US3169575A

US3169575A - Evaporative heat exchanger

Info

Publication number: US3169575A
Application number: US148254A
Authority: US
Inventors: Jr John Engalitcheff; Thomas F Facius
Original assignee: Baltimore Aircoil Co Inc
Current assignee: Baltimore Aircoil Co Inc
Priority date: 1961-10-27
Filing date: 1961-10-27
Publication date: 1965-02-16
Anticipated expiration: 1982-02-16

Description

1965 J. ENGALlTCHEFF, JR., ETAL 3,169,575

EVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 6 Sheets-Sheet 1 REFRIGERANT m AIR DISCHARGE L 26 21 w t f I 1 )f' i I I l6 INVENTORS John Engolitcheff, Jr.,

Thomas F. Facius TTORNEY' Feb. 16, 1965 J. ENGALlTCHEFF, JR., ETAL EVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 AIR DISCHARGE 6 Sheets-Sheet 2 T WATER iii? il FLT? l W J.

l l- I- I! REFRIG. 1"

OUT

fae

MAKE-1 INVENTORS John Engulitcheff, Jr.,

Thomas F. Facius ATTORNEYS Feb. 16, 1965 J. ENGALITCHEFF, JR, ETAL. 3,169,575

EVAPORATIVE HEAT EXCHANGER 6 Sheets-Sheet 3 Filed Oct. 27, 1961 is E23 5:; z;

INVENTORS John Engaliic'neffldn,

Thomas F. Fqcius Feb. 16, 1965 Filed Oct. 27, 1961 TEMPERATURE J. ENGALITCHEFF, JR., ETAL 3,16

EVAPORATIVE HEAT EXCHANGER 6 Sheets-Sheet 4 'Zl- REFRIGERANT REFRIGERANT CONDENSING B SUPERHEAT REMOVAL sus-coouuc AND SOME CONDENSING 0F REFRIG. IN EXTERNAL HEAT EXCHANGER \HEATED SPRAY wATER SPRAY WATER FROM EXTERNAL HEAT KM/ EXCHANGER AIR INVENTORS John Engalitcheff, Jr.,

Thomas F. Fucius BY m,fiw,w m TTORNEYTS 1965 J. ENGALITCHEFF, JR., ETAL 3,169,575

EVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 6 Sheets-Sheet 5 SPRAY J CHAMBER I COIL SECTION AIR INVENTORS John Engoli'rcheff, Jr., Thomas F. Fucius AIRIN ATTORNEYS Feb. 16, 1965 J. ENGALITCHEFF, JR., ETAL 3,169,575

EVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 6 Sheets-Sheet 6 SPRAY FROM CHAMBER TUBE-40o COILSECTION J4} I LIQUIDIN ANNULAR SPRAY WATER m INNER PIPE TEMPERATURE INVENTORS John Engolitcheff, Jr. Thomas F. Fqcius agww fiw mgm ATTORNEYS United States Patent EVAPDRATIVE I-EAT EXCHANGER John Engalitchefi, Jr., Gibson Island, and Thomas F. Facials, Baltimore, Md, assignors to Baltimore Aircoil Company, Inc, Baltimore, Md., a corporation of Maryland Filed Oct. 27, 1961, Ser. No. 148,254

7 Claims. (Cl. 1651) This invention relates to evaporative' heat exchangers and more particularly to methods and apparatus for extracting heat from fluids in operations such as the condensing of refrigerants and/ or the cooling of liquids.

In an evaporative condenser, the fluid from which heat is sought to be extracted is circulated through a coil or tube bank which is disposed in a chamber which has a water reservoir or sump at its bottom. The apparatus is provided with means for flowing air upwardly around the coil while water from the sump is pumped to the top of the tank and sprayed downwardly from a spray tree in droplets which fall countercurre'nt to the air flowing over the coil. The air circulating counter to the droplets causes a measure of evaporation of the water and the latent heat necessary to support this evaporation is taken from the fluid in the coils.

