Multi-head centrifugal unit with high load shedding performance

Abstract

The utility model provides a multi-head centrifugal unit with high load shedding performance, which comprises a parallel unit formed by connecting a single-stage compressor and an N-stage compressor in parallel, the evaporator is respectively connected with the inlet end of the single-stage compressor and the first inlet end of the N-stage compressor, the condenser is respectively connected with the outlet end of the single-stage compressor and the outlet end of the N-stage compressor, and the first economizer, the second economizer,..., and the (N-1) th economizer are respectively connected with the second inlet end, the third inlet end,..., and the Nth inlet end of the N-stage compressor. A single-stage compression large-cooling-capacity compressor and a double-stage compression small-cooling-capacity compressor are mixed and matched to form the double-stage compression system, so that the performance of the whole machine is improved under the condition that the performance of the single-stage compression compressor is not changed. The two-stage compression small-cooling-capacity compressor is adopted in single-machine-head operation, the minimum load shedding cooling capacity of a unit is small, the unit is a two-stage compression system, hot gas bypass measures do not need to be configured, load shedding performance is improved, full-load unit performance is improved, the whole machine IPLV is improved, for example, the whole machine performance of a 200RT + 700RT system is improved by 1-2%, and the partial load performance is improved by 1.5-3%. And the IPLV of the whole machine is improved by 1-3%.

Description

Technical Field

[0001] The utility model belongs to the technical field of compressor throttling, and in particular relates to a multi-head centrifugal unit with high load reduction performance. Background Art

[0002] At present, industrial users in the market have high requirements for the load shedding capacity of chillers, requiring them to operate 24 hours a day without stopping. The existing centrifugal chillers, when equipped with hot gas bypass, have a load shedding capacity of at least 10%, which still cannot meet the needs of industrial users. If the hot gas bypass is turned on, the performance of the unit will be reduced. Therefore, the existing single-stage compressor can only use a one-stage throttling system, which has poor unit performance and IPLV (integrated part load performance coefficient) compared to the two-stage compression system.

[0003] The existing technology uses two single-stage compression compressors with similar cooling capacity for mixing, which has the following disadvantages: after mixing, the unit is still a one-stage throttling system, and the unit performance is poor; when a single head is running, the unit's load reduction capacity is limited, the unit needs to be equipped with hot gas bypass, and the load performance is poor. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a multi-head centrifugal unit with high load reduction performance, which is used to improve the performance of the whole machine without changing the performance of the compressor of the single-stage compression.

[0005] The utility model adopts the following technical scheme to solve the above-mentioned technical problems: a high-load-reducing-performance multi-head centrifugal unit, comprising a parallel unit consisting of a single-stage compressor and an N-stage compressor connected in parallel, and also comprising an evaporator respectively connected to the inlet end of the single-stage compressor and the first inlet end of the N-stage compressor, a condenser respectively connected to the outlet end of the single-stage compressor and the outlet end of the N-stage compressor, a first economizer, a second economizer, ..., an (N-1)th economizer respectively connected to the second inlet end, the third inlet end, ..., the Nth inlet end of the N-stage compressor, and a first throttling device, a second throttling device, ..., an Nth throttling device connected in series in sequence among the condenser, the first economizer, the second economizer, ..., the (N-1)th economizer and the throttling device, N≥2; the cooling capacity of the single-stage compressor is greater than that of the multi-stage compressor.

[0006] According to the above scheme, it also includes a first valve, a second valve, ..., a (N-1)th valve connected in series between the second inlet end, the third inlet end, ..., the Nth inlet end of the N-stage compressor and the first economizer, the second economizer, ..., the (N-1)th economizer, respectively; an Nth valve connected in series between the first inlet end of the N-stage compressor and the evaporator; and an i'th valve connected in series between the first inlet end of the N-stage compressor and the i-th economizer, i=1, 2, ..., N.

[0007] Further, the i'th valve is closed, and the first valve, the second valve, ..., and the (N-1)th valve are opened. The single-stage compressor and the N-stage compressor are operated in parallel, and the system is an N-stage throttling intermediate incomplete cooling system.

[0008] Further, the i'th valve is opened, and the first valve, the second valve, ..., the (N-1)th valve are closed, and the single-stage compressor and the N-stage compressor are operated simultaneously, and the N-stage compressor is an air supplement and enthalpy increase device of the single-stage compressor.

[0009] Further, the i'th valve is closed, the first valve, the second valve, ..., the (N-1)th valve are opened, the single-stage compressor is closed, the N-stage compressor is operated alone, and the system operates at a small load.

[0010] According to the above scheme, the cooling capacity ratio of the multi-stage compressor and the single-stage compressor ranges from 0.1 to 0.5.

[0011] According to the above scheme, the rated maximum cooling capacity of the parallel unit is the sum of the cooling capacities of the single-stage compressor and the N-stage compressor.

