US2667766A - Method of balancing steam consumption in air conditioning - Google Patents

Description

W. W. CUMMINGS METHOD OF BALANCING STEAM CONSUMPTION Reb. 2, 1954 IN AIR CONDITIONING Filed OCb. 29, 1948 2 Sheets-Sheet l Feb. 2, 1954 w, w. cuMMlNGs METHOD OF BALANCING STEAM CONSUMPTION IN AIR CONDITIONING 2 Sheets-Sheet 2 Filed Oct. 29. 1948 Patented Feb. 2, 1954 METHOD OF BALANCING STEAM CONSUIWP- TION IN AIR CONDITIONING William Warren Cummings, Bradford, Vt. Application October 29, 1948, Serial No. 57,6325

9 Claims. (Cl. 62-176) This invention relates to a method of balancing steam consumption in air conditioning which makes possible savings of 40% or more in operating costs over conventional air-conditioning systems.

Air-conditioning in large commercial installations usually involves lcontrolling both the temperature and the humidity of the air to provide substantially uniform conditions at all times. Air ltering to remove dust and dirt and sterilization are incidental. Complete control of temperature and humidity of course, requires heating the air, as well as cooling it, and adding moisture to the air, as well as extracting it from the air. Heating, however, is normally done separately, and independently of the cooling of the air,4 and not at the same time.

Air-conditioning as described herein involves both temperature control (by heating or cooling the air) and humidity control (by adding mois` ture to, or extracting it from the air, as needed). Currently in many large commercial installations, the cooling of the air is done by means of an electrically driven refrigerating compressor,

which supplies refrigerant to pipes over which the air is passed, and the moisture is extracted from the air in an entirely separate process, by chemical sorbents, such as activated alumina, calcium chloride, lithium chloride, silica gel, triethylene-glycol, andv the like. The sorbents, however, must be renewed or reactivated from time to time by extracting the moisture from them in turn, which is done by heating the sorbent. Normally, of course, in cooling the air by refrig eration, moisture will be extracted from the air.

-But this is a haphazard consequence of the cooling, when natural humidity fluctuates widely from time to time, and cannot be used for accurate control of both temperature and humidity without the use of reheat. For instance, to secure a desired humidity, over-cooling of the air may be necessary to remove the required amount of moisture, and then the air` will have to be reheated to restore it to its desired temperature. Occasionally, in recent installations, chemical sorbents have been used separately to effect humidity control, but this has necessarily been without relation to temperature control. If temperature and humidity control is sought by use of chemical sorbents alone, the control of either cannot be accurate except in a narrow range since the two conditions bear no normal xed relationship to each other, but fluctuate widely in nature.

M The two processes olf` temperature and humidity control are therefore, necessarily separate and 2 distinct operations and are usually separately powered, and by different operating media. Occasionally, if the steam plant is available, the refrigerating compressor is driven by a steam turbine, from which the steam is allowed to exhaust, or it may be condensed and fed back to the boiler. I am also aware that this same steam has been used also to reactivate the sorbents. But it has never before been thought possible that the steam requirements for these two separate uses of the steam for refrigeration and reactivation of sorbents could be balanced, because of the great variations and fluctuations between natural ternperature and humidity conditions at different periods of the year. I have, however, discovered that by using steam for powering both the cooling and dehumidifying operations (i. e. in the latter operation, for reactivating the sorbent by removing the moisture therefrom, after the sorbent has removed the moisture from the air) the steam requirements for the two operations can be balanced,v so that the requirement for low pressure or exhaust steam for removing the moisture from the sorbent is always equal to the requirement for high pressure steam for operating the refrigerating unit. The result of using the same steam for these two purposes in this manner is a great saving in operating costs, of 40% or more, amounting to many thousands of dollars per year in large installations.

Briefly, my' invention consists in cooling the air by means of a steam driven refrigerating unit (compressor and condensor), dehumidifying the air by chemical sorbents below the designed relative humidity, reactivating the chemical sorbents to remove the moisture therefrom by the exhaust steam from the refrigerating unit, and automatically spraying moisture into the dehumidied effluent air stream to restore its designed relative humidity, which provides an evaporative cooling action in the air, and further reduces the sensible heat load on the refrigerating unit. In this manner the requirement for low pressure exhaust steam for dehumidifying the air (i. e. reactivating sorbents and removing the moisture therefrom) is always equal to the requirement for high pressure steam for cooling the air (i. e. driving the refrigerating unit), and steam is not wasted, as it otherwise would be. In other words, to maintain this balanced steam condition, the sorbent side is operated at peak capacity at all times up tothe -limit of the exhaust steam furnished by the steam-driven refrigerating unit. With the sorbent side' operated at full capacity, which capacity is greater than required to maintain the designed humidity, more moisture will be taken out than is required for the designed humidity. The humidistat will then be energized to open sprays in the eiiiuent air stream at the absorber unit, thus adding moisture to the air stream. This added Water when evaporated into the air stream results in a conversion of the heat of vaporization to cooling the air stream. This in turn absorbs heat from the area, which reduces the steam requirements for operating the refrigeration unit and further reduces the supply of exhaust steam available for reactivating the sorbent.

