Twin screw heating pumps and systems

Abstract

A twin screw heating pump including a first screw twin and a second screw twin disposed within a casing and axially spaced apart from one another to define a central chamber therebetween, wherein the first screw twin is adapted to convey fluid from an inlet to the central chamber, and wherein the second screw twin is adapted to convey fluid from the central chamber to an outlet, and wherein a volumetric flow rate of the first screw twin is greater than a volumetric flow rate of the second screw twin.

Description

TWIN SCREW HEATING PUMPS AND SYSTEMSCross-Reference To Related Applications

[0001] This application claims priority to U.S. Patent Application Serial No. 63 / 516,554, filed July 31, 2023, the disclosure of which is incorporated herein by reference in its entirety.Field of the Disclosure

[0002] The present disclosure relates generally to screw pumps or screw machines such as, for example, twin screw pumps, and more particularly to twin screw pumps adapted to heat fluids that are being pumped.Background of the Disclosure

[0003] Many chemical processes require fluid to be both pumped and heated. In most cases, a heater or heat exchanger can be used to add thermal energy to a fluid, and a pump is only required to move the fluid at a required flow at a given temperature and viscosity. In some applications, however, heaters and heat exchangers cannot be used due to considerations such as cost, space requirements, environmental constraints, sensitivity of the fluid being handled, etc. In such cases, alternative techniques must be employed to add thermal energy to the fluid to achieve necessary temperatures and / or viscosities.

[0004] It is with respect to these and other considerations the present disclosure is provided.Summary

[0005] This Summary is provided to introduce a selection of concepts in a simplified form further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is the summary intended as an aid in determining the scope of the claimed subject matter.

[0006] A twin screw heating pump in accordance with an embodiment of the present disclosure may include a first screw twin and a second screw twin disposed within a casing and axially spaced apart from one another to define a central chamber therebetween, wherein the first screw twin is adapted to convey fluid from an inlet to the central chamber, and wherein the second screw twin is adapted to convey fluid from the central chamber to an outlet, and wherein a volumetric flow rate of the first screw twin is greater than a volumetric flow rate of the second screw twin.

[0007] A twin screw heating pump in accordance with another embodiment of the present disclosure may include a first screw twin and a second screw twin disposed within a casing and axially spaced apart from one another to define a central chamber therebetween, wherein the first screw twin and the second screw twin are adapted to convey fluid to the central chamber, and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin, wherein thesecond slip flow is greater than the first slip flow and conveys fluid from the central chamber to an outlet.

[0008] A twin screw heating pump in accordance with another embodiment of the present disclosure may include a first screw twin and a second screw twin disposed within a casing and axially spaced apart from one another to define a central chamber therebetween, and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin, wherein the first screw twin and a surrounding portion of the liner are conical and tapered from a first axial end to a second axial end, and wherein the first screw twin and the liner are axially movable relative to one another for varying a size of the first radial gap to adjust the first slip flow.

[0009] A twin screw heating pump system in accordance with an embodiment of the present disclosure may include a first twin screw pump adapted to convey fluid from an inlet of the first twin screw pump to an outlet of the first twin screw heating pump, and a second twin screw pump adapted to convey fluid from an inlet of the second twin screw pump to an outlet of the second twin screw pump, wherein the outlet of the first twin screw pump is coupled to the inlet of the second twin screw pump, and wherein a volumetric flow rate of the first twin screw pump is greater than a volumetric flow rate of the second twin screw pump.

[0010] A twin screw heating pump system in accordance with another embodiment of the present disclosure may include a first twin screw pump adapted toconvey fluid from an inlet of the first twin screw pump to an outlet of the first twin screw pump, and a second twin screw pump adapted to convey fluid toward an inlet of the second twin screw pump, wherein the outlet of the first twin screw pump is coupled to the inlet of the second twin screw pump by a fluid line, the first twin screw pump having a slip flow that conveys fluid from a central chamber of first twin screw pump to an inlet of the first twin screw pump, and the second twin screw pump having a slip flow that conveys fluid from a central chamber of second twin screw pump to an outlet of the second twin screw pump, wherein the slip flow in the second twin screw pump is greater than the slip flow in the first twin screw pump.Brief Description of the Drawings

[0011] By way of example, various embodiments of the disclosed techniques will now be described with reference to the accompanying drawings, wherein:

[0012] FIGS. 1A is a longitudinal cross-sectional view illustrating a twin screw heating pump in accordance with an embodiment of the present disclosure;

[0013] FIGS. IB is a longitudinal cross-sectional view illustrating an alternative embodiment of the twin screw heating pump shown in FIG. 1A;

[0014] FIG. 2 is a longitudinal cross-sectional view illustrating another twin screw heating pump in accordance with an embodiment of the present disclosure;

[0015] FIGS. 3 is a longitudinal cross-sectional view illustrating a twin screw heating pump in accordance with another embodiment of the present disclosure;

[0016] FIGS. 4 is a longitudinal cross-sectional view illustrating a twin screw heating pump in accordance with another embodiment of the present disclosure;

[0017] FIG. 5A is a perspective view illustrating a twin screw heating pump system in accordance with an embodiment of the present disclosure;

[0018] FIG. 5B is a longitudinal cross-sectional view illustrating the twin screw heating pump system of FIG. 5A;

[0019] FIG. 5C is a perspective view illustrating an alternative embodiment of the twin screw heating pump system shown in FIG. 5A;

[0020] FIG. 6A is a perspective view illustrating another twin screw heating pump system in accordance with an embodiment of the present disclosure;

[0021] FIG. 6B is a longitudinal cross-sectional view illustrating the twin screw heating pump system of FIG. 6A;

[0022] FIG. 7 is a perspective view illustrating another twin screw heating pump system in accordance with an embodiment of the present disclosure.Detailed Description

[0023] The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, wherein some exemplary embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and are not to be construed as limited to the embodiments set forth herein. These embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.

