FIELD OF THE INVENTION The present invention relates to cooling (or heating) systems. More particularly the present invention relates to a heat-exchanging device.
BACKGROUND OF THE INVENTION The continuing reduction in size of microelectronic components, such as chips, diodes, laser sources and other such devices, and the reduction in transistor rise time, presents a formidable challenge to the packaging industry. In order to facilitate effective near term utilization of the future microelectronic devices, the design and performance of first and second level packaging need a significant improvement with respect to the current state-of-the-art technology. Heat fluxes of various microelectronic devices exceeding 100 Watts per cm2 are currently considered in the art.
Various solutions for cooling microelectronic devices have been suggested in the literature and are known in the art. The following are examples of air cooling systems.
In U.S. Pat. No. 4,447,842 (Berg) finned heat exchangers for electronic chips and cooling assembly were introduced. It features a pair of heat exchange fins mounted on the electronic chip, each projecting through a groove and into a channel of a cooling module, and kept in contact with a cooling surface of that module.
In U.S. Pat. No. 4,535,386 (Frey et. al.) a natural convection cooling system for electronic components was disclosed. The electronic components were to be mounted at the base of an enclosure, at an opening of an inner chimney, which separates the interior of the enclosure into forward and rearward compartments. The inner chimney serves to duct the heated air rising from the electronic components to the top of the enclosure. A heat exchanger is placed at the top of that enclosure, to cool the heated air, resulting in a cooler air movement downwardly, and thus establishing natural air turbulence within the enclosure.
Another cooling system was introduced in U.S. Pat. No. 4,158,875 (Tajima et. al.). In this invention the air cooling of the electronic components is achieved by a double-walled duct construction whereby air, as a coolant, is introduced, in a direction at high angles to the length of the heat generating electronic components.
In U.S. Pat. No. 4,837,663 (Zushi et. al.) a cooling system for an electronic apparatus was disclosed. It included a plurality of motherboards, each having a circuit board to be cooled, a blower for causing airflow, and a duct for directing the airflow between the motherboards.
To-date cooling systems are not efficient enough when higher rates of heat dissipation from electronic components are considered, and as technology proceeded to introduce micro electronic devices with higher performance parameters, with subsequently higher heat dissipation, there is a need for more efficient cooling systems.
It is a purpose of the present invention to provide a novel heat-exchanging device for cooling high-power devices.
Another purpose of the present invention is to provide such heat-exchanging device of high efficiency, both for cooling and heating missions.
Yet another purpose of the present invention is to provide such heat-exchanging device of high efficiency for cooling and heating missions where the device is designed to exchange heat by placing it in contact with a high-power device or by submerging its heat-transfer surface to a fluidic medium (liquid or gas).
Another purpose of the present invention is to provide such heat-exchanging device of high efficiency where gases such as air or liquids such as water are used as a coolant fluid.
SUMMARY OF THE INVENTION There is thus provided, in accordance with some preferred embodiments of the present invention, a heat-exchanging device comprising:
a heat exchanging layer, made from heat conducting material, having a heat transfer contact surface and flow passages whose inlets and outlets are located on at least a first active surface that is substantially opposite the heat exchanging contact surface;
a manifold comprising a housing with a top cover, and alternating supply and evacuation substantially parallel channels, the channels having openings on a second active surface for fluidically communicating with the first active surface of the hear exchanging layer, each channel having at least another opening for coolant supply or for evacuating the coolant from the device,
whereby when the manifold and the heat exchanging layer are coupled and coolant fluid is supplied through the manifold, local U-shaped flow patterns are established in the heat exchanging layer, towards and away from the heat transfer contact surface.
Furthermore, in accordance with some preferred embodiments of the present invention, at least a portion of the heat exchanging layer and at least a portion of the manifold are integrated in one block.
Furthermore, in accordance with some preferred embodiments of the present invention, the heat-conducting material is selected from the group of materials containing Aluminum and Copper.
Furthermore, in accordance with some preferred embodiments of the present invention, the fluidic coolant is selected from the group containing: gas, air, liquid, water and two-phase fluid.
Furthermore, in accordance with some preferred embodiments of the present invention, the fluidic coolant is pre-cooled.
Furthermore, in accordance with some preferred embodiments of the present invention, supply channels of the manifold are connected to a high-pressure coolant fluid supply.
Furthermore, in accordance with some preferred embodiments of the present invention, evacuation openings are located on the top cover, for exhausting the coolant fluid away from the device.
Furthermore, in accordance with some preferred embodiments of the present invention, the manifold is connected to the high-pressure supply from one or more sides of the housing.
Furthermore, in accordance with some preferred embodiments of the present invention, evacuation channels of the manifold are connected to a low-pressure source for suction of the surrounding coolant fluid.
Furthermore, in accordance with some preferred embodiments of the present invention, openings of supply channels are located on the top cover for receiving surrounding coolant fluid.
Furthermore, in accordance with some preferred embodiments of the present invention, the manifold is connected to the low-pressure source from one or more sides of the housing.
Furthermore, in accordance with some preferred embodiments of the present invention, the coolant fluid is supplied to the manifold from a first side of the manifold and evacuated from a second side of the manifold.
Furthermore, in accordance with some preferred embodiments of the present invention, a driving source for providing pressure differences to drive the coolant fluid through the device are selected from the group containing: fan, diagonal fan, blower, pump, compressor, vacuum pump.
Furthermore, in accordance with some preferred embodiments of the present invention, the heat exchanging layer comprises a block having a plurality of U-shaped cooling tubes provided in it, each of the cooling tubes having an inlet section for receiving an inflow of the coolant fluid, an outlet section, substantially parallel to the inlet section, for evacuating the coolant fluid, and a connecting section in between, the inlet and the outlet of each cooling tubes are distributed on said at least first active surface, whereby when the manifold and the heat exchanging layer are coupled and coolant fluid is supplied through the manifold, the coolant fluid passes through the plurality of U-shaped tubes towards and away from the heat transfer contact surface.
Furthermore, in accordance with some preferred embodiments of the present invention, the active surface is staggered, whereby the inlets of the cooling tubes and the outlets of the cooling tubes are located at two planes, one of said planes is elevated in relation to the second plane.
Furthermore, in accordance with some preferred embodiments of the present invention, the vertical inlet sectors of the cooling tubes are of different length in relation to the vertical outlet sectors of the cooling tubes.
Furthermore, in accordance with some preferred embodiments of the present invention, the cooling tubes have a diameter that is not greater than 1 mm.
Furthermore, in accordance with some preferred embodiments of the present invention, the cooling tubes have a height that is not greater than 10 mm.
Furthermore, in accordance with some preferred embodiments of the present invention, the total area taken by the inlets and outlets of the cooling tubes amounts between 50 to 85 percent of the total area of the first active surface.
Furthermore, in accordance with some preferred embodiments of the present invention, the block is made from at least two adjacent sub-layers, a first sub-layer comprising a plurality of passing through tubes creating the inlet and outlet sections of each cooling tube, and a second sub-layer comprising a plurality of basins which are the connecting sections of the cooling tubes.
Furthermore, in accordance with some preferred embodiments of the present invention, inlets and outlets of the cooling tubes are arranged in alternating rows.
Furthermore, in accordance with some preferred embodiments of the present invention, inlets and outlets of the cooling tubes are arranged in adjacent twin-rows.
Furthermore, in accordance with some preferred embodiments of the present invention, inlets and outlets are arranged in a staggered formation.
Furthermore, in accordance with some preferred embodiments of the present invention, pairs of inlets of cooling-tubes are adjacent and fluidically communicating with a supply channel of the manifold and pairs of outlets of cooling-tubes are adjacent and fluidically communicating with a channel of the manifold.
Furthermore, in accordance with some preferred embodiments of the present invention, the cooling-tubes are distributed on the active surface at varying densities.
Furthermore, in accordance with some preferred embodiments of the present invention, the cooling tubes have elongated inlets and outlets sections.
Furthermore, in accordance with some preferred embodiments of the present invention, one or more connecting sections connect the inlet and the outlet sections of each cooling tube.
