Patent Description:
Heating, ventilating, and air conditioning (HVAC) systems can be used to regulate the environment within an enclosed space. Typically, an air blower is used to pull air (i.e., return air) from the enclosed space into the HVAC system through ducts and push the air into the enclosed space through additional ducts after conditioning the air (e.g., heating, cooling, or dehumidifying the air).

The cooling aspect of an HVAC system may utilize an evaporator that cools return air from the enclosed space. An expansion valve meters refrigerant to the evaporator while receiving the refrigerant from a condenser. The expansion valve, the evaporator, and the condenser form part of a closed-conduit refrigeration circuit of the HVAC system. There are, at times, issues with stable operation of the expansion valve that could benefit from improvements.

Illustrative embodiments of the present disclosure are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein.

The figures described above are only exemplary and their illustration is not intended to assert or imply any limitation with regard to the environment, architecture, design, configuration, method, or process in which different embodiments may be implemented.

Heating, ventilating, and air-conditioning (HVAC) systems commonly incorporate an expansion valve to regulate a flow of refrigerant from a condenser to an evaporator. The expansion valve, the condenser, and the evaporator are components of a closed-conduit refrigerant circuit, which also includes a compressor. The closed-conduit refrigerant circuit is operable to circulate refrigerant among its components, thus enabling the evaporator to produce a cooled airflow from unconditioned air.

To regulate the flow of refrigerant between the condenser and the evaporator, the expansion valve incorporates a movable pin that selectively occludes an internal flow orifice. The movable pin displaces along a pin stroke, positions of which, determine a degree of occlusion. An actuator is operable to displace the movable pin in response to a refrigerant temperature, which is sensed at an output of the evaporator. Such displacement typically occurs against a biasing member, such as a spring. The movable pin ceases its displacement when forces applied by the actuator and the biasing member balance.

As the refrigerant temperature changes, a force applied by the actuator changes and the movable pin adjusts to a new equilibrium point. This adjustment occurs dynamically as refrigerant traverses the expansion valve to flow from the condenser to the evaporator and the refrigerant temperature changes. However, under certain operating conditions, e.g., the HVAC system operating under reduced loads, the movable pin may oscillate around or excessively "hunting" the equilibrium point, causing unstable operation of the expansion valve. This unstable operation creates fluctuations in the flow of refrigerant, especially with regards to refrigerant temperature and pressure. These fluctuations negatively impact the HVAC system, reducing its efficiency and potentially damaging components of the closed-conduit refrigeration circuit.

The embodiments described herein relate to systems and methods for improving stabilization of a heating, ventilating, and air conditioning (HVAC) system. More specifically, the systems and methods include a heat-flow modulator for regulating an exchange of thermal energy between a flow of refrigerant and a sensory bulb. The exchange of thermal energy allows an expansion valve to respond to a refrigerant temperature using an actuator, which is coupled to the sensory bulb. The heat-flow modulator is formed of a body that includes a first contact surface and a second contact surface. The first contact surface is thermally-coupled to a suction line of the HVAC system, which conveys the flow of refrigerant. The second contact surface is thermally-coupled to the sensory bulb. The heat-flow modulator is operable to affect a flow of heat between the suction line and the sensory bulb, which includes providing a thermal resistance, a thermal capacitance, or both to the flow of heat. Such control regulates a response of the expansion valve to the refrigerant temperature and allows a pin within the expansion valve to reliably achieve an equilibrium point. Other systems and methods are presented.

Referring now to the drawings and primarily to <FIG>, a schematic diagram is presented of a heating, ventilating, and air conditioning (HVAC) system <NUM> having a heat flow modulator <NUM> for improving stabilization of an expansion valve <NUM>, according to an illustrative embodiment. The expansion valve <NUM> is operable to regulate a flow of refrigerant within the HVAC system <NUM>. The HVAC system <NUM> includes a closed-conduit refrigeration circuit <NUM>. The closed-conduit refrigeration circuit <NUM> is shown in <FIG> by tubing that represents fluid coupling between components of the closed-conduit refrigeration circuit <NUM>. Sections of tubing <NUM>, <NUM>, <NUM>, <NUM>, <NUM> correspond to individual conduits of refrigerant and arrows <NUM>, <NUM>, <NUM>, <NUM> indicate corresponding flows of refrigerant therein (i.e., when refrigerant is present in the HVAC system <NUM>).

The closed-conduit refrigeration circuit <NUM> includes an evaporator <NUM> for enabling a cooling capacity of the HVAC system <NUM>. The evaporator <NUM> typically includes at least one evaporator fan <NUM> to circulate a return air <NUM> across one or more heat-exchange surfaces of the evaporator <NUM>. The evaporator <NUM> is configured to transfer heat from the return air <NUM> to refrigerant therein. The return air <NUM> is drawn in from a conditioned space and exits the evaporator <NUM> as a cooled airflow <NUM>. Concomitantly, a low-pressure liquid refrigerant <NUM> enters the evaporator <NUM> and leaves as a low-pressure gas refrigerant <NUM>.

