Патент USA US2136114код для вставки
Nov. s, 1938. A. A. MARKSON . 2,136,114 CONTROL SYSTEM FOR STEAM REFRIGERATING SYSTEMS Filed Feb. ll, 1955 INVENTOR W 2,136,114 ~ Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE ` 2,136,114 CONTROL SYSTEM FOR STEAM REFRIGER ATING SYSTEMS Alfred A. Markson, Kew Gardens, N. Y., assignor to John M. Hopwood, Dormont, Pa. Application February 11, 1935, Serial No. 6,053 5 Claims. (C'l. (i2-_152) _ This invention relates to refrigerating systems of the type in which the refrigerant or the ma terial to be cooled, for example water, is cooled in a'. tank which is maintained under partial vacuum‘by means of a steam actuated vacuum >device such asa venturi or evactor, and more particularly to a control system for maintaining the proper relationship between the steam pres sure and the pressure in the flash tank or 1° evaporator and a condenser into which steam, Aair, and water vapor are discharged. In refrigerating systems of this type, whether they be used for air conditioning or for pro viding a supply of cool water for oflice buildings, 'l5 and the like, the water being cooled which, for convenience will be called refrigerant herein, is delivered from a source of _supply into a flash tank or vacuum chamber in which it is cooled and from which the cooled water is‘circulated V$50 to Wherever needed. A booster or steam jet com pressor venturi or evactor type is connected to the flash tank and to a water cooled condenser and a supply of steam is provided which when passed through the booster at high velocity picks 25 up'vapor which is evaporated in the flash tank, compresses and transfers it to the condenser. As' the vacuum increases the boiling point of the water is lowered, so that some of the water is the flash tank to the condenser, while the dif ferential would tend to increase because of the increased load on the condenser. ' Ifgtherefore, the steam pressure at the nozzles is regulated or controlled to bear a deñnite'rela tionship to the differential between the flash tank and condenser pressures, decided economies in the amount of steam and condenser cooling water employed may be realized. An object of this invention is the provision of a regulating systemv which‘will respond to changes in the difference between the flash tank and condenser pressure, hereinafter called the pres sure differential, and so control the pressure. of ‘the steam at the'nozzles tha‘t a deûnite rela tionship is maintained between the nozzle steam pressure and said pressure differential. Another object is the provision of a regulating system which will respond to changes or varia-I tions in a given pressure differential to control 20 the pressure of the steam at the nozzles in such fashion as to maintain a definite relation ship between the nozzle steam pressure and the pressure differential regardless of the number of .` 25 boosters or nozzles that may be operating. Other objects of the invention will, in part, be apparent and will, in part, be obvious from the following description taken in conjunction with vaporized by the heat of the liquid, whereby the the accompanying drawing, in which: ` cooler the temperature of the liquid will be. For a control system embodying one form of the invention, parts of the apparatus of the sys Figure l is a more or less diagrammatic view temperature of the remaining liquid is released. of a steaní refrigerating system provided with -The higher the vacuum in the iiash tank the example, if the pressure in the flash tank is re duced to a value say 0.2575 inch of mercury ab tems being shown insection; "eo ‘ Fig. 2 is a. fragmentary view in section of a 35 35 solute pressure, the temperature of the water'inv f portionof a regulator embodied in the control the tank will be about 41° F. »I In systems of this type, one or more boosters or steam jet compressors are employed and are con nected in multiple to a steam supply header. 'I‘he y number of boosters employed at any `one time is dependent upon the refrigerating load. Each booster- or compressor may include one or a group of nozzles, and the steam in passing through them is converted from pressure head . into velocity head which is high enough to over come the back pressure in the condenser and to compress and transfer air and water vapor from thaï flash tank to the condenser. _ system; . Fig. 3 is a view in 'vertical section of an escape ment valve associated with the regulator; and Fig. 4 is afragmentary view in side elevation 40 of the flash tank showing a plurality of steam jet boosters or ebmpressors connected to a com mon header in which the steam pressure is regu lated- by one- regulator. . 