KR20090024171A - Pulse electrothermal deicing of complex shapes - Google Patents

Abstract

A pulse electrothermal deicing apparatus comprises at least one complex shape characterized by a thickness profile configured to generate uniform power per unit area to melt an interfacial layer of ice. A method of optimizing thicknesses of complex shapes for a pulse electrothermal deicing system includes assigning initial estimates of the pulse electrothermal deicing system parameters. A temperature distribution, a temperature range and a refreezing time produced by a deicing pulse are modeled. Shape thicknesses are adjusted according to the temperature range, deicing pulse parameters are adjusted according to the deicing pulse, and the modeling and adjusting is repeated until the temperature range and the refreezing time are within predetermined limits.

Description

PULSE ELECTROTHERMAL DEICING OF COMPLEX SHAPES

<Related application>

This application claims the priority status of co-owned pending patent application US Provisional Patent Application No. 60 / 802,407, filed May 22, 2006. This application also claims priority to US Provisional Patent Application Nos. 60 / 646,394, filed Jan. 24, 2005, 60 / 646,932, filed Jan. 25, 2005, and 60 / 739,506, filed Nov. 23, 2005, Some ongoing applications of co-owned pending PCT / US2006 / 002283, filed Jan. 24, 2006. This application also claims priority to U.S. provisional patent applications filed on June 22, 2004, application number 60 / 581,912, filed on January 24, 2005, application number 60 / 646,394, filed on January 25, 2005. It is partly pending application of the co-owned pending US patent application Ser. No. 11 / 571,231, filed on December 22, 2006, which claims priority over PCT / US2005 / 022035, filed on June 22, 2005, claiming status. . This application is also a co-owned pending US patent application, filed on Jan. 24, 2006, filed on Sep. 10, 2004, now claiming priority status for US Patent Application No. 10 / 939,289, now registered patent 7,034,257. Part of the application of No. 11 / 338,239. The registered patent 7,034,257 is a priority for US provisional patent applications of application number 60 / 646,394, filed on Feb. 11, 2002, application number 60 / 398,004, filed on Aug. 21, 2002, and application no. 60 / 404,872, filed on Aug. 21, 2002. A split application filed on February 11, 2003, which claims priority, now claims priority to US Patent Application No. 10 / 364,438, which is now US Patent 6,870,139. All patent applications identified above are hereby incorporated by reference.

Ice making, which melts or tears ice with electrically generated heat (joule heat), has many applications. Some of these applications benefit from minimizing the energy applied to the ice and / or the object to which the ice is attached. For example, producing more heat than necessary to melt or at least tear off ice requires excessive energy consumption. In some devices, such as in ice making or deicing of refrigeration equipment, the consumption of extra energy in breaking ice is particularly disadvantageous; Not only is energy consumed to melt the ice, more energy may be consumed to recool the portion of the system from which the ice is removed to the cooling system.

In one embodiment, the pulse electrothermal deicing device comprises at least one composite shape characterized by a thickness profile configured to generate a constant power per unit area to melt the interfacial layer of ice. .

In one embodiment, a composite shape thickness optimization method for a pulsed ice making system comprises the steps of: assigning a size and geometry to each shape and connectivity of the shapes; Assigning an initial thickness to each shape; Assigning an initial estimate to the ice making pulse duration; Modeling a temperature distribution on the surface of each shape based on the ice making pulse duration and the thickness of each shape; After application of the ice making pulse, determining a refreezing time for each shape; If the modeled temperature distribution is not within the required tolerance range, adjusting the thickness of each shape based on the modeled temperature distribution; Adjusting the ice making pulse duration based on the determined refreezing time; And if the determined re-freezing time is not within a defined limit, repeating the modeling, determining and adjusting steps until the temperature distribution is within the required tolerance range and the re-freezing time is within a defined limit. It includes.

In one embodiment, the pulsed ice making device comprises at least one axially symmetric composite shape characterized by a thickness profile configured to produce a constant power per unit area to melt the interfacial layer of ice.

1 shows one exemplary pulse electrothermal deicing (PET) device comprising a plate according to one embodiment of the present invention.

2 shows one representative PETD device including a cylinder, according to one embodiment of the invention.

3 shows one representative PETD device including a cone, according to one embodiment of the invention.

4 shows one representative PETD device including a sphere, according to one embodiment of the invention.

5 shows one representative PETD device comprising a crescent, in accordance with an embodiment of the present invention.

6 shows the rendition of an ice tray for a representative residential icemaker having an axial symmetrical shape.