Furthermore, in accordance with some preferred embodiments of the present invention, the connecting sections of the heat exchanging layer comprise a plurality of channels, each of the channels fluidically communicating with a row of inlet and outlet sections of a row of cooling tubes, whereby local, aerodynamically separated, U-shaped flow patterns are established in the heat exchanging layer when coolant fluid is passed through.
Furthermore, in accordance with some preferred embodiments of the present invention, the heat exchanging layer comprises a plurality of exposed U-shaped cooling tubes, each of the cooling tubes having an inlet section for receiving an inflow of the coolant fluid, an outlet section, substantially parallel to the inlet section, for evacuating the coolant fluid, and a connecting section in between, the inlet and the outlet of each cooling tubes are distributed on said at least first active surface, whereby when the manifold and the heat exchanging layer are coupled and coolant fluid is supplied through the manifold, the coolant fluid passes through the plurality of U-shaped tubes facilitating cooling of a fluidic medium to which the device is exposed.
Furthermore, in accordance with some preferred embodiments of the present invention, the heat exchanging layer comprises a plurality of substantially parallel cooling fins defining a plurality of substantially parallel elongated channels with elongated openings facing the second active surface of the manifold, whereby when the manifold and the heat exchanging layer are coupled and coolant fluid is supplied through the manifold, local, aerodynamically separated, U-shaped flow patterns are established in the heat exchanging layer, towards and away from the heat transfer contact surface.
Furthermore, in accordance with some preferred embodiments of the present invention, the channels of the manifold are substantially orthogonal to the cooling fins of the heat exchanging layer.
Furthermore, in accordance with some preferred embodiments of the present invention, the heat exchanging layer of the device is integrated with a heat spreader of a heat dissipating device.
Furthermore, in accordance with some preferred embodiments of the present invention, the heat exchanging layer of the device is integrated with a surface of a heat dissipating device.
Furthermore, in accordance with some preferred embodiments of the present invention, the height of the cooling fins is in the range between 0.1 to a few millimeters.
Furthermore, in accordance with some preferred embodiments of the present invention, the density of the cooling fins is in the range between 5 to 100 fins per cm.
Furthermore, in accordance with some preferred embodiments of the present invention, the density of the manifold channels is in the range between 50 to 5 percent of the density of the cooling fins.
Furthermore, in accordance with some preferred embodiments of the present invention, the height of the manifold channels is in the range between 2 to 20 millimeters.
BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the present invention, and appreciate its practical applications, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the invention. Like components are denoted by like reference numerals.
FIG. 1a illustrates the basic cell of the heat-exchanger device having two internal U-tubes in accordance with a preferred embodiment of the present invention.
FIG. 1b illustrates a top view of the basic cell of FIG. 1a.
FIG. 1c illustrates a cross-sectional view of the basic cell of FIG. 1a.
FIGS. 1d-f illustrate U-tubes of rectangular cross-section and an exemplary way of implementation.
FIG. 2a illustrates the basic cell of the heat-exchanger device having two external U-tubes in accordance with another preferred embodiment of the present invention.
FIG. 2b illustrates a top view of the basic cell of FIG. 2a.
FIG. 2c illustrates a cross-sectional view of the basic cell of FIG. 2a.
FIGS. 3a-d illustrate the rule of multiplying the number of U-tubes within a heat-exchanger device, whilst at the same time reducing their dimensions.
FIG. 4a illustrates a schematic top view of a heat-exchanging device having feeding and evacuation coolant channeling in accordance with another preferred embodiment of the present invention.
FIG. 4b illustrates a schematic top view of the coolant feeding and evacuation arrangement shown in FIG. 4a.
FIGS. 4c-e illustrate some optional structures of fine delivery and evacuation channels.
FIG. 5a is a cross-sectional view of a local coolant feeding and evacuation channels for a heat-exchanging device in accordance with another preferred embodiment of the present invention.
FIG. 5b illustrates a schematic 3D of the coolant delivery channeling shown in FIG. 4a (up-side down).
FIG. 6a depicts a heat-exchanging device in accordance with a preferred embodiment of the present invention mounted over an electronic component (such as CPU) having similar dimensions having a structure of four layers.
FIG. 6b depicts a heat-exchanging device in accordance with a preferred embodiment of the present invention mounted over an electronic component (such as CPU) having similar dimensions having a structure of three layers.
FIG. 6c illustrates a 4-layers heat-exchanging device in accordance with another preferred embodiment of the present invention mounted over an electronic component (such as CPU) having smaller dimensions with respect to the heat-exchanging device.
FIGS. 6d-e illustrate optional setups of the heat-exchanging device on top of the heat-generating element, in accordance with a preferred embodiment of the present invention.
FIGS. 6f-h illustrate optional shapes of U-tubes design with respect to the active surface of a heat-exchanging device, in accordance with a preferred embodiment of the present invention.
FIG. 7a illustrates typical arrangement of U-tubes of a heat-exchanging device, in accordance with a preferred embodiment of the present invention.
FIG. 7b illustrates a proposed coolant delivery and evacuation ducting for a heat-exchanging device of FIG. 7a, in accordance with a preferred embodiment of the present invention.
FIG. 8a illustrates a multi-zonal arrangement of U-tubes of a heat-exchanging device, in accordance with another preferred embodiment of the present invention.
FIG. 7b illustrates a proposed coolant feeding and evacuation ducting for a heat-exchanging device of FIG. 8a, in accordance with a preferred embodiment of the present invention.
FIG. 9a-c illustrates various U-tube's basic cell arrangements in accordance with some preferred embodiment of the present invention.
FIG. 10a illustrates an electronic component with localized hot spots, typically hotter than other zones on that component.
FIG. 10b illustrates a proposed U-tubes arrangement of a heat-exchanging device, with corresponding varying density (with respect to the component of FIG. 10a).
FIG. 11 illustrates a cooling system for servers based on a plurality of U-tubes heat-exchanging devices, in accordance with a preferred embodiment of the present invention.
FIG. 12 is a table showing optimized data resulted from virtual prototyping simulation of a heat-exchanger device having optimized U-tubes for different supply pressure.
FIG. 12a defines the parameters L and D associated with the table shown in FIG. 12.
FIG. 13 is a graph showing the calculated optimized heat removal of the heat-exchanger device having optimized U-tubes for different supply pressure.
FIG. 14a illustrates a heat-exchanger device in accordance having through-tubes (I-tubes) with yet another preferred embodiment of the present invention.
FIG. 14b illustrates a single cooling fin of the heat-exchanger device shown in FIG. 14a (cross-section A-A in FIG. 11a).
FIG. 14c illustrates I-tubes arrangements with fine and coarse density for the cooling fins of the heat-exchanger device shown in FIG. 14a.
FIG. 14d illustrates a 3D view of the heat-exchanger device shown in FIG. 14a.
FIG. 14e illustrates a cross-sectional view of the heat-exchanger device shown in FIG. 14a, mounted over an heat-generating element (such as CPU).
FIG. 15 illustrates a U-tubes heat-exchanging device, in accordance with a preferred embodiment of the present invention.
FIG. 16 illustrates a heat-exchanging device having engaged U-tubes construction, in accordance with another preferred embodiment of the present invention.
FIG. 17 illustrates a heat-exchanging device with elongated U-tubes, in accordance with another preferred embodiment of the present invention.
FIG. 18 illustrates a heat-exchanging device similar to the one shown in FIG. 17 where the fine manifold extend from one side to another side of the heat-exchanging device, in accordance with another preferred embodiment of the present invention.
FIG. 19 illustrates a heat-exchanging device similar to the one shown in FIG. 18 where deeper horizontal connecting tubes are applied, in accordance with another preferred embodiment of the present invention.
FIG. 20 illustrates a heat-exchanging device, where a crossing channel is applied at a lower layer of the heat-exchanging device to establish local U-shaped flow patterns, in accordance with a preferred embodiment of the present invention.
FIG. 21 illustrates a heat-exchanging device similar to the one shown in FIG. 20, but with alternating rows of vertical supply tubes and vertical evacuation tubes, in accordance with a preferred embodiment of the present invention.
FIG. 22 illustrates a general view of Crossing-channels in a heat-exchanging device, in accordance with a preferred embodiment of the present invention.
