US3782132A

US3782132A - Heat-exchange system

Info

Publication number: US3782132A
Application number: US00260389A
Authority: US
Inventors: H Lohoff
Original assignee: CTC GmbH
Current assignee: CTC GmbH
Priority date: 1971-06-08
Filing date: 1972-06-07
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01
Also published as: DE2128331A1; ZA723116B

Abstract

A conduit has an inlet portion, an outlet portion, and a main body portion which is to be embedded in a structural element and which is composed of at least two parallel sections having identical internal cross-sectional areas and being in heatexchanging contact with one another over their entire length. One of these sections is adapted to receive fresh incoming heat exchange fluid from the inlet portion and the other section is adapted to receive spent heat-exchange fluid from the first section and to conduct it to the outlet portion. A pump is provided for circulating heat-exchange fluid through the conduit and one or more identical or different heat-exchanges are interposed for adjusting the temperature of the heat-exchange fluid.

Description

United States Patent [1 1 Lohoff HEAT-EXCHANGE SYSTEM [75] Inventor: Hermann Lohoff, Bochum,

Germany [73] Assignee: CTC GmbH, Hamburg, Germany [22] Filed: June 7, 1972 [21] App]. No.: 260,389

[30] Foreign Application Priority Data June 8, 1971 Germany P 21 28 331.8

[52] US. Cl 62/260, 62/333, 162/515, 165/45, 165/46, 165/49, 165/49, 165/168, 165/171 [51] Int. Cl. F25d 23/12 [58] Field of Search 62/260, 333; 165/45, 165/46, 49, 168, 171

[56] References Cited UNITED STATES PATENTS 520.930 6/1894 Levey et al... 165/171 2,513,373 7/1950 Sporn 62/260 2,780,415 2/1957 Gay 62/260 2,784,945 3/1957 Fodor 165/45 2,996,896 8/1961 Johnson.... 62/235 3,012,596 12/1961 Skolout 62/235 [111 3,782,132 [4 1 Jan.l1,1974

Primary Examiner--William J. Wye Att0rney-Michael S. Striker 5 7 ABSTRACT A conduit has an inlet portion, an outlet portion, and a main body portion which is to be embedded in a structural element and which is composed of at least two parallel sections having identical internal crosssectional areas and being in heat-exchanging contact with one another over their entire length. One of these sections is adapted to receive fresh incoming heat exchange fluid from the inlet portion and the other section is adapted to receive spent heat-exchange fluid from the first section and to conduct it to the outlet portion. A pump is provided for circulating heatexchange fluid through the conduit and one or more identical or different heat-exchanges are interposed for adjusting the temperature of the heat-exchange fluid.

15 Claims, 3 Drawing Figures PATENTEDJAH 1 1974 3782.132 snmaufz 1 HEAT-EXCHANGE SYSTEM BACKGROUND OF THE INVENTION The present invention relates generally to heatexchange systems and more particularly to heat exchange systems which are especially suited for use in structural elements.

In many instances it is necessary to heat or cool enclosed spaces in structures by influencing the temperature of a structural component of such a structure. For instance, it is already known to embed in a panel which is installed on or as the floor of a room, a conduit through which hot or warm water is circulated. This water then yields up heat to the panel material in which the conduit is embedded, heating the panel material and thus the room in which a surface of the panel is exposed.

The prior art has not previously proposed an arrangement of this type in which the temperature at the exposed surface of the panel (which latter could of course also be provided on or in a wall,or on or in a ceiling), can be varied both uniformly and relatively rapidly. Consequently, the constructions of this type which are known from the prior art require relatively substantial amounts of expended energy for their operation, and do not provide the degree of comfort in a room with which they are associated, which is desirable.

SUMMARY OF THE INVENTION It is, accordingly, a general object of the present invention to overcome these disadvantages of the prior art.

More particularly, it is an object of the present invention to provide an improved heat-exchange system which overcomes such disadvantages.