The closed-conduit refrigeration circuit <NUM> also includes a compressor <NUM> fluidly-coupled to the evaporator <NUM> via a suction line <NUM>, or tubing. The suction line <NUM> is operable to convey the low-pressure gas refrigerant <NUM> from the evaporator <NUM> to the compressor <NUM>. During operation, the compressor <NUM> performs work on the low-pressure gas refrigerant <NUM>, thereby generating a high-pressure gas refrigerant <NUM>. The high-pressure gas refrigerant <NUM> exits the compressor <NUM> through a discharge line <NUM>, or tubing. In some embodiments, the compressor <NUM> includes a plurality of compressors that form a tandem configuration within the closed-conduit refrigeration circuit <NUM>. In such embodiments, the plurality of compressors may be fluidly-coupled to the suction line <NUM> through a common suction manifold and fluidly-coupled to the discharge line <NUM> through a common discharge manifold. Other types of fluid couplings are possible.

The closed-conduit refrigeration circuit <NUM> also includes a condenser <NUM> that is fluidly-coupled to the compressor <NUM> via the discharge line <NUM>. The condenser <NUM> typically includes at least one condenser fan <NUM> to circulate a non-conditioned air <NUM> across one or more heat exchange surfaces of the condenser <NUM>. The condenser <NUM> is configured to transfer heat from refrigerant therein to the non-conditioned air <NUM>. The non-conditioned air <NUM> exits the condenser <NUM> as a warmed airflow <NUM>. Concomitantly, the high-pressure gas refrigerant <NUM> enters the condenser <NUM> and leaves as a high-pressure liquid refrigerant <NUM>. In some embodiments, the condenser <NUM> includes a microchannel condenser.

The closed-conduit refrigeration circuit <NUM> includes a liquid line <NUM>, or tubing, and a refrigerant line <NUM>, or tubing. The liquid line <NUM> fluidly-couples the condenser <NUM> to the expansion valve <NUM> and is operable to convey the high-pressure liquid refrigerant <NUM> from the condenser <NUM> to the expansion valve <NUM>. The refrigerant line <NUM> fluidly-couples the expansion valve <NUM> to the evaporator <NUM> and is operable to convey the low-pressure liquid refrigerant <NUM> from the expansion valve <NUM> to the evaporator <NUM>. In some embodiments, a distributor <NUM> splits the refrigerant line <NUM> into a plurality of branches <NUM>. These branches <NUM> transition into a plurality of short heat-transfer circuits (not explicitly shown) upon entry into the evaporator <NUM>. In such embodiments, the plurality of short heat transfer circuits may prevent large drops in pressure that might otherwise occur if a single, long circuit were used.

The expansion valve <NUM> serves to regulate the flow of refrigerant through the HVAC system <NUM> and to control a conversion of high-pressure liquid refrigerant <NUM> into low-pressure liquid refrigerant <NUM>. Such regulation is assisted by a sensory bulb <NUM>, which is fluidly-coupled to the expansion valve <NUM> and operates cooperatively with the heat-flow modulator <NUM>. The heat-flow modulator <NUM> includes a first contact surface <NUM> that is thermally-coupled to the suction line <NUM> and a second contact surface <NUM> that is thermally-coupled to the sensory bulb <NUM>. Such thermal coupling enables the heat-flow modulator <NUM> to regulate an amount of thermal energy exchanged between the suction line <NUM> and the sensory bulb <NUM>. This regulation improves stability of the expansion valve <NUM> during operation. Aspects of the heat-flow modulator <NUM> will be described further in relation to <FIG> and <FIG>.

Referring now primarily to <FIG>, a schematic diagram is presented, with a portion shown in cross-section, of an expansion valve suitable for use as the expansion valve <NUM> of <FIG>, according to an illustrative embodiment. It should be understood that the depiction of <FIG> is not intended as limiting and is presented for purposes of illustration only. Numerous types of expansion valves are suitable for use in the HVAC system <NUM> and might be incorporated therein in place of the one illustrated in <FIG>. Some features of the expansion valve <NUM> are shown in both <FIG> and <FIG> (e.g., the sensory bulb <NUM>). The expansion valve <NUM> includes a body <NUM> formed with a flow orifice <NUM>. The flow orifice <NUM> is operable to convey the flow of refrigerant from an inlet port <NUM> to an outlet port <NUM>. The inlet port <NUM> is configured to fluidly-couple the expansion valve <NUM> to the liquid line <NUM> of the closed conduit refrigeration circuit <NUM>. The outlet port <NUM> is configured to fluidly-couple the expansion valve <NUM> to the refrigerant line <NUM> of the closed-conduit refrigeration circuit <NUM>.