[0024] As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” are understood as possibly including plural elementsor operations, except as otherwise indicated. Furthermore, various embodiments herein have been described in the context of one or more elements or components. An element or component may comprise any structure arranged to perform certain operations. Although an embodiment may be described with a limited number of elements in a certain topology by way of example, the embodiment may include more or less elements in alternate topologies as desired for a given implementation. Note any reference to “one embodiment” or “an embodiment” means a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrases “in one embodiment,” “in some embodiments,” and “in various embodiments” in various places in the specification are not necessarily all referring to the same embodiment.

[0025] Single Pump Heating: Concept 1

[0026] Referring to FIG. 1A, a longitudinal cross-sectional view illustrating a twin screw heating pump 100 (hereinafter “the pump 100”) in accordance with an embodiment of the present disclosure is shown. For the sake of convenience and clarity, terms such as “axial,” “radial,” “inner,” “outer,” “lateral,” and “longitudinal,” may be used herein to describe the relative positions and orientations of various structures and features of the pump 100, all with respect to the geometry and orientation of the pump 100 as it appears in FIG. 1A. Said terminology is not intended to be limiting and includes the words specifically mentioned, derivatives thereof, and words of similar import.

[0027] The pump 100 may include first and second rotors 102, 104 that may be rotatably fixed within a housing or casing 106 (hereinafter “the casing 106”). The first and second rotors 102, 104 may have respective first and second shafts 108, 110 with axially spaced-apart first and second screw threads 112a, 112b and 114a, 114b extending radially therefrom, respectively. The first screw thread 112a of the first rotor 104 and the first screw thread 114a of the second rotor 104, collectively referred to herein as a first screw twin 116, may be intermeshed and may define a first plurality of rotor chambers 118 within the casing 106. Similarly, the second screw thread 112b of the first rotor 104 and the second screw thread 114b of the second rotor 104, collectively referred to herein as a second screw twin 120, may be intermeshed and may define a second plurality of rotor chambers 122 within the casing 106. The shaft 108 of the first rotor 102 may extend out of the casing 106 and may be coupled to a motor 124 as schematically shown in FIG. 1A. A first gear 126 on the first shaft 108 may engage a second gear 128 on the second shaft 110, such that when the first shaft 108 is rotatably driven by the motor 124 the second shaft 110 is rotated at the same rate but in an opposite direction. The first and second screw threads 112a, 112b and 114a, 114b may be configured (e.g., angled) such that the first and second screw twins 116, 120 convey fluid in the same direction (from left to right in FIG. 1A) as further described below.

[0028] In addition, the casing 106 may include a replaceable liner 130 that is arranged and configured to surround the first and second rotors 102, 104 (e g., the liner136 is arranged and configured as a separate component which is installed in the casing 106). The liner 130 may be supported and sealed against the inner surfaces of the casing 106. The first and second screw twins 116, 120 do not radially engage the liner 136because the first and second rotors 102, 104 must be allowed to rotate freely without interference from the liner 136. There are therefore first and second radial gaps 132, 134 between the first screw twin 116 and the liner 130 and between the second screw twin 120 and the liner 130, respectively. Therefore, some slip flow will occur, allowing a certain amount of fluid to flow back through the first and second radial gaps 132, 134, driven by differential pressure over the first and second screw-twins 116, 120 as further described below. The volumetric flow rates of the slip flows around the first and second screw-twins 116, 120 are indicated by Si and S2 in FIG. 1A, respectively (hereinafter “the first slip flow Si” and “the second slip flow S2”). Slip flow resistances around the first and second screw-twins 116, 120 are indicated by Ri and R2 in FIG. 1, respectively (hereinafter “the first slip flow resistance Ri” and “the second slip flow resistance R2”). Generally, the smaller the first and second radial gaps 132, 134 the greater the first and second slip flow resistances Ri and R2, respectively. Of course, slip flow resistances are also affected by fluid viscosity as further discussed below.

[0029] During operation, fluid is drawn into the pump 100 at an inlet 136. Fluid pressure at the inlet 136 is indicated by Pin in FIG. 1A. As the first and second rotors 102, 104 are turned by the motor 124, the fluid is entrapped within the first plurality of rotor chambers 118 of the first screw twin 116, which convey the fluid longitudinally from the inlet 136 to a central chamber 138 axially intermediate the first screw twin 116 and the second screw twin 120 where the first and second shafts 108, 110 are exposed and are not threaded. The volumetric flow rate through the first screw twin 116 is indicated by Q01 in FIG. 1A. The fluid is then collected from the central chamber 138 by the second plurality of rotor chambers 122 of the second screw twin 120, which conveythe fluid longitudinally from the central chamber 138 to an outlet 140 where the fluid is ultimately expelled from the pump 100. The volumetric flow rate through the second screw twin 120 is indicated by Q02 in FIG. 1A, and fluid pressure at the outlet 140 is indicated by Pout in FIG. 1A. The total volumetric flow rate into / out of the pump 100 is indicated by QpUmp in FIG. 1A.

