US 3009684 A
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Nov. 21, 1961 MUNTERS APPARATUS AND METHdD OF CONDITIONING THE STREAM OF INCOMING AIR BY THE THERMODYNAMIC EXCHANGE WITH SEPARATE STREAMS OF OTHER AIR Filed Oct. 25, 1955 2 Sheets-Sheet 1 N PM 74 MOISTURE TRA NSFERRER p 10 1 we" 2 mans FERRER E Hr: AT
77 N Fa-R I- IN V EN TOR.
Carg fieo M iers Nov. 21, 1961 C. G. MUNTERS APPARATUS AND METHOD OF CONDITIONING THE STREAM OF INCOMING AIR BY THE THERMODYNAMIC EXCHANGE WITH SEPARATE STREAMS OF OTHER AIR Filed Oct. 25, 1955 FIG. 2
PSYGIROMETRIC (HART 2 Sheets-Sheet 2 100 HO I20 I30 DRY BULB TEMPERATURE F INVENTOR.
yl G /r9 Mwf/QIS B POUNDS OF WATER PER POUND OF DRY AIR United States Patent The present invention relates to improvements in air conditioning systems and more particularly to an apparatus and method of'treating the stream of air to be conditioned by thermodynamic exchange by separate streams or" other air. The invention is particularly applicable to a method wherein the incoming air is conditioned by thermodynamic exchange with the leaving air or exhaust air together with a separate stream of outdoor air, but is not limited thereto. The term thermodynamic exchange as used in the specification and claims is intended to include an exchange of sensible heat or an exchange of moisture with a resultant liberation or absorption of latent heat, or both.
The principal object of the invention is to effect air conditioning with substantial economy of power consump tion; to economize on the amount of energy required for the dehumidification and cooling of the air and to increase the co-efiicient of performance.
Another object is to provide an installation in which the dehumidifying means can also be used for heating and humidifying where conditions so require, for instance in Winter time.
A further object is to provide an installation that can be operated by a relatively economical source of heat such as gas, oil and steam.
The invention contemplates the use of an apparatus of the type in which the thermodynamic exchange between the difierent air streams is brought about by the use of one or more heat and moisture transferrers which move cyclically across the passages for the different streams of air. An example of such an apparatus is shown in U.S. Patents Nos. 2,700,537 and 2,723,837 to Pennington dated January 25, 1955, and November 15, 1955, respectively, but is, of course, not limited thereto.
The type of apparatus indicated comprises broadly the combination of a moisture transferrer and a heat transferrer, both of which may take the form of a wheel which rotates across the passages for the leaving air and the incoming air, respectively. These transferrers may, of course, embody some other form, the main feature being that they move cyclically across or between the passages for the difierent air streams. The combination may include a heating element for regenerating the moisture transferrer and an evaporator element or pad in one Or both of the passages for imparting to the respective :air stream or streams a predetermined temperature condition.
Moisture is first removed from the incoming air, i.e., the air to be conditioned, by exchange with the leaving air, i.e., the air leaving the conditioned enclosure, through the moisture transferrer. The thus dehumidified air is then precooled by exchange with the leaving air by the heat exchanger and finally adiabatically cooled or padded up to the desired temperature and relative humidity by an evaporator pad or similar element.
The leaving air having first been cooled or padded up by anevaporator pad or similar element removes heat from the incoming air by thermodynamic exchange in the heat transferrer. The thus warmed leaving air is further heated by the heating element to lower its relative humidity to a point below that of the incoming air so as "ice to impart to the leaving air sufficient power to regenerate the moisture transferrer. The foregoing description is given in general terms and the arrangement of the different component parts maybe subject to a variety of difierent combinations.
The present invention contemplates such an improved combination or cycle. Other examples of such improved cycles are shown in co-pendingapplication Serial No. 520,602, filed July 7, 1955, now Patent No. 2,926,502 granted March 1, 1960, in the name of Carl Georg Munters, the sole inventor herein, and Per Gunnar Norback.
The invention is illustrated by way of example in the accompanying drawing in which FIGURE 1 is' a schematic view of an installation according to the invention. j
FIGURE 2 is a chart which shows the psychrometric interaction of the air streams as they pass through the improved installation.
