US 2167878 A
Description (OCR text may contain errors)
Alm- 1 w39- R. B. CRAWFORD 2,167,878
AIR CONDITIONING SYSTEM Aug. 1939. R B CRAWFORD ZG'B'B l AIRCoNDlTIoNING SYSTEM Filed Feb. 19, 1936 2 Sheets-Sheet 2 WQKK (RI I, f
J6 J0 J3 f5 Patented Aug. 1, '1939 UNITED STATES PATENT OFFICE 6 Claims.
This invention relates to air conditioning systems and methods, and among other objects, aims to eliminate wasting of Water and to'save power by employing the refrigerating or heating elect of the earth or of ground water, which is returned, after absorbing or yielding heat, to b'e used again. Other objects will be understood from the following description of two different installations which are within the scope of the invention and by either of which the method of the invention may be practiced.
In the accompanying drawings forming part of 'this specication;
Fig. i is a diagrammatic sectional elevation oi an installation employing circulated. ground water for either cooling or heating;
Fig. 2 is a similar view of an. installation of a different type employing a hygroscopic chemical which is circulated in a circuit comprising the earth and air cooling apparatus.
Referring to Fig. 1, there is shown an air conditioning system which will dehumidify and cool the air to be treated. In some localities, hot ground water in almost unlimited quantities is available, and in such places, the system with some obvious modifications may be for air conditioning and heating. In most parts oi the country, however, the temperature of the earth at depths of, say, 25 to 100 feet below the ground level, is nearly constant, Winter and summer, and will average around 50-60" F. The earth at this temperature is a heat transfer medium of suillcient magnitude to absorb all the heat removed in the process of conditioning air in even a large building; hence a system employing a subterranean channel, as in Fig. l, is most useful as an air conditioning means in hot weather, though useful in all seasons, if in cold weather heat is supplied to the conditioned air.
In the system of Fig. 1, air conditioning apparatus is provided having a capacity sumcient to deliver air at the desired temperature in the necessary volume, at the hour of greatest demand on the Worst day of the year (from the standpoint of atmospheric conditions) with a maximum internal load arising from crowded rooms, lights, sunlight' and other heat sources. In order to dehumidify the air properly, it is usually necessary to cool the air by refrigeration to a teinperature which is too low for delivery directly into the area to be conditioned. To provide the reheating oi the air which is necessary for less than the maximum load and for proper dehumidiiying when refrigeration is used, and to gain the equivalent energy on the cooling cycle, the water circulated from the subterranean area is used to heat the air. After the water has thus been reduced in temperature (by air reheating) in the arrangement of Fig. 1, it is further cooled by refrigeratlon and is then used to cool the air coun- 5 ter-currently. Finally, before returning the Water to the subterranean channel, it is heatedV as by absorbing heat from the condenser of the refrigerating system, thus assuring a higher temperature to the returning water than the subterranean channel has. This means that the subterranean area always does part of the cooling, which part can be the sensible part of the Work.
According to this invention, a heat transfer channel in strata of the desired temperature is created for continuous circulation of a fluid preferably of high speciiic heat, such as water or brine. Not only is energy below the desired temperature level used but the added heat energy above this level is put back into the system and all the circulating fluid isA conserved. The system to be described is particularly advantageous when all the air introduced into the system is from the outdoors, thus effecting a saving in the amount of the refrigeration equipment needed. When employing the apparatus for heating, the reverse cycle system covered in my copending application Ser. No. 18,685 filed April 27, 1935,
' Patent 2,135,742, issued November 8, 1938, is used.
Referring particularly to Fig. 1, there is shown a building '.i having a room t to be air conditioned and basement room l in which most of the necessary apparatus is set up. Somewhere below the level of the footings t there will be a stratum 9 of permanently moist earth, clay or rock which is either below the permanent water table or which may be an artificially created perched Water table. In the stratum 9, in accordance with the invention, an excavation is made and a large conduit or other artificial directed channel I0 is 40 built in the excavation, preferably by the Well known shield process. Preferably the conduit or channel Ill is lined with precast concrete blocks Ia and openings Il are left at various points in the length of the conduit so that water from the stratum 9 may gravitate into the artificial channel and maintain the same iilled or saturated with water.
The conduit or channel it may be Wholly lled with coarse gravel or broken bricks l2, though Ait 5d is shown as only partly filled, with screens i3 confining the masses of gravel etc. to certain portions of the channel.v The purpose of the gravel is to 4cleanse the Water by removing clay, debris, etc., and particularly to increase the t transfer capacity Aof the conduit. If desired, the gravel may be in several layers, screened and graded to size. In any event, the gravel should increase the flow of the water through the subterranean channel, so that the Walls of said channel may dissipate the heat of the water at a high rate.