'I'hroughout the drawing and the `specification, In Fig. 1 of the drawing, a flash tank or vacuum chamber I is illustrated in which the rPhe steam flow through a nozzle is theoreti f‘ cally a function ofv the absolute nozzle pressure while the vapor flow from the ilashtank to the liquid, _such as water, is refrigerated. Thewater or liquid to be cooled is introduced into the iiash tank by a pipe 2 having sprays 3 extending from condenser is a function of the difference between the pressure in the flash tank and in the con discharges into the tank. The cooled or chilled denser'. When this differential is at the proper value and the nozzle pressure is at its eiiicient operating point, any increase in steam pressure .above that required to maintain the proper pres sure differential between the flash tank and the condenser will not effect any material increase l in the rate of transfer or vapor and air from 45 like ref_erence characters indicate like parts. opposite sides thereof and from which the water ` liquid or water is discharged into a cooling sys-.` tem,- not shown, by means of- a pump 4. The 55 water in the flash tank is chilled or cooled by maintaining a partial vacuum therein, the .de gree of vacuum depending uponl the temperature of liquid desired. The vacuum is maintained by vmeans of one or'more steam jet compressors " 2 2,186,114 or boosters 5 connected to the top of the flash tank and to the top of a water cooled condenser 6. Cooling water for condensing the steam is delivered to the condenser through an inlet pipe ‘I and is discharged therefrom through an outlet 8. The air and water vapor in the con denser is exhausted by means of a vacuum pump 9, and the condensate is discharged therefrom acteristics of the booster or compressor, while by means of a pump Iii'. 10 excess heat is put into the cooling Water unneces The steam jet compressors or boosters 5 are, sarily because of the excess steam employed. If the pressure of the steam at the nozzles were controlled in accordance with the pressure dif ierential existing between the flash tank and the condenser, considerable economies in the use of steam may be attained. Theoretically, the ñow as stated previously herein, operated by steam which is delivered thereto by means of a plu rality of steam nozzles II. Each booster may have one -or a. plurality of nozzles Il, which always function as a group, but the number of boosters in operation at any one time is de pendent on the load and these may be turned of steam through a nozzle is a function of the absolute nozzle pressure, While the flow of vapor “on” or “olf” manually or automatically in ac cordance with the load requirements. through the booster is a function of the diiîer Steam is' ence in pressure between the condenser and the 20 supplied to the boosters from a supply pipe or ñash tank when the evactor is working at its 20 header I2, and the pressure of the steam at the nozzles of these boosters is controlled by means of regulator I3. This regulator is illustrated as most eñicient point. with the value oi' steam pressure required. The steam, in passing through the nozzles of the booster or boosters is converted from pres sure head into velocity head, which creates a_ and eifects the transfer of air and water vapor from the iiash tank to the condenser. If the tem perature of the Water is to be maintained at 41° F., for example, then the absolute pressure in 35 the iiash tank is maintained at about 0.2575 inch of mercury. The action of the steam jet com pressors or boosters and the steam nozzles em ployed for creating and'maintaining the desired vacuum in the flash tank is well understood in 40 this art and for that reason no further descrip tion thereof is believed necessary. The control system of this invention is de signed primarily to secure economy in the use I of steam by regulating the steam pressure in ac cordance with the pressure differential between the ilash tank and condenser. -The function of the evactor is to transfer water vapor and air from the ñash tank to the condenser at such a rate as to maintain the proper degree of vac 50 uum in the flash tank. In accomplishing this transfer, the evactor must work against a pres sure head which is equal to the diiference, in absolute pressure, between the flash tank andcondenser pressures. The absolute pressure in' 55 the flash tank will vary only with variations in the temperature pressure in the amount of steam tity of available 60 of the chilled water, while the condenser will vary with the being condensed and the q'uan cooling water and its temper ature. r If the condenser water is cooled by a cooling tower (not shown) considerable variations may be expected in the condenser pressure. When the outside wet and dry bulb conditions are high, the refrigeration load will be high and the cool ing water for the condenser lwill be warm. Under these conditions the maximum pressure differ ence between the iiash tank and the condenser will exist. As the outside wet and