Background
The centrifugal refrigerating unit mainly comprises: the evaporator, the condenser, the flash tank, the throttling device and the centrifugal compressor. The evaporator is mainly used for cooling the water system by absorbing heat by the refrigerant, so as to realize refrigeration. The condenser mainly transfers the heat of the superheated gas of the refrigerant to a water system to realize the temperature reduction of the refrigerant; the flash tank is mainly used for throttling the liquid in the condenser, generating low-temperature gaseous refrigerant and sending the low-temperature gaseous refrigerant to the middle air supplement port of the centrifugal compressor, so that secondary air supplement and cooling of the compressor are realized, and the power consumption of the centrifugal compressor is reduced; the throttling device is mainly used for throttling and cooling the high-temperature and high-pressure refrigerant of the condenser to realize the pressure at the evaporator side, and the pressure change in the process is dissipated through the throttling device; the centrifugal compressor mainly has the functions of compressing the refrigerant, converting the low-temperature and low-pressure refrigerant into high-temperature and high-pressure refrigerant, and consuming electric energy in the process.
When the unit is in the normal operating process, the compressor reaches intermediate pressure through absorbing low temperature low pressure gaseous state refrigerant from the evaporimeter behind one-level compressor, and compressor gas belongs to the overheated attitude this moment, needs the flash tank to provide low temperature gas and cools down and neutralize, and the gaseous state refrigerant that only relies on pure throttling arrangement to produce among the traditional art easily appears tonifying qi and takes liquid problem, influences the operational reliability of compressor.
In addition, the compressor can have the heating of electric elements such as motor and converter in the course of the work, need in time dispel the heat in order to maintain the normal operating of refrigerating unit to heating element. As shown in fig. 1, the conventional cooling method is to use the liquid refrigerant of the condenser 2 for cooling, in order to utilize the high pressure of the condenser 2 to deliver the liquid refrigerant to the cooling branch 9 of the motor and controller 10, and the energy of the part is generated after passing through the compressor 1, thus consuming part of the power of the compressor 1, increasing the unit power consumption and reducing the unit energy efficiency.
Therefore, how to provide a centrifugal refrigerator set with an energy recovery function is an urgent technical problem to be solved in the industry.
SUMMERY OF THE UTILITY MODEL
In order to solve the defects in the prior art, the utility model provides a centrifugal refrigerating unit with an energy recovery function, which recovers excessive pressure of a refrigerating circuit by using an energy recovery device, recycles the recovered energy, reduces the refrigeration loss of a main circuit of a compressor, reduces the running power of the compressor, saves energy and improves the energy efficiency.
The technical scheme adopted by the utility model is that a centrifugal refrigerating unit is designed, and the centrifugal refrigerating unit comprises: the refrigerating circuit is connected with an energy recovery device, and when the gaseous refrigerant in the refrigerating circuit drives the energy recovery device to work, the energy recovery device sends the expanded and cooled gaseous refrigerant back to the flash evaporator.
The heat-generating device in the centrifugal refrigerating unit is cooled through the cooling branch, the outlet of the cooling branch is connected to the evaporator, and the energy recovery device absorbs the liquid refrigerant in the refrigerating circuit when working and pressurizes the liquid refrigerant and then sends the liquid refrigerant to the cooling branch.
In one embodiment, an energy recovery device comprises: the compressor comprises a shell, a rotating shaft arranged in the shell, a bearing for supporting the rotating shaft, an expansion wheel fixed at one end of the rotating shaft and a compression wheel fixed at the other end of the rotating shaft, wherein the shell is provided with an expansion chamber for accommodating the expansion wheel and a compression chamber for accommodating the compression wheel, a gaseous refrigerant flows through the expansion chamber to drive the expansion wheel to rotate, and the compression wheel sucks a liquid refrigerant in a refrigeration circuit and performs pressurization when rotating.
Preferably, the expansion chamber is provided with an air inlet and an air outlet, the air inlet of the expansion chamber is connected to the top of the heat exchange tube of the condenser, and the air outlet of the expansion chamber is connected to the liquid inlet of the flash tank.
Preferably, the compression chamber is provided with a liquid inlet and a liquid outlet, the liquid inlet of the compression chamber is connected to the bottom of the heat exchange tube of the evaporator, and the liquid outlet of the compression chamber is connected to the cooling branch.
Preferably, the throttling means comprises: the first throttling element is connected between the outlet of the condenser and the liquid inlet of the flash evaporator in series, and the second throttling element is connected between the liquid outlet of the flash evaporator and the inlet of the evaporator in series.
Preferably, the bottom of the heat exchange tube of the condenser is provided with a cooling outlet, the cooling outlet is connected to the cooling branch through a control valve, and the control valve is closed when the parameters of the high-pressure side of the centrifugal refrigerating unit reach set conditions.
