WO2007046566A1

WO2007046566A1 - Ice making unit of thermal storage medium and thermal storage system equipped thereof

Info

Publication number: WO2007046566A1
Application number: PCT/KR2005/003516
Authority: WO
Inventors: Seong-Eun Cho
Original assignee: T1 Engineering Co., Ltd.
Priority date: 2005-10-21
Filing date: 2005-10-21
Publication date: 2007-04-26

Abstract

A heat storage system is provided with a thermal storage medium freezing unit that includes an air compressor for compressing an air sucked from a heat storage reservoir and a spray nozzle for spraying the air compressed by the air compressor into the heat storage reservoir together with a thermal storage medium. The thermal storage medium is granulated by the compressed air and frozen as the air is sprayed from the spray nozzle and expanded. This improves the efficiency of the heat storage system and simplifies the structure of the heat storage system, thus helping to miniaturize the heat storage system.

Description

ICE MAKING UNIT OF THERMAL STORAGE MEDIUM AND THERMAL STORAGE SYSTEM EQUIPPED THEREOF

Technical Field

[1] The present invention pertains to a heat storage system that stores thermal energy through the use of nighttime electricity and performs a daytime air conditioning task with the thermal energy thus stored. Background Art

[2] In general, a heat storage system is designed to store thermal energy in the nighttime by virtue of a refrigerating cycle composed of a compressor, a condenser, an expansion valve and an evaporator and to conduct an air conditioning task during the daytime with the use of the thermal energy stored at night. The heat storage system stores the thermal energy in a manner by which a thermal storage medium is caused to make heat exchange with the evaporator and then to be phase-transformed into a lump of ice.

[3] According to such a heat storage system, the thermal storage medium of liquid phase is phase-transformed into the ice lump of solid phase while passing through and heat exchanging with the evaporator. The ice lump is then crushed into small-sized ice grains by a pulverizer with which the heat storage system is equipped. The thermal storage medium of small-sized ice grain condition is transferred to a heat storage reservoir and admixed with a liquid phase thermal storage medium into ice slurry. The thermal storage medium of this condition is caused to, in the daytime, heat exchange with load-side circulating water of elevated temperature such that it can be used for air conditioning and cooling.

[4] In the typical heat storage system as described above, the thermal storage medium makes a direct contact with the evaporator and is transformed into the ice phase, in which process ice is stuck to the surface of the evaporator. Thus a need exists for a regenerating process whereby the ice stuck to the surface of the evaporator is melted down. Also, a process is required for crushing the thermal storage medium, which has been solidified into the ice lump, into the small-sized ice grains.

[5] These regenerating and crushing processes entails an energy loss which may lead to reduced efficiency of the heat storage system. In addition, the crushing process requires use of a separate pulverizer, which is disadvantageous in miniaturization of the heat storage system. Disclosure of Invention Technical Problem [6] Taking into account the afore-mentioned problems inherent in the prior art, it is an object of the present invention to provide a thermal storage medium freezing unit and a heat storage system incorporating the freezing unit that exhibit an enhanced efficiency.

[7] Another object of the present invention is to provide a thermal storage medium freezing unit and a heat storage system incorporating the freezing unit that have a simplified structure and are advantageous in miniaturization.

[8]

Technical Solution

[9] With these objects in mind, one aspect of the present invention is directed to a thermal storage medium freezing unit for use in a heat storage system, comprising: an air compressor for sucking and compressing an air from a heat storage reservoir in which a thermal storage medium is stored; and a spray nozzle for spraying the air compressed by the air compressor into the heat storage reservoir together with the thermal storage medium to freeze the thermal storage medium.

[10] The thermal storage medium collides with and is granulated by the compressed air as the thermal storage medium and the compressed air are introduced through the spray nozzle, and the granulated thermal storage medium is frozen by the air sprayed from the spray nozzle and expanded.

[11] The thermal storage medium freezing unit further comprises: an air pressure tank for cooling the air compressed by the air compressor, the air pressure tank enclosing therein an evaporator of a refrigerator unit; an air pressure control valve provided between the air pressure tank and the spray nozzle for allowing the air in the air pressure tank to flow toward the spray nozzle if the pressure in the air pressure tank is equal to or greater than a predetermined value; and a moisture separator for separating moisture from the air sucked up by the air compressor.

