serves as an auxiliary cold source of the refrigeration unit 1 to cool the condenser 11. This mode is mostly operated in summer when the temperature is high, so it can also be called "summer mode".

[0034] When the difference between the cooling demand temperature of the cooled equipment 4 and the ambient wet-bulb temperature is greater than or equal to the limit approximation, the cooling tower 3 is provided to the cooled equipment 4 as a separate cold source.

[0035] When the difference between the cooling demand temperature of the cooled equipment 4 and the ambient wet-bulb temperature is less than the limit approximation, the refrigeration unit 1 is started; the refrigeration unit 1 and the cooling tower 3 perform joint cooling, and the cooling tower 3 serves as the main cooling equipment to provide a cold source for the cooled equipment 4, and at the same time serves as an auxiliary equipment to cool the condenser 11 of the refrigeration unit 1.

[0036] When the difference between the hot fluid temperature of the cooled equipment 4 and the ambient wet bulb temperature is less than or equal to the limit approximation, the refrigeration unit 1 is provided as a separate cold source to the cooled equipment 4, and the cooling tower 3 is used as an auxiliary device to cool the condenser 11 of the refrigeration unit 1.

[0037] Furthermore, the circulating pump group 2 includes a main circulating water pump 21, a chiller refrigerating water pump 22, and a chiller cooling water pump 23, and the chiller refrigerating water pump 22 and the chiller cooling water pump 23 are intermittently operated in conjunction with the refrigeration unit 1. According to the different needs of the cooled equipment 4, there are three or two sets of water pump groups in the system. Three sets of water pump groups: the main circulating water pump 21, the chiller refrigerating water pump 22, and the chiller cooling water pump 23, which are independent of each other. There are two cases for two sets of water pump groups: one is the main circulating water pump 21 (which also serves as the chiller refrigerating water pump 22) and the chiller cooling water pump 23; the other is the chiller refrigerating water pump 22 and the chiller cooling water pump 23 (the main circulating water pump 21 is concurrently used by one of the two). In addition, when the cooled equipment 4 is not directly connected to the circulating cooling system, a self-circulating water pump for the cooled equipment 4 is also required.

[0038] Furthermore, the cooling tower 3 is an open cooling tower or a closed cooling tower.

[0039] See also Figures 2 to 8 , describe any one embodiment of the utility model for further explanation:

[0040] The cooling medium of a factory process equipment is water, with a peak heat load of 450kW and a peak flow rate of 160m 3 / h, the target temperature of the cooled equipment is 24℃, with fluctuation ≤±0.5℃, the cooling water temperature difference requirement is 2-3℃, the water inlet pressure of the cooled equipment is 0.2-0.3MPa, with fluctuation ≤±0.01Mpa, and the local ambient wet-bulb temperature is 27.2℃.

[0041] The peak heat load of the cooled equipment is 450kW, and the peak flow rate of process cooling water is 160m 3 / h, cooling from 28℃ to 25±0.5℃. Considering the high stability requirements of the system, the self-circulation of chilled water, and the lack of separate access to the cooling system, the chilled water temperature needs to be lower than the process fluid temperature. The usual chilled water temperature difference of the refrigeration unit is 5℃, so this system is selected according to the chilled water cooling from 24℃ to 21℃, and a medium-temperature refrigeration unit with a cooling capacity of ≥450kW is required. The reason for choosing a medium-temperature refrigeration unit is that the chilled water temperature of a conventional refrigeration unit is too low, only 12-7℃, which is too different from the target temperature and will cause unnecessary waste.

[0042] Select a certain brand of medium-temperature refrigeration unit, compressor power 90kW, chilled water flow 80m 3 / h, temperature difference 24℃-21℃, cooling water flow 107m 3 / h, temperature difference 37℃-32℃.

[0043] The maximum load condition when the cooling tower is running independently is: flow rate 160m 3 / h, temperature difference 28-24℃, wet bulb temperature 21℃. Based on this selection condition, the cooling tower standard condition (37℃ inlet, -32℃ outlet, -28℃ wet bulb) flow rate is 160m 3 / h.

[0044] When the refrigeration unit is running independently, the maximum load condition of the cooling tower is: flow rate 107m 3 / h, temperature difference 37-32℃, wet bulb temperature 27.2℃. Based on this selection condition, the cooling tower standard condition (37℃ inlet -32℃ outlet -28℃ wet bulb) flow rate is 100m 3 / h.