Now, in a system of the type described above, the spray water leaving the spray tree and before it begins to contact the coil section containing the fluid from which heat is to be extracted, is cooler than the air which has been moving upwardly through the coils to cause evaporation; Accordingly between the spray tree and the beginning of the coil section, the air which is leaving the f of water.

tures of the spray water and the air that the spray moving down to the coil section "will be cooled by the counterfiowing air leaving the system rather than/taking up heat from that air. 7

it is an object of the present invention to provide an evaporative condenser or other, heat exchanger of improved thermal efiiciency which is characterized by the capability of maintaining an appreciable temperature dif-' ference between the flowing water spray and counteriiowing air in'the region between the spray header and thecoil. j The present invention olfersthe advantage that by its use the heat extracting capacity of [an evaporativeconi denser or heat exchanger of any given size is increased so thatif the present inventionis applied toan existing installation it will increase its cooling capacity] Of course, if the same cooling capacity is desired then, with the present invention, it can be achieved with smaller equipment. a

Other objects and advantages of this invention will be I apparent upon consideration of the following detailed description of several embodiments thereof in conjunction with the annexed drawings wherein:

FIGURE 1 is a schematic yiew in vertical sectionof an evaporative condenser constructed in accordance with the principles of the present invention to incorporate aheat exchanger through which the spray water passes and. is

preheated on its way to the spray head, the heat 'exchang or being physically separate from the condenser casing; FIGURE 2 is a view in vertical section, showing'a It is proposed according to the present invention .to 4

eliminate this waste and so to adjust the relative tempera-' ice in the various regions of a sytsem such as that shown in FIGURE 1;

FIGURE 5 is a view similar in that of FIGURE 4,

but showing relative temperatures of the heat exchange media in various zones of a in FIGURE 2;

FIGURE 6 is a view similar to FIGURE 3, but represystem such as that shown 'senting the relative temperature curves of air, spray water,

and fluid to have heat extracted therefrom where the coil contains aliquid which is being cooled by the extraction of sensible heat as distinct from latent heat;

FIGURE 7 is a graphic representation ofthe relative temperature of air, spray water and liquid to be cooled under conditions which would prevail if the apparatus of FIGURE 1 were used to cool a liquid rather than to condense a refrigerant gas; and g p FIGURE 8 is a view similar to FIGURE 7 but showing the relative temperature curves for air, spray water and a liquid to be cooled as these would be iri the various zones in the apparatus of FIGURE 2 if'that apparatus a were'used to cool aliquid rather thanto con-dense a "refrigerant.

casing 10 there is provided'a reservoir or sump 11 for.

spray water, and reservoir is maintained at a predetermined level by makeup water supplied by a conduit 12 througha float valve 13 of conventional construction controlled by, a float l4. Waterfrom the reservoir. 11 is withdrawn by a pump 15 through a conduit 16 and delivered-through a conduit 17 to a heat exchanger diagrammatically indicated at 18. The cooling water is one phase a conduit 21, gives up some'of its heat'to the spray water, and leaves through conduit 22 from which it is delivered to the coils v23 inthe casing 10. ;The condensed refrigerant leaves the-condenser through conduit 24. The

refrigerant .is only partly cooled in heatexchanger l3, but the principal condensing of the sanie'takes place: in

the coils 23. To this end, the cooling water is sprayed over the coils 23 in droplet form and the water'tempera .ture is kept low by evaporation induced by air flowcaused by a fan 25 which pumps air'vertically upwardly through the casing 10 countercurrent to the spray'water which is falling by gravity. -Drift eliminators 26 catch the water in the air which leaving the system and return it to the system.