FIGS. 23a-b schematically depict several fluid-flow aspects related to the Crossing-channels heat-exchanging device shown in FIG. 22.
FIG. 24 illustrates top views and cross-sectional views of the Crossing-channels of the heat-exchanging device shown in FIG. 22, in accordance with a preferred embodiment of the present invention.
FIG. 25a illustrates a possible implementation of a stand-alone Crossing-channels heat-exchanging device, in accordance with a preferred configuration of the present invention.
FIG. 25b illustrates another possible implementation the Crossing-channels heat-exchanger where the cooling fins are integrated on top of a heat-spreader, in accordance with another preferred configuration of the present invention.
FIG. 25c illustrates another possible implementation the Crossing-channels heat-exchanger where the cooling fins are integrated on top of the heat-generating device, in accordance with another preferred configuration of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention typically relates to a heat-exchanging device, aimed in particular at cooling electronic components (such as PC CPUs and main-frames or server's CPUs, electro-optic component that waste heat at small area and other general purpose heat-dissipating electronic components). Hereafter we shell refer only to cooling missions although the heat exchanger of the present invention may be implemented for heating missions too.
In principle, a heat-exchanging device in accordance with some preferred embodiments of the present invention comprises a block having at least two surfaces. One surface is subjected to a heat flux (to be refer to as the HT (heat-transfer) surface), for example by attaching it to a heat dissipating element, and a substantially opposite active surface. The block constitutes the heat exchanger body, and is made of a heat-conducting material with a plurality of small cooling tubes provided in it, each of the cooling tubes having an inlet for an inflow of the coolant fluid and an outlet for evacuating the coolant fluid. The cooling tubes are distributed on the block surfaces or surfaces which are generally substantially opposite the heat-transfer surface (or surfaces)—to be refer as the active surface. The cooling tubes are oriented, at least at portions near the inlets and outlets, substantially normal to the active surfaces, so as to allow local heat-exchanging by the coolant fluid that is passed through each of the cooling tubes. A coolant fluid supplier, fluidically connected (optionally by an integral manifold) to the inlets of each of the cooling tubes, so as to drive the coolant fluid through the cooling tubes.
The heat-exchanging device of the present invention can also be a large device that may effectively be used for general-purpose industrial heat-exchange applications, for both heating and cooling. In the present specification we shell specifically refer to cooling, but heating applications are applicable too, as heat exchange deals with both.
A main aspect of the cooling device in accordance with the present invention is the implementation of various arrangements of heat-exchanging devices to meet specific heat-exchange requirements.
An important aspect of the heat-exchanging device in accordance with the present invention is the provision of a heat-exchanger comprising a body, made of heat-conducting materials known in the art (for example, Aluminum or Copper) incorporating a plurality of ducts, significantly increasing the overall external surfaces of the body.
Another main aspect of the present invention is the provision of a flow of coolant gas or fluid through the ducts for acquiring heat from the body and evacuating it away.
Reference is made to FIG. 1a illustrating a concept for a heat-exchanger device in accordance with a preferred embodiment of the present invention where internal U-tubes are implemented.
A basic cell of heat exchanging device 10 in accordance with a preferred embodiment of the present invention comprises a small portion of the main body 22 of the heat exchanger of the present invention (here depicted in the form of a rectangular block, but the shape may vary) made form a heat-conducting material with two U-tubes 14 provided in the body. Each duct has an inlet 16 and outlet 18. Both are located on the active surface 17 of 10. The heat flux 11 of the object to be cooled is coming from the HT-surface 19 which is the bottom surface of 12.
The twin U-tubes of the basic cell shown in FIG. 1a are U-shaped, but other general shapes are possible too. By “U-shaped” is meant, for the purpose of the present invention, any shape that facilitates directing a coolant towards and then away from the contact surface of the heat-exchanging device. This may include, for example (but not limited to using letter-shapes), U-shape, J shape, V-shape, etc.
A heat-exchanging coolant fluid (for heating or cooling), which may be gas (for example, Air, Helium or Nitrogen but other coolant gases may be used too) or liquid (for example, Water, Oil, but other liquid coolants may be used too), is passed through the U-tubes and exchanges (absorbs or delivers) heat and is then evacuated away from the U-tubes. For the purpose of the present invention, by “cooling” is meant both cooling and heating, in other words any heat transfer or exchange.
The coolant may also comprise a mixtures of fluids, single phase or twin-phase of fluids may be implemented, and it may also include phase changes to enhance heat-transfer. The overall internal surface of the plurality of U-tubes that is densely distributed over the heat-exchanging active surface 17 (see for example FIG. 3d) creates high potential of heat removal associated with the heat-exchanger of the present invention.
The heat exchanging takes place when the heat exchanger is adjacent to a heat-dissipating device (such as a CPU) and the heat-flux from that device, denoted by Q (11) passes into body 12, through the heat transfer (HT) surface 19. As the coolant is passed through the U-tubes, it absorbs the heat and evacuates it away.
FIG. 1b illustrates a top view of the basic cell 14 shown in FIG. 1a. FIG. 1c illustrates a cross-sectional view of the basic cell 14 shown in FIG. 1a. Note that for practical purposes, the U-shaped duct may be easily manufactured by producing a first block 13 perforated with ducts passing through it and a second block 15 of corresponding concave basins (dents), and coupling the two blocks together so that U-shaped ducts are formed within.
The cross-section area of the U-tubes and their shape may vary downstream. FIG. 1d illustrates in accordance with another preferred embodiment of the present invention a general view of U-tubes 14c and 14d that have rectangular shape, where U-tubes 14c (the connecting-channels between the inlet 16 and the outlet 18) have a more rounded shape. Both tube embodiments (14c and 14d) have a rectangular cross-section. Such U-tubes may be created for example by attaching a plurality of parallel plates as shown in FIG. 1f, oriented at a general direction that is perpendicular both to the active surface 17 and the HT-surface 19 where plates 13v encase in between them the U-tubes, fine delivery channels (44) and the fine evacuation channels (46), and intermediate dividing plates 15v encasing only the fine delivery channels (44) and the fine evacuation channels (46).
A three-dimensional version of U-tubes 14e is shown in FIG. 1d to indicate that the centerline of the U-tube (with respect to its cross section) may not belong to a plane.
Reference is made to FIG. 2a illustrating a heat-exchanger device in accordance with another preferred embodiment of the present invention where external U-tubes are implemented. This version of the heat-exchanger of the present invention is capable of removing heat from a fluid as it is placed with its U-tubes submerged in that fluid.
A basic cell of heat exchanging device 20 in accordance with another preferred embodiment of the present invention comprises a small portion of the main body 22 of the heat exchanger of the (here depicted in the form of a rectangular box, but the shape may vary) preferably made form a heat-conducting material with two external U-tubes 24 provided in the body. Each U-tube has an inlet 16 and outlet 18, both located on the active surface 27 of 20. In this case the U-tubes 24 are exposed extending from the HT-surface 29 and the heat flux Q (21) is absorbed mostly through the outer surface of 24.
FIG. 2b illustrates a top view of the basic cell 24 shown in FIG. 2a. FIG. 1c illustrates a cross-sectional view of the basic cell 14 shown in FIG. 2a. One can see the advantage of the embodiment shown in FIG. 2a in dealing with heat-flux Q not only from the bottom, but also from the surrounding space. This embodiment would be recommended for use when the ambient atmosphere (or other gas or fluid) needs to be cooled or heated using the device of the present invention.
FIGS. 3a through 3d illustrate, with respect to a preferred embodiment of the present invention, a possible principle of increasing the number of U-tubes within a single heat-exchanger device, whilst at the same time the U-tubes dimensions are scaled down in such a way that the weight of the heat-exchanger device is kept relatively constant but the overall internal surface area of the plurality of U-tubes of the heat-exchanger device is substantially increased. In FIG. 3a the heat-exchanger device 30a comprises of one basic cell with two U-tubes similar to the one shown in FIG. 1. FIG. 3a shows more dense heat-exchanger device 30b having 8 U-tubes. In fact, device 30b includes 4 basic cells. Devices 30a and 30b are of similar sizes and thicknesses, but the U-tubes of 30b are smaller by factor of two whereas the number of U-tube is increased by a factor of four. Accordingly the internal surface area of the heat-exchanger device 30b is increased by factor of 2 with respect to 30a. Similarly, the heat-exchanger device 30c (FIG. 3c) has 64 U-tubes and the internal surface area of the heat-exchanger device 30c is increased by a factor of four with respect to 30a. The heat-exchanger device 30d (FIG. 3d) has 128 U-tubes and the internal surface area of the heat-exchanger device 30d is increased by a factor of 8 with respect to 30a.
