Patent ID: 12196465

DETAILED DESCRIPTION

System Overview

FIG.1is a schematic diagram of an embodiment of a heating, ventilation, and air conditioning (HVAC) system100that is configured to use parallel flow expansion for pressure and superheat control. The HVAC system100is configured to use a combination of a fixed expansion device104and variable expansion device106to reduce the range of flow rates for the variable expansion device106which improves the operation of the HVAC system100by providing a faster response time, reducing pressure drops, and reducing thermal lag for the HVAC system100.

HVAC System

An HVAC system is generally configured to control the temperature of a space. Examples of a space include, but are not limited to, a refrigerator, a cooler, a room, a home, an apartment, a mall, an office, a warehouse, a building, and the like. In one embodiment, an HVAC system100may comprise an evaporator108, a compressor112, a condenser102, a fixed expansion device104, a sensing bulb110, a variable expansion device106, and/or any other suitable type of hardware for controlling the temperature of the space. The HVAC system100further comprises a working-fluid conduit subsystem for moving a working fluid, or refrigerant, through a cooling cycle. The working-fluid conduit subsystem may comprise tubes, pipes, orifices, connectors, or any other suitable type of components for routing a working fluid through the HVAC system100. The working fluid may be any acceptable working fluid, or refrigerant, including, but not limited to, fluorocarbons (e.g. chlorofluorocarbons), ammonia, non-halogenated hydrocarbons (e.g. propane), hydrofluorocarbons (e.g. R-410A), or any other suitable type of refrigerant.

Evaporator

The evaporator108is generally any heat exchanger configured to provide heat transfer between the air flowing through (or across) the evaporator108(i.e., air contacting an outer surface of one or more coils of the evaporator108) and working fluid passing through the interior of the evaporator108. The evaporator108may comprise one or more circuits of coils. The evaporator108is fluidically connected to the compressor112, such that working fluid generally flows from the evaporator108to the compressor112when the HVAC system100is operating to provide cooling and/or dehumidification. The evaporator108is generally configured to receive a working fluid (e.g. a refrigerant) in a liquid state, to evaporate the working fluid into a gaseous state, and to output the evaporated working fluid120in the gaseous state to the compressor112.

Compressor

The HVAC system100may be configured with a single-stage or multi-stage compressor112. A single-stage compressor112is configured to operate at a constant speed to increase the pressure of the working fluid to keep the working fluid moving along the working-fluid conduit subsystem. A multi-stage compressor112comprises multiple compressors configured to operate at a constant speed to increase the pressure of the working fluid to keep the working fluid moving along the working-fluid conduit subsystem. In this configuration, one or more compressors112can be turned on or off to adjust the cooling capacity of the HVAC system100. In some embodiments, a compressor112may be configured to operate at multiple speeds or as a variable speed compressor. For example, the compressor112may be configured to operate at multiple predetermined speeds. The compressor112is generally configured to receive the evaporated working fluid120from the evaporator108in the gaseous state, to compress the evaporated working fluid120, and to output the compressed working fluid122in the gaseous state to the condenser102.

Condenser

The condenser102is located downstream of the compressor112and is configured for rejecting heat. A fan126may be configured to move air across the condenser102. For example, the fan126may be configured to blow outside air through a heat exchanger to help cool the working fluid. The condenser102is generally configured to receive the compressed working fluid122from the compressor112, to condense or cool the compressed working fluid122from the gaseous state into a liquid state, and to output the condensed working fluid124in the liquid state to the variable expansion device106and the fixed expansion device104.

Fixed Expansion Device

The fixed expansion device104comprises a tubular structure with an opening that allows the working fluid to flow through the bore of the tubular structure. In one embodiment, the flow rate of the fixed expansion device104is proportional to the diameter of the opening of the fixed expansion device104. A larger opening provides a greater flow rate than a smaller opening since more working fluid can pass through the bore of the fixed expansion device104. Examples of the fixed expansion device104include, but are not limited to, an orifice, a capillary tube, a tube, or a nozzle. The fixed expansion device104is configured to remove pressure from the condensed working fluid124. The fixed expansion device104is coupled to the working-fluid conduit subsystem downstream of the condenser102for removing pressure from the condensed working fluid124. In this way, the working fluid is delivered to downstream components of the HVAC system100and receives heat from the airflow to produce a treated airflow that is delivered by a duct subsystem to the desired space, for example, a room in the building. The fixed expansion device104is generally configured to receive the condensed working fluid124from the condenser102and to output a first portion114of the condensed working fluid124in a liquid state at a fixed flow rate to downstream HVAC components (e.g. the evaporator108).

