USRE22533E

USRE22533E - Apparatus for cooling a stream of

Info

Publication number: USRE22533E
Authority: US
Priority date: 1941-11-17
Publication date: 1944-08-22
Also published as: US2296946A

Description

Aug. 22, 1944.

M. H. OLSTAD ETAL APPARATUS FOR COOLING STREAMS OF FLUID Original Filed Nov. 17, 1941 I INVENTOR mwzzoaam M 7 ivrromuzg.

- water necessary for the We Aug. 1944 Re. 22,533 f 22,53: ArrAnA'rUs ron 000mm A s'raaAM or rwm 7 Martin a. Olstad, Bayside, one Allan E. Williams,

White Plains, N. 1., alsignors to Niagara Blower Company, New York, N.

York

Y.. a corporation oililew Original No. 2,296,946, dated September 29, 1942,

Serial No. 419,412, November 17, 1941. Application for reissue October 11, 1943, Serial No.

This invention relates to apparatus for cooling a stream of fluid and more particularly is shown,

as an example of its use, as embodied and carried out in a heat exchanger for maintaining the desired temperature of quenching oil used in tempering steel. However, the invention can be used in conjunction with liquids other than quench ing oils andthe invention is therefore not to be construed as limited to any particular fluid to be treated.

In the tempering of steel, the steel at temperatures as high as 2000 1". is quenched in a bath of quenching oil which must be maintained near the proper temperature in order that the cooling of the steel, in tempering, be effected at acertain rate. The bath of quenching oil is heated by the batches of steel being tempered and in order to maintain the proper temperature of the quenching oil, the quenching all must be continuously recirculated through a cooler so as to maintain the desired temperature of the quenching bath while tempering the steel. The quenching oil may include a large percentage of lard oil which may deposit on the heat transfer surface of the c'ooler in the form of a wax. This wax builds up until the heat transfer between the cooling surface and the quenching oil is greatly reduced and the capacity of the cooler greatly diminished.

with oil cooling systems now in use, no adequate provision is made'for dewaxing the cooling \8.Claims. (01.257-2) close limits, that is, within 1''. when used cool quenching oil.

Another object of the invention is to provide such apparatus which is tullyautomatlc in maintalning the desired temperature of the liquid being treated.

Another object of the invention is to provide a simple and efl'ectlve control for the minimum temperature of the liquid being treated by the surface and also, with'systems now in use, while it is possible to cool the quenching oilbath, no

provision is made for heating the bath. There;

'iore, at the start of theoperation of tempering steel, or in shifting to higher temperature quenching. it has been the practice for the operator to pass a few batches of hot steel through the bath merely to bring the bath up to the desired quenching temperature.

Thepassing of hot steel merely to. bring up the temperature of adjustment of the character of the air supplied to the apparatus.

Another object of the invention s to provide such apparatus in which such control can be effected entirely automatically in response to the temperature oi the liquid being treated.

Another object is to provide such apparatus in which, where the cooling eifect is obtained from theevaporation of water. the amount of moisture evaporated to provide the cooling effect is reduced to a minimum.

Another object of the invention is to provide for dewaxlng the cooling surface, when used for cooling quenching oil, so as to insure the proper heat transfer between the cooling surface and the quenching oil at all times.

Another object 01' the invention is to provide for heating the quenching oil. when desired, so as to bring it up to the proper temperaturefor -use' in tempering steel, and thereby avoid the I where the cooling eireet is obtained ironi the evaporation of water, a simple and eflective means for maintaining any desired minimum temperature of the spray water'whic'h is evaporated, thereby to provide a more exact control the quenching bath to that desired involves, oi

course, waste labor and also. the possible loss of a large quantity of steel in the event that it cannot be retempered at the desired temperature.

It is one of the principal objects of the present invention to provide a simple and-efficient apparatus adapted to cool a fluid in which the cooling eflect is obtained from the evaporation of water, thereby to greatly reduce the amount of cooling operation of the apparat a w I Another object of the invention is to provide such apparatus in which the temperature of the liquid beingtreated is maintained within very Oil.

of the cooling effect of the apparatus.

Another object is to maintain the apparatus under such conditions that no substantial amounts; of lard oil are precipitated out on the cooling surface, when used for cooling quenching --1 Other objects are to provide such apparatus .which is simple and inexpensive in construction and which will stand up under conditignhog severe and constant use without getting out of order or requiringrepairs.

In the accompanying drawing; Fig. 1 is a diagrammatic perspective view of a heat exchanger embodying and carrying out the invention.

Fig. 2 is a fragmentary, vertical, transverse section, taken on line 2-2, Fig. 1.

