A parallel high-power heat pump refrigeration unit

Abstract

The present invention discloses a parallel high-power heat pump refrigeration unit, including: a compressor, an evaporator, a condenser, an economizer, and a throttling device. The compressor is a centrifugal compressor, generally having two or more stages, connected to the evaporator and the condenser, and having the characteristics of high speed, large pressure ratio, high output power, etc. The centrifugal heat pump has the characteristics of large capacity and high efficiency, but is limited by the development level of supporting technologies such as motors and bearings. The speed that the motor can achieve does not match the speed required by the pneumatic design of the compressor, which poses a huge challenge to the improvement of compressor efficiency and the development of large-capacity heat pump refrigeration units. A heat pump refrigeration unit disclosed in the present invention solves the contradiction between the motor speed and the compressor design speed through a unique parallel scheme and a reasonable layout of important components, and obtains the technical effect of simultaneously improving the circulating refrigeration / heating capacity of the unit and the working efficiency of the compressor.

Description

Technical Field

[0001] The invention relates to the technical field of heating, ventilation and air conditioning and heat pumps, and in particular to a parallel high-power heat pump refrigeration unit. Background Art

[0002] A heat pump is an efficient and energy-saving system that makes full use of low-grade thermal energy. It obtains more high-grade thermal energy for direct use while consuming a small amount of electrical power. During the process of compressing the working medium, as the pressure increases, the temperature of the working medium will increase significantly, and the corresponding compression power consumption will also increase. Due to the limitations of the thermal stability temperature of the working medium, the complexity of the aerodynamic design, the sealing of the rotating parts, and the balance of the axial thrust, when the power of a single heat pump unit is increased from hundreds of kilowatts to megawatts, high temperature, high pressure, large pressure ratio, and high speed become important bottlenecks for increasing the power of a single heat pump unit.

[0003] In particular, due to the limitations of the current development level of important supporting components such as motors and bearings, the speed that the motor can achieve is extremely mismatched with the speed required by the high-parameter pneumatic design of the compressor, resulting in the inability to improve the efficiency of the compressor. It is even more difficult to develop a single large-capacity heat pump refrigeration unit.

[0004] For heat pump units with higher condensing temperatures, including high-temperature heat pumps that provide hot water and steam-type ultra-high-temperature heat pumps that directly generate high-temperature steam, the increase in power and COP of a single heat pump unit can significantly reduce the equipment cost corresponding to unit power, and will achieve very obvious technical advantages in market applications. The compressors of existing heat pump units mainly include screw compressors, scroll compressors, centrifugal compressors, etc. The power of a single unit is only tens to hundreds of kilowatts. Heat pump refrigeration units with high system COP and single unit power exceeding megawatts are basically blank.

[0005] In response to the important bottlenecks and technical gaps described above, this patent proposes a parallel high-power heat pump refrigeration unit that can solve the serious mismatch between the motor speed and the speed required by the pneumatic design, and the problem of the inability to coordinate the unit capacity increase with ultra-high design parameters and requirements. Summary of the invention

[0006] The purpose of the present invention is to provide a parallel high-power heat pump refrigeration unit to solve the design and layout problems of high-power heat pump units under high temperature, high pressure, large pressure ratio and high speed mentioned in the above background technology, especially the serious mismatch problem between the motor speed and the speed required by the pneumatic design, thereby greatly improving the power of a single heat pump refrigeration unit and realizing high-parameterized design and low-cost large-scale use of high-power heat pump refrigeration units.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a parallel high-power heat pump refrigeration unit, comprising: a compressor, a condenser, a throttling device, an economizer, and an evaporator. The compressor, condenser, throttling device, economizer and evaporator are connected in sequence to form a closed cycle. The outlet end of the compressor is connected to the condenser, and the outlet end of the condenser is connected to the inlet of the economizer. The economizer is provided with two outlets, and the two outlets of the economizer are respectively connected to the outlet end of the low-pressure compressor and the inlet end of the evaporator. The evaporator comprises a first evaporator and a second evaporator. The first evaporator and the second evaporator adopt a unique parallel scheme in the layout of the unit equipment.

[0008] Preferably, the compressor comprises a low-pressure compressor and a high-pressure compressor.

[0009] Preferably, the low-pressure compressor and the high-pressure compressor form a two-stage compression.

[0010] Preferably, the low-pressure compressor and the high-pressure compressor include a motor, an impeller and a high-speed rotating shaft, the high-speed rotating shaft is mounted at both ends of the motor, and the impeller is mounted on the high-speed rotating shaft.

[0011] Preferably, the low-pressure compressor drives two impellers on the same rotating shaft to operate in parallel, and the high-pressure compressor drives two impellers on the same rotating shaft to operate in parallel;

[0012] Preferably, a first throttling device is provided at the inlet of the economizer.