Referring to FIGURE 1, the installation shown therein is primarily designed for warm climates which require a reduction in temperature of the incoming air with consequent adjustment of the water vapor pressure in order to attain the desired relative humidity of the cooled air 'when it enters the enclosure.
Since temperature, humidity and air motion all influence the rate and mechanism of body heat loss, they can be logically optimum room conditions with high heat transfer co-efiicient and high humidity transfer 'co-efiicie'nt and g which can be easily regulated to meet different comfort conditions.
In the specific example described herein and plotted on the psychrometric chart of FIGURE 2, the outdoor air which in this case is the incoming air, is assumed to have a temperature of 95 F. and 40% relative humidity which should be conditioned to a temperature of ab0ut'66 F. and 70% relativehumidity in order to acquire sufiicient power to maintain a room temperature of approximately 78 F. to 80 F. and a relative humidity of about 50%. It should of course be understood that the installation is not limited to these examples. i v
It might be mentioned parenthetically that even in hot climates where the air has a comparatively low relative humidity, as in the example herein described, it has found desirable first to remove moisture from the infcoming air to still further lower its relative humidity to a point from which it may be anhydrously pro-cooled by exchange with the leaving air and thereafter may padded up to acquire the temperature and relative humidity to meet the predetermined com-fort condition. While it is recognized that the cooling of the air in such hot and dry climates might be attained by adding mois ture, for example by evaporating moisture into the inabout so Referring in greater detail to FIGURE 1 the room air or leaving air is exhausted through the passage 12 to the atmosphere by the action of the fan 10. It is cooled by passing through an evaporative pad 13 or similar element of conventional construction. The leaving air, or exhaust air, having been adiabatical-ly cooled by the pad 13, in turn cools the heat transferrer 14, itself becoming warmed in the process, and then passes through the moisture transferrer 16 where it heats and dries the hygroscopic packing thereof.
The incoming air, on the other hand, is impelled through two passages, 20 and 22 by the action of the fan 18. The passage 20 leads to the room or other enclosure whereas the passage 22 returns a portion of the air to the atmosphere after having passed through the heat transferrer 28 and moisture transferrer 24. The air flowing through the passage 20 first passes through the lower portion of the moisture transferrer 16 which moves cyclically across both passages 12 and 20, where moisture is removed and the temperature raised by thermodynamic exchange with the leaving air passing through the upper portion of the moisture transferrer 16.
The thus partly dried and heated incoming air is then passed through a second moisture transferrer 24 which moves cyclically across the passages 20 and 22, and becomes further heated and dried by exchange with the air treated in passage 22 which process will hereinafter be explained in greater detail.
The thus dried and heated air is then passed through the heat transferrer 14, which also moves cyclically across both passages 12 and 20, and in which the incoming air is cooled by exchange with the cool leaving air or exhaust air.
The incoming air may finally be passed through the evaporator pad or similar element 26 where it acquires its final psychrometric condition prior to entering the room or other enclosure.
The portion of the incoming air being impelled through the passage 22 in turn passes through the bottom part of the heat transferrer 28, and then after being heated by the element 30, through the bottom part of the moisture transferrer 24 which thus is regenerated. The still warm air then passes through the upper portion of the heat transferrer 28 where it transfers heat to the incoming portion of the air in passage 22 and which thus becomes preheated before encountering the heating element 30.
It may be pointed out that the heating element is not restricted to the location shown in the drawing. As indicated herein, the main purpose of the heating element is to increase the temperature of the air in the passage 22 so as to regenerate the moisture trausferrer 24. Thus it is conceivable that the heating element 30 may be located in the upper or outgoing portion of the passage 22 or in any other location where it can accomplish the designated purpose.
The heating element is preferably a gas heater of the type shown in Pennington Patent No. 2,700,537, but may, of course, consist of an electrically heated grill, an oil burning furnace or any equivalent heating means. The heating means may be augmented by radiation screens or shields, similar to those shown in the aforementioned Pennington patent, for the purpose of shielding the moisture and heat transferrer from direct rays from the heating means.
The heat transferrers 14 and 28 are presumed to be so constructed that they transfer principally heat and comparatively little moisture. The heat transferrers may with advantage be of the types described in my co-pending US. patent applications No. 442,686, filed July 12, 1954, and No. 387,656, filed October 22, 1953, both ap plications now abandoned, and are of the so-called regenerative type, i.e., an exchanger wherein one fluid passes in contact with the surface of a substance and gives oif heat to the same, whereafter another fluid passes into contact with the same surface and is heated. The
heat exchangers may be composed of fine wires or foillilre partitions, or may be packed with metal wool or similar material.