dry bulb con 70 ditions become lower, the refrigeration require ments become less with the result that the cool ing water for the condenser will be colder; Thus less pressure difference exists between the ñash tank and the condenser under low outside wet and dry bulb conditions. ' In accordance with this invention, control ap paratus is provided which will maintain a defi nite relationship between the pressure diiîeren comprising a valve I4 and a pressure actuated 25 device I5 for adjusting the valve in accordance 30 vacuum and lowers the pressure in the iiash tank If the steam pressure at nozzles II is higher than that required to transfer the vapor and air from the iiash tank to the condenser at a rate which will maintain the required pressure difference between the ñash tank and the con el denser, no material increase in the amount of vapor transferred is eiïected because of the char tial existing between the ñash tank and con- ~ denser and the pressure oi' the steam at the nozzles, thereby avoiding the use of excess steam to accomplish the work involved. The capacity of the refrigerating system would be adjusted by changing the number of boosters or compressors 30 employed at any one time either by hand or automatically, without in any way interfering with the operation of the control system in main taining the above stated relationship between the nozzle steam pressure and the pressure differen 35 tial between the flash tank and condenser. The apparatus embodied in the control system comprises a regulator I 1 which is responsive to the pressure in the condenser and in the iiash tank and to the steam pressure at the~nozzles and causes regulating device I3 to operate in 40 such fashion that the' steam pressure at the nozzles will be caused to bear a definite relation ship to the differential between the flash tank and the condenser pressure. The steam actuating device I5 comprises a 45 pressure-tight housing I8 having therein a ilexi ble member I9, such as a bellows, which carries a thrust plate 20 at its upper end. The- thrust plate when it is in' its uppermost position engages spaced lugs 2I on the top of housing I8 so that actuating pressure when admitted to the hous ing will compress the bellows and move the thrust plate downwardly. A boss 22 centrally positioned on the lower side of plate 20 is coupled to stem 23 of valve I3 by means of a push rod 24 and 55 adjustable couplings 25. These couplings pro vide a means for adjusting the valve in relation to the limits of travel of the bellows. The lower limit of travel of thrust plate 20 is ñxed by a tubular stop 26 which is threaded on boss 22 to 60 provide adjustment in the downward movement of the plate. Movement of the bellows is resisted by a coll spring 21 located between the thrust plate and the bottom- of housing I5. The coil spring urges the plate and valve stem upwardly 65 and tends to actuate valve I4 to a position of minimum opening, in which case minimum steam pressure exists at nozzles II. As the pressure of actuating medium delivered to housing I 8 in 70 creases the thrust plate moves- downwardly thereby moving thel valve stem towards open vposition and increasing the pressure of the steam nozzles. ‘ The operating medium for actuating device I5 3 2,136,114 may be compressed air taken from a supply pipe 28 in which the pressure is substantially constant, and transmitted thereto by -regulator I1 at varying pressures depending upon the relation between the nozzle steam pressure and the pressure dif ferential between the flask tank and condenser. Regulator I1 need not be of any special con struction, as any regulator which will provide stability in the relationship between the nozzle steam pressure and the flash tank-condenser pressure differential will serve the purpose. The illustrated embodiment of regulator I1 is pre ferred, but as novel features of this regulator per that is, up or down as seen in the drawing. This gradient diminishes from the maximum value it exerts at the beginning of movement of the dia phragm to zero value and at a rate which allows suñicient time `to elapse to effect the necessary;` adjustment in the steam pressure called for by a change in the pressure differential between the flash tank and condenser `or as effected by a change in steam pressure without a change in the pressure differential, as where the number of noz zles II in use is changed to suit a change in load ` ' on the refrigerating system. l se are disclosed and claimed in a copending ap 15 plication of Robert R. Donaldson, Jr., Serial No. 14,468 filed April 3, 1935, and assigned to John M. ’ Hopwood, no claim thereto is made herein. Regulator l1 comprises an escapement valve 3D (see Fig. 3)_ which controls or determines, by its position in a valve body 3|, the pressure of the air delivered through a pipe 