A cascaded heat pump system for achieving wide-range continuous adjustment of the energy output of a condenser

Abstract

The present invention relates to a cascaded heat pump system for achieving wide-range continuous regulation of the energy output of a condenser, which comprises at least one variable-frequency heat pump unit and multiple fixed-frequency heat pump units. The heat medium channels of the condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump units are connected in series. The variable-frequency heat pump unit controls and regulates the rotational speed of the compressor motor through a variable-frequency power supply module. The present invention can use one variable-frequency heat pump unit as the core, combine multiple fixed-frequency heat pump units, and construct a cascaded heat pump system to achieve wide-range continuous regulation of the energy output of the condenser group to the heat medium channel.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and particularly to a cascaded heat pump system for achieving wide-range continuous regulation of the energy output of a condenser. Background Art

[0002] When a heat pump unit is applied to scenarios such as grain drying, the drying air flow usually rises from an ambient temperature of about 20°C to about 70°C required by the drying process, with a large temperature rise. If a condenser of a high-power single-system heat pump unit is used for one-time heating, the cycle temperature rise (condensing temperature - evaporation temperature) of the heat pump unit will be very high, and the coefficient of performance (COP) (COP = condenser heating power / system electric power), which is a core technical index of the heat pump unit, will become very low because it is inversely related to the cycle temperature rise, even lower than 1.5. The economy of the heat pump unit will thus become very poor, losing its commercial value and market significance.

[0003] In order to improve the coefficient of performance of heat pump units in scenarios such as grain drying, heat pump enterprises usually adopt the method of cascaded configuration of condensers of multiple small-power single-machine heat pump subsystems and implementing cascaded small-power heating on the drying air flow to improve the overall coefficient of performance COP.

[0004] For example, if the heat pump evaporator is set to absorb heat from the ambient air at 20°C and the drying air flow is heated by the condenser to complete a one-time large-power large-span total temperature rise of 50°C from 20°C to 70°C, the COP will be very low. In order to improve the COP, some innovative heat pump enterprises decompose the one-time large-power large-span total temperature rise of 50°C from 20°C to 70°C into multiple small-stage small-power cascaded temperature rises of multiple small-power single-machine heat pump subsystem evaporators absorbing heat from the ambient air and then heating the drying air flow through multiple condensers. For example, it is decomposed into three-step heating of the drying air flow from the ambient temperature of 20°C to 36.7°C, 36.7°C to 53.4°C, and 53.4°C to 70°C. The "ultra-high COP" of 20°C to 36.7°C (COP ≥ 6) and the "high COP" of 36.7°C to 53.4°C (COP ≥ 4) in the early and middle small-power cascaded temperature rise stages of this 3-stage temperature rise combination of the drying air flow are used to offset and neutralize the "ultra-low COP" lower than 1.5 of the one-time large-power 50°C total temperature rise of the drying air flow from 20°C to 70°C, so as to obtain a relatively high (≥ 2.5) overall coefficient of performance for the entire system of the heat pump unit composed of multiple small-power single-machine heat pump subsystems.

[0005] Furthermore, these innovative heat pump enterprises with an exploratory spirit adopt a cascaded heat pump system composed of multiple single-stage heat pump modules, where some or all of the single-stage heat pump modules are composed of more than two heat pump subsystems; the finned tube heat exchangers (evaporators and / or condensers) of more than two heat pump subsystems for each single-stage heat pump module adopt a refrigerant pipeline staggered nesting technology, with the refrigerant pipelines arranged at intervals, and the heat absorption and heat release integration of the heat exchangers of more than two heat pump subsystems of the single-stage heat pump module are realized through the fin heat bridge effect on the refrigerant pipeline of the heat exchanger; as the heat source of the drying device for recovering the outgoing air heat, multiple small-power single-stage heat pump modules can be combined to replace a high-power single-stage heat pump unit. The heat exchangers of multiple single-stage heat pump modules with staggered nesting refrigerant pipelines are arranged in a cascade in the air duct to implement multi-stage evaporator cascade recovery of the outgoing air heat of the drying device and multi-stage condenser cascade heating of the fresh air flow for drying, reduce the difference between the condensation temperature and the evaporation temperature of each heat pump subsystem of each single-stage heat pump module, improve the COP of each heat pump subsystem of each single-stage heat pump module, and thus greatly improve the comprehensive heating energy efficiency ratio COP of the whole system throughout the process.