The expansion valve <NUM> also includes a pin <NUM> having a longitudinal axis <NUM>. The pin <NUM> is operable to control a primary flow of refrigerant through the flow orifice <NUM>, which includes varying an occlusion of the flow orifice <NUM>. The pin <NUM> is operatively movable along the longitudinal axis <NUM> between a closed position and an open position. The closed position and the open position define terminal points of a stroke of the pin <NUM>, or pin stroke. In the closed position, the pin <NUM> occludes the flow orifice <NUM>. Such occlusion may involve the pin <NUM> sealingly engaging the body <NUM> along one or more surfaces that define the flow orifice <NUM>. In the open position, the pin <NUM> substantially unoccludes the flow orifice <NUM>. Motion of the pin <NUM> within the pin stroke alters the occlusion of the flow orifice <NUM>. As the pin <NUM> moves from the closed position to the open position, the occlusion progressively decreases. As the pin <NUM> moves from the open position to the closed position, the occlusion progressively increases. In <FIG>, the pin <NUM> is depicted at a point along the pin stroke between the closed position and the open position.

In some embodiments, the expansion valve <NUM> includes a spring <NUM> arranged within the expansion valve <NUM> so as to bias the pin <NUM> in the closed position. In such embodiments, a spring guide <NUM> is typically operable to center the spring <NUM> along the longitudinal axis <NUM> of the pin <NUM>. In some embodiments, the pin <NUM> is disposed through the flow orifice <NUM>, as shown in <FIG>. This depiction, however, is not intended as limiting. For example, and without limitation, the pin <NUM> could be configured to sealingly engage the body <NUM> proximate the flow orifice <NUM>, but not extend therethrough. Other configurations are possible.

The expansion valve <NUM> includes an actuator <NUM> coupled to the pin <NUM> and configured to move the pin <NUM> in response to a refrigerant temperature. The refrigerant temperature is sensed adjacent an output of the evaporator <NUM> via the sensory bulb <NUM>. In some embodiments, the actuator <NUM> includes a chamber <NUM> having a diaphragm <NUM> coupled to the pin <NUM>. This coupling may involve other elements, such as a flexible plate <NUM>. The diaphragm <NUM> partitions the chamber <NUM> into a first compartment <NUM>, which is at or near a minimum in <FIG>, and a second compartment <NUM>. In such embodiments, the actuator <NUM> also includes a tube <NUM> coupling the chamber <NUM> to the sensory bulb <NUM>. The tube <NUM>, commonly a capillary transmission tube, enables fluid communication between the first compartment <NUM> of the chamber <NUM> and the sensory bulb <NUM>.

A fluid is disposed within a volume defined by the first compartment <NUM>, the sensory bulb <NUM>, and the tube <NUM>. The fluid is typically the same as a refrigerant used in the HVAC system <NUM>, although other fluids are possible. The fluid is operable to displace the diaphragm <NUM> in response to thermal energy entering or exiting the sensory bulb <NUM>. Such displacement adjusts a position of the pin <NUM>, thereby altering the flow of refrigerant through the flow orifice <NUM>. The expansion valve <NUM> is therefore able to regulate the flow of refrigerant through the HVAC system <NUM> in response to the refrigerant temperature of the low-pressure gas refrigerant <NUM> exiting the evaporator <NUM>.

In some embodiments, the expansion valve <NUM> includes a pressure equalizer port <NUM> fluidly-coupled to the suction line <NUM> of the closed-conduit refrigeration circuit <NUM>. In such embodiments, the pressure equalization port <NUM> enables the expansion valve <NUM> to sense a refrigerant pressure of the low-pressure gas refrigerant <NUM> exiting the evaporator <NUM>. The sensed refrigerant pressure is utilized by the expansion valve <NUM> to adjust the position of the pin <NUM>, thereby altering the flow of refrigerant through the flow orifice <NUM>. This alteration aids in regulating the flow of refrigerant through the HVAC system <NUM>. In some embodiments, the pressure equalizer port <NUM> is fluidly-coupled to the suction line <NUM> via a pressure equalization line <NUM>, such as that shown in <FIG>. In these embodiments, the pressure equalization line <NUM> forms a junction <NUM> with the suction line <NUM> in close proximity to the output of the evaporator <NUM>. The pressure equalizer port <NUM> is configured to receive refrigerant from the suction line <NUM> and convey such refrigerant into the second compartment <NUM> and against the diaphragm <NUM> (or flexible plate <NUM>). The diaphragm <NUM> (or flexible plate <NUM>) may displace when contacted by such refrigerant, i.e., displace in response to the refrigerant pressure, thereby adjusting the position of the pin <NUM>.

It will be appreciated that the expansion valve <NUM>, when including the pressure equalization port <NUM>, uses the refrigerant temperature and the refrigerant pressure in combination to regulate the flow of refrigerant in the HVAC system <NUM>. For embodiments that incorporate both the sensory bulb <NUM> and the pressure equalization line <NUM> - such as that depicted in <FIG> - the junction <NUM> is typically adjacent, but downstream a portion <NUM> of the HVAC system <NUM> that contains the sensory bulb <NUM>. More specifically, the portion <NUM> contains a segment of the suction line <NUM> thermally-coupled to the sensory bulb <NUM> via the heat-flow modulator <NUM>. However, other locations of the junction <NUM> are possible.

