US2697587A - Controlled temperature fan cooled heat exchanger - Google Patents

Description

Dec. 21, 1954 CONISON CONTROLLED TEMPERATURE FAN COOLED HEAT EXCHANGER Filed April 16, 1951 2 Shee ts-Sheet 1 (HIHTL (F All??? 30 if /J5 JOSEPH CON/801V,

INVENTOR.

J. CONISON 2,697,587 CONTROLLED TEMPERATURE FAN COOLED HEAT EXCHANGER 2 Sheets-Sheet 2 am W T755524 CON/601V,

INVENTOR.

Dec. 21, 1954 Filed April 16, 1951 United States Patent CONTROLLED TEMPERATURE FAN COOLED HEAT EXCHANGER Joseph Conison, Los Angeles,

Fluor Corporation, ration of California Application April 16, 1951, Serial No. 221,289 13 Claims. (Cl. 257-2) Ltd., Los Angeles, Calif., a corpo- This invention relates to improved air cooled heat exchangers and trolling the temperature of fluid discharged from such heat exchangers. In certain of its aspects, the invention is especially concerned with heat exchangers of the multiple cell type, including a number of individual cells or sections having interconnected fluid conducting heat exparticularly to novel apparatus for con-' Calif., assignor to The and stopping of the various fans is automatically 4 determined change in fluid discharge temperature to start or stop the fans individually and in a predetermined sequence. Preferably, the fan control apparatus is designed to allow a predetermined timing period between the starting or stopping of each two successive fans, during which period the change in condition of the first fan is given an opportunity to compensate for the abnormal temperature. If the first fan does not prove capable of correcting the temperature during the timing period, a second fan is started or stopped (as the case may be), and a second timing period then allowed before starting or stopping a third, fourth and other fans. When the starting or stopping of one of the fans ultimately succeeds in correcting the undesired fluid discharge temperature. the control apparatus automatically becomes ineffective to cut in or out any further fans.

To effect such sequential actuation of the fans, I may employ two timers, one operable when energized to sequentially start the fans, and the other operable to sequentially stop the fans. The fan starting timer is automatically energized upon a predetermined rise in temperature to start one or more fans, and the fan stopping timer is energized upon a predetermined fall in temperature to stop one or more fans.

For assuring accurate temperature control over a very wide range of temperatures, I may employ, in conjunction with one or more air cooled heat exchanger cells, a by-pass valve through which a controlled amount of fluid may by-pass about the heat exchanger tubes. When such a by-pass valve is employed, an important feature of the invention resides in the provision of temperature responsive means for automatically controlling both the valve and fan in accordance with changes in the fluid discharge temperature. Preferably, the by-pass valve is adjusted between its open and closed conditions in response to temperature changes within a predetermined range, and a fan motor is started or stopped only when the valve control reaches the limits of that range, that is, only when the valve is either completely opened or completely closed. When the heat exchanger includes a number of individual sections or cells, the previously discussed timers may be energized upon complete closure or opening of the by-pa'ss valve to start or stop the various fans in timed sequence, the fans being started or stopped at predetermined intervals until the valve again moves to an intermediate position.

An additional object of the invention is to provide means for synchronizing a pair of fan starting and stopping timers of the above character in a manner maintaining them in step, so that even if less than all of the .fans are in operation, the fan stopping timer will always ICC be properly conditioned to act next on one of the operatmg fans, rather than to attempt to stop an already deenergized fan, and vice versa the fan starting timer will always be conditioned to act next on a stopped fan. Such synchronizing means may include a number of parallel connected interlock relays responsive to energization of the fans respectively and acting to break the energizing circuit to each of the timers when the fans are all in the condition to which that timer tends to actuate them.

A still further object is to provide means operable after a temporary power failure to restart those fans that were in operation prior to the failure, so that the apparatus {Jeturns to exactly the condition in which it had previously een.

The above and other features and objects of the present invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawings, in which:

Fig. 1 is a vertical section through a multi-cell mechanical draft heat exchanger for cooling to a predetermined temperature a stream of cooling water or other fluid; and

Fig. 2 is a diagrammatic view of the electrical control app arattis for controlling the operation of the cooling fans in 1g.