Still more particularly, it is an object of the invention to provide such an improved heat-exchange system which utilizes one or more conduits that can be embedded in part in a structural element and will, when the heat-exchange system is operated, provide for a uniform temperature over the entire exposed surface of the structural element.

In pursuance of these objects and of others which will become apparent hereafter, one feature of the invention resides in a heat-exchange system which, briefly stated, comprises a combination of conduit means including an inlet portion, an outlet portion and a main body portion, intermediate the inlet and outlet portions. The main body portion is adapted for embedding in a structural element and includes at least two parallel sections of at least substantially identical crosssectional area and which are in heat-exchanging contact with one another, over at least substantially their entire length. One of these conduit sections is adapted to receive incoming fresh heat-exchange fluid from the inlet portion and the other conduit section is adapted to receive spent heat-exchange fluid from the first section and to conduit it to the outlet section. Circulating means is provided for circulating heatexchange fluid through the conduit means and heatexchange means is provided for adjusting the temperature of the heat-exchange fluid circulated by the circulating means to the desired level.

Due to the fact that according to the invention the aforementioned conduit sections extend in parallel, have substantially identical cross-sectional areas and are in heat-exchanging contact with one another over at least substantially their entire length, the temperature given a structural element in which they are embedded, and in particular at the exposed surface of such a structural element, is highly uniform everywhere. Because of this, the comfort of persons in a room in which such a structural element is used for heating or cooling purposes is substantially improved, and, a concomitant not to be overlooked, the energy required to be expended in order to obtain the desired temperature level can be reduced over what is known from the prior art.

If the heat-exchange system of the present invention is to be utilized for cooling the structural element in which its conduit sections are embedded, then cooling fluid must of course be passed through the conduit means. In such a case it is, however, essential to assure that the surface temperature of the structural element being cooled will, depending upon the ambient conditions in the air of the room in which it is used, not fall below that temperature at which the water vapor contained in the ambient air will begin to condense at the exposed surface.

The concept of embedding conduits for instance in a floor of a structure, and circulating cooling water through them is not in itself novel. It is for instance known to circulate town water or well water through such conduits, water which in temperate zones usually has a temperature of substantially 8 14 C. If the water temperature is for instance 14 C. and the resulting surface temperature of the floor is 17 C, the dew point temperature (the temperature at which water vapor in the air of a room whose floor is being cooled thusly, will condense) is not met on many days throughout the year. In other words, the surface temperature of the floor will be cooler than the dew point temperature and as a result condensation will take place. To prevent this it is necessary in such case to shut off the system and do without cooling entirely, or to either heat the incoming town or well water or mix it with warm water in order to raise its temperature and thereby the surface temperature of the floor. Evidently, the former possibility is uncomfortable and the latter possibility is expensive.

A further disadvantage of this prior art approach to cooling is the fact that the floor can be cooled only highly unevenly, that is there will be local areas where the floor is cooler than at other areas. Aside from the undesirable influence on the comfort of users of the room, this further causes the development of stress cracks in the floor.

The present invention, however, eliminates all these problems because due to the fact that the conduit sections which respectively carry the incoming fresh heatexchange fluid and the outgoing spent heat-exchange fluid, extend in parallelism and are in contact over all or substantially their entire length, with the heatexchange fluid flowing in opposite directions in the respective conduit sections, a uniform heating or cooling of the structural element in which the conduit sections are embedded is assured. Furthermore it has been found that when the heat-exchange system according to the present invention it utilized for cooling purposes, the incoming cooling fluid (usually water) can have a temperature which is actually below the previous critical temperature (at which the structural element was cooled to the point where condensation would take place at its exposed surface) without causing condensation. Evidently, this increases the effectiveness of the system.

