ENERGY STORAGE AND REMOVAL METHODS FOR RANKINE CYCLE SYSTEMS

1OO1O18 !1 ti il i! l! Background of the Invention Vapor cycle engines, particularly-when used in automotive or similar applications, frequentlY 'have peak loads imposed upon them which are substantially higher than those encountered under ordinary running conditions. In open cycle ! engines, the vapor or working fluid is vented into the atmosli phere after it has performed useful work and no condenser is N j utìlJ.zed in the system. Ilowever, because the fluid is vented i "nnd must be replaced, it is necessary te carry a large'reservoir ]! of working fluid which must be transported by the vehicle being ii drivo2n by the engine.

!),. In closed cycle engines a condenser is used to ¢onvei.'t tho worlçl, ill; f],li:id from vlipoi." to liquid to I)e upped on( o -N l i i I I i I i i I I ]i il J! iJ L' 30:.

ÆoOIOÆ8 more in the cycle of the engine. To cope with the peal< loads, conventional practice is simply to employ a condenser of sufficient capacity to handle those peak loads. In the specific case of automotive applications, the engine moist be capable of accelerating in quick bursts and the power needed for such bursts is much greater than that needed for driving at relatively unchanging speeds. Stated otherwise, the engine must be operable for short periods at power levels far above those considered maximum for sustained operation. In engines of the type with which the present invention is concerned, air-coolant condensers i of capacity great enough to handle the peak load on a sustained basis are conmlonly used. This constitutes a brute force solution I[ to there problem and the extra cooling capacity of the large coni densers is used inefficiently.

. . I The large condenser design is disadvantageous for other reasons. In any automotive vehicle, the permissible engine weight is limited and, also, the amount of space available is limited in size and frequently in configuration.

Moreover, engine efficiency is reduced because parasitic air flow cooling losses increase as condenser size is increased.

Finally, the larger the condenser is, the more expensive it Summary of the Invention becomes.

I I i This ínvention is concerned with vapor cycle li engines suitable for automotive applications. According to I1 iì this invention, the capacity of the engine's primary condenser l ay be reduced below that required for peak power operntion, i !i During high power transients, the heat of the working fluid, in excess of the primary condenser's capacity, is absorbed by a v li l I I I liquid contaí.ned in a secondary cooling system.

i In this manner, ì i l i0 100101 The load imposed on the primary condenser is reduced.

Broadly, one aspect of the present invention may be described as a vapor cycle engine in which working fluid is vaporized in a boiler, fed therefrom to an expander to perform useful work, returned to a condenser to be converted to a liquid and then fed to the boiler to complete a cycle, the improvement which comprises, means for cooling the working fluid converted by the condenser at a given rate continuously at predetermined operating levels of the engine, and means including a heat-absorbing liquid for cooling the working fluid converted by the condenser at a rate higher than the given rate in response to operation of the engine at levels higher than the predetermined levels.

Another aspect of the present invention may be broadly described as a vapor cycle engine in which working fluid is vaporized in a boiler, fed therefrom to an expander to perform useful work, condensed thereto to a liquid, and then fed to the boiler to complete a cycle, a method for condensing the working fluid to a liquid comprising the steps of accepting working fluid from the expander, continually extracting heat from the working fluid in a condenser in a first heat exchange step wherein the maximum rate of heat extraction corresponds to the rate of heat extraction required when the engìne is operating at a predetermined level and rejecting the heat to a gaseous environment, transferring additional heat from the working fluid to a heat-absorbing liquid in a second heat exchange step to augment the extracting step and thereby permit operation of the engine at operating levels above the predetermined operating level, and thereç, after discharging the additional heat to the gaseous environment.

ljr: J ç i0 IOOÆOÆ8 In one embodiment of the secondary cooling system, the working fluid passes through a heat exchanger immersed in a liquid contained in an air cooled thermal storage chamber. This liquid partially cools the working fluid, thus reducing the load imposed on the condenser. The heat absorbed by the liquid is released through the walls of the chamber. Cooling vanes or impingement cooling apparatus are employed to increase the heat rejection rate of the chamber. Due to the fact that heat can be absorbed rapidly by the liquid during high power transients and released at a s!ower rate during lower sustained power operations, the total amount of cooling surface in both the primary condenser and the secondary cooling system is less than that required by a single condenser in a conventional system.

The thermal storage cooling system is compatible with various vapor cycle engine designs. It can be arranged to cool the working fluid before, or after, it passes through the primary condenser, or it can be placed in line with each condenser stage« It can also be designed to operate on demand by means of a simple valving arrangement.

In another embodiment, a liquid is stored in a pressurized tank and is sprayed against the cooling surfaces of the condenser during high power transients to increase the condenser's cooling capacity. It is also possible to combine this system with the thermal storage cooling system to meet a Wide range of design requirements.

The employment of secondary cooling as in this invention in an automotive vapor cycle engine significantly reduces the required size of the engine's primary condenser.