In one embodiment, the high side parameter comprises a high side temperature and a high side pressure, and the set condition is that neither the high side temperature nor the high side pressure is lower than a respective set value.
Compared with the prior art, the utility model has the following beneficial effects:
1. the supercooling pressure in the refrigeration loop is recycled through the energy recovery device, and the expansion cooling is sent to the flash tank for air supplement and cooling, so that the secondary air supplement enthalpy increase of the centrifugal compressor is realized, the problem of liquid entrainment in air supplement is avoided, and the reliability of the unit is improved;
2. the energy after recycling is utilized to pressurize the liquid refrigerant to provide flowing power, the liquid refrigerant is conveyed to heating devices such as a motor and a controller through the cooling branch to be cooled, the pressure energy is recycled and converted into mechanical energy in the process, the power consumed by the cooling system is reduced, and therefore the energy-saving effect of the unit is achieved by utilizing the energy of the turbine to recycle.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.
The principles of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.
As shown in fig. 2, the centrifugal refrigeration unit according to the present invention forms a refrigeration circuit in which a refrigerant circulates through a condenser 2, a throttling device, a flash tank 3, an evaporator 4, and a centrifugal compressor 1, and an air make-up branch 5 is provided between the flash tank 3 and the centrifugal compressor 1. Wherein, throttling arrangement includes: the first throttling element 6 is connected in series between the outlet of the condenser 2 and the liquid inlet of the flash evaporator 3, the second throttling element 7 is connected in series between the liquid outlet of the flash evaporator 3 and the inlet of the evaporator 4, the refrigerant flowing out of the condenser 2 is decompressed into low-pressure low-temperature refrigerant by the first throttling element 6, the supercooling degree of the liquid refrigerant flowing out of the flash evaporator 3 is improved by the second throttling element 7, and the first throttling element 6 and the second throttling element 7 can adopt electronic expansion valves.
The refrigeration loop is connected with an energy recovery device 8, when the high-temperature gaseous refrigerant in the refrigeration loop drives the energy recovery device 8 to work, the high-temperature gaseous refrigerant does work due to expansion, the internal energy is reduced, the temperature and the pressure are both reduced, the energy recovery device 8 sends the expanded and cooled intermediate-temperature gaseous refrigerant back to the flash tank 3, the gaseous refrigerant in the flash tank 3 mainly comprises two parts, one part is the low-temperature and low-pressure gaseous refrigerant generated by the first throttling element 6, the other part is the intermediate-temperature and medium-pressure gaseous refrigerant generated by the energy recovery device 8, the two parts of gas supplement the centrifugal compressor 1 after being mixed in the flash tank 3, the intermediate-temperature gaseous refrigerant and the low-temperature gaseous refrigerant are mixed in the flash tank 3, liquid components in the low-temperature gaseous refrigerant absorb heat and are vaporized, and the problem that gas supplement and liquid carry are generated by a pure throttling device in the prior art is avoided.
In the working process of the unit, the power consumed by the compressor is mainly used for increasing the pressure, but because heat is inevitably generated when work is done, a low-temperature liquid refrigerant is required to be used for cooling. The heating device in the centrifugal refrigerating unit is generally cooled by adopting a cooling branch 9, an outlet of the cooling branch 9 is connected to the evaporator 4, the energy recovery device 8 absorbs the liquid refrigerant in the refrigerating circuit when working, pressurizes the liquid refrigerant and then sends the pressurized liquid refrigerant to the cooling branch 9, and in the process, because the centrifugal compressor 1 does not work on the refrigerant of the cooling branch 9, the consumption of the centrifugal compressor 1 on electric energy is reduced, the energy efficiency level of the refrigerating unit is improved, and the energy conservation of the unit is realized.
As shown in fig. 3, the energy recovery device 8 includes: the refrigerating device comprises a machine shell, a rotating shaft 81 arranged in the machine shell, a bearing 82 for supporting the rotating shaft 81 and an expansion wheel 83 fixed at one end of the rotating shaft 81, wherein the machine shell is provided with an expansion chamber 84 for accommodating the expansion wheel 83, the expansion chamber 84 is provided with an air inlet 841 and an air outlet 842, the air inlet 841 of the expansion chamber 84 is connected to the high-pressure side of a refrigerating circuit, the air outlet 842 of the expansion chamber 84 is connected to an liquid inlet of the flash evaporator 3, gaseous refrigerant enters the expansion chamber 84 from the air inlet 841 to drive the expansion wheel 83 to rotate, and the gaseous refrigerant which is changed into medium-temperature and medium-pressure after working on the expansion wheel 83 is sent back to the flash evaporator 3.
