Patent Description:
Concerns related to global warming and increasing energy prices have heat pump technologies increasingly lucrative. In such systems energy is recovered from heat source by using compression-evaporation cycle. By these systems heat end energy can be collected from various sources even at very low temperatures. Typical energy sources are wastewater, exhaust air or gas flows, ground and water sources and air. The energy is collected to the compression-evaporation circuit by using a heat exchanger. various kinds of heat exchangers can be used for this purpose, the most usual types being plate- or tube heat exchangers. Typical materials are metals and plastics (polymers). When a heat exchanger is used in a cold environment, it should have a high heat transfer capability at low temperatures and good resistive for freezing. This makes designing and dimensioning such heat exchangers challenging.

Examples of heat exchangers for low temperatures can be found in <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

According to a first aspect of the present invention, there is provided a heat exchanger as defined in claim <NUM>.

According to a second aspect of the present invention, there is provided a method as defined in claim <NUM>.

There can be provided a heat exchanger wherein all major parts are made of plastic, at least the parts forming and within the flow path of the second liquid.

There can be provided a heat exchanger, wherein the heat exchanger tubing comprises a first coil tube coiled around the core and at least one second coil tube coiled around the first coil tube wherein the first end of the first coil tube is located at vicinity of the first end of the core and the first end of the second coil tube is located at a distance from the first end of the core that is greater than the distance between the first end of the first coil tube and the first end of the core so that the first ends of the coil tubes form a cone at the first end of the core and the second ends of the coil tubes are set on a same plane.

The heat exchanger tubing may comprise multiple successive coil tubes having first ends distanced gradually at longer distances from the first end of the core.

The length of each coil tube may be the same.

There can be provided a heat exchanger comprising at least one axial divider wall extending between the outer surface of the core and the inner surface of the body and having holes for coil tubes.

There can be provided a heat exchanger, comprising at least one radial divider extending from either the outer surface of the core or the inner surface of the body in between the coil tubes creating one or multiple flow paths for the second liquid.

There can be provided a heat exchanger wherein the axial dividers comprise multiple holes.

There can be provided a heat exchanger, wherein the coil tubes (<NUM>, <NUM>, 7xx) are single continuous pipes without splices or joints.

The heat exchanger described herein is primarily for collecting heat energy or for dissipating heat energy for cooling using sea- river or lake water or other water bodies having sufficient volume. The heat exchanger is usable in waters at low temperatures, even close to the freezing temperature. The heat exchanger is suitable for connecting to a heat pump system for either collecting heat to a heat pump circuit or for dissipating heat from the circuit. The heat exchanger has a flow path for the liquid from which the heat is collected or dissipated to formed so that the cross section of the flow path decreases in the flow direction, i.e. the direction on which the temperature of the second liquid decreases. A coil tube assembly for the first liquid is fitted in the flow path of the secondary liquid. The heat exchanger is preferably made of plastic, for example polyethylene or polypropylene.

<FIG> illustrates a heat exchanger in accordance with at least some embodiments of the present invention. At the centre of the heat exchanger is a cylindrical core <NUM>. A heat exchanger tubing <NUM> is arranged around the core <NUM> and the heat exchanger tubing <NUM> is forms an outer borderline defining the shape of the heat exchanger tubing <NUM>. The shape of the heat exchanger tubing <NUM> has a first part <NUM> formed as a cone and a second part <NUM> formed as a cylinder. The diameter of the cylinder is the same as the largest diameter of the cone, so these diameters match each other. A body <NUM> forms the outer casing of the heat exchanger. The outer surface of the body is cylindrical. The inner surface of the body is also cylindrical , but has a lining wall <NUM> extending from the inner surface of the cylinder towards the core <NUM>. The lining wall <NUM> forms a cone funnel over the heat exchanger tubing <NUM> and the inner shape of the lining wall <NUM> follows the outer border line of the heat exchanger tubing at a distance, placing the inner wall of the body <NUM> parallel at a distance from the outer borderline of the heat exchanger tubing <NUM>. The inner wall of the body <NUM> with the lining wall <NUM> and the outer surface of the core <NUM> form a flow path for a liquid. This liquid is the second liquid, that functions as a volume from which the heat is collected from or to which it is dissipated. The second liquid is usually water, as it is easily accessible in large enough volumes. However, any other liquid may be used, as long as the materials and structure of the heat exchanger is capable of handling such liquid, e.g. waste water, process water.