[0045] For easy switching, the standard flow rate of a single unit can be selected to be 60m 3 / h cooling towers, when the refrigeration unit is running independently, two cooling towers are opened to cool the condenser; when the ambient temperature is high during joint operation or independent operation of the cooling tower, all three are opened and run at full load. 3 / h>Required capacity standard condition 160m 3 / h, so the actual maximum wet bulb temperature of the cooling tower operating independently (that is, the starting temperature of the joint operation) can be increased to 21.5℃.

[0046] Main circulation pump group: flow rate 160m 3 / h, head 35m, 1 in use and 1 in reserve;

[0047] Chiller chilled water pump group: flow rate 80m 3 / h, head 16 meters, 1 in use and 1 in reserve;

[0048] Chiller cooling water pump group: flow rate 110m 3 / h, lift 20 meters, 1 in use and 1 in reserve.

[0049] The lift is determined based on the actual on-site layout and piping conditions.

[0050] In this system, the refrigeration unit has an independent refrigeration cycle, and the intermediate cooling device indirectly transfers the cold to the main circulation cooling medium. The intermediate cooling device can be in the form of a mixed water tank or a plate heat exchanger. For economic considerations, this system uses a mixed water tank with a size of 6m 3 It can not only exchange heat but also play the role of stabilizing the pressure and replenishing water in the circulating water tank.

[0051] In addition, the condenser cooling cycle is also equipped with a cooling water mixing tank, which can both regulate the water temperature and stabilize the water pressure.

[0052] See the attached diagram of the “three-mode” system Figure 2 .

[0053] A: Independent operation mode of cooling tower in winter - "free cooling" mode: when the wet-bulb temperature is ≤21℃, close valves D, E, F, G, H, open valves A, B, C, turn off the chiller, chilled water pump and cooling water pump, and only run the main cooling cycle. The cooling tower supplies cold water to the intermediate cooling water tank. The equipment return water T1 directly enters the cooling tower and cools to T2 before returning to the water tank. At this time, the main circulation pump serves as the power pump for the cooling tower and the cooled equipment. As the wet-bulb temperature decreases, the number of fans or spray pumps in operation can be reduced to ensure that the equipment inlet water temperature is within 24℃±0.5.

[0054] The above only includes the main system equipment. In other similar systems, the main circulation pump can be placed either upstream or downstream of the cooling tower, depending on the different needs of the system.

[0055] B: Summer chiller independent operation mode: When the wet bulb temperature is ≥24℃, close valves A, B, H, open valves C, D, E, F, G, start the chiller, cooling tower, main circulation pump, chilled water pump and cooling water pump, and run the main cooling cycle, evaporator refrigeration cycle and condenser cooling cycle. The cooling tower cools the chiller unit, and the chiller unit supplies cold air to the intermediate cooling water tank.

[0056] Main cooling cycle: The main cooling water is delivered by the main circulation pump group, and the cooling capacity of the chiller is obtained through the intermediate cooling water tank to reduce the temperature to T2. The water required by the cooled equipment is directly drawn from the intermediate cooling water tank, and then returned to the intermediate cooling water tank after absorbing heat and heating to T1.

[0057] Refrigeration cycle: The chiller of this system is not directly connected to the main cooling cycle pipeline. The refrigeration cycle is an independent cycle. The chilled water of the chiller is cooled to td2 in the chiller evaporator and then transported to the intermediate cooling water tank by the chiller chilled water pump group. After absorbing heat and heating up, it returns to the chiller evaporator for cooling.

[0058] Cooling cycle: After the cooling water of the chiller absorbs heat in the condenser and rises to tq1, it is transported to the cooling tower by the chiller cooling water pump group to cool down to tq2, and then returns to the condenser to absorb heat again. The cooling tower cools the refrigeration unit, and the cooling water pump at this time serves as the power pump of the cooling tower.

[0059] C: Transition season joint operation mode: When the wet bulb temperature is greater than 21℃ and less than 24℃, close valve D, open valves A, B, C, E, F, G, H, start the chiller, cooling tower, main circulation pump, chilled water pump and cooling water pump, and run the main cooling cycle, evaporator refrigeration cycle and condenser cooling cycle. The cooling tower cools the refrigeration unit and supplies cold to the main cooling cycle, that is, the cooling tower and refrigeration unit supply cold to the intermediate cooling water tank at the same time.

