Superdensity assembly system for heat exchangers

Page 1 — bibliographic record

Page 2

Drawing sheet — no readable text.

Page 3

Drawing sheet — no readable text.

Page 4

Drawing sheet — no readable text.

Page 5

combined cooling effects. However, such attempted use

SUPERDENSITY ASSEMBLY SYSTEM FOR HEAT of numerous tanks involves an expensive, large scale EXCHANGERS installation.

If an attempt is made to crowd more heat exchange

This is a division of application Ser. No. 06/662,387, tubing into a tank for increasing the cooling effect, an filed Oct. 18, 1984, and now U.S. Pat. No. 4,616,390, unexpected problem is encountered. Assuming that the Oct. 14, 1986. PCM being used is water, the water surrounding the FIELD OF THE INVENTION tubes becomes frozen completely solid when the tank is fully charged with cooling, thus, it will lose its buoy

The present invention is in the field of phase change O ancy when all the liquid has become frozen. However, thermal storage. More particularly this invention relates when the ice is nearly all frozen, say 90% or so, a maxi to a superdensity assembly method and system for plas mum buoyancy force is equal to the weight of the dis tic heat exchangers of the coiled tubing bundle type placed liquid less the weight of the displacing object, positioned in cylindrical tanks having vertical axes for the buoyancy force at 90% frozen in water/ice is equal resisting the large buoyancy forces which are generated 15 to 8.33 lbs/gallon times the approximately 9% expan by ice build-up on the multiple tubes and enabling sion when ice is frozen. The heat exchanger tubes them changes in predetermined tubing densities throughout selves, being made of a plastic slightly lighter than various tanks to be accomplished easily and reliably for water and filled with an anti-freeze liquid solution meeting the needs of various applications. slightly heavier than water, can be neglected. Thus, a 20 tank holding 2,000 gallons of water will have a buoy

BACKGROUND OF THE INVENTION

The present invention is an improvement over the tubes having a built-up ice coating.

invention in U.S. Pat. Nos. 4,294,078 and 4,403,645 of In a phase change liquid salt solution having a density the present inventor. as high as 1.8 times the density of water, the buoyancy There are a variety of applications which require the 25 of the heat exchanger volume itself would also have to fast meltdown of phase change material (PCM) from its be taken into account, and thus the buoyancy forces can solid, e.g. frozen or ice state, into its liquid, e.g. melted be much higher. If the heat exchanger, weighing the or water state, in order to provide an intense surge of same as water, occupied 25% of the volume of the tank cooling over a relatively brief time span. Examples of and the heavy phase change material did not change such applications include a short church service, brief 30 volume as it froze, the buoyancy force on the heat ex use of an auditorium or theater, providing cool air to an changer would be airplane while it's unloading and loading passengers, 0.25X2,000x (1.8-1.0)x 8.33=3,330 lbs. levelling short term combinations of loads, and cooling When water freezes to solid ice or another phase computers or spaces during a brief power outage where change material freezes solid, crystals are formed which the stand-by generator only needs to run a pump and 35 create strong local forces. Thus, I have found that a blower but not the refrigeration equipment. An example heat exchanger imbedded in such a crystallized mass of such a fast melt down application would be a large must be somewhat flexible and resiliently deformable in airport in which the central air conditioning system its structure and, in its components to prevent breakage electrical load on certain summer nights coincides with but also must have the inherent strength to resist the and thus adds to the airport illumination electrical load 40 buoyance forces. Also, the components must be non for two hours before the air conditioning is shut off, corrodible and inexpensive, since the heat exchanger thereby causing an expensive 2000 KW peak electrical would include many more components than in the demand, which would cost more than $50,000 per above patents. Also, the component tubes and their month in demand charges, that could be avoided by the support members are less likely to be deformed if the ice use of fast melting stored ice. 45 does not stick to their surfaces too strongly, as is noticed Another example of such a fast melt down applica in an ice cube tray of a freezer where ice cubes can be tion would be an airlines terminal at a hub airport for dislodged by bending the tray. The material of which many outlying cities, where more than a dozen passen the tubes and support members are made must also not ger airplanes must simultaneously be provided with become brittle at low temperatures.

cool air for one hour while passengers are shifting to 50 SUMMARY other flights to their respective outlying destinations.