3|' to device I5;. a dia phragm 32 disposed in a housing 33 which responds to the difference in pressure between the flash tank and condenser; a steam pressure responsive device 34; and a lever 35 fulcrumed on a roller'36 and operatively connected, at one end and on one side of the fulcrum by a link 35’ to device 34 and on the other side of the fulcrum to the pressure differential responsive diaphragm 32. Thus the 30 escapement valve 30 is under the joint control of the pressure differential responsive diaphragm and to the steam pressure responsive device 34 The dash-pot comprises a coil spring 41 which is connected at its upper end to the pressure dif ferential responsive diaphragm and at _its lower 15 end to a piston 48 disposed in a vertically extend ing cylinder 49. The upper end of the cylinder is open to the atmosphere and the lower end is connected to a chamber 50 formed by a flexible member such as a bellows. The bellows is en 20 closed in a pressure _tight housing 5I to which air pressureis .admitted by a pipe 52 at pressures determined and controlled by valve 30. The lower end of the) bellows is closed by a thrust plate 53 which in its lowermost position is spaced from the 25 bottom of the housing by“ lugs 54 to allow the air pressure to work properly on the bellows. A com pression spring 55 located inside the bellows yield ingly opposes contraction of the bellows and pro vides a positive gradient against which the air 30 pressure must work. Housing 5I is carried by a frame 56 which sup ports the diaphragm housing and the aforemen so that the steam pressure at nozzles II will be ' tioned parts above it, and the housing also car-' controlled and adjusted in accordance with the pressure differential between the flash tank and' condenser. As will be disclosed later herein,.the range of steam pressures which will balance a correspond ing range of pressure differentials between the ries a bracket 51 onl which a steam pressure re flash tank and condenser may be changed by ad- tom of the cylinder is connected by pipe 58 which is connected at its -top with the interior of cylin justing the position of fulcrum 36 with respect to link 35’. In order that the weight of lever 35 may not affect the operation of the diaphragm 32 and de vice 34 in their responses to the flash tank and condenser pressure differential and the steam pressure, respectively, a relatively light spring 39 35 sponsive device 34 and the fulcrum 36 are sup ported. » - I The space in cylinder 49 above and below piston 48 and the space within bellows 50 are ñlled with a non-compressible fluid such as pil and the bot der 49 at a point above the piston, at a height above the uppermost limit of travel of the piston. The pipe 58 is provided with a needle valve 59 that 45 fixes the rate, for a given oil pressure, at which oil may ñow from the space below the piston to the space above it, or -vice versa, in case either - is connected at one end to lever 35 at a suitable the bellows contracts or expands, respectively, or point between fulcrum 36 and the connection be in case the piston is moved downwardly or up tween valve 30 and the diaphragm 32, and at its opposite end to an anchor 40 which is supported by an adjustment screw 4.I from a support hous ing 42 carried by a frame 43 on which valve 30 'and body 3| are supported. This spring is ad justed to carry the unbalanced weight of lever 35 and maintain it in operating engagement with the wardly, respectively, by the diaphragm 32. If diaphragm 32 moves downwardly in re-I sponse to an increase in the pressure differential between the >flash tank and the evactor, spring 41 is compressed and opposes such movement of the diaphragm but the spring compression tends valve and diaphragm connection. The opposite to move the piston 48 downwardly at a rate fixed by the rate at which the oil can flow from the end of the lever is connected to an adjustable space below the piston to the needle valve to the tension spring 44 which fixes the loading that de- ì space above it. As the piston moves downwardly 60 7,0 vice 34 operates under and provides a means for the restraint offered by the spring tends to dimin initially adjusting the steam pressure at nozzles ' ish but, while this restraint is diminishing, valve I I to the proper value for a given flash tank and 30 is being opened to deliver air at increasing condenser pressure differential. Regulator I1 is pressure to device I5 and to the interior of hous 65 in equilibrium at these values of pressure dif .ing 5I, thereby increasing the steam pressureat ferential and steam pressure, and thereafter the the nozzles 1, because valve I4 has been opened regulator will automatically adjust the steam wider, and increasing the pressure acting-on the pressure so that the regulator will always be in dash-pot bellows 