Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B29/00—Combined heating and refrigeration systems, e.g. operating alternately or simultaneously
  • F25B29/006—Combined heating and refrigeration systems, e.g. operating alternately or simultaneously of the sorption type system
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B41/00—Fluid-circulation arrangements
  • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B41/00—Fluid-circulation arrangements
  • F25B41/40—Fluid line arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B49/00—Arrangement or mounting of control or safety devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
  • F25B2400/04—Refrigeration circuit bypassing means

Definitions

• the present disclosure relates to an absorption chiller system. More particularly, the present disclosure relates to a method and system for rejecting heat from a hot water source in an absorption chiller capable of simultaneous heating and cooling.
• a simultaneous heating and cooling absorption chiller may be configured for providing heating and cooling to a building using, respectively, a hot water source and a chilled water source.
• the absorption chiller may include a heat exchanger configured for receiving the hot water and thereby increasing a temperature of the hot water.
• the building may have heating and cooling demands that vary frequently. There may be periods of time when the building is not requiring any heating; thus, the absorption chiller does not have a heating demand during that time.
• Tn those cases, if there is a cooling demand, the absorption chiller is still operating, and a pump that delivers the hot water to the heat exchanger may continue to circulate the hot water through the heat exchanger. Due in part to friction heat inside piping of the heat exchanger and energy from the pump, a temperature of the hot water may increase. If the building does not have a heating load to consume the energy from the hot water, the hot water may rise to an undesirable temperature.
• the present disclosure relates to a method and system for rejecting heat from a hot water source capable of being used for heating in a simultaneous heating and cooling absorption chiller having an absorber, a generator, a heat exchanger, a condenser, an evaporator, and a cooling water loop passing through the absorber and the condenser.
• the system includes a bypass loop configured in parallel with the heat exchanger and connected to an inlet and an outlet of the heat exchanger.
• the bypass loop is configured to receive at least a portion of hot water flowing to the heat exchanger, and includes a radiator positioned inside a portion of the cooling water loop. Hot water directed into the bypass loop flows through the radiator so that heat from the hot water is transferred to cooling water in the cooling water loop.
• the system further includes a valve for controlling a flow of hot water through the bypass loop.
• FIG. 1 is a schematic diagram of an exemplary embodiment of a simultaneous heating and cooling absorption chiller, which includes a heat exchanger and a bypass loop configured for rejecting heat from a hot water source being delivered to the heat exchanger.
• FIG. 2 is a schematic diagram of the heat exchanger of FIG. 1 and a portion of the bypass loop.
• FIG. 3 is another schematic diagram of the heat exchanger and the bypass loop of FIGS. 1 and 2, as well as a valve configured for regulating flow through the bypass loop.
• FIG. 4 is a schematic diagram of a portion of the chiller of FIG.
• FIG. 5 is a schematic diagram of a control system for controlling operation of the absorption chiller of FIG. 1.
• FIG. 1 is a schematic diagram of absorption chiller system 10, which includes evaporator 12, absorber 14, high stage generator 16, low stage generator 18, condenser 20, high temperature solution heat exchanger 22, low temperature solution heat exchanger 24, and auxiliary heat exchanger 26.
• chiller system 10 is a double-effect absorption chiller with simultaneous heating and cooling capabilities, and as such, system 10 may be used to supply heating and cooling to a building. It is recognized that the method and system described herein for rejecting heat in chiller system 10 may also apply to any type of absorption chiller having simultaneous heating and cooling capabilities, including, but not limited to, a single-effect or a triple-effect absorption chiller.
• Chiller system 10 is configured to provide cooling to a building by decreasing a temperature of chilled water source 28, which passes through evaporator 12.
• System 10 is able to simultaneously provide heating to the building by increasing a temperature of hot water source 30, which passes through auxiliary heat exchanger 26.
