Патент USA US2116958код для вставки
May 10, 1938. K. P. BRACE Er AL 2,116,958 MEANS FOR CIRCULATING FLUIDS Filed April 19, 1935 2 Sheets-Sheet l . 31; ‘ 3nventor4 ffemperPBrace ZRObertBPQr'a 0rd 5 W(Ittomeg “If May 10, 1938. K, p_ BRA¢E ET AL 2,116,958 1 MEANS FOR 'CIRCULATING FLUIDS Filed April 19, 1935 2 Sheets-Sheet 2 i m \. M Mu ffemperPBrace 3nnentoud Z?’ober?i POmwfard 015W Gttorneg Patented May 10, 1938 2,116,958 ‘ um'rao ,S'l'A'i‘ES PATENT OFFICE ' 2,116,958 ' MEANS FOR CIROULATING FLUIDS _ Kemper l‘. Brace and Robert B. P. ‘Crawford, ' - Washington, D. 0. Application April 19, 1935, Serial No. 17,368 10mm. (Cl. 62-1195) This invention deals with the forced circulation of ?uids and more particularly with the propul a non-electrolyte, the osmotic pressure of a solute pressure without the employment of pumps or other mechanical moving parts. An object of lowering caused by the solute in the solution. The equation connecting the lowering of the vapor sion of one liquid into another under a higher _ in a solution is a function of the vapor pressure the invention is to provide a method and ap pressure and the osmotic pressure is as follows: _R-T P°"'P -_1_(p0—p)’ 1(p0—p)‘ ‘ paratus for continuously concentrating a solu l0 tion which is being continuously vdiluted and for continuously diluting a solution which is being continuously concentrated thereby maintaining P_TS( p0 +2 a method and apparatus for pumping the liquid in an absorberv type of refrigerator from the ab 20 sorber into the boiler without the use of mechani cal pumps and without the use 01' hydrogen or other gases commonly used to balance the pres sures in systems of this kind. 10 S=Speci?c volume of the solvent at P =Vapor pressure of the pure solvent p=Vapor pressure of the solution. A further more speci?c object is to provide a method and means for. supplying liquid to a chanical moving mechanism. A still further more speci?c object is to provide ' T=Absolute temperature ‘ 16 boiler without the use of a pump or other me po R=Gas constant=82.07 the degree of concentration substantially con-. stant. p0 +3 where P=0smotic pressure in atmospheres From the (above formula it can be readily seen 15 that the osmotic pressure of any solution which is of su?icient concentration to lower the vapor pressure appreciably of the solvent is very high. For example, the. osmotic pressure of a six molar (67%) sugar solution is 232 atmospheres or 3410 20 lbs. per square inch whereas the vapor pressure lowering of a six molar sugar solution Further objects and advantages will become LIL'LP) pc 25 apparent as‘ the description proceeds. _ Referring to the accompanying drawings which 25 is only 20% at 70 degrees F. , ‘ are made a part hereof and on which similar ‘ ‘The fact that the osmotic pressure of a six reference characters are used to denote the same _ molar sugar solution is equal to 3410 lbs. per > part thruout, 30 Figure 1 is a view in elevation of one of the simplest forms of apparatus embodying the in vention, . ' Figure 21s a view in elevation of a refrigerat ing system of thevabsorber type showing the ap 35 plication of the invention, Figures 3 and 4 are modi?ed forms of refrig erating apparatus showing the invention. It is well known that if a pure solvent is sepa rated from a solution of a solute in the same solvent by a semi-permeable membrane, there will be a ?ow of solvent thru the membrane into the solution. This ?ow will occur even when the pressure upon the solution is much greater than the pressure upon the solvent. The pressure 45 necessary to be applied to the solution to prevent. this ?ow is called the osmotic pressure of the solu As would be expected, the‘ osmotic pres square inch means that if a semi~permeable mem brane separates the solution from pure solvent, 30 that is, frompure water, a pressure of 3410 lbs. per square inch would have to be applied- to the solution to prevent water from passing thru the membrane into the solution. 