[0030] The volumetric flow rate Q01 of the first screw twin 116 may be greater than the volumetric flow rate Q02 of the second screw twin 120, which may be achieved by providing the threads of the second screw twin 120 with a pitch that is smaller than the pitch of the threads of the first screw twin 116 (as shown in FIG. 1A) or by otherwise reducing / varying the dimensions of the second screw twin 120 relative to those of the first screw twin 116. Thus, due to this difference in volumetric flow rates, the second screw twin 120 blocks part of the flow coming from the first screw twin 116, consequently increasing the fluid pressure in the central chamber 138 (such pressure indicated by Pcenter in FIG. 1A) until the total slip flow around the first and second screw twins 116, 120 (given by Si + S2) compensates the difference in the volumetric flow rates (i.e., Si + S2 ~ Q01 - Q02).

[0031] Hydraulic and mechanical energy imparted by the first screw twin 116 pressurizes and heats the fluid in the central chamber 138, and the second screw twin 120 actively pulls the heated fluid out of the central chamber 138 and ejects the fluid through the outlet 140. The first screw twin 1 16 thus acts as a heating booster, while the second screw twin 120 acts as a flow control. Thus, increasing the speed of the pump 100 (via the motor 124) will result in a higher total volumetric flow rate QpUmp as dictated by the volumetric flow rate Q02 through the second screw twin 120. Increasing the speed of thepump 100 will also increase the hydraulic power imparted to the fluid, thereby increasing the pressure Pcenter, which in-turn increases the energy of the fluid. The difference between Qoi and Q02 forces the surplus fluid through the first and second radial gaps 132, 134, reducing the fluid pressure and converting the hydraulic energy into thermal energy, heating the fluid.

[0032] More generally, the above-described pump 100 can be characterized by the following equations:

[0033] Pcenter - S i * R1 = S2* R2

[0034] Q pump—QO2 + S2

[0035] Pump power = Qoi * (Pcenter - Pin) - Q02 * (Pcenter “ Pout)

[0036] In various embodiments, the pump 100 may further include means for allowing fluid from the central chamber 138 to bypass the second screw twin 120. For example, referring to FIG. IB, an embodiment of the pump 100 is shown that includes a bypass line 150 extending from the central chamber 138 directly to the outlet 140, wherein the bypass line 150 includes a bypass valve 152. By controlling the bypass valve 150 (i.e., controlling the degree to which the bypass valve is opened), the pressure Pcenter can be regulated, which in-tum regulates the energy of the fluid. For example, if the bypass valve 152 is completely opened, the fluid in the central chamber 138 may freely bypass the second screw twin 120 via the bypass line 150. Thus, the second screw twin 120 will not restrict any of the flow exiting the central chamber 138, resulting in little or no increase in the fluid pressure in the central chamber 138 and therefore little or no heating of the fluid. Alternatively, if the bypass valve 152 is partially closed, the flowrate through the bypass line 150 may be reduced (i.e., relative to the bypass valve 152 being completely opened), thereby causing an increase in the pressure Pcenter, which in- tum increases the energy / temperature of the fluid. Of course, if the bypass valve 152 is completely closed, no fluid will exit the central chamber 138 via the bypass line 150 and the pump 100 will operate in the same manner as described above with respect to FIG.1A

[0037] Single Pump Heating: Concept 2

[0038] Referring to FIG. 2, a longitudinal cross-sectional view illustrating a twin screw heating pump 200 (hereinafter “the pump 100”) in accordance with another embodiment of the present disclosure is shown. For the sake of convenience and clarity, terms such as “axial,” “radial,” “inner,” “outer,” “lateral,” and “longitudinal,” may be used herein to describe the relative positions and orientations of various structures and features of the pump 200, all with respect to the geometry and orientation of the pump 200 as it appears in FIG. 2. Said terminology is not intended to be limiting and includes the words specifically mentioned, derivatives thereof, and words of similar import.

[0039] The pump 200 may include first and second rotors 202, 204 that may be rotatably fixed within a housing or casing 206 (hereinafter “the casing 206”). The first and second rotors 202, 204 may have respective first and second shafts 208, 210 with axially spaced-apart first and second screw threads 212a, 212b and 214a, 214b extending radially therefrom, respectively. The first screw thread 212a of the first rotor 204 and the first screw thread 214a of the second rotor 204, collectively referred to herein as a first screw twin 216, may be intermeshed and may define a first plurality of rotor chambers 218 within the casing 206. Similarly, the second screw thread 212b of the first rotor 204and the second screw thread 214b of the second rotor 204, collectively referred to herein as a second screw twin 220, may be intermeshed and may define a second plurality of rotor chambers 222 within the casing 206. The shaft 208 of the first rotor 202 may extend out of the casing 206 and may be coupled to a motor 224 as schematically shown in FIG. 2. A first gear 226 on the first shaft 208 may engage a second gear 228 on the second shaft 210, such that when the first shaft 208 is rotatably driven by the motor 224 the second shaft 210 is rotated at the same rate but in an opposite direction. The first and second screw threads 212a, 212b and 214a, 214a may be configured (e.g., angled) such that the first and second screw twins 216, 220 convey fluid in opposite directions. Specifically, the first screw twin 216 may convey fluid from left-to-right in FIG. 2, and the second screw twin 220 may convey fluid from right-to-left in FIG. 2 as further described below.