It is advantageous to provide a heat exchange unit, which according to one concept of the invention may be in form of a conduit coil which is embedded in the soil, and connected with the inlet portion of the conduit means so that the cooling fluid will pass through this conduit coil. The latter should advantageously be of synthetic plastic material to avoid rusting.

The heat-exchange unit can, however, also be in form ofa cooling coil which is interposed in the inlet portion of the conduit means, although this second possibility, contrary to the first-mentioned one which requires no additional operating expenses, does require additional expenses for its operation. On the other hand, the second possibility has been found to be highly advantageous where high cooling capacity is required, especially in view of the fact that at an ambient air temperature of 32 C. and a relative humidity of 40 percent such cooling tower can still produce a cooling water temperature of 21 C.

However, the heat exchange unit can also be in form of a heat pump, or more particularly the evaporator of the heat pump whose condenser is constructed as a conduit coil which may be embedded in the soil and which also advantageously is of synthetic plastic material. With such a construction it is possible to select heating or cooling at the choice of a user, simply by switching the heat pump from cooling operation to heating operation. Such an arrangement is particularly advantageous because of the low energy requirement and expenses which are merely needed for operating the compressor, whereas the cooling or heating energy is taken directly from the soil.

A heat pump is so well known in its construction and its operation, that a detailed discussion is not thought to be necessary herein. However, if additional information is required, reference may be had to Heating and Ventilating Engineering Databook", Clifford Strock, published by The Industrial Press, N. Y. 1938, Section I0.

I have found it to be particularly advantageous if the inner diameter of the flow passages in the conduit means is at most 25 mm., and if, should the main body portion have more than one conduit sections for fresh heat-exchange fluid and more than one conduit section for spent heat-exchange fluid, the distance between adjacent conduit sections for fresh heat exchange fluid (and again the distance between adjacent conduit sections for spent heat exchange fluid), is not substantially greater than l8 cm.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic illustration of a heatexchange system in accordance with the present invention;

FIG. 2 is a diagrammatic illustration showing a further heat-exchange system according to the invention; and

FIG. 3 is a Mollier diagram for humid air.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 I have illustrated a structural element 2, for instance a panel or plate, which is intended to constitute the exposed floor of a room (not shown). Such panel or plate may be cast of a hardenable material, for instance a synthetic as shown, concrete or other material, and embeds in it the main body portion of a conduit having an inlet portion 1 and an outlet portion 1". The embedded body portion of the conduit 1 has at least two sections, one being identified with reference numeral la and carrying the incoming heat-exchange fluid which enters through the conduit portion 1, whereas the other is identified with reference numeral lb and carries the spent heat exchange fluid which it receives from the section 10 and passes on to the outlet portion 1". For better identification, the section 1a is shown in broken lines and the section lb in solid lines. It will be seen that the sections 1a and lb are here shown in form of several convolutions, and that the number of convolutions may be greater or smaller than what has been illustrated. If each section 1a (and similarly lb) has two or more parallel subdivisions due to the presence of two or more convolutions, then these subdivisions of the same section should be advantageously spaced no more than the distance I apart from one another. with this distance not substantially exceeding 18 cm. It is advantageous if the sections 1a and lb are deposited on a somewhat diagrammatically illustrated steel reinforcing mesh 2' to which they are secured and together with which they are embedded in the material of the structural element 2.

Reference numeral 3 in FIG. 1 identifies a support, for instance a foundation of concrete or the like on which the element 2 is positioned. Interposed between the support 3 and the element 2 is an intermediate component 2" (which may be composed of a plurality of layers) for thermal insulating purposes, accoustical insulating purposes, and vapor-barrier purposes. The provision of the component 2" is known in the art and conventional.

The inlet portion 1' and the outlet portion 1" are connected via respective collecting receptacles 1" and 1" with a boiler 4 which in the illustrated embodiment is provided with a closed expansion vessel 4' and a safety valve 4". A pump 5 for cooling water is interposed in the inlet portion 1, together with a three-way mixing valve 6, which is connected via a branch conduit 6' with the outlet portion 1".