Now referring again primarily to <FIG>, the HVAC system <NUM> includes a refrigerant disposed therein (e.g., see arrows <NUM>, <NUM>, <NUM>, <NUM>). The closed-conduit refrigeration circuit <NUM> serves to convey refrigerant between components of the HVAC system <NUM> (e.g., the expansion valve <NUM>, the evaporator <NUM>, the compressor <NUM>, the condenser <NUM>, etc.). Individual components of the closed-conduit refrigeration circuit <NUM> then manipulate the refrigerant to generate the cooled airflow <NUM>.

In operation, the evaporator <NUM> receives the low-pressure liquid refrigerant <NUM> as a cold fluid from the expansion valve <NUM> via the refrigerant line <NUM> and, if present, the distributor <NUM> and associated plurality of branches <NUM>. The cold, low-pressure liquid refrigerant <NUM> flows through the evaporator <NUM> and, while therein, absorbs heat from the return air <NUM>. Such heat absorption maybe aided by the at least one evaporator fan <NUM> and the one or more heat-exchange surfaces of the evaporator <NUM>. The at least one evaporator fan <NUM> enables a forced convection of return air <NUM> across the one or more heat-exchange surfaces of the evaporator <NUM>. Absorption of heat by the cold, low-pressure liquid refrigerant <NUM> induces a conversion from liquid to gas (i.e., boiling) of refrigerant within the evaporator <NUM>. The cold, low-pressure liquid refrigerant <NUM> therefore leaves the evaporator <NUM> as a warm, low-pressure gas refrigerant <NUM>. Concomitantly, the return air <NUM> exits the evaporator <NUM> as the cooled airflow <NUM>.

Conversion of the cold, low-pressure liquid refrigerant <NUM> into the warm, low-pressure gas refrigerant <NUM> often produces a superheated refrigerant whose temperature exceeds a saturated boiling point. Superheated refrigerant is generated when warm, low-pressure gas refrigerant <NUM> continues to absorb heat after changing from liquid to gas. Such absorption occurs predominantly within the evaporator <NUM>, but may also occur within the suction line <NUM>. A degree of superheat is typically measured in terms of temperature (e.g., °F, °C, K) and refers to a difference in temperature between the superheated refrigerant and its saturated boiling point.

After leaving the evaporator <NUM>, the warm, low-pressure gas refrigerant <NUM> traverses the suction line <NUM> of the closed-circuit refrigeration circuit <NUM> and enters the compressor <NUM>. The compressor <NUM> performs work on the warm, low-pressure gas refrigerant <NUM>, producing a hot, high-pressure gas refrigerant <NUM>. The hot, high-pressure gas refrigerant <NUM> exits the compressor <NUM> via the discharge line <NUM> and travels to the condenser <NUM>. The hot, high-pressure gas refrigerant <NUM> flows through the condenser <NUM>, and while therein, transfers heat to the non-conditioned air <NUM>. Such heat transfer may be assisted by the at least one condenser fan <NUM> and the one or more heat-exchange surfaces of the condenser <NUM>. The at least one condenser fan <NUM> enables a forced convection of non-conditioned air <NUM> across the one or more heat-exchange surfaces of the condenser <NUM>. Loss of heat from the hot, high-pressure gas refrigerant <NUM> induces a conversion from gas to liquid (i.e., condensing) within the condenser <NUM>. The hot, high-pressure gas refrigerant <NUM> therefore leaves the condenser <NUM> as a warm, high-pressure liquid refrigerant <NUM>. Concomitantly, the non-conditioned air <NUM> exits the condenser <NUM> as the warmed airflow <NUM>.

Conversion of the hot, high-pressure gas refrigerant <NUM> into the warm, high-pressure liquid refrigerant <NUM> often produces a subcooled refrigerant whose temperature is below a saturated condensation point. Subcooled refrigerant is generated when warm, high-pressure liquid refrigerant <NUM> continues to lose heat after changing from gas to liquid. Such loss occurs predominantly within the condenser <NUM>, but may also occur within the liquid line <NUM>. A degree of subcooling is typically measured in terms of temperature (e.g., °F, °C, K) and refers to a difference in temperature between the subcooled refrigerant and its saturated condensing point.

After leaving the condenser <NUM>, the warm, high-pressure liquid refrigerant <NUM> flows through the liquid line <NUM> to reach the expansion valve <NUM>. As explained more below, passage of the warm, high-pressure liquid refrigerant <NUM> through the flow orifice <NUM> induces a lowering of pressure and temperature that generates the cold, low-pressure liquid refrigerant <NUM>. The position of the pin <NUM> relative the flow orifice <NUM> serves to regulate flow through the expansion valve <NUM>, and hence, generation of the cold, low-pressure liquid refrigerant <NUM>. The cold, low-pressure liquid refrigerant <NUM> is then conveyed to the evaporator <NUM> by the refrigerant line <NUM> (and, if present, the distributor <NUM> and associated plurality of branches <NUM>).