The purpose of the moisture transferrers 16 and 24 is, of course, to transfer moisture from one stream to the other. In order to attain as high a moisture transfer coefiicient as possible, these transferrers should transfer no or only an unappreciable amount of heat. The moisture exchangers which are also of the regenerative type and may be of the type described in my copending US. ap' lication No. 485,633, filed February 2, 1955, now Patent No. 2,925,880, granted February 23, 1960, and in US. application No. 485,633 filed February 2, 1955, in the names of Carl Georg Munters and Per Gunnar Norback, or it may be of the type disclosed in US. patent to Pennington No. 2,700,537 dated January 25, 1955, or any similar type such as that shown in my co-pending U.S. applications Nos. 442,686 and 442,687 filed July 12, 1954, both applications now abandoned. All of these exchangers are of the so-called regenerative type comprising a transfer element or elements which move cyclically across the streams between which thermodynamic exchange is desired. The moisture transferring mass may consist of a maze of wires or layers of foil-like partitions but preferably of a corrugated or moneycomb structure of ashestos paper or paper made of cellulosic fibers which in itself is somewhat hygroscopic in character but should be treated with a hygroscopic substance to increase its hygroscopic qualities. As examples of such substances may be mentioned calcium chloride, lithium chloride and lithium bromide.
Wliile continuously moving transfer elements may be preferable, intermittently or alternately moving transferrers may be used so that one is used to remove moisture while the other is being regenerated.
For a better understanding of the invention, reference is made to the psychrometric chart in FIGURE 2. For the purpose of the example, the incoming outdoor air will be assumed to have a temperature of 95 F. and a relative humidity of 40% which should be conditioned to a temperature of about 66 F. and a relative humidity of 70% in order to obtain optimum comfort condition in the room which should be about 78 F. to 80 F. and about 50% relative humidity.
In the psychrometric chart in FIGURE 2 the ordinate gives the absolute moisture content in pounds of water per pound of dry air. The abscissa gives the dry bulb temperature in F. and the curves give the relative humidity in percent. Psychrometric charts are, of course, well known devices for plotting the thermodynamic characteristics of the air streams and should not require any further detailed explanation.
The leaving air exhausted from the room will be assumed for the purpose of this example to have the psychrometric condition corresponding to point 34 on the chart, namely a temperature of about 80 F. and a relative humidity of 50%. The final psychrometric condition of the incoming air before entry into the room is represented by the point 36, namely a temperature of about 66 F. and a relative humidity of about 70%. These figures represent substantially the optimum values under the indicated climatic condition, but should not, of course, be taken as restrictive in any manner upon the application of the invention. The figures are given in round numbers for the sake of simplicity.
The adiabatic cooling of the exhaust or leaving air in the pad 13 is reflected on the chart by the enthalpy line 38 connecting points 34 and 40 which represents the condition 68 F. and relative humidity. This adiabatically cooled air while passing through the heat transferrer 14 removes heat from the incoming air stream in passage 20 and this heat absorption by the leaving air is reflected by the line 42 connecting the point 40 with point 44 which corresponds to a temperature of roughly 118 F. and relative humidity of 20%. The corresponding heat removal or anhydrous cooling of the incoming air in passage 20 passing through the bottom partof heat exchanger 14 is reflected by the line 72 connecting the point 62 corresponding to the psychrometric condition of roughly 124 F., 9% relative humidity, and the point 74, corresponding roughly to 74 F. and 40% relative humidity.
The exhaust air or leaving air, after having passed through the heat exchanger 14, is now sufliciently dry and warm to remove some moisture from the incoming air in passage 20 as the two streams pass through the moisture exchanger 16. This thermodynamic exchange is represented by the line 46 connecting the points 44- (118 F., approximately 20% relative humidity) and 48 (104 F., 37% relative humidity) with respeotto the leaving air, and by the line 50 connecting the points 3-2 (95 F., 40% relative humidity) and point 52 (108 21% relative humidity).
