Refrigeration – Intermediate fluid container transferring heat to heat... – Flow line connected transfer fluid supply and heat exchanger
Reexamination Certificate
2000-12-08
2001-12-18
Bennett, Henry (Department: 3744)
Refrigeration
Intermediate fluid container transferring heat to heat...
Flow line connected transfer fluid supply and heat exchanger
C062S079000, C062S237000
Reexamination Certificate
active
06330809
ABSTRACT:
This invention relates generally to the cooling of generators/motors and specifically, to the application of a chiller in series with a conventional coolant source to increase generator/motor capability.
BACKGROUND OF THE INVENTION
The capacity of the machinery to convert energy from mechanical to electrical or vice versa is directly related to the rate of which the excess heat can be removed. Currently, the gas which is used to cool electrical machinery, such as a motor or generator, whether hydrogen or air, is typically cooled by a heat exchanger in the system that transfers the heat to a fluid such as water or anti-freeze mixture. This coolant then rejects the heat to the atmosphere through a second heat exchanger. Therefore, the cooling capacity is limited by the temperature of the heat sink. In hot climate regions of the world, this severely reduces the cooling capacity and limits generator/motor capability.
Duplex series coolers are currently used on generators ranging from 25 MW to 1300 MW. Coolant supplied to these coolers comes from a common “ambient following source.” Assuming the two cooler sections are constructed with identical hardware (for example, tube and fin count), the first section removes about 75% of the heat load, and the second section removes the remaining 25%, i.e., the gas flows over the heat exchangers “in series.” Every effort has been made to reduce the approach temperature difference between the cold liquid temperature and ambient temperature, and between the generator cold gas and cold liquid temperature using extended tube and fin technology. This closes the gap between the generator cold gas and ambient air temperature, but the generator output is still limited by the temperature of the ambient following source.
Chillers have been applied to generators in the past, but not as described herein where the chiller technology is used to step cool the gas in a duplex series cooler arrangement.
BRIEF SUMMARY OF THE INVENTION
This invention seeks to provide a means for lowering the overall cost of producing power by cooling the generator/motor more efficiently. To obtain additional cooling capacity, chilled coolant is circulated through a second heat exchanger downstream of the ambient following or first exchanger. Arranging them in series (relative to the gas flow) greatly increases the cooling efficiency and reduces the required size of the chiller since only a portion of the heat is rejected to the chiller.
The (refrigeration) chiller unit also offers the ability to control the coolant temperature independent of the ambient temperature. The coolant temperature can be set to a constant (as low as 42° F.) which is ideal for constant load steam turbine generator applications, or the chiller can be programmed to deliver cold liquid as a function of the ambient temperature ideal for gas turbine ambient following machines. It will be understood, however, that the coolant temperature cannot be so low as to freeze the evaporator section of the chiller.
More specifically, this invention provides for the application of a reciprocating, centrifugal or absorption chiller to provide chilled water to a second heat exchanger downstream of a first or ambient water source exchanger so as to significantly improve generator/motor cooling while minimizing the cost associated with the chiller. This invention simply maximizes the temperature difference from hot gas to cold liquid in both exchanger sections to maximize heat transfer and generator cooling. Although power is required to run the chiller, the series arrangement minimizes the size of the chiller required, which lowers the power consumption to only a small fraction of the increase power output obtained by more effective cooling.
In accordance with one aspect of the invention, there is provided a generator/motor cooling apparatus comprising a cooler for cooling gas used to cool the generator/motor, the gas flowing serially across first and second heat exchangers that are supplied with water from an ambient source; and a chiller having an evaporator and a condenser with a closed refrigerant circuit between the evaporator and condenser; wherein water from the ambient source supplied to the second heat exchanger is chilled in the evaporator and returned to the second heat exchanger.
In another aspect, the invention provides a method for increasing the cooling efficiency of a generator/motor cooler that includes first and second heat exchangers operating in parallel, utilizing water from a common ambient source, and with gas to be cooled flowing past the first and second heat exchangers in series. The method comprises: a) diverting some or all of the water exiting the second heat exchanger to a chiller where the water is chilled; and b) returning the chilled water to the second heat exchanger.
REFERENCES:
patent: 4835977 (1989-06-01), Haglund et al.
patent: 5125378 (1992-06-01), Westerbeke, Jr.
patent: 5386687 (1995-02-01), Frutschi
patent: 6018942 (2000-02-01), Liebig
Boardman, IV William Hunter
Bosley Dewey Reed
Sapiro Edward Paul
Bennett Henry
General Electric Company
Jiang Chen-Wen
Nixon & Vanderhye P.C.
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