It will be appreciated that the closed-conduit refrigeration circuit <NUM> circulates the refrigerant to allow repeated processing by the evaporator <NUM>, the compressor <NUM>, the condenser <NUM>, and the expansion valve <NUM>. Repeated processing, or cycles, enables the HVAC system <NUM> to continuously produce the cooled airflow <NUM> during operation. During such cycling, the expansion valve <NUM> regulates the flow of refrigerant through the HVAC system <NUM>, which includes receiving the warm, high-pressure liquid refrigerant <NUM> from the condenser <NUM> and metering the cold, low-pressure liquid refrigerant <NUM> to the evaporator <NUM>. The former flow influences the degree of subcooling and the latter flow influences the degree of superheat. Higher degrees of superheat reduce a risk that the warm, low-pressure gas refrigerant <NUM> will enter the compressor <NUM> with a non-zero liquid fraction. Higher degrees of subcooling reduce a risk that the warm, high-pressure liquid refrigerant <NUM> will enter the expansion valve <NUM> with a non-zero gas fraction.

Now referring again primarily to <FIG>, the expansion valve <NUM> regulates refrigerant flowing through the HVAC system <NUM> by receiving refrigerant through the inlet port <NUM> (see arrow <NUM>). This received refrigerant traverses the body <NUM> and exits the outlet port <NUM> (see arrow <NUM>). A presence of refrigerant within the body <NUM> enables the pin <NUM> to fluidly-couple to the flow orifice <NUM>. Such fluid coupling includes impeding refrigerant flowing through the flow orifice <NUM> (i.e., with the pin <NUM>). When the pin <NUM> is in the open position, the flow of refrigerant exhibits a maximum magnitude. When the pin <NUM> is in the closed position, the flow of refrigerant substantially ceases. Between the open position and the closed position, i.e., along the pin stroke, the flow of refrigerant varies in magnitude between the maximum magnitude and substantially zero, respectively.

When the pin <NUM> is in the open position, the expansion valve <NUM> operates at "full load". The expansion valve <NUM>, however, can transition into "part load" operation if the pin <NUM> moves along the pin stroke towards the closed position. "Part load" operation corresponds to that portion of the pin stroke where the flow of refrigerant exhibits a reduced, non-zero magnitude relative to the maximum magnitude. For example, and without limitation, "part load" operation may correspond to that portion of the pin stroke where the flow of refrigerant is <NUM>% or below that of the maximum magnitude. If the pin <NUM> moves into the closed position, the expansion valve <NUM> transitions into "no load" operation. In "no load" operation, the flow of refrigerant substantially ceases.

During operation, a plurality of forces acts on the pin <NUM> to determine the position of the pin <NUM> within the pin stroke. Refrigerant flowing from the inlet port <NUM> through the flow orifice <NUM> impinges on the pin <NUM>, biasing the pin <NUM> towards the open position and contributing to an opening force. The actuator <NUM> also contributes to the opening force depending on the refrigerant temperature, which is typically sensed proximate the output of the evaporator. For embodiments where the actuator <NUM> incorporates the diaphragm <NUM>, such as that illustrated in <FIG>, the diaphragm <NUM> flexes in response to thermal energy transferring into or out of the fluid. Such transfer typically occurs at the sensory bulb <NUM>, which is thermally-coupled to the suction line <NUM> through the heat-flow modulator <NUM>. Because the fluid is sealed in the volume defined by the first compartment <NUM>, the sensory bulb <NUM>, and the tube <NUM>, thermal energy entering the fluid causes an increase in pressure that displaces the diaphragm <NUM> towards the body <NUM>. Conversely, thermal energy leaving the fluid causes a decrease in pressure that allows the diaphragm to relax away from the body <NUM>. By virtue of its coupling to the pin <NUM>, the diaphragm <NUM> contributes to the opening force when thermal energy enters the fluid. Such contribution decreases in magnitude when thermal energy leaves the fluid.

The spring <NUM> biases the pin <NUM> towards the closed position and contributes to a closing force. A strength of such bias increases as the pin <NUM> moves towards the open position, i.e., the spring <NUM> becomes increasingly compressed. An initial spring bias is typically determined by selecting an initial compression of the spring <NUM>. The pressure equalizer port <NUM>, if present, may also contribute to the closing force depending on the refrigerant pressure, which is typically sensed proximate the output of the evaporator (e.g., at the junction <NUM>). The pressure equalizer port <NUM> is fluidly-coupled to the diaphragm <NUM> via the second compartment <NUM>. Such fluid-coupling allows the refrigerant pressure to be conveyed from the pressure equalizer port <NUM>, through the second compartment <NUM>, and against the diaphragm <NUM>. The refrigerant pressure displaces the diaphragm <NUM> away from the body <NUM> which, by virtue of its coupling to the pin <NUM>, contributes to the closing force. This contribution increases or decreases as the refrigerant pressure, respectively, increases or decreases.