[0012] Furthermore, when N=2, the parallel unit is composed of a 700RT single-stage compressor and a 200RT two-stage compressor in parallel; when N=3, the parallel unit is composed of a 700RT single-stage compressor and a 200RT three-stage compressor in parallel.

[0013] According to the above scheme, the parallel unit is a chiller.

[0014] According to the above scheme, the parallel unit is a heat pump unit.

[0015] The beneficial effects of the utility model are:

[0016] 1. The utility model is a high load-reducing performance multi-head centrifugal unit that is a two-stage throttling intermediate incomplete cooling system. By mixing a single-stage compression compressor with a large cooling capacity and a two-stage compression compressor with a small cooling capacity into a two-stage compression system, the performance of the entire machine is improved without changing the performance of the single-stage compression compressor.

[0017] 2. The single-head operation of the utility model adopts a two-stage compression compressor with a small cooling capacity, which makes the minimum cooling capacity of the unit load reduction small and is a two-stage compression system. There is no need to configure hot gas bypass measures, which improves the load reduction performance, improves the full-load unit performance, and improves the IPLV of the whole machine: taking the 200RT+700RT system combination as an example, the performance of the whole machine is improved by 1~2%, the partial load performance is improved by 1.5~3%, and the IPLV of the whole machine is improved by 1~3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a principle block diagram of a two-stage compression chiller system according to an embodiment of the utility model.

[0019] Figure 2 It is a principle block diagram of a three-stage compression chiller system according to an embodiment of the utility model. DETAILED DESCRIPTION

[0020] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] Example 1

[0022] See also Figure 1 This embodiment adopts a scheme of mixing two centrifugal machines with large and small cooling capacities. The mixed unit is a two-stage throttling intermediate incomplete cooling system; the large cooling capacity centrifugal compressor adopts a single-stage compression 700RT compressor, and the small cooling capacity centrifugal compressor adopts a two-stage compression 200RT compressor; the rated maximum cooling capacity of the two compressors in parallel is 900RT; the ratio range of large and small cooling capacities is that the cooling capacity of the two-stage compression compressor is within the range of 10% to 50% of the cooling capacity of the single-stage compression compressor. According to the size of the customer's cooling capacity, the system operation includes the following modes:

[0023] Mode 1: When the customer's cooling capacity is in the range of 750RT to 900RT, the 700RT compressor and the 200RT compressor operate in parallel, valve 2 is closed, and valves 1 and 3 are opened; the performance of the entire machine is improved through two-stage compression without changing the performance of the 700RT compressor.

[0024] The two compressors absorb low-temperature, low-pressure saturated gas from the evaporator respectively, and after being compressed into high-temperature, high-pressure superheated gas by the compressor, they are condensed into high-temperature, high-pressure subcooled liquid in the condenser; after the first-stage throttling, the gas-liquid mixed gas enters the economizer for gas-liquid separation. The liquid after the first-stage throttling enters the evaporator after the second-stage throttling, and the gas after the first-stage throttling enters the air supply pipeline of the 200RT compressor through valve 1; the low-temperature, low-pressure gas-liquid mixed gas entering the evaporator through the second-stage throttling absorbs heat in the evaporator, and enters the 700RT compressor and the 200RT compressor for compression, thus completing the entire cycle.

[0025] Mode 2: When the customer's cooling capacity is within the range of 200RT to 750RT, the 700RT compressor and the 200RT compressor operate simultaneously, valve 2 is opened, and valves 1 and 3 are closed; at this time, the 200RT compressor is used as an air supply and enthalpy increase device for the 700RT compressor, and the air supply gas is pressurized from the intermediate pressure to the condensing pressure through the 200RT compressor, the lifting force becomes smaller, the labor consumption is reduced, and the unit performance is improved.

[0026] The 700RT compressor absorbs low-temperature, low-pressure saturated gas from the evaporator, which is compressed into high-temperature, high-pressure superheated gas by the compressor and condensed into high-temperature, high-pressure subcooled liquid in the condenser; after the first-stage throttling, the gas-liquid mixed gas enters the economizer for gas-liquid separation. The liquid after the first-stage throttling enters the evaporator after the second-stage throttling, and the gas after the first-stage throttling enters the impeller inlet of the 200RT compressor through valve 2, and enters the condenser after being compressed by two-stage impellers; the low-temperature, low-pressure gas-liquid mixed gas that enters the evaporator after the second-stage throttling absorbs heat in the evaporator and enters the 700RT compressor for compression, thus completing the entire cycle.

[0027] Mode 3: When the customer's cooling capacity is below 200RT, shut down the 700RT compressor and operate the 200RT compressor alone, with valve 2 closed and valves 1 and 3 open; the unit's loading capacity is below 5% without opening the hot gas bypass, which improves the low-load operation performance.

