US20110079025A1

US20110079025A1 - Thermal storage device with ice thickness detection and control methods

Info

Publication number: US20110079025A1
Application number: US12/572,434
Authority: US
Inventors: William F. Mohs; Bernard Wayne Benson
Original assignee: Thermo King Corp
Current assignee: Thermo King Corp
Priority date: 2009-10-02
Filing date: 2009-10-02
Publication date: 2011-04-07
Also published as: CN102032754A

Abstract

A thermal storage device for generating a thermal storage medium from a fluid and including a storage tank for containing the fluid, a refrigeration system having a heat exchanger positioned in the storage tank, a pump for pumping the fluid through the storage tank, a storage medium detection device, and a controller. The storage medium detection device generates a signal corresponding to at least one parameter of the pump. The controller controls the refrigeration system in one of a first mode and a second mode based on the signal. The at least one heat exchanger removes heat from the fluid to generate the thermal storage medium thereon when the refrigeration system operates in the first mode, and the at least one heat exchanger does not remove heat from the fluid thereby terminating generation of the thermal storage medium when the refrigeration system operates in the second mode.

Description

BACKGROUND

The present invention relates to a thermal storage device, and in particular to a thermal storage device that utilizes ice as the storage medium and includes detection methods for determining ice thickness.

SUMMARY

In one embodiment the invention provides a method of controlling the generation of a thermal storage medium from a fluid. The method includes positioning at least one heat exchanger of a refrigeration system within a storage tank containing the fluid, pumping the fluid with a pump along a flow path in the storage tank, sensing at least one parameter of the pump, generating a signal corresponding to the at least one parameter of the pump, controlling the refrigeration system in one of a first mode and a second mode based on the signal, operating the refrigeration system in a first mode to remove heat from the fluid with the at least one heat exchanger to generate the thermal storage medium on the at least one heat exchanger, and operating the refrigeration system in a second mode in which heat is not removed from the fluid with the at least one heat exchanger, the second mode for terminating generation of the thermal storage medium on the at least one heat exchanger.
In another embodiment, the invention provides a thermal storage device for generating a thermal storage medium from a fluid. The thermal storage device includes a storage tank, a refrigeration system, a pump, a storage medium detection device, and a controller. The storage tank has first and second ports in fluid communication with one another defining a flow path through the storage tank between the first and second ports, and is configured to contain the fluid. The refrigeration system includes at least one heat exchanger positioned within the fluid in the storage tank. The pump is fluidly coupled to the first and second ports and operable to pump the fluid through the flow path. The storage medium detection device is operable to generate a signal corresponding to at least one parameter of the pump. The controller is in electrical communication with the storage medium detection device and the refrigeration system, and is operable to control the refrigeration system in one of a first mode and a second mode based on the signal. The at least one heat exchanger removes heat from the fluid to generate the thermal storage medium thereon when the refrigeration system operates in the first mode, and the at least one heat exchanger does not remove heat from the fluid thereby terminating generation of the thermal storage medium when the refrigeration system operates in the second mode.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a thermal storage device in accordance with the present invention.

