US3231013A

US3231013A - Controlling the heat exchangers of air condensation apparatus

Info

Publication number: US3231013A
Application number: US85339A
Authority: US
Inventors: Heller Laszlo; Bodas Janos
Original assignee: Licencia Talalmanyokat Ertekesito Vallalat
Current assignee: Licencia Talalmanyokat Ertekesito Vallalat
Priority date: 1961-01-27
Filing date: 1961-01-27
Publication date: 1966-01-25
Anticipated expiration: 1983-01-25

Description

Jan. 25, 1966 I L. HELLER ETAL 3,231,013

CONTROLLING THE HEAT EXCHANGERS OF AIR GONDENSATION APPARATUS Filed Jan. 27. 1961 4 Sheets-Sheet 1 F/g. Z

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By 1mm: 300/23 fa MW DTTORIVEYJ Jan. 25, 1966 HELLER ETAL CONTROLLING THE HEAT EXCHANGERS OF AIR CONDENSATION APPARATUS 4 Sheets-Sheet 2 Filed Jan. 27 1961 INVENTORS Z A921. 0 HELLER, l IJ'ZM I U/Q60 BY ,1 mm: 600/); flfiarv, 224 I r l fiTTOR/VEKS Jan. 25, 1966 L. HELLER ETAL 3,231,013

CONTROLLING THE HEAT EXCHANGERS OF AIR CONDENSATION APPARATUS Filed Jan. 27. 1961 4 Sheets-Sheet 5 INVENTORS M32 L0 HEZLER, mszm mean BY Jma: .3000;

r M W Jan. 25, 1966 L. HELLER ETAL 3,231,013

CONTROLLING THE HEAT EXCHANGERS OF AIR CONDENSATION APPARATUS Filed Jan. 27, 1961 4 Sheets-Sheet 4.

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United States Tatent C 3,231,013 CONTROLLING THE HEAT EXCHANGERS OF AIR CONDENSATION APPARATUS Laszl Heller, Laszl Forg, and Janos Bdas, Budapest,

Hungary, assignors to Licencia Talalmanyokat Ertekesito Vallalat, Budapest, Hungary Filed Jan. 27, 1961, Ser. No. 85,339 4 Claims. (Cl. 165-97) This invention relates to controlling the heat exchangers of air condensation apparatus.

As is known, in the so-called air condensation apparatus of power plants the exhaust steam of turbines is condensed indirectly by means of atmospheric air. Such apparatus are used on sites where no suificient quantities of cooling water is at disposal. Their characteristic feature is that they operate without any loss of water, due to the Water serving for cooling purposes being circulated in a closed system. Condensation of the exhausted steam of the steam turbine is effected in a jet condenser by cooling water, naturally with the result of the coolant being warmed-up. The hot cooling water is Withdrawn from the condenser by means of a circulating pump and supplied into a heat exchanger apparatus of large surface swept by a stream of atmospheric air. In such heat exchanger apparatus the cooling water is cooled down whcreafter it is returned into the jet condenser for being mixed with exhaust steam as before.

The cooling output of the heat exchangers of such apparatus is to be calculated so as to enable it to cool down the cooling Water to an extent which is necessary for an economic operation of the steam turbine even if the latter is under maximum load and, consequently, a maxi- ;mum amount of steam has to be condensed and, at the same time, the temperature of the atmospheric air reaches its upper limit.

Thus, the output of the heat exchanger apparatus is too great Whenever the amount of steam introduced into thejet condenser is less than the maximum value or else the temperature of the atmospheric air is inferior to the maximum temperature value taken as basis of dimensioning. In such cases, the cooling water would excessively pheric air is below freezing point.

