Heat pump arrangement having a controllable heat exchanger and method for producing a heat pump arrangement
11852388 · 2023-12-26
Assignee
Inventors
Cpc classification
F25B30/06
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B2500/02
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B49/02
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B2500/29
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B2500/09
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B30/02
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
F25B30/06
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B30/02
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Abstract
A heat pump arrangement includes a heat pump device, an evaporator cycle interface for inputting liquid to be cooled into the heat pump device and for outputting cooled liquid out of the heat pump device, a condenser cycle interface for inputting liquid to be heated into the heat pump device and for outputting heated liquid out of the heat pump device, a controllable heat exchanger for controllably coupling the evaporator cycle interface and the condenser cycle interface, and a control for controlling the controllable heat exchanger in dependence on an evaporator cycle temperature in the evaporator cycle interface or a condenser cycle temperature in the condenser cycle interface.
Claims
1. A heat pump arrangement, comprising: a heat pump device; an evaporator cycle interface configured for inputting a liquid to be cooled into the heat pump device and configured for outputting a cooled liquid out of the heat pump device; a condenser cycle interface configured for inputting a liquid to be heated into the heat pump device and configured for outputting a heated liquid out of the heat pump device; a controllable heat exchanger configured for controllably coupling the evaporator cycle interface and the condenser cycle interface, the controllable heat exchanger comprising a controllable short circuit, wherein the controllable short circuit, when activated, is such that power requirements for the heat pump device are increased compared to power requirements in case of a deactivated controllable short circuit; and wherein a controller is configured: to activate cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger when a condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is lower than an evaporator cycle temperature as sensed by the evaporator cycle temperature sensor of the liquid to be cooled for a first temperature range, wherein the controllable short circuit is deactivated, to prevent cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger when the condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is higher than the evaporator cycle temperature as sensed by the evaporator cycle temperature sensor of the liquid to be cooled for a second temperature range, wherein the controllable short circuit is deactivated, and to activate the controllable short circuit of the controllable heat exchanger for a third temperature range, wherein the controllable heat exchanger, when the controllable short circuit of the controllable heat exchanger is activated, is configured to heat the liquid to be cooled in the evaporator cycle interface using the liquid to be heated in the condenser cycle interface or using the heated liquid in the condenser cycle interface, and wherein the first temperature range comprises first temperatures, wherein the second temperature range comprises second temperatures, and wherein the third temperature range comprises third temperatures, the second temperatures being higher than the first temperatures, and wherein the third temperatures being higher than the second temperatures.
2. Heat pump arrangement according to claim 1, wherein the controllable heat exchanger comprises a heat exchanger unit with four terminals and two fluidically separated paths and at least one control element fluidically coupled to the evaporator cycle interface, wherein the at least one control element fluidically coupled to the evaporator cycle interface is configured as a two-way switch or a mixer, wherein the two-way switch is configured as a passive two-way switch in order to effect or prevent the flow through one path of the two fluidically separated paths of the heat exchanger unit in dependence on the setting of the passive two-way switch, or wherein the mixer is configured as a passive mixer to reduce the flow through one path of the two fluidically separated paths of the heat exchanger unit in dependence on the setting of the passive mixer, or wherein the controller is configured to control the at least one control element such that the flow through one path of the two fluidically separated paths is effected when the condenser cycle temperature is at a predetermined ratio to the evaporator cycle temperature or lower than a predetermined condenser cycle temperature threshold, or wherein the controllable heat exchanger is configured such that a first path of the two fluidically separated paths of the heat exchanger unit can be continuously flowed-through independent of the controller and a second path of the two fluidically separated paths of the heat exchanger unit can be switched on or off or can be throttled with respect to an on-state by the controller.