[0006] More specifically, a cascaded heat pump system is composed of multiple single-stage heat pump modules. Its evaporator and condenser can adopt a 4-stage configuration, that is, 8 sets of evaporators and condensers supporting compressors with a motor power of P are used, paired in groups of two, with the refrigerant pipelines staggered and nested to form 4 single-stage heat pump modules; by combining the start and stop of 4 groups of 8 heat pump subsystems driven by compressors with a motor power of P, a condenser heat power output corresponding to 1P, 2P, 3P, 4P, 5P, 6P, 7P, 8P, a total of 4 levels and 8 gears corresponding to the total compressor motor power can be combined with the heat pump subsystem driven by the compressor with an electric power of P as the basic energy unit, having a very wide energy spectrum; moreover, since more than two heat pump subsystems are used to form a single-stage heat pump module through the staggered nesting of the refrigerant pipelines of the evaporator and condenser, in the above scenarios of the condenser heat power output corresponding to 5 gears above 4P and the compressor motor power, the COP of the cascaded heat pump system is very high.

[0007] However, this cascaded heat pump system composed of multiple single-stage heat pump modules is difficult to accurately control the heat power output and has poor variable load adaptability:

[0008] ① The reduction of the heat load leads to the reduction of the COP

[0009] When the heat load demand of the drying device decreases due to a decrease in the feeding amount, an increase in the ambient temperature, etc., the above cascaded heat pump system can only adjust the heat power output by stopping some of the small-power single-machine heat pump subsystems or single-stage heat pump modules, so that the four-stage cascaded heat pump is reduced to a three-stage cascaded heat pump system, a two-stage cascaded heat pump system or even a single-stage heat pump system, and the corresponding comprehensive COP also decreases accordingly.

[0010] ②The output heat load can only be an integer multiple of the condenser output heat power of a single-unit heat pump subsystem and cannot be continuously adjusted.

[0011] The above-mentioned cascade heat pump system composed of four groups of single-stage heat pump modules, through the start-stop combination of the heat pump subsystems driven by 8 sets of motors with power P compressor in 4 groups of single-stage heat pump modules, with the heat pump subsystem driven by the electric power P compressor as the basic energy unit, can combine a total of 4 levels and 8 gears of condenser heat power outputs corresponding to the total compressor motor power of 1P, 2P, 3P, 4P, 5P, 6P, 7P, and 8P; on the energy spectrum, these are only 8 discrete distribution points rather than a wide continuous period; when the thermal device needs to more precisely adjust the heat output power and make continuous adjustments between the above 8 gears, the cascade heat pump system is powerless. Summary of the Invention

[0012] To solve the above problems, the present invention provides a cascade heat pump system that realizes wide-range continuous adjustment of condenser energy output, including at least one set of variable-frequency heat pump units and multiple sets of fixed-frequency heat pump units, and the heat medium channels of the condensers of the variable-frequency heat pump units and the fixed-frequency heat pump units are connected in series.

[0013] Preferably, the variable-frequency heat pump unit controls and adjusts the rotational speed of the compressor motor through a variable-frequency power supply module.

[0014] Preferably, a blower is provided on one side of the evaporator of the variable-frequency heat pump unit.

[0015] Radiating fins are provided on the variable-frequency power supply module, and the heat dissipation channels between the radiating fins are communicated with the air inlet of the blower.

[0016] Preferably, the evaporator of the variable-frequency heat pump unit is arranged in an air flow channel, and the blower is arranged at the outlet of the air flow channel; a flow guide cover is provided outside the air flow channel, and the flow guide cover is respectively communicated with the outlet of the air flow channel and the external environment; the radiating fins of the variable-frequency power supply module are arranged in the flow guide cover.

[0017] Preferably, a water pump is provided on one side of the evaporator of the variable-frequency heat pump unit.

[0018] Radiating fins are provided on the variable-frequency power supply module, and the heat dissipation channels between the radiating fins are communicated with the water inlet of the water pump.

[0019] Preferably, the evaporator of the variable-frequency heat pump unit is arranged in a water flow channel, and the water pump is arranged at the outlet of the water flow channel; a flow guide cover is provided outside the water flow channel, and the flow guide cover is respectively communicated with the outlet of the water flow channel and the water body environment; the radiating fins of the variable-frequency power supply module are arranged in the flow guide cover.

[0020] Preferably, the condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump unit both adopt finned tube heat exchangers.

[0021] Preferably, the condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump unit are both arranged in an air duct, and all the condensers are arranged at intervals from the inlet of the air duct to the outlet of the air duct.

[0022] Preferably, some or all of the variable-frequency heat pump units and the fixed-frequency heat pump units are single-stage heat pump modules composed of at least two heat pump subsystems. The single-stage heat pump module includes at least two compressors, a condenser module, at least two throttling devices, and an evaporator module. Both the evaporator module and the condenser module include fin arrays and at least two sets of refrigerant pipelines passing through the fin arrays, and these sets of refrigerant pipelines are arranged in a staggered and nested manner; a compressor, a set of refrigerant pipelines of the condenser, a throttling device, and a set of refrigerant pipelines of the evaporator are sequentially connected to form a refrigerant circulation loop of a heat pump subsystem.