For reasons of clarification, in FIGS. 3a-d a dashed line was used to draw the outlets of the U-tubes, and it was further applied when necessary in the following figures.
When going to more and more dense arrangements, very high number of smaller and smaller U-tubes may be provided in a heat-exchanger device of the present invention. Typically for CPU cooling (without derogating the generality), the U-tube inlet & outlet diameter is between 0.8 mm to 0.16 mm and accordingly as much as 50 to 1200 inlets and outlets are provided in one square centimeter (see also the table shown in FIG. 13).
It is evident that reducing the dimensions of the ducts to a miniaturized scale provides substantially greater internal surface for the heat-exchanging body. By “internal surface” is meant the entire surface of the body coming in contact with the coolant. Obviously, the greater that surface the more efficient the heat-transfer is to (or from) the coolant agent but also pressure losses may by considered with respect to the optimization of the heat-exchanger device of the present invention.
FIG. 4a illustrates a schematic top view of a heat-exchanging device in accordance with a preferred embodiment of the present invention. In this embodiment integral delivery and evacuation channeling of the coolant is presented. The heat exchanger 40 having a large number of U-tubes (see for example FIG. 5a) gets the coolant through a tree-like channeling where each of the u-tubes is fed by one of a plurality of fine integral channels 44 that are attached to the active surface 17 of 40. The fine delivery channels 44 are connected to the main delivery manifold 42 that is connected to an air (or other coolant) source such as fan, blower or pump that provides a predetermined mass flow rate at a predetermined pressure drop. Optionally, evacuation channeling may be applied, whereby a tree-like channeling where each of the u-tubes is connected to one of a plurality of fine integral channels 46 that attached to the active (top) surface 17 of 40 is used. The fine evacuation channels 46 are connected to the main evacuation manifold 48 that removes the already heated coolant away, preferably to the ambient atmosphere or further away (meaning that the heated coolant is not recycled and therefore has no heating effect on the device).
Alternatively, vacuum pump or any other suction device may be used to provide the pressure drop for driving the coolant through the heat exchanger of the present invention. In that case the evacuation channeling must be applied (for example when sucking and using the surrounding air as coolant) and adding delivery channels becomes an option only. It has to be emphasized that in some applications both blowers (or pumps) at the entrance to the delivery channels and vacuum means at the exit of the evacuation channels may be used.
FIG. 4b is another schematic top view of the delivery and evacuation channeling shown in FIG. 4a. The main delivery manifold 42 is fluidically connected to a plurality of fine delivery channels 44, and channels 44 are fluidically connected to each of the inlets 16 of the heat exchanger device 50. The main evacuation manifold 48 is fluidically connected to a plurality of fine evacuation channels 46, and channels 46 are fluidically connected to each of the outlets 16 of the heat exchanger device 50. In this arrangement, inlets 16 of two adjacent rows of U-tubes are juxtaposed, being fed through one delivery channel thus cutting to half the number of fine delivery channels, and the same is valid with respect to the evacuation channels. Notice that the evacuation and the fine delivery channels may both be applied in the same layer, thus presenting a structure of 3 layers.
The fine delivery channels 44 and 46 at FIG. 4b can be designed by applying uniform cross-section distribution as shown in FIG. 4c. However, in order to reduce pressure losses it is beneficial, with respect to a preferred embodiment of the present invention, to apply convergence cross-section distribution for the fine delivery channels and divergence cross-section distribution for the fine evacuation channels as shown in FIGS. 4d and 5e. In FIG. 4d the cross-sections 44a and 46a are distributed by changing the width of channels 44 and 46 while keeping the height constant and in FIG. 4e the cross-sections are distributed by changing both the width and the height of channels 44 and 46. The following comments are useful for better understanding of FIG. 4c-e
-
- The divergence and convergence are related to the direction of the flow.
- The area of each pair of cross sections (of 44a and 46a) at the cross-flow plane is constant and therefore it is a tradeoff matter of how to distribute the area between 44 and 46.
- The cross sections shaded by diagonal lines are the solid end of the channels.
- The elongated rectangular opening of all channels shown in FIG. 4c-e are similar (see also FIG. 4b). Notice that these channels are facing the active-surface of the heat exchanger device of the present invention and are fluidically connected to the inlets and the outlets of the cooling tubes.
FIG. 5a illustrates a cross-sectional view of the heat-exchanger device with respect to a preferred embodiment of the present invention including the delivery channeling and evacuation openings. This embodiment comprised of 3 attached blocks, the first block 13 of passing through ducts, a second block 15 of corresponding concave basins (both creating the plurality of U-tubes), and the third one is block 54 that includes a plurality of fine delivery channels 44 and openings 55 for evacuation. Here the fine delivery channels 44 are connected to the inlets 16 of U-tubes 14 and the heated coolant is evacuated from surface 56 of block 54. However, by adding another layer (59, not attached in the figure for reason of clarity, but in reality it is attached), evacuation channeling may be easily applied, thus creating a four-layer structure.
FIG. 5b illustrates 3 dimensional view of the delivery channeling of FIG. 4a. It is an up-side-down drawing that shows the plurality of inlets 16 of the U-tubes fluidically connected to the fine delivery channels 44 and the plurality of channels 44 that are fluidically connected to the main delivery manifold 42.
FIG. 6a depicts a heat-exchanging device 60a based on U-tubes in accordance with a preferred embodiment of the present invention, mounted over an electronic component 66 (CPU) on board 68 where a heat spreader 64a made of conductive material exists between 66 and 60a (U-tubes block 62 of 60a is in fact attached to 64a). This is a schematic drawing showing two levels of fine channels where the fresh air supply is delivered by the fine delivery channels block 44 that is attached to the U-tubes black 62 and fluidically connected to the inlets of each of the U-tubes. Hot air emerging from the U-tubes outlets is evacuated by the fine evacuation channels block 46 on top of 44. The main fresh air supply manifold 42 is fluidically connected to each of the fine delivery channels of 44, and the main evacuation manifold 48 is fluidically connected to each of the fine evacuation channels of 46, where channels 46 may exhaust the hot air to any desired space, preferably to a far environment.
FIG. 6b depicts a heat-exchanging device 60b based on U-tubes in accordance with another preferred embodiment of the present invention, mounted over an electronic component 66 (CPU) on board 68 where a heat spreader 64 is placed between 66 and 60b. Device 60b differs from device 60a of FIG. 6a only in using one layer of fine channels (44+46) as shown in FIG. 4a, thus reducing the overall width of 60b with respect to 60a.
FIG. 6c depicts a heat-exchanging device 60c based on U-tubes in accordance with another preferred embodiment of the present invention, mounted over an electronic component 66 (CPU) on board 68 where a heat spreader 64b placed between 66 and 60c. 60c has a similar stricture to device 60a of FIG. 6a but the heat spreader 64b has larger dimensions than 66. Accordingly the dimensions of 62 are enlarged also. Without derogating generality, a typical ratio between the top surface area of 66 and the effective area of 60c (i.e. the HT-surface 19 of FIG. 1) can be as much as 8:1 in case of CPU cooling.
FIG. 6d illustrates in accordance with a preferred embodiment of the present invention a planar setup 60d where a flat heat-exchanging device 62 is mounted over a flat electronic component 66 (for example, a CPU) and a flat heat-spreader 64 is placed in between them. This is a common setup where the HT-surface 19 and the active surface 17 of 62 are flat, but other alternatives of non-planner setups are possible too, as shown in FIG. 6e. FIG. 6e illustrates in accordance with another preferred embodiment of the present invention a non-planar setup 60e where two flat heat-exchanging devices 62 are mounted at an angle of inclination over a flat electronic component 66 (for example, a CPU) and a heat-spreader 64 in between them where 64 is flat from the “CPU side” and have two incline HT-surfaces 19 where 62 are mounted.
