Patent Publication Number: US-11022349-B2

Title: Hydronic system for combining free cooling and mechanical cooling

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a US National Stage application of PCT/IB2015/001370, filed Jul. 22, 2015, which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to refrigeration systems, and more particularly, the present disclosure relates to methods and systems for operating a refrigeration system in a free-cooling mode and a mechanical cooling mode. 
     Conventional refrigeration systems operate by circulating a fluid, such as refrigerant, through a closed thermodynamic loop. During the cycle, heat is absorbed from a medium on the evaporator side and rejected to a medium on the condenser side. During these heat transfer processes at pressure conditions defined by the temperature levels of the source and sink temperatures, the refrigerant undergoes phase changes occurring during heat transfer processes. This cyclic transformation occurs due to mechanical compression or work provided to the refrigerant by a compressor and a pressure expansion device and is referred to as a “mechanical cooling mode”. Typically in the evaporator, the refrigerant enters a heat exchanger and cools a medium such as water, air, or glycol, which in turn may be used to cool a conditioned space. Applications of refrigeration systems include cooling of commercial and residential buildings, data centers, industrial equipment, agriculture and food. 
     However, when the temperature of the ambient outside air is low, the outside air may be used to cool the medium without engaging the compressor. In such instances, the refrigeration system includes several additional components connected to the refrigeration system through one or more hydraulic loops. When cool ambient air is used by the refrigeration system in place of the compressor, the system is referred to as operating in a “free-cooling mode.” In the free-cooling mode, one or more ventilated heat exchangers and pumps are activated and the cooling medium circulating throughout the refrigeration system is cooled indirectly by outside ambient air without the need for a compressor. Because running the refrigeration system in a free-cooling mode requires less work input, running the system in free-cooling mode is more efficient than run g the system in mechanical cooling mode. 
     Traditionally, refrigeration systems have been run in a mechanical cooling mode even when the ambient outside air temperature is low. In contrast, running the refrigeration system under such conditions in a free-cooling mode is more efficient. Accordingly, there is a need for a system configured to operate in one of both a mechanical cooling mode and a free-cooling mode. 
     SUMMARY 
     According to an embodiment of the present disclosure, a refrigeration system is provided including a refrigeration circuit and a free cooling system. The free cooling system includes a fluid cooling circuit and a free cooling circuit. The fluid cooling circuit is thermally and hydraulically coupled to the refrigeration circuit such that that a cooling fluid of the fluid cooling circuit is configured to transfer heat to the refrigerant. The free cooling circuit is thermally and hydraulically coupled to the refrigeration circuit such that a free cooling fluid of the free cooling circuit is configured to absorb heat from the refrigerant. The free cooling circuit and the fluid cooling circuit are thermally and hydraulically coupled through a free cooling heat exchanger. At least one valve is configured to control a flow within the free cooling circuit. The refrigeration system is operable in a free cooling mode, a mechanical cooling mode, and a combined free cooling and mechanical cooling mode. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the free cooling circuit includes a heat exchanger configured to reject heat from the free cooling fluid to ambient air. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the free cooling circuit is thermally and hydraulically coupled to the condenser and the fluid cooling circuit is thermally and hydraulically coupled to the evaporator. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the free cooling heat exchanger is located upstream of the condenser with respect to a flow of the free cooling fluid through the free cooling circuit. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the free cooling heat exchanger and the condenser are arranged in parallel with respect to a flow of the free cooling fluid through the free cooling circuit. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one valve is positioned upstream from the free cooling heat exchanger. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one valve includes a valve positioned upstream from the condenser. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one valve is positioned downstream from the free cooling heat exchanger. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the free cooling heat exchanger is located upstream of the evaporator with respect to a flow of the cooling fluid through the fluid cooling circuit. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the free cooling circuit includes a pump configured to move the free cooling fluid through the free cooling circuit. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the fluid cooling circuit includes a pump configured to move the cooling fluid through the fluid cooling circuit. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one valve is selected from a three-way valve and a two-way valve. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments a controller is configured to control operation of the refrigeration system in one of the free cooling mode, mechanical cooling mode, and a combined free cooling and mechanical cooling mode based on a cooling load and an outside temperature. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the controller is operably coupled to the compressor, a pump, and the at least one valve. The controller is configured to operate one or more of the compressor, the pump, and at least one valve when switching between the free cooling mode, mechanical cooling mode, and a combine free cooling and mechanical cooling mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the present disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic diagram of a refrigeration system according to an embodiment of the present disclosure; and 
         FIG. 2  is a schematic diagram of another refrigeration system according to another embodiment of the present disclosure. 