[0040] In addition, the casing 206 may include a replaceable liner 230 that is arranged and configured to surround the first and second rotors 202, 204 (e g., the liner 230 is arranged and configured as a separate component which is installed in the casing 206). The liner 230 may be supported and sealed against the inner surfaces of the casing 206. The first and second screw twins 216, 220 do not radially engage the liner 230 because the first and second rotors 202, 204 must be allowed to rotate freely without interference from the liner 230. There are therefore first and second radial gaps 232, 234 between the first screw twin 216 and the liner 230 and between the second screw twin 220 and the liner 230, respectively. Therefore, some slip flow will occur, allowing a certain amount of fluid to flow back through the first and second radial gaps 232, 234, driven by differential pressure over first and second screw-twins 216, 220 as furtherdescribed below. The volumetric flow rates of the slip flows around the first and second screw-twins 216, 220 are indicated by Si and S2 in FIG. 2, respectively (hereinafter “the first slip flow Si” and “the second slip flow S2”). Slip flow resistances around the first and second screw -twins 216, 220 are indicated by Ri and R2 in FIG. 2, respectively (hereinafter “the first slip flow resistance Ri” and “the second slip flow resistance R2”). Generally, the smaller the first and second radial gaps 232, 234 the greater the first and second slip flow resistances Ri and R2, respectively. Of course, slip flow resistances are also affected by fluid viscosity as further discussed below.

[0041] During operation, fluid is drawn into the pump 200 at an inlet 236. Fluid pressure at the inlet 236 is indicated by Pm in FIG. 2. As the first and second rotors 202, 204 are turned by the motor 224, the fluid is entrapped within the first plurality of rotor chambers 218 of the first screw twin 216, which convey the fluid longitudinally from the inlet 236 to a central chamber 238 axially intermediate the first screw twin 216 and the second screw twin 220 where the first and second shafts 208, 210 are exposed and are not threaded. The volumetric flow rate through the first screw twin 216 is indicated by Q01 in FIG. 2. The second screw twin 220, which conveys fluid in the opposite direction of the first screw twin 216 as described above, also drives the fluid toward the central chamber 238. The volumetric flow rate through the second screw twin 220 is indicated by Q02 in FIG. 2. Hydraulic and mechanical energy imparted by both the first and second screw twins 216, 220 pressurizes the fluid in the central chamber 238. Fluid pressure in the central chamber 238 is indicated by Pcentcr in FIG. 2. As Pccntcr increases and becomes sufficient to overcome the first slip flow resistance Ri and the second slip flow resistanceR2, the fluid may be forced out of the central chamber 238 via the first and second slipflows Si, S2. The second slip flow S2 around the second screw twin 220 may be greater than the first slip flow Si around the first screw twin 216, which may be achieved by making the second radial gap 234 larger than the first radial gap 232, for example. Thus, due to this difference in the slip flows Si, S2, most of the fluid will be conveyed by the second slip flow S2to an outlet 240 where the fluid is ultimately expelled from the pump 200 (a certain amount of fluid will be conveyed by the first slip flow Si back to the inlet 236 where it will be recirculated through the pump 200). The fluid pressure at the outlet 240 is indicated by Pout in FIG. 2. The total volumetric flow rate into / out of the pump 200 is indicated by QpUmp in FIG. 2.

[0042] Increasing the speed of the pump 200 (via the motor 224) will increase the hydraulic power imparted to the fluid, thereby increasing the pressure Pcenter, which in- tum increases the hydraulic energy of the fluid. An increase in Pcenter results in an increase in the first and second slip flows Si, S2, which consequently leads to a higher pump flow rate. At lower speed, less hydraulic energy is introduced, resulting in a lower Pcenter and reduced first and second slip flows Si, S2. As fluid flows from the central chamber 238 to the inlet 236 and the outlet 240, the hydraulic energy is converted into thermal energy and the fluid is heated.

[0043] More generally, the above-described pump 200 can be characterized by the following equations:

[0044] Pcenter ~ Si * R1 = S2* R2

[0045] Q pump Qoi Si - S2- QO2

[0046] Pump heating power = Qoi * (Pcenter - Pin) + Qo2* (Pcenter - Pout)

[0047] Single Pump Heating; Concept 3

[0048] In both of the pumps 100, 200 described above, it may sometimes be desirable to dynamically adjust one or both of the slip flow resistances Ri and R2 to facilitate greater control over pump capacity and fluid heating. This may be achieved by making one or both of the first and second screw twins 116, 120 and the surrounding portions of the liner 130 conical and making the first and second screw twins 116, 120 and the liner 130 axially movable relative to one another. For example, referring to FIG. 3, a modified version of the above-described pump 100 is shown wherein the first screw twin 116 and a surrounding portion of the liner 130 are conical, tapering from a first end axially adjacent the central chamber 138 to a second end axially adjacent the inlet 136. That is, the first screw twin 116 and the surrounding portion of the liner 130 may have largest diameters at the first end and smallest diameters at the second end. In various embodiments, the first screw twin 116 and the surrounding portion of the liner 130 may be tapered at an angle in a range of 0.001 degrees to 45 degrees relative to longitudinal axes of the first and second shafts 108, 110. In certain embodiments, the first screw twin 116 and the surrounding portion of the liner 130 may be tapered at an angle in a range of 1 degree to 30 degrees relative to longitudinal axes of the first and second shafts 108, 110. The present disclosure is not limited in this regard. The second screw twin 120 and the surrounding portion of the liner 130 may have consistent diameters (i.e., identical to the embodiment of the pump 100 shown in FIG. 1A).