[0023] Preferably, the condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump unit both adopt shell-and-tube heat exchangers.

[0024] Preferably, it is used for cascaded recovery of the outlet air heat of the drying device and cascaded heating of the drying air flow. The drying device includes a drying air flow inlet channel, a drying section, and a drying air flow outlet channel. Both the drying air flow inlet channel and the drying air flow outlet channel are communicated with the drying section;

[0025] The cascaded heat pump system includes several fixed-frequency heat pump units and at least one variable-frequency heat pump unit. The condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump unit are both arranged in the drying air flow inlet channel and are arranged sequentially and at intervals from the inlet side of the drying air flow inlet channel to the drying section; each evaporator corresponding to each condenser is arranged in the drying air flow outlet channel and is arranged sequentially and at intervals from the outlet side of the drying air flow outlet channel to the drying section.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] The present invention provides a cascaded heat pump system for achieving wide-range continuous regulation of the energy output of a condenser. With a set of variable-frequency heat pump units as the core and multiple sets of fixed-frequency heat pump units combined, the heat medium channels (air ducts, water circuits, etc.) of the condensers of a set of variable-frequency heat pump systems and multiple sets of fixed-frequency heat pump systems are connected in series to construct a cascaded heat pump system, so as to achieve wide-range continuous regulation of the energy output of the condenser group to the heat medium. The present invention only combines a set of variable-frequency heat pump systems with multiple sets of fixed-frequency heat pump systems, thus filling the energy gap that traditional cascaded heat pump systems can only provide multi-stage energy output but not wide-range continuous energy output. In the energy spectrum, a number of discrete energy output points are expanded into a period with wide-range continuous energy output, meeting the continuous and precise variable load requirements of thermal devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings. In the drawings:

[0029] Figure 1 FIG. is a schematic structural diagram of a cascaded heat pump system for achieving wide-range continuous regulation of the energy output of a condenser provided for Preferred Embodiment 1 of the present invention;

[0030] Figure 2 FIG. is a schematic diagram of the continuous following of the heat load demand by a 4-stage cascaded heat pump system implanted with 1 set of variable-frequency heat pump units provided for Preferred Embodiment 1 of the present invention (relationship diagram between output heat power and motor power);

[0031] Figure 3 FIG. is a schematic structural diagram of a single-stage heat pump module composed of two heat pump subsystems provided for Preferred Embodiment 1 of the present invention;

[0032] Figure 4 FIG. is a schematic structural diagram of a cascaded heat pump system for achieving wide-range continuous regulation of the energy output of a condenser provided for Preferred Embodiment 2 of the present invention;

[0033] Figure 5 FIG. is a schematic structural diagram of a drying double-cascaded heat pump system implanted with a variable-frequency heat pump unit provided for Preferred Embodiment 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will be combined with Figures 1 to 5A cascaded heat pump system for achieving wide-range continuous adjustment of condenser energy output provided by the present invention is described in detail. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments. Those skilled in the art can modify and polish it without changing the spirit and content of the present invention.

[0035] The present invention provides a cascaded heat pump system for achieving wide-range continuous adjustment of condenser energy output, including at least one variable-frequency heat pump unit and multiple fixed-frequency heat pump units. The heat medium channels of the condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump units are connected in series to construct a cascaded heat pump system, so as to achieve wide-range continuous adjustment of the energy output of the condenser group to the heat medium channel.

[0036] When the cascaded heat pump system operates, the controller of the cascaded heat pump system inputs the variable-frequency heat pump unit and several fixed-frequency heat pump units according to the heat load demand signal; if the difference between the energy output of the condenser group to the heat medium channel and the heat load demand is greater than the heat output of the condenser of 1 fixed-frequency heat pump unit, the controller increases or decreases the operation of 1 fixed-frequency heat pump unit until the difference is less than the output of the condenser of 1 fixed-frequency heat pump unit; when the difference between the energy output of the condenser group to the heat medium channel and the heat load demand is less than the heat output of the condenser of 1 fixed-frequency heat pump unit, the controller adjusts the compressor speed and refrigerant circulation amount of the variable-frequency heat pump unit to adjust the heat output of the condenser of the variable-frequency heat pump unit, thereby adjusting the total energy output of the entire cascaded heat pump system until the difference is reduced to within the energy output control accuracy range, and then stabilizing the speed of the compressor of the variable-frequency heat pump unit to achieve dynamic following of the heat load demand by the cascaded heat pump system.