• system 10 also includes cooling water loop 32 for flowing water from a cooling tower through absorber 14 and condenser 20 such that the cooling water is used for heat removal.
• absorption chiller systems like system 10, are configured to use an absorbent solution, such as lithium bromide, and a refrigerant, such as water, to provide a cooling and/or a heating effect.
• an absorbent solution such as lithium bromide
• a refrigerant such as water
• chiller system 10 is described using lithium bromide and water, it is recognized that other combinations (for example, water as the absorbent and ammonia as the refrigerant) may alternatively be used in system 10.
• Evaporator 12 is configured to receive refrigerant in liquid form (i.e. water) from condenser 20 and store the water in evaporator sump 34.
• evaporator 12 pumps water from sump 34 to sprayer 38, located at a top of evaporator 12, or to a dripper system in evaporator 12.
• system 10 is a closed loop system and maintained in a vacuum such that water from sprayer 38 boils at a lower temperature.
• the refrigerant (water), now in vaporized form, travels to absorber 14 through eliminator 40, at which point the water is absorbed by a concentrated lithium bromide solution being sprayed through sprayer 42 at a top of absorber 14.
• a diluted lithium bromide solution then is delivered to high stage generator 16 using solution pump 44.
• Exhaust gas is supplied to high stage generator 16 to boil water from the lithium bromide solution, thus generating steam.
• exhaust gas is supplied from a rnicroturbine or another type of prime mover.
• a benefit of system 10 is that it utilizes waste heat from another component used in the building. It is recognized that other types of heat sources may be used for supplying heat energy to generator 16.
• generator 16 may be direct-fired, steam fired or hot-water driven. Steam generated by generator 16 may then be directed to low stage generator 18 and to auxiliary heat exchanger 26. Moreover, steam from generator i 16 may also reside in overflow piping 46.
• Lithium bromide solution from high stage generator 16 flows through heat exchanger 22 and then flows to a shell side of low stage generator 18.
• the lithium bromide solution in generator 18 then boils off additional steam due to transferred heat from the steam on the tube side of generator 18.
• the additional steam on the shell side of generator 18 then travels to condenser 20 through eliminator 48 located between generator 18 and condenser 20.
• cooling water 32 flows through a tube side of condenser 20.
• the steam from generator ⁇ 8 enters the shell side of condenser 20 the steam condenses and the condensate is recycled back to evaporator 12.
• system 10 in the exemplary embodiment of FIG. 1, is a simultaneous heating and cooling absorption chiller, system 10 also includes auxiliary heat exchanger 26, which may be used for heating.
• chiller system 10 includes overflow piping 46 connected between high stage generator 16 and absorber 14. Overflow piping 46, used in conjunction with steam trap 50, may be used to recycle excess absorbent solution in generator 16, which may accumulate under certain operating conditions, back to absorber 14. As also shown in FIG.
• system 10 includes liquid level sensors 52 for monitoring a level of refrigerant in evaporator sump 34 to control operation of refrigerant pump 36. It is recognized that overflow piping 46, steam trap 50 and sensors 52 are not required in chiller system 10, but may be used for improving operation of system 10, particularly under a low cooling or heating load.
• system 10 includes three main valves that are used to control operation of system 10 - diverter valve 70 (also referred to as CVl), heat exchanger control valve 72 (also referred to as CV2), and low stage generator control valve (also referred to as CV3).
• Valve 70 (CVl) is configured to regulate an amount of exhaust gas supplied to high stage generator 16 based on the heating and/or cooling demands on system 10.
• Valve 72 is configured to regulate an amount of liquid condensate in heat exchanger 26 recycled back to generator 16, as a function of the heating demand.
• Valve 74 is configured to regulate an amount of liquid condensate in low stage generator 18 recycled back to evaporator 12, based on the heating and/or cooling demands and the conditions inside high stage generator 16.
• System 10 also includes bypass loop SO, configured in parallel with heat exchanger 26, and valve 82, both of which are described in further detail below. It is recognized that additional valves not specifically shown in FIG. 1 or described herein are included in system 10.