[0049] The axial positions of the first and second rotors 102, 104 and the first and second screw twins 116, 120 relative to the liner 130 may be adjusted in a conventional manner by adjusting the axial alignment of thrust bearing positions within the pump 100.Alternatively, the liner 130 can be moved axially, such as may be achieved by the repositioning of set screws during maintenance of the pump 100 or via dynamic positioning during operation of the pump 100. The present disclosure is not limited in this regard.

[0050] If greater heating power is required, the axial positions of the first and second screw twins 116, 120 may be shifted leftward relative to the liner 130, toward the inlet 136, thereby decreasing the size of the first radial gap 132, which in-turn decreases the first slip flow Si and increases the pressure Pcenter. If less heating power is required, the axial positions of the first and second screw twins 116, 120 may be shifted rightward relative to the liner 130, toward the outlet 140, thereby increasing the size of the first radial gap 132, which in-turn increases the first slip flow Si and decreases the pressure Pcenter. The size of the of the second radial gap 134 may remain constant throughout such adjustments.

[0051] In the embodiment shown in FIG. 3, only the first screw twin 116 and the surrounding portion of the liner 130 are conical, which facilitates the adjustment of heating power as described above. However, alternative embodiments of the pump 100 are contemplated in which both the first and second screw twins 116, 120 and the surrounding portions of the liner 130 are conical, thereby facilitating adjustment of both heating power and fluid flow. Such configurations may require more complex liner configurations (e.g., a two-piece liner). Further embodiments are contemplated in which only the second screw twin 120 and the surrounding portion of the liner 130 are conical (i.e., the first screw twin 116 and the surrounding portion of the liner 130 have consistent diameters), thus enabling adjustment of fluid flow but not heating power. Additionally,while the first screw twin 116 and the surrounding portion of the liner 130 are shown in FIG. 3 as decreasing in diameter from right-to-left, further embodiments are contemplated in which the first screw twin 116 and the surrounding portion of the liner 130 decrease in diameter from left-to-right. Similarly, in embodiments in which the second screw twin 120 and the surrounding portion of the liner 130 are additionally or alternatively made conical, the second screw twin 120 and the surrounding portion of the liner 130 may taper from right-to-left or left-to-right. Still further, the diameter of the first screw twin 116 (whether uniform or tapered) may be the same as, or may differ from, the diameter of the second screw twin 120. The present disclosure is not limited in this regard.

[0052] In any of the above-described Single Pump Heating Concepts 1-3, a pressure control device may be implemented to facilitate external regulation of Pcenter. For example, referring to FIG. 4, a variation of the pump 100 is shown that includes a pressure control device 150 coupled to the pump 100 in fluid communication with the central chamber 138. The pressure control device 150 may be a simple valve or any other type of pressure regulation device or flow control device adapted to controllably release fluid from the central chamber 138. By operating the pressure control device 150, Pcenter can be externally controlled to vary the flow of fluid through the pump 100 and the amount of energy imparted to the fluid in the pump 100. For example, if the pressure control device 150 is opened and fluid is allowed to escape from the central chamber 138, Pcenter will decrease, in-tum causing the temperature of the fluid to decrease. In some embodiments, the pressure control device 150 may be operated as a pressure safety valve, wherein the pressure control device 150 may be opened if Pcenter exceeds a predeterminedsafety threshold. The present disclosure is not limited in this regard.

[0053] Two-Pump Heating: Concept 1

[0054] The same general concepts for achieving fluid heating and flow control in the pumps 100, 200 described above can also be implemented using multiple pumps. Such multiple-pump configurations may be preferable for facilitating better independent control of heating and flow as well as for achieving higher levels of heating relative to the single-pump configurations described above. For example, referring to FIGS. 5A and 5B, an external view and a schematic cross-sectional view illustrating a two-pump system 300 (hereinafter “the system 300”) are shown. For the sake of convenience and clarity, terms such as “axial,” “radial,” “inner,” “outer,” “lateral,” and “longitudinal,” may be used herein to describe the relative positions and orientations of various structures and features of the system 300, all with respect to the geometry and orientation of the system 300 as it appears in FIG. 5B. Said terminology is not intended to be limiting and includes the words specifically mentioned, derivatives thereof, and words of similar import.

[0055] The system 300 may be conceptually analogous to the pump 100 described above, with the first screw twin 116 of the pump 100 being replaced by a first pump 400 and the second screw twin 120 of the pump 100 being replaced by a separate, second pump 500. Each of the first and second pumps 400, 500 may be an independently driven, independently controllable twin screw pump having first and second screw twins 416, 420 and 516, 520 as further described below. The first pump 400 may receive unheated fluid via split inlets 436a, 436b (externally appearing as a single inlet 436 inFIG. 5A) at opposing longitudinal ends of the first and second screw twins 416, 420. The first and second screw twins 416, 420 may be configured (e.g., their threads may be angled) such that they convey fluid in opposite directions, longitudinally from the inlets 436a, 436b to a central chamber 438 intermediate the first and second screw twins 416, 420, where the fluid is ultimately expelled from the pump 400 through outlet 440. Fluid pressures at the inlets 436a, 436b (which are equal) are indicated by Pin in FIG. 5B. The volumetric flow rate in the first pump 400 is indicated by Qoi in FIG. 5B. Slip flow rates around the first and second screw twins 416, 420 (which are equal) are indicated by Si in FIG. 5B. Slip flow resistances around the first and second screw-twins 416, 420 (which are equal) are indicated by Ri in FIG. 5B.