[0013] Preferably, the evaporator inlet is provided with a second throttling device and a third throttling device;

[0014] Preferably, the working fluid of the heat pump refrigeration group can be a mixed working fluid or a single-phase pure refrigerant.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: the parallel high-power heat pump refrigeration unit proposed by the present invention cleverly solves the problem of mismatch between the motor speed and the speed required by the pneumatic design, the irreconcilable contradiction between the capacity of a single heat pump unit and the ultra-high operating parameters, and overcomes the problem of low single-stage compression ratio and high and uncontrollable operating parameters after compression. At the same time, the use of a double impeller parallel operation mode in the same stage of compression can greatly improve the compression efficiency and output power, which is very beneficial for designing an impeller with higher pneumatic efficiency and also reduces the speed requirement for the motor. The intermediate air supply is set at the outlet of the low-pressure compressor, which can significantly improve the inlet parameters of the high-pressure compressor, further improve the compression efficiency, avoid too high working fluid parameters entering the condenser, and reduce the risk of very high pressure on the condenser. In addition, the evaporator can be made into a parallel form of graded evaporation, which is more adaptable to the temperature range of the external heat source. In particular, when the heat pump unit adopts a mixture of multiple refrigerants as the working fluid, the heat absorption temperature difference can be significantly reduced and the heat exchange power of the evaporator can be greatly improved. Accordingly, the operating parameters of the condenser do not need to be particularly high, and its heat exchange power can reach the megawatt level. The equipment cost per unit power is greatly reduced, which has a very obvious market advantage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the parallel operation of staged evaporation of the present invention;

[0017] Figure 2 This is a schematic diagram of the double impellers of a single-stage compressor operating in parallel according to the present invention;

[0018] Figure 3 This is a schematic diagram of the parallel operation of compressors when the high-pressure and low-pressure stage impellers of the present invention are coaxial.

[0019] In the figure: 1. compressor; 101. low-pressure compressor; 102. high-pressure compressor; 103. motor; 104. impeller; 105. rotating shaft; 2. condenser; 3. throttling device; 301. first throttling device; 302. second throttling device; 303. third throttling device; 4. economizer; 5. evaporator; 501. first evaporator; 502. second evaporator. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example 1: Combination Figure 1 and Figure 2The present invention provides a parallel high-power heat pump refrigeration unit, including: a low-pressure compressor 101, a high-pressure compressor 102, a condenser 2, a throttling device 3, an economizer 4, a first evaporator 501 and a second evaporator 502.

[0022] The first evaporator 501 and the second evaporator 502 are heat exchange devices running in parallel. By adjusting the second throttling device 302 and the third throttling device 303, the first evaporator 501 and the second evaporator 502 can be made to evaporate and absorb heat at different pressures respectively, so as to adapt to a heat source with a wider temperature range and fully absorb heat to maximize the amount of heat absorbed. The use of graded and parallel evaporation can effectively reduce the heat transfer temperature difference between the unit's working fluid and the heat source, improve the heat exchange efficiency, reduce the volume of the heat exchange equipment, obtain more evaporation heat absorption at the same heat exchange area, and significantly increase the unit capacity.

[0023] Similar to the principle of graded and parallel evaporation, the condenser 2 can be arranged as a first condenser 201 and a second condenser 202 at the same time, and a variety of high-efficiency heat exchange methods such as falling film and flash evaporation can be used to achieve large-capacity heat exchange under extremely low heat exchange temperature difference, making the equipment more compact.

[0024] Embodiment 2: In terms of the layout of the unit components, a parallel scheme is adopted. The unit adopts two-stage or multi-stage compression. The single-stage compressor drives two impellers 104 on the same rotating shaft 105 to run in parallel. While matching the pneumatic design speed, it not only increases the working fluid flow, but also improves the compression efficiency of the compressor 1. Combined with the principle of energy cascade utilization, the evaporator 5 and the condenser 2 connected to the compressor 1 can be connected in parallel in sections to effectively reduce the heat transfer temperature difference between the unit working fluid and the heat source / cold source, and improve the heat transfer efficiency; in order to avoid the high-pressure compressor 102 inlet parameter overheating too much, before the high-pressure compressor 102 intakes air, the intake parameters are adjusted by intermediate air supplementation. The pressure and temperature of the intermediate air supplement are adjusted by the throttling device 3 before the economizer 4. The saturated liquid working fluid inside the economizer 4 enters the evaporator 5 to absorb heat after further throttling, depressurization and temperature reduction. The working fluid of the heat pump refrigeration unit can be a single-phase pure refrigerant or a mixture of multiple refrigerants.