FIG. 2 is a schematic cross-sectional view of the thermal storage device of FIG. 1 having a buildup of thermal storage medium.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
FIGS. 1-2 illustrate a thermal storage device 10 for generating a thermal storage medium 14 from a fluid 18, such as ice from water, respectively. The thermal storage device 10 includes a storage tank 22, a refrigeration system 26, a pump 30, first and second storage medium detection devices 34 a, 34 b, and a controller 38. In the illustrated construction, the thermal storage device 10 is used to provide extra cooling capacity during pre-cooling of a perishable product near a harvesting area to immediately begin preserving the shelf life of the perishable product. The thermal storage device 10 is fluidly connected to an appropriately sized hydrocooler 40, such as an immersion hydrocooler or a spray hydrocooler. The thermal storage medium 14 is built up during a non-harvest period, such as overnight. The fluid 18 is cooled by the thermal storage medium 14 during a use period to cool the perishable product. The thermal storage device 10 and hydrocooler 40 constitute a modular system that can be transported to various locations and quickly assembled. In other constructions, other fluids and thermal storage media may be employed, and the thermal storage device 10 may be fluidly connected to other devices for other applications.
The refrigeration system 26 includes a cooling fluid and a plurality of plate heat exchangers 50 a, 50 b receiving a flow of the cooling fluid therethrough in a first cool mode to cool the heat exchangers 50 a, 50 b. It is to be understood that the refrigeration system 26 includes any suitable type of refrigeration system, such as, but not limited to, a direct expansion system having an evaporator or a chilled glycol system having a chilling device.
The heat exchangers 50 a, 50 b are positioned within the fluid 18 in the storage tank 22. The storage tank 22 includes a first wall 54 and a second wall 58 opposite the first wall 54. A first set of the heat exchangers 50 a extends from the first wall 54 substantially perpendicular to the first wall 54 in a cantilevered fashion such that a gap is left between the first set of heat exchangers 50 a and the second wall 58. A second set of the heat exchangers 50 b extends from the second wall 58 substantially perpendicular to the second wall 58 in a cantilevered fashion such that a gap is left between the second set of heat exchangers 50 b and the first wall 54. The tank also includes front and rear walls (not shown), and the first and second sets of heat exchangers 50 a, 50 b may extend from the front and rear walls in other constructions.
The second set of heat exchangers 50 b are spaced from the first set of heat exchangers 50 a in an alternating fashion such that the gaps alternate and a serpentine-shaped flow path (see arrows in FIG. 1) is defined within the storage tank 22. In other constructions, other types of heat exchangers may be employed such that the thermal storage medium 14 may be built up on surfaces of the heat exchangers. In yet other constructions, the heat exchangers 50 a, 50 b may be arranged in other ways that define other shapes of flow paths.
The storage tank 22 contains the fluid 18 and has first and second ports 42, 46 in fluid communication with one another. The serpentine-shaped flow path (see arrows in FIG. 1) through the storage tank 22 extends between the first and second ports 42, 46 from the first port 42 to the second port 46. The pump 30 is fluidly connected to the first and second ports 42, 46 and operable to pump the fluid 18 through the flow path to improve formation of the thermal storage medium 14 during the non-harvest period when the thermal storage medium 14 is built. During the non-harvest period, the pump 30 operates to circulate the fluid 18 in a first circuit, which includes the first port 42, the serpentine-shaped flow path, and the second port 46. After exiting the second port 46, the pump recirculates the cooling fluid 18 back to the first port 42. During the use period, the hydrocooler 40 operates to circulate the fluid 18 in a second circuit, which includes the first port 42, the serpentine-shaped flow path, the second port 46, and the hydrocooler 40, which includes an additional pump 66 that returns the fluid 18 to the first port 42 for recirculation through the storage tank 22. The second circuit also includes valves 62 for closing off the second circuit in a closed position and opening the second circuit in an open position. The valves 62 are closed during the non-harvesting period and open during the use period.
The storage medium detection devices 34 a, 34 b are operable to generate a signal corresponding to at least one parameter of the pump 30. In some constructions, only one storage medium detection device 34 a or 34 b is employed in the thermal storage device 10. Both storage medium detection devices 34 a, 34 b are shown together in the figures for ease of illustration.
The first storage medium detection device 34 a includes a pair of pressure sensors positioned upstream and downstream of the pump 30 to measure a pressure differential across the pump 30. The pressure differential is indicative of a size of the thermal storage medium 14, e.g., a thickness of the thermal storage medium 14. The thicker the thermal storage medium 14, the smaller a flow area in the serpentine-shaped flow path. As the thermal storage medium 14 increases in thickness, the pressure differential across the pump 30 increases. When the pressure differential reaches a predetermined differential, the controller 38 ceases formation of the thermal storage medium 14.
The second storage medium detection device 34 b includes a power consumption meter, such as a watt meter, to measure the power consumption of the pump 30. As the flow area in the serpentine-shaped flow path decreases, the power consumption of the pump 30 increases. Thus, an increase in power consumption of the pump 30 is indicative of increasing thickness of the thermal storage medium 14. When the power consumption of the pump 30 reaches a predetermined amount, the controller 38 will cease formation of the thermal storage medium 14.
The controller 38 is in electrical communication with the storage medium detection devices 34 a, 34 b and the refrigeration system 26, and is operable to control the refrigeration system 26 in one of a first mode and a second mode based on the signal. The heat exchangers 50 a, 50 b remove heat from the fluid 18 to generate the thermal storage medium thereon 14 when the refrigeration system 26 operates in the first mode, and the heat exchangers 50 a, 50 b do not remove heat from the fluid 18, thereby terminating generation of the thermal storage medium 14 when the refrigeration system 26 operates in the second mode. For example, the controller 38 may cease operation of the refrigeration system 26 and/or operation of the pump 30.
In operation, the thermal storage medium 14 is built up during the non-harvest period, such as overnight, during which period the refrigeration system 26 operates in the first mode. The heat exchangers 50 a, 50 b are cooled by the refrigeration system 26 and the fluid 18 is pumped by the pump 30 along the first circuit (i.e., the valves 62 are closed) to increase formation of the thermal storage medium 14 on surfaces of the heat exchangers 50 a, 50 b in the serpentine-shaped flow path. This stores cooling potential for future use during high load or peak demand to minimize the peak demand. Furthermore, this allows a smaller refrigeration system to be utilized at a high utilization rate (e.g., all day). If the signal generated by one of the storage medium detection devices 34 a, 34 b and received by the controller 38 is indicative of a predetermined thermal storage medium thickness, the controller 38 ceases formation of the thermal storage medium 18 to prevent the flow path from being completely blocked.
During the use period, the valves 62 are set to the open position and the fluid 18 is directed to the thermal storage device 10 where the fluid 18 is cooled by the thermal storage medium 14. The fluid 18 is then directed to the hydrocooler 40 where the perishable product is cooled, for example, by immersion or spraying. The fluid 18 is then collected and redirected back to the thermal storage device 10 to be re-cooled and re-used for additional perishable product cooling.
Thus, the invention provides, among other things, a thermal storage device for generating a thermal storage medium from a fluid and a method of controlling the generation of a thermal storage medium from a fluid. Various features and advantages of the invention are set forth in the following claims.

