CN107144040B

CN107144040B - Multistage compression double-compressor parallel piston type carbon dioxide heat pump system

Info

Publication number: CN107144040B
Application number: CN201710385497.7A
Authority: CN
Inventors: 李敏霞; 陈振国; 王派; 詹浩淼; 马一太; 唐维祎; 陈齐飞; 张正韬; 瑚彩玲; 邵亚伟
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2017-05-26
Filing date: 2017-05-26
Publication date: 2023-09-08
Anticipated expiration: 2037-05-26
Also published as: CN107144040A

Abstract

The invention relates to the technical field of large-scale heat supply, and discloses a multistage compression double-compressor parallel piston type carbon dioxide heat pump system, wherein an outlet of an evaporator is connected with a low-pressure stage compression unit, the low-pressure stage compression unit is formed by parallel opposition of identical first compressors and second compressors, the low-pressure stage compression unit is connected with an inlet of a third compressor through a first stage air cooler, an outlet of the third compressor is connected with an inlet of an expander through a second stage air cooler, and an outlet of the expander is connected with an inlet of the evaporator through an auxiliary throttle valve; the first compressor, the second compressor and the third compressor are coaxial, the third compressor is used as a high-pressure stage compression unit and is coaxially opposite to the expander, and part of expansion work is recovered. According to the invention, the double-cylinder compressors of the multi-stage compression and low-pressure stage compression units are opposite, the high-pressure stage compression units are opposite to the expansion machine, so that the noise is reduced, the efficiency of the compressor is improved, the effects of energy conservation and emission reduction are achieved, and the large-scale piston is adopted to greatly improve the power of the heat pump system, so that the heat pump system can replace heating equipment such as boilers.

Description

Multistage compression double-compressor parallel piston type carbon dioxide heat pump system

Technical Field

The invention relates to the technical field of large heating, in particular to a heat pump circulation system using carbon dioxide as a working medium, which is applied to large heating engineering.

Background

The heat pump is a renewable energy exploitation machine, which exploits several times of renewable energy with one part of electric energy or mechanical energy, and is an important energy-saving technology and an environment-friendly technology. The heat pump manufacturing industry is greatly developed, the heat pump technology is greatly popularized, and the coal-to-electricity conversion is an important measure for realizing coal-free.

Carbon dioxide as a heat pump working medium can be traced back to the beginning of the 20 th century. Carbon dioxide is nontoxic and safer, so that it has been used for 50 years in marine refrigerators. Since carbon dioxide has an ozone depletion index of 0, the Global Warming Potential (GWP) is only 1. The heat pump system can reduce environmental pollution when being used as a working medium of the heat pump system. And the carbon dioxide working medium is a byproduct of a plurality of energy reactions and is easy to prepare. The carbon dioxide working medium is not decomposed to generate toxic gas at high temperature, and has good safety and chemical stability.

The carbon dioxide has high refrigerating capacity per unit volume, good fluidity, reduced size of the compressor and system, and simplified heat supply system. Carbon dioxide has higher heat conductivity, and improves the heat exchange performance of the heat pump system. The pressure of the carbon dioxide heat pump system is 7-8 times that of the common heat pump system, wherein the expansion valve pressure difference is large, and the throttling loss is large.

In order to achieve the purpose of changing coal into electricity by utilizing the carbon dioxide heat pump technology, the heat load of a heat pump system is required to be improved. For a refrigerating unit with larger cooling capacity, a single compressor unit with larger cooling capacity has certain limitation on unit load, and the refrigerating (heating) capacity is smaller, so that the demand is difficult to reach; for high-capacity (heat) units, many manufacturers are in a vacuum zone in this region, thus creating a multi-head unit. The multi-head unit is assembled by adopting a plurality of compressor units, which occurs not because of the superiority of the system, but rather is a non-trivial choice of manufacturers for market demands. The more the operating components of the unit, the poorer the continued reliability. The multi-head unit is provided with a plurality of compressors, one set of controller is used for controlling a plurality of control elements, the system is complex, the equipment is multiple, the reliability of the unit is relatively low, the service life is relatively short, and the refrigerating capacity (heating capacity) of the unit is still limited.

