US 3443633 A
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y 3, 1969 'r. c. CARNAVOS v 3,443,633
TEMPERATURE COMPENSATED AIR-COOLED STEAM CONDENSER Filed March 30, 1967 F|G.I (PRIOR ART) OUTSIDE AIR F I G. 2 T 38 T OUTSIDE 5 AIR INVENTORI THEODORE C. CARNAVOS,
United States Patent 3,443,633 TEMPERATURE COMPENSATED AIR-COOLED STEAM CONDENSER Theodore C. Carnavos, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed Mar. 30, 1967, Ser. No. 627,157 Int. Cl. F28f 13/08 US. Cl. 165-108 2 Claims ABSTRACT OF THE DISCLOSURE A freeze-preventive air-cooled steam condenser having and air recirculation conduit, dampers to control same, and a heat admission conduit thereto.
Background of the invention This invention is related to steam condensers of the aircooled type. More particularly, it relates to an air-cooled steam condenser having provision for the prevention of freezing during sub-zero operation and for the removal of ice prior to startup.
Direct air-cooled steam condensers are known to the prior art and are used in areas where water is not readily available. In such a condenser, the atmospheric or ambient air is the cooling medium which passes over and around the condenser tubes which contain the steam and condensate.
schematically, and as shown in FIG. 1 of the drawing, a typical prior art air-cooled steam condenser includes a turbine steam exhaust pipe 2 terminating in a steam header 4 which in turn leads through a plurality of condenser tubes 6 to a condensate header 8 disposed somewhat below steam header 4 for the purpose of gravity drain of the condensate. Condensate from header 8 is led back to the steam system by means not shown. Condenser tubes 6 are disposed in the path, defined by conduit 10, of coolant air which is motivated therethrough by means of a fan 12. Fan 12 receives air from the outside ambient air through a protective louver 14 and discharges through a gravity shutter 16 into the path defined by conduit and over the condenser tubes 6.
The potential problem with an air-cooled condenser as just described arises in its use in very cold temperatures where there is a possibility of freezing of the condensate in the condenser tubes. Furthermore, after shutdown, such freezing is likely to occur so as to create a problem on subsequent startup.
Accordingly, it is an object of the present invention to provide an air-cooled steam condenser having a modification for the prevention of freezing during operation.
Another object is to provide an air cooled steam condenser with means to eliminate ice which may have formed during a shutdown period.
Other objects, advantages and features of the present invention will become apparent from the following description when taken in connection with the accompanying drawing.
Summary of the invention Briefly, the present invention is practiced in one form by an air cooled steam condenser having, in addition to the primary air flow circuit, a secondary air flow circuit recirculating the cooling air from the condenser tubes back to the fan suction. Dampers in the primary and secondary air flow circuits regulate the proportion of fan discharge air that circulates in each circuit. In addition, the suction side of the air fan is communicable with a source of heat to introduce the same to the condenser if it becomes desirable to melt ice. The secondary or re- 3,443,633 Patented May 13, 1969 'ice circulation air circuit provides warmer air for the condenser in the event that the outside ambient air is too cold.
Referring now to FIG. 2, a turbine exhaust pipe 22 is shown leading into a steam header 24 which in turn leads through a plurality of condenser tubes 26 to a condensate header 28, located below steam header 4 for purposes of gravity condensate flow.
Condenser tubes 26 are disposed in the path or circuit of cooling air defined between walls or conduits 30. Air is motivated through the cooling circuit by a motor operated fan 32 which receives air from two diiferent sources alternatively or in combination, as hereinafter described, and discharges it through gravity shutter 36 over the condenser tubes 26. Forming a part of wall 30 and located on the downstream side thereof from condenser tubes 26 is an adjustable damper or louver 38.
From fan 32, cooling air moves through gravity shutter 36 along the path shown by the solid arrows, which will be designated the primary air circuit and exits the apparatus through adjustable louvers 38. Primary air circuit is shown at A on the drawing.
A recirculation adjustable damper or louver 40 may be located downstream of the condenser tubes 26 and adjacent the louver 38. On the suction side of fan 32, an adjustable intake louver 34 provides air passages from the outside to the fan. Also on the intake or suction side of fan 32, an adjustable recirculation louver 42 is mounted in series with recirculation louver 40. The series passages provided by louvers 40 and 42, and shown by dotted arrows, will be designated the secondary or recirculation air circuit, and is shown at B on the drawing.
A conduit 44, which communicates with a heat source, not shown, is introduced to the condenser so as to communicate with the suction side of fan 32. Conduit 44 has a shutofi valve 46 therein. Conduit 44 may be introduced at the recirculation circuit B as shown, or it may be introduced directly into the intake side of the primary air circuit. The aforementioned heat source might be any suitable supply of heated air or gas. Typically, it might be the exhaust from a gas turbine used in conjunction with a steam turbine for which the present condenser is furnished in a combined steam-gas cycle.