[12] The spray nozzle is provided with a throttling part whose flow path section area is reduced such that the air can be expanded as it is introduced through the spray nozzle. The air pressure tank is provided with a drain line for exhausting condensed water therethrough.

[13] Another aspect of the present invention is directed to a heat storage system, comprising: a refrigerator unit provided with first and second evaporators; a heat storage reservoir in which a thermal storage medium is stored; a thermal storage medium cooling unit for cooling the thermal storage medium by causing the thermal storage medium stored in the heat storage reservoir to heat exchange with the first evaporator; and a thermal storage medium freezing unit for bringing the air in the heat storage reservoir into heat exchanging with the second evaporator, wherein the thermal storage medium freezing unit comprises: an air compressor for sucking and compressing the air in the heat storage reservoir; and a spray nozzle for spraying the air compressed by the air compressor into the heat storage reservoir together with the thermal storage medium to freeze the thermal storage medium.

[14] The thermal storage medium cooling unit comprises: a thermal storage medium circulating pump for circulating the thermal storage medium stored in the heat storage reservoir; a first heat exchanger for causing the thermal storage medium to heat exchange with a load as the thermal storage medium is circulated by the thermal storage medium circulating pump; a second heat exchanger for causing the thermal storage medium to heat exchange with the first evaporator as the thermal storage medium is circulated by the thermal storage medium circulating pump; a reservoir inlet pipe in fluid communication with the heat storage reservoir for returning the thermal storage medium to the heat storage reservoir after passing through the second heat exchanger; and a nozzle inlet pipe connected to the reservoir inlet pipe for feeding the thermal storage medium to the spray nozzle.

[15] A three-way control valve is disposed at a position where the reservoir inlet pipe meets with the nozzle inlet pipe.

[16]

Advantageous Effects

[17] According to the present invention, a thermal storage medium is granulated and frozen into small-sized ice grains through the use of an air sprayed by a spray nozzle, thus making it possible to eliminate the ice crushing process which has been required in the prior art.

[18] Furthermore, first and second evaporators make no direct contact with a thermal storage medium in a freezing process, which ensures that no ice is stuck to the first and second evaporators. This makes it possible to eliminate the process of regenerating the first and second evaporators.

[19] Eliminating the ice crushing process and the evaporator regenerating process in this manner helps improve efficiency of the heat storage system.

[20] Moreover, the size of the ice grains sprayed into a heat storage reservoir can be changed by regulating the pressure of an air introduced through a spray nozzle. This helps optimize fluidity of the thermal storage medium, which is of ice slurry condition, thus further improving efficiency of the heat storage system.

[21] In addition to the above, the elimination of an ice crushing unit and the simplification of a thermal storage medium freezing unit offer an advantage in miniaturizing a heat storage system. This reduces constraints in selecting an installation place of the heat storage system. Brief Description of the Drawings [22] FIG. 1 is a schematic diagram showing a heat storage system in accordance with one embodiment of the present invention;

[23] FIG. 2 is a section view showing a spray nozzle employed in the heat storage system shown in FIG. 1 ;

[24] FIG. 3 is a schematic diagram illustrating a process of heat-storage cooling operations in the heat storage system shown in FIG. 1 ;

[25] FIG. 4 is a schematic diagram illustrating a process of heat-storage freezing operations in the heat storage system shown in FIG. 1 ;

[26] FIG. 5 is a schematic diagram illustrating a process of heat-emission operations in the heat storage system shown in FIG. 1 ; and

[27] FIG. 6 is a schematic diagram illustrating a process of parallel operations in the heat storage system shown in FIG. 1.

[28]

Best Mode for Carrying Out the Invention

[29] Now, a preferred embodiment of a heat storage system and a thermal storage medium freezing unit of the heat storage system in accordance with the present invention will be described in detail with reference to the accompanying drawings.

[30] A heat storage system according to one embodiment of the present invention includes a refrigerator unit 10, a heat storage reservoir 30 in which a thermal storage medium is stored, a thermal storage medium cooling unit 50 and a thermal storage medium freezing unit 70.