[0056] The outlet 440 of the first pump 400 may be coupled to an inlet 536 of the second pump 500 by a fluid line 537 (e.g., a pipe, tube, etc.). The fluid may enter the second pump 500 at a central chamber 538 intermediate the first and second screw twins 516, 520. The first and second screw twins 516, 520 may be configured (e.g., their threads may be angled) such that they convey fluid in opposite directions, longitudinally from the central chamber 438 to split outlets 540a, 540b (externally appearing as a single outlet 540 in FIG. 5A) at opposing longitudinal ends of the first and second screw twins 516, 520, where the fluid is ultimately expelled from the pump 500. The volumetric flow rate in the second pump 500 is indicated by Q02 in FIG. 5B. Slip flow rates around the first and second screw twins 516, 520 (which are equal) are indicated by S2 in FIG. 5B. Slip flow resistances around the first and second screw-twins 516, 520 (which are equal) are indicated by R2 in FIG. 5B. Fluid pressures at the outlets 536a, 536b (which are equal) are indicated by Pout in FIG. 5B.

[0057] The volumetric flow rate Qoi in the first pump 400 may be greater than the volumetric flow rate Q02 in the second pump 500. Due to this difference in volumetric flow rates, the second pump 500 blocks part of the flow coming from the first pump 400, consequently increasing the fluid pressure in the fluid line 537 between the first and second pumps 400, 500 (such pressure indicated by Pcenter in FIG. 5B). The total volumetric flow rate through the first and second pumps 400, 500 is indicated by Qpi&2in FIG. 5B. Hydraulic and mechanical energy imparted by the first pump 400 pressurizes and heats the fluid between the first and second pumps 400, 500, and the second pump 500 actively pulls the heated fluid from between the first and second pumps 400, 500 and ejects the fluid through the outlets 536a, 536b. The first pump 400 thus acts as a heating booster, while the second pump 500 acts as a flow control. Thus, increasing the speed of the first pump 400 (via the motor 424) will result in greater heating of the fluid, while increasing the increasing the speed of the second pump 500 (via the motor 524) will result in greater flow through the system 300.

[0058] More generally, the above-described system 300 can be characterized by the following equations:

[0059] P center S1 * R1 = S2* R2

[0060] QPI&2 = Q02 + S2 QO2 + P center / R2

[0061] Pump power = QOI * (Pcenter - Pin) “ Qo2 * (Pcenter “ Pout)

[0062] In various embodiments, the system 300 may further include means for allowing fluid from the fluid line 537 to bypass the second pump 500. For example, referring to FIG. 5C, an embodiment of the system 300 is shown that includes a bypassline 550 extending from the fluid line 537 directly to the outlet 540 of the second pump 500, wherein the bypass line 550 includes a bypass valve 552. By controlling the bypass valve 552 (i.e., controlling the degree to which the bypass valve is opened), the pressure Pcenter in the fluid line can be regulated, which in-tum regulates the energy of the fluid. For example, if the bypass valve 552 is completely opened, the fluid in the fluid line 537 may freely bypass the second pump 500 via the bypass line 550. Thus, the second pump 500 will not restrict any of the flow in the fluid line 537, resulting in little or no increase in the fluid pressure in the fluid line 537 and therefore little or no heating of the fluid. Alternatively, if the bypass valve 552 is partially closed, the flow rate through the bypass line 550 may be reduced (i.e., relative to the bypass valve 552 being completely opened), thereby causing an increase in the pressure Pcenter in the fluid line 537, which in-tum increases the energy / temperature of the fluid. Of course, if the bypass valve 152 is completely closed, no fluid will exit the fluid line 537 via the bypass line 550 and the system 300 will operate in the same manner as described above with respect to FIGS. 5A and 5B.

[0063] Two-Pump Heating; Concept 2

[0064] Referring to FIGS. 6A and 6B, an external view and a schematic cross- sectional view illustrating another two-pump system 600 (hereinafter “the system 600”) are shown. For the sake of convenience and clarity, terms such as “axial,” “radial,” “inner,” “outer,” “lateral,” and “longitudinal,” may be used herein to describe the relative positions and orientations of various structures and features of the system 600, all with respect to the geometry and orientation of the system 600 as it appears in FIG. 6B. Saidterminology is not intended to be limiting and includes the words specifically mentioned, derivatives thereof, and words of similar import.

[0065] The system 600 may be conceptually analogous to the pump 200 described above, with the first screw twin 216 of the pump 200 being replaced by a first pump 700 and the second screw twin 220 of the pump 200 being replaced by a separate, second pump 800. Each of the first and second pumps 700, 800 may be an independently driven, independently controllable twin screw pump having first and second screw twins 716, 720 and 816, 820 as further described below. The first pump 700 may receive unheated fluid via split inlets 736a, 736b (externally appearing as a single inlet 736 as shown in FIG. 6A) at opposing longitudinal ends of the first and second screw twins 716, 720. The first and second screw twins 716, 720 may be configured (e.g., their threads may be angled) such that they convey fluid in opposite directions, longitudinally from the inlets 736a, 736b to a central chamber 738 intermediate the first and second screw twins 716, 720, where the fluid is ultimately expelled from the pump 700 through outlet 740. Fluid pressures at the inlets 736a, 736b (which are equal) are indicated by Pin in FIG. 6B. The volumetric flow rate in the first pump 700 is indicated by Qoi in FIG. 6B. Slip flow rates around the first and second screw twins 716, 720 (which are equal) are indicated by Si in FIG. 6B (hereinafter “the first slip flow Si”). Slip flow resistances around the first and second screw-twins 716, 720 (which are equal or nearly equal) are indicated by Ri in FIG. 6B