Then the gates will be empty for some time until an This invention enables the crowding or superdensity other group of planes arrive together at the hub airport. packing of far more heat exchange area per unit volume As a further example of an application calling for an within a tank containing PCM without undue cost, intense burst of cooling for a brief period, it is noted that 55 weight, pressure drop, manufacturing or handling oper a computer installation requires the back-up of uninter ations, or structural weakening and while being capable ruptible power systems (UPS) during a power failure so of resisting the large buoyancy forces involved. The that their valuable memories will not be lost. To size novel assembly method and system allow for any de UPS to provide cooling is very expensive. Computers gree of heat exchange density or surface area per unit heat up and become damaged very quickly if run with volume in the coiled plastic tubing heat exchanger that out cooling, if even only for the time to store away is desirable for a given cooling application. memory content into magnetic discs. I have found the reliable, practicable answers to all of In order to meet the requirements of these brief but the problems and qualities discussed above in the assem intense cooling situations it would be possible to employ bly method and system of this invention. The support a relatively large number of the thermal storage tanks 65 members for the numerous slippery plastic tubes are disclosed in U.S. Pat. Nos. 4,294,078 and 4,403,645 and relatively rigid slippery plastic strips made, for example, then to operate all of their heat exchangers simulta of high density polyethyelene (H.D.P.E.) or polypro neously in parallel with each other for obtaining their pylene and having a thickness in the range from th to

Page 6

th of an inch thick, with an intermediate thickness of In accordance with the present invention in one as 3/16ths of an inch being the preferred thickness for pect there is provided a method for making a coiled reasons discussed below. These strips are to be suffi tubing bundle heat exchanger in a tank for containing ciently thick to provide enough stiffness to avoid undue 5 phase change material (PCM) which becomes frozen deflection under stress of large longitudinal compres (solid) during extraction of heat and which becomes sional loadings developed due to buoyance effects as melted (liquid) during addition of heat comprising the discussed above. On the other hand, these strips are not steps of providing a multiplicity of relatively rigid, thick to be unduly thick such as to interfere with formation of slippery plastic strips having an overall length L equal keyhole slots in them as shown. to the internal height of the tank in which the coiled In order to capture and hold the multiple tubes, key O tubing bundle is intended to be placed and having front hole slots are formed in each strip extending into the and rear edges; providing a multiplicity of individual body of the strip from its "front edge. Each keyhole plastic tubes of slippery plastic having an outside diame slot terminates in a rounded seat having a diameter in.) ter (O.D.) in the range from 9/32th of an inch (0.28125 slightly smaller than the O.D. of the tubes which are shaped to one inch; forming uniformly spaced, keyhole forced into these slots for becoming firmly seated in and each strip slots extending inwardly from the front edge of captured by these seats. These seats are each positioned having a diameter each terminating in a rounded seat opening a predetermined distance from the "rear" edge of the tubes, with said slots slightly smaller than the O.D. of the strip for establishing the horizontal center-to-center predetermined distance in each strip being spaced apart a spacing "X" of the tubes in the coiled heat exchanger predetermined vertical along the strip for establishing and are spaced a predetermined center-to-center dis with said rounded seats located"Y" spacing of the tubes and a predetermined dis tance "Y" along the length of the strip for setting the tance from the rear edge for establishing predetermined vertical center-to-center spacing of the neighboring horizontal spacing "X" of the tubes in the coiled heat coiled tubes. exchanger; spacing the strips approximately uniformly The keyhole-slotted support spacer strips get a good 25 parallel to each other extending transversely of the firm hold on each and every tube throughout the tank. tubes; pushing the tubes into the respective keyhole So, when ice builds up on the tubes, the spacer Strips keep the tube bundle, or heat exchanger, from rising slots in the strips for capturing the tubes in the respec because the strips press in large numbers against the coil havingcoiling tive seats; the captured tubes into a tight spiral an axis parallel with the lengths L of the rigid top or inner cover of the tank. 30 strips for forming a coiled tubing bundle in which the The density of the coiled plastic tubes within the successive convolutions of the coiled tubes are prede PCM in the tank is determined by the following for termindely spaced "X" from the neighboring prior con mula, where "d' is the O.D. of the tubes: volutions by resting against the rear edges of the strips (1) Density = ird2/4xy=0.786d2/xy. In most installa in which the portions of the tubes forming the prior tions the predetermined X and y spacings are made 35 convolutions are captured; and placing the coiled tub equal, and thus, the density formula can be simplified to: ing bundle in a tank for containing PCM, with the oppo (2) Density = T/4a2=0.786/a2, where "a" is the ratio site ends of the strips abutting the bottom and cover of of center-to-center tube spacing to the O.D. of the the tank for supporting the tubes and for resisting the tubes. large buoyance forces developed by the heat exchanger The assembly method and system of this invention 40 in the liquid PCM and/or during build-up of frozen advantageously enable the density of tubing in each PCM on the multiple coiled tubes.