Sensing Bulb

The sensing bulb110comprises a hollow chamber fluidly coupled to a capillary tube. The hollow chamber is configured to store a fluid or gas118. The capillary tube is configured to allow the fluid or gas118to flow into and out of the hollow chamber. The sensing bulb110may be formed from steel or any other suitable type of material. The sensing bulb110is located adjacent to the evaporator108and is positioned to experience or sense heat that is emitted by the evaporator108. The sensing bulb110is generally configured to sense the temperature of the evaporator108and to output a fluid or gas118based on the sensed temperature of the evaporator108to the variable expansion device106. The amount of fluid or gas118that is transferred to the variable expansion device106is proportional to the temperature of the evaporator108. For example, the amount of fluid or gas118that is transferred to the variable expansion device106may increase when the temperature of the evaporator108increases and may decrease when the temperature of the evaporator108decreases.

Variable Expansion Device

The variable expansion device106is also configured to remove pressure from the condensed working fluid124. One embodiment of a variable expansion device106is illustrated and described in conjunction withFIG.2. The variable expansion device106is coupled to the working-fluid conduit subsystem downstream of the condenser102for removing pressure from the condensed working fluid124. The variable expansion device106is generally configured to receive the condensed working fluid124from the condenser102and to output a second portion116of the condensed working fluid124in a liquid state at a variable flow rate to downstream HVAC components (e.g. the evaporator108). The flow rate of the variable expansion device106is proportional to the sensed temperature of the evaporator108. The variable expansion device106is fluidly coupled to the sensing bulb110via a capillary tube. The variable expansion device106is configured to receive a fluid or gas118from the sensing bulb110that is proportional to the temperature of the evaporator108. As the amount of received fluid or gas118from the sensing bulb110increases, the variable expansion device106is configured to increase the flow rate of the condensed working fluid124that is transferred to downstream HVAC components. As the amount of received fluid or gas118decreases, the variable expansion device106is configured to decrease the flow rate of the condensed working fluid124that is transferred to downstream HVAC components. Additional information about the operation of the variable expansion device106is discussed below inFIG.2.

Variable Expansion Device Configuration

FIG.2is a schematic diagram of an embodiment of a variable expansion device106. In one embodiment, the variable expansion device106comprises a flexible diaphragm202, a pin204, a valve206, and a spring208.

The flexible diaphragm202is a thin material (e.g. sheet metal) that is operably coupled to the pin204such that the pin204moves up and down within the variable expansion device106with the flexible diaphragm202. The flexible diaphragm202is configured to receive a fluid or gas118from the sensing bulb110via a capillary tube216. The amount of fluid or gas118that is received from the sensing bulb110is proportional to the temperature of an evaporator108. The flexible diaphragm202is further configured to apply a force to reposition the pin204based on the received fluid or gas118from the sensing bulb110. In some embodiments, the variable expansion device106may further comprise an outlet214for an external equalization connection to equalize the force that is applied to the pin204.

As the amount of fluid or gas118that is received from the sensing bulb110increases, the flexible diaphragm202deflects to apply a downward force on the pin204. The downward movement of the pin204applies a second downward force to a valve206that is operably coupled to the pin204. The valve206is configured to adjust a flow rate of working fluid that passes from an inlet210of the variable expansion device106to an outlet of the variable expansion device106. As the valve206moves downward, the flow rate of the variable expansion device106increases.

As the amount of fluid or gas118that is received from the sensing bulb110decreases, the flexible diaphragm202deflects to decrease the downward force that is applied to the pin204. The upward movement of the pin204decreases the downward force that is applied to the valve206. As the valve206moves upward, the flow rate of the variable expansion device106decreases. The valve206is also operably coupled to a spring208that is configured to apply an upward force to the valve206to return the valve206to its normally closed position.