[31] The refrigerator unit 10 includes a coolant compressor 12 for compressing a coolant at an elevated temperature and under a high pressure, a condenser unit 14 for bringing the coolant of high temperature and high pressure into heat exchanging with cooling water to cool down the coolant, first and second expansion valves 18, 19 for adia- batically expanding the coolant flowing past the condenser unit 14, first and second evaporators 20, 21 through which the coolant adiabatically expanded in the first and second expansion valves 18, 19 flows to absorb environmental heat, a coolant supply header 22 for distributing the coolant having passed the condenser unit 14 to the first and second evaporators 20, 21, and a coolant returning header 24 for collecting the coolant returned back from the first and second evaporators 20, 21 and supplying it to the coolant compressor 12. A first coolant control valve 25 for controlling flow of the coolant is provided between the first evaporator 20 and the coolant supply header 22, and a second coolant control valve 26 is provided between the second evaporator 2 and the coolant supply header 22.

[32] The condenser unit 14 includes a cooling water circulating pump 15 for circulating the cooling water, a condenser 16 for heat exchanging between the cooling water circulated by the cooling water circulating pump 15 and the coolant discharged from the coolant compressor 12, and a cooling tower 17 for cooling down the cooling water having passed the condenser 16. The refrigerator unit 10 set forth just above is a knowledge of public domain and widely used in the conventional heat storage system, which would justify omission of detailed description in that regard.

[33] The heat storage reservoir 30 for storing the thermal storage medium is designed to store the thermal storage medium which was transformed into an ice slurry state with the use of nighttime electricity. Water or a variety of other aqueous solutions known in the art may be used as the thermal storage medium.

[34] The thermal storage medium cooling unit 50 includes first and second thermal storage medium circulating pumps 51a, 51b and first and second heat exchangers 52, 53. The first and second thermal storage medium circulating pumps 51a, 51b are installed in parallel on a reservoir outlet pipe 54 which in turn is connected to a bottom-side part of the heat storage reservoir 30. The first thermal storage medium circulating pump 51a alone is operated in a heat- storage cooling operation mode in which the thermal storage medium is fed under a relatively low pressure, whereas both the first and second thermal storage medium circulating pumps 51a, 51b are operated in a heat-storage freezing operation mode in which the thermal storage medium is fed under a relatively high pressure. A check valve 61 for preventing any backflow of the thermal storage medium is provided between the heat storage reservoir 30 and the first and second thermal storage medium circulating pumps 51a, 51b.

[35] The first heat exchanger 52 is utilized to transfer ice storage heat to the side of a load 90 and allows the thermal storage medium to heat exchange with cooling water of the load 90 inside the first heat exchanger 52. In the meantime, a bypass pipe 55 is installed to prevent the thermal storage medium from entering the first heat exchanger

52. A three-way control valve 57 is provided at a position where the bypass pipe 55 meets with a connection pipe 56 that interconnects the first heat exchanger 52 and the second heat exchanger 53.

[36] The second heat exchanger 53 contains therein the first evaporator 20 that heat exchanges with the thermal storage medium introduced into the second heat exchanger

53. The thermal storage medium having passed the second heat exchanger 53 is admitted into the heat storage reservoir 30 through a reservoir inlet pipe 58. Connected to the reservoir inlet pipe 58 is a nozzle inlet pipe 59 for introducing the thermal storage medium into a spray nozzle 78. A second three-way control valve 60 is provided at a position where the nozzle inlet pipe 59 and the reservoir inlet pipe 58 meet with each other.

[37] The thermal storage medium freezing unit 70 includes a moisture separator 72, an air compressor 74, an air pressure tank 76, an air pressure control valve 80 and a spray nozzle 78. The moisture separator 72 is adapted to remove gaseous moisture from the air in the heat storage reservoir 30 and is provided therein with a humidity-absorbing filter that absorbs moisture present in the air passing therethrough. It goes without saying that other moisture removing methods known in the art, including a method of removing moisture by cooling down and condensing the air, may be used as long as they can remove the moisture present in the air.