• FIG. 2 is a schematic diagram of heat exchanger 26 from FIG. 1.
• Heat exchanger 26 is used to increase a temperature of hot water 30 passing through heat exchanger 26 via heat exchanger inlet 84 and heat exchanger outlet 90.
• heat exchanger 26 may be a shell and tube type heat exchanger, in which case hot water 30a entering through inlet 84 is directed through multiple tubes 86 inside heat exchanger 26.
• Steam from generator 16 enters a shell side of heat exchanger 26 through piping 88. As such, heat from the steam is transferred to hot water 30 and the steam condenses on the outside of tubes 86 to form a liquid condensate.
• Valve 72 is configured to regulate an amount of heat transferable to hot water 30. If CV2 is open, the liquid condensate (which was steam from generator 16) is directed to flow out of heat exchanger 26 and back to generator 16 through piping 92. Conversely, if CV2 is closed, the liquid condensate builds up inside heat exchanger 26. A heating capacity of heat exchanger 26 is a function of an amount of condensate inside heat exchanger 26.
• the heating capacity of heat exchanger 26 is a function, in part, of the po sition or state of C V2.
• CV2 controls the outlet temperature T HE OUT of hot water 30b by controlling an amount of condensate inside heat exchanger 26, based on a set point temperature T SET PT for hot water 30. For example, during a heating demand, the set point temperature T SET PT may be equal to 175°F.
• CV2 is positioned and adjusted as necessary so that T HE O UT remains essentially equal to 175°F. Because system 10 is a simultaneous heating and cooling absorption chiller, system 10 may be operating in some cases when there is a cooling demand, but no heating demand. (This includes those scenarios in which the heating and cooling demands on system 10 are frequently fluctuating.) Under those conditions, hot water 30 may continue to be pumped through heat exchanger 26, even though the building is not requesting any heating. [0023] The set point temperature T SET PT for the hot water outlet is adjusted to reflect changes in the heating demand. When there is no heating demand, controller 112 of system 10 (described below in reference to FIG.
• Bypass loop 80 may be used to reject (i.e. transfer) heat from hot water 30 when outlet temperature T HE OUT rises above a predetermined level.
• Bypass loop 80 includes first flow passage 96, second flow passage 98 and heat rejection radiator 100 (see FIG. 4). As shown in FIGS. 1 and 2, bypass loop 80 is configured in parallel with heat exchanger 26 and is configured to receive a portion of hot water 30a entering inlet 84 of heat exchanger 26. As shown in FIG. 2, first flow passage 96 is connected to inlet 84 of heat exchanger 26 and second flow passage 98 is connected to outlet 90. (This is further described in FIGS. 3 and 4.) [0025] FIG. 3 is a schematic diagram of heat exchanger 26, a portion of bypass loop
• First flow passage 96 delivers hot water 30 from heat exchanger inlet 84 to heat rejection radiator 100 (see FIG. 4); second flow passage 98 delivers hot water 30 from heat rejection radiator 100 to heat exchanger outlet 90.
• first flow passage 96 includes two sections of piping - first piping section 96a and second piping section 96b. Second flow passage 98 is similarly formed from at least one section of piping.
• Valve 82 is located between first and second sections of piping 96a and 96b, and is configured to regulate a flow of hot water 30 through bypass loop 80.
• valve 82 is a solenoid valve. It is recognized that other types of flow valves or similar flow regulating devices may be used. -As described above, passage 96 is configured to receive a portion of hot water 30 passing through inlet 84. When solenoid valve 82 is actuated, water 30 is permitted to flow through valve 82 to radiator 100. When valve 82 is closed, all of hot water 30 flows through tubes 86 of heat exchanger 26. [0027] FIG.
• cooling water loop 32 is configured to circulate water from a cooling tower through absorber 14 and condenser 20.