[0025] After absorbing heat from the first evaporator 501 and the second evaporator 502, the working fluid of the heat pump unit has different temperatures and pressures when entering the two ends of the low-pressure compressor 101, but reaches the same state point after being compressed.

[0026] The benefits of this layout are: on the one hand, it increases the circulation flow of the unit's working fluid and greatly improves the unit's power; on the other hand, the unit has a wider adaptability to heat sources and a stronger system stability. The low-pressure compressor 101 drives the dual impellers 104 to operate in parallel through the high-speed rotating shaft 105. The impellers 104 can be arranged symmetrically at both ends of the same axis, or at one end of the shaft. The impeller 104 can be an open impeller or a closed impeller.

[0027] Cold working fluid will be introduced at the outlet of the low-pressure compressor 101 for intermediate air supply, so as to adjust the superheat of the inlet of the high-pressure compressor 102, so as to avoid the problem that the working fluid at the inlet of the high-pressure compressor 102 is too superheated and the temperature and pressure of the working fluid after compression are uncontrollable. The air supply pressure of the economizer 4 is adjusted by the first throttling device 301 before the inlet; similarly, the high-pressure compressor 102 is also driven by the high-speed rotating shaft 105 to drive the double impeller 104 to operate in parallel, and reaches a high temperature and high pressure state before entering the condenser 2; the saturated liquid phase working fluid coming out of the economizer 4 becomes a gas-liquid mixed state after passing through the second throttling device 302 and the third throttling device 303, and enters the first evaporator 501 and the second evaporator 502 to absorb heat again.

[0028] In the whole cycle, the low-pressure compressor 101 and the high-pressure compressor 102 are two-stage compression, and the single-stage compression ratio does not need to be too high. When they are operated in parallel, it is beneficial to design the impeller 104 with higher aerodynamic efficiency and reduce the requirement for the speed of the motor 103. Especially when the double impellers 104 are symmetrically arranged, the axial thrust is very small, which can significantly improve the operating environment of the high-speed rotation of the compressor 1 and improve the stability and reliability of the unit operation.

[0029] Example 3: Combination Figure 2 and Figure 3 The present invention provides a parallel high-power heat pump refrigeration unit, including: a low-pressure compressor 101, a high-pressure compressor 102, a condenser 2, a first throttling device 301, a second throttling device 302, an economizer 4 and an evaporator 5.

[0030] Different from the first embodiment, for each low-pressure compressor 101 and high-pressure compressor 102, the high-speed rotating shaft 105 drives the low-pressure stage and high-pressure stage impellers 104 to operate in series, and the low-pressure compressor 101 and the high-pressure compressor 102 operate in parallel. In this case, even if one compressor does not work, the entire heat pump refrigeration unit can still operate at partial load.

[0031] 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. A parallel high-power heat pump refrigeration unit, comprising: A compressor (1), a condenser (2), a throttling device (3), an economizer (4), and an evaporator (5), characterized in that the compressor (1), the condenser (2), the throttling device (3), the economizer (4), and the evaporator (5) are connected in sequence to form a closed cycle, the outlet end of the compressor (1) is connected to the condenser (2), the outlet end of the condenser (2) is connected to the inlet end of the economizer (4), the economizer (4) is provided with two outlets, and the two outlets of the economizer (4) are respectively connected to the outlet end of the low-pressure compressor (101) and the inlet end of the evaporator (5), and the evaporator (5) comprises a first evaporator (501) and a second evaporator (502); The low-pressure compressor (101) and the high-pressure compressor (102) comprise a motor (103), an impeller (104) and a high-speed rotating shaft (105); the high-speed rotating shaft (105) is mounted at both ends of the motor (103); and the impeller (104) is mounted on the high-speed rotating shaft (105); The low-pressure compressor (101) drives two impellers (104) on the same rotating shaft to operate in parallel, and the high-pressure compressor (102) drives two impellers (104) on the same rotating shaft to operate in parallel.

2. A parallel high-power heat pump refrigeration unit according to claim 1, characterized in that: The compressor (1) comprises a low-pressure compressor (101) and a high-pressure compressor (102).

3. A parallel high-power heat pump refrigeration unit according to claim 2, characterized in that: The low-pressure compressor (101) and the high-pressure compressor (102) form a two-stage compression.

4. A parallel high-power heat pump refrigeration unit according to claim 1, characterized in that: The inlet of the economizer (4) is provided with a first throttling device (301).

5. A parallel high-power heat pump refrigeration unit according to claim 1, characterized in that: The inlet of the evaporator (5) is provided with a second throttling device (302) and a third throttling device (303).

6. A parallel high-power heat pump refrigeration unit according to claim 1, characterized in that: The working fluid of the heat pump refrigeration unit is a mixed working fluid or a single-phase pure refrigerant.

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