The heat exchanger shown, by way oi. example in the accompanying drawing, is particularly designed for maintaining the desired temperatureof thequenching oil used in tempering steel, in which use it operates at most times to cool the quenching oil, provision being made, however, forheating the quenching oil and also to maintain the desired minimum temperature of the water used for cooling, through the heating means. The apparatus shown is designed to eflect cooling through the evaporation of water and includes a sheet metal casing which is mounted upon a tank 6 forming the base of the casing, this tank 6 containinga body of water I which is evaporated'to provide the cooling effect. .The tank 6 is preferably extended beyond one end of the casing 5,

shown as provided with a top 3.

A plurality o1 fan housings ID are mounted in the upper part of the casing 5, the, inlets of these fan housings being in communication with the interior of the casing 5 so as to exhaust air therefrom. A common shaft ll extends through the several fan housings l0. and is shown'as driven by a motor I2 mounted on a bracket I 3 at one end of the casing 5. Within each fan housing the shai't ll carries a fan l4 of any suitable construcas indicated at 8, and this extension is.

quenching tank (not shown) a The quenching oil or other fluid to be treated is supplied through a tion, these fans drawing the air from the interior I of the casing 5 and discharging it through the outlets I 5 oi. the several tan housings which proiect upwardly through the top of the casing 5. These outlets discharge-the air into a vertical duct 20, the upper end of which forms an air discharge duct for exhausting the air to the outer atmosphere. A horizontal recirculation air duct 2| communicates with one side of the vertical duct- 20, this recirculation air duct discharging into a vertical duct 22' arrangedin rear of, the casing 5 and this vertical duct 22 being provided with a lower horizontal leg 23 which is in communication with the lower part of the casing 5 immediately above the tank 6. A cold air intake duct 26 also discharges into the vertical duct 22, this cold air intake duct being preferably in horizontal alinement with therecirculation air duct 2|.

..Means are provided for delivering difierent proportions of cold'outside air from the duct 26 .andrecirculated or return air from the duct 2| intothe duct 22. For this purpose a fresh air damper 30 is arrangedin the cold outside air duct 26 and a recirculation damper 3| is arranged,

in the vertical air discharge duct 20 in position to close the opening into the recirculation air duct 2|. This recirculation damper 3|, when moved away from the opening into the recirculation air duct, is alsomoved to restrict theair discharge duct 20 thereby to reduce the amount of air exhausted to the atmosphere in relation to the amount of air recirculated through the recirculation duct 2|. I

The fresh air damper 30 is provided with an operating lever 32 which projects downwardly and the recirculation damper 3| isprovided with a lever 33 which projects upwardly. The free ends of these levers 32 and 33' are connected by a-bar 34, the central part of which isconnected by a link 35 with the arm 3601 a damper motor 31, this damper motor 31 being shown as being line 42, the inlet and outlet lines 42, 43 ior'the quenching oil connecting with the headers of a.

bank of coils 44 arranged within the casing 5 im mediately above 'the opening from the duct 23. these coils being thereby arranged in the path of the air drawn from the duct 23 and upwardly through the casing 5 by the Ian wheels l4.

Immediately below the bank oi' coils 44 a second bank of coils 45 is arranged, this second bank of coils 45 being supplied with steam from a steam line 46, the condensate being withdrawn from these coils through a line 41. The steam or other heating medium supplied to the coils 45 is under control of a valve 48 which is actuated in response to an immersion thermostat 43, the sensitive parts I of which are immersed in the body of water 1 contained within the tank 8. The steam valve 48 can also be placed under manual control and for' this purpose the immersion thermostat 49 is shown as connected to the steam valve 48 by a wire 50, and the other wires BI and 52 connected,-

respectively, with the steam valve 48 and immersion thermostat 49 are shown as connected through a manual switch 53 with the main power lines 54 and 55. a

The water I to the tank 6 can be supplied in'any suitable manner and is shown as maintained at a constant level by an overflow connection 58in the upper part of the tank 8, this overflow 56 leading to a drain line 51 connected with the bot-' tom part or the tank 8. A drain valve 58 is provided in thedrain line 51 between the tank 8 and the connection of'this drain line 51 withthe overflow line Eli.

The water I in the tank 6 is withdrawn by a centrifugal spray water pump ill and is discharged through a vertical pipe 3| into a horizontal pipe 62 extending lengthwise through the interior of the casing above the bank of coils 44. This pipe 62 carries a suitable number of branch pipes 63, each of which carries a downwardlydischarging nozzle. The nozzles 64 are arranged above the bank of coils 44 which carry the quenching oil or other liquid to be cooled so that these coils 44 are constantly flushed with water. The excess water from the coils 44 falls back into the tank 6 to be again recirculated bythe spray water pump 80.