area is reduced, resulting in a rise in relative humidity in the area.

spray of moisture into the eiliuent air stream from the absorber.

sorbent side of the systenr throughsevaporative cooli'ngaction,` of.` the sprayed moisture. and the temperature and humidityorthe controlled' area tends to rise.4 The entire load'l of. heat removal' is their thrown on: the refrigerating unit, which requires more steam to operate it, and in turn provides. more exhaust. steamv to reactivate vthe sorbent. to a higher concentration land thus removeumore moisture from the air stream, and reduce. the-relative humidity to the desired level. When. the relative humidity again drops below the desiredlevel", thexhumidistat again opens the spray, thus completing the cycle. Thus, regard.- less of thechange in= temperature and humidity requirements-j, the system will at all. times` arrive at a steambal'ance, wherein allthersteam exhausted Vfrom thefrefrigerationunit: will be fully utilizedin. the reactivation. of'the sorbentno more and no less, thereby: accomplishing two integrated uses ofthe same steam.

Before explaining in detail the present invention it is to Vbe understood` that the invention is notlimited in itsapplication tothe details of construction and` arrangement of partsl illustrated in the accompanying drawings; since the invention is: capable of othernembodiments andi of being practiced or carri'edfout in various ways. Also it i's to beV understood' that-the phraseology or terminology employed herein is for the purpose of description and not. or limitation, and it is not "i lintendedl to limit. the inventiony claimed herein beyond theA requirements .of the prior art.

InV the dra-Wing.:`

Less moisture is then removed from ther-sorbent; and its capacity to absorb moisture in the controlled When the humidity rises to the desired degree, the humidistat-shutsoff theY With the spray shutoff;` there is no longer any heat removal from the operating the cooling system steam passes through pipe 2| to steam turbine 22 at proper pressure, i. e. generally 240 to 300 pounds per square inch. The turbine 22 in turn drives the compressor 23 of the refrigerating unit 24 containing a suitable refrigerant such as Freon (dichloro-difluoro-methane) and a part of which is thecondenserZ. As these are standard refrigeratingfunits" their structure need? not be described in detail.` The refrigerantV is directed to I the heat exchanger 25 through suitable coils Eig.. 1i isi-a diagram of an. installation utilizing A my method of air conditioning:

units t5 by fans It which force the airy across coils or pipes; l?, through.` which chilled water is circulated., These. Cooling; units.l are preferably arranged on the. ceiling. of. the controlled area. I

A. steam. boiler 2 0 provides; the steam for operating tout, me cuori-ng, and densa-ramas. systems-if For Ht represents an air inlet; for outside air 5i therethrough by pump 3u.

where it is used to chill Water which is the coolirigonedlium,1 as shown in the diagram. The chilled' Water is then piped, as through pipes 28 to the cooling units I5 Where it is returned through return pipe 29, being caused to circulate A modulating valve 32 controlled by a thermostat 33 regulates the iiow of'thechilled Water through cooling unit I5. The cooling water for the ,condenser 25 is passed throughA Apipe 316- torf the) cooling tower Sbeing pumped therethrough. :byfpumo: 3-6 and; isxthen circulated through pipe 3:1 tothe. absorber lfrand returns through pipes 38- aud 39 to the condenser 25. At the same time cooling Water is bili-passed to the :heat exchanger 261 through; pipes ftand returned through: pipe 42 to pipe 319..