[38] The air compressor 74 serves to compress the air from the heat storage reservoir 30 and supply it to the spray nozzle 78. The air pressure tank 76 stores the air compressed by the air compressor 74 and contains therein the second evaporator 21 in order to ensure that the air introduced into the air pressure tank 76 heat exchanges with the second evaporator 21 and is cooled down accordingly.

[39] The air pressure control valve 80 allows the compressed air in the air pressure tank

76 to be discharged to the spray nozzle 78 only if the pressure of the compressed air is equal to or greater than a predetermined pressure. This is because the thermal storage medium will be frozen only when the air is sprayed from the spray nozzle 78 on or above the predetermined pressure. As an arrangement for assuring that the compressed air in the air pressure tank 76 is discharged to the spray nozzle 78 with the pressure equal to or greater than the predetermined pressure, it may be possible to attach a pressure sensor (not shown) to the air pressure tank 76 such that the air pressure control valve 80 can be opened at the time when the pressure in the air pressure tank 76 as detected by the pressure sensor is equal to or greater than the predetermined pressure. Furthermore, the air pressure tank 76 is provided with a drain line 77 for exhausting condensed water therethrough.

[40] As shown in FIG. 2, the spray nozzle 78 is adapted to receive the air of a pressure equal to or greater than the predetermined pressure from the air pressure tank 76 and the thermal storage medium from the nozzle inlet pipe 59. The spray nozzle 78 is provided with a throttling part 79 whose flow path section area is small. As the thermal storage medium is introduced into the spray nozzle 78, the air of high pressure collides with the thermal storage medium and thus granulates the thermal storage medium. Particularly, the thermal storage medium is introduced into the throttling part 79 where the air flows fastest, thus prompting the thermal storage medium to be granulated in a more efficient manner. In addition, a pressure drop occurs at the throttling part 79 to thereby facilitate introduction of the thermal storage medium. As the granulated thermal storage medium and the air pass through the throttling part 79, the air is expanded to absorb heat from the thermal storage medium. Consequently, the granulated thermal storage medium is sprayed from the spray nozzle 78 in the form of small ice grains.

[41] The size of the ice grains varies with the pressure of the air admitted into the spray nozzle 78. In other words, the ice grains become smaller in size if the air pressure is kept high, but the size of the ice grains grows larger if the air pressure is low. This means that the ice grain size can be controlled by regulating the pressure of the air admitted into the spray nozzle 78. By controlling the size of the ice grains in this manner, it becomes possible to optimize the ice grain size in conformity with the correlation between the circulation of the thermal storage medium and the ice storage heat stored in the thermal storage medium, thus maximizing efficiency of the heat storage system.

[42] Although a single spray nozzle 78 is employed in the illustrated embodiment, it would be possible to utilize a plural number of spray nozzles.

[43] Operations of the heat storage system according to one embodiment of the present invention will be described with reference to FIGS. 3 through 6.

[44] Operation modes of the heat storage system are largely divided into a heat-storage cooling operation mode in which the thermal storage medium is cooled down with the use of cheaper midnight electricity, a heat-storage freezing operation mode in which the thermal storage medium is transformed into an ice slurry state, and a heat-emission operation mode in which the ice storage heat is transferred to the load 90 by virtue of heat exchange with the latter. The heat-emission operation mode are subdivided into a heat storage reservoir exclusive operation mode and a parallel operation mode in which the heat storage reservoir exclusive operation is carried out simultaneously with one or both of the heat-storage cooling operation and the heat-storage freezing operation. Operations in each of the afore-mentioned modes will be set forth below.

[45] Referring to FIG. 3, first of all, the coolant compressor 12 is driven to perform the heat-storage cooling operation mode, at which time the first coolant control valve 25 is opened and the second coolant control valve 26 is closed. The coolant of high temperature and high pressure discharged from the coolant compressor 12 is fed to the condenser 16. The coolant in the condenser 16 is brought into heat exchange with the cooling water circulated by the cooling water circulation pump 15 and chilled in the cooling tower 17, whereby the coolant becomes low in temperature and high in pressure. Passing through the condenser 16, the coolant is supplied to the first expansion valve 18 via the coolant supply header 22 and then adiabatically expanded in the first expansion valve 18, after which the coolant is introduced into the first evaporator 20. In the first evaporator 20, the coolant pulls down an environmental temperature and then returns to the coolant compressor 12 via the coolant returning header 24.