11' instead of separating a solution from a pure 35 solvent, a solution is separated from a stronger solution by meansoi' a semi-permeable mem brane, there will be a ?ow of pure solvent from the weaker‘solution to the stronger and the pres sure causing the ?ow is equal to the difference 40 between the osmotic vpressures of the two solu tions. The ?ow will continue until the concen tration of the two solutions is the same, that is until both solutions have the same osmotic pres sure. ‘ 45 Now if the stronger solution is continually con sure of any solution depends upon the co'ncen- v centrated by boiling oil? the solvent and the weaker solution is continually diluted by the ad tration of the solution, that. is, the higher the 50 concentration, the higher the osmotic pressure. dition of pure solvent, then the ?ow of pure n For solutions, of non-electrolytes such as cane - solvent" thru the membrane from the weaker solu 50 sugar, the osmotic pressure is equal to the pres-’v tion to the strong solution will continue as long as sure which an equivalent gram molecular volume there is a difference in concentration. Figure 1 shows one of the simplest embodi of the solute would exert if con?ned to the space 55 occupied by the solution. Due to the e?fect of ments of the invention in the form of apparatus ionization, the osmotic pressure of electrolytes for continuously concentrating a solution which 55 is being continuously diluted and for diluting a such as NaCl, NaOH, LiC'l, etc., is as a rule con ‘ tion. , siderably higher than that of non-electrolytes of the same concentration. It hasibeen found that for any substance, whether it is an electrolyte or solution which‘ is being continuously concen trated. _Vessels Ill and l l contain weak solution I 2- and strong solution l3 respectively of some non-volatile solute in a suitable solvent, such for 60 2,1 18,958 2 example as cane sugar in water. The solutions are separated by a semi-permeable membrane 15. Pure solvent may be boiled o? from the strong solution I3 by heating element 14, thereby con centrating the solution and pure solveht'may be supplied by pipe [8 to the solution 12 to dilute this weak solution. So long as the concentration of the solution 13 is greater than the concentra tion of the solution 12 there will be a ?ow of pure 10 solvent thru the semi-permeable membrane from chamber 18 into. chamber ll. - We may assume that the solution 12 is a 1.0 molar solution of cane sugar in water and that the solution 13 is a six molar solution of cane sugar 15 in water. The osmotic pressure of a six molar with the solutions and solvent, all air and other foreign gases are evacuated from the system and the system closed. The evaporator will be sur rounded by or in heat exchange relation with the media to be cooled. Heat extracted from this medium will evaporate the refrigerant. Now the vapor pressure above the pure solvent 28 is greater than the vapor pressure above the weak solution 28. There will therefore be a ?ow of vapor from chamber 18 thru channel 8| into 10 chamber 19, this vapor being absorbed into the solution 28. This evaporation of vapor from the solvent ‘body 28 and absorption into 28 will cause the temperature in 18 to fall and the temperature in IS to rise. The added heat in solution 28 may solution is 3410 lbs. per square inch. The osmotic be carried o? by'the cooling coil 25. The addi pressure of a 1.0 molar solution is 397 lbs. per tion of pure solvent to the weak solution 28 will square inch. Therefore, the force driving pure tend to dilute this solution. But the solution in solvent (water) from the weak solution 12 into the boiler 20 is stronger than the solution 28. There will, therefore, be a flow of pure solvent 20 the strong solution 13 is 3410 minus 397 lbs. per thru the semi-permeable membrane 82 from the square inch or‘3013 lbs. per square inch, and nothing will stop the ?ow of solvent from the body of solution 28 into the solution 21. The weak into the strongsolution except an external heater 24 continuously boiling of! pure solvent pressure on the strong solution of 3013 lbs. per from the solution 21 continuously concentrates this solution. The addition of pure solvent from 25 square inch. It is apparent from the foregoing absorber 19 will tend to keep the solution at the that a semi-permeable membrane provides means for causing a solvent to ?ow from a weak same degree of concentration. The rate of flow of pure solvent from I8 to 28 solution under a low pressure to a strong solution is directly proportional to the di?erenoe between under a. high pressure without the aid of a me the osmotic pressures of the solutions 21 and 28 30 chanical pump. Pressure may be built up in the minus the difference in total pressure in vessels boiler by providing a throttling valve 11. i9 and 211. Thus if the solution 28 is a 1.0 molar From‘ the structure described