As refrigerant flows through the expansion valve <NUM>, the pin <NUM> translates along the pin stroke until an equilibrium point is reached where the opening force balances the closing force. The equilibrium point changes dynamically in response to the refrigerant temperature and, in some embodiments, the refrigerant pressure. When integrated into the HVAC system <NUM>, it will be appreciated that the expansion valve <NUM> translates the pin <NUM> to meter refrigerant to the evaporator and to maintain a substantially constant degree of superheat therein. Thus, the expansion valve <NUM> sustains HVAC operating efficiencies while transitioning between "full load", "part load", and "no load" (i.e., as cooling demands on the evaporator <NUM> change). The expansion valve <NUM> also influences the degree of subcooling in the condenser. Translation of the pin <NUM> along the pin stroke alters refrigerant flow through the inlet port <NUM>, which due to fluid-coupling with the condenser <NUM>, varies a residence time of refrigerant flowing therein.

During certain operating conditions, without more, the expansion valve <NUM> may become susceptible to unstable regulation of the flow of refrigerant. For example, and without limitation, the HVAC system <NUM> may experience a reduced cooling demand that forces the expansion valve <NUM> into "part load" operation. If this "part load" operation corresponds to a small fraction of "full load" operation, e.g., less than <NUM>% of the maximum magnitude, the pin <NUM> may experience difficulty finding the equilibrium point.

More specifically, the actuator <NUM> may contribute to the opening force in such a manner as to cause the pin <NUM> to oscillate around or excessively "hunt" the equilibrium point. Such oscillation or "hunting" may cause undesirable fluctuations the flow of refrigerant (e.g., unstable suction pressure in refrigerant flowing through the suction line <NUM>).

To mitigate this behavior, the heat-flow modulator <NUM> provides a thermal resistance, a thermal capacitance, or both to a flow of heat caused by changes in refrigerant exiting the evaporator <NUM> (e.g., changes in the refrigerant temperature). These thermal characteristics aid the heat-flow modulator <NUM> in smoothing or delaying the flow of heat between the suction line <NUM> and the sensory bulb <NUM>. The actuator <NUM> is therefore allowed sufficient time to apply a steady force onto the pin <NUM>, allowing the pin <NUM> to reliably find the equilibrium point. Thus, the heat-flow modulator <NUM>, in cooperation with expansion valve <NUM>, ensures a controlled flow of refrigerant in the closed-conduit refrigeration circuit <NUM> and an improved stability of the HVAC system <NUM>.

Now referring primarily to <FIG>, a perspective view is presented of a portion <NUM> of a heating, ventilating, and air conditioning (HVAC) system having a heat-flow modulator <NUM> for improved stability, according to an illustrative embodiment. <FIG> presents a rear elevation view of the portion <NUM>. The portion <NUM> of <FIG> is analogous to the portion <NUM> of <FIG>. The portion <NUM> includes a section <NUM> of a suction line immediately downstream of an evaporator (see <NUM> in <FIG>). The portion <NUM> also includes a sensory bulb <NUM> thermally-coupled to the section <NUM> via the heat-flow modulator <NUM>. The sensory bulb <NUM> incorporates a tube <NUM> for fluidly-coupling to an actuator of an expansion valve. For purposes of illustration, the tube <NUM> is presented only partially in <FIG>.

The heat-flow modulator <NUM> includes a first contact surface <NUM> and a second contact surface <NUM> (see <FIG>). The first contact surface <NUM> is thermally-coupled to the section <NUM> of the suction line and the second contact surface <NUM> is thermally-coupled to the sensory bulb <NUM>. This thermal coupling typically involves direct contact. However, in some embodiments, a thermal interface material (TIM) may be disposed between the first contact surface <NUM> and the section <NUM>, the second contact surface <NUM> and the sensory bulb <NUM>, or both. In such embodiments, the thermal interface material influences heat flow between neighboring components and may also secure one component to another. Non-limiting examples of thermal interface materials include thermal paints, frits, solders, pastes, epoxies, tapes, and glues. In some embodiments, the portion <NUM> of the HVAC system includes at least one bracket member <NUM> for urging the section <NUM> of the suction line (or portion thereof) towards the first contact surface <NUM>. In these embodiments, the at least one bracket member <NUM> also urges the sensory bulb <NUM> (or portion thereof) towards the second contact surface <NUM>. The at least one bracket member <NUM> may be configured to influence heat flow between the section <NUM> and the sensory bulb <NUM> (e.g., increase heat transfer between the section <NUM> and the sensory bulb <NUM>).

The heat-flow modulator <NUM> typically includes a body <NUM>, or modulator body, that incorporates the first contact surface <NUM> and the second contact surface <NUM>. The body <NUM> may be deformable. The body <NUM> is configured to provide a thermal resistance, a thermal capacitance, or both to heat flowing between the first contact surface <NUM> and the second contact surface <NUM>. <FIG> shows a perspective view of the body <NUM> of the heat-flow modulator <NUM>. A rear elevation view of the body <NUM> is shown in <FIG>. The body <NUM>, in cooperation with the first contact surface <NUM> and the second contact surface <NUM>, is operable to direct heat flow between the sensory bulb <NUM> and the section <NUM> of the suction line. Dimensions of the body <NUM> (e.g., length, width, height, etc.) and its shape may be selected to direct heat along a predetermined thermal flow path. In some embodiments, the first contact surface <NUM> is formed on the body <NUM> as a first concave portion and the second contact surface <NUM> is formed as a second concave portion that faces away from the first concave portion. In other embodiments, the body <NUM> may have a rectilinear cross-section such as a square or rectangular cross-section. Other dimensions and shapes, however, are possible.