Claims

1. A method of controlling the generation of a thermal storage medium from a fluid, the method comprising:

positioning at least one heat exchanger of a refrigeration system within a storage tank containing the fluid;

pumping the fluid with a pump along a flow path in the storage tank;

sensing at least one parameter of the pump;

generating a signal corresponding to the at least one parameter of the pump;

controlling the refrigeration system in one of a first mode and a second mode based on the signal;

operating the refrigeration system in the first mode to remove heat from the fluid with the at least one heat exchanger to generate the thermal storage medium on the at least one heat exchanger; and

operating the refrigeration system in the second mode in which heat is not removed from the fluid with the at least one heat exchanger, the second mode for terminating generation of the thermal storage medium on the at least one heat exchanger.

2. The method of claim 1, further comprising:

directing a cooling fluid of the refrigeration system through one of an evaporator and a chilling device in the first mode to cool the fluid in the storage tank.

3. The method of claim 1, wherein generating a signal includes generating a signal corresponding to a pressure difference across the pump.

4. The method of claim 1, wherein generating a signal includes generating a signal corresponding to power consumed by the pump while pumping the fluid along the flow path.

5. The method of claim 1, further comprising correlating the at least one parameter to a particular size of the thermal storage medium.

6. The method of claim 1, wherein positioning at least one heat exchanger of a refrigeration system within a storage tank includes staggering a plurality of plates in an alternating fashion within the storage tank such that the plurality of plates define a serpentine-shaped path within the storage tank, and wherein pumping the fluid with a pump along a flow path includes pumping the fluid with the pump along the serpentine-shaped path.