• Cooling water loop 32 includes cross-over piping 32a between absorber 14 and condenser 20.
• bypass loop 80 includes first flow passage 96 (specifically second section 96b), second flow passage 98, and heat rejection radiator 100 located between passages 96 and 98.
• Heat rejection radiator 100 is designed to be located inside cross-over piping
• Hot water 30 from heat exchanger inlet 84 passes from first fluid passage 96 through heat rejection radiator 100, and then to heat exchanger outlet 90 through second fluid passage 98.
• cooling water is circulating through cross-over piping 32a.
• heat is transferred from hot water 30 to cooling water in cross-over piping 32a.
• a temperature of hot water 30 at outlet 104 of radiator 100 is less than a temperature of hot water 30 at inlet 102.
• heat rejection radiator 100 is a piece of
• U-shaped piping wherein a diameter of the piping is significantly less than a diameter of cross-over piping 32a.
• a benefit of the embodiment of FIG. 4 is that a standard piece of piping may be bent to form the U-shape or hairpin shape, hi other embodiments, the piping may be bent in various ways so long as the piping is configured to be located inside crossover piping 32a.
• chiller system 10 uses an existing cooling source (i.e. cooling water loop 32) for heat rejection under those conditions in which the hot water outlet temperature T HE OUT rises above a predetermined level. Moreover, because heat rejection radiator 100 is contained within cross-over piping 32a, bypass loop 80 does not increase a footprint of chiller system 10. [0031] In preferred embodiments, radiator 100 is configured to maximize a length L of radiator 100 inside cross-over piping 32a in order to maximize an amount of heat transferred from radiator 100 to cooling water inside cross-over piping 32a.
• radiator 100 may reside only in cross-over piping 32a; in alternative embodiments, a portion of radiator 100 may extend into a water box of absorber 14 and/or condenser 20.
• FIG. 5 is a schematic diagram of control system 110 for controlling operation of chiller system 10, including bypass loop 80.
• System 110 includes controller 112, inputs 114 to controller 112 and outputs 116. It is recognized that control system 110 includes additional inputs and outputs that are not included in FIG. 5 for clarity.
• Inputs 114 include cooling demand 118, heating demand 120, T HE OUT, THE SET
• chiller system 10 may have a cooling demand and a heating demand at the same time. At other times, system 10 may be operating under either a cooling demand or a heating demand. Moreover, system 10 may experience frequent fluctuations in the cooling and/or the heating demand.
• controller 112 Based on cooling demand 118 and heating demand 120, controller 112 controls a position of valve 70 (CVl), which supplies heat (i.e. waste gas) to generator 16. So long as the total demand (heating plus cooling) does not exceed a maximum value, controller 112 may not be required to designate a heating priority or a cooling priority.
• CVl valve 70
• controller 12 may operate as a function, at least in part, of whether system 10 has a heating priority or a cooling priority. In either case, when the total demand is at or above a maximum value, control valve 70 (CVl) is fully open and controller 112 adjusts valves 72 and 74 to provide the required heating and/or cooling. f0034] Because valve 72 (CV2) is configured to regulate a flow of condensate exiting heat exchanger 26, valve 72 controls an ability of heat exchanger 26 to transfer heat to hot water 30 passing through heat exchanger 26. A position of valve 72 (CV2) is controlled, in part, as a function of the temperature T HE OUT of hot water 30b at outlet 90.
• Temperature T HE OUT is compared to a set point temperature TH E SE T P T for the hot water, which may be, for example, commonly set at 175°F.
• T HE O U T and T HE SET PT are both inputs to controller 112.
• bypass loop 80 is configured to redirect at least a portion of hot water 30 from heat exchanger 26 to heat rejection radiator 100 if the temperature T HE OUT of hot water 30 at outlet 90 of heat exchanger 26 is too high.