The body <NUM> is formed from a thermally-insulating material. The thermally-insulating material may have a thermal conductivity less than <NUM> W / (m • K). It will be appreciated that the body <NUM> is not limited to a single material, but in certain embodiments, may be formed from a plurality of materials (e.g., a textured composite). In these embodiments, the plurality of materials may be selected to impart predetermined thermal resistances and thermal capacitances to the body <NUM>. The plurality of materials may also be structured within the body <NUM> to constrain heat substantially along the predetermined thermal flow path.

In operation, the section <NUM> of the suction line conveys refrigerant from the evaporator towards a compressor and thereby attains an operating temperature that reflects a refrigerant temperature of refrigerant exiting the evaporator. If the operating temperature is greater than a temperature of the sensory bulb <NUM>, heat will traverse the heat-flow modulator <NUM> to flow from the section <NUM> to the sensory bulb <NUM>. If the operating temperature is less than the temperature of the sensory bulb <NUM>, heat will flow in an opposite direction, traversing the heat-flow modulator <NUM> to flow from the sensory bulb <NUM> to the section <NUM>.

Heat enters and leaves the body <NUM> substantially through the first contact surface <NUM> and the second contact surface <NUM>. Moreover, after entering the body <NUM>, heat flows substantially along the predetermined thermal flow path and experiences a resistance. This resistance stems from the thermal resistance, which retards a rate of heat transfer between the first contact surface <NUM> and the second contact surface <NUM>. This resistance may also be influenced by the thermal capacitance, which smooths the rate of heat transfer between the first contact surface <NUM> and the second contact surface <NUM>. Thus, the body <NUM>, by providing the thermal resistance, the thermal capacitance, or both, enables the heat-flow modulator <NUM> to regulate heat exchanged between the section <NUM> of the suction line and the sensory bulb <NUM>.

Although the heat flow modulator <NUM> is depicted in <FIG> as having a body <NUM> with concave portions, this depiction is not intended as limiting. The body <NUM> may have other portions and still remain with the scope of this disclosure. For example, and without limitation, <FIG> presents a perspective view of a body <NUM> of a heat-flow modulator <NUM> having a rectangular cross-section. The body <NUM> has a first contact surface <NUM> and a second contact surface <NUM> defined by planar, parallel portions. The rectangular cross-section is highlighted in <FIG>, which shows a rear view of the body <NUM>. Features analogous to both <FIG> and <FIG> are related via coordinated numerals that differ in increment by a hundred.

According to an illustrative embodiment, a heat-flow modulator includes an insulating body that is operatively disposed between a portion of a suction line and a sensory bulb of an expansion valve. The insulating body has a first contact surface and a second contact surface. The first contact surface is thermally-coupled to the portion of the suction line and the second contact surface is thermally-coupled to the sensory bulb. The heat-flow modulator also includes a mounting bracket. The mounting bracket is operable to urge the portion of the suction line toward the first contact surface and to urge the sensory bulb (or a portion thereof) towards the second contact surface. During operation, refrigerant flows through the portion of the suction line. In response, heat is exchanged substantially through the mounting bracket between the portion of the suction line and the sensory bulb. A temperature of the portion is therefore communicated to the sensory bulb solely through the mounting bracket. The temperature of the portion may represent a temperature of refrigerant flowing therein.

According to an illustrative embodiment, a heat-flow modulator includes a body having an arc-shaped cross-section. The body is typically formed of an insulating material and has a length that varies between <NUM>" to <NUM>". The arc-shaped cross-section extends entirely through the length of the body and thereby forms a concave surface and a convex surface. The arc-shaped cross-section has a width of approximately <NUM>" and a thickness of approximately <NUM>" (i.e., when viewed from an end perspective). The concave surface defines a first contact surface for thermally-coupling to a portion of a suction line. The convex surface of the body defines a second contact surface for thermally-coupling to a sensory bulb of an expansion valve. The specific dimension are not intended to be limiting but to offer one illustrative embodiment.

According to an illustrative embodiment, a method for stabilizing suction pressure within a heating, ventilating, and air conditioning (HVAC) system includes the step of using a heat-flow modulator to exchange heat between refrigerant in a suction line and a sensory bulb. The HVAC system has a closed-conduit refrigeration system. The method also includes the step of fluidly-coupling the sensory bulb to an expansion valve and the step of altering the flow of refrigerant through the expansion valve in response to heat exchanged between the sensory bulb and the heat-flow modulator. The expansion valve is configured to regulate refrigerant flow within the closed-conduit refrigeration circuit is also configured to meter the flow of refrigerant (i.e., flowing through the expansion valve) to the evaporator.