I have chosen to illustrate in FIG. 1 four different possibilities of providing a heat-exchange means for adjusting the temperature of the water to be passed through the conduit 1 to a desired level. It should be understood that each of the heat-exchange means, which are identified with

reference numerals

7, 8, 9 and 20, can be used individually or in any combination with any or all of the others. In other words, it is possible to use all four illustrated heat-exchange means in a single system, or to use any one of them individually or to use two or more of them in any desired combination.

Discussing firstly the means identified with reference numeral 7, it will be seen that this utilizes a conduit coil 7a (preferably of synthetic plastic material to avoid rusting) which is embedded in the soil 7 and is connected with the inlet portion 1 of the conduit 1 via a first conduit connection 7" and a second conduit connection 7". interposed between the locations where the

conduit connections

7 and 7" communicate with the conduit portion 1 is a valve 11 which is provided in the conduit portion 1'. interposed in the conduit connection 7" is a valve and interposed in the conduit connection 7" is a valve 10.

If the temperature of the water to be supplied to the sections la and lb is to be influenced with this heatexchange arrangement, then the valve 11 is closed, and the valves 10 and 10' are opened. Water circulated by the pump 5 now enters the connection 7" via the valve 10, passes through conduit coil 7a in which it is cooledv due to the coolness of the surrounding soil 7', and returns via the conduit connection 7' and the valve 7 downstream of the valve 11, into the inlet portion 1' from where it circulates first through the conduit section la and then the section 1b to return into the outlet portion 1. By the time the water reaches the conduit portion 1" it has of course warmed up, having absorbed heat from the material of the structural element 2. ltpasses now via the collecting receptacle 1" and the branch conduit 6' and valve 6 back into the pump 5 to begin its circulation anew. This particular arrangement is advantageous insofar as it requires no additional operating expenses, forinstance energy to operate a fan or the like, and in that particularly if the conduit coil 7a is of synthetic plastic material the installation is largely corrosion resistant and requires no maintenance.

The second heat exchange arrangement is identified with reference numeral 8,making use of the illustrated cooling tower which may be of any construction well known per se to those skilled in the art and which therefore requires no detailed discussion. The cooling tower is connected via the conduit connection 8 and the valve 8' with the conduit portion 1' upstream of a valve 12 interposed in the latter; the cooling tower is further connected with the conduit portion 1 downstream of the valve 12 via a conduit connection 8" and a valve 8". In this case, it is desirable to have the pump for the coolingwater located in the conduit portion 1 downstream of the juncture of the latter with the conduit connection 8", as indicated at 5'. When the valve 12 is closed the pump 5' draws cooling water via valve 8', conduit connection 8' through the cooling tower 8, and subsequently via the conduit connection 8" and the valve 8 into the conduit portion 1 to circulate it through the conduit 1 in the manner discussed previously. This arrangement has the particular advantage that the cooling capacity of the cooling tower can be precisely accommodated to the maximum cooling requirements anticipated, and that it is possible to cool the incoming fresh cooling water to a temperature of 2l C. when the ambient air has a temperature of 32 C. and a-relative humidity of 40 percent. For this reason, this second heat exchange arrangement is particularly advantageous where hotels, office buildings or the like are to be cooled with a heat-exchange system according to the present invention.

A third heat-exchange arrangement is identified with reference numeral 9, utilizing the diagrammatically illustrated heat pump which has been previously discussed. Essentially this arrangement provides an evaporator 9' interposed in the conduit portion 1' so that it can exchange heat with the cooling water passing through the latter, a compressor 9", a condenser 9" and a pressure reducing valve 9". Heat is withdrawn from the cooling water passing through the evaporator 9 by the cooling medium of the heat pump. This cooling medium evaporates and the vapor is drawn off the evaporator 9' by the compressor 9" and compressed to such an extent that it reaches an appropriate temperature. The compressed vapor is then supplied to the condenser 9" whose cooling surface area is of requisite size, and it is cooled by the diagrammatically illustrated blower. When it has been cooled it is then returned via the pressure reducing valve 9 as cooling medium condensate into the evaporator 9 where the cycle begins again.