[0066] The outlet 740 of the first pump 700 may be coupled to an inlet 836 of the second pump 800, where the fluid enters a central chamber 838 intermediate the first and second screw twins 816, 820 of the second pump 800. The first and second screw twins516, 520 may be configured (e.g., their threads may be angled) such that they convey fluid in opposite directions, longitudinally toward the central chamber 438. Fluid may escape from the central chamber via slips flows around the first and second screw twins 816, 820 and may be channeled to split outlets 840a, 840b (externally appearing as a single outlet 840 as shown in FIG. 6A) at opposing longitudinal ends of the first and second screw twins 816, 820, where the fluid is ultimately expelled from the pump 800. The volumetric flow rate in the second pump 800 is indicated by Q02 in FIG. 6B. Slip flow rates around the first and second screw twins 816, 820 (which are equal) are indicated by S2 in FIG. 6B (hereinafter “the second slip flow S2”). Slip flow resistances around the first and second screw -twins 816, 820 (which are equal or nearly equal) are indicated by R2 in FIG. 6B. Fluid pressures at the outlets 836a, 836b (which are equal) are indicated by Pout in FIG. 6B.

[0067] Thus, the first and second pumps 700, 800 pump against one another, and hydraulic and mechanical energy imparted by both the first and second pumps 700, 800 pressurizes and heats the fluid between the first and second pumps 700, 800. Fluid pressure between the first and second pumps 700, 800 is indicated by Pcenter in FIG. 6B The second slip flow S2 in the second pump 800 may be greater than the first slip flow Si in the first pump 700, which may be achieved by making the radial gaps around the first and second screw twins 816, 820 of the second pump 800 larger than the radial gaps around the first and second screw twins 716, 720 of the first pump 700, for example. Due to this difference in the slip flows Si, S2, most of the heated fluid will be conveyed by the second slip flow S2 to the outlets 840a, 840b where the fluid is ultimately expelled from the pump 800 (a small amount of heated fluid will be conveyed by the first slip flow Siback to the inlets 736 of the first pump 700 where it will be recirculated through the first pump 700). The total volumetric flow rate through the first and second pumps 700, 800 is indicated by QPI&2 in FIG. 6B.

[0068] Again, the first and second pumps 700, 800 pump against each other to provide as much hydraulic power (and therefore heating) as possible while the capacity- slip-flow-balance (Qoi + Q02 = S2 + SI and S2 > Q02) will set the overall flow rate in the system 600. Because S2 > Q02 and Qoi > Si, the first pump 700 pushes flow through the second pump 800 (Qoi - Si > S2 - Q02). By increasing the pump speed the second pump 800 may increase Pcenter which increases the total slip flow (S2 + Si) in the system 600. At the same time, the second pump 800 reduces the overall flow rate by pumping a higher percentage of its slip (S2) backwards. The shaft power of both pumps 700, 800 together is used to heat the fluid as controlled by the combined speeds of both the first and second pumps 700, 800. More generally, the above-described system can be characterized by the following equations:

[0069] Pcenter - Si * R1 = S2* R2

[0070] QPI&2 ~ Qoi - Si = S2 - Q02

[0071] Pump heating power = QOI * (Pcenter - Pin) - Q02 *(Pcenter - Pout)

[0072] In either of the above-described Two-Pump Heating Concepts 1 and 2, a pressure control device may be implemented to facilitate external regulation of Pcenter. For example, referring to FIG. 7, a variation of the system 300 is shown that includes a pressure control device 450 coupled to the fluid line 537 intermediate the first pump 400 and the second pump 500. The pressure control device 450 may be a simple valve or anyother type of pressure regulation device or flow control device adapted to controllably constrict the fluid line 537. By operating the pressure control device 450, Pcentercan be externally controlled to vary the flow of fluid through the system 300 and the amount of energy imparted to the fluid in the system 300. For example, if the pressure control device 450 is opened and fluid is allowed to escape from the fluid line 537, Pinter will decrease, in-tum causing the temperature of the fluid to decrease. In some embodiments, the pressure control device 450 may be operated as a pressure safety valve, wherein the pressure control device 450 may be opened if Pcenter exceeds a predetermined safety threshold. The present disclosure is not limited in this regard.

[0073] The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Furthermore, while the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize its usefulness is not limited thereto. Embodiments of the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below shall be construed in view of the full breadth and spirit of the present disclosure as described herein.

Claims

Claims1. A twin screw heating pump comprising: a first screw twin and a second screw twin disposed within a casing and axially spaced apart from one another to define a central chamber therebetween; wherein the first screw twin is adapted to convey fluid from an inlet to the central chamber, and wherein the second screw twin is adapted to convey fluid from the central chamber to an outlet; and wherein a volumetric flow rate of the first screw twin is greater than a volumetric flow rate of the second screw twin.

2. The twin screw heating pump of claim 1, further comprising a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin.

3. The twin screw heating pump of claim 1, wherein threads of the second screw twin have a pitch that is smaller than a pitch of threads of the first screw twin.

4. The twin screw heating pump of claim 1, further comprising a pressure control device in fluid communication with the central chamber and adapted to controllably release fluid from the central chamber.