FIG. 6f illustrates, in accordance with a preferred embodiment of the present invention, a cross sectional view of a heat-exchanging device 60f, in accordance with another preferred embodiment of the present invention, built of two jointed blocks 13 & 15 (see FIG. 1). This cross sectional view includes a row of a plurality of U-tubes 14, where the both the inlets and the outlets of the U-tubes are located at the active-area 17 of 60f. However, FIG. 6g illustrates, in accordance with another preferred embodiment of the present invention, a cross sectional view of a heat-exchanging device 60g, built of two jointed blocks 13 & 15. This cross sectional view includes a row of a plurality of U-tubes 14a that are shaped like the letter “J” where the conduit leading to the outlet of each of the U-tubes is significantly longer than the conduit extending form the inlet. Accordingly, the actives surface of the heat-exchanging device 60g has two levels, 17b where the inlets of the U-tubes are located and 17a where the outlets of the U-tubes are located. Both 17a and 17b are parallel and oppose the HT-surface 19, similar to FIG. 6f. Moreover, this structure creates elongated cavities 63 (i.e. long cavities in the direction perpendicular to the plane of the drawing), thus block 13 is an integral structure that includes fine delivery channels (meaning cavities 63), yet a cover that may include fine evacuation channels has to be added. Another option is to join two outlet conduits than each two outlets 65a at 17a will be merged to one (65b) thus reducing the pressure losses. FIG. 6h illustrates, in accordance with another preferred embodiment of the present invention, a cross sectional view of a heat-exchanging device 60h, built of two jointed blocks 13 & 15. This cross sectional view includes a row of a plurality of U-tubes 14b that are shaped like the letter “V” where the actives surface 17 of the heat-exchanging device 60g is staggered, presenting a non-continuous plane.
FIG. 6g illustrates, in accordance with another preferred embodiment of the present invention, a cross sectional view of a heat-exchanging device 60g, built of two jointed blocks 13 & 15. This cross sectional view includes a row of a plurality of J-like cooling tubes 14a where the outlet conduit of each of the U-tubes is longer than the inlet conduit of each of the U-tubes.
FIG. 7a illustrates, in accordance with a preferred embodiment of the present invention, a top view of a heat-exchanging device 70, i.e. the active-surface 17 of 70. In this embodiment two close U-tubes are arranged in opposing rows thus each U-tube inlet 16 belongs to a row of two inlets and each U-tube outlet 18 belongs to a row of two inlets. Accordingly the number of fine channels may be reduced by a factor of 2, as shown in FIG. 7b. FIG. 7b illustrates, in accordance with a preferred embodiment of the present invention, delivery and evacuation channeling, with respect to the U-tubes arrangement of FIG. 7a, where the fine delivery channels 42 supply the fresh coolant to the heat-exchanger device 72 and each of channels is fluidically connected to half of the row of two U-tubes inlets, as it this arrangement there are two main delivery manifolds 44 on opposing sides of 72. In this arrangement, the pressure drop may be significantly reduced due to (1) an increase in the cross section area of 42, when it delivers coolant to two rows of U-tubes (see FIG. 7a), and (2) by reducing to half the mass flow rate through 42, when applying two main delivery manifold 42. The outlets rows of 72 may be fluidically connected to the fine evacuation channels 46 and each of 46 may be fluidically connected to the main evacuation manifold 48.
FIG. 8a illustrates, in accordance with another preferred embodiment of the present invention, a top view of a heat-exchanging device 80, i.e. the active-surface 17 of 80. In this embodiment the U-tubes are arranged in four quarters, where in each of the quarters the arrangement of U-tubes is similar to the arrangement shown in FIG. 7a. Such an arrangement provides the option to apply the fine delivery channels 42 from all sides as shown in FIG. 8b.
FIGS. 9a-9c illustrate, in accordance with preferred embodiments of the present invention, several packaging approaches. FIG. 9a shows a rectangular basic cell arrangement 92 where the overall area of both the inlet 16 and the outlet 18 of the U-tubes 14 occupies less than half of the active surface 17 as applied in the heat-exchanging device 93. FIG. 9b shows a rectangular basic cell arrangement 94 where the overall area of both the inlet 16 and the outlet 18 of the U-tubes 14 occupies more than half of the active surface 17 as applied in the heat-exchanging device 95. In such a rectangular arrangement, the overall area of the U-tubes inlets and outlets is limited to about 66% of the active surface 17 of 95. However, FIG. 9c shows a staggered (or hexagonal) basic cell arrangement 96 where the area of both the inlet 16 and the outlet 18 of the U-tubes 14 occupies much more than half of the active surface 17 as applied in the heat-exchanging device 97. In such a staggered arrangement, the overall area of the U-tubes inlets and outlets may be increased to about 80% of the active surface 17 of 97.
FIG. 10a illustrate, a typical case where the top surface heat flux of an heat-generating element 100 (for example, a CPU) is not uniform, and in particular hot-spots exist at restricted areas 102 where the heat flux are significantly intensive with respect to the average heat flux of 100. Accordingly, a non-uniform heat-exchanger device may be designed as shown in FIG. 10b. FIG. 10b illustrates in accordance with a preferred embodiment of the present invention a heat-exchanging device 104 with a special U-tubes arrangements. In most of the active area 17 (i.e. areas 108) of 104, low-density arrangement of U-tubes is applied, but at restricted areas 106 of 17 high-density arrangement of U-tubes is applied in order to provide local high heat-removal performance in accordance to the hot-spots of the heat-generating element 100 shown in FIG. 10a.
The heat-exchanger device of the present invention may be operated at different operational conditions and provide increasing performance in terms of heat-removal per unit of area with respect to the operational pressure. The heat-exchanger device is an ideal heat-exchanger with respect to the heat-capacity of the coolant liquid but from practical system considerations, without derogating generality, an optimized heat-exchanger device may reach a cooling efficiency that is in the range of 75-100% of the ideal cooling potential. FIG. 11 shows simulated prototype results of the performance of an optimized heat-exchanger device with respect to the pressure supply for air-cooling at temperature gap of 30° K (i.e. the temperature gap between the heat-generating element and the colder air). Due to early optimization considerations (minimizing pressure losses through the U-tubes), the results were obtained for the case where the overall area of the inlets and the outlets of the U-tubes occupies 70% of the active area of the heat-exchanger device. It is clearly seen that the greater the pressure supply, the significantly lower the heat transfer per unit of area is. Practically speaking, air supply of up to few millibars (1 millibar=100 Pascal) is typical for desktop CPUs cooling (fans and small blowers) where heat transfer rates of up to 10 watts/cm2 meet the cooling requirements, and air supply of up to few tens of millibars is typical for desktop main-frames and servers (i.e. system with large number of CPUs) cooling (including blade servers and communication oriented servers where the task of cooling are not only dedicated to CPU cooling). However, the potential of extremely large heat-removal per unit of area cooling performance at higher air pressure supply is clearly seen from FIG. 11, in particular at compressible flow (above 300 mbar) where heat-transfer enhancement exists due to compressible effects of fluid flow expansion. It has to be emphasized that pre-cooling of the coolant may enhance the heat removal performances. In addition, it has to be emphasized that the coolant may be any practical liquid and not only air, for example, heat transfer rate of 3000 watts/cm2 and more may be provided when using high pressure water as the coolant used in the heat-exchanger device of the present invention.
The simulated results (as shown in FIG. 11) provide also various indications that may be used in the design of an optimized heat exchanger device. FIG. 12 presents a table of optimized data for increasing pressure supply of coolant (air). It has to be emphasized that the data presented at this table is of typical values that may used as guide-lines for a design but for many practical applications, with respect to system and compactness considerations, changing the optimized geometrical parameters (such as D—diameter and L—length—, see FIG. 12a) even by a factor of 2 or more may provide a well functioning heat-exchanger device. The simulated results clearly indicate that:
-
- As the pressure increases, the Inlets/outlets diameter D of the U-tubes must be reduced for optimal heat-exchanger design.
