US2327664A - Method of and apparatus for air conditioning - Google Patents

Description

Aug. 24, '1943. G. 1E] ons 2,327,664

METHOD OF AND APPARATUS FOR AIR CONDITIONING f Gera/d E. Offs Aug. 24, 1943. G. ET ons 2,327,664

METI'IIOD 0F AND 'APPARATUS FOR AIR CONDITIONING Filed Deo. 6, 1940 2 Sheets-Sheet 2 /Z FE1-z Z CJP 5 Gem/c7 .E 0775 Patented Aug. 24, 1943 UNITED STATES PATENTJOFFICE lvIETHOD F AND APPARATUS FOR AIR 1 CONDITIONING Gerald E. Otis, Moline, Ill., assignor to The Herman Nelson Corporation, Moline, Ill., a corporation of Illinois Application December 6, 1940, Serial No. 368,764

2 Claims.

The present invention relates in general to air conditioning and is concerned more particularly with an improved method and apparatus for by it is possible to maintain an agreeable and wholesome atmosphere under varying weatherv `greater part of the United States and in many other countries, outdoor air may be satisfactorily used for cooling and is thev principal medium employed in this invention.- In schools and other crowded spaces to which my invention is particularly adaptable, lthe independent heating effect of occupancy usually tends to create an indoor temperature considerably higher than the outdoor temperature, and artificial cooling may be effected by introducing and diffusing outside air in the space concerned. As will readily be appreciated by those skilled in the art, the outdoor air introduced may be precooled, Washed or otherwise treated, if desired, before entering the distributing apparatus illustrated, withoutA affecting the method of this invention. It is therefore evident that at the time I applied for this patentI foresawfurther utility of the method thereof, through the use of preconditioned air, and as will hereinafter appear, I have now devised a method and means for providing preconditioned air in such a way as to extend the utility of the method and apparatus of my above patent to year-round service under all weather conditions in a much more eicient and practical manner than heretofore employed.

The pronounced advantage of. Patent No. 1,913,681 lies in graduation of the outdoor air supply according to the actual duty imposed in maintaining a fixed thermal status of the air in the space served. A savingof more than fty percent in fuel consumption, over earlier conventional practice, was thus made possible in certain classes of heating and Ventilating work such, for example, as in the large and important schoolhouse eld where it is now in general use. The potency of this feature in this particular is conditioning the air of rooms in'buildings wherea comparatively large quantity of fresh air.

limited to the heating season, but were this.' its only advantage, the benefit during this period would, of course, be of great value inl yearround service. v Y

However, this feature has other advantages which are effective in summer as well as in winter conditioning service, and which take on an added value in year-round service. One of these is that gaduation of' a mixture of recirculated room air and cooler fresh air affords a simple, effective and reliable method of regulating the room temperature; and it is one which averts the danger of waste incurred by other methods through adverse functioning of the heating and cooling means in the transitional stage between heatingv and cooling duty. Another advantage lies in better humidity regulation throughout the year.

As pointed out in my earlier patent, the method thereof provides very little fresh air in cold weather, but increases the supply as the weather moderates. Since the moisture bearing capacity of air is limited by its temperature,v it follows that air normally contains much less moisture in cold weather than in mild' or warm weather, Hence, in cold weather, when the room air would otherwise tend to be quite dry, the moisture content is allowed to build up under the effects of occupancy, because little fresh air is circulated, whereas in mild weather, when the air naturally contains sufcent moisture, the effect of occupancy is nullied by circulating In this Way the room humidity is kept Within satisfactory limits throughout the heating season. And, where precooled air is used for summer conditioning, this feature is of special value in guarding against excessive humidity. To illus- Itrate, suppose the apparatus be designed to maintain a room temperature of 80 F. in warm weather, in a room where the circulation rate is 30 cu. ft. per minute per occupant and the duty requires that the air be introduced at F. If all the air introduced were preconditioned to 60 F., the relative humidity of the room would rise to 55%; but, if a mixture of one part recirculated air at F, and two parts of air preconditioned to 50 F. be used to obtain the required 60 F. mean, the relative humidity would be reduced to LLZ1/2%, which is a much better level. Moreover, under this method, the relative humidity will not vary so much under different load conditions and will be more in line with that maintained during the heating season.

i' While the present invention broadens the utilratus of a capacity to ity vof my patented method by providing improved means for supplying precooled air in accordance with the requirements of said method for summer cooling and year-around service, it also constitutes an improvement in heating and Ventilating (winter) service- A common difficulty in thermally conditioning rooms, under the normal range hof Weather conditions prevailing in the greater part of the country during the 4late fall, winter and early spring, is that appameet severe conditions is hard to regulate smoothly in average 'and mild weather; and failure to do so is liable to result in drafty room conditions. Through the present invention, the work is divided into steps which serve to overcome this difficulty.