Referring first to Fig. 1, the illustrated cooling apparatus includes a plurality of heat exchanger cells 10 each containing near its upper end one or more banks of heat exchanging tubes 11, and each having a fan 12 for creating an upward draft of cooling air past the tubes. The tube banks 11 of the various cells are connected in parallel, all receiving fluid from a line 13 and discharging the cooled fluid through a line 14. Lines 14 and 13 may typically deliver cooling water to and from the water jacket of a compressor, engine or other piece of operating equipment. Under certain circumstances, some or all of the fluid may be by-passed about the heat exchanger tubes by passage through by-pass line 15, under the control of by-pass valve 16, to regulate the cooling effect of the tubes. Valve 16 is pneumatically actuated between its open and closed conditions in accordance with the operation of a temperature responsive valve type instrument, hereinafter referred to as valve 17, connected into fluid discharg line 14 leading from the tube banks. When valve 16 reaches either its fully open or fully closed condition, valve 17 penumatically actuates the electrical control apparatus of Fig. 2 to start or stop one or more of the fan driving motors 18 and thus further regulate the cooling effect of the heat exchanger cells.

The various cells 10 may typically be formed in a unitary housing 19 mounted on a suitable base 20. The housing may include a pair of elongated side walls 21 extending along the opposite sides of all of the cells, a pair of end walls 22, and two interior partitions 23 sepa rating the cells. The fans 12 are individually mounted to base 20 for rotation about vertical axes by upstanding frames 24, and are driven by motors 18 through reduction gears 25 and shafts 26. The usual shrouds 27 are provided about fans 12 to assure a maximum draft from the fans. At a location beneath shrouds 27, the housing side walls 21 and end walls 22 take the form of screens 28, through which air may enter the cells to be blown upwardly by the fans and past the tube banks 11.

Compressed air for actuating by-pass valve 16 and the fan motor controlling apparatus of Fig. 2 is supplied through a line 29 to temperature responsive valve 17, which controls the pressure of air admitted to control line 30 in accordance with the changes in fluid discharge temperature. Valve 17 is so designed that a rise in the temperature of fluid in discharge line 14 partially opens the valve to increase the pressure of air in line 30, and conversely a falling temperature partially closes valve 17 to decrease the pressure in line 30. The temperature controlled pressure in line 30 actuates by-pass valve 16 through diaphragm 31, to compensate for whatever temperature variations may occur. This controlled pressure air in line 30 is also communicated to two diaphragm actuated switches LPS-l and HPS, by which the motor starting and stopping circuits of Fig. 2 are controlled. Specifically, switch LPS-l is designed to close a fan motor starting circuit at the moment when the fluid discharge temperature in line 14 and the air pressure in line 30 have reached such values as to completely close by-pass valve 16. Similarly, switch HPS closes a fan motor stopping circuit when by-pass valve 16 has been completely opened. A third pressure actuated switch LPS-2 is responsive to the pressure in compressed air supply line 29 and breaks both the starting and stopping circuits when the air in line 29 falls below a predetermined value.

In the electrical fan motor control apparatus of Fig. 2, certain elements which are duplicated for each of the various fans have been shown only once, in the interest of simplifying the circuit diagram. Specifically, it is noted that the portion of the circuit enclosed by the dot-dash lines is associated with fan motor No. 1, and is to be considered as duplicated for each of the other fans.

Low pressure switch LPS-l controls the energization of timer 32, which when energized is operable to sequentially start the various fan motors. This timer includes electric motor 33 driving at a relatively slow rate a shaft 34 which carries a number of switch actuating parts. Typically, for clarity of illustration, these parts are represented as comprising four disks 35a, 35b, 35c and 35d rotatable with the shaft and each carrying one or more switch actuating fingers or lugs 36. Timer operated disks 35a, 35b and 35c are associated with fan motors 1, 2 and 3 respectively, and are operable through fingers 36 to actuate switches 37a, 37b and 37c for closing starting circuits to the corresponding fan motors. The fourth disk 35d controls the actuation of a switch 38 for controlling the period of operation of the timer motor upon each actuation by the low pressure switch.