Assuming that the quencbingoil is being used for tempering steel and that the heat exchanger forming the subjectof the invention is operatin under heavy cooling load conditions, th1s,.hot

mounted on a bracket 38 secured to theexterior of the duct 22. The control line 40 to the damper motor 31 connects with a thermostat 4|, the sensi- 'tive parts 01 which are immersed in the quenching oil or other fluid being cooled, which leaves the apparatus through a return line 42, this return line discharging the quenching oil bath into the quenching oil enters the bank of cooling coils 44 from the supply line 43 and is returned to the tempering bath through the line 42. The quench- U lug oil so passing through the bank of coils 44 is arranged in the stream of air which, under heavy cooling load conditions, is drawn by the fan wheels l4'i'rom the cold air intake duct 26 through the vertical duct 22 and horizontal leg 23 into the bottom of the casing 5, this cold outside air being.

drawn vertically upward through the casing-5 and discharged by the fan wheels l4 into the air discharge duct 20. At the same time the body of water 1 in the tank 6 is, being pumped by the spray water ump 60, through

the'pipes

6 l, 62 and 63 and is sprayed onto the bank of coils 44 by the nozzles 64, the excess spray water collecting in the tank 6.- The'bank of coils 44 carrying the hot quenching oil is'threby flooded with water. this water evaporating on these coils, the coils 44 tending to assume the wet bulb temperature of the air drawn upwardly through these coils by the fan wheels I4. The quenching oil passing through eases pered batch of steel and the introduction of a batch of hot steel into the bath of quenchin! oil to be tempered, the falling temperature of the quenching oil leaving the apparatus through the quenching oil return line 42 actuates the thermostat 4| and the damper motor ll connected to this thermostat through the control line .40 to move the fresh air damper lli toward its closed position and the recirculation damper II toward its open position. When this occurs recirculation air from the air discharge duct 20 is drawn, together with thefresh air from the cold air irtake duct 26, through the vertical duct 22 and its horizontal leg 23 into the bottom of the casing 5. Since this recirculation air withdrawn from the air discharge duct 20 has been heated by passing the bank of coils 44 and also is substantially saturated with the moisture evap orated in passing through these flooded coils 44 and thesprays from the nozzles 64, it will be seen that the mixed fresh and recirculated air now supplied to the bottom of the casing has a higher wet bulb temperature and hence the evaporative cooling effect of the water and air passing over the bank of coils 44 is reduced. It will therefore be seen that the immersionthere mostat 4| maintains a constant minimum temperature of the quenching oil returned to the quenching bath by the inverse operationof the recirculation damper 3| and fresh air damper 30, a falling temperature of the quenching oil or other liquid being treated opening the recirculation damperll and closing the cold fresh air damper 30. This modulating control of the dampers 30 and 3| allows the intermediate position ofthese dampers to hold a constant minimum temperature of the quenching oilby the use of recirculated air and tempered cold fresh air.

The recirculation of the necessary amount of airfrom the air discharge duct 20 to the bottom of the casing 5 in so maintaining a' constant minimum temperature of the quenching oil or other liquid being treated also keeps the amount of evaporated'moisture to a minimum. The ar-- rangement of the recirculation damper 3| in the air discharge duct 20 also serves to reduce the amount of air exhausted through the outlet of the discharge duct 20 with an increase in the amount of recirculated air returned to the bottom of the casing 5.

The primary purpose of the immersion ther mostat it in the spray water tank 8 is to keep the water temperature above a predetermined In the event that the temperature of the quenching oil drops below that required for properly tempering the steel, as at the start of operation or in an extended period between tempering operations, the immersion thermostat 4! is actuated by the lowering temperature of the water I in the tank} to open the steam valve 48 and admit steam to the steam coils 45. This thermostat 49 serves to maintain a constant min- 1 Under imum temperature of the spray water. these conditions, the immersion thermostat 4| has moved the fresh air damper 30 to its fully closed position and the recirculation damper ii to its fully opened position and hence the air heated by the steam coils is continuously recirculated by the fan wheels l4, through the air discharge duct 20, recirculation duct 2|. vertical duct 22, and horizontal leg 23 to the bottom of the casing 5, this air moving upwardly through the bank of coils 44 carrying the quenching oil or other liquid being treated so as to heat the same. Since this recirculating air is. saturated with moisture, there is no evaporative cooling effect and hence the quenching oil passing through the bank of coils 44 is heated so as to keep the bath of quenching oil at the desired minimum temperature under all conditions of operation.