Reference should be had in this connection to the embodimentillustrated in FIG. 2, where a particularly advantageous version of the novel heat-exchange system is illustrated, using the third heat-exchange arrangementof FIG. 1, or rather a somewhat different embodiment thereof. FIG. 2, wherein like reference numerals identify the same components as in FIG. 1, provides a heat pump in which the condenser 9" of the arrangement of FIG. 1 is replaced by a conduit coil 9" which is either embedded in the soil or is immersed in well water, in the water of a stream or the like. In other words, the requirement for supplying energy capable of operating the diagrammatically illustrated blower of the condenser in FIG. 1 has been eliminated.

interposed between the evaporator 9' in FIG. 2 and the compressor 9" there is provided a four-way valve 15,and two

pressure reducing valves

13 and 14 are interposed between the conduit coil 9" and the evaporator 9. Valves l3, 13', 14 and 14" are provided, permitting either the reducing

valve

13 or 14 to operate independently of the other.

With this arrangement, it is possible to both heat and cool via the novel heat-exchange system. If cooling is desired, then the heat pump acts as a refrigerator and the cooling medium therein flows through it in the direction indicated by the flow-line arrows. The device 9' acts as an evaporator and the conduit coil 9" acts as the condenser.

The same arrangement can, however, also serve to provide heating of the fluid circulating through the conduit 1. Thus, it can replace the boiler 4 which in the embodiment of FIG. 1 is provided to be able to use the system when it is desired to heat rather than cool the structural element 2. In the embodiment of FIG. 2, however, the heat pump itself can act to heat the cooling fluid, for which purpose it is merely necessary to operate the four-way valve 15 so that the direction of fluid circulating in the heat pump is now as indicated by the broken-line arrows of FIG. 2. In this case, the conduit coil 9" acts as the evaporator and the unit 9' acts as the condenser, meaning that heat is withdrawn from the soil in which the conduit coil 9 is embedded (or the water in which it is located), raised to a high temperature via the operation of the compressor 9" and then transmitted via the element 9' to the water circulating through the conduit portion 1' in heatexchanging engagement with the element 9. Because the surface temperature of the structural element 2 shown in FIG. 1 must not exceed a temperature of approximately 27-28 C., not only to provide a high degree of comfort for persons present in an enclosure in which the element 2 is provided but also in order to avoid the formation of stress cracks in the element 2, the water temperature in the incoming water circulating in the conduit portion 1 can be relatively low, because of this the heat-exchange system has a high efficiency both when the system of FIG. 2 is operated for cooling and when it is operated for heating purposes.

Returning to FIG. 1, it will be recalled that there is still a fourth heat-exchange arrangement illustrated in this Figure. This is identified with reference numeral 20, utilizing a receptacle preferably of synthetic plastic material. A conduit coil 20' is located in the receptacle 20 and connected with the conduit portion 1' so that when the valve 22 in the conduit portion 1 is closed and the mixer valve 22 is opened, the water passing through the conduit portion 1 will circulate through the conduit coil 20" under the influence of the pump 5.

A pump 23 is provided, for instance a submersible pump, which is located in the soil at an appropriate depth, such as to be able to withdraw groundwater, and this groundwater is then circulated via the pipe or conduit 23 into the receptacle 20 from where it is returned via the pipe or conduit 23 back to the groundwater. The return takes place at a sufficient distance from the intake of the pump 23 so that the latter will not draw in the warmer spent water which is being returned via the conduit or pipe 23. Of course, it is possible to discharge the water from the receptacle 20' to a point other than back to the groundwater but by so doing as shown in FIG. I, the groundwater level will not be dropped.