[0060] Main cooling cycle: The main cooling water is delivered by the main circulation pump group and first enters the cooling tower for preliminary cooling to T m , and then the intermediate cooling water tank is used to obtain the cooling capacity of the chiller and cool it down to T2. The water required by the cooled equipment is directly drawn from the intermediate cooling water tank, and after heat exchange and temperature rise to T1, it enters the cooling tower again.

[0061] Refrigeration cycle: The chiller in this system is not directly connected to the main cooling cycle pipeline. The refrigeration cycle is an independent cycle. The chilled water of the chiller is cooled to td2 in the chiller evaporator and then transported to the intermediate cooling water tank by the chiller chilled water pump group. After absorbing heat and heating to td1 (= T2), it returns to the chiller evaporator for cooling.

[0062] Cooling cycle: After the cooling water of the chiller absorbs heat in the condenser and rises to tq1, part of it is transported to the cooling tower by the chiller cooling water pump group to cool down to tq m (=T m ), and the other part directly enters the cooling water mixing tank. After the two are mixed to reach the optimal cooling water temperature tq2, they return to the condenser to absorb heat again.

[0063] In the above cycle, the cooling tower cools the refrigeration unit and supplies cooling to the main cooling cycle. At this time, the cooling water pump and the main circulation pump both serve as the power pumps of the cooling tower. The cooling water pump drives the condenser cooling water, and the main circulation pump drives the main circulation cooling water. The two groups of cooling water with temperatures of tq1 and T1 merge in the equalizing water pipe and then enter the cooling tower. Cooling to the intermediate temperature T m The latter part enters the cooling water mixing tank, and the other part enters the intermediate cooling water tank. The cooling water entering the intermediate cooling water tank is further cooled to the target temperature T2 by the chilled water. The latter part directly enters the main cooling cycle, and the other part returns to the chiller evaporator for cooling. The cooling tower and the chiller simultaneously provide cooling for the intermediate cooling water tank. The water required by the cooled equipment is directly drawn from the intermediate cooling water tank and returned to the cooling tower after heat exchange.

[0064] The above has analyzed the "three-mode" system. In the actual implementation process, it can be appropriately simplified. There are several forms:

[0065] "Three-mode" simplified system - the main circulation pump also serves as the chilled water pump:

[0066] As attached Figure 3As shown. In the conventional non-simplified system, the chiller is not directly connected to the main cooling cycle, there is an independent refrigeration cycle, and there is an intermediate cooling water tank, whose internal stable temperature is the target temperature T2. In the simplified system, the chiller is directly connected to the main cooling cycle, the refrigeration cycle becomes a part of the main cooling cycle, and the main circulation pump also operates as a chilled water pump. The intermediate cooling water tank is changed to a circulating water tank, and the stable temperature is T2 or T1 or T m .

[0067] A: Winter cooling tower independent operation mode - "free cooling" mode: when the wet bulb temperature is ≤21℃, close valves D, E, F, G, H, open valves A, B, C, turn off the chiller and cooling water pump, start the cooling tower and main circulation pump, only run the main cooling cycle, the cooling tower supplies cold to the circulating water tank, and the stable temperature in the water tank is T2.

[0068] B: Summer chiller independent operation mode: When the wet bulb temperature is ≥24℃, close valves A, B, C, H, open valves D, E, F, G, start the chiller, cooling tower, main circulation pump (also serving as chilled water pump) and cooling water pump. The main cooling water, which absorbs heat and heats up in the cooled equipment, first enters the circulating water tank and then enters the chiller evaporator for cooling. The stable temperature in the water tank is T1.

[0069] C: Transition season joint operation mode: When the wet bulb temperature is greater than 21℃ and less than 24℃, close valves C and D, open valves A, B, D, E, F, G, H, start the chiller, cooling tower, main circulation pump (also serving as chilled water pump) and cooling water pump. The cooling water cooled to the intermediate temperature Tm in the cooling tower enters the circulating water tank, and then enters the chiller evaporator for further cooling. The stable temperature in the circulating water tank is T m .

[0070] In the above system, although the refrigeration cycle is simplified, the main cooling cycle has to flow through three major equipment (evaporator, cooled equipment, cooling tower) at one time, so the head requirement is relatively high.