If the cooling coils 44 which carry the quenching oil become waxed up internally due to the deposit of lard oil in the form of a wax therein,

the heat exchanger can be manually adjusted to operate'in the same way as when the quenching oil is below the set temperature as Just described. Thus, to dewax the cooling coil 44,

the fresh air damper ill is held closed, the recirculated air damper is held open and steam, under control of the manual switch 53, is admitted to the steam coil 45. The air being recirculated through the casing 5 is thereby heated so as to melt the wax in the cooling coils 44, this wax being carried away with the quenching ofl.

While the invention has been described particularly in conjunction with the cooling of quenching oils, it will be understood that it is not limited to this particular use but may be used in conjunction with any fluid to be treated as indicated in the accompanying claims. While the invention has also been illustrated as embodied in an evaporative type of heat exchanger, the use of the spray water for evaporative cool ing is not an essential feature of the invention in its broader aspect.

minimum. With quenching oils, this minimum is in the range of 50 to F., and by keeping the spray water at this minimum temperature, the minimum amount of lard oil will be deposited out in the cooling coils 44. By setting the ther- .mostat 49 to maintain, through the'steam coils 45, this minimum temperature of the spray water, the deposit of wax in the coils 44 is reduced toa minimum since it has been ascertained that at temperatures above 55 F. practically no lard oil will deposit out of quenching oils. Other means could, of course, be provided for so maintaining the minimum temperature of the spray water and the maintenance of this minimum temperature could, of course, be made responsive to the leaving temperature of the quenching oil, as through the thermostat 4 i I It will be-seen, so far as the control of the proportions of fresh and recirculated air ad- 'mitted to the casing 5 is concerned, that an important feature ofthe invention resides in this control being responsive to' the temperature of the liquid being cooled. It will also be apparent that this control can be accomplished directly, as by the immersion thermostat shown, or indirectly, as by response to a temperature which varies in substantial proportion to the temperature of the liquid being cooled. The claims are therefore not to be construed as specifically limited to the use of the immersion thermostat 4| but as including control means which are indirectly responsive to the temperature of the quenching oil or other liquid being cooed.

From the foregoing it will be seen that the present invention provides a simple and emcient apparatus for maintaining the desired temperature of a fluid within very close limits; which has a high cooling capacity with a minimum consumption of cooling water, and which will prevent the liquid beingv treated from droppingbelow the desired minimum temperature. Further, when the cooling surfaces become waxed up due to the deposit of any material, such as lard oil, on the cooling surface, this surface can quickly and easily be dewaxed.

We claim as our invention; g 1.. A heat exchange device for cooling a stream of fluid, comprising means forming a chamber having an air inlet at one end and an air outlet at its opposite end, a fan arranged to force a stream of air from saidinlet, through said chainher and out through said outlet, a cooling coil arranged in the stream of air passing through said chamber, means for discharging and distributing water over said cooling coil to wetthe exterior of a part ofthe stream ofair leaving said chamber back to said air'inlet, and means for adjusting the'relative amounts of outside. and recirculated said cooling coil and to evaporate and absorb heat therefrom, means for continuously conduct-' ing the said stream of fluid to be cooled through said cooling coil, a duct for conducting-outside air to said air. inlet, a recirculation duct conducting a part of the stream of air leaving said chamber back to said air inlet and means for adjusting the relative amounts of outside and recirculated air admitted to said air inlet to maintain a minimum surface temperature of said cooling coil comprising damper means in the currents of outside and recirculated air passing through said outside air and recirculated air ducts and movable to restrict'the flow of one of said currents of air and to relieve the restriction to the flow of the other of said currents of air and vice versa and .a thermostat responsive to the temperature ofsaid stream of fluid and regulating said dampers.

2. A heat exchange device for cooling a stream of fluid, comprising means forming a chamber having an air inlet and an air outlet, a fan arranged to force a stream of air from said inlet, through said chamber and out through said outlet, a cooling coil arranged in the stream of air passing through said chamber, means fordischarging and distributing water over said cooling coil to wet the exterior of said cooling' yil and to evaporat and absorb heat therefrom, means for continuously conducting the said stream of fluid to be cooled through said cooling coil, means for conducting outside air to said air inlet, recirculation means for conducting a part of the stream of air leaving said chamber back to said air inlet and thermostat means responsive to the temperature of said stream of fluid and adjusting the amount of air so conducted back by said re-- circulation means to maintain a minimum surface temperature of said cooling coil.