The stream in branch passage 22 passing through the bottomportion of heat exchanger 28 is heated by exchange with the outgoing portion of the same stream passing through the upper portion of the heat exchanger 28. This thermodynamic exchange is represented by the line 52a with respect to the incoming portion connecting point 32 (95 F., 4 relative humidity) and 54 (128 F., 16% relative humidity) and by the line 68 connecting the point 66 (131 F., 19% relative humidity) with point 70 (99 F., 48% relative humidity) with respect to the outgoing portion. Thus the incoming portion is heated against the cooling of the outgoing portion of the same stream which represents a considerable saving in power consumption. v
However, the thus pre-heated air in the incoming branch of the passage 22 must be further heated in order to acquire a sufficient low relativehumidity to remove the balance of moisture necessary to attain the final condition of the incoming air in the passage, 20'. This added heat represents the added energy input and is used to regenerate the moisture transferrer 24.j The heating process is :reflected by'the line '56 connecting the point 54 (128 F., 16% relative humidity) with the point 58 (153 F., 8% relative humidity).
As the heated air passes through the bottom portion of the moisture exchanger 24, it regenerates the latter and at the same time heats the incoming air passing through the upper portion of the moisture exchanger 24 to attain a temperature and relative humidity condition correspending to the predetermined final psychrometric function of the incoming air stream. This thermodynamic exchange is reflected by the line 64 connecting the point.
58 (153 F., 8% relative humidity) with point 66 (131 F., 9% relative humidity) with respect to air in the passage 22 and by the line 60 connecting the point 52 with point 62 (124 F., 9% relative humidity) with respect to the incoming air in the passage 20.
As previously stated, the incoming air is then cooled to the point 74 by thermodynamic exchange with the leaving air in the heat transferrer 14 and outgoing portion of the air in branch passage 22 gives off heat to the incoming portion of the same air in the heat exchanger 28 before being exhausted to the atmosphere at point 70.
It will be noted, however, that the psychrometric condition corresponding to the point 74 might difier from the predetermined final condition at point 36 and it is therefore necessary, in the example described, to pad up the air by the evaporator pad or similar element 26. This adiabatical cooling is reflected by the line 76.
Under certain temperatures and humidity conditions, the padding up might be eliminated, as will be understood by plotting on the psychrometric chart air streams having other psychrometric conditions and where the ap paratus is designed for other comfort requirements. In such case the added energy input will be still further reduced, as will be understood from the shortened line 60 which is equal in length to line 64. The shortening of given padding up of at least the leaving air was found necessary in order to obtain sufiicient driving p'owert For the sake of simplicity, the diagram in FIGURE 2 assumes a heat and moisture transfer effectiveness of the respective transferrers, i.e., only heat is transferred by the heat exchanger and only moisture by the moistureexc'hanger. If the transferrers should not be 100% effective, the points will be somewhat displaced. Thus if the moisture transfer along the lines 50 and 60 should be combined with some heat transfer betweenthe air streams then the point 62 would be displaced towards the right and the line 50-60 deviated accordingly. In actual practice transfer strictly along the enthalpy lines cannot be attained partly for the reason that the absorption heat is added to the vapor condensation heat and partly because of the inherent heat capacity of the transferrer mass. For the same reason the lines 38 and 76 will deviate from the enthalpy lines on the chart on ac count of the heat retaining capacity of the evaporated water. This deviation or lean should, of course, be considered in the design of the apparatus.
It will be seen from the foregoing that the moisture removal from the incoming air takes place in two steps represented by the lines '50 and 60, respectively. The first step is carried out by exchange with the leaving or exhaust air while the other is accomplished by exchange witha portion of its own air stream in the passage 22. By this thermodynamic exchange between portions of the same incoming air stream, considerable heat is saved as will be understood from the'relatively short line 56.
The amount of air passing through the two passages 12 and 20 per time unit may be about the same, but the amount in the passage-22 may be varied according to the condition.
As explained in Pennington Patent No. 2,700,537, the type of moisture transferrers used in the invention are capable of transferring-moisture from either air stream to the other by merely changing the rpm. The optimum rotation speeds differ somewhat for various materials, but can easily be determined experimentally for each.
The reason for the different speeds is that at low rotation speeds, moisture transfer takes place essentially from the cooler air stream to the hotter air stream, regardless of their humidity, whereas, at high rotation speeds, mois ture is transferred chiefly from the more humid air stream to the less humid one regardless of the difference in temperature between them.