[0037] The beneficial effect of the present invention is that the combination of the variable-frequency heat pump unit and the fixed-frequency heat pump unit fills the energy gap that the traditional cascaded heat pump system can only provide multi-stage energy output but cannot provide wide-range continuous energy output, and expands several discretely distributed energy output points in the energy spectrum into a period with wide-range continuous energy output, meeting the continuous and precise variable load requirements of thermal devices.

[0038] Embodiment 1

[0039] A cascaded heat pump system for realizing wide-range continuous regulation of condenser energy output in this embodiment includes at least one variable-frequency heat pump unit 1 and multiple fixed-frequency heat pump units 2. The heat medium channels of the condenser module 11 of the variable-frequency heat pump unit 1 and the condensers 21 of the fixed-frequency heat pump units 2 are connected in series to construct a cascaded heat pump system, so as to realize wide-range continuous regulation of the energy output of the condenser group to the heat medium channel. In this embodiment, the numbers of the variable-frequency heat pump unit 1 and the fixed-frequency heat pump units 2 are not specifically limited and can be set according to actual usage requirements. Moreover, there is no limitation on the heat medium, such as it can be a gas, a liquid, or a gas-liquid mixture.

[0040] As shown in the figure, it is a combination of 1 variable-frequency heat pump unit 1 and 3 fixed-frequency heat pump units 2. In this embodiment, the condenser module 11 of 1 variable-frequency heat pump unit 1 and the condensers 21 of 3 fixed-frequency heat pump units 2 are both fin-tube heat exchangers, and the heat medium of the condensers is a gas. Therefore, the condenser 11 of the variable-frequency heat pump unit 1 and the condensers 21 of the fixed-frequency heat pump units 2 are both arranged in the air duct 3 and are arranged sequentially and at intervals from the inlet of the air duct 3 to the outlet of the air duct 3. There is no limitation on whether the condenser module 11 of the variable-frequency heat pump unit 1 is arranged at the bottom, middle, or upper part of the condensers 21 of the fixed-frequency heat pump units 2. Figure 1 It shows that the condenser module 11 of the variable-frequency heat pump unit 1 is arranged at the inlet of the air duct 3, but it is not limited to this. A four-stage cascaded heat pump system is constructed to realize wide-range continuous regulation of the energy output of the condenser group to the air duct, and accurately meet the dynamic requirements of the thermal device for the temperature and heat of the high-temperature drying air flow.

[0041] When the cascaded heat pump system for realizing wide-range continuous regulation of condenser energy output in this embodiment operates, the four-stage cascaded heat pump system controller starts all or part of the variable-frequency heat pump unit 1 and 3 fixed-frequency heat pump units 2 according to the heat load demand signal; if the difference between the energy output of the condenser group to the hot air channel and the heat load demand is greater than the heat output of the condenser of 1 fixed-frequency heat pump unit 2, the controller increases or decreases the operation of 1 fixed-frequency heat pump unit 2 until the difference is less than the output of the condenser of 1 fixed-frequency heat pump unit 2; when the difference between the energy output of the condenser group to the hot air channel and the heat load demand is less than the heat output of the condenser of 1 fixed-frequency heat pump unit 2, the controller adjusts the compressor speed and refrigerant circulation volume of the variable-frequency heat pump unit 1 to regulate the heat output of the condenser of the variable-frequency heat pump unit 1, thereby regulating the total energy output of the entire four-stage cascaded heat pump system until the difference is reduced to within the energy output control accuracy range, and then stabilizing the speed of the variable-frequency compressor to realize the dynamic following of the four-stage cascaded heat pump system to the heat load demand. As Figure 2 As shown in the right half, it is set that there is a 4-fold relationship between the heat output power Q of the condenser and the motor power P of the compressor, Q = 4P.

[0042] The beneficial effect of the cascade heat pump system for realizing wide-range continuous regulation of the condenser energy output in this embodiment is that only by combining 1 set of variable-frequency heat pump system with 3 sets of fixed-frequency heat pump systems, the energy gap that the traditional cascade heat pump system can only provide 4 energy output levels and cannot provide wide-range continuous energy output is filled. On the energy spectrum, 4 discretely distributed energy output points (as shown in the left half part, such as Figure 2 shown in the left half) are developed into a period with wide-range continuous energy output (as shown in the right half part, such as Figure 2 shown in the right half), meeting the continuous and precise variable load requirements of the thermal equipment.

[0043] In this embodiment, the variable-frequency heat pump unit 1 controls and adjusts the rotational speed of the compressor 12 through the variable-frequency power supply module 13.

[0044] Furthermore, the variable-frequency heat pump unit 1 controls and adjusts the rotational speed of the compressor 12 through the variable-frequency power supply module 13. The variable-frequency power supply module 13 includes a power transmission module and a variable-frequency control module. The variable-frequency control module is respectively connected to the power transmission module and the controller of the heat pump system. The variable-frequency control module adjusts the rotational speed of the compressor of the variable-frequency heat pump unit 1 according to the actual usage requirements.