The size or weight of the pin204is proportional to a ratio between a maximum flow rate of the variable expansion device106and a total flow rate that is equal to the combined maximum flow rate for the fixed expansion device104and the variable expansion device106. As an example, the total flow rate for the HVAC system may be five tons. The fixed expansion device104may be configured to provide a flow rate of two and a half tons. This allows the pin204of the variable expansion device106to be reduced to also provide a flow rate of two and a half tons. In this example, the maximum flow rate of the variable expansion device106is set to fifty percent of the total flow rate provided by the variable expansion device106and the fixed expansion device104. This means that the size and weight of the pin204may be fifty percent smaller or lighter than a pin204that would be used to provide one hundred percent of the total flow rate. In other examples, the size or weight of the pin204is configured to provide any other suitable percentage of the total flow rate. For example, the size or weight of the pin204may be sized to provide a flow rate that is less than or equal to fifty percent of the total flow rate. Reducing the size or weight of the pin204reduces the range of the flow rates that are provided by the variable expansion device106. In the previous example, reducing the size or weight of the pin204by fifty corresponds with a fifty percent reduction in the range of flow rates provided by the variable expansion device106. Reducing the range of the flow rates allows the variable expansion device106to have a faster response time, reduced pressure drops, and reduced thermal lag for the HVAC system.

HVAC System with Secondary HVAC Components

FIG.3is a schematic diagram of another embodiment of an HVAC system300configured to use parallel flow expansion for pressure and superheat control. The HVAC system300is also configured to use a combination of a fixed expansion device104and variable expansion device106to reduce the range of flow rates for the variable expansion device106. InFIG.3, the HVAC system300comprises a primary evaporator310, a compressor112, a primary condenser302, a fixed expansion device104, a variable expansion device106, a sensing bulb110, a secondary evaporator304, a secondary condenser306, and an orifice308. In other embodiments, the HVAC system300may be configured in any other suitable configuration. For example, the HVAC system300may add or omit one or more components shown inFIG.3.

Primary Condenser

The primary condenser302is configured similar to the condenser102described inFIG.1. In this configuration, the primary condenser302is configured to receive a working fluid (e.g. a refrigerant) in a gaseous state, to condense the working fluid into a liquid state, and output a first condensed working fluid312in the liquid state to the fixed expansion device104and the variable expansion device106.

Fixed Expansion Device

The fixed expansion device104is configured to receive the first condensed working fluid312from the primary condenser302and to output a first portion314of the first condensed working fluid312in the liquid state at a fixed flow rate to downstream HVAC components (e.g. the secondary evaporator304).

Variable Expansion Device

The variable expansion device106is configured to receive the first condensed working fluid312from the primary condenser302and to output a second portion316of the first condensed working fluid312in the liquid state at a variable flow rate to downstream HVAC components. For example, the variable expansion device106is configured to receive a fluid or gas118from the sensing bulb110that is proportional to the temperature of the primary evaporator310. As the amount of received fluid or gas118from the sensing bulb110increases, the variable expansion device106is configured to increase the flow rate of the first condensed working fluid312that is transferred to downstream HVAC components. As the amount of received fluid or gas118decreases, the variable expansion device106is configured to decrease the flow rate of the first condensed working fluid312that is transferred to downstream HVAC components.

The variable expansion device106may be configured to provide the second portion316of the first condensed working fluid312to a variety of downstream HVAC components. For example, the variable expansion device106may be configured to output the second portion316of the first condensed working fluid312to an inlet328of the secondary evaporator301. As another example, the variable expansion device106may be configured to output the second portion316of the first condensed working fluid312to an inlet330of the orifice308. As another example, the variable expansion device106may be configured to output the second portion316of the first condensed working fluid312to an inlet332of the primary evaporator310. In other examples, the variable expansion device106may be configured to output the second portion316of the first condensed working fluid312to an inlet of any other suitable type of HVAC component.

Sensing Bulb

In this configuration, the sensing bulb110is configured to sense the temperature of the primary evaporator310and to output a fluid or gas118to the variable expansion device106that is proportional to the sensed temperature of the primary evaporator310.