I At present, two methods are known for controlling the thermal output of heat exchanger apparatus associated with air condensation systems. One of these methods consists in that the amount of cooling water circulated across heat exchanger elements is decreased whereby,

however, the heat transfer coefiicient of the heat exchanger apparatus and the mean temperature difference between air and water diminish so that also the thermal output of the heat exchanger apparatus decreases. However, by means of such type of control the temperature of the cooling water withdrawing from the heat exchanger constantly decreases with the diminishing amount thereof sothat such a control may be applied only until the temperature of the cooling water withdrawing from the heat exchanger apparatus approaches the freezing point.

According to the other method suitable for controlling the output of heat exchanger apparatus of air condensa- .tion systems a part of the heat exchanger apparatus is disconnected with the circulation of the cooling water in which case the dicsonnected heat exchangers do not ex- Such system of control is, principally, capable to alter the output of the heat exchanger apparatus within any limits. However, an economic establishment of heat exchanger apparatus requires the number of disconnectable parts to be restricted to a minimum. Viz., each individually disconnectable heat exchanger part requires a great number of expensive armatures or fittings associated with it so that an excessively great number of heat exchanger parts entail a considerable increase in investment costs. Apart from such surplus expenses the aforesaid method of control unnecessarily increases the number of fillings which being delicate operations are undesirable. Namely, if in the course of filling subsequent to a previous emptying air remains in one of the heat exchanger passages, it prevents there the setting-in of circulation of the cooling water with the result of a freezing-in of the respective heat exchanger element.

Neither a simultaneous application of both aforesaid control methods gives the possibility of adjusting the temperature of the water withdrawing from the heat exchanger apparatus to an actually required optimum value at any quantities of steam to be condensed and at any temperatures of atmospheric air.

The main object of the present invention is to propose a new apparatus for the control of the thermal output of heat exchanger apparatus the use of such control with known devices permitting the temperature of the cooling water supplied by the heat exchanger apparatus to al-- ways correspond to the desired optimum value.

The new control method according to the invention is based on the idea of the possibility of running two-way cross-flow heat exchanger apparatus in cross counterflow connection as well as in cross parallel flow connection, respectively.

As is known, heat exchangers used with air condensation systems are built up of a plurality of heat exchanger elements each of which receives the cooling water at its bottom portion and conducts it through a group of finned parallel tubes to a top portion. Here, a return chamber serves for reversing the flow direction of the cooling water which flows through a second group of tubes of the heat exchanger again to the bottom portion thereof where it withdraws through an outlet stub. In both groups of tubes or heat exchanger sections the air flow is of the cross-flow types.

In case of such heat exchanger elements, the connection is labelled as cross parallel flow if the admitted cooling water contacts fresh air in the first one of the aforesaid groups of tubes or heat exchanger sections whereas in the second one it is the cooling water already cooled down and the warmed-up air which contact each other in a cross-flow type heat exchange (FIG. 1).

Cross counterflow connection consists in an arrangeent wherein the cooling water introduced into the heat exchanger element first contacts air already warmed-up in the second section or group of tubes, a contact with fresh air taking place in the latter (FIG. 2).

Furthermore, it is known that the thermal performance of heat exchangers is less in cross parallel fiow connection than in cross counterflow connection under otherwise identical conditions.

Such variety of possible heat exchanges oifers a further possibility of adjusting the output of heat exchangers used with air condensation systems. Viz., besides both aforesaid methods of adjusting the thermal output also use is made of wholly or partly switching over a heat exchanger apparatus from cross counterfiow to cross parallel fiotw type of connection.

The heat exchanger elements have to be constructed so as to discharge the water immediately upon stopping of its circulation. Namely, if circulation of the cooling water is stopped in the heat exchangers because of stopping of its circulating pump and the temperature of the cooling air happens to be below the zero point, the cooling water quickly freezes in the tubes of the heat exchangers which will be destroyed thereby. Therefore, it is important that the cooling water be automatically drained oif immediately upon stopping of the circulatin'g pump of the heat exchanger apparatus. Obviously, the means serving for the aforesaid switching-over must not prevent an automatic drainage of the respective heat exchanger element and of the piping associated therewith.

