Patent Application
20130160477
The present disclosure relates to an ice generator capable of making ice slurry by absorbing heat energy when a refrigerant is evaporated. To be specific, the present disclosure relates to an ice slurry generator with increased efficiency and productivity by modifying the structure for heat exchange between a refrigerant and a carrier fluid.
Generally, ice slurry has excellent heat storage, fluidity, ability as a refrigerant, and heat release compared to a conventional refrigerant. Therefore, the ice slurry is expected to take on a greater role in heat storage and cold heat transportation and to be recognized as a core technology for a next-generation heating and cooling system. However, the market demand for ice slurry-based cooling systems has been stagnant for many years. Many scholars and researchers have claimed that the reason for such stagnation is the lack of an economical and reliable ice generator that is scalable and easily maintainable. Accordingly, the first priority in the expansion of the role of the ice slurry is to obtain an economical and reliable ice slurry generator.
Such an ice generator can be attained through a different version of the common shell and tube heat exchanger-type ice generator. The efficacy of the shell and tube model has been partially proven with the vertical shell and tube heat exchanger. However, the maximum capacity of all vertical shell and tube type products developed so far has not been scaled up above approximately 500 kW/unit (based on ice generation capacity). Furthermore, in all models so far, ice particles cannot be present at the outset of the ice generator cycle, as this results in inoperability due to clogging. Thus, it is difficult to apply the ice generator to a direct transportation system. For domestic products, as the size of an ice generator is increased, the power consumption of the circulation pump is disproportionately increased during ice slurry production.
In accordance with a whip rod heat exchanger described in U.S. Pat. No. 5,768,894, a carrier fluid is uniformly introduced into the top of the vertical heat exchanger tubes. Then, a whip rod inside each heat transfer tube is rotated at high speed with an orbital motion. The orbital motion generates a centrifugal force that causes the whip rod to rotate in contact with the inner surface of the heat transfer tube. Thus, the ice layer is scraped from the inner surface and flows down to be collected at a lower area of the heat transfer tube due to gravity. A slurry pump sucks the collected ice slurry and discharges the ice slurry to the bottom discharge chamber. However, the flow velocity of the carrier fluid at the inlet chamber is greatly decreased in order to uniformly distribute the carrier fluid. Therefore, if even a small amount of ice particles is externally introduced into the apparatus, the ice particles continue to pile up at an upper area of the inlet chamber and the inlet chamber becomes clogged. Even if an additive to increase fluidity is used, this problem cannot be avoided. If the ice generator is connected to a heat storage tank in order to apply it to a direct transportation system, a high concentration of ice particles is unavoidably introduced into the inlet chamber. Thus, the inlet chamber is often clogged and operation becomes very difficult. For this reason, this apparatus cannot be applied to the direct transportation system and thus has been used for a cooling-only ice storage system that uses an ice-bed type heat storage tank. The discharge section of the ice slurry generator is frequently clogged as well. Furthermore, it is difficult to manufacture this apparatus on a large scale as the drive plate, which is a main component for power transfer, cannot be scaled up due to the limitation of its mechanical strength. Therefore, this apparatus is not suitable for a large scale heat source system such as a district cooling system. Furthermore, abrasion of the driving components is quite common, and the cost of maintenance is greatly increased as a result. Korean Patent No. 10-0513219 describes efficiency in discharging ice slurry to the outside of an ice generator as a requisite feature of an ice generator. To be specific, in an ice generator, guide plates slanted toward the outlet are provided in a counter-flow discharge chamber. However, despite the presence of the guide plates, additional pumping head ranging from about 0.2 bar to about 0.8 bar (depending on a size of the ice generator) is needed in order to discharge the ice slurry from the ice generator. The necessary additional pumping head is proportional to the capacity of the ice generator. Compared to the basic pumping head for uniform distribution, power consumption is greatly increased by the additional pumping head. If ice slurry containing a high concentration of ice particles is introduced into the ice generator, the ice particles and the water separate at the inlet, and the ice generator may become partially clogged. Therefore, ice generator components with better discharge and clogging prevention capabilities are necessary.