7 is a flow chart illustrating a representative method of optimizing the thickness of conductive composite shapes in a PETD system design in accordance with an embodiment of the present invention.

Pulsed ice making (PETD) can be used to separate ice from an object by melting at least the interfacial layer of ice. As used herein, the term "ice" refers to any of ice, snow, frost and other forms of frozen water, with or without mixed matter. "Interfacial layer of ice" refers to a thin layer in close proximity to an object. Melting of the interfacial layer of ice is generally sufficient to separate bulk ice (ie, the insoluble portion of the ice) from the object. The interfacial layer of ice may have a thickness of about 5 cm or less, preferably about 3 cm or less, more preferably between about 1 cm and 1 μm, most preferably between 1 mm and 1 μm. It will be appreciated that the heat applied to heat the interfacial ice also heats some of the objects in contact with the interfacial ice. Heat is to a distance of 5 cm or less inside the object and / or ice, preferably 3 cm or less inside the object and / or ice, more preferably between about 1 cm and 1 μm inside the object and / or ice, most preferably the object and / or It is desirable to diverge to a distance between about 1 mm and 1 μm in the ice.

The energy consumed in PETD is advantageously minimized by providing a constantly melted interfacial layer. Excessively thick molten interfacial layers correspond to higher ice making temperatures and represent energy wasted in the ice making process. That is, more energy is applied than is necessary to separate the large ice from the object. For example, in an icemaker, a "hot spot" created during deicing requires recooling after ice making, before ice production begins again at that spot. . This lowers the yield of the ice making process by melting more intended products than necessary. Too thin a molten interfacial layer risks re-freezing of the large ice before the ice can be removed.

In order to optimize the energy consumption for ice making, devices utilizing PETD must provide approximately constant heating power density per surface area of the interfacial ice layer. However, a constant heating power density per surface area can be difficult to achieve when the object to be iced has a complex shape. As used herein, a "complex shape" refers to a portion of an object that has one or more walls of non-uniform thickness. The composite shape can be described as a "thickness profile", where the thickness profile defines the thickness of the wall over distance (eg from one point on the object to another point on the object).

The heating layer of the object is characterized by electrical resistivity ρ and thickness t. When heating power W per unit area is applied, the following relation applies.

..............................식(1)

.............. Equation (1)

Here, E is the intensity (V / m) of the electric field developed through the heating layer by application of the current density I _s (A / m). In order to keep W constant at various parts of the heating layer, the following relation further applies.

...................................식(2)

Equation (2)

Equation (2) is approximate because it does not consider the dependence of the heat capacity of the heating layer based on the object thickness.

However, equation (2) is very useful because the heat capacity is usually a very small provision in the total PETD energy requirement compared to the heat capacity of the underlying ice, and the latent heat of the melted interfacial ice layer.

1 shows one representative PETD device 10 (1) comprising a plate 40 (1). 1 may not be drawn to scale. The power supply 20 (1) is connected to the flat plate 40 (1) via a switch 30 (1) to supply power for the ice making to the plate 40 (1). The length L and the thickness t of the flat plate 40 (1) are shown in FIG. When the power supply device 20 (1) supplies the voltage V, the power W supplied by the power supply device 20 (1) may be expressed as follows in terms of power per unit area.

..................................................식(3)

........................................ Formula (3)

2 shows one representative PETD device 10 (2) comprising a cylinder 40 (2). 2 may not be drawn to scale. The power supply 20 (2) is connected to the cylinder 40 (2) via a switch 30 (2) to supply power to the cylinder 40 (2) for ice making. The length L and the thickness t of the cylinder 40 (2) are shown in FIG. When the power supply 20 (2) supplies a voltage V, the power W supplied by the power supply 20 (2) can be expressed by power per unit area as shown in equation (3) It describes an object with a certain thickness.

3 shows a cross section of one representative PETD device 10 (3) comprising a cone 40 (3). 3 may not be drawn to scale. The power supply 20 (3) is connected via a switch 30 (3) to supply power for the ice making to the cone 40 (3). The linear dimension x, the angle [theta] with respect to the x-axis, and the thickness t of the cone 40 (3) are shown in FIG. Note that the thickness t varies with the position along the x axis of the cone 40 (3). When the power supply device 20 (3) supplies a voltage V and a current I ₀ , the thickness t required to provide a constant power W per unit area can be expressed as follows.