3. The heat pump arrangement according to claim 1, wherein the controllable heat exchanger comprises a heat exchanger unit with four terminals and two fluidically separated paths and at least one control element fluidically coupled to the evaporator cycle interface, wherein the at least one control element comprises an input terminal, a first output terminal and a second output terminal, wherein the input terminal is connected to an output of the region to be cooled, wherein the first output terminal is connected to the first terminal of the heat exchanger unit, and wherein the second output terminal is connected to an input into the evaporator cycle interface for inputting the liquid to be cooled into the heat pump device, or wherein the at least one control element comprises a first input terminal, a second input terminal, and a first output terminal, wherein the first input terminal is connected to an output of the region to be cooled, wherein the second input terminal is connected to the second terminal of the heat exchanger unit, and wherein the output terminal is connected to an input into the evaporator cycle interface for inputting the liquid to be cooled into the heat pump device.
4. The heat pump arrangement according to claim 1, wherein the evaporator cycle interface comprises an input terminal to the heat pump device for the cooled liquid, and an output terminal to the heat pump device for the liquid to be cooled, and wherein the evaporator cycle interface is connected to the region to be cooled and to the controllable heat exchanger, wherein the evaporator cycle interface further comprises an evaporator cycle pump configured for circulating the liquid to be cooled or the cooled liquid, or wherein the condenser cycle interface comprises an input terminal to the heat pump device for the heated liquid, and an output terminal to the heat pump device for the liquid to be heated, and wherein the condenser cycle interface is connected to the region to be heated and to the controllable heat exchanger, wherein the condenser cycle interface further comprises a condenser cycle pump that is configured to circulate the heated liquid or the liquid to be heated, or wherein the evaporator cycle interface comprises an input terminal to the heat pump device for the cooled liquid, an output terminal to the heat pump device for the liquid to be cooled, and the evaporator cycle temperature sensor, and wherein the evaporator cycle interface is connected to the region to be cooled and to the controllable heat exchanger, wherein the evaporator cycle interface further comprises an evaporator cycle pump configured for circulating the liquid to be cooled or the cooled liquid, and wherein the evaporator cycle temperature sensor is configured to detect a temperature of the liquid to be cooled before the liquid to be cooled enters the controllable heat exchanger, or wherein the condenser cycle interface comprises an input terminal to the heat pump device for the heated liquid, an output terminal to the heat pump device for the liquid to be heated, and the condenser cycle temperature sensor, and wherein the condenser cycle interface is connected to a region to be heated and to the controllable heat exchanger, wherein the condenser cycle interface further comprises a condenser cycle pump that is configured to circulate the heated liquid or the liquid to be heated, wherein the condenser cycle temperature sensor is configured to detect a temperature of the liquid to be heated before the liquid to be heated enters the controllable heat exchanger.
5. The heat pump arrangement according to claim 1, wherein the controller is configured to prevent cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger and to perform, in dependence on a requested cooling capacity, a speed regulation of a radial wheel of a compressor in the heat pump device when the condenser cycle temperature as sensed by a condenser cycle temperature sensor of the liquid to be heated is higher than the evaporator cycle temperature as sensed by an evaporator cycle temperature sensor of the liquid to be cooled for the second temperature range, or to activate cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger and to increase or decrease a speed of a radial wheel within a compressor of the heat pump device in dependence on a requested cooling capacity or to deactivate the compressor in the heat pump device when the condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is lower than a predetermined temperature of the liquid to be cooled or the cooled liquid as sensed by the evaporator cycle temperature sensor for a first subrange of the first temperature range, or to activate cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger and to throttle a circulation pump arranged in the condenser cycle interface with respect to a set speed when the condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is equal to or lower than a predetermined temperature of the liquid to be cooled or the cooled liquid as sensed by the evaporator cycle temperature sensor for a second subrange of the first temperature range, wherein the second subrange comprises lower temperatures than the first subrange.
6. The heat pump arrangement according to claim 1, wherein the controller is configured to detect a specific state of the heat pump device, wherein the specific state of the heat pump device is such a state, in which the controllable short circuit of the controllable heat exchanger when activated by the controller results in an improved operating behavior of the heat pump device, and wherein the controller is configured to activate the controllable short-circuit of the controllable heat exchanger only when the specific state of the heat pump device has been detected by the controller.