Meanwhile, ice generators of the single tube scraper-type, the disc-type, the vacuum-type, and the fluidized bed-type have been developed in Europe and North America. However, these apparatuses are not priced competitively, are not suitable for a thermal storage system due to their small capacity, and are used only for a specific purpose due to high cost. Although the single tube scraper-type apparatus of a small capacity has high reliability and excellent circulation capability, it is limited in usage to cooling marine products, due to limited capacity and lack of competitive prices. In addition, it is very difficult to return the ice slurry from vacuum to atmospheric pressure; because of this, the vacuum-type apparatus cannot be commercialized.
In a fluidized bed-type apparatus, it is difficult to separate the ice particles from the metal or plastic balls that are used in a fluidized bed. Accordingly, the height of the apparatus must be greatly increased, resulting in difficulty in transporting the separated ice particles. Another type of apparatus has been developed that makes the ice slurry on a smooth, lab-scale evaporation plate in order to prevent ice particles from becoming stuck to the plate. However, a long term operation is not viable due to issues of surface contamination. Moreover, actual competitiveness is still questionable due to the complicated conditions required for operation.
The multilayer disc and brush-type ice generating method recently developed in Canada allows for a capacity of about 500 kW/unit. However, there is not yet a way to efficiently collect the generated ice slurry from this method.
A super-cooled water-type ice generating method has been developed primarily in Japan. The great technical advances in this method have been commercialized widely in an ice storage system. However, for direct transportation applications, the efficacy of the system is limited by clogging (caused by phase separation) and agglomeration (caused by re-crystallization and the bridging phenomenon). Furthermore, in order to continuously generate super-cooled water, the ice generator needs a highly efficient filter for removing fine impurities/particulates from the water, a preheating device to prevent the unwanted introduction of ice particles, and an indirect cooling evaporator (it is impossible to directly exchange heat with a refrigerant). Therefore, the operation becomes overcomplicated. Accordingly, despite its technical superiority, usage of the super-cooled water-type ice generator is not expanding.
Recently, there has been one more trial to develop an improved scraper-type ice generating method. An attempt was been made in the U.S., in which the outer surface of the whip rod was coated with a plastic to prevent abrasion of the whip rod. However, the heat transfer tube had a problematic driving system, issues in circulation due to a larger whip rod that blocked the ice particles from flowing downward, and stagnation of the ice slurry in the inlet of the distribution chamber.
In conclusion, ice generators have high potential for effective use in heat pump systems, but in order for them to be widely used, they need to be economically feasible, scalable and free of clogging problems incurred during circulation.
In accordance with an illustrative embodiment of the present disclosure, there is provided a scalable ice generator with improved efficiency and productivity due to modifications in the structure of the heat exchange between a refrigerant and a carrier fluid.
In accordance with an illustrative embodiment of the present disclosure, there is provided an ice generator that prevents an overload of components by minimizing clogging and agglomeration of the ice slurry within the apparatus and enables efficient circulation of the ice slurry.
In accordance with an embodiment of the present disclosure, there is provided an ice generator that includes: a heat exchanger configured to absorb heat energy while a refrigerant is evaporated; multiple horizontal heat exchange passages provided within the heat exchanger and configured for heat exchange between a carrier fluid and the refrigerant; inlet and discharge chambers that are connected to the heat exchange passages; screw-like scrapers within the heat exchange passages that transport the carrier fluid from the inlet chamber to the discharge chamber via rotation; and a driving unit that rotates the scrapers.
In accordance with one aspect of the present disclosure, at least one scraper should be extended from the heat exchange passages into either the inlet chamber or the discharge chamber.
In accordance with one aspect of the present disclosure, the ice generator also includes stirring units with radial paddles that are installed in both the discharge and inlet chambers. They prevent clogging caused by phase separation of the carrier fluid during rotation.