Although the present invention is in the main directed to improvements in the method and apparatus of my United States Letters Patent No. 1,913,681, it is to be distinctly understood that I do not propose to thus limit its application, since it will be appreciated by those skilled in the art that the invention is susceptible of wide and general use.

Other objects and features of the invention will more fully appear from the following detailed description taken inconnection with the accompanying drawings, which illustrate a preferred I embodiment thereof, and in which:

Figure 1 is a combined vertical sectional view through a building floor and diagrammatically representing the arrangement of the apparatus of the 4present invention for carrying out my improved method of conditioning the room thereof; and

Figure 2 is an enlarged vertical sectional view taken through anindividual room-conditioning unit of a type adapted for utilization in connection with the present invention.

As shown on the drawings:

As shown in Figure 1, a room with means consisting, i room-conditioning unit 2, itself adapted, and so controlled by a room thermostat 3 as to carry out the method described and explained in my I is equipped this instance, of av United States Letters Patent No. 1,913,681. kIt is to be noted, however, that whereas it has heretofore been customary to locate theroom-conditioning unit on an outside wall of the room, and to take the required fresh air supply directly from outdoors through an opening in the wall, it will usually be found expedient, in the present instance, to locate the unit on an inner partition adjacent an immured branch conduit 4 adapted to supply preconditioned air. But, as will be understood by those skilled in the art, the location of the room-conditioning unit and the arrangement of the preconditioned air conduits will vary with circumstances and with the particular form of apparatus used.

Room-conditioning units of various constructions may be utilized to carry out the method, one suitable construction being shown in Figure 2. In this case, theunit consists of a suitable cabinet 5 adapted to be set on the floor, against a wall of the room served, this cabinet being provided with a fresh air inlet 6, a recirculating air inlet 'I and an air discharge outlet 8, The branch conduit 4 is connected to the fresh air inlet 6 to supply preconditioned air in the volumes required and at a sufciently low temperature to take care of the maximum cooling duty. The recirculated air inlet 1 and the communicate with the room or space served. It is preferred that these communicate with the discharge outlet 8 room directly, or as freely as possible, and that the outlet 8 be arranged to deliver the air into the room in the form of a substantially vertical jet with suihcient force to carry to the ceiling.

.The cabinet contains a motor driven fan 9, for drawing air through the inlets and discharging it through the outlet. The cabinet is also equipped with a radiator I0 for heating the air drawn through it, and with a filter II for cleaning the air. The arrangement is such that only the air drawn through the recirculation air inlet 7 is heated, but all of the air is filtered. However, it is to be understood that filtration is not essential to the method. Dampers I2 and I3 regulate the flow of air through the inlets 6 and 1, respectively, and are so linked together that one closes as the other'opens its associated air passage. A valve (not shown) controls the flow of steam to the radiator. The thermostat 3 controls the operation of the dampers I2 and I3 together with the radiator valve, in a manner and through mechanism well known in the art, so that on a rising room temperature within'a selected range the fresh air damper I2 is held closed (or to a fixed minimum setting), and the recirculated air damper I3 is held opened while the radiator control valve is gradually throttled through the lower portion of said range, after which the fresh air damper is gradually opened while the recirculated air damper isA correspondingly closed.- On a falling room temperature within said range, the operation is reversed. Of course, in either phase of the cycle, the room temperature, and hence the control mechanism, comes to rest whenever equilibrium is established between duty and output. As explained in Patent No. 1,913,681, certain modifications of the above-described cycle of control may be employed, but this will suice to illustrate the principle of the method thereof.