Timer motor 33 is energized from power supplied through lines 39 and 40. One terminal 41 of the timer is connected to line 40 through low pressure switch LPS-2, low pressure switch LPS-l, and the parallel connected normally closed contacts of three timer interlock relays 43a, 43b and 43c associated with the three fan motors respectively. A second circuit from supply line 40 to timer terminal 42 is completed by the closing of timer actuated switch 38.

A second timer 46 is provided for controlling the stopping of the various fan motors, as directed by actuation of high pressure switch HPS. This second timer is substantially identical to the first timer, including a motor 47 driving a shaft 48 carrying disks 49a, 49b, 49c and 49d having switch actuating fingers 40. The fingers carried by disks 49a, 49b and 490 are operable to actuate fan stopping switches 51a, 51b and 510 associated with the three fan motors. Disk 49d controls a switch 52 which determines the period of timer operation on each closing of HPS.

A first terminal 53 of timer motor 47 is connected to the first power supply line 39. The second timer motor terminal 54 is connected to line 40 by a circuit including switch LPS-Z, switch HPS, and the parallel connected normally open contacts of interlock relays 43a, 43b and 43c. Timer actuated switch 52 closes a second circuit between line 40 and timer motor terminal 54.

Referring now to the portion of Fig. 2 enclosed within the dot-dash lines. each fan motor is energized from a 480 volt 3 phase A. C. power supply through three lines 55. The current supply through these three lines is controlled by switches 56 which are drawn to closed condition by energization of relay coil 57. Coil 57 and other parts of the fan motor control circuit are energized by a transformer 58, whose primary is connected across two of the power supply lines.

Closing of the primary controlled fan starting switch 37a closes an energizing circuit to relay coil 57, leading from a first side of the transformer secondary through cell 57, vibration responsive switch 58, the normally closed contacts of manual stop switch 59, primary actuated switch 37a and the normally closed contacts of primaryactuated stop switch 510 and then back to the second side of the transformer secondary. A similar circurt may be closed by actuation of manual start switch 60, which is connected in parallel with the timer operated start switch 37a. Upon energizing relay coil 57 by closmg either of the start switches, the relay actuated switches or contacts 56 are drawn to closed positions to energlze the corresponding fan motor. Energization of coil 57 also closes a fourth switch 61, connected in parallel with the two start switches, to maintain closed the energizing circuit to coil 57, even though the start a switch which had been open may return to its normal closed condition. The fan motor then continues to operate until the circuit to coil 57 is broken by either actuation of the manual stop switch 59 or timer operated stop switch 51a.

For starting the fan motor after a temporary power failure, if the motor had been in operation prior to the failure, I provide a third starting circuit in parallel with start switch 37a and 69. This third starting circuit includes a normally open relay contact 62 adapted to be drawn to closed condition by energization of relay coil 63, and a second normally open relay contact 64a. Coil 63 is connected in parallel with coil 57, to be energized and close contact 62 whenever the corresponding fan is in operation. Latch 65 maintains contact 62 in its closed condition when once actuated to that condition by energization of coil 63, and is releasable by energization of release coil 66, to permit return of contact 62 to its normal open position. An energizing circuit to latch release coil 66 is closed upon actuation of either of the stop switches 59 or 51a, by closure of the normally open contacts of these stop switches. Thus, under normal operation, contact 62 is closed when the corresponding motor is in operation, and is open when the motor is stopped. If power fails while the motor is operating, latch 65 maintains contact 62 closed, to complete a temporary start circuit with contact 64a upon resumption of power.

Contact 64a and corresponding contacts 64b and 64c in the circuits of the second and third fan motors, are closed by energization of relay coil 67, under the control of normally closed time delay relay 63. Relay 68 is so constructed as to remain temporarily closed for a brief interval when power returns after a failure, to thus temporarily energize coil 67 for closing contacts 64a, 64b and 64c. Such closure of contacts 64a, 64b and 64c closes start switches through the contacts 62 associated with the fans that had been operating prior to the power failure, and thus restarts those fans. After a period sufficient to effect such starting of the fans, delay relay 68 opens, deenergizing coil 67 to permit contacts 64a, 64b and 640 to return to their normal open condition.