• controller 112 adjusts CV2 to control temperature T HE OUT* based on the set point temperature T HE SET PT - Therefore, heat rejection radiator 100 is usually not used until temperature THE O U T is above a predetermined value that is greater than the set point temperature T H ⁇ SET PT - Valve 82 controls a flow of hot water 30 to radiator 100, and is controlled by controller 112.
• controller 112 opens valve 82 so that water 30 is able to flow through radiator 100.
• the predetermined value is equal to a sum of the set point temperature TSET P T and a marginal value. For example, if THE SE T PT is equal to 175°F and the marginal value is equal to ten degrees, controller 112 opens valve 82 ifT HE ⁇ u ⁇ is greater than 185°F. Valve 82 may then be closed when T H E OUT decreases to a temperature that is less than or equal to the predetermined value.
• Control system 110 includes at least one temperature sensor located around outlet 90 of heat exchanger 26 for measuring THE O UT-
• inputs 114 also include T G2 OU T , which is a temperature of liquid condensate exiting a tube side of generator 18, and TAB S O UT, which is a temperature of absorbent solution (i.e. lithium bromide) exiting absorber 14.
• T C K O UT and TABS OU T may be monitored, along with THE OU T, by controller 1 12 to determine a position of valve 74 (CV3).
• valve 72 (CV2) is used to control the outlet temperature T H E OUT of hot water 30, and consequently control an amount of heating provided by heat exchanger 26.
• valve 72 (CV2) is fully open (i.e.
• the outlet temperature T H E OU T of hot water 30 may be less than the set point temperature THE SET P T. In that case, adjustments may be made to valve 74 (CV3), based on T G2 OUT, TAB S O UT, and THE OUT, to increase the outlet temperature THE OUT and bring it closer to TH E SE T PT- AS also shown in FIG.
• inputs 114 may also include a set point temperature for liquid condensate exiting low stage generator 18 (referred to as TQ 2 S E T PT ) 3 which may be a function of TAB S O U T and THE OU T -
• TQ 2 S E T PT set point temperature for liquid condensate exiting low stage generator 18
• controller 1 12 compares T G2 OUT to T G2 S ET PT to determine how to adjust valve 74.
• Control system 110 includes at least one temperature sensor at an outlet of absorber 14 for measuring the temperature of the absorbent solution T ABS OUT , and at least one sensor at an outlet of generator 18 for measuring the temperature of the steam condensate, TG 2 OUT-
• bypass loop 80 which includes radiator 100, may be used in chiller system 10 to reject or transfer heat from hot water 30 when the building does not have a heating demand and an outlet temperature of hot water 30 becomes undesirably high.
• Bypass loop 80 is designed such that existing piping 32a of cooling water loop 32 in system 10 may be used for rejecting heat from hot water 30 to cooling water passing through piping 32a. As such, bypass loop 80 does not increase a footprint of absorption chiller system 10. Moreover, by utilizing an existing cooling water loop, bypass loop 80 does not require an additional heat exchanger dedicated to removing heat from hot water 30.
• heat rejection radiator 100 is a single piece of piping having a U-shape, and located in cross-over piping 32a. It is recognized that additional designs for radiator 100 may be used in system 10. For example, in alternative embodiments, heat rejection radiator 100 may be located inside the piping of cooling water loop 32 at a different location within system 10. Bypass loop 80 may be added to existing chiller systems or it maybe included in the design of new chillers. [00391 Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Sorption Type Refrigeration Machines (AREA)
• Other Air-Conditioning Systems (AREA)

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• 2007
  • 2007-04-13 KR KR1020097022654A patent/KR101120251B1/ko not_active IP Right Cessation
  • 2007-04-13 CN CN2007800529526A patent/CN101688710B/zh not_active Expired - Fee Related
  • 2007-04-13 WO PCT/US2007/009033 patent/WO2008127228A1/en active Application Filing
  • 2007-04-13 EP EP07755340A patent/EP2156111A1/de not_active Withdrawn

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