tank to be tailored to the particular requirements of In accordance with this invention in another of its each installation for achieving the optimum over-all aspects a multiple plastic tube, coiled tubing bundle heat economic return in a compact installation having dura exchanger is provided in a tank containing PCM which ble, long life and reliable, predictable, excellent perfor 45 becomes frozen (solid) during extraction of heat and mance. For example, tubing densities in the range from which becomes melted (liquid) during addition of heat 5% up to 32% or more are now made feasible. comprising a multiplicity of individual horizontally The maximum tubing densities contemplated in my extending plastic tubes of slippery plastic all having the prior two patents referred to above is around 10%. This same outside diameter (O.D.) in the range from 9/32ths keyhole slot assembly method and system enables con 50 of an inch (0.28125 in.) to one inch, a multiplicity of venient and reliable superdensity coiled plastic tubing relatively rigid, thick, vertical slippery plastic strips heat exchangers to be constructed durably resisting the having an overall length L equal to the internal height strong forces and stresses to which their components of the tank in which the coiled tubing bundle is placed are subjected during freeze-up. Densities above 20% and having front and rear edges and with the upper and are considered to be in the "superdensity" range. 55 lower ends of each strip abutting the cover and bottom It is among the objects of the present invention to of the tank. Each of the strips has uniformly spaced, provide dramatically improved coiled plastic tubing keyhole shaped slots extending inwardly from its front heat exchangers in tanks for containing PCM by an edge, each keyhole slot terminating in a rounded seat assembly method and system which maintains excellent having a diameter slightly smaller than the O.D. of the overall quality and performance of the resulting heat 60 tubes. These rounded seats are spaced vertically in each exchangers while accomplishing the objectives inexpen strip by a predetermined spacing "Y" for holding the sively, easily and conveniently. tubes horizontally and spaced vertically center-to-cen Further objects of the invention are to provide super ter by said predetermined distance "Y" and with the density coiled tubing heat exchangers in tanks contain rounded seats located a predetermined distance from ing PCM capable of resisting the strong buoyancy 65 the rear edge of the strip for holding the horizontal forces and stresses occasioned by closely packed plastic tubes spaced horizontally center-to-center by a prede tubes imbedded in a mass of liquid as the solid ice and termined distance "X" for establishing the desired tub crystals build-up around the numerous tubes. ing density throughout the PCM in the tank. The tubes

Page 7

are captured and firmly held in the respective seats of between the tubes. In other words, in order to provide the keyhole slots in said strips for supporting and hold 24% density of inch O.D. tubes uniformly throughout ing said tubes in spaced parallel relationship uniformly the PCM in a tank in a square pattern requires that the spaced apart "Y" vertically with said strips being spacing between tubes be only 0.4 of an inch, which is spaced apart approximately uniformly along the length only 80% of the diameter of the very tubes themselves. of the parallel tubes. In the spirally coiled heat ex Such a superdensity packing is conveniently changer the successive convolutions of the coiled tubes achieved, as shown in FIGS. 1 and 2, int he coiled are advantageously separated by a predetermined spac plastic tubing heat exchanger 10 by employing numer ing "X" from the neighboring prior convolutions by ous relatively rigid flat strips 12 of slippery plastic resting against the rear edges of the strips in which the O made, for example, of H.D.P.E. or polypropylene and neighboring prior convolutions of the tubes are cap having a thickness in the range from th to th of an tured. A very convenient, effective, efficient, economi inch thick, with an intermediate thickness of 3/16ths of cal and durable heat exchanger is obtained for use in an inch being shown in FIG. 2 as the optimum thick tanks containing PCM. ness. Keyhole-shaped slots 14 (FIG. 3) are formed in 15 each of these strips, for example, by punching. These