7. The heat pump arrangement according to claim 1, wherein the controllable heat exchanger comprises a heat exchanger unit with four terminals and two fluidically separated paths and at least one control element fluidically coupled to the evaporator cycle interface, wherein the at least one control element fluidically coupled to the evaporator cycle interface is configured as a mixer, wherein the mixer is configured to bring, in the controllable short circuit when activated by the controller, a first portion of a liquid that can be circulated in the condenser cycle interface or the evaporator cycle interface into thermal operative connection to a liquid of the respective other interface and to bring a second portion of the liquid that can be circulated in the condenser cycle interface or the evaporator cycle interface not into thermal operative connection to the liquid of the respective other interface, wherein the first portion is smaller than the second portion.
8. The heat pump arrangement according to claim 7, wherein the mixer is controllable by the controller to control a ratio of the first portion to the second portion in dependence on an operating behavior of the heat pump device.
9. The heat pump arrangement according to claim 1, wherein the heat pump device comprises a compressor that is configured to be switched off in a switch-off even when the cooled liquid falls below a predetermined temperature as sensed by the evaporator cycle temperature sensor, or when the heated liquid exceeds a predetermined temperature as sensed by the condenser cycle temperature sensor, and wherein the controller is configured to detect a clocking frequency of the switch-off events and to activate, at the clocking frequency of the switch-off events being higher than a clocking frequency threshold, the controllable short circuit of the controllable heat exchanger, so that, due to the activated controllable short circuit of the controllable heat exchanger, the clocking frequency of the switch-off events is reduced or an occurrence of the switch-off events is eliminated.
10. The heat pump arrangement according to claim 1, wherein the evaporator cycle interface is configured to be coupled to the region to be cooled directly or via a heat exchanger, or wherein the condenser cycle interface is configured to be coupled to the region to be heated directly or via a heat exchanger.
11. The heat pump arrangement according to claim 1, wherein the evaporator cycle interface is configured to hold a first operating liquid, wherein the condenser cycle interface is configured to hold a second operating liquid, wherein the second operating liquid differs from the first operating liquid, or wherein the second operating liquid is CO.sub.2 and the first operating liquid is water or wherein the first operating liquid is water or CO.sub.2 and the second operating liquid is a water glycol mixture.
12. The heat pump arrangement according to claim 1, wherein the heat pump device comprises one or several stages, wherein one stage comprises an evaporator, a compressor, a condenser, and a throttle, wherein the stage is configured to use water as an operating medium, and wherein pressure differences between the evaporator and the condenser are below 300 mbar in an entire operating range, wherein the compressor comprises a radial wheel that is speed-controllable in dependence on a requested power of the heat pump device, and wherein the throttle is a self-regulating passive throttle, or wherein the heat pump device comprises one or several stages, wherein one stage comprises an evaporator, a compressor, a condenser, and a throttle, wherein the stage is configured to use a chemical medium as an operating medium, wherein a pressure difference between the evaporator and the condenser is greater than 5 bar, and wherein the compressor comprises a radial wheel that is speed-controllable in dependence on a requested power of the heat pump device, and wherein the throttle comprises a switchable throttle bypass in order to bring the operating medium from the condenser back into the evaporator.