it will be ap sugar solution having an‘ osmotic pressure of 397 parent that the device may have many possibili ties in its adaptation to useful purposes. For lbs. per square inch and solution 21 is a 6 molar sugar solution having an osmotic pressure of 3410 35 example, if the vapor under pressure from the lbs. per square inch and if the pressure above the boiler is conducted to a ?uid motor the device two liquids be ignored for the present, there will may serve as a boiler for an engine in which the boiler is fed without the use of mechanical pumps be a difference in pressures of 3410 minus 397, or 3013 lbs. per square inch and this will represent or injectors. the force driving the pure solvent from solution Figure 2 shows the invention adapted to a re 40 frigerating system of the absorber type. In this 28 into- solution 21. For practical purposes a solution of sodium by form of refrigerator a vapor is absorbed into a solution. As here shown numeral 18 indicates an droxide (NaOH) . and water is preferable to the ‘ cane sugar solution. Let us assume, therefore, _ evaporator, 19 an absorber, 20 a boiler, 2i a con . that water and NaOH are the‘ solvent and 'the denser, 22 a vapor conducting connectionfrom 45 the ‘boiler to the condenser and 123 a connection . solute-respectively. Let us assume that the tem from the condenser‘ to the evaporator. v Vapor is perature desired in the evaporator is 40 degrees boiled o? by a heater 241. A cooling coil 25 cools F. and that the ‘temperature of ‘the tap water for the liquid in the absorber._ This cooling coil may cooling coil 25 is '10 degrees. Now the vapor pres; be supplied with cooling water which passes thru .. sure of water at 40 degrees is 6.4 mm. of Hg'and so 'pipe 26 to the condenser after leaving coils 25. If therefore in order for the-water 29_ in the evapo preferred both the cooler 25 and the condenser rator 18 to boil at 40°, the vapor pressure of the may be air cooled; :such cooling systems are well solution 28 in the-absorber 19 must be less'than' known and therefore need ‘not be here described; 6.4 mm. of Hg at a temperature slightly in ex ‘ Before starting, the boiler will be partially ?lled "cess of 70 degrees (say perhaps 80 degrees). Ex perimental data showithat the vapor pressure of _ with a suitablesolntion. . .This may be a solution a 40% solution of NaOH in water exerts a vapor of cane ‘sugar and water asstated in the descrip tion of the system shown hf‘Figure 1, or a solution . pressure of 5.3 mm. of Hg. at 80°. Y Therefore, we of any suitable non-volatile solute, such as NaOH, can assimie that the concentration of the solu tion 28 is 40% and that the driving force causing v60 .LiCl, H2804, Lil, ZnCl, etc., in a solvent. Numeral 21 indicates the strong solution in the solvent vapor (water) to pass from l8 to'l9 as boiler, 28 a weak solution in the absorber and 29 6.4-5.3,‘that is as 1.1 mm. of mercury. Withan the pure solvent in the evaporator. There will unrestricted passage 31 between the chamber 18 be a body of solvent'vapor 30 above the body .of and‘ the chamber 19 water vapor will pass at a rapid rate from 29 to 28 and the temperature of 65 solvent in the evaporator. The upper portion of 29 will be maintained at 40 degrees as long as the ‘the evaporator communicates with the upper por temperature of the solution 28 is kept at 80 de tion of the absorber thru a passage 3|. A semi permeable membrane 32 separates the strong grees and the concentration at 40%‘. In‘ order to maintain the concentration at 40% solution 21 in the boiler from the weak solution pure solvent must pass thru the semi-permeable 70 28 in" the absorber.‘ Suitable examples of such 70 membrane as fast as solvent vapor passes from membranes are collodion, parchment, animal in testine, animal bladder, ?sh skin, rubber,-copper 29 to 28. In order to maintain this osmotic ?ow ferrocyanide precipitated in porous earthenware, of pure solvent from weak solution" into strong solution 21 the concentration of 21 must be much porcelain, ground glass, gelatine, etc.v After ?lling the system to the desired levels greater than'28. Let us assume that the concen- 7‘ 75 2,116,958 tration of 21 is 50% by weight. By the formula given, the osmotic pressure of a 40% solution 28 at 80 degrees F. is 28,300 lbs. per square inch. The osmotic pressure of a 50% solution 21 at 165 degrees F. (B. P. at 36 mm. Hg) is 35,750 lbs. per square inch. The di?'erence- between