58. Bellows 50 therefore con tracts an amount proportional to the pressure ex balance for different values of pressure differen erted on it and exerts an hydraulic pressure on the 70 tial. lower side of the piston 48 tending to move it up Regulator I1 also embodies a stabilizing means wardly and to further compress spring `41. This ’in the form of a dash-pot 46 which acts to provide a positive but gradually diminishing gradient increased compression in spring 41 tends to move against which the pressure differential diaphragm A75 32 must work when moving in either direction, the diaphragm 32 upwardly, but this tendency diminishes at a rate proportional to the rate at 75 4 2,136,114 which the oil iiows through the needle valve into the space above piston 48 in cylinder 49. This increased pressure on the dash-pot bellows and on the bellows of the steam responsive device 35, slows down the corrective action of diaphragm 32 sufliciently to permit enough time to elapse to effect the proper adjustment in the steam pres sure as called for by the change in the pressure diiferential between the flash tank and the con 10 denser. By the time the steam pressure has been adjusted to balance the pressure differential act ing on the diaphragm of regulator I1, the effect of the dash-pot has diminished to the vanishing point and the coil spring 41 associated therewith 15 will have assumed the position it normally occu pies when equilibrium is reached between the dif ferential acting on diaphragm 32 and the steam pressure acting on the 4bellows steam responsive When diaphragm 32 moves upwardly, it moves -valve 30 upwardly to a position which reduces the area of opening 18 in the inlet port- of valve body 3l and increases the area of opening 19 in the exhaust -port at the lower end of the valve body n. through which air may exhaust to the atmos phere. Thus, the relative areas of the inlet and exhaust openings fixes the pressure of the air ex isting within valve body 3| and as transmitted through outlet port 80 to pipe 3 I ' which communi cates with the interior of the housing I8 device I5 and to the interior of the dash-pot bellows housing 5|. A Valve 38 as shown in'Fig. 3, is yieldingly urged towards open position, that is, towards maximum pressure transmitting position by means of a coil spring 82. Therefore, as the diaphragm moves downwardly, this spring will move valve 38 down device 34. ` wardly and cause it to follow push rod 11. 20 From the above it will be apparent that theA The exhaust opening 19 is lformed in a bushing magnitude of the pressure impulses delivered to 83 which is threaded into the lower end. of the the steam pressure regulator I3 and to the dash valve body and provides an adjustment which pot bellows 50 is proportional to the change in the fixes the amount of travel required to move valve pressure differential acting on ydiaphragm I1 30 upwardly to its extreme closed position or 25 and/or the steam pressure acting o_n'device 34. downwardly to its extreme open position, thatA For this reason, the greater these changes, the is, tothe position which the exhaust port open shorter will the time of correction be as fixed by ing 19 is closed. ' ` dash-pot 46, because the higher the pressure act In case it is desired to change the values of ing on the dash-pot bellows, the higher the rate 30 of oil flow through needle valve 59 will be. This steam pressure required by device 35 to balance a given differential acting on diaphragm 32, the action of the dash-pot prevents over-correction of fulcrum roller 36 may be shifted longitudinally of y the nozzle steam pressure. lever 35 either towards or away from spring 39. The dash-pot working in conjunction with dia The closer fulcrum 36 is to the connection of the phragm 32 therefore gives stable operation to reg steam pressure bellows to lever 35, the higher the 35 ulator I1 and avoids over or under adjustments of the steam pressure whenever a change in the pressure differential between the ñash tank and the condenser occur. . In Fig. 2 of the drawing, the construction em 40 ployed for providing an operating connection be tween diaphragm 32 and the valve 30 and between the diaphragm and the 'dash-pot coil spring 41, is illustrated. As shown, thrust plates 68 and 6I are disposed on the upper an lower sides of the 45 diaphragm and give support and rigidity to the central or middle portion thereof. The center of the diaphragm and the plates are apertured to accommodate a connecting rod 62, the ends of which extend upwardly and downwardly, respec 50 tively, through the diaphragm housing’. The plates 60 and 6I are held flrmly against the dia phragm by means of bushings 63 and nuts 64. In order to provide a pressure tight joint where rod 62 passes through housing 33, suitable flexible 55 diaphragms 65 are secured between the bushings 63 and Washers 66, the required pressure being supplied by nuts 64, and by pressure tight sealing rings 61 which seal the outer edges of the open ings through which rod 62 passes. 