     
    
    
     The detailed description explains embodiments of the present disclosure, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION 
     Referring now to the  FIGS. 1-2 , various refrigeration systems, generally referred to by reference numeral  20 , are illustrated. System  20  is configured to simultaneously perform both mechanical cooling and free cooling. The system  20  includes a refrigerant circuit  22  having a compressor  24 , condenser  26 , an expansion device  28 , and an evaporator  30 . The compressor  24  compresses a refrigerant and delivers it downstream into a condenser  26 . From the condenser  24 , the refrigerant passes through the expansion device  28  and then to the evaporator  30 . From the evaporator  30 , the refrigerant is returned to the compressor  24  to complete the closed-loop refrigerant circuit. A basic refrigeration circuit is illustrated and described herein. However, systems  20  having a more complex refrigeration circuit  22  are within the scope of the present disclosure. In addition, the refrigeration system  20  may include any number of refrigeration circuits  20  depending on the cooling requirements of a given application. 
     Each of the illustrated refrigeration systems  20  additionally includes a free cooling system  40  operably connected to the refrigeration circuit  22 . The refrigeration circuit  22  and the free cooling system  40  may be packaged together and may be located at any location, for example indoors, in any technical room of a facility to be conditioned, on a roof or in a basement. In this configuration, the refrigeration system  20  is modular and easy to connect to a new or existing fluid network, such that the system  20  may be used in retrofit applications. 
     The free-cooling system  40  includes a first circuit or free cooling circuit  42 , having a first fluid or free cooling fluid W 1 , such as ethylene/propylene glycol, brine or any other anti-freeze solution for example, flowing there through and a second circuit or cooling fluid circuit  50  having a second fluid W 2 , such as water, ethylene/propylene glycol, brine or any other solution for example, flowing there through. The free cooling first circuit  42  includes a dry or adiabatic cooler  44  configured to take advantage of the heat-removing capability of cool, ambient air, by arranging the air in a heat exchange relationship with the fluid W 1  via a heat exchanger, such as a round tube heat exchanger for example, and one or more fixed speed or variable speed fans. As shown, the free-cooling circuit  42  and the refrigeration circuit  22  are thermally and hydraulically coupled together at the condenser  26  such that heat rejected from the refrigerant in the condenser is transferred to the free-cooling fluid W 1  of the free cooling circuit  42 . The condenser  26  is arranged generally downstream of the dry cooler  44 . 
     The fluid W 1  is driven through the first circuit  42  by a pump  46  such that the fluid W 1  flows sequentially through the condenser  26  and the dry or adiabatic cooler  44 . The pump  46  may be located at any positioned within the free-cooling circuit  42 , such as adjacent an inlet or outlet of the dry or adiabatic cooler  44 . The pump  46  may be configured as a fixed speed pump or as a variable speed pump operable to control a constant pressure differential or temperature differential or any other control modes. The second circuit  50  is configured to supply a fluid W 2  to an environment to be conditioned and receive cooling fluid W 2  from the environment to be conditioned. In one embodiment, the second circuit  50  may include a storage tank configured to store a portion of cooling fluid W 2 . The second circuit or cooling fluid circuit  50  and the refrigeration circuit  22  are hydraulically and thermally coupled together so as to allow the cooling fluid or second fluid W 2  to be cooled in the evaporator  30 . Similarly, the second circuit or cooling fluid circuit  50  and the first circuit, the free cooling circuit  42 , are thermally and hydraulically coupled together at the free cooling heat exchanger  48 . When arranged in a heat exchange relationship in the free cooling heat exchanger  48 , the second fluid W 2  is configured to reject heat to the first fluid W 1 . 