The effect of the patent method is to maintain an approximately uniform temperature in the room under varying weather conditions and the effects o f occupancy. In cold weather, the heat gains due to occupancy, sunshine, etc., are usually more than offset by heat losses through the outer walls, hence, the room temperature tends to fall and will be brought to rest at some point within the lower portion of the control range, where the fresh air supply is reduced to a minimum and the radiator control valve is open to supply enough heat to make up the deficit between the natural gains and losses. On the other hand, when conditions are such that the natural gains exceed the losses, the -room temperature would tend to rise and must be brought to rest in the upper portion of the control range, where the radiator control valve is shut and the dampers I2 and I3l are adjusted to recirculate less air and admit enough fresh air to neutralize the excess heat gain.

Notwithstanding outdoor primary factor in determining the duty on the system, it is not controlling. In many instances occupancy and sunshine impose a substantial cooling duty in comparatively cold weather. vThroughout a large portion of the year, circumstances permit of a wide range in cooling duty, and hence, in the quantity'of fresh air required. Where this air is drawn directly from outdoors by the room-conditioning unit 2, no problem is involved in connection with the supply. But, Where the supply must be drawn in Varying amounts from a limited source such as a separate preconditioning station,`a problem is introduced temperature is the damper size lof the units,

` drawsi'ts supply of air froms 'ageI1.- -The preconditioning chamber- I6, which 'may be of any suitable form-'and construction is pro'- vided with a heating element iii-regulating the available supply according to the demand. The present -invention is directed 'to a solution of this problem.

In certain instances it is feasible to equip each individual room-conditioning unit with additional preconditioning means, thus avoiding the problem cited, but in other cases it is not practicable, and it is rarely as satisfactory as protioning purposes, particularly where this involves precooling. The mere addition of a cooling coil in the type of room-conditioning unit shown in Figure 2 would not' be especially diflicult. As a l matter of fact, the same radiator could be made to serve for either heating or cooling by employing water as a circulating medium and heating or cooling the'water as required; However, the

adaptation of apparatus of this character to summer service is not so .simply accomplished.. A study of the regulating mechanism will indicate that it is not suitable for a radiator functioning in a cooling capacity. In order therefore to adapt room-conditioning units of the type required to carry' out the aforesaid method in summer service, it would be necessary to locate the precooling coil outside the port controlled by the I2 and provide additional thermo- Static regulation. 4In addition to greatly increasing the cost, this would-materially increase the unitsfor double service is complicated, unsightly and costly. Moreover, artificial cooling involves dehumidication, andfthis br'ngs up a'sanitarydrainage problem vthat is not easily disposed'of.

4Thepresent invention provides -an arrangement'wherein the simple unit system of my which is'itself often objectionother closes.

earlier patent, with its manifold advantages, is

used for conditioningrthe rooms themselves, while a central plant is employed to properly .prepare or precondition the air supplied, as'v required, to the room-conditioningunitsl In other words, the amount of fresh air required and circulated 'by the room-'conditioning units 2, while the Aaggregate amount pared and distributed asrequired, by a centraliA demanded is prepreconditionin'g plant. Referring again to -Fig- -electric motor or other chamber I 6` through` "a suction conduit orpas- I8 and/or cooling.

is forcdjby a-fan` or blower |5. The fan 'is,^of course, driven by an` suitablemeans and..

a preconditioning to maintain an op-y vtimum"condition in'each room,A under varying ,Weather andoccupancy conditions,.is. regulated u re -1, each roem-conditioning .unit 2 is supplied' AIl -from a trunk w I4 into and through ment 2l while the required air supply flows into the preconditioning chamber through the intake duct or passage 22 which communicates with the receiving compartment 20 and is arranged to to regulate the ow from the two sources as desired.

Wherejair is taken from within the building,

l it should preferably bedrawn from some quarter, such as a main corridor,'which is not itself equipped with conditioning units 2 but into which air from the rooms' so equipped may overflow, either through suitable vents or by` leakage. In such cases, the complete circulation process may be facilitated by either allowing about an inch clearance under doors between such roomsand the corridors, or, by providing vents in the lower rails of the doors or in the corridor partition. .An arrangement which has been found satisfactory is shown in Figure 1, wherein the room I -is vented into the corridors through an oifset vent 26 which communicates at its lowermost end with the room at a point near the floor and at its uppermost end with the upper region of the corridor.