[0071] "Three-mode" system - self-circulation of the cooled equipment:

[0072] In order to ensure the stability of the system and reduce the interference of other equipment on the operation of the cooled equipment, it is sometimes necessary to separate the cooled equipment for self-circulation. Figure 4 As shown:

[0073] A: Winter cooling tower independent operation mode - "free cooling" mode: When the wet bulb temperature is ≤21℃, close valves B, D, E, F, G, H, open valves A and C, turn off the chiller, chilled water pump and cooling water pump, start the cooling tower, main circulation pump and self-circulation pump of the cooled equipment, only run the main cooling cycle and self-circulation of the cooled equipment, and the cooling tower supplies cold water to the cold water tank. The equipment return water T1 enters the cooling tower from the hot water tank and returns to the cold water tank after cooling. At this time, the main circulation pump serves as the power pump of the cooling tower.

[0074] B: Summer chiller independent operation mode: When the wet bulb temperature is ≥24℃, close valves A, B, C, H, open valves D, E, F, G, start the chiller, cooling tower, main circulation pump, self-circulation pump, chilled water pump and cooling water pump, and run the main cooling cycle, evaporator refrigeration cycle, condenser cooling cycle and self-circulation of the cooled equipment. The cooling tower cools the refrigeration unit, and the cooling water pump serves as the power pump of the cooling tower. The chilled water pump draws the cooling water in the chilled water tank, and after cooling and cooling, it enters the cold water tank. The self-circulation water pump draws the cooling water in the cold water tank into the cooled equipment to absorb heat. After the cooling water is heated up, it enters the hot water tank and is then transported back to the chilled water tank by the main circulation water pump.

[0075] C: Transition season joint operation mode: When the wet bulb temperature is greater than 21℃ and less than 24℃, close valves C and D, open valves A, B, D, E, F, G, H, start the chiller, cooling tower, main circulation pump, self-circulation pump, chilled water pump and cooling water pump, and run the main cooling cycle, evaporator refrigeration cycle, condenser cooling cycle and cooled equipment self-circulation. The cooling water in the hot water tank enters the cooling tower and is cooled to the intermediate temperature T m After entering the chilled water tank, it is pumped to the chiller evaporator by the chilled water pump for further cooling before entering the cold water tank. The cooling water in the cold water tank absorbs heat through the self-circulation of the cooled equipment and then returns to the hot water tank.

[0076] "Dual Mode" System:

[0077] Because the "three-mode" system includes a joint operation mode, the control and system are relatively complex. In order to simplify the system, the joint operation mode can be removed, and only the cooling tower independent operation mode and the chiller independent operation mode are retained to become a "dual-mode" system. Figure 5 shown.

[0078] A: Winter cooling tower independent operation mode - "free cooling" mode: When the wet bulb temperature is ≤21℃, close valves D, E, F, G, open valves A, B, C, turn off the chiller, chilled water pump and cooling water pump, start the cooling tower and main circulation pump, only run the main cooling cycle, and the cooling tower supplies cold to the intermediate cooling water tank. The equipment return water T1 directly enters the cooling tower for cooling and then returns to the water tank. At this time, the main circulation pump serves as the power pump for the cooling tower and the cooled equipment.

[0079] B: Independent operation mode of chiller in summer and transition season: When the wet bulb temperature is greater than 21℃, close valves A and B, open valves C, D, E, F, G, start the chiller, cooling tower, main circulation pump, chilled water pump and cooling water pump, and run the main cooling cycle, evaporator refrigeration cycle and condenser cooling cycle. The cooling tower cools the refrigeration unit. At this time, the cooling water pump serves as the power pump of the cooling tower. The unit supplies cooling to the intermediate cooling water tank. The water required by the cooled equipment is directly drawn from the intermediate cooling water tank and returned to the intermediate cooling water tank after heat exchange.

[0080] The above has analyzed the "dual mode" system. In the actual implementation process, it can be appropriately simplified. There are several forms:

[0081] "Dual Mode" Simplified System - Main Circulation Pump Also Acts as Chilled Water Pump

[0082] As attached Figure 6 As shown. The chiller is directly connected to the main cooling cycle, the refrigeration cycle becomes a part of the main cooling cycle, and the main circulation pump also operates as a chilled water pump. The intermediate cooling water tank is changed to a circulating water tank, and the stable temperature is T2 or T1.