BRIEF DESCRIPTION OF THE DRAWINGS slippery plastic strips 12 are sufficiently thick to provide The various features, objects, aspects and advantages enough stiffness to avoid undue deflection under stress of the present invention will become more fully under of large longitudinal compressional loadings developed stood and appreciated from a consideration of the fol due to large buoyancy effects. On the other hand, these lowing detailed description in conjunction with the 20 strips are not unduly thick such as to interfere with accompanying drawings describing and illustrating the formation of the keyhole slots 14. Thickness of 3/16ths best mode I contemplate for practicing this invention. of an inch is the optimum compromise I have found for FIG. 1 is an elevational sectional view of a portion of the slippery plastic materials as described. a superdensity coiled plastic tubing heat exchanger in a These keyhole slots 14 are formed in each strip 12 tank for containing PCM and being shown full scale 25 extending into the body of the strip from its "front" with portions broken away; edge 16. Each keyhole slot terminates in a rounded seat FIG. 2 is an elevational view as seen looking in the 18 having a diameter "S" (see also FIG. 1) slightly direction toward the right 2-2 in FIG. 1; smaller than the O.D. of the tubes 20 which are forced FIG. 3 shows the configuration of a keyhole slot into these slots for becoming firmly seated in and cap twice full size; and 30 tured by the respective seats 18. For example, in order FIG. 4 is a somewhat schematic plan view of the to firmly grasp and hold tubes having an O.D. of 0.50 of coiled tubing. an inch, the optimum value for S is 31/64th of an inch, DESCRIPTION namely, 1/64th of an inch less than the O.D., being about 1.6% less.

As explained above in the introduction, there are 35 The rounded seats 18 are centered a predetermined various severe commercial applications calling for sud distance "G" from the "rear' edge 22 of each strip such densurges of cooling over relatively brief spans of time. that G plus one-half of the tube O.D. will be equal to the Such brief time periods are often approximately 1.5 to 2 desired horizontal center-to-center spacing "X" of the hours in duration. neighboring convolutions of the tubes in the heat ex I have found by experiment that to melt solid ice in changer 10. The seats 18 are spaced a predetermined about two hours by means of polyethylene plastic tubes center-to-center distance "Y" along the length of the embedded in the ice carrying a heat transfer liquid en strip for setting the vertical center-to-center spacing of tering the tubes at a temperature of about 20 F. above the neighboring coiled tubes.

the ice temperature requires about 4 square feet of tube In order to facilitate entry of the inserted tube, each surface per gallon of ice (or water) arranged as homoge 45 keyhole slot 14 has a funnel entrance 24 converging neously (uniformly) as possible throughout the mass of inwardly from the front edge 16. For example, this ice. The size of the plastic tubes is desired to be rela funnel entrance, as shown, has an entry mouth with a tively small (under one inch O.D.), so that they can be span "M" of 9/16ths of an inch, namely, about 6% to coiled without employing heroic measures. On the 7% larger than the tube O.D. for ease of entry when the other hand, the tubes cannot be too small, because then 50 tubes are being inserted perpendicular to their own too many of them will be required to handle the neces length through the keyhole slots into their seats 18. The sary flow, and hence their assembly becomes uneco funnel entrance 24 converges inwardly at an acute angle nomical. The preferred range of tubing O.D. is 9/32nds "F", for example, in the range from 30 to 75". I have to ths of an inch, with the optimum O.D. size being found that a funnel angle F of about 60' works to advan inch, but it is feasible to go down to th of an inch 55 tage.