................................식(4)

Equation (4)

4 shows a cross section of one representative PETD device 10 (3) comprising a sphere 40 (4). 4 may not be drawn to scale. The power supply 20 (4) is connected to the sphere 40 (4) via a switch 30 (4) to supply the sphere 40 (4) with power for ice making. The radius R, the angle θ relative to the axis along which power is supplied, and the thickness t of the sphere 40 (4) are shown in FIG. It should be noted that the thickness t of the sphere 40 (4) varies with the angle θ. When the power supply device 20 (4) supplies a voltage V and a current I ₀ , the thickness t required to provide a constant power W per unit area can be expressed as follows.

................................식(5)

Equation (5)

5 shows one representative PETD device 10 (3) comprising a crescent 40 (5). 5 may not be drawn to scale. Crescent 40 (5) may be produced by the rotation of the line about the axis of rotation. These shapes can be, for example, (1) filled with liquid water, (2) cooled until water freezes to form ice, (3) rotates to face ice downwards, or (4) It may be useful for ice makers that are heated with an ice making pulse to separate the ice from the shape. The power supply 20 (5) is connected via a switch 30 (3) to supply the crescent 40 (5) with power for ice making. The linear dimension x, the offset value R (x) as a function of position on the x-axis, and the thickness t of the crescent 40 (5) are shown in FIG. Note that the thickness t of the shape varies with R (x). If the power supply device 20 (5) supplies a voltage V and a current I ₀ , it can be explained that the thickness t required to provide a constant power W per unit area can be expressed as follows.

................................식(6)

Equation (6)

For manufacturing any of the shapes 40 described above, but not limited to, continuous application of die casting, injection molding, conductive paint or other coating materials. Various techniques may be utilized including application, machining and the like.

Figure 6 shows the rendition of an ice tray of a residential ice maker. Ice makers using the ice tray 50 may be made of a thermally conductive and electrically conductive composite material, such as E5101 from CoolPolymers. The inner shape 40 (6) of the ice tray 50 is symmetric in the axial direction. To form ice, the tray 50 is arranged with the interior shape 40 (6) facing up. The tray 50 is then filled with water. After the water freezes on ice, the tray 50 is rotated about 120 ° about its long axis, with two second pulses of power 60 (1) and 60 (2) across the terminals of the tray 50. It is applied via copper bus bars disposed on it. Electrical power uniformly heats the tray 50 to a temperature just above the melting point of the ice, melting the interfacial layer of ice. The ice then slides off the tray 50 and enters into a collecting vessel (not shown). It is understood that the tray 50 includes a compound, variable thickness. The thickness can be calculated using equation (6), and the thickness can be adjusted at a constant position such as a corner, according to the method described below.

7 is a flow diagram illustrating one representative method 100 for optimizing the thickness of a conductive composite shape in a PETD system design. It will be appreciated that some or all of the steps shown in FIG. 7 may be performed by a computer under the control of software instructions. Or alternatively, some or all of the steps in FIG. 7 may be performed by a human. In step 102, the method 100 assigns a size and geometry type to each shape of the ice making system and the connections between the shapes. In step 104, the method 100 assigns an initial thickness configuration to each shape. Such a setting may be determined by the position and / or angle (Figs. 3-5 and Equation (4) in the case where the fixed thickness (e.g., as shown in Figs. May vary in thickness as a function of)-(6). In step 106, deicing pulse parameters are assigned, such as the voltage or current supplied, and an initial estimate of the deicing pulse duration. In step 108, the temperature distribution, temperature range and refreezing time obtained for a particular shape via a particular ice making pulse is determined. For example, step 108 may be performed utilizing finite element method modeling using a package such as Comsol's FEMLAB 3.1. Step 110 is a determination step of determining whether the temperature range is within a certain tolerance. If the temperature range is outside a certain tolerance range (i.e. there is a greater difference than the required difference between the lowest and highest temperatures produced by the de-icing pulse), the shapes may be too high or too low for the modeled temperature of the shape. Depending on the thickness or thickness, respectively, in steps 112 and 114, respectively. Step 116 is a determination step. In step 116, the refreezing time is compared to a specific minimum and maximum limit. If the refreezing time is too short (ie, below a certain minimum limit), the deicing pulse is extended in step 118. If the refreezing time is too long, the deicing pulse is shortened in step 120. It will be appreciated that the power parameters of the ice making pulse can be modified, such as to provide more or less power instead of changing the duration of the ice making pulse or in addition to changing the duration of the ice making pulse. . If either of the shape thickness and the refreezing time changes in steps 112, 114, 118 and / or 120 the method returns to step 108. If not, the method ends at 122 and yields a set of optimized thickness and ice making pulse parameters.