In this embodiment it will be appreciated that heat is exchanged between the groundwater circulating through the receptacle 20 and the cooling water circulating through the conduit coil 20, thereby cooling the cooling water which is then returned into the conduit portion 1' and circulates through the sections la and lb. This particular possibility has the advantage that the receptacle 20 can be positioned so as to be readily accessible, and that it as well as the conduit coil 20' are not subjected to any significant danger of mechanical damage and can also be readily cleaned if and when necessary. Furthermore, the mixing valve 22 makes possible an admixture of the warmer water in the incoming connection of the coil 20" with the cooler water which has been cooled in the receptacle 20', so that the temperature of the water which reaches the sections la and lb can be particularly easily regulated.

Coming, finally to FIG. 3, it will be seen that this is a Mollier-diagram wherein the advantages of the present invention are clearly evident. The curve a shown in the diagram is representative of the ambient air conditions which prevail in moderate climates on an average summer day. Given the conditions as set forth by the curve a and assuming that a room utilizing a structural element providing with the heat-exchange system according to the present invention receives fresh air, the ambient air in the room at the point A (see FIG. 3) would have a temperature of 32 C., 40 percent relative humidity and a dew point temperature of about l6,8C. In other words, the dew point temperature is that temperature below which the water contained in the air will condense on the surface of the element 2. Thus, it follows that the surface of the element 2 of FIG. I must not reach or drop below the dew point temperature of l6.8C. in the example. Quite surprisingly, however, I have found that with my novel heat-exchange system the temperature of the incoming cooling water, that is the cooling water which is supplied via the conduit portion 1 may actually be below the dew point, because due to the counterflow of water in the conduit sections 1a and lb (which are in heat-exchanging contact with one another), the temperature in the immediate vicinity of the sections la and 1b will still be above the dew point temperature (assuming that the temperature of the incoming water in the conduit portion 1 is not too far below the dew point temperature) This is true even if the room in which such a structural element is used receives fresh air directly from the exterior, that is ambient fresh air.

On the other hand, if the structural element is used in a room where provisions are made for dehumidifying the air, a temperature of the incoming cooling water in the conduit portion 1 of C. to C. and even slightly below is permissible, depending upon the condition of the air in the room, for instance at 25 C. and between 50-60 percent relative humidity, without having to anticipate that the exposed surface of the element 2 would reach the critical dew point temperature at which condensation could take place. This is graphically shown by the curve b in FIG. 3.

The present invention has other advantages beyond those which have already been pointed out. One of these is, for instance, the fact that the room temperature which is comfortable in a room whose temperature is being regulated with the heat-exchange system according to the present invention, can be higher than the temperature which is considered comfortable if one or the other of the air-conditioning systems known from the prior art is employed. This means, that the heatexchange system according to the present invention is capable of providing for a comfortable room temperature without requiring a dehumidifying system for the air in the room, and even at maximum cooling capacity at summer time, the critical surface temperature of the element 2 is reached if at all only on a very few days of the year. For instance it has been found that if the temperature of the incoming water in the portion 1 is 20C. resulting in a surface temperature of the element 2 of approximately 2324 C., a room provided with the element 2 could be maintained at a comfortable room temperature of 2728 C.

If the heat-exchange system according to the present invention is to be used in large installations, for instance for cooling large buildings or other structures, it is advisable to connect a plurality of conduits in parallel with one another, as is indicated in FIG. 1 by the two conduit portions 1, 1" and conduit portions 21', 21" of a second conduit. This permits the cooling of individual zones in such a structure to individual temperatures (and of course, the heating thereof, if desired) in dependence upon particular requirements, for instance the North, South, East or West exposure of a particular area of the structure.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a heat-exchange system, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can,

by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

l claim:

1. In a heat-exchange system, in combination, conduit means including a fluid inlet portion, a fluid outlet portion, and a main body portion adapted for embedding in a structural element, said main body portion including a first section having a first upstream end which communicates with said inlet portion and also having a first downstream end, and a second section extending along said first section and contacting the same in heatexchange surfact-to-surface contact over substantially the entire length thereof, said second section having a second upstream end communicating with said first downstream end and also having a second downstream end communicating with said outlet portion; circulating means for circulating heat-exchange fluid through said conduit means so that the fluid flows initially in one direction through said first section, and thereupon in counter-flow to said one direction through said second section; and heat-exchange means for adjusting the temperature of said heat-exchange fluid to a desired level.