Above and below the coils'23'there are located

wet dech sections

26 and 27. These wet decksections are merely groups of corrugated metal sheets disposed in mutually parallel relation in such a way as toicollect water. on

their surfaces' for evaporation by the, air passing ithere across. This, of course has the'fefiect of cooling the' water droplets flowing to and flowing from the coils 23. a

' its own air exhaust duct In FIGURES 3 and 4 there are set forth curves representing relative temperature changes which occur in evaporative heat exchangers; The curves of FIGURE 3 represent the conventional heat exchanger while those of FIGURE 4 represent the heat exchanger of the present invention. In FIGURE 3 there is diagrammatically represented a spray tree 30, a coil section 31, a sump 32 and a fan 33. In actual structures these are arranged vertically, but in FIGURE 3 they are diagrammed horizontally to correlate the apparatus with the temperature curves.

The abscissa of these curves represent position in the system, while the ordinates represent temperaturerising in the direction of the arrow. The refrigerant entering the top of a conventional system contains some superheat. This is extracted in the upper part of the coil section. Thereafter, heat of vaporization is extracted as the refrigerant changes from gaseous to liquid phase, and then, at thevery bottom of the coil section 31, a small amount of sub-cooling occurs.

Nowin FIGURE 3 where there is no heat exchanger such as heat exchangerlti, the air enteringthe spray chamber zone is the hottest air in the entire system, see the right side of FIGURE 3. The water is at about the temperature prevailingin the reservoir32, and it has been found that this temperature is regularly and appreciably below the temperature of air leaving the uppermost pass of the coils 31. Obviously, if the air is warmer than the water, the water will cool the air and then this air will be forthwith vented to atmosphere. 1 Aside from this waste, the temperature difference between air and spray water does not get to a desired level until the spray water has progressed a fair distance into the coil system.

On the other hand with applicants improvement the spray water is not led from the reservoir directly to the spray head 20, but instead is first passed through the heat exchanger 18. The effect of this is set forth in FIGURE 4 which is a diagram made in the same fashion as FIG- URE 3 to show graphically the advantage of the construction of FIGURE 1 over the'prior art the function of which is set out in FIGURE 3. In FIGURE 4 the parts which appear diagrammatically bear the reference numerals of the equivalent parts in FIGURE 1. paring FIGURES 3 and 4 the advantage of passing the cooling water through the heat exchanger 18 on its way to the spray tree is graphically apparent. Note that the spray Water in passing through heat exchanger 18 has its temperature raised from level A to level B, see FIGURE 4, so that the water entering the spray'tree 20 is much warmer than' the air leaving the casing 10, with the result. that the entering Water is cooled and the leaving aircon- 4 As shown in FIGURE 4 condensation may commence in the heat exchanger 13.

In FIGURE 1 the achievement of the rise in temperature of the cooling water before its entry into the spray trees 20 is accomplished'by a heat exchanger which is physically separate from the evaporative condenser casing. In FIGURE 2 there is shown a ve-ry-eflicient arrangement wherein the preheating of the cooled water is accomplished first by flowing it countercurrent to the refrigerant as the inside phase of a dual heat exchanger, the outside phase of which is between the refrigerant and the spray of cooling water from the spray trees.

In FIGURE 2 the evaporative heat exchanger casing is defined by numeral 33; A fan 34 is provided to pump air substantially vertically through the casing from bottom to top. At the bottom of the tower there is a water reservoir or sump 35 provided with a fioat operated make-up valve generally designated at 36. Cooling water is withdrawn from the sump 35 through a pipe 37 leading to the intake of a pump 38. The pump 38 delivers the water through a conduit 29 which enters the inner tube 49a of concentric tube heat exchange coil 40 through a suitable end fitting 41. Through a similar end fitting 42 the cooling water leaves the coil 4%) and is delivered by a pipe 43 to spray tree 44. The coils 49 are fed with refrigerant through a conduit 45 leading to the outer tube 4% of the coil 43. The refrigerant is withdrawn through a conduit 46; The refrigerant circulates in an annular zone through the coil 4tisurrounding the tube 40a which contains the coolant water, the outer surface of the refrigerant tube 49b being exposed to'the cooling droplets of water issuingfrom the spray trees 44. It will be noted that the water is flowing upwardly through the coil 49a I counter to the downward flow of the refrigerant to be condensed in tube 4%. On the other hand, the spray issuing from the spray trees 44 is. flowing generally'concurrently with the refrigerant to be condensed wh-ileboth the spray and the liquid to be cooled are flowing countercurrently to the air. Drift eliminators 47 similar in structure and function to eliminators 26 are provided at the top of the casing 33.