3. A heat exchange device for maintaining a fluid in a selected temperature range determined by the character of the fluid by cooling a stream of said fluid and preventing the temperature ,thereof from falling below said temperature range, comprising means forming a chamber having an air inlet at one end connecting with the outside air and an air outlet at its opposite end, a fan arranged to force a stream of air from said inlet, through said chamber and out through said outlet, a cooling coil arranged in the stream of air passing through said chamber,

means for discharging and distributing a stream air admitted to said air inlet to: prevent the tem-v peratureof said fluid in said cooling coil from falling below said temperature range, comprising damper means in the currents of outside and re-' circulated air passingthrough said outside and recirculated air ducts and movable to restrict the flow of one of said currents of air and torelieve the restriction to the flow of the other of said currents of air and vice versa and thermostat means responsive to the temperature atom of said streams and regulating said dampers. v

4. A heat exchange device for maintaining a fluid in a selected temperature range determined by the character of the fluid by cooling a stream of said fluid and preventing the temperature thereof from falling below said temperature range, comprising means forming. a chamber having an air inlet and an air outlet, a fan arranged to force a stream of air from said inlet, through said chamber and out through said outlet, a cooling coil arranged in the stream of air passing through said chamber, means fortherefrom; means for continuously conducting part of the stream of air leaving said chamber back to said air inlet, and thermostat means 'responsive to the temperature of one of said streams to adjust the amount of air so conducted back by said"recirculation means to prevent the temperature of said fluid in said cooling coil from. falling below said temperature range.

5. A heat exchange device for cooling a stream or fluid, comprising means forming achamber having an air inlet-at one end and an air outlet at its opposite end, a fan arranged to force a stream of air from said inlet, through said chamher and out through said outlet, a cooling coil arranged in the stream of air passing through said chamber, means for continuously conducting the said stream of fluid to be cooled through said cooling coil, a duct for conducting outside air to said air inlet, a recirculation duct conducting a part of the stream of air leaving said chamber back to said air inlet and means for adjusting the relative amounts of outside and recirculated air admitted to said air inlet to maintain a minimum surface temperature of said cooling coil comprising damper means in the currents of outside and recirculated air passing through said outside air and recirculated air ducts and movable torestrict the flow of one of said currents of air and to relieve the restriction to the flow ofthe other of said currents of air and vice versa and a thermostat responsive to the temperature of "said stream of fluid and regulating -said,

dampers.

6. A heat exchange device for cooling a stream of fluid, comprising means forming a chamber back to said air a 22,583 Y i be cooled through said cooling coil, means for conducting outside air to said air inlet, recirculation means for conducting a part of the stream of air leaving said chamber'back to said air inlet and thermostat means responsive to the temperature of said stream of fluid and adjusting the amount of air so conducted back by said recirculation means to maintain a minimum surface temperature of said cooling coil.

' '7. A heat exchange device for maintaining a uid in a selected temperature range determined I y the character of the fluid by cooling a stream at said fluid and preventing the temperature thereiif from falling below said temperature range, comprising means forming a chamber having an air inlet at one end connecting with the outside air and an air outlet at its opposite end, a an arranged to force a stream of air from said inlet, through said chamber and out through said outlet, a cooling coil arranged in the stream of air passing through said chamber, means for continuously conducting the said stream of fluid to be cooled through said cooling coil said stream of air normally being heated through heat derived from said stream of fluid passing through said cooling coil, a recirculation duct conducting a part of the stream of air leaving said chamber the? relative amounts of outside and recirculated -air,admitted to said air inlet to prevent the tem-.

pefialture' of said fluid in said cooling coil from i'alling below said temperature range, comprising damper means inthe currents of outside and recirculated air passing through said outside and recirculated air ducts and movable to restrict the flow of one of said currents of air and to relieve the restriction to the flow of the other or said currents of air and vice versanand thermostat means responsive to the temperature of one of said streams and regulating said damper.

8. A heat exchange device for maintaining a fluid in a selected temperature range determined by the character of the fluid by cooling a stream of said fluid and preventing the temperature inlet, and means for adjusting thereof from falling below said temperature range, comprising means forming a chamber having an air inlet and an air outlet, a fan arranged to force a stream of air from said inlet, through said chamber andout through said outlet, a cooling coil arranged in the stream of air passing through said chamber, means for continuously conducting the said stream of fluid to be cooled through said cooling coil, said stream of air normally being heated through heat derived from said stream of fluid passing through said cooling coil, means forconducting outside air to said air inlet, recirculation means for conducting apart of the stream of air leaving said chamber back to said air inlet, and thermostat means responsive to the temperature of one of said streams to adjust the amount of air so conducted back by said recirculation means to prevent the temperature of said fluid in said cooling coil from falling below said temperature range.

- MARTIN H. OLSTAD.