The optimum slow speed for a fully impregnated moisture transferrer may be of the order of 3 r.p.m. but may vary between this speed and Vs r.p.m. or even less depending upon the type of hygroscopic substance and degree of impregnation.
The optimum fast speeds for the moisture transferrer as well as the heat transferrer may be of the order of 25 to 30 rpm.
The driving mechanism and speed change mechanism for the transferrers may be similar or identical with that shown in Pennington Patent No. 2,700,557 and should not therefore require any detailed description.
The evaporative pads 13 and 26 may be of conventional construction, as indicated. Water may be fed to the evaporators from a tank by means of a conventional pump and the tank may be supplied with water from any convenient source. This mechanism may be identical or similar to that shown in the aforementioned Pennington Patents Nos. 2,700,537 and 2,723,837. An evaporating air cooler of the type shown in U.S. patent to McKinney and Pennington No. 2,681,217 might also be used in place of the aforementioned pads.
The apparatus may also be controlled in a manner identical or similar to that shown in the aforementioned patents. Thus thermostats and humidistats which actuate electrical switches may be provided, as shown in these patents, to control the turning on and off of the pumps and the fuel valve.
In order to correct a possible problem of clogging of the transferrers, filter pads similar to those in the aforesaid Pennington patents or any other conventional construction may be added.
It should be understood that the foregoing description is given by way of example only and the invention may be subject to a variety of modifications within the scope of the accompanying claims.
What I claim is:
l. The method of conditioning the incoming air for an enclosure by thermodynamic exchange means which means are moved cyclically between a first passage means for the air leaving the enclosure and a second passage means for the air coming into the enclosure and between said second passage means a third passage means, which method comprises the steps of passing the air leaving the enclosure and heated and dried incoming air through a heat exchange means to thereby transfer sensible heat to the leaving air to reduce its relative humidity to a level below that of the unconditioned outdoor air, passing the thus heated leaving air through a moisture exchange means and passing outdoor air through said second passage means and also through said moisture exchange means to thereby transfer moisture from the incoming air to the leaving air, passing the thus dried incoming air through a second moisture exchange means moving between said second passage meansand said third passage means, passing extraneously heated auxiliary air through said third passage means to regenerate said second moisture exchange means while transferring heat to the incoming air, and passing the thus dried and heated incomingair through said heat exchange means to effectuate the transfer of sensible heat to the leaving air in the first step.
2. Method according to claim 1 in which the auxiliary air is first passed through a heat exchange means which is movable between an incoming portion and an outgoing portion of said third passage means prior to being heated and passing the auxiliary air from said second moisture exchange means through said outgoing portion and through said heat exchange means to thereby transfer heat to the incoming portion of said auxiliary air.
3. Air-conditioning apparatus having a conduit for the incoming passage of air and a conduit for the outgoing passage of air both for communication with a space to be conditioned; an auxiliary conduit for the incoming passage of air; means rotatable between said first and second conduits for thermodynamically transferring moisture; means rotatable between said first conduit and said auxiliary conduit and located indoorward of said first means for thermodynamically transferring moisture; said auxiliary conduit having portions directing flow of air in reverse directions; rotatable means for thermodynamically transferring heat between said portions located outdoorward of said second means for transferring moisture; said auxiliary conduit serially connecting one portion of said means for transferring heat with said second means for transferring moisture and with said other portion of said second means for transferring heat; means for heating said auxiliary conduit between said means for transferring and said second means for transferring moisture; means for impelling air through said outgoing air conduit; and means for impelling air through said incoming air conduit and said auxiliary conduit.
4. An air-conditioning apparatus according to claim 3 in which the auxiliary conduit branches from the firstmentioned conduit.
5. Air-conditioning apparatus according to claim 3 having rotatable heat transferring means between and communicating with the first and second conduits indoorward of both moisture transferring means, and having an evaporative air cooler located in each of the conduits indoorward of the last-mentioned heat transferring means in which the auxiliary conduit branches from the first-mentioned conduit and in which the air conduit branches from the first mentioned conduit outdoorward of the first means for transferring moisture.
Miller June 16, 1942 Pennington Jan. 25, 1955