A further requirement in connection with heat exchangers of air condensation systems is that the pressure of water therein be anywhere superior to the atmospheric pressure since this is the only way to warrant that no air enter the heat exchanger at probably defective places. Moreover, such places should immediatelybe indicated by water spouting therefrom. Thus, a further object of the invention consists in the provision of a switching-over apparatus which prevents the pressure of the cooling water to drop below the atmospheric pressure anywhere in the heat exchanger apparatus.

Finally, it is required with heat exchangers of the above described type that any switching-over thereof be quickly feasible so that circulation of the cooling water be interrupted only for a time period of at most one to two minutes.

The invention will hereinafter be described in closer details by taking reference to the annexed drawings FIG. 3 of which shows, by way of example, an embodiment of a heat exchanger apparatus according to the invention capable of being switched over from cross counterfiow to cross parallel flow connection and vice versa, FIGS. 1 and 2 illustrating the already explained principles of such connections.

FIG. 4 shows an embodiment of the invention for operating a plurality of heat exchange elements. FIG. 5 is a schematic diagram of a hydraulic system for switch over of the heat exchange apparatus of the invention.

FIG. 3 shows an element of a heat exchanger suitable for air condensation systems referred to above. It consists of a pair of groups of tubes or

sections

13 and 14 serving for cooling down a coolant, i.e., water introduced via a" supply pipe conduit 2 and returned to a not-represented jet condenser of the system via a return pipe conduit 3. Cooling down of the water is effected by atmospheric air flowing, in the instant case, in the direction of arrows '1. The top portion of the represented heat exchanger element is formed by a return chamber 5 whereas at the bottom portion thereof an inlet stub 4 and an outlet stub 6 for introducing and withdrawing, respectively, of the cooling water are provided. In operation of the heat exchanger element in a cross counterfiow type of contact between cooling water and air the former flows from the pipe conduit 2 through the stub 6 and section '14 of the heat exchanger into the return chamber 5 which purpose various valve means such as gate valves or sluices are provided. Viz., stub 4 is connected to pipe conduits 2 and 3 by means of valves 7 and 8, whereas stub 6 communicates with both pipe conduits 2 and 3 through valves and 9, respectively.

A tank 15, serving for storing the water drained olf from the heat exchanger element, is connected to the conduits of the cooling water by

pipe conduits

16 and 17 upstream the valves 8 and 10, respectively. The

pipe conduits

16 and 17 comprise

valves

18 and 19, respectively.

Switching-over of the above described apparatus from cross counterflow connection to cross parallel flow connection is carried out in the following manner:

As has been shown, in case of cross counterflow operation, the cooling water is introduced into the heat exchanger element through valve 10 and. stub 6 whereas it withdraws therefrom through stub and valve 7, valves 8 and 9 as well as valves 18 andj 19 then being closed. In order to switch over first valve 7 is to be closed whereafter valve 8 maybe opened. This sequence of handling the valves prevents the pressure in the cooling element to drop below the normal operating pressure during switching-over. Then, valve 10 is closed and finally valve 9 opened whereby switchin -over to cross parallel flow connection has been carried out. In this case, the cooling water flows from pipe conduits 2 through valve 8 and stub 4 first into heat exchanger section 13 and theninto heat exchanger section 14 wherefr om it withdraws through stub 6 and valve 9 into the'return pipe conduit 3.

Valves

7 and 10 as well as

valves

18 and 19 are now closed.

Switching over from cross parallel flow connection to cross counterflow connection, that is, from a lower heat out-put to a higher thermal output is eifected by'closing valve 9 and opening valve 10. Then, valve 8 is closed whereupon valve 7 is opened.