60 , The lower end of rod 62 is provided with an anchor block 68 around which the upper end of coil spring 41 is disposed, and to which it is sel curely clamped by means of a clamping ring 69 and a screw 18. 65 The upper end of rod 62 is operatively con nected to valve 30 and lever 35 by means of a yoke 1I which is secured between the upper -nut 64 and washer 66. The upper end of the yoke is provided with a flange 12 which overhangs lever 70 35 and which carries a knife edge 13 on its under side which is engaged by lever 35. The upperside of this ilange carries a pin 14 having a conical point which seats in a socket 15 in the lower end of a push rod 11 that engages the lower end of 75 valve 38. see Fig. 3. ` ' steam pressure must be to balance a given pressure diiîerential between the ñash tank and the con denser, and the farther -it is away from this point of connection the lower the steam pressure must be to balance this differential. To provide _for this adjustment fulcrum roller 36 is mounted on a carriage 84 which is slidable on >bracket 51. The adjustment of the carriage may be accomplished by means of a screw 95 which is threaded into the fulcrum carriage and journalled in a bearing 86 which cooperates with collars 81 on the screw to prevent its longitudinal movement. By turning a handwheel 88 fastened to this screw, the fulcrum carriage and its ful crum roller may be shifted longitudinally 0f lever 35 to change the relation between the steam pressure acting on the nozzles and the pressure differential between the flash tank and the con denser. - -. ' ` The operation of the control system above de scribed is as follows: Assume that the absolute pressure to be maintained in ilash tank I is P1 pounds per sq. in. and that the absolute pressure in the condenser is P2 pounds per sq. in., then the pressure differential in pounds per sq. in. is equal to (Pif-P2). Assume also that for this differential of (P1-P2) that the evactor or venturi 5 requires a steam pressure on the noz zles II of P pounds per square inch. With these assumed conditions, regulator I1 is then adjust ed, as hereinbefore described, until a steam pres-sure of P pounds per square inch balances the differential of (P1-P2) acting on diaphragm 32. Under these conditions valve 30 will be in such a position as to effect the delivery of compressed air to device I5 and to the dash-pot bellows hous 70 ing 5I at L pounds per square inch. Under these conditions the steam valve I4 will be held at a fixed opening, an opening which will deliver steam to the nozzles II at a pressure of P pounds per square inch. 75 5 2,136,114 If all of the steam boosters are not operating and another booster is turned on therel will be a pressure drop in the steam pressure acting on the nozzles of these boosters because of the increased steam flow through valve I4. This reduced steam pressure is reflected in the steam pressure re sponsive device 35 with the result that regulator I1 is unbalanced. When this happens the dia phra‘gm 'moves downwardly to open valve 30 an 10 amount depending upon the unbalance and in creases the pressure of the air in device I5. This results in a further opening of valve Il and in creased steam pressure. 'I'he increased steam pressure results in increased steam iiow lthrough 15 the booster nozzles so that the pressure in the- condenser is increased thereby increasing the dif ference between the pressure in the iiash tank and condenser. This increase in differential fur tions in the pressures existing in the vacuum chamber and the condenser. ` -2. In a steam reirigerating system having a vacuum chamber in which iiuid is cooled, a con denser, and a steam jet compressor connected be tween said chamber and condenser, a steam noz zle disposed to deliver steam at' high velocity through said compressor to establish a partial> vacuum in said chamber, a source of supply oi steam for said nozzle, and means for varying the 10 pressure of the steam delivered to said nozzle, the combination of a device having means respon sive to the pressure of the steam delivered to said nozzle, and to the difference between the pres sure in the vacuum chamber and in the con 15 denser for so regulating the steam pressure vary ing means that the pressure of the steam as de livered to said compressor is caused to bear a deñnite relationship to the diilerential in pres- ` ther unbalances regulator I‘I in a direction which sure between the flash tank pressure and the 20 will further increase the air pressure in device I5 pressure. ’ and further increase the~ extent of opening of the condenser 3. I_n a' steam refrigerating system having a steam