In accordance with one aspect of the present disclosure, the gap between the edge of the scraper blade and the inner surfaces of the heat exchange passages should be between 0.1 mm to 0.4 mm.
In accordance with one aspect of the present disclosure, one face of a scraper blade is flat, while the other face is convex.
In accordance with one aspect of the present disclosure, the ice generator includes supporting members for the heat exchange passages, and the supporting members are made of plastic.
In accordance with one aspect of the present disclosure, the discharge chamber includes a discharge opening to expel the carrier fluid to the outside; flat guide plates inclined within the heat exchange passages guide the carrier fluid toward the discharge opening.
In accordance with one aspect of the present disclosure, a scraper may penetrate the guide plates.
In accordance with one aspect of the present disclosure, the inlet chamber may include one or more inlet openings. If there are multiple inlet openings, they are arranged symmetrically in a radial direction with respect to the inlet chamber.
The effect of the Invention can be described as follows. Firstly, the scrapers are extended into the inlet chamber or the discharge chamber so as to smoothly stir the carrier fluid; such extensions make it possible to prevent clogging or agglomeration caused by phase separation of the solid-liquid carrier fluid.
Secondly, the extension of scrapers into the inlet chamber can prevent stagnation caused by a difference in the flow velocity of the carrier fluid and/or a difference in the distance from the inlet opening to each heat exchange passage.
Thirdly, it is possible to efficiently remove any solidified medium from the inner surface of the heat exchange passage, despite the relatively slow rotation of the scrapers, by maintaining a gap between the scraper and the inner surface of the heat exchange passage. This makes it possible to perform a continuous operation.
Fourthly, a scraper maintains its precisely fitted position within its respective heat exchange passage regardless of whether the ice generator is on or off. This prevents abrasion of the inner sides of the heat exchange passage. Because the scraper does not shift from its position at the center of the heat exchange passage, the heat exchange passage can be positioned at any angle regardless of gravitational direction.
Fifthly, the ice generator is aligned horizontally, so that the refrigerant outside of the heat exchange passages can be maintained in a nucleate boiling condition. Thus, it is possible to increase the efficiency of heat transfer. Moreover, a horizontal driving unit is more accessible to maintenance workers than vertical types. Further, a horizontal heat exchange passage can be made to be longer than a vertical type can be made tall, so that it is more feasible to scale the generator up, although the scale is also dependant on the strength of the driving unit.
Sixthly, the stirring units that guide the carrier fluid toward the discharge opening aid the overall prevention of clogging or agglomeration.
Seventhly, because the scraper does not shift from the center of the inside of the heat exchange passage during operation, rotational vibration of the scraper can be minimized. Even if excessive power is applied to the scraper, as it is when the generator senses potential clogging in the heat exchange passage, the heat exchange passage is supported by an external member(s) that suppresses rotational vibration. This is possible because the external member(s) is/are made of flexible plastic material that absorbs high frequency vibration, so that the transfer of the vibration to other components is minimized.
Hereinafter, illustrative embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, it is to be noted that the present disclosure is not limited to the illustrative embodiments.
An ice generator in accordance with an illustrative embodiment of the present disclosure will be explained with reference to
As depicted in the drawings, the ice generator includes a heat exchanger 100, heat exchange passages 110, an inlet chamber 120, a discharge chamber 130, scrapers 200, and a driving unit 170.
The heat exchanger 100 is primarily used to absorb heat energy from the ice slurry while the refrigerant is evaporated within the inner space of the heat exchanger 100.
The heat exchange passage 110 is aligned horizontally within the heat exchanger 100, and the carrier fluid interacts with the refrigerant while passing through the heat exchange passages 110. There are multiple heat exchange passages 110 shaped like hollow pipes. Preferably, the heat exchange passages should be made of a surface processed copper tube that is ideal for accelerating nucleate boiling, but other materials could be used.