tubing O.D. or up to one inch tubing O.D. For obtaining a good firm grip on the fully inserted One-half inch O.D. tubes have 0.131 square feet of tubes, each of the keyhole slots 14 has a narrow throat surface area for every foot of length. Therefore, about 26 (FIG. 3) which communicates directly into the 30 such tubes, one foot long, would be required in one rounded seat opening 18, thereby creating shoulders 27 gallon of water to provide 3.93 (about 4) sq. ft. of tube for retaining the inserted tubes in their seats 18. For surface. Since a gallon occupies 231 cubic inches and example, as shown, each throat 26 has a width Tofiths the 30 tubes occupy 71 cubic inches, the tubing occupies of an inch, i.e. this throat has a width of only 75% of the 71/(231-71), or about 24% of the total volume in O.D. of the tube to be inserted through it. Conse volved. In a square pattern, and referring to the density quently, during the insertion thrust, the H.D.P.E. tube formula (2) above, when x and y are made equal 65 20 momentarily resiliently flattens sufficiently on each (namely, a square pattern), this 24% density value side to pass through the narrow throat 26 and then means that the "O.D. tubes must be spaced from each immediately resiliently springs back to a circular con other center-to-center 0.90 of an inch, or 0.4 of an inch figuration in the tightly embracing seat 18.

Page 8

In order to aid in producing a momentary resilient It will now be understood that any desired predeter flattening of the inserted tube, both edges of the funnel mined horizontal and vertical spacings X and Y within entrance 24 are rounded at 28 forming curved transi reasonable limits can be achieved by selecting the strip tions which are tangent to the edges of the funnel en width B including the desired distance G from the rear trance 24 and also tangent to the edges of the throat 26. 5 edge 22 to the seat center and by selecting the slot spac For example, as shown, this rounding at 28 has a radius ing Y. If the ice or other PCM 36 must be melted more of 3/16ths of an inch, namely, a radius of curvature quickly, then the strips 12 are narrower, and the key equal to about 75% of the radius of the O.D. of the tube hole slots 14 are closer together. If a slower melting itself. period, such as cooling a building over 10 occupied The strips 12 are spaced approximately uniformly O hours, were desired, the strips would be wider and the along the length of the tubes 20, for example, by a spac keyhole slots farther apart. If the anti-freeze heat trans ing in the range from 1 foot to 3 feet. The more densely fer liquid leaving the tubes 20 of the tank/heat ex that the tubes 20 are to be packed in the coiled heat changer 10 were required to be closer to the freezing exchanger 10, the more of the strips 12 which will be 5 point of water, such as for a low temperature air condi included for maintaining the accuracy of the spacing tioning duct system, then the strips would be narrower with neighboring convolutions of the coiled heat ex and the keyhole slots closer together. Conversely, if a changer, and so the closer these strips are positioned standard temperature duct system were used, wider along the length of the tubes within this 1 to 3 foot strips and wider keyhole slot spacings could be used and thus save cost.

range, and vice versa.

After all of the tubes 20 have been inserted and are 20 As the strip width B and the rear edge to seat center captured in their respective seats 18, these captured distance G is reduced, the spiral convolutions of the tubes are firmly held uniformly spaced extending paral tubes 30 become closer together, or, in other words, the lel to each other. Suitable conduit connections 38 and 39 spiral becomes more tightly wound. As the spiral be comes more tightly wound, the tubes become longer to (see FIG. 4) are made to the ends of the tubes, as will be 25 fill understood from the above referenced patents. Then, mean out a given diameter tank 30. Longer tube lengths these captured parallel tubes are rolled up into a spiral higher pressure drops for the ethylene glycol and roll 10 whose axis is parallel with the length "L" of the water anti-freeze solution being circulated through the strips 12. As shown in FIG. 1. the rear edges 22 of the tubes,needed and thus higher circulating pump power is to produce a given flow rate when faced with a strips are in contact with the neighboring convolutions 30 higher pressure drop. The increased pressure drop in of the tubes 20, and thus the distance G establishes the predetermined horizontal center-to-center spacing "X". there are now moreis tubes each longer tube somewhat offset by the fact that

The rear edges 22 preferably all face inwardly toward tue of having more spiralsconnected of tubes, in parallel by vir because of their the axis of the heat exchanger 10.