Coil 69a of timer interlock relay 43a associated with fan motor No. 1 is connected in parallel with relay coils 57 and 63, to actuate the movable contact '74) of relay 43a from its normal full line position of Pig. 2 to its broken line position while fan motor No. 1 is operating. Coils 69b and 690 of interlock relays 43b and 43c are connected into the control circuits of fans 2 and 3 in the same way that 69a is connected into the illustrated fan No. 1 control circuit.

When the disclosed heat exchanging apparatus is in operation, variations in fluid discharge temperature within a predetermined range are compensated for by variation of the setting of by-pass valve 16 between its open and closed conditions. For instance, a rise in the ternperature of fluid within discharge line 14 partially closes temperature responsive valve 17 to reduce the air pressure in line 30 and permit corresponding closure of valve 16. As a result, less fluid is by-passed through valve 16, and more fluid is required to pass through the heat exchanger tube banks 11 for cooling by the fan created air drafts. Similarly, a fall in fluid discharge temperature opens valve 17 and valve 16 to by-pass more fluid and decrease the cooling elfectiveness of the heat exchanger cells.

If the fluid discharge temperature rises to a value at which by-pass valve 16 is completely closed. low pressure switch LPS-l is then automatically closed to complete the energizing circuit to timer motor 33. As this timer motor then commences to rotate shaft 34 and the carried disks, one of the fingers on disk 35d engages and closes switch 38. This switch completes a second energizing circuit to timer motor 33 and is of a nature to remain closed and maintain energization of the timer motor until a second finger 36 on disk 35:! opens the switch. The fingers 36 of disk 35d are so positioned as to continue the operation of timer motor 33 through approximately /3 of a disk revolution (when three fan motors are being controlled) During the initial stages of a /3 revolution of shaft 34, caused by closure of switch LPS-l and resultant closure of timer actuated switch 38, the finger 36 on one of the fan controlling disks 35a, 3512 or 35c actuates its associated switch 37a, 37b, or 37c to close the previously defined start circuit of the corresponding fan motor. This energizes coil 57 to close fan starting contact 56 and holding contacts 61 commencing and maintaining operation of the fan.

Timer shaft 34 slowly rotates through the major portion of the /3 revolution timing period after the starting of the first fan. The time required for this /3 revolution of the timer gives the started fan a period in which to lower the fluid discharge temperature to a value again opening LPS-l. If the temperature has not been lowered to such a value when the timer completes a /3 revolution, LPS-l remains closed to start another /2, revolution timing period. During this second period, a second fan is started, to further increase the cooling eflect of the heat exchanger. When all of the fans have been started in this manner, all of the interlock relays 43a, 43b and 430 will be in their broken line condition, to break the energizing circuit to timer motor 33 and prevent this motor from getting out of phase with the second timer motor 47 by attempting to start fans already in operaion.

If the fluid discharge temperature falls to a value in which by-pass valve 16 is completely open, high pressure switch HPS is closed to energize timer motor 47 for stopping one or more of the fan motors. The operation of timer motor 47 is substantially the same as motor 33, and will not be discussed in detail. When all of the fan motors are stopped, relays 43a, 43b and 43c will be in their full line positions, to break the energizing circuit to timer motor 47 and prevent its further operation.

In the event of temporary power failure, the contact 62 of the fans that had been operating prior to the failure are latched in closed condition, so that the temporary closure of contacts 64a, 64b and 640 upon return of power closes starting circuits to the previously operating fans to again set them in operation. If the pressure of control air line 29 falls to a predetermined value, switch LPS-Q is opened to break the circuits to both the timers. Vibration responsive switch 58 is mounted near the associated fan, to open the circuit to relay coil 57, stopping the fan, 1f the fan commences to vibrate.

I claim:

1. Heat exchanging apparatus comprising a plurality of cells having interconnected heat exchanger conduits through which a common fluid is passed and having 1ndividual power driven fans for producing air drafts past the conduits respectively, fan control means operable to individually and sequentially actuate said fans between running and stopped conditions, and temperature responsive means controlling said fan control means, said temperature responsive means being exposed to and actuated by variations in temperature of the fluid passed through said conduits, and operable upon predetermined change in temperature of said fluid to cause said control means to sequentially actuate said fans to one of said conditions.

