Patent Application
20110079025
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.
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.
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.
The refrigeration system 26 includes a cooling fluid and a plurality of plate heat exchangers 50a, 50b receiving a flow of the cooling fluid therethrough in a first cool mode to cool the heat exchangers 50a, 50b. 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 50a, 50b 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 50a 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 50a and the second wall 58. A second set of the heat exchangers 50b 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 50b and the first wall 54. The tank also includes front and rear walls (not shown), and the first and second sets of heat exchangers 50a, 50b may extend from the front and rear walls in other constructions.
The second set of heat exchangers 50b are spaced from the first set of heat exchangers 50a in an alternating fashion such that the gaps alternate and a serpentine-shaped flow path (see arrows in
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
The storage medium detection devices 34a, 34b 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 34a or 34b is employed in the thermal storage device 10. Both storage medium detection devices 34a, 34b are shown together in the figures for ease of illustration.
The first storage medium detection device 34a 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 34b 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 34a, 34b 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 50a, 50b 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 50a, 50b 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 50a, 50b 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 50a, 50b 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 34a, 34b 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.