FIG. 4 shows an exemplified embodiment of the invention wherein the group of valves=7, 8, 9 and 10 as well as of the valve means 15, 16, 17, 18, 19 serve for operating a plurality of heat exchanger elements rather than one of them, such elements being arranged in parallel connection by means of

pipe conduits

22 and 23, the stubs 4 being connected to pipe conduit 22whereas the stubs 6 are connected to pipe conduit 23. The means serving to switch over and drain oil are likewise connectedto the pipe conduits 22 and 2-3. In the instant case, by switching over the

groupof valves

7, 8, 9 and It) in the manner described in connection wit-h FIG. 3 all heat exchanger elements connected to the pipe conduits 2 2 and 23 are switch over from one type of operation to the other type thereof. i I

In FIG. 5, a structure is shown wherein the switchover is effected by hydraulic means. In this embodiment,

valves

7, 8, 9 and' 10 correspond to the valves of FIG. 3, and the heat exchanger element is not shown. The valves are illust'ratively shown in the condition in which valves 8 and 9 are closed and valves 7 and '10 are open (cross counterflow condition).

A supply of oil is maintained in reservoir 34 and is pumped under pressure by pump 33 from reservoir 34 through change-over valve 31 to work cylinder 35 on the right or left of piston 35a, depending upon the p0sition of valve 31. In the-illustrated position of switch 32, the high pressure oil enters cylinder on the right of piston 35a and drives cam member 36 coupled to piston 35a to the left (arrow 38'). Cam member 36 is shown at the beginning of its stroke to the left.

Cam member 36

controls slide valves

37a, 37b, 37c and 37d which respectively control

valves

7, 8, 9 and 10. In the illustrated right position of cam member 36,

the pistons of slide valves 37b and 37d are depressed and the pistons of slide valves 37a and 370 are elevated. In the left position of cam member 36, the positions of the slide valves are reversed.

. The oil from pump 33 is also led through branch lines through the casings of the slide valves and back to' reservoir 34. The casings are connected by further branch lines to the casings of

valves

7, 8, 9 and 10. In the illustrated arrangement, the oil flow is such as to maintain valves 8 and 9 closed and

valves

7 and 10 open. It will the apparent that the various air flow circuits are reversed when member 36 is moved to the left so as to open valves 8 and 9 and

close valves

7 and 10.

When valve 32' is moved to position 31, the valves are restored to their illustrated condition.

It will be further noted that the cams on member 36 are positioned so that on movement of member 36 to the left, the sequence of valve openings and closings is as follows: initially, valves 8 and 9 are closed and

valves

7 and 10 are open. Then valve 7 is closed. Next valve 10 is closed. Finally, valve 9 is opened. On reverse movement of member 36, the desired sequence of valve operations will also be obtained.

What we claim is:

1. In a heat exchanger for cooling water with atmospheric air, a pair of heat exchanger sections through which water to be cooled is adapted to flow, said sections being arranged beside each other with one of said sections in advance of the other with respect to the direction of air flow so that said one section is contacted by atmospheric air before the other section, said heat exchanger sections respectively having adjacent each other a pair of communicating ends through which said heat exchanger sections communicate directly with each other, and said heat exchanger sections also having adjacent each other a pair of non-communicating ends opposed to said communicating ends, respectively, a pair of tubular stubs respectively communicating with said non-communicating ends of said heat exchanger sections, a supply conduit for supplying warm water to be cooled, a return conduit for withdrawing cooled water from the heat exchanger sections, a pair of inlet valves both communicating with said supply conduit and respectively communicating with said tubular stubs, and a pair of discharge valves both communicating with said return conduit and respectively communicating with said tubular stubs, whereby said valves may be moved between open and closed positions providing a flow of water from said supply conduit first through said one heat exchanger section and then through said other heat exchanger section, to provide a cross parallel flow, or first through said other heat exchanger section and then through said one heat exchanger section to provide a cross counterflow in order to increase the thermal performance as compared to the thermal performance during cross parallel flow.

2. In a heat exchanger as recited in claim 1, a pair of discharge conduits respectively communicating with said tubular stubs, and a pair of additional valves respectively connected operatively to said pair of discharge conduits for maintaining them closed during normal operation of said heat exchanger sections, said additional valves when open quickly discharging both of said sections through said discharge conduits.