[0045] Since the variable-frequency power supply module 13 generates heat, therefore, in order to solve the heat dissipation of the variable-frequency power supply module 13, heat dissipation fins 131 are provided on the variable-frequency power supply module 13. The following will be described in detail according to the evaporator 16 of the variable-frequency heat pump unit 1 being arranged in different media.

[0046] As an embodiment, the heat absorption medium of the evaporator 16 of the variable-frequency heat pump unit 1 is a gas: A blower 14 is provided on one side of the evaporator 16 of the variable-frequency heat pump unit 1. The function of the blower 14 is to drive the air flow to flow through the evaporator 16 of the variable-frequency heat pump unit 1. The heat dissipation channels between the heat dissipation fins 131 on the variable-frequency power supply module 13 are communicated with the air inlet of the blower 14, aiming to dissipate the heat of the heat dissipation fins 131 on the variable-frequency power supply module 13 through the blower 14.

[0047] Specifically, the evaporator 16 of the variable-frequency heat pump unit 1 is placed in the air flow channel 15, and the blower 14 is provided at the outlet of the air flow channel 15; In this embodiment, no specific limitation is made on what medium flows in the air flow channel 15, which can be air, nitrogen, carbon dioxide, etc. In this embodiment, air is taken as an example. Therefore, the air flow channel 15 is an air channel.

[0048] A flow guide cover is provided outside the air flow channel 15, and the flow guide cover is communicated with the outlet of the air flow channel 15 and the external air environment respectively; the heat dissipation fins 131 of the variable frequency power supply module 13 are arranged in the flow guide cover, and the flow guide cover is communicated with the outlet of the air flow channel 15 and the external air environment respectively; the heat dissipation channels between the heat dissipation fins 131 on the variable frequency power supply module 13 are communicated with the external air environment and the outlet of the air flow channel 15 respectively, and the outlet of the heat dissipation channel is communicated with the air inlet of the fan 14. When the fan 14 is working, a negative pressure is generated at its air inlet. Therefore, the external environmental air flows through the heat dissipation channels between the heat dissipation fins 131 to quickly take away the heat of the variable frequency power supply module 13 through the fan 14, aiming to ensure that the variable frequency power supply module 13 is in a safe and reliable working condition.

[0049] As another embodiment, the heat absorption medium of the evaporator 16 of the variable frequency heat pump unit 1 is a liquid. In this embodiment, there is no limitation on what specific liquid it is. Taking water as an example, a water pump is provided on one side of the evaporator 16 of the variable frequency heat pump unit 1, and the function of the water pump is to drive water to flow through the evaporator 16 of the variable frequency heat pump unit 1. The heat dissipation channels between the heat dissipation fins of the variable frequency power supply module are communicated with the water inlet of the water pump.

[0050] Specifically, the evaporator 16 of the variable frequency heat pump unit 1 is arranged in the water flow channel, and the water pump is arranged at the outlet of the water flow channel; a flow guide cover is provided outside the water flow channel, and the flow guide cover is communicated with the outlet of the water flow channel and the water body environment respectively; the heat dissipation fins of the variable frequency power supply module are arranged in the flow guide cover.

[0051] As an embodiment, please refer to Figure 1 , both the variable frequency heat pump unit 1 and the fixed frequency heat pump unit 2 are composed of a set of heat pump subsystems, and the structures of the refrigerant circulation circuits of the variable frequency heat pump unit 1 and the fixed frequency heat pump unit 2 are the same. Taking the variable frequency heat pump unit 1 as an example, it includes a compressor 12, a condenser module 11, a throttling device 17 and an evaporator module 16. The compressor 12, the condenser module 11, the throttling device 17 and the evaporator module 16 are sequentially connected to form the refrigerant circulation circuit of this set of heat pump subsystems.

[0052] As another embodiment, some or all of the variable frequency heat pump unit 1 and the fixed frequency heat pump unit 2 are single-stage heat pump modules composed of at least two sets of heat pump subsystems. Taking the variable frequency heat pump unit 1 as a single-stage heat pump module composed of two sets of heat pump subsystems, please refer to Figure 3, this variable-frequency heat pump unit 1' includes two compressors 12', a condenser module 11', two throttling devices 17' and an evaporator module 16'. Both the evaporator module 16' and the condenser module 11' include fin arrays and at least two sets of refrigerant pipelines passing through the fin arrays. These sets of refrigerant pipelines are arranged in a staggered and nested manner, that is, these sets of refrigerant pipelines are not in the same row, and one set of refrigerant pipeline is embedded in another set or several other sets of refrigerant pipelines; One of the compressors 12', one set of refrigerant pipelines of the condenser module 11', one of the throttling devices 17' and one set of refrigerant pipelines of the evaporator module 16' are sequentially connected to form a refrigerant circulation loop of a heat pump subsystem. In this embodiment, the number of compressors 12' = the number of sets of refrigerant pipelines of the evaporator module 16' = the number of throttling devices 17' = the number of sets of refrigerant pipelines of the condenser module 11'.