The lubricating oil is a lubricating agent of the heat pump air conditioning system and has the effects of reducing the abrasion of mechanical parts, reducing the friction temperature of a mechanism, enhancing the sealing performance and the like. When the refrigerating unit is operated, a part of lubricating oil inevitably enters the whole refrigerating system along with refrigerant gas to participate in refrigeration cycle. The lubricating oil forms a layer of oil film on the inner surface of the coil pipe after entering the evaporator or the condenser along with the refrigerant, and the heat conduction coefficient of the layer of oil film is smaller, so that the heat transfer resistance of the heat exchanger is directly increased, the heat exchange performance is affected, the heat exchange efficiency is reduced, and the running resistance is increased. Research shows that when the circulation amount of the lubricating oil exceeds 3% in an evaporator of a refrigeration system, the heat exchange capacity will deteriorate and the pressure loss will increase; when the circulation amount of the lubricating oil in the evaporator reaches 5%, the attenuation of the refrigerating capacity can reach more than 10%, the power consumption is increased, and the refrigerating capacity of the system is greatly reduced.

Compressors with multi-stage compression intercooling configurations typically have different cylinders connected by a mechanism. When the motor is driven, the inertial force and the moment of inertia in the mechanism can cause the vibration of the mechanism, particularly in a mechanical device running at a high speed, the vibration influence is serious, the vibration of the mechanism can cause the influence of noise and the like, and the development of the mechanism to a high-precision direction is hindered.

Disclosure of Invention

The invention aims to solve the technical problems that the existing heat pump has lower heating engineering power and is difficult to meet the requirement of large load, and provides a multistage compression double-compressor parallel piston carbon dioxide heat pump system, which has the advantages that the double-cylinder compressors of a multistage compression unit and a low-pressure compression unit are opposite, and the high-pressure compression unit is opposite to an expander, so that the power of the heat pump system is greatly improved, the heat pump system can replace heating equipment such as a boiler, the power can reach 1000KW, the noise is reduced, the efficiency of the compressor is improved, and the effects of energy conservation and emission reduction are achieved; and simultaneously, the exhaust temperature is reduced, hot water is generated, and the power consumption is reduced.

In order to solve the technical problems, the invention is realized by the following technical scheme:

the utility model provides a parallelly connected piston carbon dioxide heat pump system of multistage compression double-compressor, this system includes evaporimeter (1), the entry of low-pressure stage compression unit is connected to the export of evaporimeter (1), low-pressure stage compression unit comprises identical first compressor (2), parallelly connected opposition of second compressor (3), the entry of first stage air cooler (4) is connected to the export of low-pressure stage compression unit, the entry of third compressor (6) is connected to the export of first stage air cooler (4), the entry of second stage air cooler (7) is connected to the export of third compressor (6), the entry of expander (9) is connected to the export of second stage air cooler (7), the entry of auxiliary throttle valve (10) is connected to the exit of expander (9), the entry of auxiliary throttle valve (10) is connected.

The first compressor (2), the second compressor (3) and the third compressor (6) are all connected to the motor (11) through the same main shaft and driven by the motor (11), the third compressor (6) is used as a high-pressure stage compression unit and is coaxially opposite to the expander (9), the expander (9) is also connected to the main shaft, and the third compressor (6) is driven to recover expansion work.

The first compressor (2), the second compressor (3) and the third compressor (6) are all piston-type and all adopt large pistons, and the expander (9) is also piston-type.

The first-stage air cooler (4) is arranged in the first water tank (5), and the second-stage air cooler (7) is arranged in the second water tank (8).

The beneficial effects of the invention are as follows:

the multistage compression double-compressor parallel piston type carbon dioxide heat pump system is applied to large-scale heat supply engineering, and the unit power can reach 1000KW. The heat pump system uses carbon dioxide as a working medium, adopts a multi-stage compression and intermediate cooling mode, improves the unit power, reduces the exhaust temperature, and utilizes the heat released during intermediate cooling through a gas cooler.

The low-pressure stage compression unit comprises two compressors which are oppositely connected in parallel, so that mechanical balance is achieved, the influence of primary inertia force and primary inertia moment of a connecting mechanism is reduced, and the effect of noise elimination is achieved; the compressor of the high-pressure stage compression unit and the expander are coaxially arranged, and mechanical work output by the expander drives the high-pressure stage compressor so as to recover an expansion work part; the low-pressure stage compression unit and the high-pressure stage compression unit both adopt multi-stage compression formed by large pistons, so that the efficiency of the compressor can be improved by 20-30%; thereby improving the reliability of the heat pump system, obviously improving the power of the unit, and enabling the power to reach 1000KW; therefore, the application range of the heat pump can be increased, and the heat pump can replace a boiler and a central air conditioner and can be used as a more energy-saving and environment-friendly heat supply device.