3. In a heat exchanger as recited in claim 1, said sections together with said tubular stubs and valves forming a unit which is connected to said supply and return conduits with all of said valves branching from said supply and return conduits and with said supply and return conduits extending uninterruptedly past said unit so that a plurality of units may be served by said supply and return conduits even if all of said valves are closed to take said unit out of operation.

4. In a heat exchanger as recited in claim 1, means cooperating with said valves for opening an inlet valve connected to one stub and a discharge valve connected to the other stub while closing the other two valves, said latter means first closing a previously opened discharge valve, then opening a previously closed inlet valve, then closing a previously open inlet valve, and finally opening a previously closed discharge valve in order to change the direction of flow of water through said heat exchanger sections.

References Cited by the Examiner UNITED STATES PATENTS 2,844,319 7/1958 McGrath 236-1 3,008,695 11/1961 Van Melle 50 FOREIGN PATENTS 809,510 2/1959 Great Britain.

ROBERT A. OLEARY, Primary Examiner.

HERBERT L. MARTIN, CHARLES SUKALO,

Examiners.

Claims

1. IN A HEAT EXCHANGER FOR COOLING WATER WITH ATMOSPHERIC AIR, A PAIR OF HEAT EXCHANGER SECTIONS THROUGH WHICH WATER TO BE COOLED IS ADAPTED TO FLOW, SAID SECTIONS BEING ARRANGED BESIDE EACH OTHER WITH ONE OF SAID SECTIONS IN ADVANCE OF THE OTHER WITH RESPECT TO THE DIRECTION OF AIR FLOW SO THAT SAID ONE SECTION IS CONTACTED BY ATMOSPHERIC AIR BEFORE THE OTHER SECTION, SAID HEAT EXCHANGER SECTIONS RESPECTIVELY HAVING ADJACENT EACH OTHER A PAIR OF COMMUNICATING ENDS THROUGH WHICH SAID HEAT EXCHANGER SECTIONS COMMUNICATE DIRECTLY WITH EACH OTHER, AND SAID HEAT EXCHANGER SECTIONS ALSO HAVING ADJACENT EACH OTHER A PAIR OF NON-COMMUNICATING ENDS OPPOSED TO SAID COMMUNICATING ENDS, RESPECTIVELY, A PAIR OF TUBULAR STUBS RESPECTIVELY COMMUNICATING WITH SAID NON-COMMUNICATING ENDS OF SAID HEAT EXCHANGER SECTIONS, A SUPPLY CONDUIT FOR SUPPLYING WARM WATER TO BE COOLED, A RETURN CONDUIT FOR WITHDRAWING COOLED WATER FROM THE HEAT EXCHANGER SECTIONS A PAIR OF INLET VALVES BOTH COMMUNICATING WITH SAID SUPPLY CONDUIT AND RESPECTIVELY COMMUNICATING WITH SAID TUBULAR STUBS, AND A PAIR OF DISCHARGE VALVES BOTH COMMUNICATING WITH SAID RETURN CONDUIT AND RESPECTIVELY COMMUNICATING WITH SAID TUBULAR STUBS, WHEREBY SAID VALVES MAY BE MOVED BETWEEN OPEN AND CLOSED POSITIONS PROVIDING A FLOW OF WATER FROM SAID SUPPLY CONDUIT FIRST THROUGH SAID ONE HEAT EXCHANGER SECTION AND THEN THROUGH SAID OTHER HEAD EXCHANGER SECTION, TO PROVIDE A CROSS PARALLEL FLOW, OR FIRST THROUGH SAID OTHER HEAD EXCHANGER SECTION AND THEN THROUGH SAID ONE HEAT EXCHANGER SECTION TO PROVIDE A CROSS COUNTERFLOW IN ORDER TO INCREASE THE THERMAL PERFORMANCE AS COMPARED TO THE THERMAL PERFORMANCE DURING CROSS PARALLEL FLOW.