the osmotic pressure of solution 21 and solution 28 is 7,450 lbs. per square inch. Experimental data indicate that the amount of semi-permeable 10 membrane required for a 100 lb. ice box is five square feet. Figure 3 shows- a form of the invention in which an interchanger 40 is positioned between the concentrator and the absorber. It will be noted that there is a temperature difference of about 85 degrees between the concentrator and the absorber. It is advisable to prevent a loss of heat from the concentrator to the absorber. The interchanger is designed to reduce the heat loss 20 as far as possible, and thereby increase the em ciency of the system. Numerals 4|, 42, 48 and 44 denote the condenser, the evaporator, the ag 3 ammonia in the condenser at a temperature of 110 degrees. " Now the vapor pressure of pure ammonia 45 in the evaporator 42 at 15 degrees F. is 2100 mm. of Hg. In order to have a ?ow of vapor from the evaporator to the absorber the vapor pressure of the weak absorbing solution must be less than the vapor pressure of the pure solution. The vapor pressure of a 60% solution of NH‘CNS in ammonia at 100 degrees F. is approximately 2000 10 mm. of Hg. This gives us a vapor pressure diifer ence‘ between the evaporator and the absorber of 100 mm. of Hg. We may therefore assume that the weak solution 46 is a 60% solution of NH4CNS in NH3. According to the formula the 15 osmotic pressure of a 60% solution of NH4CNS in NH; at 100 degrees F. is 40,719 lbs. per square inch. Assume that the strong solution 41 in the boiler is an 80% solution of NH4CNS in‘NHa. From the formula we note‘that the 20 osmotic pressure of an 80% solution of NHiCNS in NH: at 100 degrees F. is 49,677 lbs. per square T e inch. It should be noted that the strong solu evaporator contains pure solvent 45, the absorber tion which is circulated from the boiler is cooled contains weak solution 46 and the boiler a strong by the jacket 64 and by the body of weak solu solution 41. Solvent is boiled off by heater 48. tion at 100 degrees temperature which surrounds Cooling water for the cooler 48 is supplied thru the chamber 58. pipe 50 the water leaving thru pipe 5! after pass Now as we have stated above, the vapor pres ing thru the condenser 4| to condense the vapor sure above the ‘weak solution 46 is 2000 mm. of from the boiler. Both cooler 48 and condenser Hg or about 38 lbs. per square inch. The vapor 30 4| may be air cooled if desired. pressure above the strong solution is the‘ vapor The upper portion of the evaporator chamber pressure of pure ammonia at condenser tempera is connected by pipe 52 with a pipe 58 which ex .ture, which as we-have stated is 110 degrees F. tends down into the weak solution 46 and ter This vapor pressurelis about 250 lbs. per square minates in a header 54 which is perforated to inch. The force tending to drive pure ammonia 35 permit vapor to pass into the solution 46 and be liquid from the weak solution into the strong is sorber and the concentrator or boiler. absorbed therein. The absorber is connected by pipes 55 and 56 with a chamber 51 thru which the weak solution is circulated by convection. 40 A chamber 58 is ‘positioned within the chamber 51 and its walls are formed partially from semi permeable membraneous material 59. The strong solution in the boiler is circulated thru the chamber 58 passing from the boiler thru pipe 45 63 thence thru the interchanger 40, pipe 60, pipe 61, back thru the interchanger 40 and pipe 62 into the boiler. A water jacket 64 may be placed about the pipe 60 to cool the strong solution be 50' fore it enters the chamber 58. This jacket may be supplied with water from the coil or water cooling jacket 48.‘ ' The heater may include a ?ue 61 which passes up thru the boiler to effect better heating. Refrigerant vapor driven oi the boiler passes thru pipe '65, condenser 4| ‘and into receiver 66. In order to insure that only liquid refrigerant shall pass from the receiver to the evaporator a valve 68 operated by a ?oat 69 controls passage of refrigerant to the evaporator. ‘ Any suitable refrigerant may be used. For domestic refrigerators requiring evaporator tem ‘ perature of 20 degrees or lower it is believed the most satisfactory solution ‘would be a solution of ammonium thiocyanate (NHiCNS) in liquid ammonia (NH:). v ‘ Let us assume that the temperature desired in the evaporator is 15 degrees F. and that the tem perature of the