     A pump  52  is configured to drive the cooling fluid W 2  through the second circuit  50 . The pump  52  may be configured as a fixed speed pump or as a variable speed pump operable to control a constant pressure differential or temperature differential or any other control modes. In the illustrated non-limiting embodiment, the fluid W 2  is provided first to the free-cooling heat exchanger  48  and then to the downstream evaporator  30 . By positioning the free-cooling heat exchanger  48  upstream from the evaporator  30 , the cooling fluid W 2  is cooled prior to entering the evaporator  30 . Based on the required cooling load of the refrigeration system  20 , the cooling fluid W 2  is cooled to a required temperature setpoint by activating the refrigeration system  20 . 
     As previously stated, the refrigeration systems  20  disclosed herein are configured to perform combined mechanical cooling and free cooling. Referring now to  FIG. 1 , the free cooling heat exchanger  48  is positioned between the dry or adiabatic cooler  44  outlet and the condenser  26 . More specifically, in the illustrated, non-limiting embodiment, the free cooling heat exchanger  48  and the condenser  26  are arranged in series such that all of the fluid W 1  provided at an outlet of the free cooling heat exchanger  48  also passes through the condenser  26 . 
     A valve  49  is configured to control the flow of fluid W 1  through the free cooling heat exchanger  48 . Although the valve is illustrated as a three-way valve, any type of valve is contemplated. For example, when the valve  49  is in a first position, all or at least a portion of fluid W 1  is configured to flow through the free cooling heat exchanger  48  and the condenser  26  sequentially. However, when the valve  49  is in a second position, the fluid flow may be configured to bypass the free cooling heat exchanger  48  such that the fluid W 1  only passes through the condenser  26 . The valve  49  may be arranged at various locations in the first circuit  42 , such as upstream from the free cooling heat exchanger  48 . When the system  20  of  FIG. 1 , is operated in a mechanical-cooling mode, the flow of fluid W 1  is configured to bypass the heat exchanger  48 . In a free-cooling mode, however, at least a portion of the fluid W 1  is configured to flow through the free cooling heat exchanger  48 . 
     In another embodiment, illustrated in  FIG. 2 , the free cooling heat exchanger  48  is similarly provided downstream from the dry or adiabatic cooler  44  outlet. However, unlike the configuration of  FIG. 1 , the free cooling heat exchanger  48  is arranged in parallel with the condenser  26  such that fluid flow is distributed between free cooling heat exchanger  48  and condenser  26  within the first circuit  42 . A first valve  49  arranged upstream from an inlet to the condenser  26  is configured to control a flow of the fluid W 1  through the condenser. Similarly, a second valve  51  arranged upstream from an inlet of the free cooling heat exchanger  48  is configured to control a flow of the fluid W 1  through the free cooling heat exchanger  48 . The valves can be of two-way valve or three-way configuration. Together, valves  49  and  51  may be manipulated between a plurality of positions to operate the air refrigeration system in a free cooling mode, a mechanical cooling mode, and a combined free cooling and mechanical cooling mode. When the refrigeration system  20  of  FIG. 2  is operated in a free-cooling mode, the fluid W 1  is configured to bypass the condenser  26 . 
     A controller  60  is configured to control operation of the refrigeration system  20 . More specifically, the controller  60  is operably coupled to the compressor  24 , pumps  46 ,  52 , dry or adiabatic cooler fans  44 , and the valves  49 ,  51  to control the cooling capacity of the system. In one embodiment, the controller  60  is configured to adjust operation of the refrigeration system  20  based not only the cooling demand on the system, but also on the temperature of the external ambient air. 
     The refrigeration system  20  described herein has a simplified and improved design compared to conventional systems, resulting in a reduced footprint. More specifically, these refrigeration systems  20  may be contained within a single package, rather than multiple packages. Because the refrigeration system  20  may be operated in a plurality of modes, the overall capability of the system is increased. For example, the system  20  may be operated in a free cooling only mode when the system has a low to moderate cooling requirement and may be operated in a combined free cooling and mechanical cooling mode for greater loads. This adaptability results in improved system efficiency which lowers the overall energy required for operation. 
     While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.