The air cooler part is used for recovering surplus heat and heating water for heating, so that energy consumption is saved; the water with different temperatures in the two-stage water tank can be respectively utilized as the water for heating with lower temperature requirement and the water for heating with higher temperature requirement.

Drawings

FIG. 1 is a schematic diagram of a multistage compression dual-compressor parallel piston carbon dioxide heat pump system provided by the invention;

fig. 2 is a schematic illustration of three compressors and expanders coaxially connected.

In the figure: 1, an evaporator; 2, a first compressor; 3, a second compressor; 4, a first-stage air cooler; 5, a first water tank; 6, a third compressor; 7, a second-stage air cooler; 8, a second water tank; 9, an expander;

10, an auxiliary throttle valve; and 11, a motor.

Detailed Description

For a further understanding of the nature, features, and effects of the present invention, the following examples are set forth to illustrate, and are to be considered in connection with the accompanying drawings:

as shown in fig. 1, the present embodiment discloses a multi-stage compression dual-compressor parallel piston carbon dioxide heat pump system, which comprises an evaporator 1, a first compressor 2, a second compressor 3, a first stage air cooler 4, a first water tank 5, a third compressor 6, a second stage air cooler 7, a second water tank 8, an expander 9, an auxiliary throttle valve 10 and a motor 11. The first compressor 2 and the second compressor 3 are oppositely connected in parallel to serve as a low-pressure stage compression unit, and working media equally pass through the first compressor 2 and the second compressor 3 and are compressed at the same time. The third-stage compressor 6 is coaxially opposed to the expander 9 as a high-pressure stage compression unit, and the third-stage compressor 6 recovers expansion work.

The outlet of the evaporator 1 is connected with the inlet of a low-pressure stage compression unit, the low-pressure stage compression unit is formed by connecting and oppositely arranging a first compressor 2 and a second compressor 3 which are identical, the outlet of the low-pressure stage compression unit is connected with the inlet of a first-stage air cooler 4, the outlet of the first-stage air cooler 4 is connected with the inlet of a third compressor 6, the outlet of the third compressor 6 is connected with the inlet of a second-stage air cooler 7, the outlet of the second-stage air cooler 7 is connected with the inlet of an expander 9, the outlet of the expander 9 is connected with the inlet of an auxiliary throttle valve 10, and the outlet of the auxiliary throttle valve 10 is connected with the inlet of the evaporator 1.

Wherein, the first compressor 2, the second compressor 3 and the third compressor 6 are all piston type, and the expander 9 is also piston type. The first compressor 2, the second compressor 3, and the third compressor 6 are large pistons, and the large pistons are pistons that can divide the cooling capacity or heating capacity of the unit to 600kw or more. The motor 11 drives the first compressor 2, the second compressor 3 and the third compressor 6 to work through the same main shaft; the expander 9 is also connected to the same main shaft, and the mechanical work output by the expander 9 can drive the third compressor 6 to recover part of the expansion work.

The first compressor 2 and the second compressor 3 are opposed in parallel, which means that the first compressor 2 and the second compressor 3 are connected to the same main shaft and have the same eccentricity as the main shaft. The third compressor 6 and the expander 9 are coaxially opposed to each other, and the third compressor 6 and the expander 9 are connected to the same main shaft and have the same eccentricity as the main shaft. Thus, the balance in mechanical aspect between the first compressor 2 and the second compressor 3 and between the third compressor 6 and the expander 9 can be achieved, the influence of primary inertia force and moment of inertia is reduced, the purpose of noise elimination is achieved, meanwhile, the motion precision and the motion balance of the mechanism are improved, the abrasion and fatigue failure of parts are reduced, the service life is prolonged, and the running stability is ensured.

The selection of the large-sized piston, the parallel connection of the first compressor 2 and the second compressor 3 as a low-pressure stage compression unit and the design of the third compressor 6 as a high-pressure stage compression unit can improve the compression ratio, improve the power of a unit and achieve the effect of improving the heating capacity (refrigerating capacity). When the refrigerating capacity or the heating capacity is large, the size of the piston is correspondingly large, and the rotating speed is not too high, so that the linear speed is preferably not more than 10m/s in order to ensure the safety and stability of the unit. When the rotating speed is slower, the lubricating oil can not be used for lubricating, meanwhile, the sealing gasket is used for replacing the sealing effect of the original lubricating oil, the lubricating oil in the first compressor 2, the second compressor 3, the third compressor and the expander 9 can be well sealed, oil-free operation of the system can be basically realized, the leakage problem of the lubricating oil is better prevented, and the heat exchange efficiency is further improved.