- As the pressure increases, the length L of the inlets/outlets conduits of the U-tubes must be increased for optimal heat-exchanger design (for a U-shaped tube, L is the height of the tube, i.e. about a half of the length of the entire tube, neglecting the bottom lateral portion).
- Accordingly the ratio L/D must rapidly increase as the pressure (of the supplied fluidic coolant) increases.
- As D decreased, greater number of U-tubes per unit of area (see coulomb “N” in the table) must be provided to obtain optimal heat-exchanger design.
- Similar to the performance graph shown in FIG. 11, the heat transfer rates (HT) are significantly increased as the pressure increases.
- The optimization suggests that as the pressure increased and D decreases, the efficiency of the heat removal (HTeff) with respect to the full potential of cooling (i.e. ideal cooling where the coolant temperature at the U-tubes exit is equal to the temperature of the heat-generating element), may reduce by 2-23% from ideal values. It is due to the fact that when trying to increase that efficiency, the mass flow rate is reduced as pressure losses are increased and the overall effect is reducing of heat-removal performance (at a given pressure supply).
Note that by the word “diameter” relates, in the context of the present specification, to any shape of the inlet and the outlet, and specifically with respect to FIG. 12, it relates to the diameter on the surface (even if it is different further downstream).
FIG. 13 illustrates, with respect to a preferred embodiment of the heat-exchanging system of present invention a typical cooling system for providing heat removal to main-frames or servers (including blade-servers or server that used for communication duties). In such as server a plurality of CPU are assembled in one system, and it may involve additional cooling needs such as other heat generating elements, for example video cards, graphic chips (or graphic engines), as well as broad-bend communication cards, and central power-supply unit. FIG. 13 illustrates a blade-server architecture, where a plurality of motherboards (being the “blades”) each equipped with one or several CPUs and optionally other heat-dissipating elements. The motherboards are vertically assembled substantially in parallel within one enclosure (or drawer). Typically a blade-server system may include several enclosures rack mounted one above the other in one frame. For simplicity, the cooling system 200 includes several blades 210 of only one enclosure, each of it includes one CPU having an integral heat-exchanger according to the present invention on top of it, 201 (notice that more than one CPU and additional heat-generating elements may be incorporated in one blade). Each of the heat-exchangers has a main delivery channel 203 for fresh air supply and a main evacuation channel 202. The plurality of main delivery channels 203 coming from each of the blades 210 are fluidically connected through a central delivery pipeline 213 to an air-supply unit 230, for example one or more air blowers. As already mentioned suction device such as vacuum pump may be used to drive the coolant, (alternatively or additionally). Optional air-treatment unit 280 may also be provided. 280 may include pre-cooling system, like filters and drying system. The blower mass-flow-rate is compatible with the overall cooling needs. The air-treatment unit 280 may be used for precooling the supplied air (or any other coolant), and filter it from contaminants. In addition, the blower may be mounted at an external area or may be acoustically shielded in order to reduce the noise level at the server area. The plurality of main evacuation channels 202 coming from each of the blades 210 is fluidically connected to a central evacuation pipeline 212. It is an option to cross the room walls 214 and place the exit 215 of 212 outside in order to exhaust the hot air into the external atmosphere. The main pipe-lines 212 and 213 may thermally be insulated using common thermal isolation shields and materials. Secondary pipe-lines 214 for cooling the central power-supply 250 may also be included. In addition, a central thermal management or control unit 260 may be provided, having input several temperature sensors and I/O signals, i.e. communication with the air-supply units 230 and 280. It may also be connected to the CPUs for integral thermal management inside the CPU itself. The thermal management of the blade-server may incorporate fans 270 for dissipating the remaining heat generated by low-power elements, or supply external cooling air through outlets 275, which may be connected to air supply 230 or to other independent air-supply means.
A second type of heat-sink with respect to another preferred embodiment of the present invention shown in FIGS. 14a-e. Similar to the heat-exchanger device that is based on U-tubes, the overall area of the internal cooling tubes may inflationary be increased when reducing the scales and adding more cooling tubes, and similarly, the rule of scaling down is a Fractal-like rule where the overall volume of the tubes is kept constant. However, the heat exchanger device that is bases on U-tubes is of different topology from the exchanger device described in FIGS. 14a-e in the following manner; While the inlets and the outlets of the U-tubes are positioned on the active surface of the heat-exchanger device and the active surface of the heat-exchanger device is substantially opposite to the HT-surface of the heat-exchanger device, the inlets and the outlets of the cooling tubes of the exchanger device described in FIGS. 14a-e are placed at substantially opposing surfaces and these two surfaces are substantially perpendicular to the HT-surface of the heat-exchanger device described in FIGS. 14a-e.
FIG. 14a illustrates a top view of a heat-exchanger device 140 in accordance with yet another preferred embodiment of the present invention, based on straight cooling tubes to be referred hereafter as I-tubes. Device 140 has short perforated cooling fins 141 mounted on the base 152 of device 140 where in between them an integral fine-delivery channels 144 and fine evacuation channels 146 are created. Manifolds 144 are fluidically connected to the main delivery manifold 142 and manifolds 146 are fluidically connected to the main evacuation manifold 148. The cooling fins 141 are perpendicular to the base 152 and the HT-surface 149 (see FIG. 14b) of the heat-exchanger device 140 and each of the fins 141 includes a large number of cooling tubes 154, i.e. I-tubes passing through the fin. FIG. 14b illustrates a cross sectional view of one cooling fin 141 (see cross section A-A). The heat flux (Q) from the heat-generating element comes from the HT-surface 149 of the fin base 152. The cooling fins 141 comprise a plurality of I-tubes 154. The basic cell 155 of this I-tubes arrangement contains one I-tubes 154 and is made of a heat-conducting material. Without derogating generality, for anticipated CPU cooling tasks typical height (H) of the cooling fins 141 is 4-20 millimeter and the length (L) of I-tubes 154 is a few millimeters. FIG. 14c clarifies the rule of down scaling of the I-tubes 154 of device 140, where arrangement 151a is created by using 3 down scaled basic cells 155 by factor of 2, and the fine arrangement 151b is created by using 4 down scaled basic cells 155 by factor of 2 (arrangements 151a and 151b have same area). This scaling down principle is similar to the scaling down principle outlined hereinabove with respect to FIGS. 3a-d, thus the heat-exchanger device 140 with the perforated fines is similar in most details, in particular with respect to the heat-exchange process, to the heat-exchanger device that was described in FIG. 1 and in more details in FIG. 3 through FIG. 13.
The heat exchanging process (see FIG. 14a) is taking place when the fresh air coming from manifolds 144 penetrates through the I-tubes 154 at a “slalom” course to the manifolds 146, as illustrates by the fine curved arrows. Illustrative three-dimensional view of a portion of the heat-exchanger device is given in FIG. 14d where the base plate 152 with the HT-surface 149 and the cooling fins 141 mounted on the top of surface of 152. In this view, it is clearly seen than the fine delivery channels 144 and fine evacuation channels 146 are created between the cooling fins 141. FIG. 14e illustrates the heat exchanger device 140 mounted over a heat-generating device such as a CPU (162). The CPU 162 is mounted on board 164. A heat-spreader 166 is optionally provided between 140 and 162, where the HT-surface 149 is the contact surface. This cross-sectional illustration shows the cooling fins 141 and the manifolds 144 and 146, where manifolds 144 and 146 are confined and closed as a top cover 168 is provided.
The heat-exchanger device of the present invention is capable of performing high heat removal rates and has inherent local nature as both the fresh air (or other coolant fluid) supply tubes and the hot air evacuation tubes are implemented vertically with respect to the contact surface of the heat-generating element. Based on this principle of vertical tubes arrangement more versions of heat-exchanging device can be created as described on FIGS. 15-26.