In some embodiments, the heat-flow modulator comprises a modulator body having a first contact surface and a second contact surface. In such embodiments, the first contact surface is thermally-coupled to the suction line and the second contact surface is thermally-coupled to the sensory bulb.

In some embodiments, the step of using a heat-flow modulator to exchange heat includes the step of directing heat along a predetermined thermal flow path of the heat-flow modulator. In some embodiments, the method further includes the step of conveying refrigerant from the evaporator to a compressor via a suction line.

In some embodiments, the step of using the heat-flow modulator to exchange heat includes flowing heat from the suction line through a first contact surface of the heat-flow modulator. In some embodiments, the step of using the heat-flow modulator to exchange heat includes flowing heat from the suction line through a first contact surface of the heat-flow modulator and through a second contact surface into the sensory bulb.

In some embodiments, the step of using the heat-flow modulator to exchange heat includes the step of flowing heat from the suction line through the first contact surface of the heat-flow modulator and through the second contact surface into the sensory bulb. In such embodiments, the method also includes the step of flowing heat from the suction line through at least one bracket into the sensory bulb.

In some embodiments, the step of altering the flow of refrigerant through the expansion valve includes the step of decreasing an occlusion of a fluid-flow orifice in the expansion valve in response to heat entering the sensory bulb. In these embodiments, the method also includes the step of increasing the occlusion of the fluid-flow orifice in the expansion valve in response to heat leaving the sensory bulb.

In some embodiments, the heat-flow modulator includes a body having a first concave portion and a second concave portion. In some embodiments, the heat-flow modulator includes a thermally-insulating material. In other embodiments, the heat-flow modulator includes thermally-conducting material.

While not limited to any certain theory, in some embodiments, it may be useful to consider that the heat flow modulator can modulate heat between the suction line and bulb using the following formula = kA(T_bulb - T_suction) / t, where k=thermal cond, A- contact area, t-thickness of modulator. Any one of the components (k, A, or t) can be changed to modulate. If an effective A and effective t were imagined, then either of these can be adjusted to modulate heat transfer rate. Change in material is one of these choices. It should be appreciated that the shape and size can also be changed to optimize the modulator.

Although the present invention and its advantages have been disclosed in the context of certain illustrative, non-limiting embodiments, it should be understood that various changes, substitutions, permutations, and alterations can be made without departing from the scope of the invention as defined by the appended claims. It will be appreciated that any feature that is described in connection to any one embodiment may also be applicable to any other embodiment.

It will further be understood that reference to "an" item refers to one or more of those items.

The steps of the methods described herein may be carried out in any suitable order or simultaneous where appropriate. Where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and addressing the same or different problems.

It will be understood that the above description of the embodiments is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments of the invention. Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of the claims.

In the detailed description of the illustrative embodiments, reference is made to the accompanying drawings that form a part hereof. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the embodiments described herein, the description may omit certain information known to those skilled in the art. The detailed description above is, therefore, not to be taken in a limiting sense, and the scope of the illustrative embodiments is defined only by the appended claims.

In the drawings and description herein, like parts are typically marked throughout the specification and drawings with the same reference numerals or coordinated numerals. The drawing figures are not necessarily to scale. Certain features of the illustrative embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness.

Unless otherwise specified, any use of any form of the terms "connect," "engage," "couple," "attach," or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to". Unless otherwise indicated, as used throughout this document, "or" does not require mutual exclusivity.

As used herein, the phrases "fluidly coupled," "fluidly connected," and "in fluid communication" refer to a form of coupling, connection, or communication related to fluids, and the corresponding flows or pressures associated with these fluids. In some embodiments, a fluid coupling, connection, or communication between two components may also describe components that are associated in such a way that a fluid can flow between or among the components. Such fluid coupling, connection, or communication between two components may also describe components that are associated in such a way that fluid pressure is transmitted between or among the components.

Claim 1:
A heating, ventilating, and air conditioning system (<NUM>) comprising:
a closed-conduit refrigeration circuit comprising:
an expansion valve (<NUM>) fluidly coupled to a sensory bulb (<NUM>), the expansion valve configured to regulate refrigerant flow within the closed-conduit refrigeration circuit,
an evaporator (<NUM>) fluidly-coupled to the expansion valve via a refrigeration line,
a compressor (<NUM>) fluidly-coupled to the evaporator via a suction line,
a condenser (<NUM>) fluidly-coupled to the compressor and to the expansion valve,
the system being characterized by a heat-flow modulator (<NUM>), the heat-flow modulator comprising a modulator body having a first contact surface and a second contact surface, the first contact surface thermally-coupled to the suction line and the second contact surface thermally-coupled to the sensory bulb; and wherein the modulator body is formed from a thermally-insulating material, wherein the thermally-insulating material has a thermal conductivity less than <NUM> W / (m • K).