5. The twin screw heating pump of claim 4, wherein the pressure control device is a valve located outside of the casing.

6. The twin screw heating pump of claim 1, further comprising a bypass line extending from the central chamber to the outlet, the bypass line including a bypass valve for controllably restricting fluid flow in the bypass line.

7. A twin screw heating pump comprising: a first screw twin and a second screw twin disposed within a casing and axially spaced apart from one another to define a central chamber therebetween, wherein the first screw twin and the second screw twin are adapted to convey fluid to the central chamber; and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin, wherein the second slip flow is greater than the first slip flow and conveys fluid from the central chamber to an outlet.

8. The twin screw heating pump of claim 7, wherein the second radial gap is larger than the first radial gap.

9. The twin screw heating pump of claim 7, further comprising a pressure control device in fluid communication with the central chamber and adapted to controllably release fluid from the central chamber.

10. The twin screw heating pump of claim 9, wherein the pressure control device is a valve located outside of the casing.

11. The twin screw heating pump of claim 7, further comprising a bypass line extending from the central chamber to the outlet, the bypass line including a bypass valve for controllably restricting fluid flow in the bypass line.

12. A twin screw heating pump comprising: a first screw twin and a second screw twin disposed within a casing and axially spaced apart from one another to define a central chamber therebetween; and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the firstscrew twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin; wherein the first screw twin and a surrounding portion of the liner are conical and taper from a first axial end to a second axial end; and wherein the first screw twin and the liner are axially movable relative to one another for varying a size of the first radial gap to adjust the first slip flow.

13. The twin screw heating pump of claim 12, wherein the first screw twin and the surrounding portion of the liner are tapered at an angle in a range of 0.001 degrees to 45 degrees relative to a longitudinal axis of a shaft of the twin screw heating pump.

14. The twin screw heating pump of claim 12, wherein the second screw twin and a surrounding portion of the liner are conical and taper from a first axial end to a second axial end, and wherein axially moving the second screw twin and the surrounding portion of the liner relative to one another varies a size of the second radial gap to adjust the second slip flow.

15. The twin screw heating pump of claim 14, wherein the second screw twin and the surrounding portion of the liner are tapered at an angle in a range of 0.001 degrees to 45 degrees relative to a longitudinal axis of a shaft of the twin screw heating pump.

16. The twin screw heating pump of claim 12, wherein the first screw twin and the second screw twin are adapted to convey fluid in the same direction.

17. The twin screw heating pump of claim 12, wherein the first screw twin and the second screw twin are adapted to convey fluid in opposing directions, toward one another.

18. The twin screw heating pump of claim 12, further comprising a bypass line extending from the central chamber to the outlet, the bypass line including a bypass valve for controllably restricting fluid flow in the bypass line.

19. A twin screw heating pump system comprising: a first twin screw pump adapted to convey fluid from an inlet of the first twin screw pump to an outlet of the first twin screw pump; and a second twin screw pump adapted to convey fluid from an inlet of the second twin screw pump to an outlet of the second twin screw pump; wherein the outlet of the first twin screw pump is coupled to the inlet of the second twin screw pump by a fluid line, and wherein a volumetric flow rate of the first twin screw pump is greater than a volumetric flow rate of the second twin screw pump.

20. The twin screw heating pump system of claim 19, further comprising a pressure control device in fluid communication with the fluid line and adapted to controllably release fluid from the fluid line.

21. The twin screw heating pump system of claim 19, wherein: the first twin screw pump comprises a first screw twin and a second screw twin disposed within a casing, and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin, wherein the second slip flow is equal to the first slip flow; and wherein the second twin screw pump comprises a first screw twin and a second screw twin disposed within a casing, and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin, wherein the second slip flow is equal to the first slip flow.

22. The twin screw heating pump system of claim 19, further comprising a bypass line extending from the fluid line to the outlet of the second twin screw pump, the bypass line including a bypass valve for controllably restricting fluid flow in the bypass line.

23. A twin screw heating pump system comprising: a first twin screw pump adapted to convey fluid from an inlet of the first twin screw pump to an outlet of the first twin screw pump; and a second twin screw pump adapted to convey fluid toward an inlet of the second twin screw pump; wherein the outlet of the first twin screw pump is coupled to the inlet of the second twin screw pump by a fluid line, the first twin screw pump having a slip flow that conveys fluid from a central chamber of first twin screw pump to an inlet of the first twin screw pump, and the second twin screw pump having a slip flow that conveys fluid from a central chamber of second twin screw pump to an outlet of the second twin screw pump, wherein the slip flow in the second twin screw pump is greater than the slip flow in the first twin screw pump.

24. The twin screw heating pump system of claim 23, further comprising a pressure control device in fluid communication with the fluid line and adapted to controllably release fluid from the fluid line.

25. The twin screw heating pump system of claim 23, wherein: the first twin screw pump comprises a first screw twin and a second screw twin disposed within a casing, and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gapbetween the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin, wherein the second slip flow is equal to the first slip flow; and wherein the second twin screw pump comprises a first screw twin and a second screw twin disposed within a casing, and a liner disposed within the casing between an inner surface of the casing and the first and second screw twins, wherein there is a first radial gap between the first screw twin and the liner for allowing a first slip flow around the first screw twin and there is a second radial gap between the second screw twin and the liner for allowing a second slip flow around the second screw twin, wherein the second slip flow is equal to the first slip flow.

26. The twin screw heating pump system of claim 23, further comprising a bypass line extending from the fluid line to the outlet of the second twin screw pump, the bypass line including a bypass valve for controllably restricting fluid flow in the bypass line.

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