The air supplied to the preconditioning chambers should never be drawn wholly from within the building except when the rooms are unoccupied, unless the outdoor temperature is higher than that to be maintained in the delivery'compartment 2I. When the outdoor temperature is lower. than that to be maintained in the delivery compartment, only enough air should be drawn from outdoors-to allow the temperature of the mixture to be at or below that to be maintained in the delivery compartment. To provide for this,4 the dampers 24 and 25 may be linked up to operate in unison so that as one opens the These dampers may be controlled by'a thermostat 21 so as to maintain a lixed temperature in the receiving compartment 20, which will be at or below that maintained in the delivery compartment 2I lsc long as the outdoor temperature is below that point and the-indoor supply source temperature is above it. This will insure that only so much raw air will be used in cold weather-as may be required to provide for proper ventilation of the rooms; and, that during warming up periods, when the building is itself cold,I all air will be recirculated.

The abovedescribed arrangement should 'be vsuch that -the thermos'tatic control' mechanism,

21 operates against a spring 23' or other force tending tot hold the outdoor damper 24 closed and the indoorsupplydamper 25 opena conventional .arrangement well understood in the art. Said-thermostat mechanism 21 in response to'air temperature conditions -in `the receiving compartment-2J), normally functions within a Aselected temperature range, when theternperatureis rising through that range, to gradually open the damper 24` and correspondingly close element I9 which serve Ato subdividev the chamber 'f fanis communicates with the deiivery comparifinto a receiving compartment 20.' anda delivery -The. suction passage -I 1 tothe the damper 25 against thetension` ofthe spring 23'. Alternatively, when the temperature in the `receiving compartment 20 isfalling, within the selected temperature' range, said thermostat mechanism 21 operates toallow said spring'23 to gradually close the damper 24 and correspondingly op'en the damper 25. ySo long as the ter nperature in the receivingl compartment 20 remains "constant Vatisome point within the se-V 4- lected control range, the thermostat 2'I acts to maintain `the dampers 24 and 25 in whatever intermediate position the dampers may be.

A leakstat or similar limiting device 2,8 responsive to tion at a point representative of the indoor supply source temperature, is utilized to render the thermostat 21 ineffective and allow the outdoor damper 24 to close and the indoor damper 25 to open whenever the outdoor temperature exceeds that at the indoor supply source. the refrigeration load will be kept to a minimum.

The air-heating element I8 and the air-cooling element I9 are indicated diagrammatically and may be'of various forms well known in the art. For the purpose of explaining the invention, it will be1 assumed that the heating element I8 consists of the usual steam radiator and that` the cooling element I9 is a radiator or coil adapted to the use of a suitab-le refrigerating agent, such as ammonia, freon, etc. It will also be further assumed that the necessary equipment is provided to render these elements serviceablel in their respective capacities, all of which is well understood in the art. It will be understood that both elements are only necessary for yearround service, and, that either may be omitted or the two functions combined in one element without affecting the broader phases of the invention.- On the other hand, humidiers, lters, ozonators or other preconditioning devices may be added, if desired.

Valves 29 and 30 or other suitable means are provided to control the respective heating and cooling elements. 'I'hese valves may be regulated through suitable thermostatic means 3l placed in the delivery compartment 2I or other appropriate point to maintain a limited range of temperature of the preconditioned air. For example, with the pneumatic system of control, an intermediate, direct-acting thermostat 3I- may be used to control a direct-acting steam valve 29 and a reverse-acting refrigerant valve 30 so that, at the lower limit of the control range the steam valve will be wide open while the refrigerant valve will be closed; and so that, as the temperature of rises above said lower limit, the steam valve will gradually close up to some selected point within the range where it will be fully closed; and so that when the temperature of the preconditioned air exceeds said selected point, either critically or by some arbitrary margin, the refrigerant valve will gradually open until the temperature rise is halted.

A by-pass duct or passage 32 affords communication between the air passages on the suction and delivery sides of the fan.