[0053] In this embodiment, each set of refrigerant pipelines includes several refrigerant branches passing through the fin array, and these refrigerant branches are arranged in parallel;

[0054] The refrigerant branches of these sets of refrigerant pipelines are arranged alternately to form a staggered and nested structure.

[0055] Specifically, the fin array is composed of several fins arranged in parallel;

[0056] Each refrigerant branch is a serpentine tube. Specifically, each refrigerant branch includes several straight pipe segments respectively passing through several of the fins, and several of these straight pipe segments are connected in series by elbow segments at their ends to form a serpentine tube;

[0057] The straight pipe segments of the refrigerant pipe branches in adjacent two rows are arranged staggeredly.

[0058] This embodiment does not limit which specific refrigerant flows in the refrigerant pipeline, and it can be set according to actual usage requirements.

[0059] In this embodiment, the finned tube evaporators and condensers of two or more heat pump subsystems of a single-stage heat pump module adopt the technology of staggered nesting of each set of refrigerant pipelines, and through the fin heat bridge effect on the refrigerant pipeline, the integration of evaporator heat absorption and condenser heat release of two or more heat pump subsystems of a single-stage heat pump module is realized.

[0060] Embodiment 2

[0061] The basic principle of this embodiment is the same as that of Embodiment 1. The difference is, please refer to Figure 4, the condenser of this embodiment adopts a shell-and-tube heat exchanger. The refrigerant flows through the tube side, and the heated medium flows through the shell side. The heated medium is a liquid. Taking water as an example, that is, there are a water inlet and a water outlet on the shell of the shell-and-tube heat exchanger. The heat pump system of this embodiment includes a set of variable-frequency heat pump units 1 and three sets of fixed-frequency heat pump units 2. The condenser of the variable-frequency heat pump unit 1 is the primary heating unit for the heated medium. That is, the water inlet of the condenser of the variable-frequency heat pump unit 1 is connected to the external water, and the water outlet of the condenser of the variable-frequency heat pump unit 1 is connected to the water inlet of the condenser of the second-stage fixed-frequency heat pump unit 2 through a pipeline. The water outlet of the condenser of the second-stage fixed-frequency heat pump unit 2 is connected to the water inlet of the condenser of the third-stage fixed-frequency heat pump unit 2 through a pipeline, and so on. The water circuits of the 4 shell-and-tube heat exchangers of the four-stage cascade heat pump system are connected in series for cascade heating to produce hot water; the variable-frequency heat pump unit 1 adopts a variable-frequency compressor, so that the outlet water temperature can be continuously adjusted.

[0062] Embodiment 3

[0063] Please refer to Figure 5 , this embodiment adopts a double-stage heat pump system composed of multiple single-stage heat pump modules for cascade recovery of the outlet air heat and cascade heating of the drying air flow, which is used for cascade recovery of the outlet air heat of the drying device 4 and cascade heating of the drying air flow. The drying device 4 includes a drying air flow inlet channel 41, a drying section 42, and a drying air flow outlet channel 43. Both the drying air flow inlet channel 41 and the drying air flow outlet channel 43 are communicated with the drying section 42;

[0064] The cascade heat pump system includes several fixed-frequency heat pump units 2 and at least one variable-frequency heat pump unit 1. The condensers 11 of the variable-frequency heat pump units 1 and the condensers 21 of the fixed-frequency heat pump units 2 are both arranged in the drying air flow inlet channel 41, and are arranged sequentially and at intervals from the inlet side of the drying air flow inlet channel 41 to the drying section 42;

[0065] The respective evaporators corresponding to the respective condensers are all arranged in the drying air flow outlet channel 43, and are arranged sequentially and at intervals from the outlet side of the drying air flow outlet channel 43 to the drying section 42.

[0066] This embodiment does not specifically limit the number of the variable-frequency heat pump units 1 and the fixed-frequency heat pump units 2, which can be set according to actual use requirements. Please refer to Figure 5 , with 1 set of variable-frequency heat pump unit 1 as the core, combined with 3 sets of fixed-frequency heat pump units 2.