FIG. 15 illustrates, in accordance with a preferred embodiment of the present invention, a heat-exchanging device 300 having a plurality of vertical cooling tubes (i.e. U-tubes 390). Heat-exchanging device 300 is a closed unit where the fluid (coolant, such as air) is channeled inside 300. It means that when using vacuum source to drive the flow, the flow can be sucked directly from the surrounding air or when using pressure source to drive the flow, the hot air is directly exhausted to the surrounding. However, in FIG. 15, both the inlet side and the outlet side can be ducted as already mentioned previously. The plurality of U-tubes 300 arranged in a repeated order where each two row are arranged in mirror symmetry. Device 300 may be assembled from two layers; layer 312 and layer 314. Layer 312 has a top-surface 310 aimed at connecting the heat exchanging device 300 to the fine-manifolds unit 400. Layer 314 has an interface contact surface 316 aimed at attaching the heat-exchanging device 300 to the heat-generating element (symbolized in all figures by the letter Q). Each of the U-tubes 390 has a vertical supply tube 320 and a vertical evacuation tube 330, both in layer 312 of device 300. The U-tube 390 has a short horizontal tube 340 (i.e. a connecting tube 340, between 320 and 330), in layer 314 of device 300. In order to operate the heat-exchanging device 300, a fine-manifolds unit 400 is provided on top of surface 310 of device 300 for supplying the fresh air (or other coolant) and for evacuating the hot air. Unit 400 has a plurality of horizontal supply channels 420 and evacuation channels 430 (i.e. substantially orthogonal to the vertical tubes 320 and 330), arranged in an alternating order, each of the channels is fluidically connected to two rows of tubes 320 or 330. Device 300 is in fact a similar embodiment to the previously mentioned embodiments, but it will serve to illustrate additional variants of the heat-exchanger device of the present invention as will be described hereafter.
FIG. 16 illustrates, in accordance with another preferred embodiment of the present invention, a heat-exchanging device 301 that is mostly similar to device 300. Heat-exchanging device is equipped with different vertical U-tubes (element 391), where several U-tubes are engaged (fluidically connected) with respect to horizontal direction “Y” (engagement of 4 U-tubes is illustrated in FIG. 16). Element 391 has elongated supply tubes 321 and elongated evacuation tubes 331. In order to provide high heat-removal rates, Elements 391 has several short horizontal tubes 341 (i.e. a connecting tube 341, between 321 and 331). Four connecting tubes are illustrated in the FIG. 16. However, in order to further improve cooling performance more connecting tubes 341 may be provided in same space. Other details are similar to the description given with respect to FIG. 15.
FIG. 17 illustrates, in accordance with another preferred embodiment of the present invention, a heat-exchanging device 302 that is mostly similar to device 300. Heat-exchanger device 302 is equipped with a plurality of elongated U-tubes 392. Each of the U-tubes 392 has an elongated supply tube 322, an elongated evacuation tube 332, and an elongated connecting tube 342, presenting elongated U-tubes. Heat-exchanging device 302 has reduced internal surfaces for heat-exchange, unless the dimensions of the elongated U-tube 302 are scaled down. Device 302 may beneficially be applied with respect to cost-effectiveness and manufacturing considerations. Other details are similar to the description given with respect to FIG. 15.
FIG. 18 illustrates, in accordance with another preferred embodiment of the present invention, a heat-exchanging device 303 being a version of 301. Heat-exchanger device 303 is equipped with vertical U-tubes construction 393 (element 393), where a row of U-tubes is engaged. Element 393 has elongated supply tubes 323 and elongated evacuation tubes 333, both extend from one side to the other side of device 303. In order to provide high heat-removal rates, element 393 has a plurality of short horizontal tubes 343 (i.e. connecting tubes 343, between 323 and 333). Other details are similar to the description given with respect to FIG. 16.
FIG. 19 illustrates, in accordance with another preferred embodiment of the present invention, a heat-exchanging device 304 that is a modified version of device 303. Heat-exchanging device 304 is equipped with vertical U-tubes construction 394 (element 394), where a row of U-tubes is engaged. Element 394 has elongated supply tubes 324 and elongated evacuation tubes 334, both extend from one side to the other side of device 304. In order to provide high heat-removal rates, element 394 has a plurality of short horizontal tubes 344 (i.e. connecting tubes 344, between 324 and 334). The difference between devices 304 and 303 is that the connecting tubes 344 are provided deep in a wider layer 314 in order to enhance heat removal rates. Other details are similar to the description given with respect to FIG. 18.
Another option is to engage U-tube by creating a long connecting channel in a horizontal direction “X” shown in FIG. 20. (“X” is orthogonal to horizontal direction “Y” shown in FIG. 16). FIG. 20 illustrates, in accordance with a preferred embodiment of the present invention, a heat-exchanging device 500 having a plurality of vertical cooling tubes (i.e. U-tubes 590). Heat-exchanging device 500 is a closed unit where the fluid (i.e. coolant, such as air) is channeled inside 500. It means that when using vacuum source to drive the flow, the flow can be sucked directly from the surrounding air or when using pressure source to drive the flow, the hot air is directly exhausted to the surroundings. The fine-manifolds unit is not shown in FIG. 20 but it may be similar to unit 400 shown in FIG. 15. A plurality of U-tubes 590 is arranged in a repeated order where each two row arranged in mirror symmetry. Device 500 may be assembled from two layers; Layer 512 and layer 514. Layer 512 has a top-surface 510 aimed at connecting the heat-exchanging device 500 to the fine-manifolds unit 400. Layer 514 has an interface contact surface 516 aimed at attaching the heat-exchanging device 500 to the heat-generating element (symbolized the letter Q). Each of the U-tubes 590 has a vertical supply tube 520 and a vertical evacuation tube 530, both in layer 512 of device 500. The U-tubes 590 of each “X” row are connected by engaging channel 540 that is extend from one side to the other side of device 500. Note that the fine-manifold of unit 400 is aligned along Y-direction and the engaging channels 540 of device 500 are aligned along the X-direction, thus crossing each-other. The engaging channels 540 are provided in layer 514 of device 500. Note that channel 540 fluidically connects vertical tubes 520 and 530. It is very important to emphasize with respect to the present invention that although engaging channels 540 are fluidically connected to both supply tubes 520 and evacuation tubes 530 of a X-row of U-tubes 590, the flow itself is subjected to aerodynamic forces that result in local U-shaped flow patterns. It is not necessary to create solid walls in order to direct the flow to change direction such as situated in case of device 300. This is what happened in the case of heat-exchanger device 500 where due to symmetry constrains, the coolant (such as air) is forced to create a “U-flow” pattern as shown in FIG. 20 (see the U-arrows at the lower cross section). In fact, the flow pattern developed inside the heat-exchanger device 500 is substantially similar to the flow pattern developed inside the heat-exchanger device 300 (where the flow is directed through physical tubes).
FIG. 21 illustrates, in accordance with another preferred embodiment of the present invention, a heat-exchanging device 501, which is a modified version of device 500. Here the X-rows of U-tubes 591 are substantially parallel (unlike two rows in mirror symmetry order as implemented in a heat-exchanger device 500). Accordingly the X-row of U-tubes 591 contains alternating vertical tubes, 521 beside 531. Here again the engaging channels 541 are fluidically connected to both supply tubes 521 and evacuation tubes 531 of a X-row of U-tubes 591, and due to symmetry constrains, the coolant (such as air) is forced to create a “U-flow” pattern as shown in FIG. 21. However, when applying alternating arrangement of vertical tubes 591 for the device 501, the flow is compressed, thus the U-flow patterns are doubled with respect to device 500 (see the dense U-arrows at the lower cross section at FIG. 21). Other details are similar to the description given with respect to FIG. 18.
Based on the heat-exchanging device 501, it is an option to provide a modified version of a heat exchanging without vertical supply and evacuation tubes and yet to establish local heat-transfer by a plurality of aerodynamically induced U-flow patterns. It can be done, for example by eliminating layer 512 of device 501 (i.e. to eliminate 521 and 531). Accordingly, a low-cost and compact heat-exchanger device may be assembled from layer 514 (with engaging channels 541) and the fine manifolds unit 400. Such a heat exchanger device will be referred to hereafter as a “crossing channels” heat exchanger device. It is very important to emphasize with respect to the present invention that the crossing channels heat exchanger device is also based on the basic principle of providing high-performance heat-exchange of inherent local nature where both the fresh air supply and the hot air evacuation are implemented vertically (i.e. by situating vertical U-flow patterns inside the heat exchanger device), with respect to the contact plane of the heat-generating element.