2. Heat exchanging apparatus comprising a plurality of cells having interconnected heat exchanger conduits through which a common fluid is passed and having individual power driven fans for producing an drafts past the conduits respectively, a first timer operable to sequentially start said fans, a second timer operable to sequentially stop the fans, and temperature responsive means controlling the operation of said timers, said temperature responsive means being exposed to and actuated by the variations in temperature of the fluid passed through sa d conduits and operable upon predetermined changes in said fluid temperature to actuate said timers respectively to sequentially start and stop the fans.

3. Heat exchanging apparatus comprising a plural ty of cells having interconnected heat exchanger condmts through which a fluid is passed and having individual power driven fans for producing air drafts past the conduits respectively, a timer operable through a predetermined timing cycle to sequentially actuate said fans between running and stopped conditions, temperature responsive means controlling said timer, said temperature responsive means being exposed to and actuated by variations in temperature of the fluid passed through said conduits, and control means operable by said temperature responsive means in response to a predetermined change in the temperature of said fluid to operate the timer through a portion of said cycle to actuate only one of the fans between said conditions, said control means being operable by said temperature responsive means upon further change in fluid temperature to sequentially actuate the other fans between said conditions.

4. Heat exchanging apparatus comprising a plurality of cells having interconnected fluid conducting heat exchanger tube banks, said cells having individual fans for producing air drafts past the tube banks and having individual electric motors for driving said fans, a first electrically energized rotary timer operable through a timing cycle to sequentially start said fans, a second electrically energized rotary timer operable through a timing cycle to sequentially stop said fans, a pair of switches for closing energizing circuits to said timers respectively, temperature responsive means operable to actuate said switches in accordance with changes in the temperature of fluid discharged from the tubes, and a pair of timer actuated switches each operable in response to energization of a corresponding one of said timers to close a circuit maintaining the timer energized for a predetermined period suflicient to start or stop one of the fans and then position the timer for a subsequent operation.

5. Heat exchanging apparatus comprising a heat exchanger conduit through which a fluid is passed, a power driven fan positioned to create a draft of air past said conduit, a by-pass valve through which fluid may bypass about the conduit, means for starting and stopping said fan, temperature responsive means exposed to and actuated by variations in the temperature of said fluid and operable to vary the setting of said by-pass valve in accordance with changes between a pair of values in said fluid temperature, and means responsive to changes in said fluid temperature to said values to actuate said fan starting and stopping means to start or stop the fan, said last mentioned means being ineffective to start or stop said fans as a result of variations in said fluid temperature between said pair of values.

6. Heat exchanging apparatus comprising a plurality of cells having interconnected heat exchanger conduits through which a fluid is passed and having individual power driven fans for producing air drafts past said conduits respectively, a by-pass valve through which fluid may by-pass about all of said conduits, means including a timer operable to sequentially actuate said fans between running and stopped conditions, and temperature responsive control means operable to actuate said bypass valve and said timer, said temperature responsive means being exposed to and actuated by variations in the temperature of the fluid passed through said conduits to actuate said valve and timer in accordance therewith.

7. Heat exchanging apparatus comprising a plurality of cells having interconnected fluid conducting heat exchanger conduits and individual power driven fans for producing air drafts past said conduits, a bypass valve through which fluid may by-pass about the conduits, a first timer operable to sequentially start said fans, a second timer operable to sequentially stop the fans, temperature responsive means for varying the setting of said by-pass valve in accordance with changes between a pair of" values in the temperature of fluid discharged from the conduits, and means responsive to the change of said fluid discharge temperature to said values to energize said timers respectively.

8. Heat exchanging apparatus comprising a plurality of cells having interconnected fluid conducting heat exchanger tube banks, said cells having individual fans for producing air drafts past the tube banks and having individual electric motors for driving said fans, a first electrically energized rotary timer operable through a timing cycle to sequentially start said fans, a second electrically energized rotary timer operable through a timing cycle to sequentially stop said fans, a pair of switches for closing energizing circuits to said timers respectively, a bypass valve through which fluid may by-pass about said tube banks, temperature responsive means operable to vary the setting of said valve in accordance with changes between a pair of values in the fluid discharge temperature from the tubes, means responsive to change of said fluid discharge temperature to said values to actuate said switches for energizing the timers respectively, and a pair of timer actuated switches each operable in response to energization of a corresponding one of said timers to close a circuit maintaining the timer energized for a predetermined period sufficient to start or stop one of the fans and then position the timer for a subsequent operation.