[0067] There is no limit on whether the condenser 11 of the variable-frequency heat pump unit 1 is arranged at the bottom, middle or upper part of the condenser 21 of the fixed-frequency heat pump unit 2, and there is also no limit on whether the evaporator of the variable-frequency heat pump unit 1 is arranged at the bottom, middle or upper part of the evaporator of the fixed-frequency heat pump unit 2. Figure 5It is shown that the condenser 11 of the variable-frequency heat pump unit 1 is arranged at the inlet of the dry air flow inlet passage 41; the evaporator 16 of the variable-frequency heat pump unit 1 is arranged at the outlet of the dry air flow outlet passage 43.

[0068] Both the variable-frequency heat pump unit 1 and the fixed-frequency heat pump unit 2 are composed of a set of heat pump subsystems, or / and both the variable-frequency heat pump unit 1 and the fixed-frequency heat pump unit 2 are single-stage heat pump modules composed of at least two sets of heat pump subsystems.

[0069] In this embodiment, some or all of the single-stage heat pump modules adopt single-stage heat pump modules composed of more than two sets of heat pump subsystems; for the finned tube heat exchangers (evaporators and / or condensers) of more than two sets of heat pump subsystems that make up each single-stage heat pump module, the refrigerant pipeline staggered nesting technology is adopted, and the refrigerant pipelines are arranged at intervals from each other, and the heat absorption and heat release integration of the heat exchangers of more than two sets of heat pump subsystems of the single-stage heat pump module is realized through the fin heat bridge effect on the refrigerant pipelines of the heat exchanger; in this embodiment, as the heat source of the drying device 4 for cascade recovery of the outlet air heat, the heat exchangers of the single-stage heat pump modules with staggered nesting of multiple sets of refrigerant pipelines are configured in steps in the air duct, the outlet air heat of the drying device 4 is subjected to multi-stage evaporator cascade recovery, the fresh dry air flow is subjected to multi-stage condenser cascade heating, the difference between the condensation temperature and the evaporation temperature of each heat pump subsystem of each single-stage heat pump module is reduced, the COP of each heat pump subsystem of each single-stage heat pump module is increased, and thus the comprehensive heating energy efficiency ratio COP of the whole system throughout the process is greatly improved.

[0070] The evaporator group and the condenser group of this embodiment adopt a 3.5-level configuration, that is, an evaporator module and a condenser module supporting a compressor with a motor power of P are paired in pairs, and the refrigerant pipelines are staggered and nested to form 3 single-stage heat pump modules; then a variable-frequency compressor with the same cylinder volume as the fixed-frequency compressor with a motor power of 0.5P and the corresponding evaporator module and condenser module are used to form a single-stage heat pump module. From the energy perspective of heat absorption and heat release, the peak heat absorption and heat release power of this variable-frequency single-stage heat pump module based on the cylinder volume of the 0.5P fixed-frequency compressor is equivalent to 0.5 of a single-stage heat pump module including 2 fixed-frequency compressors with a motor power of 1P, so it is combined and called a 3.5-level configuration, as Figure 5 shown;

[0071] In this embodiment, since a variable-frequency compressor with the same cylinder volume as that of a 0.5P fixed-frequency compressor is implanted, if the difference between the energy output of the condenser group and the heat load demand is greater than the heat output of the condenser of 1 set of 1P fixed-frequency heat pump system, the controller increases or decreases the operation of 1 set of fixed-frequency heat pump system until the difference is less than the output of the condenser of 1 set of fixed-frequency heat pump system; when the difference between the energy output of the condenser group to the heat medium channel and the heat load demand is less than the heat output of the condenser of 1 set of fixed-frequency heat pump system, the controller adjusts the rotational speed of the compressor and the refrigerant circulation volume of the variable-frequency heat pump system by putting into operation the 0.5P variable-frequency heat pump system to regulate the heat output of the condenser of the variable-frequency heat pump system so as to regulate the total energy output of the entire four-stage cascade heat pump system until the difference is gradually reduced to within the energy output control accuracy range and then the rotational speed of the variable-frequency compressor is stabilized, realizing the dynamic follow-up of the four-stage cascade heat pump system to the heat load demand.

[0072] This embodiment has the advantages of Embodiment 1, that is, "developing the discretely distributed energy output points in the energy spectrum into a period with a wide and continuous energy output amplitude, meeting the continuous and precise variable load demand of the thermal device". And because the finned tube heat exchangers of the two heat pump subsystems that make up each single-stage heat pump module adopt the refrigerant pipeline staggered nesting technology, the refrigerant pipelines are arranged at intervals of each other, and the heat absorption and heat release integration of the heat exchangers of the two heat pump subsystems of the single-stage heat pump module is realized through the fin heat bridge effect on the refrigerant pipeline of the heat exchanger. When the three-stage 1P fixed-frequency compressor single-stage heat pump module is operating at half load in this embodiment, since the operating heat pump subsystem makes full use of the evaporator and condenser fin resources of the other half of the stopped subsystem, the heat exchange area of the two devices is enlarged, the heat transfer temperature difference of the heat exchanger is reduced, and the COP is further improved.