The second liquid is fed to the heat exchanger through an intake <NUM> that is placed over the top of the heat exchanger tubing <NUM> when the heat exchanger is in vertical position in relation to the ground, i.e. the central axis of the core and the heat exchanger being placed on a right angle in relation to the ground. From the intake <NUM> the second liquid flows on a screen <NUM>. The screen <NUM> is a plate having holes in it. This simple part effectively divides the second liquid over the heat exchanger tubing placed under it. The second liquid flows by the gravity downwards over the heat exchanger tubing and releases heat to the first liquid flowing in the heat exchanger tubing <NUM>. Consequently the temperature of the second liquid decreases. When the heat exchanger is used for cooling, the action is obviously the opposite. As the temperature decreases, the heat transfer to the heat first liquid decreases. However, as the second liquid flows downwards the cross section of the flow path decreases as the second liquid reaches the cone part formed of the conical first part <NUM> of the heat exchanger tubing <NUM> and the inner wall of the body <NUM>, formed at this section by the lining wall <NUM>. This causes the flow speed of the second liquid to increase, increasing the heat transfer and keeping it on a steady level over the heat exchanger tubing <NUM>. Another feature that is important when the heat exchanger is used in cold waters is that increasing flow speed reduces the risk of freezing that might occur when the temperature of the second liquid (water) is reduced. As the heat exchanger may be used even in cold waters having temperature only few degrees above zero, even at a range from <NUM>,<NUM> - <NUM>, freezing may be a problem. From the conical part of the body <NUM> the second liquid flows on the bottom reservoir <NUM> of the body <NUM> and exits via outlet <NUM>.

The operation and setup of the heat exchanger is described herein in a vertical mounting and operation position. The apparatus may be operated and mounted horizontally, for example, or on an angle to the ground. If such mounting positions are used, forced feeding of second liquid may be needed. This applies to all assemblies when sufficient flow speed can't be achieved by gravity. The force feeding may be accomplished by pumping or using a liquid source placed on an elevated position in relation to the heat exchanger.

The first liquid, i.e. the liquid used for collecting or dissipating the heat energy, is fed to the heat exchanger tubing <NUM> through a manifold <NUM> at the bottom reservoir <NUM>. The manifold <NUM> is connected to first ends <NUM> of each of the coil tubes <NUM>, <NUM>, 7xx of the heat exchanger tubing <NUM>. The feed pipe <NUM> of the manifold <NUM> runs from the manifold <NUM> through the core to the top of the heat exchanger and therefrom to other parts of the heating/cooling system. The second ends <NUM> of the coil tubes <NUM>, <NUM>, 7xx are connected through a collector <NUM> to an exit pipe <NUM>. The exit pipe also runs through the core <NUM>. The location and arrangement of each of the feeding and exit of the first and second liquids are described herein as they are in the apparatus used as an example. The arrangement of these connecting assemblies have to be designed to adapt to the apparatus they are connected to.

The structure of the heat exchange tubing <NUM> is described in the following referring to <FIG>. The core has axial brackets <NUM>. herein <NUM>, but other number might be used. On these brackets <NUM> are mounted axial divider walls <NUM>. These axial divider walls <NUM>?? divide the circumference of the heat exchanger tubing in sections, in this case quadrants. The coil tubes <NUM>, <NUM>, 7xx are mounted on these axial divider walls <NUM>?. Each axial divider wall <NUM> is built of mounting strips <NUM>. The mounting strips <NUM> have semi-circular seats <NUM> for a coil tube and fasteners for joining the mounting strips to the brackets and to each other. The seats may have other forms, for example oval or angular. It the seat doesn't adapt closely to the outer cross section of the coil tube, the seats allow passage of water between eh mounting strip and the coil tube. The fasteners may be of any convenient kind, for example snap-on clips, rivets, screws, or glue. However, metal parts should be avoided in order to prevent risk of freezing and corrosion. The first mounting strips <NUM> (<NUM> pcs) are fixed on the brackets of the core <NUM> and the first coil tube <NUM> is wound around the core <NUM> placing the coil tube in the seats <NUM> of the mounting strips <NUM>. The first end <NUM> of the first coil tube is placed closest to the first end <NUM> of the core <NUM>, i.e. closest to the bottom of the heat exchanger. The first coil tube <NUM> is would around the core until the top wherein the second end of the coil tube <NUM> is set on a set level. Now, the next mounting strip <NUM> may be attached to the previous one locking the first coil tube <NUM> on its place. The second coil tube <NUM> is would on the mounting strip <NUM>, but now the first end <NUM> of the second coil tube <NUM> is set further away from the bottom of the heat exchanger. The second end <NUM> of the second coil tube <NUM> is set on the same level as the first coil tube <NUM>. Further coil tubes 7xx are mounted in similar fashion by adding mounting strips and successive coil tubes. As the first ends <NUM> of the coil tubes are gradually distanced from the bottom of the heat exchanger, the first ends and first rounds of the coil tubes form a cone shape. The first purpose of this structure is to form said cone shape to accommodate the conical shape of the inner wall of the body. The second purpose is to enable using coil tubes having same length. As the diameter of the coil tube winds increases when successive coil tubes are added, it must be accommodated by shortening the number of winds in direction parallel to the core. This structure enables using coil tubes of equal length. As the lengths of the coil tubes are the same, the flow resistance is the same and no valves are needed to accommodate different flow resistances.