The center of each seat 18 is spaced inwardly a dis 35 closer vertical spacing and less total ice to be frozen. However, the over-riding faster melt down requirement tance "A" from the front edge 16 of the strip. The over means that greater total flow is called for, and so the all width "B" of each strip is the sum of "A" plus "G". overall net effect is higher pressure drop. These support strips 12 have a length L equal to the The easiest way to counteract this increased pressure internal height of the tank 30 between the bottom wall drop 32 and the rigid top or inner cover 34 of the tank. Thus, 40 tanks. isI have to reduce the tank diameter and to use more found that reducing the ice volume about these strips 12 are adapted normally to rest on the bot in half or, in other words, reducing the diameter of the tom wall 32 for supporting the weight of the heat ex changer 10. The keyhole-slotted support spacer strips tank 30 by the square root of one-half gives about equiv 12 provide a firm gripping hold on each and every tube alent pressure drop between a low density and a high 20 throughout the tank 30. Thus, when ice builds up on 45 density heat exchanger.

the tubes, the spacer strips 12 keep the tube bundle heat EXAMPLES exchanger 10 from rising, because the strips press in large numbers against the rigid cover 34 which is areExamples of various coiled tubing heat exchangers 10 given in the following table, which also sets forth strongly and securely fastened to the side wall (not shown) of the tank 30. 50 the resultant tubing density in the PCM 36 in the tank 30. The tubing O.D. is one-half of an inch for each

In FIG. 1, the dimension "E" is the spacing between example:

the center of the lowermost seat 18 and the lower end of the strip 12. This dimension E is preferably slightly less than Y or may be equal to but not more than Y for Tubing Density achieving an effectively uniform tubing distribution 55 A (in.) G (in.) X (in.) Y (in.) in the PCM within the PCM throughout the tank. The dimension 0.5 0.55 0.8 0.8 31% 'C' is the distance from the center of the uppermost 0.5

seat 18 to the upper end of the strip 12. C is usually in 0.65 0.75 1.0 1.0 20% the range between 3.5 and 7.75 inches depending upon 0.65 0.85 1.1 1. 6% the internal tank height and the relative expansion of 60 0.65 0.95 1.2 1.2 14% some PCM's during freezing. As indicated by the 0.65 1.15 1.4 1.4 10% dashed line 36, the melted (liquid) PCM fully covers the 0.65 1.35 .6 1.6 8%

uppermost tube 20 in the exchange 10. The taller the tank and the greater the expansion of the PCM 36 dur ing freezing, the greater "C" will be in order to provide 65 It will be understood that the dimension G in large sufficient headroom below the cover 34 for accommo measure determines the strength of the strips 12. There dating the expected overall expansion of some PCM's fore, as B is increased, G is increased more than A. For during freeze up, without its contacting the cover 34. wider strips, A may be kept constant at a reasonable

Page 9

value, for example, 0.65 inches, as shown, or 0.75 each of said strips having generally uniformly spaced inches. There are sufficient strips 12 to resist the total tube-capturing slots extending inwardly from its buoyancy. It will be understood that the density of the front edge, circulating anti-freeze heat transfer liquid relative to the each tube capturing slot terminating in a seat opening density of the PCM will affect the total buoyancy. In 5 having an effective size for firmly gripping the addition to the ethylene glycol solution discussed O.D. of the tubes, above, other suitable anti-freeze liquids which are some said seats being spaced vertically in each strip by a times used are a methanol solution or a solution of cal predetermined spacing "Y" for holding the tubes cium chloride in water, but ethylene glycol solution is horizontally and spaced vertically center-to-center usually preferred. by said predetermined distance "Y" and with the As used herein, the terms "frozen' and 'melted' are 10 seats located a predetermined distance from the intended to include crystallized and decrystallized rear edge of the strip for holding the horizontal states, respectively. In some cases additives are included tubes spaced horizontally center-to-center by a in the PCM to form a gel-like structure to contain the predetermined distance "X" for establishing the melted PCM distributed in multitudes of tiny pores 15 desired tubing density throughout the PCM in the throughout the gel-like structure. tank,