valve I4. This action continues until the flash tank in which ñuid is cooledby the action steam pressure acting on the nozzles of the oi' partial evaporation, a condenser, and a booster boosters-is in balance with the pressure diEer connected between said tank and condenser, a 25 ential (P1-P2) acting on diaphragm 32. At this steam nozzle disposed to deliver steam through new equilibrium between steam pressure and pres said booster at high velocity to establish avac sure differential, regulator I‘I will maintain a uum in said flash tank, means for controlling the higher steam pressure on the booster nozzles but nozzle steam pressure, means responsive to flash the value of Pl-P2 will be the same for any value tank pressure and condenser pressure', means re 30 of steam pressure required to maintain it. Regu sponsive to the nozzle steam pressure, and means lator I1 acts to regulate the steam pressure di jointly controlled by all said pressure responsive rectly in accordance with the diiïerential in pres means for operating the nozzle steam pressure sure between the ilash tank and the condenser controlling means to maintain a predetermined independently of the number of boosters in use relationship between the nozzle steam pressure 35 at any particular time._ And regardless of the number of boosters in use, the steam pressure f and the diiîerence between the flash tank and condenser pressures. acting on nozzles II will be regulated tomain 4. In a steam refrigerating system having a rtain the value of (Pl-P2) constant even though “ ilash tank in which iiuid >is cooled by the action the »individual values of P1 or P2 may vary slight ly. But since regulation of the steam pressure of partial evaporation, a condenser, and a plu 40 results from a change in either P1 or P2 or vin the steam pressure and since regulator I'I is ini tially adjusted to maintain the difference be tween‘Pl and P2 constant, it will be apparent that the steam pressure will always be adjusted to maintain this difference whenever P1 or P2 or rality of steam jet compressors connected be tween sald tank and condenser, each compressor having a plurality of steam nozzles disposedto deliver steam through said compressors at high velocity to establish a vacuum in said ñash tank, 45 means for controlling the steam pressure at the both change in values to depart from a constant - nozzles, means responsive to the ilash tank pres diiïerence between them. - sure and the condenser pressure, means respon ` While but one embodiment'of the control sys tem or this invention has been shown and de scribed, it will be apparent to those skilled in this sive to the nozzle steam pressure, omeans jointly controlled by` all said pressure responsive means 50 for maintaining a predetermined ratio between art that various modifications and changes may A thev nozzle pressure and the difference between be made in thesystem and in the operative ele ments of the system without departing either from the spirit or the scope of the invention. ~ What I claim as new and desire to secure by Letters Patent is: 1. In a steam reirigerating system having a vacuum chamber in which iiuid is cooled, a con denser, and a steam :let compressor connected be tween said chamber and condenser, a source of supply of steam connected to _flow .through said the iiash tank and condenser pressures ,inde pendently ci.' the number of compressors in op eration, and means for adjusting the ratio of steam pressure at the nozzles to the pressure 5.5 differential between the flash tank and condenser. 5. In a steam refrigerating system having a ilash tank in which iiuid is cooled by the action of partial evaporation, a condenser, and a booster 60 connected between said tank and condenser, .a steam nozzle disposed to deliver steam through said booster at high velocity to establish a vac uum in said ilash tank, means for controlling the nozzle steam pressure, means responsive to delivered to said compressor, and a source or flash tank pressure and condenser pressure, and supply of cooling iiuid for the condenser for con vmeans controlled by said pressure responsive densingrthe steam delivered thereto, the combina means for operating the nozzle Asteam pressure tion of a device- having means responsive to the controlling means to maintain a predetermined pressure of the steam as delivered to said com relationship between the nozzle steam pressure 70 pressor and means responsive to the pressure in 70 the and the diiîerence between the ilash tank and vacuum chamber and condenser, for so con trolling the steam pressure varying means that condenser pressures. compressor to establish a partial vacuum in the chamber, means for varying the’pressure of steam the pressure of the steam as delivered to said compressor is varied in accordance with varia s - AIFRED A. MARKSON.