The inlet chamber 120 is connected to the heat exchange passage 110 on one side of the heat exchanger 100, so as to introduce the carrier fluid into the heat exchange passage 110. The discharge chamber 130 is connected to the heat exchange passage 110 and is provided on the opposite side of the inlet chamber 120 on the heat exchanger 100. The carrier fluid exits through to the discharge chamber 130 from the heat exchange passage 110.
The inlet chamber 120 includes an inlet opening 125; the carrier fluid is introduced into the inlet chamber through the inlet opening 125. The discharge chamber 130 includes a discharge opening 135 for discharging the carrier fluid, by which heat is completely exchanged with the outside via the ice slurry. Details will be described with reference to
The scraper 200 in
The blade 220 wraps in a screw-like fashion around the outside of the rod member 210. Relative to the direction of rotation of the scraper 200, the front face of the blade 220 forms a convex surface and the back face forms a flat surface.
The scraper 200 is inserted into the heat exchange passage 110. As the scraper 200 is rotated, the carrier fluid introduced from the inlet chamber 120 into the heat exchange passage 110 is transported toward the discharge chamber 130 inside the heat exchange passage 110 by the spiraled blade 220. The carrier fluid is transported while in contact with the heat exchange passage 110, so that heat exchange is performed. In other words, the scraper 200 both transport the carrier fluid toward the discharge chamber 130 and removes any solidified medium on the inner surface of the heat exchange passage 110, thus increasing the efficiency of heat transfer.
The driving unit 170 is connected to, but not limited to, a commonly used motor; a gear is connected to the motor to provide a rotational driving force to the scraper 200. Any motor can be used if it can output the power required to operate the ice generator and provide a driving force capable of rotating the scraper 200.
Since one or more of the scrapers 200 extend into the inlet chamber 120 or the discharge chamber 130, the scraper 200 can prevent clogging or agglomeration caused by phase separation of the carrier fluid.
Thus, the scraper 200 enables the carrier fluid to smoothly flow through the inlet chamber 120 or the discharge chamber 130.
In the ice generator configured as described above, when the carrier fluid is introduced into the inlet chamber 120 of the ice generator, the flow velocity of the carrier fluid is decreased due to an increased cross sectional area.
Previously, the carrier fluid may have become stagnant because the flow velocity was different at each part of the carrier fluid, and/or because the distance between the inlet opening 125 and each heat exchange passage 110 was not uniform, but the scrapers 200 prevent such stagnation because they are extended into the inlet chamber 120.
The width of the blade 220 should be determined so as to maintain a gap between the edge of the blade 220 of the scraper 200 and the inner surface of the heat exchange passage 110 within a range of 0.1 mm to 0.40 mm.
The driving unit 170 is operated so as to rotate the scraper 200 at speeds between 200 rpm and 450 rpm.
The sharp edge of the blade 220 can further reduce any potential dry-out points on the inner surface of the heat exchange passage 110 during rotation. Preferably, the edges of the blades 220 of the scrapers 200 for each respective heat exchange passage 110 should have a thickness of, but not limited to, approximately 0.1 mm.
When the ice generator is operating, the carrier fluid forms a thin liquid film that is continuously formed and destroyed by the contact between the edge of the blade 220 and the inner walls of the heat exchange passages. This film acts as a lubricant for the blades, and speeds up the entire heat transfer process.
The convex shape of the front face of the blade 220 (“front” with respect to the direction of the movement of the carrier fluid during operation) compresses the carrier fluid while the flat back face, in comparison with the convex front face, decompresses the carrier fluid. This creates a partial vortex, which relieves supercooling and accelerates the phase separation of the carrier fluid. Thus, the level of supercooling of the carrier fluid can be controlled in order to generate soft ice slurry.