tap water or cooling air, when air is used, is 90 degrees. We will assume that the cooler 48 is large enough to maintain a tempera ture of 100 degrees in the weak solution 46. We will assume also that the cooling water in passing thru the cooler 48 is heated to approximately‘ 100 degrees and that it is e?ective to condense the (49,677+38) —(40,719+250) =8746 lbs. per square - inch » , It is therefore apparent that in spite of the pres sure difference of 212 lbs. in the boiler and the absorber pure liquid will ?ow from the absorber into the boiler at a rapid rate thru the semi permeable membrane due to osmotic force. Figure 4 shows another embodiment of the in vention. Numerals 10, 1| and 12 represent the 45 evaporator, the boiler and the absorber. The ab sorber consists of a plurality of tubes having walls of semi-permeable membraneous material connecting headers‘!!! and 82. This absorber is positioned in a chamber 13 where it is enveloped in vapor passing from the evaporator thru pas sage 14. The solution circulating by convection ' thru the absorber is cooled by air cooler 15 of any suitable sort. Pure solvent vapor in chamber 55 13 will be absorbed thru the walls of the tubes and will tend to dilute the solution therein. To maintain the proper degree of concentration in the tubes, a portion of the solution is circulated thru the boiler thru pipes 11,18 and interchanger 18. This circulating solution ‘is cooled by air cooler 16. This pipe 18 may be coiled around the ?ue 80 to effect better heating. The boiler will be partially ?lled with a suit able solution. This may be a 60% solution of 65 NHACNS in NHa. The pure solvent in the evapo rator may be liquid ammonia 82. Ammonia vapor boiled o? from the boiler will pass thru pipe 93, be condensed by air condenser 83 and delivered to receiver 84. A valve 85 controlled 70 by ‘bellows 86 will control passage of liquid from pipe 81 to pipe 88 so .as to prevent the passage of gas to the evaporator- Pressure in the bellows and pressure below the valve will be equal since both are subject to the pressure in the condenser 9,118,958 4 causing osmotic ?ow of pure solvent from the weaker to the stronger solution. 3. A refrigerator of the absorber type compris thru pipes 81 and 88 so that'the valve 85 will be closed by gravity. When liquid accumulates in the leg 88 of the U-tube this will unbalance the valve and permit liquid refrigerant to pass thru the valve into the line 89. ing a boiler, an absorber, an evaporator, a con denser and heater, the boiler having therein a strong solution of a solvent and a non-volatile solute, the absorber having therein a weaker solution of the same solvent and solute, means Instead of the pressure operated valve Just de scribed we may use the ?oat controlled valve shown in Figure 3. Assume that a temperature of 15 degrees F. is 10 desired in the evaporator and that the cooling for conducting vapor from the evaporator into the weaker solution to have it absorbed therein, 10 means for circulating said weak solution and for media for the absorber is at a 90 degree tempera ture and that the coolers are suf?ciently large to maintain a temperature of 100 degrees in the absorption solution and a temperature of 110 de 15 grees in the condenser. We will assume, as stated above, that the solution Si is a 60% solution of . NHlCNS in NIB. cooling it, a semi-permeable membrane separat ing the weak from the strong solution, means for circulating said strong solution in surface contact with said membrane to circulate the pure solvent absorbed from the weaker solution and bring it into the boiler to dilute the solution therein which is being continuously concen trated by boiling oif pure solvent therefrom. 4. A refrigerator of the absorber type compris Now, as we have stated, the vapor pressure of pure ammonia at 15 degrees is ‘2100 mm. of Hg. The vapor pressure of a 60% solution of NH4CNS in NH: at 100 degrees F. is ing. a boiler, an evaporator, an absorber, a plu 2000 mm. of Hg. The osmotic pressure of a 60% rality of tubes positioned in the said absorber, said solution of NHrCNS in NH: is 40,719 lbs. per tubes being ?lled with a solution of a solute and square inch. Since there is a pressure in the a solvent, said tubes being exposed to solvent absorber chamber 13 outside the tubes of about ' vapor from the evaporator, said tubes having '38 lbs. per square inch the total force tending to walls of semi-permeable