[46] Meanwhile, the thermal storage medium is caused to flow toward the bypass pipe

55 by driving the first thermal storage medium circulating pump 51a, at which time the first three-way control valve 57 prevents the thermal storage medium from passing through the first heat exchanger 52. The thermal storage medium having passed the bypass pipe 55 is admitted into the second heat exchanger 53 and cooled down by making heat exchange with the first evaporator 20 therein. The thermal storage medium having passed the second heat exchanger 53 is not fed to the spray nozzle 78 but to the heat storage reservoir 30 under the action of the second three-way control valve 60.

[47] The above-noted cycle is repeatedly performed to ensure that the thermal storage medium stored in the heat storage reservoir 30 is cooled down to a temperature of about O⁰C. Subsequently, the heat-storage cooling operation mode is converted to the heat-storage freezing operation mode either automatically under the control of a control part (not shown in the drawings) or manually by the intervention of an operator.

[48] Referring to FIG. 4, in order to perform the heat-storage freezing operation mode, the first coolant control valve 25 is shut off and the second coolant control valve 26 is opened. This makes sure that the coolant discharged from the coolant compressor 12 is admitted into the second evaporator 21 via the coolant supply header 22 and the second expansion valve 19. The air compressor 74 is driven to suck up the air in the heat storage reservoir 30 through the moisture separator 72. The air is compressed by the air compressor 74 and then fed to the air pressure tank 76. If the pressure in the air pressure tank 76 soars up to a predetermined pressure, the air pressure control valve 80 is opened to feed the air of high pressure to the spray nozzle 78.

[49] In the meantime, the thermal storage medium is circulated under a high pressure by the combined actuation of the first and second thermal storage medium circulating pumps 51a, 51b. The first three-way control valve 57 directs the thermal storage medium to the bypass pipe 55 and not to the first heat exchanger 52. Furthermore, the thermal storage medium having passed the second heat exchanger 53 is not directly introduced into the heat storage reservoir 30 but fed to the spray nozzle 78 under the action of the second three-way control valve 60.

[50] The thermal storage medium introduced into the spray nozzle 78 collides with and is granulated by the air of high pressure. In the spray nozzle 78, the air passes through the throttling part 79 (see FIG. 2) and absorbs the environmental heat to thereby transform the granulated thermal storage medium into small-sized ice grains. Therefore, the thermal storage medium is dropped into the heat storage reservoir 30 in the form of small-sized ice grains. By repeatedly conducting such process, the heat storage reservoir 30 is filled with the ice slurry of thermal storage medium.

[51] FIGS. 5 and 6 show a heat-emission operation mode in which the ice storage heat stored in the ice slurry of thermal storage medium by use of nighttime electricity is transferred to the load 90. The heat-emission operation mode may be divided into a heat storage reservoir exclusive operation and a parallel operation.

[52] Referring to FIG. 5, if the first thermal storage medium circulating pump 51a is driven to perform the heat storage reservoir exclusive operation, the thermal storage medium transfers its heat to the load 90 while passing through the first heat exchanger 52 and returns to the heat storage reservoir 30 via the second heat exchanger 53 and the reservoir inlet pipe 58. At this time, the first three-way control valve 57 closes off the bypass pipe 55 so that the thermal storage medium can be fed only to the first heat exchanger 52. The second heat exchanger 53 does not cool down the thermal storage medium because the refrigerator unit 10 is kept inoperative. In addition, the second three-way control valve 60 shuts off the nozzle inlet pipe 59 to ensure that no thermal storage medium is introduced into the spray nozzle 78.

[53] In the event that the load 90 requires a relatively small cooling capacity, the heat storage reservoir exclusive operation will suffice for cooling down the load 90. In the summer daytime, for example, the heat storage reservoir exclusive operation may fail to provide a cooling capacity great enough to cool down the load 90. In such an instance, as can be seen in FIG. 6, it is necessary to perform the parallel operation whereby the heat storage reservoir exclusive operation is conducted in combination with the heat-storage cooling operation that cools down the thermal storage medium with the use of the refrigerator unit 10. In case an even greater cooling capacity is required, it would be possible to simultaneously perform the heat-storage cooling operation, the heat-storage freezing operation and the heat storage reservoir exclusive operation.