The ice generator may become overloaded if the gap between a blade 220 and the respective heat exchange passage 110 is increased. This is because the widened gap causes the level of supercooling to increase as well; as a result hardened ice may form on the inner surface of heat exchange passages, and the scraper 200 may be unable (due to the overload of the carrier fluid) to remove the hardened ice. Thus it is necessary that the gap remains at the same width at all times in order to ensure uninterrupted operation.
Furthermore, in order to prevent agglomeration or clogging within discharge chamber caused by interaction between discharged carrier fluid from adjacent heat exchange passages 110, the scraper 200 in a given heat exchange passage 110 should be rotated in the opposite direction to a scraper 200 in an adjacent heat exchange passage 110.
For configuration described above, the power consumption for the ice generator, in accordance with the illustrative embodiment, is minimized because the overloading typical of a conventional ice generator does not occur and thus efficiency of heat transfer is increased. This result is shown in
By looking at the variations in power consumption, it can be deduced that initial overloading of the ice generator that is in accordance with the illustrative embodiment is relatively low compared to the conventional ice generator.
When the blade 220 is maintained in the correct shape and position, any deviation between the stop position of the scraper 200 and an operation position can be reduced. And because any deviation is minimized, the heat exchange passages 110 and thus the entire ice generator can be positioned horizontally so as to be perpendicular with the direction of gravity.
Therefore, the ice generator in accordance with the illustrative embodiment of the present disclosure can be aligned to be horizontal. In other words, the carrier fluid is transported from the inlet chamber 120 to the discharge chamber 130 as the scraper 200 is rotated, and, thus, the heat exchange passage 110 is aligned to be in parallel with the direction of the surface of the earth. The discharge chamber 130, the inlet chamber 120, and the driving unit 170 are provided at a side surface of the heat exchanger 100, so that a large quantity of the carrier fluid can flow through and the influence of gravity can be minimized.
Since the ice generator is aligned horizontally, the refrigerant outside the heat exchange passage 110 can be maintained in a nucleate boiling condition. This can increase the efficiency of heat transfer. Furthermore, since the driving unit 170 is also positioned horizontally, it is easily accessible for maintenance work, compared to a case where the driving unit 170 is positioned vertically. Furthermore, the horizontal heat exchange passage 110 can be made longer than the vertical type can be made taller, so that the ice generator is more scalable.
Although it has been described that the scrapers 200 of the ice generator in accordance with the illustrative embodiment are extended to either the discharge chamber 130 or the inlet chamber 120 so as to stir the carrier fluid, the present disclosure is not limited thereto. For more detailed explanation thereof,
As depicted in the drawings, the ice generator further includes a stirring unit 400.
The stirring unit 400 is provided in the discharge chamber 130 and includes radial paddles. The stirring unit 400 is formed in a shape substantially similar to, but not limited to, a propeller.
The stirring unit 400 stirs the carrier fluid discharged from the heat exchange passage 110 so as to suppress clogging caused by the phase separation of the carrier fluid.
The carrier fluid discharged from the heat exchange passage 110 is prone to causes agglomeration or clogging within the heat exchange passage 110 in the form of ice slurry, but the stirring unit 400 works to circulate and guide the carrier fluid toward the discharge opening 135. Thus, it is possible to suppress clogging or agglomeration.
The ice generator in accordance with a second illustrative embodiment of the present disclosure will be explained with reference to
As depicted in the drawings, the ice generator includes the heat exchanger 100, the heat exchange passage 110, the inlet chamber 120, the discharge chamber 130, the scraper 200, the driving unit 170, a supporting member 115, and a guide plate 300. For the sake of convenient explanation, explanations of similar or same components as illustrated with reference to
The flat guide plate 300 is provided in the discharge chamber 130. The guide plate 300 is inclined toward a certain direction at a predetermined angle with respect to the heat exchange passage 110 so as to best guide the carrier fluid toward the discharge opening 135.