Dampers or louvers 34, 38, 40 and 42 are adjustable between their closed and open positions and may be operated by hand or a suitable automatic control. Shutter 36 is gravity-operated so that when fan 32 is not running, shutter 36 is closed to prevent backflow of air.
Operation In normal operation, secondary or recirculating air circuit B is isolated. That is, louvers 40 and 42 are closed and shutolf valve 46 is closed. While an operating turbine is exhausting steam through its exhaust pipe 22, fan 32 is circulating outside ambient air through open louver 34 and through primary air circuit A over the condenser tubes 26 and out through open exhaust louver 38.
In operation at very low temperature, it will be apparent that exhaust steam flowing from pipe 22 and into condenser tubes 26 might possibly turn to ice in the condenser tubes due to the circulation thereover of the outside ambient air through primary air circuit A as above described. To prevent this, that is, to raise the temperature of the circulating air to a temperature above which freezing might result, adjustable louvers 34 and 38 are adjusted to a more closed position. Thus the intake of outside air through louver 34 is limited and the exhaust through louver 38 is limited. So that fan 32 continues to operate at full discharge capacity, recirculation louvers 40 and 42 are adjusted to a more open position. The result is that fan 32 receives its intake partially from the outside through louver 34 and partially from the recirculation loop B through louver 42. The fan discharge flows partially through louver 38 and partially through louver 40 into recirculation circuit B. Of course, fan discharge air as it passes over condenser tubes 26 is warmed and therefore, air circulating through circuit B and back to the fan suction is warmer than outside ambient air. By regulating the degree of opening of louvers 34 and 38 and of louvers 40 and 42 in the recirculation circuit, the temperature of air discharging from fan 32 over the condenser tubes can be regulated so as to be kept as cool as possible and yet kept above the point where condensate freezing occurs.
For starting the system after a shutdown in cold weather, louvers 34 and 38 can be either partially or fully closed with louvers 40 and 42 open. Valve 46 is open permitting the flow therethrough of warmed fluid from the heat source through conduit 44. Fan 32 motivates such warmed fluid around the circuit over the condenser tubes and through recirculation circuit B until the system is completely thawed and ready for operation.
It will be apparent that an air-cooled steam condenser has herein been provided which is effective to prevent freezing during operation in even the coldest weather.
Furthermore, the air-cooled steam condenser of the present invention has provided a means to facilitate the restarting of an air-cooled steam condenser after shutdown in cold weather.
It may occur to others of ordinary skill in the art to make modifications of the present invention which will remain within the concept and scope thereof and not constitute a departure therefrom. Accordingly, it is intended that the invention be not limited by the details in which it has been described but that it encompass all within the purview of the following claims:
What is claimed is:
1. An air-cooled steam condenser including steam condensing tubes disposed within a primary air flow circuit, said circuit communicating at its intake and exhaust ends with the atmosphere, and blower means to motivate air through said circuit, said condenser being characterized by the improvement comprising:
first adjustable damper means to throttle the air flow from the atmosphere into said circuit,
second adjustable damper means to throttle the air flow from said circuit to the atmosphere,
a recirculation circuit communicating with said primary circuit on the intake side of said air motivating means and on the downstream side of said steam condensing tubes, and
third adjustable damper means to regulate the air flow through said recirculation circuit to keep air flow around said condensing tubes substantially constant,
said improvement being operative to eifect steam condensation and to prevent freezing of the resulting condensate in said tubes, and
means to selectively increase the thermal energy of air circulating over said condensing tubes, said means comprising a conduit communicating with a source of heated fluid at a higher temperature than the steam in said condensing tubes and connected to the intake side of said blower means.
2. An air-cooled steam condenser including steam condensing tubes disposed within the flow path of a primary air flow circuit,
said circuit communicating at its intake and exhaust ends with the atmosphere, and a fan to motivate air through said circuit, said condenser being characterized by the improvement comprising:
a recirculation air flow circuit communicating with said primary circuit on the intake side of said fan and on the downstream side of said steam condensing tubes,
means to throttle air flow at the intake and exhaust ends of said primary,
means to throttle air flow through said recirculation circuit,
said improvement being operative to effect steam condensation and to prevent freezing of the resulting condensate in said tubes, and
means to add heat to the air circulating over said condensing tubes,
said last-named means comprising a conduit communicating with a source of heated fluid at a higher temperature than the steam in said condensing tubes and connected to said recirculation circuit, and means to open and close said conduit to control the flow of said heated fluid into said recirculation circuit.
References Cited UNITED STATES PATENTS 1,563,963 12/1925 Byrd 165--108 X 1,564,566 12/1925 Harris l108 X 2,247,987 7/1941 Carson -103 2,665,840 1/1954 Powell 165--108 ROBERT A. OLEARY, Primary Examiner.
THEOPHIL W. STREULE, Assistant Examiner.