13. A heat pump system, comprising: a region to be cooled; a region to be heated; and a heat pump arrangement comprising: a heat pump device; an evaporator cycle interface configured for inputting a liquid to be cooled into the heat pump device and configured for outputting a cooled liquid out of the heat pump device; a condenser cycle interface configured for inputting a liquid to be heated into the heat pump device and configured for outputting a heated liquid out of the heat pump device; a controllable heat exchanger configured for controllably coupling the evaporator cycle interface and the condenser cycle interface, the controllable heat exchanger comprising a controllable short circuit, wherein the controllable short circuit, when activated, is such that power requirements for the heat pump device are increased compared to power requirements in case of a deactivated controllable short circuit; and a controller configured for controlling the controllable heat exchanger in dependence on an evaporator cycle temperature in the evaporator cycle interface or a condenser cycle temperature in the condenser cycle interface, wherein the controller is configured to to activate cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger when a condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is lower than an evaporator cycle temperature as sensed by the evaporator cycle temperature sensor of the liquid to be cooled for a first temperature range, wherein the controllable short circuit is deactivated, to prevent cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger when the condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is higher than the evaporator cycle temperature as sensed by the evaporator cycle temperature sensor of the liquid to be cooled for a second temperature range, wherein the controllable short circuit is deactivated, and to activate the controllable short circuit of the controllable heat exchanger for a third temperature range, wherein the controllable heat exchanger, when the controllable short circuit of the controllable heat exchanger is activated, is configured to heat the liquid to be cooled in the evaporator cycle interface using the liquid to be heated in the condenser cycle interface or using the heated liquid in the condenser cycle interface, wherein the evaporator cycle interface is coupled to the region to be cooled, and wherein the condenser cycle interface is coupled to the region to be heated.
14. A method for producing a heat pump arrangement with a heat pump device, comprising: inputting a liquid to be cooled into the heat pump device and outputting a cooled liquid out of the heat pump device; inputting a liquid to be heated into the heat pump device and outputting a heated liquid out of the heat pump device; coupling liquid cooled by a region to be heated in a controllable and thermal manner to the liquid to be cooled via a controllable heat exchanger in dependence on an evaporator cycle temperature comprising a temperature of the liquid to be cooled or the cooled liquid or in dependence on a condenser cycle temperature comprising a temperature of the liquid to be heated or the heated liquid or the liquid cooled by the region to be heated, the controllable heat exchanger comprising a controllable short circuit, wherein the controllable short circuit, when activated, is such that power requirements for the heat pump device are increased compared to power requirements in case of a deactivated controllable short circuit, activating cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger when a condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is lower than an evaporator cycle temperature as sensed by the evaporator cycle temperature sensor of the liquid to be cooled for a first temperature range, wherein the controllable short circuit is deactivated, preventing cooling of the liquid to be cooled by the liquid to be heated using the controllable heat exchanger when the condenser cycle temperature as sensed by the condenser cycle temperature sensor of the liquid to be heated is higher than the evaporator cycle temperature as sensed by the evaporator cycle temperature sensor of the liquid to be cooled for a second temperature range, wherein the controllable short circuit is deactivated, and activating the controllable short circuit of the controllable heat exchanger for a third temperature range, wherein the controllable heat exchanger, when the controllable short circuit of the controllable heat exchanger is activated, is configured to heat the liquid to be cooled in the evaporator cycle interface using the liquid to be heated in the condenser cycle interface or using the heated liquid in the condenser cycle interface.
15. The heat pump arrangement according to claim 1, wherein the controllable heat exchanger comprises a heat exchanger unit with four terminals and two fluidically separated paths and at least one control element fluidically coupled to the evaporator cycle interface, wherein a third terminal of the four terminals and a fourth terminal of the four terminals are connected, wherein a second path of the two fluidically separated paths extends between the third terminal and the fourth terminal, and wherein the liquid to be heated leaves the second path via the fourth terminal and the heated liquid enters the second path via the third terminal after cooling in a region to be heated, wherein a first terminal of the four terminals and a second terminal of the four terminals are connected, so that a first path of the two fluidically separated paths extends between the first terminal and the second terminal, and wherein the first terminal of the heat exchanger unit or the second terminal of the heat exchanger unit is coupled to at least one terminal of the at least one control element in order to effect, reduce or prevent a flow through the first path of the two fluidically separated paths of the heat exchanger unit in dependence on a setting of the at least one control element, wherein the at least one control element fluidically coupled to the evaporator cycle interface is configured as a two-way switch or as a mixer.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:
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DETAILED DESCRIPTION OF THE INVENTION
(15)
(16)
(17) Thus, depending on the implementation, the controllable heat exchanger comprises a heat exchanger unit having four terminals and two fluidically separate paths, wherein at least one terminal is coupled to a control element, such as a two-way control element and in dependence on a setting of the control element, flow through one of the paths is effected, reduced or suppressed.