[0083] A: Winter cooling tower independent operation mode - "free cooling" mode: when the wet bulb temperature is ≤21℃, close valves D, E, F, G, open valves A, B, C, turn off the chiller and cooling water pump, start the cooling tower and main circulation water pump, only run the main cooling cycle, and the cooling tower supplies cold water to the circulating water tank. The equipment return water T1 directly enters the cooling tower for cooling and then returns to the water tank. At this time, the main circulation pump serves as the power pump for the cooling tower and the cooled equipment.

[0084] B: Independent operation mode of chiller in summer and transitional seasons: When the wet bulb temperature is greater than 21°C, close valves A, B, and C, open valves D, E, F, and G, start the chiller, cooling tower, main circulation pump (also serving as a chilled water pump), and cooling water pump, and run the main cooling cycle and condenser cooling cycle. The cooling tower cools the refrigeration unit, and the cooling water pump serves as the power pump of the cooling tower. The chiller draws cooling water from the circulating water tank, which enters the cooled equipment to absorb heat after cooling, and then returns to the circulating water tank.

[0085] "Dual mode" simplified system - chilled water pump or cooling water pump also serves as the main circulation pump:

[0086] As attached Figure 7 As shown. The chiller is directly connected to the main cooling cycle. When the chiller operates independently, the refrigeration cycle becomes part of the main cooling cycle. The chilled water pump also operates as the main circulation pump, and the hot water tank is used as the system circulation water tank. The stable temperature is T1. When the cooling tower operates independently, the cooling water pump also operates as the main circulation pump, and the cold water tank is used as the system circulation water tank. The stable temperature is T2.

[0087] A: Winter cooling tower independent operation mode - "free cooling" mode: When the wet bulb temperature is ≤21℃, close valves C, D, E, F, open valves A, B, G, turn off the chiller and chilled water pump, turn on the cooling tower and cooling water pump, only run the main cooling cycle, and the cooling tower supplies cold water to the cold water tank. The equipment return water T1 directly enters the cooling tower for cooling and then returns to the cold water tank. At this time, the cooling water pump also serves as the main circulation pump and as the power pump for the cooling tower and the cooled equipment.

[0088] B: Independent operation mode of chiller in summer and transition season: When the wet bulb temperature is greater than 21℃, close valves A, B, and G, open valves C, D, E, and F, start the chiller, cooling tower, cooling water pump, and chilled water pump, and run the main cooling cycle and condenser cooling cycle. The cooling tower cools the refrigeration unit, and the cooling water pump serves as the power pump of the cooling tower. The chilled water pump becomes the main circulation pump, extracting cooling water from the hot water tank, and after cooling, it enters the cooled equipment to absorb heat and then returns to the hot water tank.

[0089] "Dual mode" system - self-circulation of the cooled equipment:

[0090] As attached Figure 8 shown.

[0091] A: Winter cooling tower independent operation mode - "free cooling" mode: when the wet-bulb temperature is ≤21℃, close valves C, D, E, F, G, open valves A and B, turn off the chiller, chilled water pump and cooling water pump, start the cooling tower, main circulation pump and self-circulation pump, and only run the main cooling cycle and the self-circulation of the cooled equipment. The cooling tower supplies cold water to the cold water tank. The equipment return water T1 enters the cooling tower from the hot water tank and returns to the cold water tank after cooling. At this time, the main circulation pump serves as the power pump of the cooling tower. As the wet-bulb temperature decreases, the number of fans or spray pumps in operation can be reduced to ensure that the equipment inlet water temperature is within 25℃±0.5.

[0092] B: Independent operation mode of chiller in summer and transitional seasons: When the wet-bulb temperature is greater than 21°C, close valves A and B, open valves C, D, E, F, and G, start the chiller, cooling tower, main circulation pump, self-circulation pump, chilled water pump, and cooling water pump, and run the main cooling cycle, evaporator refrigeration cycle, condenser cooling cycle, and self-circulation of the cooled equipment. The cooling tower cools the refrigeration unit, and the cooling water pump serves as the power pump of the cooling tower. The chilled water pump draws the cooling water from the chilled water tank, and after cooling and cooling, it enters the cold water tank. The self-circulation water pump draws the cooling water from the cold water tank into the cooled equipment to absorb heat. After the cooling water is heated up, it enters the hot water tank and is then transported back to the chilled water tank by the main circulation water pump.