Thus engine weight is reduced, space is conserved and condenser costs are »ç í : ': ljr : 5f - 3al !j , ÆOOîOÆ8 are minimized. Furthermore, engine efficiency is increased because the condenser's parasitic load is reduced.

Brief Description of the Drawings For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description of a preferred embodiment of the invention which should be read mn connection with the accompanying drawings, in which:

Fig. i ms a,mhematic of a valour cycle engine'wí.th i a secondary cooling system, Fig. 2 ms a plan view, in section, of a condenser and its associated secondary cooling system, Fig. 3 xs aæhematic showing of a condenser and its associated secondary cooling system, ' • .0 Fig. 4 zs a plan view, in section, of another form of condenser and its associated secondary cooling system, Fig. 5 ms a schematic representation of he device illustrated is Fig. 4; and, Fig. 6 is a schematic showing of a condenser and - its associated secondary cooling system. í Description of the Prefer :ed embodiment I Referring to Fig. i, working fluid is vaporized I , in a boiler 2 and is then carried by a conduit 4 to an expander I ! 6 where it performs useful work. The fluid, still in a gaseous :

!I.. state, passes from the expander 6, via a conduit 8, into a i I regenerator i0, where it is partially cooled in a heat exchanger 12. The fluid, still in a gaseous state, passes from the í regenerator I0 through a conduit 14 into anothcr heat exchanger 18 ' * í i of a secondary cooling system 19. The heat exhanger 18 is I immersed in a liquid 20, such as water or water mixed with a ' } 'i :i i, i, IOOÆOÆ8 .2o Il non-volatile anti-freeze contained in an air cooled thermal ]í storage chamber 16. The liquid 20 absorbs heat from the fluid provîded with a pressure release valve 22 and an impingement heat transfer mechanism 40. The workíng fluíd passes from the ]1 chamber 16 via a-conduit 24 into a primary condenser 26. After l[ being recondensed, the fluid passes through a conduit 30 into a fo J pump 32. From there it is pmnped throush a conduit 34 into the , ,, regenerator i0 where it passes through another heat exchanger 36 IO and absorbs the heat rejected by the heat exchanger 12". In this ii preheated state it passes through a conduit 38 into the boiler ' I 2, thus the completing cycle.

li During steady state operation at or below a given ii maximum sustained power level, the liquid 20 reaches an ,. equilibrium temperature at which thë rate of heat absorption i i from the heat exchanger 18 equals the rate of heat rejection " through the walls 17 of the chamber 16. The air flow over both t! the chamber 16 and the primary condenser 26 is normally generated i by a fan and the pressure differential created by vehícle motíon.

- The rate of heat rejectíon through the vails 17 can be improved, and the equilíbrium temperature of líquid 20 lowered, by .inereas-; if ii ing the surface area of walls 17, or preferably, by providing air I impingement nozzles 40 on the upstream side of the chamber 16. J i! The condenser 26 and the chamber 16 are designed to meet: the i, ,t I cooling requirements of the engine during continuous operation !I at tl e given maximum power level for sustained operation..

i, ,i During each power transient in excess of the engine s , steady state cooling capacity, more heat is produced thán can be 6 I immediately rejected. The secondary cooling system 19 is pro- . vided with a sufficient volume of the liquid 20 to absorb and .J !i.

ed I I t i ÆOOÆOÆ8 I thermally store this excels thermal energy. The heat exchanger '°il 18 is designed to insure that all of this excess energy is and the necessity of carrying a reserve, a sufficient liquid volume must be contained in the chamber 16 to i1 isure that its overall temperature does not reach theboiling point of the liquid. For example, assuming an average overall engine efficiency of 15%, and a 15 second peak power requirement of approxi I transferred to the liquid 20. To avoid dissipation oç the liquidI t I t i I J.mately 50 horsepower above the vehícle m xìmum sustained power" i requirement, the liquid 20 must be capable of absorbing an extra ì 3,000 BTUs of heat energy, approximately. The minimum amount of i water required by the secondary cooling system 19, in this case, 1 I would be approximately 9 gallons, assuming a 40°F. temperature ì I rise available in its sensible heating range at the worst design ! . conditíons, However, íf reductíon of the size of the chamber 16 il is essential, the latent heat capacity of liquid 20 can also be • l! brought, into play "1 " '" The heat absorbed by the liquid 20 during high i power transients is rejected through the walls 17 of the chamber ! 16 during the longer periods of lower power operation. In other 1 i words, transient high heat can be rapidly absorbed by the secondary coolíng system 19 and slowly rejectedduríng the more quiescent and generally longer intervals between high power transients. Ilence, ! ií the cooling capacity of the primary condenser 26 i Substantially" lí !! less than that which would be required in a single condenser I i ii ' operatíng alone. Furthermore, the necessary cooling surface area', ìl 26 and the thermal storage cooling system 19 combined is legs i ;i than that required by a single condenser operating alonè. í I I!. As shown in Fig. 1, the chamber 16 and the condenser 3o1i 26 are at approximately the same level. If the secondary cooling i ,i í J' I :: » I s J! -6I i 1O01018 S system 19 totally recondenses the working fluid and this is not desired, such ,aay be avoíded as shown in Figs. 4 and s.. Here, the working f1 uid enters a first stage 21 of the condenser 26 via conduit 14. After passing through that stage of the condenser, it enters a cooling system stage. From thé cooling I[ system, it flows through a subsequent stage 23 of the condenser.

il The condenser 26 and cooling system 19 may be .constructed .se that il this sequence occurs once (e.g., by flow through parallel.