(18) Thus, the control element, such as 720, 730, 740, 750, 760 is configured to effect a flow through a path when the condenser cycle temperature is in a predetermined ratio to the evaporator cycle temperature or is less than a predetermined condenser cycle threshold.
(19) Depending on the implementation, the controllable heat exchanger 700 is configured such that one path of the controllable heat exchanger is continuously flowed-through independent of the control and another path of the controllable heat exchanger can be switched on or off or can be throttled by the control with respect to an on-state.
(20) Depending on the implementation, as will be discussed below, the controllable heat exchanger 700 includes a heat exchanger unit, namely the heat exchanger unit 710 of
(21) Above that, the condenser cycle interface 300 is coupled to a second path of the heat exchanger element, such that the liquid to be heated leaves the second path and the heated liquid enters the second path after cooling in a heat sink.
(22) A respective implementation where the controllable element is coupled to the first path of the heat exchanger unit 710 is shown in
(23) Here,
(24) It should further be noted that the condenser cycle interface 300 in
(25)
(26) In the embodiment shown in
(27) Above that, the second path of the heat exchanger unit is also connected to the input 230 of the heat pump device 100 for liquid to be cooled via a further connecting line 235.
(28)
(29)
(30) As shown in
(31) While
(32) Therefore, in the embodiment shown in
(33) If, however, it is determined that the evaporator cycle temperature TWK is lower than the condenser cycle temperature TWW, as determined by sensors 310 or 210, the control element is switched into the position of
(34)
(35) Although the control element 720, 730, 740, 750 is illustrated as two-way switches in
(36) Thereby, for example, an operating liquid having a temperature of 20 C. is heated to 24 C. by the effect of the heat exchanger unit 710. Thus, an overall achieved temperature of 21 C. results at the branch point or at the combination point where the output 712 of the first path is connected to the line for the liquid to be cooled 230. Thus, by implementing the control element 760 as a mixer, in a configuration as shown in
(37) Similar implementations for the mixer can also be provided for the control elements 740, 750 of
(38)
(39) Further, it should be noted that in the heat pump device 100 not only such a stage as illustrated in
(40) Further,
(41) Since in one embodiment the heat exchanger unit 710 is continuously flowed-through by the condenser cycle or by the evaporator cycle, cooling takes place at all times. The temperatures in the condenser cycle which can be above 20 C. are sufficient as cooling temperatures for the electronic arrangement. Therefore, it is advantageous to couple the heat exchanger unit 710 to the condenser cycle interface such that the heat exchanger unit 710 or a second path of the same is flowed-through by the condenser cycle. Thereby, the exhaust heat of the control electronics enters the condenser cycle directly and hence into the exhaust heat apparatus without having to be pumped first from the evaporator cycle into the condenser cycle.
(42)
(43) In particular in a cold temperature range where an exemplary air temperature is lower than 10 C. and wherein the sensor values are such that TWK is higher than TWW, free cooling is active. Further, the controllable heat exchanger is flowed-through from both sides, i.e., the same is active. Above that, as exemplarily shown in
(44) In a medium cold temperature range, which is, for example, between 10 C. and 16 C., free cooling is also active. Above that, the compressor is also active and regulation of the temperature fed into the data center or the region to be cooled can take place in that the speed of the radial wheel in the compressor is controlled. If higher cooling capacity is needed, the speed is increased. If, however, lower cooling capacity is needed, the speed of the radial wheel is reduced.
(45) In a normal operating mode which is activated in a warm temperature range, where the temperatures are, for example more than 16 C., it is typically determined that the temperature TWK is lower than the temperature TWW. Then, the controllable heat exchanger 710 is deactivated, i.e., switched to inactive and cooling capacity control can take place again via the speed of the radial wheel. In this mode, i.e., in the warm temperature range, no free cooling is active.