A submersible pump I4 driven by motor I5 takes the water from the delivery end of the channel II) and hoists it through pipe line I6 to the machinery room 1. Here pipe line I6 (which may be termed the cool water line) is preferably connected by a valved pipe I 1 to the house service pipe I8 which supplies the system initially with water. When the motor and pump assembly is to be repaired or serviced it may be lifted out of the channel I0 through a manhole I9 extending down from the floor of room 1. Motor t5 is controlled by a switch (not shown) in the machinery room, and hence the rate of circulation of the water in the system may be varied according to needs.
The air to be conditioned enters the building through inlet near the ground level controlled by weatherproof vanes 2|, and it passes through a conduit 22 because of the draft induced by suction fan 23 driven by motor 24. The iiow of air through the system should be controllable, and the motor 24 and vanes 2| afford operatorcontrolled means to increase or decrease the air flow to anything desired. -As the air travels through conduit 22 it is dehumidied, cooled and reheated by apparatus to be described and then goes to the suction fan 23. Then the conditioned air is blown through a conduit 25 which extends up through the walls of the building to the room or rooms 6 where the conditioned air is needed.
When the air is to be cooled as well as conditioned, the conduit 22 contains or is connected to air cooling means comprising a plurality of refrigerating coils 26 which are part of a refrigerating system which also includes a condenser 21, a compressor 28 and a motor 29. The compressor 28 delivers the compressed refrigerant through pipe 30 to the condenser 21, where the refrigerant is liquefied and then delivered to a liquid line 3| and past an expansion valve 32 to a cooler 33. From the cooler the refrigerant is returned by the pipe line 34 to the compressor 28. Expansion valve 32 may be of the thermal type actuated by a bulb 49g on the suction line 34. 'I'he refrigerating coils 26 are connected to the cooler 33 by pipe 35 so that a continuous supply of cold water at approximately 50 will pass through said coils. As the air is brought into contact with the cooled coils it is dehumidified and the water thus extracted is collected by a drip pan 36 which has an outlet pipe 31 controlled by a check valve 36. An eductor 39 is connected with pipe 31 and is also connected with the coils 26 by means of a pipe 40 likewise provided with a check valve 4|. Water flows from the eductor 33 through the pipe 42 to the condenser 21 where it is heated, the hot water then moving down pipe 43 into the receiving end of the channel or conduit I 6.
The cooled water from pipe line I6 is forced by pump I4 through the pipe 44 which conducts the water to the air reheatlng coils 45 located in the duct 22. Here the water is cooled a couple of degrees and then enters the water cooler 33 by means of pipe line 45a. If desired the water may be by-passed around the reheating coils 45 by means of a pipe line 46 leading directly to the cooler 33 and controlled by a threeway valve 46a. Valve 46a. is controlled by a thermostat 41, which is preferably located in one of the rooms whose temperature is to be cooled by the conditioned air delivered by the system. Thermostat 41 will regulate the flow of water through the reheatlng coils 45 and if no reheating is desirable under the temperature conditions in the room the thermostat 41 will by-pass the coils 45 whereupon the entire flow of water will -be directed through pipe 46 to the cooler 33. It is also desirable as shown to provide a by-pass line 48 controlled by a hand-valve 49 and a check valve 49a and connecting the pipe line 44 with the ,pipe 42.
To insure a higher fluid temperature in pipe 40 than in pipe 44, a matched thermostat 46h,
relay 49c and valve 49d are provided. When the temperature at thermostat 49h is 80, for example, valve 49d should be wide open. Should the temperature of the outdoor air be reduced, the temperature at thermostat 49h would fall, valve 49d would gradually close, and would be closed tight when the temperature at thermostat 43h fell below the temperature in pipe 44 by a small amount. This is necessary to insure getting the maximum heat removal from the air at the intake with the'l minimum refrigeration and power input to the motor 23. The desired temperature (50 or thereabouts) in cold water line 35 is maintained by varying the speed of said motor or by starting and stopping multiple compressor units (not shown) by motor 29. A thermostat 43h in cold water line 35 controls motor 28 by a thermostatic switch 49i. The water temperature in line 42 as sensed by thermostat 43h can be calibrated by matched umts or setting of thermostat 49h can be varied by outdoor thermostat 43e or by fluid thermostat 43f.
Referring to Fig. 2, there is shown a system which, While using the refrigerating and/or heating effect of the earth as a source of energy, employs a closed fluid circuit, that is, a circuit having no inlets or outlets for ground water. Such a circuit is obviously independent of a supply of ground water, and hence the water-tight conduit 50 may be buried in stratum 6| which is perfectly dry. In this conduit, coarse gravel or the like 52 is confined by screens 53, or it may fill the interior of the conduit, which thus has a high heat transfer capacity. A quantity of a hygroscopic aqueous brine 54, for example sodium chloride or calcium chloride brine, is introduced' into the circuit of which the conduit is a part and is circulated and recirculated by means of a submersible pump 55 driven by motor 56 controlled from the machinery room 1 by a switch (not shown). A manhole 51 permits hoisting of the pump and motor assembly out of the conduit and a pipe 56 conducts the brine from the conduit to the contactor 53.