2. In a system as defined in claim 1, wherein said circulating means is operative for circulating a cooling fluid through said conduit means.

3. In a system as defined in claim 1, wherein said heat-exchange means is interposed in said inlet portion of said conduit means.

4. In a system as defined in claim 3, wherein said heat-exchange means comprises a conduit coil adapted to be embedded in soil and connected in circuit with said inlet portion so that heat-exchange fluid circulates through said conduit coil.

5. In a system as defined in claim 4, wherein said conduit coil is of synthetic plastic material.

6. In a system as defined in claim 3, wherein said heat-exchange means comprises a cooling tower interposed in said inlet portion.

7. In a system as defined in claim 3, wherein said heat-exchange means comprises a heat pump including an evaporator and a condenser operatively associated with said evaporator and constituted by a conduit coil adapted to be embedded in soil.

8. In a system as defined in claim 7, wherein said conduit coil is of synthetic plastic material.

9. In a system as defined in claim 3, wherein said heat-exchange means comprises a heat pump operable for selective heating or cooling of said heat-exchange fluid at the will of a user.

10. In a system as defined in claim 3, wherein said heat-exchange means comprises a receptacle, a conduit coil located in said receptacle and connected in circuit with said inlet portion so that said heat-exchange fluid flows through said conduit coil, and supply means for passing a flow of cooling water through said receptacle in contact with said conduit coil.

11. In a system as defined in claim 10, wherein said receptacle is of synthetic plastic material.

12. In a system as defined in claim 3, wherein said heat-exchange means comprises a heat pump including an evaporator, and a condenser operatively associated with said evaporator and exposed to a stream of air.

13. In a system as defined in claim 1, wherein at least said conduit sections have an inner diameter of at most 25 mm.

14. In a system as defined in claim 1; further comprising additional conduit means parallelling the firstmentioned conduit means and also operatively associated with said circulating means and said heatexchange means.

15. In a system as defined in claim 13, wherein said sections each comprise at least a first portion and at least one second portion; and wherein said first portions are transversely spaced from one another by a distance not exceeding substantially 18 cm, and said second portions are also transversely spaced from one another by a distance not exceeding substantially 18 cm. l

Claims

1. In a heat-exchange system, in combination, conduit means including a fluid inlet portion, a fluid outlet portion, and a main body portion adapted for embedding in a structural element, said main body portion including a first section having a first upstream end which communicates with said inlet portion and also having a first downstream end, and a second section extending along said first section and contacting the same in heat-exchange surfact-to-surface contact over substantially the entire length thereof, said second section having a second upstream end communicating with said first downstream end and also having a second downstream end communicating with said outlet portion; circulating means for circulating heat-exchange fluid through said conduit means so that the fluid flows initially in one direction through said first section, and thereupon in counterflow to said one direction through said second section; and heatexchange means for adjusting the temperature of said heatexchange fluid to a desired level.

14. In a system as defined in claim 1; further comprising additional conduit means parallelling the first-mentioned conduit means and also operatively associated with said circulating means and said heat-exchange means.

15. In a system as defined in claim 13, wherein said sections each comprise at least a first portion and at least one second portion; and wherein said first portions are transversely spaced from one another by a distance not exceeding substantially 18 cm, and said second portions are also transversely spaced from one another by a distance not exceeding substantially 18 cm.