[0028] The 200RT compressor absorbs low-temperature, low-pressure saturated gas from the evaporator; after being compressed into high-temperature, high-pressure superheated gas by the compressor, it is condensed into high-temperature, high-pressure subcooled liquid in the condenser; after the first-stage throttling, the gas-liquid mixed gas enters the economizer for gas-liquid separation. The liquid after the first-stage throttling enters the evaporator after the second-stage throttling, and the gas after the first-stage throttling enters the air supply pipeline of the 200RT compressor through valve 1; the low-temperature, low-pressure gas-liquid mixed gas entering the evaporator after the second-stage throttling absorbs heat in the evaporator and enters the 200RT compressor for compression, thus completing the entire cycle.

[0029] Example 2

[0030] The structure of this embodiment is the same as that of Embodiment 1, except that when the customer's cooling capacity is within the range of 200RT to 750RT, the 200RT compressor is shut down and the 700RT compressor is operated alone, and valves 1, 2 and 3 are closed.

[0031] Example 3

[0032] See also Figure 2 The principle of this embodiment is the same as that of Embodiment 1, except that a single-stage compression 700RT compressor and a three-stage compression 200RT compressor are mixed; the rated maximum cooling capacity of the two compressors in parallel is 900RT.

[0033] Example 4

[0034] The principle of this embodiment is the same as that of Embodiment 1, except that the chiller is replaced by a heat pump unit.

[0035] The above embodiments are only used to illustrate the design ideas and features of the utility model, and their purpose is to enable those skilled in the art to understand the content of the utility model and implement it accordingly. The protection scope of the utility model is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the utility model are within the protection scope of the utility model.

Claims

1. A multi-head centrifugal unit with high load reduction performance, characterized in that: The invention comprises a parallel unit consisting of a single-stage compressor and an N-stage compressor connected in parallel, and further comprises an evaporator respectively connected to the inlet end of the single-stage compressor and the first inlet end of the N-stage compressor, a condenser respectively connected to the outlet end of the single-stage compressor and the outlet end of the N-stage compressor, a first economizer, a second economizer, ..., an (N-1)th economizer respectively connected to the second inlet end, the third inlet end, ..., the Nth inlet end of the N-stage compressor, and a first throttling device, a second throttling device, ..., an Nth throttling device connected in series in sequence among the condenser, the first economizer, the second economizer, ..., the (N-1)th economizer and the throttling device, N≥2; the cooling capacity of the single-stage compressor is greater than that of the multi-stage compressor.

2. A multi-head centrifugal unit with high load reduction performance according to claim 1, characterized in that: It also includes a first valve, a second valve, ..., and an (N-1)th valve connected in series between the second inlet end, the third inlet end, ..., the Nth inlet end of the N-stage compressor and the first economizer, the second economizer, ..., and the (N-1)th economizer, respectively, an Nth valve connected in series between the first inlet end of the N-stage compressor and the evaporator, and an i'th valve connected in series between the first inlet end of the N-stage compressor and the i-th economizer, i=1, 2, ..., N.

3. A multi-head centrifugal unit with high load reduction performance according to claim 2, characterized in that: Close the i'th valve, open the first valve, the second valve, ..., the (N-1)th valve, the single-stage compressor and the N-stage compressor run in parallel, and the system is an N-stage throttling intermediate incomplete cooling system.

4. A multi-head centrifugal unit with high load reduction performance according to claim 2, characterized in that: The i'th valve is opened, and the first valve, the second valve, ..., and the (N-1)th valve are closed. The single-stage compressor and the N-stage compressor operate simultaneously. The N-stage compressor is an air supplement and enthalpy increase device for the single-stage compressor.

5. The high load-reducing performance multi-head centrifugal unit according to claim 2, characterized in that: The i'th valve is closed, and the first valve, the second valve, ..., the (N-1)th valve are opened, the single-stage compressor is closed, and the N-stage compressor is operated alone, and the system operates at a small load.

6. The high load-reducing performance multi-head centrifugal unit according to claim 1, characterized in that: The cooling capacity ratio of a multi-stage compressor to a single-stage compressor ranges from 0.1 to 0.

5.

7. The high load-reducing performance multi-head centrifugal unit according to claim 1, characterized in that: The rated maximum cooling capacity of the parallel unit is the sum of the cooling capacities of the single-stage compressor and the N-stage compressor.

8. A multi-head centrifugal unit with high load reduction performance according to any one of claims 1 to 4, characterized in that: When N=2, the parallel unit is composed of a 700RT single-stage compressor and a 200RT two-stage compressor in parallel; When N=3, the parallel unit is composed of a 700RT single-stage compressor and a 200RT three-stage compressor in parallel.

9. The high load-reducing performance multi-head centrifugal unit according to claim 1, characterized in that: The parallel unit is a chiller.

10. The high load-reducing performance multi-head centrifugal unit according to claim 1, characterized in that: The parallel unit is a heat pump unit.

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