In the heat exchanger coil 10, the rear edges 22 of all said tubes being captured in the respective seats of the strips preferably all face in the same direction. These slots in said strips for supporting and holding said rear edges 22 may all face inwardly toward the axis of tubes at substantially equal intervals throughout the coil 10 or they may all face outwardly toward the their lengths in spaced parallel relationship uni perimeter of the coil 10, i.e. toward the side wall of the 20 formly spaced apart "Y" vertically with said strips tank 30. being spaced apart approximately uniformly along What is claimed is: the length of the parallel tubes, 1. A coil tube bundle for a heat exchanger which said parallel tubes being coiled into a spiral coil as comprises seen in plan view having an axis parallel with the (a) a multiplicity of substantially rigid strips each 25 length L of the strips forming a coiled tubing bun formed with equally spaced slots inwardly along a dle in which the strips are parallel with their seats front edge thereof and with each slot defining a aligned in spiral rows and facing the same direction seat opening through a narrower funnel throat to relative to a center axis of the spiral rows and suc the front edge of the strip, cessive convolutions of the coiled tubes are prede (b) the strips being parallel to one another with their 30 terminedly spaced "X" from the neighboring con respective slots aligned in spiral rows and facing in volutions by resting against the rear edges of the the same direction relative to a central axis of said strips in which the neighboring convolutions of the spiral rows, and tubes are seated.

(c) flexible tubes of resilient circular cross section 6. A coiled tubing heat exchanger as claimed in claim spirally disposed across the strips with each tube 5, in which tightly embraced within the seats of a row of slots 35 said tube-capturing slots include a funnel entrance to form a coiled interconnected grid of rigid strips converging inwardly from the front edge of the and flexible tubes with convolutions of each tube strip, and contacting and being spaced apart by rear edges of each funnel entrance has an entry mouth width "M" the strips opposite the front edges and with the wider than the O.D. of the tubes. tubes supported at substantially equal intervals 40 7. A coiled tubing heat exchanger as claimed in claim throughout their lengths. 5, in which 2. A tube bundle, according to claim 1 wherein the said tube-capturing slots have a keyhole shape and tube bundle is contained between a cover and a bottom each includes a narrow throat region iocated be of a tank with opposite ends of the strips aligned and tween the front edge of the strip and the seat, abutting the cover and bottom, the bundle being 45 the narrow throat communicates directly with the emersed in a liquid phase-change material which is seat forming a pair of shoulders at the juncture of expandable upwardly toward the cover upon freezing. the throat region and the seat, and 3. A tube bundle according to claim 1 wherein the the spacing "T" between said shoulders is sufficiently rear edges of the strips in the bundle face inwardly less than the tubing O.D. for firmly retaining said toward the central axis. 50 tube, wherein said tube is a stiffly flexible, resil 4. A tube bundle according to claim 1 wherein the iently deformable plastic tube inserted into the seat front edges of the strips in the bundles are spaced from by an insertion thrust exerted perpendicular to the the tubes. tube axis.

5. A multiple plastic tube, coiled tubing bundle heat 8. A coiled tubing heat exchanger claimed in claim 7, exchanger for use in a tank for containing phase change 55 in which said spacing "T" between the shoulders is at material (PCM) which becomes frozen during extrac least 10% less than the O.D. of the tube.

tion of heat and which becomes melted during addition 9. A coiled tubing heat exchanger as claimed in claim of heat comprising: 7, in which the stiffly flexible, resiliently deformable a multiplicity of individual horizontally extending tubes are formed of polyethylene and have a tubing wall plastic tubes all having an outside diameter (O.D.) 60 thickness of about 1/16th of an inch.

in the range from 9/32ths of an inch (0.28125 in.) to 10. A coiled tubing heat exchanger as claimed in one inch, claim 9, in which the stiffly flexible, resiliently deform a multiplicity of relatively rigid, thick, vertical plastic able tubes are formed of polyethylene and have a tubing strips having an overall length L comparable with wall thickness of about 1/16th of an inch.

the internal height of the tank in which the coiled 11. A coiled tubing heat exchanger as claimed in tubing bundle is to be placed and having front and 65 claim 5, in which the coiled heat exchanger is self-sup rear edges and with the upper and lower ends of porting when free-standing before being installed in the each strip for positioning near the cover and bot tank.

tom of the tank, ck xk 2k sk