The discharge end of pipe 53, which may be termed the cool brine pipe, has a series of perforations 66, or a sexies of perforated pipes (not shown) causing the brine to be discharged into the interior of contactor 56 in a series of ne streams. 'I'hese fine streams fall upon a heterogeneous medium 6| which may be a mass of broken tile, coarse gravel or any material not reacting with the brine which will further break up the brine spray before it passes down over absorbent tubes 62 (or sheets, if preferred). The viscosity and surface tension of the brine are such as to make it adhere to the heterogeneous medium 6| until it makes contact with the tops of the tubes or sheets. The tubes or sheets are spaced apart uniformly by spacer 63.
'I'he air to be conditioned enters the building 5 through an intake 64 controlled by vanes 65 and passes through conduit 66 because of the suction of motor-driven fan 61. The discharge side 68 of the fan forces the air into the lower end of the contactor 59 and thence the air passes up between the tubes or sheets, then through a mass of glass wool 69 and nally up to the distributing duct 10 into the room or rooms 6 to be air-conditioned. As the air passes up through the contactor, some of its heat and moisture is taken up by the brine. The heat picked up by the solution is the thermal equivalent of all the work done on the air; consequently the brine which returns to the conduit 50 (as will be described) carries all the heat and losses exactly as does the water in the system of Fig. 1.
At the bottom of contactor 59, a pipe 1I which may be termed the warm brine pipe, is provided to carry away the warm and weaker brine resulting from contact with large volumes of the atmosphere. To maintain the concentration necessary to do the work, a concentrator 12 is provided. A thermostat 13, or else a Dunlap density controller (not shown) actuates a threeway valve 14 to direct the weak brine to the concentrator, from which concentrated brine ows down to the conduit 50 through return pipe 15. 'I'he brine is concentrated to a strength greater than is desirable at the upper end of the contactor 59, and this excessively concentrated brine is mixed with more or less weak brine from pipe 16, as permitted by three-way valve 14so that the brine returned to conduit 50 is of exactly the right strength for the atmospheric conditions and the load on the system.
The concentrator may be thermal, electrochemical or electro-endosmatic as described in my copending applications.
Ii a thermostat 13 is used, rather than a density controller, it controls the concentration by a calibration of known surface and transfer conditions in the contactor with given conditions in the contactor with given conditions at the air inlet 64 as sensed by controller 11. This controller may be a dew-point thermostat. awet bulb thermostat or a combination eiective temperature controller, as required by the conditions at 64 and 10. Controller 11 resets thermostat 13, acting through a relay 19, for the known temperature for a given heat and moisture duty, so that thermostat 13 can in turn bring about the degree of brine concentration necessary for eiilcient operation of the system under light loads.
The walls oi the conduit 50 preferably are serrated, grooved and ribbed, or otherwise shapedv to insure a maximum heat transfer, but they should be substantially brine tight.
It will be clear that the systems of Figs. 1 and 2 may be used to deliver large volumes oi.' conditioned air to the interior of a building, and that the use of expensive, noisy and ugly cooling towers is entirely obviated. Furthermore, the systems require no large supply of water, 4thus effecting important operating economies particularly in cities where water is metered. Both systems are notably economical. to operate and to maintain, and neither requires a huge investment.
Obviously the present invention may be practiced with systems differing in many particulars from the ones shown and described herein for illustration.
Having described the improved method and two air conditioning systems embodying my invention, what I claim as new and desire to secure by Letters Patent is:
1. An air conditioning system comprising in combination a subterranean conduit positioned below the water table and having openings providing direct contact of the fluid therein with ground water; a refrigerating system including a cooler and a condenser; a duct for conveying air to a point of distribution, a cooling coil in said air duct; and means for circulating water successively through said conduit, the cooler of the refrigerating system, the cooling coil in the air` duct, the condenser of the refrigerating system and back to said conduit.
2. 'I'he invention according to claim 1, wherein there is an air-reheating coil'through which the water flows on its way to the cooler, and past which the air ows on its way to the point of distribution.
3. The invention according to claim 1, wherein the conduit is at least partially lled with inert material to increase the turbulence of ow and hence the heat transfer and to remove certain impurities from. the water. l
4. The invention according to claim 1, wherein the water system has a coil in the air duct, for reheating the air after dehumidiiying, and a bypassl around said coil, with a thermostaticallycontrolled valve governing the amount of flow through the by-pass and coil.
5. The invention according to claim 1, wherein the dehumidifylng coil has a drip pan, and a pipe leads from the drip pan to an eductor, said eductor being in the water-circulating system, so that water extracted from the air enters the watercirculating system.
6. The invention according to claim 1, wherein the refrigerating system has an electric motor and a compressor driven by said motor, a thermostat being in the cold water line from the discharge side of the cooler, a thermostatic switch governingthe motor, and means connecting the thermostat and said switch, so that the motor iis governed by the temperature in the cold water ROBERT BRACE CRAWFORD.