The" dehumidiiying system: is .also operatedy .by the exhaust, steam:v from; steam turbine 22:'which aetuates the cooling; system; previously described. Low pressure exhaust steamztoi 8. to-.10. :pounds per square inch) aterfoperating: steam turbine 22 passes through' pipe 4:4fto thevliqudi. sorbent reuctivatorr t5?, Where .the steam rused to. reactivate the sorbent in: the reaetirator 4 5 tof extract the moisture therefrom, andftnus restore the'sorbent qualities of the sorbent liquid. Wherntlie relative: hul'nidityv offthevcontroll'ed area.; reaches apoint belote thedesigned relatorey humidity the humidistat; Elli" automaticall'y causes'. atomizod waterA to. be sprayed intoY the dehumidied eilluent air` stream through atomizerit controlled: by Value 5.2, water being;suppliedV- thereto vfrom any suitable .sourcevr through pipe..n 531'.' It should. Ybe understood thatv standard humidistats. operate Within; a. fixed plus oriminusrangeof a desired setting, and: iffor instance the desired `relative humidity is 50% the humidity-of. thefcontrolled area .would dropftozapproximately 458:% before thefhumidistat would operate,.and thus:l actuate the valve-52cm. the atomizer- 5k. The addition of this moisture. in atomized form to the entering air stream provides an, evaporative cooling: action on 'the air itself' which 'reduces its 'temperature and lessensthe loadA on, the cooling .system including the refrigerating unit, 24 and cooling unit iti and. the steam required cooperate the 'refrige erating'unit 24; supplied throughftheturbine- 22.

Agaim when. the,E relative humidityirisesto the desired` degree, thehumidistat will shut oir the spray of moisture:intoI theair` stream. Thus the sorbent side'oi the vsystem no longer removes heat', and thel load ori-1 the: reirigerating inuit` increases, requiring; more steam. to operate it, and

thus providing more exhaust steam .to reactivate liquid, sorbent is. used. Outside air again isv in-` troduced through; the air inlet 63 and; room 'air inlet, stthrouglrlter E2 to:.absorber..63 for the solid sorbent, which again extracts moisture from the air and thus dehumidies the air. rThe air Yin turn passes out into the controlled area through duct 64 being forced therethrough fan 65. Again an alternate humidistat 'l0 automatically introduces atomized water into the entering air stream through atomizer 1I, valve 'I2 and Water pipe 13. Similarly an alternate thermostat 'I5 controls the ow of air through the cooling units I5. Again exhaust steam after passing through turbine 22 and thus operating the refrigerator unit 24 and cooling units I5, passes through pipes 44 and 'I8 to reactivator 80, where sorbent qualities of the solid sorbent are again restored by the use of low pressure steam. The exhaust steam or condensate is then returned to the boiler through pipe 8|. The alternate dehymidifying steam using a solid sorbent operates in all respects similar to that of the dehumidifying system using the liquid sorbent previously described. Again as the relative humidity reaches a point lower than the designed relative humidity atomized water is sprayed into the dehumidied air stream through atomizer 'I I, which again provides an evaporative cooling action in the air and thus reduces the flow on the cooling system and hence the amount of steam supplied to operate steam turbine 22. Regardless, therefore, of the variation between the cooling system and the dehumidifying system, the requirement for low1 pressure or exhaust steam for removing the moisture from the sorbent, and thus operating the dehumidifying system, is always equal to the requirement for high pressure steam for driving the refrigerating unit, and thus operating the cooling system. It will be understood that in Fig. 2 the dehumidifying chamber for solid sorbent 63 replaces the absorber I3, that temperature and humidity controls 'I5 and 10 replace equivalent controls 50 and 33, as shown in Fig. 1, when using liquid sorbent, and that the outside air is brought in through inlet 50 instead of I0 (in Fig. 1) and that the room air is brought in through inlet SI, instead of inlet Il (Fig. 1).

By Way of illustration, my method of balancing the steam requirements for cooling and dehumidifying air may be determined in the following manner. The natural state or condition of .the air in most climates, of. course, iluctuates widely, so far as the relationship between temperature and humidity of the air is concerned, Y

.relative humidity. The desired relationship for industrial methods and processes will, of course, vary indefinitely. But with the natural weather conditions varying constantly, it is obvious that under previous methods in use, that the plant requirements for cooling and dehumidifying the air will not normally balance, and that the steam supply would necessarily have to be provided to take care of the maximum or extreme conditions which may be encountered. This necessarily results in high operating costs for plant requiren ments. Operating costs for refrigeration systems, whether operated electrically or by steam, are approximately the same, and average about 11,/4 cents per ton hour. The seasonal steam requirements for cooling the air (i. e. sensible heat removal) however, is normally in excess of that required for operating the dehumidifying system (through reactivation o the sorbent).V The excess steam, if ,not usable in industrial processes,