Wet deck sections

43 and 49 are provided, section 48 being between the spray trees 44 and the coil 40, and section 49 being between the coil 46 and the sump 35; Thesesections 43 and 49 correspond respectively in structure and function to

sections

26 and 27 shown in FIGURE 1. 1

The effect of these wet deck sections is to improve the air-water contact thereby to increase evaporation of the water and to improve the amount of cooling that can be accomplished per unitlength of fall of the cooling water. FIGURE 5 is a diagrammatic illustration in the style of FIGURE 4 but is prepared to show the relative temperature curves for the refrigerant, the spray water and By com- 7 the air as they move through the apparatus of FIGURE 2. The diagrammatic parts of the system of FIGURE 5 bear the same numbers as have been assigned to those parts in FIGURE 2. The broken line indicates the spray water V tinues to pick up heat with the result that the water at the moment of commencement of spray is already, and continues to be all the way through the coils 23, much warmer than the air which is cooling it. The increase in the temperature of the spray water entering the spray chamber would, of course, not result in increased efliciency except for the factthat the heat which causes the rise from its entering temperature as shown in FIGURE 3 to the entering temperature as shown in FIGURE 4 is derived from the material to be cooled, i.e. the refrig-' erant. This material has the superheat removed'before it enters coil 23 with the result that the amount of condensing per unit of surface of the equipmentis increased.

in the inner pipe during the preheat operation. Note that it is preheated from a sump temperature indicated at .A to a spray tree temperature indciated at B and that A is much lower than the airtemperature at C although thethat this superheat is dissipated much more rapidly thanin conventional apparatus dueto the fact that the refrigerant is having heat extracted from both the inner and outer surfaces of its annular. path. a

, f Of course, in the condensation of a refrigerant, a temperature curve representing heat extraction is a straight linesince there is no change in sensible heat, the extracted heat going to bring about a change in state, i.e., from gas to liquid. Accordingly, the refrigerant curves in FIG- URES 3, 4, and 5 are essentially straight lines. The apparatus of the present invention is, however, quite suitable for cooling liquids, i.e., the extraction of sensible heat from a liquid. In FIGURES 6, 7, and 8 there are shown temperature curves quite similar to those shown in FIG- URES 3, 4, and 5 respectively except that the fluid from which heat is extracted is a liquid rather than a gas. The curves of FIGURES 6, 7, and 8, therefore, represent the change in relative temperature which occurs in extracting heat from a liquid which stays in liquid phase throughout the entire passage through the coil section. FIGURE 6 represents the prior art evaporative heat exchanger as it deals with the cooling of a liquid. FIGURE 7 represents the apparatus of FIGURE 1 used for cooling at liquid or other fluid as distinct from condensing and FIGURE 8 represents the use of the apparatus of FIGURE 2 for cooling instead of condensing. By studying the temperature curves of these figures it can be seen that the advantage of passing the cooling water in heat exchange relationship to the incoming material from which heat is to be extracted applies regardless of whether the heat is extracted for the purpose of reducing the sensible heat, i.e., the measurable temperature of a fluid, or for the purpose of bringing about a change of state.

While wet deck sections are shown in both of FIGURES 1 and 2, these are operational to the system and may be removed if desired. The heating of the entering spray water with the entering fluid to have heat extracted from it increases the entering temperature of the spray water as shown in FIGURES 4 and 7, and thus establishes a larger than conventional temperature difference between the air and the spray water, this temperature difierence has a counterbalancing effect on the smaller temperature difierence between the fluid in the coil 23 and the spray water. In this section of the evaporative heat exchanger using the heated spray water from the external heater 18, there is only a small reduction in capacity as compared to the same section of a conventional heat exchanger (10%15%). The external heater accounts for additional capacity as much as 40%50%. This results in a net gain of approximately 35% more capacity than a conventional evaporative heat exchanger. The use of the double pipe heat exchanger shown in FIGURE 2 results in additional capacity as compared to the FIGURE 1 system. In the case of FIGURE 2, there is a larger temperature difference between the spray water and the fluid in the annular space. This is because the fluid entering the double pipe coil is at its highest temperature.