membranes to cause the drive the pure solvent into the solution thru the solvent to flow by osmosis from the absorber to semi-permeable membrane is I 40,757 lbs. per the solution, means for carrying. of! heat from square inch. But the vapor pressure of the pure the solution, and means for circulating said so ammonia in the condenser is the vapor pressure lution thru the boiler, and means for boiling of! at a temperature» of 110 degrees which is about pure solvent from the solution, for condensing it 250 lbs. per square inch. Taking this from the and returning it in liquid form to the evaporator. pressure indicated above, since this is a pressure 5. A refrigerating system of the absorber type acting against the flow of solvent into the strong comprising a still, an absorber, an evaporator, a solution, we have a total pressure acting to drive condenser, and a semi-permeable membrane sep arating vapor of the pure solvent in the evapo rator from solution circulated from the still, a liquid\trap between the condenser and evapo solvent vapor into the solution of 40,507 lbs. per square inch. , 8 From the foregoing it will be apparent that we have a system in which the solvent will be auto matically supplied to the boiler and that the sys tem will operate continuously without. the neces rator, and a pressure controlled balanced valve operable upon a rise of liquid in the trap for re 40 turning only liquid refrigerant to the evaporator. sity of a pump or the presence of an inert gas to .6. A device of the kind described comprising tion without departing from the spirit thereof. We, therefore, do not limit ourselves to the in a pair of chambers, one containing a solution of a volatile solvent and a non-volatile solute, the other containing a body of the solvent substan-, tially free of the solute and under a pressure less than the pressure in the ?rst named chamber, a vention as shown in the drawings and- as de semi-permeableymembrane separating the solu scribed in the speci?cation but only asset forth tion from vapor of the body of pure solvent, and means for vaporizing solvent from the solution 50 balance pressures. , ' It will be obvious to those skilled in the art that various changes may be made in the inven in the appended claims. > in the ?rst named chamber, condensing it, and 1. A device of the kind described comprising a vessel having a compartment therein having a solution of a pure solvent and a nonvolatile solute dissolved therein, a second compartment having a body of pure-solvent therein under a pressure less than that in the ?rst named compartment, delivering it to the body of solvent in the other What we claim is: . chamber, the said membrane causing pure solvent to flow by osmosis from the body ofpure solvent to the, solution. . r 55 '1. A refrigerating system of the kind described comprising a boiler containing a solution of a a semi-permeable membrane separating the two . solute and a volatile solvent, a chamber, having bodies of liquid to-cause a ?ow of solvent by osmosis into the solution, means for boiling o? walls of semi-permeable membraneous material, in communication with the solution in the boiler, solvent from the solution and means for supply ing pure liquid solvent to the body of pure sol thermal means for circulating the solution‘ from vent. , 2. A device of the kind described comprising av vessel divided into two chambers by a semi-per 65 meable membrane, a concentrated solution of, a the boiler thru the said chamber, an evaporator, means for boiling off vapor from the solution, con densing it and delivering it to the‘ said evaporator, means for conducting refrigerantvapor from said 65 evaporator into surface contact with said semi solvent and a nonvolatile solute in one chamber, permeable membraneous walls while maintaining a less concentrated solution of the composition in said vapor under pressure appreciably lower than the pressure in said chamber, the solvent vapor being caused to ?ow by osmosis only thru the semi-permeable membraneous walls of the said chamber into the solution in said‘ chamber. KEMPER P. BRACE. the other chamber, and a third chamber vhaving a body of-pure solvent therein, the space above 70 said last named solvent being open‘to the space »_above the weaker solution to permit passage of vapor from said solvent to the said solution ‘to bev absorbed therein, the semi-permeable membrane ROBERT B. P. CRAWFORD. 70 .