6 is either exhausted to atmosphere or condensed at additional cost. If the refrigerationsystem is electrically driven, it is obvious that the steam must be specially generated :for reactivating the sorbents of the dehumidifying system. Assuming a total heat problem requiring .100 tons lof refrigeration, and using steam of 240 pounds per square inch to drive the steam turbine which operates the refrigerating unit, and a back pres-` sure on the exhaust steam from the turbine of 8 to l0 pounds per square inch, the steam requirements are 2500 pounds of steam per hour, at an operating cost of $1.25 per hour. This cost is approximately the same as that of an electrically driven turbine, or 11A; cents per ton hour. Assuming a 60-40 proportion for peak loads as normal, the original 100 ton refrigeration load is broken down into 60 tons for the sensible heat load (cooling the air) and tons for the latent heat load (dehumidifying the air.) To obtain a constant steam balance, the equipment is sized for the total heat problem requiring 100 tons of refrigeration, by providing a 60 ton compressor driven by a non-condensing steam turbineinstead of the 100 ton unit which would normally be provided in the conventional and unbalanced system. The remaining 40 tons of the 100 ton refrigerating load is then applied to the ydehumidifying system which is sized accordingly. If then the latent heat load of the dehumidifying system is of the designed heat latent load, only 50% of the designed capacity of the absorber is needed to reduce the moisture in the controlled area to the designed relative humidity, reflected by the standard humidistat. When the designed relative humidity is attained, the humidistat automatically operates a valve which sprays atomized water into the dehumidified air stream. In so doing, evaporative cooling occurs in the air, which inturn lessens the sensible heat load on the cooling system. In theexamples stated, thus 50% or 20 tonsof cooling is accomplished by the dehumidifying system. Thus tons of sensible heat removal is accomplished by the cooling unit, plus 20 tons of sensible heat removal accomplished by the dehumidifying or latent heat removal system. This' makes a total of tons of sensible heat removal and a normal 20 tons of latent heat removal, totalling 100 tons of refrigeration, and this is accomplished by the use of steam normally capable of only 60 tons of sensible heat removal in conventional air-conditioning systems. l

The'sensiblev heat removal Vsystem thusA automatically synchronizes with the latent heat removal system, taking only the minimum 240 pounds per square inch steam required to effect a complete condensation. Any decrease in the actual latent heat load over the designed capacity of they dehumidifying equipment increases `the capacity of the latter for assuming part of the sensible heat load. This reduces the sensible heat load on the cooling system and it results in ya substantial saving in operating costs through `be operated for only.75 cents per hour per tons of accomplished refrigeration. i 1n industry .installations .-accomplishingv1000 tons ci refrig- 'I eration-.per hour, are: not Y. unusual.. The `yearly operating costs; oconventionai air conditioning Systems average approximately $15.0'pe1 year per tn 0f refrigeration. For a 10,00 ton refrigeration system the savings'are atleast $60,006 per year. In addition,y remarkably accurate temperature controlis possible by, my method and control' of anarea with less'than l degree lF. temperature dierence at any one point throughout the area has been commonly experienced- I claim:

v l. The method oi air conditioning which combines the cooling and humidicationy of air in a. balanced steam operated ldual system utilizing asteam turbine driven refrigerating compressor suppl-ying refrigerant tol a. cooling elementl wherein'water is cooled, cooling the air by bringing it into heat exchange with the cooled watery` removing-the moisture from the'air by'means of chemical sorbents.. reactivating the chemical sorbents by utilizing; the exhaust steam .from the compressor v unit and automaticallyl spraying moisture into the dehumidified air until the dcsired relativehumidityhas been reached, to pro.- vide an evaporativel cooling action and to further reduce the sensible heat load on'the reirigerating compressor.

2. The method of air conditioning which balances the steam requirements for effecting cooling andA humidilication of the air a steam operated dual system including a steam driven refrigerating compressor-.supplying refrigerant to a'coolingrelement wherein water is'` cooled, cooling the air by bringingitinto4 heatV exchange with the ,cooled Water, removing. the moisture fromthe g air by means, of chemicalsorbents, reactivating the chemical sorbents for dehumid-ifying, the air by utilizing the exhaust steam from the refrigeratingcompressor unit, and automatically sprayingmoisture into the dehumidied air until'. the desired relative humidity has been reached to provide an evaporative cooling action land to fur,- ther reduce the sensible'heat load on the refrig- Verating compressor. y

3. 'I he method of air conditioning which combines the cooling and humidicationof air in a balanced steam operated., dual system utilizing a steam driven refrigerating compressor supplying .refrigerant to a cooling; elementV where-in, Water is .cooled,. cooling thev air by .bringingstinto heat exchange with the cooled Water-removing the moisture from the airby means of cl'iemcal sorbents belov.1 the designed relative humidity, reactivating thc-chemicalsorbents byutilizing the vexhaust steam from Ythe refrigeratingcompress` sor unit,l and automatically spraying moisture into the dehumidied air tot restore it `to itsv designed relative humiditypand to provide an evaporative cooling action and to further reduce the sensible heat load on the refrigerating compressor.