What is claimed is:

1. The method of improving the efliciency of evapora tive heat extraction that comprises as the first step in extracting heat from a fluid that has absorbed heat, passing said fluid to have heat extracted therefrom and a cooling liquid in mutual heat exchange relation without evaporation of said cooling liquid and then passing the same fluid and of all said liquid in mutual heat exchange relation while evaporating at least a portion of said cooling liquid.

2. The method of improving the efliciency of evaporative heat extraction that comprises as the first step in extracting heat from a fluid that has absorbed heat, passing said fluid to have heat extracted therefrom and a cooling liquid in mutual heat exchange relation without evaporation of said cooling liquid and then passing the same fluid and of all said liquid in mutual heat exchange relation while evaporating at least a portion of said cooling liquid by direct contact with a counterflowing air appreciably cooler than said cooling liquid at the beginning of the contact.

3. The method of improving the efliciency of evaporative cool-ing that comprises passing the fluid to have heat extracted therefrom and the cooling liquid in countercurrent flow, indirect heat exchange relationship and then without introducing additional heat to said liquid passing said fluid and all of said liquid in concurrent flow, indirect heat exchange relationship while evaporating a portion of the cooling liquid.

4. Apparatus for cooling fluids under conditions of high thermal efliciency that comprises a coil, means to pass the fluid to be cooled into the top of said coil and to withdraw it from the bottom of said coil, means for spraying cooling water downwardly over said coil, means below said coil to collect water, means to cause a flow of air upwardly through said coil and counter to said spray and means defining a flow path from said collecting means to said spray means and means in said flow path for passing said water in heat exchange relation to said fluid to be cooled before said liquid enters the top of said coil.

5. Apparatus for cooling fluids under conditions of high thermal efliciency that comprises a coil, means to pass the fluid to be cooled into the top of said coil and to withdraw it from the bottom of said coil, means for spraying cooling water downwardly over said coil, means below said coil to collect water, means to cause a flow of air upwardly through said coil and counter to said spray and means defining a flow path from said water-collecting means to said spraying means,- said flow path including a passageway through said coil to provide for countercurrent flow, indirect heat exchange between the fluid to be cooled and the water flowing from the water collecting means to the spraying means.

6. Apparatus as claimed in claim 4 further comprising a wet deck section in the region of counterflow of air and spray.

7. Apparatus as claimed in claim 5 further comprising'a wet deck section in the region of counterflow of air and spray.

References Cited by the Examiner UNITED STATES PATENTS 1,732,963 10/29 Burhorn 623 10 2,1 66,158 7/39 Kalischer 625 13 2,257,983 10/41 Shipman 623 05 2,787,134 4/57 Boling 62305 CHARLES SUKALO, Primary Examiner. HERBERT L. MARTIN, FREDERICK L. MATTESON,

JR., PERCY L. PATRICK, Examiners.

Claims

1. THE METHOD OF IMPROVING THE EFFICIENCY OF EVAPORATIVE HEAT EXTRACTION THAT COMPRISES AS THE FIRST STEP IN EXTRACTING HEAT FROM A FLUID THAT HAS ABSORBED HEAT, PASSING SAID FLUID TO HAVE HEAT EXTRACTED THEREFROM AND A COOLING LIQUID IN MUTUAL HEAT EXCHANGE RELATION WITHOUT EVAPORATION OF SAID COOLING LIQUID AND THEN PASSING THE SAME FLUID AND OF ALL SAID LIQUID IN MUTUAL HEAT EXCHANGE RELATION WHILE EVAPORATING AT LEAST A PORTION OF SAID COOLING LIQUID.