Since the inlet of the condenser 2 is connected with the exhaust port of the centrifugal compressor 1, after the unit normally operates, the temperature and pressure of the high-pressure side are increased, high-temperature and high-pressure gaseous refrigerant exists at the top of the heat exchange tube of the condenser 2, and the air inlet 841 of the expansion chamber 84 is connected to the top of the heat exchange tube of the condenser 2, so that the design has the advantage that the excessive pressure of the condenser 2 can be recycled without affecting the normal operation of a refrigeration loop.
In some embodiments, the energy recovery device 8 is a turbo-supercharged energy recovery device, the other end of the rotating shaft 81 is fixed with a compression wheel 85, the compression wheel 85 and the expansion wheel 83 are coaxially arranged, the compression wheel 85 and the expansion wheel 83 are both turbines, the casing is provided with a compression chamber 86 for accommodating the compression wheel 85, the expansion chamber 84 and the compression chamber 86 are separately arranged, the compression chamber 86 is provided with an inlet 861 and an outlet 862, the inlet 861 of the compression chamber 86 is connected to the low-pressure side of the refrigeration circuit, and the outlet 862 of the compression chamber 86 is connected to the cooling branch 9. When the gas refrigerant drives the expansion wheel 83 to rotate and work, the expansion chamber 84 sends the expanded and cooled gas refrigerant back to the flash tank 3, meanwhile, the compression chamber 86 absorbs the liquid refrigerant in the refrigeration loop, the compression wheel 85 rotates to pressurize the liquid refrigerant, and the liquid refrigerant is conveyed to the cooling branch 9 to cool the controller 10 and the heating devices such as the motor of the compressor.
Since the outlet of the evaporator 4 is connected with the air suction port of the centrifugal compressor 1, after the unit normally operates, the liquid refrigerant exists at the bottom of the heat exchange tube of the evaporator 4, and the liquid inlet 861 of the compression chamber 86 is connected to the bottom of the heat exchange tube of the evaporator 4, the design has the advantage that the liquid refrigerant of the evaporator 4 can be utilized to prevent the air suction and liquid entrainment of the centrifugal compressor 1.
It should be noted that, the expansion wheel 83 is driven by the high-temperature high-pressure gaseous refrigerant, the expansion wheel 83 drives the rotating shaft 81 to rotate, and the pressure energy is converted into the mechanical energy, so that there are various ways to realize energy recovery, which are not limited to the above-mentioned ways, for example, a power generation structure may be designed to convert the mechanical energy generated by the rotation of the rotating shaft 81 into electrical energy. The bearing 82 used in the energy recovery device 8 may be a static pressure gas bearing or a dynamic pressure gas bearing, and for the present invention, a dynamic pressure gas bearing is preferable since the rotation speed of the rotating shaft 82 is as high as several tens of thousands of rotations.
In the preferred embodiment, the bottom of the heat exchange tube of the condenser 2 is provided with a cooling outlet, the cooling outlet is connected to the cooling branch 9 through a control valve, and the control valve is closed when the parameters of the high pressure side of the centrifugal refrigerating unit reach set conditions.
For convenience of understanding, the centrifugal compressor is exemplified by a two-stage centrifugal compressor, and the high-pressure-side parameter includes a high-pressure-side temperature and a high-pressure-side pressure, and the setting condition is that neither the high-pressure-side temperature nor the high-pressure-side pressure is lower than the respective set values. When the centrifugal compressor 1 is just started, the high-pressure side temperature and the high-pressure side pressure are low, so that the operation of the energy recovery device cannot be met, the control valve is kept in an open state, the cooling of the heat generating device is mainly performed by the pressure difference of the system, and the liquid refrigerant is taken from the bottom of the condenser 2 for cooling. When the high-pressure side temperature and the high-pressure side pressure rise to be not lower than the respective set values, the control valve is closed, and the high-pressure low-temperature liquid refrigerant is supplied through the energy recovery device 8 for cooling. When the refrigerating unit is in a normal operation process, the centrifugal compressor 1 absorbs low-temperature low-pressure gaseous refrigerant from the evaporator 5 and then passes through the primary compressor to reach intermediate pressure, at the moment, the gas of the centrifugal compressor 1 belongs to an overheat state, then the gas of the flash evaporator 3 is cooled, and then secondary compression is carried out to reach set pressure, and the energy efficiency level of the refrigerating equipment is indirectly improved due to the fact that the power consumed by the secondary compression is reduced through intermediate cooling.
The utility model can realize the pressure energy recovery of the unit, reduce the power consumption of the compressor, increase the air supplement amount of the flash tank, avoid the air supplement liquid carrying problem generated in the pure throttling process and improve the operation reliability of the unit.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.