[54]

[55]

[56]

Industrial Applicability

[57] As described in the foregoing, the present invention provides a heat storage system that stores the surplus electricity in the form of ice storage heat in the nighttime and utilizes the ice storage heat in the daytime. The heat storage system can be applied in a variety of industrial fields that require air conditioning, including a refrigerating warehouse for storage of various goods such as agricultural and marine products and an air conditioning system for buildings.

[58]

Claims

[1] A thermal storage medium freezing unit for use in a heat storage system, comprising: an air compressor for sucking and compressing an air from a heat storage reservoir in which a thermal storage medium is stored; and a spray nozzle for spraying the air compressed by the air compressor into the heat storage reservoir together with the thermal storage medium to freeze the thermal storage medium.

[2] The unit as recited in claim 1, wherein the thermal storage medium collides with and is granulated by the compressed air as the thermal storage medium and the compressed air are introduced through the spray nozzle, and the granulated thermal storage medium is frozen by the air sprayed from the spray nozzle and expanded.

[3] The unit as recited in claim 2, further comprising: an air pressure tank for cooling the air compressed by the air compressor, the air pressure tank enclosing therein an evaporator of a refrigerator unit; and an air pressure control valve provided between the air pressure tank and the spray nozzle for allowing the air in the air pressure tank to flow toward the spray nozzle if the pressure in the air pressure tank is equal to or greater than a predetermined value.

[4] The unit as recited in claim 3, further comprising a moisture separator for separating moisture from the air sucked up by the air compressor.

[5] The unit as recited in claim 4, wherein the spray nozzle is provided with a throttling part whose flow path section area is reduced such that the air can be expanded as it is introduced through the spray nozzle.

[6] The unit as recited in claim 5, wherein the air pressure tank is provided with a drain line for exhausting condensed water therethrough.

[7] A heat storage system, comprising: a refrigerator unit provided with first and second evaporators; a heat storage reservoir in which a thermal storage medium is stored; a thermal storage medium cooling unit for cooling the thermal storage medium by causing the thermal storage medium stored in the heat storage reservoir to make heat exchange with the first evaporator; and a thermal storage medium freezing unit for bringing the air in the heat storage reservoir into heat exchange with the second evaporator, wherein the thermal storage medium freezing unit comprises: an air compressor for sucking and compressing the air in the heat storage reservoir; and a spray nozzle for spraying the air compressed by the air compressor into the heat storage reservoir together with the thermal storage medium to freeze the thermal storage medium.

[8] The system as recited in claim 7, wherein the thermal storage medium cooling unit comprises: a thermal storage medium circulating pump for circulating the thermal storage medium stored in the heat storage reservoir; a first heat exchanger for causing the thermal storage medium to make heat exchange with a load as the thermal storage medium is circulated by the thermal storage medium circulating pump; a second heat exchanger for causing the thermal storage medium to make heat exchange with the first evaporator as the thermal storage medium is circulated by the thermal storage medium circulating pump; a reservoir inlet pipe in fluid communication with the heat storage reservoir for returning the thermal storage medium to the heat storage reservoir after passing through the second heat exchanger; and a nozzle inlet pipe connected to the reservoir inlet pipe for feeding the thermal storage medium to the spray nozzle.

[9] The system as recited in claim 8, further comprising a three-way control valve disposed at a position where the reservoir inlet pipe meets with the nozzle inlet pipe.

[10] The system as recited in claim 9, wherein the thermal storage medium freezing unit comprises: an air pressure tank for cooling the air compressed by the air compressor, the air pressure tank enclosing therein the second evaporator; and an air pressure control valve provided between the air pressure tank and the spray nozzle for allowing the air in the air pressure tank to flow toward the spray nozzle if the pressure in the air pressure tank is equal to or greater than a predetermined value.

[11] The system as recited in claim 10, wherein the air pressure tank is provided with a drain line for exhausting condensed water therethrough.

[12] The system as recited in claim 11, wherein the spray nozzle is provided with a throttling part whose flow path section area is reduced such that the air can be expanded as it is introduced through the spray nozzle.