(46) As a special mode where a mixer as described with reference to
(47) Thus, according to the invention, the special mode with controllable short circuit is activated, which is detected, for example, by a specific clocking frequency. If a too high clocking frequency is determined, the controllable short circuit is activated, therefore a typically smaller part, i.e., a part less than 50% of the flow amount is fed into the respective first or second path of the heat exchanger unit and combined again with the other (typically greater) portion at the output of the heat exchanger unit. This mixer effect that has been illustrated in
(48) In embodiments of free cooling plus, a heat exchanger and a three-way switch are installed. This three-way switch can be incorporated on the cold water side or the warm water side and is to enable or disable the flow through the heat exchanger. Depending on the implementation, pumps PV 240 or PK 340 might be present or not. Above that, additional heat exchanges can be used, for example at the output of pump PV 240 or at the output of pump PK 340, although these heat exchanges are not illustrated in
(49) In specific alternative embodiments, it is advantageous that the control, i.e., whether the heat transfer is flowed-through or not, merely depends on the temperatures TWW and TWK, namely when the temperature TWW is lower than TWK, the heat exchanger unit is flowed-through. If the temperature in the evaporator is higher than the flow temperature on the cold water side or customer side, the compressor has to work. If, however, the temperatures in the free cooling mode are below the requested customer temperature, here 16 C., the fan on the roof and the finally the pumps can be throttled.
(50) In an embodiment of the present invention, a throttle is used for free-cooling plus that already safely operates without pressure difference or starting from a small pressure difference less than 10 mbar up to the maximum pressure stroke. Then, it is ensured that the cooling means balance is compensated from the liquefier to the evaporator when respective liquid compensation functionality is needed. This is in contrast to known cooling systems having electronic throttles that only operate at pressure differences of several bar.
(51) Above that, it is advantageous to use a flow machine as a compressor such that the needed pressure difference and the power, for example the mass flow, can be exactly controlled via the speed. Further, water is used as cooling means, wherein small pressure differences of less than 100 mbar are possible across the entire operating range and wherein further a self-regulating throttle can be incorporated due to the extreme volume differences between vapor and liquid. In order to be able to work with so-called chemical cooling means, i.e., cooling means differing from water, it is advantageous to use a switchable throttle bypass instead of the passive self-regulating throttle as illustrated in
(52) As has already been illustrated and has been explained based on
(53) One branch flows continuously through the heat exchanger unit in the controllable heat exchanger. Therefore, the heat exchanger is perfectly suitable for cooling capacity electronics. If the mixer is brought to the cold water side, the electronics introduces its losses directly into the cooling water side, i.e., into the condenser cycle. This has the advantage that the heat pump device does not have to provide the power loss first to the exhaust heat side by compressor work. The rectifiers for the frequency converter circuits are arranged on the heat exchanger unit, i.e., in thermal operative connection with the controllable heat exchanger.
(54) A method for producing a heat pump arrangement having a heat pump device comprises the following steps:
(55) Inputting liquid to the cooled into the heat pump device and outputting cooled liquid out of the heat pump device;
(56) Inputting liquid to be heated into the heat pump device and outputting heated liquid out of the heat pump device; and
(57) Coupling a liquid cooled by a heat sink in a controllable and thermal manner to the liquid to be cooled via a controllable heat exchanger in dependence on an evaporator cycle temperature having a temperature of the liquid to be cooled or the cooled liquid or in dependence on a condenser cycle temperature having a temperature of the liquid to be heated or the heated liquid or the liquid cooled by the heat sink.
(58) Although specific elements have been described as apparatus elements, it should be noted that this description is equally to be considered as the description of steps of a method and vice versa.
(59) Further, it should be noted that a control, for example, effected by the element 400 in
(60) While this invention has been described in terms of several advantageous embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.