!! passages in each stage) or repetitively (e.g., by flow through a pluraltiy of alternating condenser and cooling system stages), i i :0 i .

Although it is desirable to have as few valves as possible in a vapor cycle engine, "the employment of valves 42 I !! and 48 as sho,,'n in ìig . to switch in the secondary coing system reduces the amount• of heat absorbing liquìd needed ín the secondary ..!:, cooling system 19 because the equflibrium temperature of the liquïd t! zo may be lower. In this system, the valve 42 normally directs i the working fluìd through a conduit 44 directly into tl e condense " 26.. When the engine is operating at power levels in excess of the condenser capacity, th'e valves 42 and 48 are opened to admi.t all t I Iii; or part of thè working fluid flow into the secondary cooling I !I Il system, thus reducing the load that would otherwise be imposed I ti on the condenser.

ml .

i! I n a o teller embody linear, no shown, the.secondary 1 ll: cooling system is located directly in line with the condenser 26,I ! bu't the working fluid first passes through the condenser 26.

1 there again, the equilibríum temperature of the heat absorbing í ; liquid 20 is lower and a smaller amount of the heat absorbing i i liquid is required by the secondary cooling system 19. tlowever, :

i" J '1 I ;: since the working fluid, within the coil 18 may .be already con1 ': densed, a greater amount of working fluid is carried by the engine '1 il ÆOOîOÆ8 i,ì than is otherwise required' i,t . Referring to Fíg. 6, another embodiment of this i i.. invention ìs illustrated, ttere again, the condenser 26 ís sízedI, for the maximum sustained power demands of the system, but the I working fluid if not diverted through any secondary cooling system.

Instead, a presstirized tank 54 of heat absorbing liquid, water I i for example, is associated with the condenser. When the engine Il is operating at power levels in excess of the condenser capacity, i i' s control 52 is actuated. The control 52 open a valve IO I! allowing the heat absorbing liquid to pass through the conduits í Ji 56 and 58 and be emitted as a spray 62. The spray 62 impinges ., 26 ! • upon the condenser/where it is vaporized and significantly inI i creases the cooling capacity of the condenser.. Ideally, because I the heat absorbing fluid vaporizes on contact with the c0 nde1 ser i ,, coil, the latent heat of the heat absorbing liquid contributes i, greatly to cooling efficiency. A combination of the spray system i ì 0 ! I! and any of the other embodiments described above may be utilized I[ to meet a wide range of design conditions.

I| !! In all of the above embodiments, the total amount o O!i cooling surface required by the vapor cycle engine is less than l s: that required by earlier designs. Thus the engine's parasitic !i cooling load is reduced and its efficiency increased. Clearly, !i also, the invention significantly reduces the required cooling "i ì! capacity of a condenser in a variable power vapor cycle engine. I Accordingly, great savings in space, weight and engine cost are i t I achieved As a resuit, closed cycle vaç0r engines which are almost i; pollution-free may be realistically considered for automotive i ii applications.

Since certain changes may be made in the above _30 1: constructions without departing from the scope of the invention, ,i J, ,i l t ,i IL J i +4 t4 t' 'i It I' I' l i !i fs il I I it is intended that ai1 allotter contained in theabove description or shown in the accompanying drawings shall be interpreted as illustrative and not interpreted in a limiting sense.

What is claimed is:

P l I i i i I i t t J 1001018 .

I[ HE EMBODIMENT,S OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

li ' I ' 2. ,The" ímprovement described in claim 1 wher'eín said Il means for cooling at a higher rate said working fluid converted " {i by said condenser comprises an air cooled thermal storage chamber ' t for containing heat-absorbing fluid, first heat transfer means communicating wíth said condenser, said heat transfer means beingI • i at least partially immersed in said heat-absorbing fluid, means » for passing saíd workíng fluíd through said heat transfer means i a !I chamber; and second heat transfer means externally mounted on said lì chamber.

!I ' 3. The improvement described in claim 2 wherein i il said first heat transfer means is interposed between said i ,! expander and said condenser.

it Ii 4. The improvement described in claim 2 wherein • , said first heat transfer means is interposed between said conl! I '" denser and saíd boíler.

ol I. In a vapor cycle engine in which working fluid is vaporized in a boiler, fed therefrom to an expander to perfrom useful work, returned to a condenser to be converted to a liquid and then fed to said boiler to complete a cycle, the improvement which comprises, means for cooling the working fluid converted by said condenser at a given rate continuously at predetermined operating levels of said engine, and means including a heatabsorbing ].iquid for cooling said working fluid converted by said condenser at a rate higher than said given rate in response to operation of said engine at levels higher than said predetermined levels.

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