4.1 The method of air conditioning which balances the steam requirements for eecting cooling, and humidii-lcation of the air in a steam operated dual system; utilizing a steam driven refrgerating compressor supplying refrigerantV to a. cooling elementywherein Water is cooled,` coolingthe air by bringing it intoheat exchange with the. cooled water, removing. theA moisture from the airby'means of chemical sorbents below the designed relative humidity, reactivating the 'chemical sorbents. for vdehumidifying the .air by utilizing the exhaust: steanrfrom the lrefrigeratingfoompressor'unu and` ,automatically spraying moisture. into the dehumidied air to restore it, to

its designed relative.hmnidi-ty.and te provide evaporative cooling.; action and to, further reduce the sensible; heat lead on therefrigeratingxcompressor.

5. The method of `air conditioning which com.- bines the cooling and humidication. affair in a balanced dual steam operated system utilizing a steam driven rcfrigerating compressor supplying refrigerant to a cooling; element wherein wa;- ter is cooled, cooling theairrby bringingzit into heat exchange with the cooledyvater;removing moisture from the air-iu `excess of the; designed relative humidity by means ofv a chemical sorbent unit having av designedv capacity greater than normally required', Vreactiva-ting the. chemical sorbents by utilizing theexhaust steam from the refrigerating compressor unit, and;` autoi matically spraying moisture into. the dehumidiiied air stream to. restore it` to its desired relative humidity, and thus provide an evaporative cooling actionin thercontrolled. area tov further reduce the sensible heat load on thefrefr'ifgerating compressor.

6. The method of airconditioningwhi'ch come bines. the cooling and humi'dification of airin a balanced steam operated dual system utilizing a steam turbine driven refrigeratilng compressor supplying refrigerant to a cooling element Wherein Water is cooled, which methodinclud'es cool-- ing the air-by bringing it Ainto heat-exchange with the cooled water; removing moisture lfrom the air in excess of the desired relative humidity by means of a chemical sorbentunit having`v` a designed capacityA greater thanno-rm-all-y'- required, reactivating the chemical sorbents by utilizing the exhaust steam from the refrigerating compressor unit, and-automatically spray ing moisture into the dehumidied air stream' to restore'it to its desired rela-tive humidity; and thus provide an evaporative cooling action inthe controlled area to further-v reduce the vsensible heat load onthe refrigerating compressor.

7. The method of- "air Iconditioning Which com-,- bines the cooling and humidiication of air in a balanced steam operated dual system` utilizing a steam turbineA driven refrigerating compressor supplying refrigerant to acoolingelement Wherein Water is cooled which method includes 'cooling the air by'bringing it into heat exchange with they cooled Water; operatingV atv peak capacity a chemical sorbent unit having a designed dehumidifying capacity1 greater than'normally required, removing moisture from the atri-nexcess of thc-desiredV relativel humidity, reactivate ing the chemical sorbentsby `utilizing the ex'- haust steam from the refrigerating compressor unit, and automatically sprayingmoistuieinto the dehumidiied airstream to'restore itto its desired relative humidity, and thus providean evaporative cooling action in the controlled14 area to further reduce theV sensible heat'loa-dvon th refrigerating compressor.

8. The method of air conditioning which combines the cooling and humidieation of air in a balanced steam operated dual system utilizing a steam turbine driven reirigerating compressor supplying refrigerant to a cooling element Wherein Water is cooled', cooling the air by' bringing itr intov heat exchange with the cooled Water, removing the moisture from the air by means .of chemical sorbents'reactivating the chemical 'sorbents Vby utilizing theexhaustfsteam from the refrigerating compressor unit, and automatically spraying moisture into the dehumidied air whenever the relative humidity of the controlled area drops below the desired level, to provide an evaporative cooling action in the controlled area.

9. The method of air conditioning which combines the cooling and humidication of air in a balanced steam operated dual system utilizing a steam turbine driven refrigerating compressor supplying refrigerant to a cooling element wherein Water is cooled, cooling the air by bringing it into heat exchange with the cooled water, removing moisture from the air in excess of the desired relative humidity by means of chemical sorbents, reactivating the chemical sorbents by utilizing the exhaust steam from the refrigerating compressor unit, and automatically balancing the steam requirements for cooling by resaturating the excessively dehumidified air, whereby the absorbent portion of the steam supply may be converted to sensible heat removal in proportion to the excess of the moisture removal.

WILLIAM WARREN CUMMINGS.

10 References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Article entitled Newspaper Puts Exhaust to Work in magazine Powerf August, 1938, pages 15 50 and 51, Figure 3.

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