[0093] The cost analysis of the traditional chiller independent refrigeration cycle system is as follows:

[0094] 1) Equipment selection and configuration

[0095]

[0096] 2) Simplified power consumption analysis

[0097] The power consumption analysis was conducted based on local meteorological parameters. This power consumption analysis only counted the cooling tower and refrigeration unit, and did not include the operating energy consumption of the cooling and refrigeration and main circulation water pump units. At the same time, the water consumption of the two systems was not considered. When the "free cooling" system is adopted, the power consumption and water consumption of the pump unit can also be greatly reduced.

[0098] For the operation of refrigeration units, based on experience we can assume that for every 1°C reduction in the cooling circulating water supply temperature, the chiller compressor power can be reduced by 5%.

[0099] 3) Analysis of power consumption of independent refrigeration cycle of refrigerator

[0100]

[0101]

[0102]

[0103] Power consumption analysis of "three-mode free cooling" system

[0104]

[0105]

[0106] 1) Power consumption analysis of “dual-mode free cooling” system

[0107]

[0108]

[0109] In summary, compared with the traditional system where the refrigeration unit operates alone, the "three-mode free refrigeration" system saves 478680.9-202669.3=276012kW·h of electricity per year. Calculated at 0.65 yuan / kWh, it can save 179,340 yuan in electricity bills per year. The "dual-mode free refrigeration" system saves 478680.9-200067.7=278613kW·h of electricity per year. Calculated at 0.65 yuan / kWh, it can save 181,100 yuan in electricity bills per year. The "three-mode" only saves 17,600 yuan in electricity bills compared to the "dual-mode". Therefore, for this system, the "free refrigeration" system has a lower operating cost, and in the "free refrigeration" system, the "dual-mode" is better than the "three-mode".

[0110] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An energy-saving free refrigeration system, characterized in that: The invention comprises a refrigeration unit (1), a circulation pump unit (2) and a cooling tower (3), wherein the refrigeration unit (1), the circulation pump unit (2) and the cooling tower (3) are connected in a circulation manner, and the circulation pump unit (2) is connected to a cooled device (4); the refrigeration unit (1) comprises a condenser (11), an evaporator (12) and a compressor (13), and the cooling tower (3) and the refrigeration unit (1) cool the cooled device (4) through the circulation pump unit (2) respectively; the difference between the outlet temperature of the cooling tower (3) and the ambient wet-bulb temperature is defined as the approximation degree, and the lowest approximation degree that can be achieved by the cooling tower (3) is defined as the limit approximation degree.

2. An energy-saving free refrigeration system according to claim 1, characterized in that: When the difference between the cooling demand temperature of the cooled equipment (4) and the ambient wet-bulb temperature is greater than or equal to the limit approximation, the cooling tower (3) is provided as a separate cold source to the cooled equipment (4).

3. The energy-saving free refrigeration system according to claim 1, characterized in that: When the difference between the cooling demand temperature of the cooled equipment (4) and the ambient wet-bulb temperature is less than the limit approximation, the refrigeration unit (1) is started; the refrigeration unit (1) and the cooling tower (3) perform combined cooling, and the cooling tower (3) serves as the main cooling equipment to provide a cold source for the cooled equipment (4), and at the same time serves as an auxiliary equipment to cool the condenser (11) of the refrigeration unit (1).

4. The energy-saving free refrigeration system according to claim 1, characterized in that: When the difference between the hot fluid temperature of the cooled device (4) and the ambient wet-bulb temperature is less than or equal to the limit approximation, the refrigeration unit (1) is provided as a separate cold source to the cooled device (4), and the cooling tower (3) is used as an auxiliary device to cool the condenser (11) of the refrigeration unit (1).

5. The energy-saving free refrigeration system according to claim 1, characterized in that: The circulating pump group (2) comprises a main circulating water pump (21), a chiller refrigeration water pump (22), and a chiller cooling water pump (23); the chiller refrigeration water pump (22), the chiller cooling water pump (23) and the refrigeration unit (1) are intermittently operated in conjunction with the refrigeration unit (1).

6. The energy-saving free refrigeration system according to claim 1, characterized in that: The cooling tower (3) is an open cooling tower or a closed cooling tower.

Images