The above described or other modifications may be made to the pulsed electrothermal ice maker and associated methods for the complex shape described herein without departing from the scope of the present invention. For example, as opposed to the thickness of a composite shape, a change in heating can be provided by changing the electrical resistivity. The principles described herein are also applicable to configurations such as cooling evaporator plates or air conditioning systems that require periodic deicing. Accordingly, it should be noted that the matter included in the above description or illustrated in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all the general and specific features described herein as well as all the statements of the scope of the present method and system in which they can be referred to as belonging between them.

Claims (18)

And at least one compound shape characterized by a thickness profile configured to produce a constant power per unit area to melt the interfacial layer of ice. The method of claim 1, And an electric power supply and a switch for selectively connecting and disconnecting the electric power supply from the complex shape. The method of claim 1, The composite shape includes one cone, and the thickness t of the cone varies according to the following equation.

(Here, the cone is characterized by a linear dimension x along the x axis and an angle θ with respect to the x axis, the power supply supplying a current I ₀ to provide power W per unit area.) The method of claim 1, The complex shape includes one sphere, and the thickness t of the sphere varies according to the following equation.

(Here, the sphere is characterized by the radius R and the angle θ with respect to the axis powered by it, the power supply supplying a current I ₀ to provide power W per unit area.) The method of claim 1, The complex shape includes one crescent, and the thickness t of the crescent varies according to the following equation.

(Here, the crescent is characterized by a linear dimension x and an offset value R (x), wherein the power supply supplies current I ₀ to provide power W per unit area. The method of claim 1, Wherein said complex shape is formed by one of die casting, injection molding, machining, and continuous application of a conductive layer. A method of optimizing the thickness of a complex shape for a pulsed ice making system, Assigning size and geometry to each shape and connectivity of said shapes; Assigning an initial thickness to each shape; Assigning an initial estimate to the ice making pulse duration; Modeling a temperature distribution on the surface of each shape based on the ice making pulse duration and the thickness of each shape; After application of the ice making pulse, determining a refreezing time for each shape; If the modeled temperature distribution is not within the required tolerance range, adjusting the thickness of each shape based on the modeled temperature distribution; Adjusting the ice making pulse duration based on the determined refreezing time; And If the determined re-freezing time is not within a defined limit, repeating the modeling, determining and adjusting steps until the temperature distribution is within the required tolerance range and the re-freezing time is within a defined limit. Method for optimizing the thickness of the complex shape for a pulsed electrothermal ice making system comprising a. The method of claim 7, wherein Adjusting the thickness is, Increasing the thickness of the shape where the temperature distribution is above the required tolerance range; And Reducing the thickness of the shape where the temperature distribution is below the required tolerance range. The method of claim 7, wherein And assigning an initial thickness to each shape comprises assigning a fixed thickness to each shape. The method of claim 7, wherein The step of assigning the initial thickness to each shape comprises the step of assigning a variable thickness to each shape thickness optimization method for a complex shape for a pulsed ice making system. The method of claim 7, wherein And adjusting the ice making pulse duration, shortening the duration if the determined re-icing time is greater than or equal to a predetermined limit. The method of claim 7, wherein And adjusting the ice making pulse duration, extending the duration if the determined re-icing time is less than or equal to a predetermined limit. And at least one axially symmetric composite shape characterized by a thickness profile configured to produce a constant power per unit area to melt the interfacial layer of ice. The method of claim 13, And a switch for selectively connecting and disconnecting the power supply from the power supply device and the axially symmetrical composite shape. The method of claim 13, Wherein said axially symmetric composite shape comprises one cone, and wherein the thickness t of said cone varies according to the following equation.

(Here, the cone is characterized by a linear dimension x along the x axis and an angle θ with respect to the x axis, the power supply supplying a current I ₀ to provide power W per unit area.) The method of claim 13, Wherein said axially symmetric composite shape comprises one sphere, and said thickness t of said sphere varies according to the following equation.

(Here, the sphere is characterized by the radius R and the angle θ with respect to the axis powered by it, the power supply supplying a current I ₀ to provide power W per unit area.) The method of claim 13, Wherein said axially symmetrical composite shape comprises one crescent, and wherein said thickness of said crescent is varied according to the following equation.

(Here, the crescent is characterized by a linear dimension x and an offset value R (x), wherein the power supply supplies current I ₀ to provide power W per unit area. The method of claim 13, Wherein said axially symmetric composite shape is formed in one of die casting, injection molding, machining, and continuous application of a conductive layer.

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