As described above, the first ends of the coil tubes are connected to a manifold <NUM> (<NUM>?) and the second ends to a collector <NUM>. The second ends of the coil tubes are set on a same level.

In order to obtain a consistent flow of liquid over the whole area of the heat exchanger tubing <NUM>, radial dividers <NUM> are set between the rounds of coil tubes. The radial dividers <NUM> are perforated plates mounted on axial divider walls <NUM>. by trusses <NUM>. The radial dividers <NUM> are set stepwise over the axial length of the heat exchanger tubing so that every other radial divider plate extends from the outer surface of the core <NUM> and every other from the inner wall of the body <NUM>. Each of the radial divider plates extend only partially over the radial distance between the inner wall of the body and the outer surface of the body creating stepwise winding flow path. In this way the second liquid is mixed and its temperature is evened out. More importantly, the flow speed over the flow path can be maintained sufficient for preventing freezing over whole are of the flow path. Also, mixed flow provides better heat transfer. One feature relates to perforations of the radial dividers <NUM>. The perforations allow second liquid to flow over the coil tube under the radial divider <NUM> so that the surface of the coil tube is not obscured by the axial divider plate.

The apparatus described above and depicted in the drawings is configured by using parts that have circular cross section. Such parts, like core, body and connecting pipelines can be conveniently obtained as they are or can be manufactured by using existing apparatuses of plastic industry. However, it can be contemplated that, for example, the core and body are made of parts having oval cross section. Such configuration may be needed to fit the heat exchanger in shallow heat sources. Any sharply angular cross sections like rectangular or hexagonal are to be avoided as they may create areas where flow speed is decreased, leading to decreased heat transfer and affinity to freezing.

The preferred material of the heat exchanger is plastic, in particular polyethylene (PE), polypropylene (PP). The parts contacting the second liquid, especially if it is water at low temperature, should be made of plastic. At higher temperatures this may not be essential. Metals also corrode. The bottom of the heat exchanger can be made of a panel made of plastic profiles, e.g. UPONOR WEHOPANEL® for example. The body may be made of tube made of wound profile. The second liquid is, for example ethanol. This allows for incoming temperatures of the first liquid as low as <NUM>,<NUM> - <NUM>. As example of the size of the heat exchanger dimensions of <NUM>,<NUM> diameter, up to <NUM> - <NUM> high, comprising <NUM> rounds of coil tubes each having length of <NUM> - <NUM>, can be given. However, the dimensions may be adjusted as required. The structure of the heat exchanger enables dismantling for maintenance and transfer. The apparatus can be operated by gravity or the pressure may be elevated by pumping.

The invention can be used for collecting or dissipating heat energy and for providing heat exchangers for collecting or dissipating heat energy.

Claim 1:
A heat exchanger comprising:
- a core (<NUM>)
- a heat exchanger tubing (<NUM>) for a first liquid,
- a body (<NUM>, <NUM>) surrounding the heat exchanger tubing (<NUM>), wherein the inner surface of the body (<NUM>) has the same shape as the outer borderline of the heat exchanger tubing (<NUM>), wherein the inner surface of the body (<NUM>) is formed as a shell around the heat exchanger tubing (<NUM>) and delineates with the core (<NUM>) a flow path for the second liquid, the heat exchanger being
characterized in that
- the core (<NUM>) is cylindrical and each coil tube (<NUM>, <NUM>, 7xx) is wounded parallel to the core (<NUM>),
- the heat exchanger tubing (<NUM>) has a first part (<NUM>) formed as a cone having first diameter and a second larger diameter, and a second part (<NUM>) formed as a cylinder having the same diameter as the second larger diameter of the cone.