The parts of the scrapers 200 that extend to the discharge chamber 130 penetrate the guide plate 300. The guide plate 300 configured as described above separates the carrier fluid remaining outside the scraper 200, i.e. the carrier fluid transformed into ice slurry and congealing on the surface of the scraper 200, from the scraper 200 and guides the separated carrier fluid toward the discharge opening 135.
The carrier fluid becomes increasingly laden with ice particles as it passes through the heat exchange passage 110 toward the discharge chamber 130. Because of the increasing level of ice particles, the circulation of the carrier fluid is relatively slow. Yet the carrier fluid still flows smoothly because of the flow path provided by the guide plate 300 and the extension of the scraper 200 into either the discharge chamber 130 or the inlet chamber 120.
If the capacity of the ice generator is increased, the number of the heat exchange passages 110 may be increased to about 200 or more. The heat exchange passages 110 may be divided into several groups and a passage space may be formed between the groups to allow for the smooth flow of the carrier fluid.
The discharge opening 135 is in the upper portion of the discharge chamber 130, so that the carrier fluid can be easily discharged through the discharge opening 135 by means of buoyancy.
Multiple inlet openings 125 may be formed in the inlet chamber 120. Similarly, multiple discharge openings 135 can be formed.
In this case, the inlet openings 125 are arranged symmetrically in a radial direction in the inlet chamber 120 in order to better control the flow of the carrier fluid when introduced into the inlet chamber 120. Accordingly, by optimizing the arrangement of the inlet openings 125, it is possible to minimize variations in flow velocity caused by the varied positions of the heat exchange passages 110 within the inlet chamber 120.
The carrier fluid is directly introduced into the inlet chamber 120 without passing through a separate distribution device, and becomes homogeneous as a result of the stirring action of the scraper 200 within the inlet chamber 120.
A bypass tube 119, separate from the heat exchange passages 110, may be further provided to connect the discharge chamber 130 to the inlet chamber 120.
The bypass tube 119 is used to move the carrier fluid in the inlet chamber 120 to the discharge chamber 130 when the amount of the carrier fluid introduced into the inlet chamber 120 is increased too quickly or if the carrier fluid does not flow smoothly in some of the heat exchange passages 110. If necessary, the bypass tube 119 may include a valve (not illustrated) for opening.
The supporting member 115 supports the heat exchange passages 110. Multiple members 115 may be arranged at intervals of 500-900 mm depending on a length of the heat exchange passages 110 so as to prevent the heat exchange passage 110 from drooping, as well as to suppress vibration of the heat exchange passages 110 during operation of the ice generator.
Preferably, the supporting members 115 are positioned in contact with the heat exchange passages 110 in order to prevent damage or decoupling of vibration between the heat exchange passage and other components. The supporting member 115 is made of plastic in order to protect the heat exchange passage 110.
In the ice generator that is in accordance with the illustrative embodiment, there is a small gap between the edge of the blade 220 of the scraper 200 and the inner surface of the heat exchange passage 110. Moreover, the blade 220 has the curved front surface described previously. Thus, when the scraper 200 is rotated, the scraper 200 pushes the carrier fluid out toward the inner surface of the heat exchange passage 110. This prevents the scraper from shifting from the center of the heat exchange passage during operation. As a result, the rotational vibration of the scraper is minimized.
Even if excessive power is applied to the scraper 200 due to the ice generator's detection of potential clogging within a heat exchange passage 110, the heat exchange passage 110 is supported by an external member that suppresses rotational vibration caused by the scraper 200. The external member is made of a flexible plastic material that absorbs high frequency vibration.
Although the present disclosure has been explained with reference to the illustrative embodiments described above and the accompanying drawings, the present disclosure is not limited thereto and can be modified and changed in various ways by those with sufficient expertise in this field.
Therefore, the scope of the present disclosure is defined by the following claims and their equivalents rather than by the detailed description of the illustrative embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2010-0094233 | Sep 2010 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR11/07103 | 9/27/2011 | WO | 00 | 3/4/2013 |