Claims

1. A cascaded heat pump system for achieving wide-range continuous adjustment of condenser energy output, characterized in that, For the cascaded recovery of the outlet heat of the drying device and the cascaded heating of the drying air flow, the drying device includes a drying air flow inlet channel, a drying section, and a drying air flow outlet channel, and both the drying air flow inlet channel and the drying air flow outlet channel are communicated with the drying section; The cascaded heat pump system includes a number of fixed-frequency heat pump units and at least one variable-frequency heat pump unit. The condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump units are all arranged in the drying air flow inlet channel, and are sequentially and spacedly arranged from the inlet side of the drying air flow inlet channel to the drying section; each evaporator corresponding to each condenser is arranged in the drying air flow outlet channel, and is sequentially and spacedly arranged from the outlet side of the drying air flow outlet channel to the drying section; The condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump units all adopt finned tube heat exchangers; All the units in the variable-frequency heat pump unit and the fixed-frequency heat pump units are single-stage heat pump modules composed of at least two sets of heat pump subsystems. The single-stage heat pump module includes at least two compressors, a condenser module, at least two throttling devices, and an evaporator module. Both the evaporator module and the condenser module include fin arrays and at least two sets of refrigerant pipelines passing through the fin arrays, and these sets of refrigerant pipelines are arranged in a staggered and nested manner; one compressor, one set of refrigerant pipelines of the condenser, one throttling device, and one set of refrigerant pipelines of the evaporator are sequentially connected to form a refrigerant circulation loop of a set of heat pump subsystems; If the difference between the energy output of the condenser group and the heat load demand is greater than the condenser heat output of 1 set of fixed-frequency heat pump units, the controller increases or decreases the operation of 1 set of fixed-frequency heat pump units until the difference is less than the condenser output of 1 set of fixed-frequency heat pump units; when the difference between the energy output of the condenser group to the heated medium channel and the heat load demand is less than the condenser heat output of 1 set of fixed-frequency heat pump units, the controller adjusts the compressor speed and refrigerant circulation volume of the variable-frequency heat pump unit by putting into operation the variable-frequency heat pump unit to adjust the condenser heat output of the variable-frequency heat pump unit, thereby adjusting the total energy output of the entire cascaded heat pump system until the difference is gradually reduced to within the energy output control accuracy range and then stabilizing the speed of the variable-frequency compressor.

2. The cascade heat pump system for realizing wide-range continuous adjustment of condenser energy output according to claim 1, wherein, The variable-frequency heat pump unit controls and adjusts the speed of the compressor motor through a variable-frequency power module.

3. The cascade heat pump system for achieving wide-range continuous adjustment of the condenser energy output according to claim 2, wherein A blower is provided on one side of the evaporator of the variable-frequency heat pump unit; Radiating fins are provided on the variable-frequency power module, and the heat dissipation channels between the radiating fins are communicated with the air inlet of the blower.

4. A cascaded heat pump system for achieving wide-range continuous adjustment of the energy output of a condenser, as described in claim 3, characterized in that The evaporator of the variable-frequency heat pump unit is arranged in an air flow channel, and the blower is arranged at the outlet of the air flow channel; a flow guide cover is provided outside the air flow channel, and the flow guide cover is communicated with the outlet of the air flow channel and the external environment respectively; the radiating fins of the variable-frequency power module are arranged in the flow guide cover.

5. A cascade heat pump system for achieving wide-range continuous adjustment of condenser energy output according to claim 2, characterized in that A water pump is provided on one side of the evaporator of the variable-frequency heat pump unit; Radiating fins are provided on the variable-frequency power module, and the heat dissipation channels between the radiating fins are communicated with the water inlet of the water pump.

6. The cascade heat pump system for realizing wide-range continuous regulation of condenser energy output according to claim 5, wherein, The evaporator of the variable-frequency heat pump unit is arranged in the water flow channel, and the water pump is arranged at the outlet of the water flow channel; a flow guide cover is arranged outside the water flow channel, and the flow guide cover communicates with the outlet of the water flow channel and the water body environment respectively; the heat dissipation fins of the variable-frequency power supply module are arranged in the flow guide cover.

7. A cascaded heat pump system for achieving wide-range continuous adjustment of condenser energy output as described in claim 1, characterized in that The condensers of the variable-frequency heat pump unit and the fixed-frequency heat pump unit are both arranged in a duct, and all the condensers are arranged at intervals from the inlet of the duct to the outlet of the duct.

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