The first-stage air cooler 4 and the second-stage air cooler 7 are used for recovering redundant heat, so that energy consumption is saved. The first stage air cooler 4 is arranged in the first water tank 5 and the second stage air cooler 7 is arranged in the second water tank 8. The higher temperature working medium passes through the first stage air cooler 4 to heat the water in the first water tank 5 for heating with lower temperature requirement; the high-temperature working medium passes through the second-stage air cooler 7 to heat water in the second water tank 8 for heating at a higher temperature. The water temperatures in the first water tank 5 and the second water tank 8 are different, and the water temperatures can be respectively installed in environments with different temperature demands for separate utilization, so that the energy utilization efficiency is improved.

The invention relates to a multistage compression double-compressor parallel piston type carbon dioxide heat pump system, which comprises the following working processes:

the motor 11 drives the system to operate, carbon dioxide working medium enters the low-pressure stage compression unit from the evaporator 1, and the working medium is uniformly divided into two parts and enters the first compressor 2 and the second compressor 3. After two parts of working media are compressed for the first time simultaneously, the working media enter the first-stage air cooler 4 from the low-pressure-stage compression unit, heat exchange is carried out on the working media with water in the first water tank 5 through the first-stage air cooler 4, the water is heated for the first time, and the working media are subjected to isobaric cooling, so that the temperature is reduced. The working medium enters the third compressor 6 through the first-stage air cooler 4 to be subjected to a second compression process, and enters the second-stage air cooler 7 after being subjected to the second compression process, so that the temperature of the working medium is reduced and water in the second water tank 8 is heated. The working medium is subjected to a two-stage compression intermediate cooling process, so that the final temperature of exhaust is reduced, compression work is saved, and the efficiency is improved. The working medium enters the expander 9 from the second-stage air cooler 7, the expander 9 and the third compressor 6 are both piston-type and coaxially rotate, and the expansion work can be recovered by the third compressor 6. The working medium is reduced in temperature and increased in density after intermediate cooling, is easy to further compress, and can greatly save the work consumption compared with one-time compression. After the expansion process is completed, the working medium returns to the evaporator 1 through the auxiliary throttle valve 10, the refrigeration process is completed, and the circulation can be repeatedly performed.

Therefore, the multistage compression double-compressor parallel piston type carbon dioxide heat pump system improves the compression ratio and the heating capacity (refrigerating capacity) in a multistage compression intermediate cooling mode by adopting the large-scale pistons to be connected in parallel in a grading manner, so that the power of the multistage compression double-compressor parallel piston type carbon dioxide heat pump system can reach 1000KW; the oil-free operation can be realized by using the large piston and the gasket seal, and the heat exchange efficiency is improved; the parallel opposite and coaxial opposite design can reduce the influence of primary inertia force and moment of inertia, reduce noise, prolong the service life of the system, improve efficiency and ensure the running stability of the system; therefore, the whole system is reliable in operation and excellent in overall effect, can replace the power of a boiler and a central air conditioner, and improves the utilization range of the heat pump.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings and preferred embodiments, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many changes may be made by those having ordinary skill in the art without departing from the spirit of the invention and the scope of the appended claims, which are to be construed as falling within the scope of the present invention.

Claims

1. The multistage compression double-compressor parallel piston type carbon dioxide heat pump system comprises an evaporator (1), and is characterized in that an outlet of the evaporator (1) is connected with an inlet of a low-pressure stage compression unit, the low-pressure stage compression unit is formed by parallel and opposite arrangement of a first compressor (2) and a second compressor (3) which are identical, an outlet of the low-pressure stage compression unit is connected with an inlet of a first stage air cooler (4), an outlet of the first stage air cooler (4) is connected with an inlet of a third compressor (6), an outlet of the third compressor (6) is connected with an inlet of a second stage air cooler (7), an outlet of the second stage air cooler (7) is connected with an inlet of an expander (9), an outlet of the expander (9) is connected with an inlet of an auxiliary throttle valve (10), and an outlet of the auxiliary throttle valve (10) is connected with an inlet of the evaporator (1);

the first compressor (2), the second compressor (3) and the third compressor (6) are all connected to a motor (11) through the same main shaft and driven by the motor (11), the third compressor (6) is used as a high-pressure stage compression unit and is coaxially opposite to the expander (9), the expander (9) is also connected to the main shaft, and the third compressor (6) is driven to recover expansion work;

the first compressor (2), the second compressor (3) and the third compressor (6) are all piston-type and all adopt large pistons, and the expander (9) is also piston-type;