9. Heat exchanging apparatus comprising a plurality of cells having interconnected fluid conducting heat exchanger conduits and individual power driven fans for producing air drafts past said conduits, a first electrically energized ttimer :operable :to sequentially :start zsaid 'fans, :a; second electrically {energized timer operable to sequenrtiallyfistop the fans, temperature responsive control means operable ,to energize :said timers in accordance 'with changes in the temperature of fluid discharged from the conduits, and electrical interlock means operable to .open the energizingcircuit to said first timer when all of the fans are in operation and to'open the energizing circuit to the second timer when all of the fans are stopped.

v10. Heat exchanging apparatus comprising a plurality of cells having interconnected fluid conducting heat ex changer conduits and individual power driven fans for producing air drafts past said conduits, a first electrically energized timer operable to sequentially start said fans, a second electrically energized timer operable to sequentially stop the fans, temperature responsive control means operable to energize said timers in accordance with changes in the temperature of fluid discharged from the conduits, and electrical interlock means operable to open the energizing circuit :to said first timer when all of .the fans are in operation and to open the energizing circuit to the second timer when all of the :fans are stopped, said interlock means including individual switch means associated with said ,fans respectively and each operable between a pair of conditions in accordance with the energization and deenergization of the corresponding ,fan, said switch means having first contacts open and second contacts closed when the corresponding fans are in operation, said first contacts being closed and said -second contacts open when the fans are stopped, said first contacts being interconnected in parallel and connected as a group into the energizing circuit of said first timer, and said second contacts being interconnected in parallel and connected as a group into the energizing circuit of the second timer.

11. For use in association with heat exchanging apparatus including a plurality of cells having interconnected fluid conducting conduits and individual power driven fans for producing air drafts past said conduits, and including a by-pass valve through which fluid may by-pass around the conduits; a first timer operable to sequentially start said fans, a second timer operable to sequentially stop said fans, temperature responsive means for varying the setting of said by-pass valve in accordance with changes between a pair of values in the temperature of fluid discharged from the conduits, and means responsive to the change of said fluid discharge temperature to said values to energize said timers respectively.

51-2. Heat exchanging apparatus including a plurality 'of cells having interconnected conduits through which alfluid is passed and [having individual power driven fans for producing air drafts past .said conduits, means operable to individually and sequentially start and stop said Ifans, temperature controlled means exposed to and actuated by changes in temperature of fluid which passes through said conduits, means operable by said temperature controlled means to actuate the fan starting and stopping means to sequentially start or stop the fans in accordance with said temperature changes, and means operable after a power failure to actuate said starting and stopping means to restart those fans that were in operation prior to the failure.

13. Heat exchanging apparatus comprising a plurality of cells having interconnected heat exchanger conduits through which a fluid is passed and having individual power driven fans for producing air drafts past the conduits, said cells including walls separating the cells one from the other and directing the major portion of the air displaced by each fan past only a corresponding one of said conduits, means operable to individually start and stop said fans, and temperature responsive means controlling the operation of said first mentioned means and operable 'to cause said first mentioned means to separately start and stop said fans, said temperature responsive means being-exposed to and actuable by variations in the temperature of the fluid which passes through said conduits.

References Cited in the file of this patent UNITED STATES PATENTS Number Name .Date

2,237,304 Greenlee Apr. 8, 1941 2,286,538 Guler June 16, 1942 2,297,970 Merz Oct. 6, 1942 2,313,439 Horton Mar. 9, 1943 2,458,683 Cowherd et al. Ian. 11 1948 2,480,120 Cruzan Aug. 30, 1949 2,488,636 Mendenhall etal Nov. 22, 1949 2,518,760 Dieter Aug. 15, 1950 2,548,324 Smith Apr. '10, 1951 FOREIGN PATENTS Number Country Date 363,370 Great Britain Dec. 10, 1931

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