In the arrangement shown, which is commonly known as a draw-through arrangement for theY reason thatthe air is drawn rather than forced through the preconditioning chamber, the by-pass is preferably connected between the trunk duct I4 and the .receiving compartment 20. As will be understood by those skilled in the art, a so-called blow-through arrangement might be substituted, wherein the intake duct 22 would connect with the suction inlet of the fan I5 instead of with the receiving compartment 20, the suction duct I1-in this case being omitted and the fan arranged to discharge into the receiving compartment. With such an arrangement, the trunk duct I4 would merely become an extension of the delivery compartment 2I or it might be omitted, and the branch ducts outdoor temperature and set to func- In this way,v

the preconditioned airv 4 extended separately from the delivery compartment. In the latter case, the by-pass 32 will connect the intake passage 22 with the trunk duct I4 or delivery compartment 2I.

The by-pass 32 is preferably provided with a damper 33 which may be regulated so as to maintain a uniform pressure in-the trunk duct I4 through the agency of a static pressure regulator 34. Under a maximum demand for preconditioned air to supply the various room-conditioning units 2, the regulator will close the damper; but, as the demand falls off the static pressure will tend to rise and cause the regulator to gradually open the damper 33 until the tendency ceases. In this way, a constant pressure of properly preconditioned air is made available to meet the varying demands of the room-conditioning units at all times. The pressure regulator 34 and even thedamper 33 may be omitted with fairly satisfactory results where the distributing system is not too complicated and is well proportioned; but, in such cases, the by-pass 32 should be taken from a point near the far end of the trunk duct I4. The by-pass need not be the full size of the trunk duct, but should be large enough to handle the difference between the maximum and minimum supply of preconditioned yair required at various times by the room conditioners.

Ordinarily, the maximum supply of preconditioned air required to serve the various room conditioners will be considerably less than the aggregrate peak demands of same, and should be independently estimated on the basis of the actual maximum demand of the group at any one time. For example, the requirements of the units serving e'ast rooms will be greatest in the morning, whereas those of units serving West rooms will be greatest in the afternoon. In a building exposed alike on opposite sides, the load factor may be as little as half the required maximum output of the individual units collectively.

It is evident that with the arrangement described, a uniform temperature of preconditioned air is made available in the quantities demanded to maintain optimum conditions inthe various rooms the year around. The entire system operates automatically to this end without further attention than such adjustment of the room thermostatsas may be required at different seasons, and to maintain a proper supply of steam in weather when it is necessary. As is well understood in the art, the refrigeration equipment may be arranged to operate automatically in response to the demand. Ordinarily, a temperature of about -55 in the trunk duct I4 will -serve this purpose best. The optimum room temperature. for occupants customarily clothed and, sedentarily engaged will vary from about iT-'72 in winter, to 7880 in summer.

It is, of course, to be understood that although I have describedv in detail a preferredembodiment of my invention, the invention is not to be thus limited, but only insofar as defined by the scope and spirit of the appended claims.

I claim as my invention:

1. Air conditioning apparatus comprising a -housing having an outlet for conditioned air and separate intakes for air from an outdoor and an indoor source respectively, a damper for each of said intakes, means normally biasing one of said dampers to closed position and the other to open position, mechanism for operating said dampers in unison so as to close one while opening the other, thermal air-conditioning means thermostatic of said thermal air-conditioning means for actuwithin said housing, means for moving air through said housing from said intakes past said thermal air-conditioning means to said outlet, means within said housing ahead ating said damper operating mechanism, temperature responsive meansin the outdoor intake operable to render said thermostatic means ineffective when the temperature of the air in the outdoor intake exceeds that in the indoor intake', a by-pass from said outlet to said housing ahead of said thermal air-conditioning means, a damper in said by-pass and pressure responsive means in said outlet for controlling said by-pass damper to maintain a substantially` uniform air pressure at said outlet irrespective of the demand for conditioned air from said outlet.

2. 'I'he method of thermally conditioning air,

which comprises moving air along a confined path providing intakes into said path from a source of indoor air and from a source of outdoor air, thermally conditioning the intaken air at a point along said conned path, controlling the selection of the source and of the proportionate Volumes of air taken in from said sources in accordance with the relative temperatures of the outside air and of the intaken air at a position ahead of said point of thermal conditioning but. beyond the points of intake, advancing said conditioned air under a pressure head for delivery and by-passing any excess. of such conditioned air over delivery demand back to said conned path ahead of said point of thermal conditioning so as to maintain said pressure head substantially constant.

GERALD E. OTIS.

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