7. The method of claim 6, wherein staggering a plurality of plates in an alternating fashion within the storage tank includes arranging every other of the plurality of plates on a first wall of the storage tank, and arranging the remaining of the plurality of plates on a second wall of the storage tank opposite the first wall.

8. The method of claim 1, wherein operating the refrigeration system in the second mode includes operating the refrigeration system in the second mode to prevent the thermal storage medium from closing the flow path.

9. The method of claim 1, wherein pumping the fluid in the flow path occurs during the first mode to improve formation of the thermal storage medium.

10. A thermal storage device for generating a thermal storage medium from a fluid, the thermal storage device comprising:

a storage tank including first and second ports in fluid communication with one another defining a flow path through the storage tank between the first and second ports, the storage tank configured to contain the fluid;

a refrigeration system including at least one heat exchanger positioned within the fluid in the storage tank;

a pump fluidly coupled to the first and second ports and operable to pump the fluid through the flow path;

a storage medium detection device operable to generate a signal corresponding to at least one parameter of the pump; and

a controller in electrical communication with the storage medium detection device and the refrigeration system, the controller operable to control the refrigeration system in one of a first mode and a second mode based on the signal, wherein the at least one heat exchanger removes heat from the fluid to generate the thermal storage medium thereon when the refrigeration system operates in the first mode, and wherein the at least one heat exchanger does not remove heat from the fluid thereby terminating generation of the thermal storage medium when the refrigeration system operates in the second mode.

11. The thermal storage device of claim 10, wherein the at least one parameter is indicative of a characteristic of the thermal storage medium.

12. The thermal storage device of claim 11, wherein the characteristic includes a size of the thermal storage medium.

13. The thermal storage device of claim 10, wherein the at least one parameter includes a pressure difference across the pump.

14. The thermal storage device of claim 10, wherein the at least one parameter includes power consumed by the pump while pumping the fluid through the flow path.

15. The thermal storage device of claim 10, wherein the at least one heat exchanger includes a plate heat exchanger.

16. The thermal storage device of claim 10, wherein the fluid includes water and the thermal storage medium includes ice.

17. The thermal storage device of claim 10, wherein the flow path includes a serpentine-shape.

18. The thermal storage device of claim 10, wherein the refrigeration system includes a cooling fluid, and wherein the at least one heat exchanger receives a flow of cooling fluid therethrough in the first mode to cool the at least one heat exchanger.

19. The thermal storage device of claim 10, wherein the storage tank includes a first wall and a second wall opposite the first wall, wherein the at least one heat exchanger includes a first plate heat exchanger and a second plate heat exchanger, and wherein the first plate heat exchanger extends from the first wall and the second plate heat exchanger extends from the second wall and is spaced from the first plate heat exchanger such that a serpentine-shaped path is defined within the storage tank by the first and second plate heat exchangers, wherein the flow path includes the serpentine-shaped path.

20. The thermal storage device of claim 10, wherein the storage medium detection device includes a static pressure switch that generates the signal corresponding to a rise in pressure across the pump.

21. The thermal storage device of claim 20, wherein the rise in pressure across the pump is indicative of a maximum thermal storage medium thickness.

22. The thermal storage device of claim 10, wherein the pump is operable to improve formation of the storage medium during the first mode.

23. A method of controlling the generation of a thermal storage medium from a fluid, the method comprising:

staggering a plurality of heat exchanger plates in an alternating fashion within a storage tank containing the fluid such that the plurality of heat exchanger plates define a serpentine-shaped path within the storage tank;

pumping the fluid with a pump along the serpentine-shaped path in the storage tank;

sensing at least one parameter of the pump, wherein the at least one parameter of the pump includes at least one of a pressure difference across the pump and power consumed by the pump while pumping the fluid along the flow path;

generating a signal corresponding to the at least one parameter of the pump;

correlating the at least one parameter of the pump to a particular size of the thermal storage medium;