FIG. 22 illustrates, in accordance with another preferred embodiment of the present invention, a crossing channels heat-exchanger device 1000 is assembled from two layers (600 and 700). Unit 600 is a solid structure made of thermally conductive material such as Copper or Aluminum. It has a base 610 that faces heat-spreader 820. The heat-spreader 820 is attached to the heat-generating element 820. Unit 600 has a plurality of elongated cooling fins 620 (610 and 620 can be made as a single solid unit), as well as sidewalls 612 and 614. Sidewalls 614 close the plurality of elongated cooling channels 622 that are defined between the parallel fins (620).
Unit 700 has a plurality of crossing supply channels 720 (with respect to cooling channels 622 of unit 600) having an entrance 722 created in side walls 712 of unit 700, for providing the fresh air (air can be supply from both directions—in order to reduce pressure losses and to enhance cooling uniformity, see FIG. 23), and a plurality of crossing evacuation channels 730. In the case presented here, the hot air is directly exhausted upwards through elongated outlet located at the top cover 710 of unit 700. Unit 700 has a plurality of dividing walls 740 (.i.e. between 720 and 730) and side walls 714 parallel to 740. Unit 700 can be made of thermally conductive material such as Copper or Aluminum, but it can be made of non-metallic, less conductive and even thermally isolating material in cases where the required heat removal rates are solely obtained by unit 600 of device 1000.
FIG. 23a illustrates the local U-flow patterns that are created inside the crossing channels heat-exchanger device 1000 presented in FIG. 22. The fresh air at the crossing supply channels 720 of unit 700, kept at a higher pressure, can pass only though the cooling channels 622 created between each two cooling fins 620 of unit 600, to the crossing evacuation channels 730 of unit 700, and then the hot air is directly exhausted upwards through the elongated opening created at top cover 710 of unit 700. As a result of the crossing channels configuration many (and substantially miniature) U-flow patterns of local nature are created. In-fact, if N cooling channels are created in unit 600 and M crossing channels are created in unit 700, than as much as M×N miniature U-flow patterns are created across the entire area of device 1000.
FIG. 23b illustrates additional aspects of the flow inside the crossing channels heat-exchanger device 1000. In this example, fresh air is supplied from both sides (721a and 721b) of device 1000 through 722 (see FIG. 22). The air is flowing horizontally along the crossing supply channel 720 of unit 700 in relatively low-velocity thus pressure is substantially uniform. Wall 725 may by used to separate the two opposing flow directions although it may by achieved naturally as by symmetry it is a stagnation line. As the passage towards the crossing evacuation channel 730 of unit 700 (hidden by the dividing wall 740), is through the cooling channels 622 of unit 600 (i.e. fine passages), the flow is accelerated downwards and passes in 622 at much higher speed, then the flow turns upwards towards the crossing evacuation channel 730 of unit 700 and the hot air is released to the surrounding space (as denoted by dashed arrows). In order to optimize pressure drop, in this configuration the crossing supply channels 720 may be wider than the crossing evacuation channels 730.
FIG. 24 illustrates, in accordance with another preferred embodiment of the present invention, additional views of a crossing channels heat-exchanger device 1000 assembled from two units (600 and 700). Unit 600 is the heat-exchanging layer having a base 610 and a plurality of elongated cooling fins 620 as well as sidewalls 612 and 614. Sidewalls 614 close the plurality of elongated cooling channels 622 created between each two parallel fins 620. Typically, with respect to the heat removal requirements relating to some commercially available heat-dissipating electronic components, the cooling-channels (622) width can be 1 mm to 0.1 mm and the fins 620 thickness may be similar or half of it. Accordingly, in each cm, typically, as much as 5 to 50 parallel cooling-channels can be created in unit 600. The height of the cooling fins 620 (and accordingly the height of cooling channels 622) can typically be varied from few millimeters to a tenth of a millimeter.
Unit 700 is a manifold having a plurality of crossing supply channels 720 having an entrance 722 created in both sidewalls 712 of unit 700, for providing fresh air from both directions, and a plurality of crossing evacuation channels 730. The hot air is directly exhausted upwards through elongated outlet located at the top cover 710 of unit 700. Unit 700 has a plurality of dividing walls 740 (.i.e. between 720 and 730) and side walls 714 (parallel to 740). The supply 720 and evacuation 730 crossing channels are significantly wider and higher than the cooling-channels 622 of unit 600, in order to reduce pressure losses and to enhance cooling uniformity. Unit 600 may be made of thermally-conducting materials in order to enhance overall heat transfer but it can made also from non-metallic and even insulating materials as most of the heat absorption takes place at unit 600.
FIGS. 25a-c illustrates, in accordance with preferred embodiments of the present invention, several implementations of the crossing channels heat-exchanger device for cooling heat-generating element (for example a CPU). In FIG. 25a, the heat-generating element 810 is equipped with a heat-spreader 820. The crossing channels heat-exchanger device (i.e. unit 600a with the cooling fins and unit 700 with the crossing supply and evacuation channels) is assembled on top of 820 as a standard stand-alone heat-exchanger device configuration 900a. In this case typical height of the fin would be of a few mm.
In FIG. 25b, the heat-generating element 810 is equipped with a heat-spreader 820 where the cooling channels (600b) are created as an integral layer on the contact surface of 820. Accordingly, part of the crossing channels heat-exchanger device (i.e. the cooling channels layer 600b) is applied on top of 820 and the complementary part (700) is provided as a stand-alone unit to complete the crossing channels heat-exchanger device configuration 900b. In this case typical height of the fin would be less than one mm.
In FIG. 25c, the heat-generating element 810 is provided with fine cooling channels (600c), created as an integral layer on the top surface of the heat-generating element 810. Accordingly, part of the crossing channels heat-exchanger device (i.e. the cooling channels layer 600c) is applied on top of 810 and the complementary part (700) is provided as a stand-alone unit to complete the crossing channels heat-exchanger device configuration 900c. In this case typical height of the fin would be less than 0.2 mm. It is possible to apply MEMS techniques to built the fine cooling fins layer above 810).
The heat-exchanger device of the present invention may exchange heat with a solid objects, but also with gases or liquids.
The cooling or heating fluid may be supplied from a low-pressure source (typically of less than 2 mbar), a moderate pressure source (typically of less than 200 mbar) or a high-pressure source (typically more than 200 mbar and also more than 5 bars). Both gases and liquid may be used as coolants and as much as the thermal capacity of the coolant is larger, the potential of cooling is larger
Generally speaking, the greater the supply pressure, the greater the potential of cooling or heat exchanging. The greater the density of the coolant, the greater the potential of cooling.
Generally speaking, as much as the mass-flow rate of the coolant is larger, the potential of cooling is larger. The cooler the coolant is with respect to the temperature of the heat-generating element (ΔT), the greater the potential of cooling.
Generally speaking, the greater the overall surface of the heat-exchanger internal cooling tubes, the greater the potential of cooling. Generally speaking, the greater the thermal-conductivity of the heat-exchanger structural material is, the greater the potential of cooling. Examples of good heat-conducting materials are Aluminum or Copper, as well as non-metallic materials having high thermal conductivity.
It has to be emphasized that several of the parameters mentioned herein are dependent parameters.
The object to be cooled may be flat or curved, and correspondingly, the shape of the heat exchanger's facing surface (the HT-surface) would be of the same shape, so as to fit it properly and allow heat-flux without thermal resistance. In some preferred embodiments of the present invention, the heat-exchanger can be of a uniform width. In other embodiments it may have a non-uniform width.
The heat exchanger of the present invention may be designed as a compact unit having same dimensions as the heat-generating element, or much different dimensions: either larger or smaller than the heat-generating element (naturally, a larger heat-exchanger is preferable).
In a preferred embodiment of the present invention the heat-exchanger device may be designed as a thin rectangular unit having relatively small width with respect to its lateral dimensions. This appears to be suitable for compact cooling conventional electronic chips.
Note that throughout this specification the terms “heat exchanging device” and “heat exchanging layer” and heat sink are alternatively used. Sometimes, when “heat exchanging device” is used it also includes the manifold—depending on the context.
It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope.
It should also be clear that a person skilled in the art, after reading the present specification could make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the present invention.