Secondary Evaporator

The secondary evaporator304is configured similar to the evaporator310described inFIG.1. In one embodiment, the secondary evaporator304is configured to receive the first portion314of the first condensed working fluid312from the fixed expansion device104and to receive the second portion316of the first condensed working fluid312from the variable expansion device106. In this configuration, the secondary evaporator304is configured to evaporate the first portion314and the second portion316of the first condensed working fluid312into a gaseous state and to output a first evaporated working fluid318in the gaseous state.

In another embodiment, the secondary evaporator304may be configured to only receive the first portion314of the first condensed working fluid312from the fixed expansion device104. In this configuration, the secondary evaporator304is configured to evaporate the first portion314of the first condensed working fluid312into a gaseous state and to output a first evaporated working fluid318in the gaseous state.

Secondary Condenser

The secondary condenser306is configured similar to the condenser102described inFIG.1. The secondary condenser306is configured to receive the first evaporated working fluid318, to condense the first evaporated working fluid318from a gaseous state into a liquid state, and to output a second condensed working fluid320in the liquid state.

Orifice

Examples of the orifice308include, but are not limited to, capillary tubes and nozzles. In one embodiment, the orifice308may be configured to receive the second condensed working fluid320and the second portion316of the first condensed working fluid312from the variable expansion device106. In this configuration, the orifice308is configured to combine the second condensed working fluid320and the second portion316of the first condensed working fluid312and to output a combined working fluid322. The orifice308may be configured output the combined working fluid322with a fixed flow rate or a variable flow rate.

In another embodiment, the orifice308may be configured to only receive the second condensed working fluid320from the secondary condenser306. In this configuration, the orifice308is configured to output the working fluid322at either a fixed flow rate or a variable flow rate.

Primary Evaporator

The primary evaporator310is configured similar to the evaporator310described inFIG.1. In one embodiment, the primary evaporator310is configured to receive the working fluid322and the second portion316of the first condensed working fluid312. In this configuration, the primary evaporator310is configured to evaporate the working fluid322and the second portion316of the first condensed working fluid312into a gaseous state and to output a second evaporated working fluid324.

In another embodiment, the primary evaporator310may be configured to only receive the working fluid322. In this configuration, the primary evaporator310is configured to condense the working fluid322into a gaseous state and to output the second evaporated working fluid324.

Compressor

The compressor112is configured to receive the second evaporated working fluid324, to compress the second evaporated working fluid324, and to output a compressed working fluid326in the gaseous state to the primary condenser302.

Operation Process for an HVAC System

FIG.4is a flowchart of an embodiment of an HVAC operation process400for using parallel flow expansion. An HVAC system (e.g. HVAC system100or300) may employ process400to provide a faster response time, to reduce pressure drops, and to reduce thermal lag for the HVAC system by using a parallel combination of a fixed expansion device104and variable expansion device106. The parallel combination of the fixed expansion device104and the variable expansion device106reduces the workload of the variable expansion device106by reducing the range of flow rates for the variable expansion device106.

At step402, the fixed expansion device104and the variable expansion device106each receive working fluid from a condenser. Here, the fixed expansion device104and the variable expansion device106both receive the working fluid in a liquid state from a condenser, for example, the condenser102shown inFIG.1or the primary condenser302shown inFIG.3.

At step404, the fixed expansion device104outputs a first portion of the working fluid to a first downstream HVAC component. As an example, the fixed expansion device104may output the first portion of the working fluid at a fixed flow rate to an evaporator, for example, the evaporator108shown inFIG.1or the primary evaporator310shown inFIG.3.

At step406, the sensing bulb110senses a temperature of an evaporator. The sensing bulb110is configured to sense the temperature of the evaporator and to transfer an amount of fluid or gas118to the variable expansion device106that is proportional to the temperature of the evaporator. As the temperature of the evaporator increases, the sensing bulb110transfers more fluid or gas118to the variable expansion device106. As the temperature of the evaporator decreases, the sensing bulb110transfers less fluid or gas118to the variable expansion device106.

At step408, the sensing bulb110applies a first force to a pin204of the variable expansion device106based on the sensed temperature. As discussed above in step406, the sensing bulb110transfers an amount of fluid or gas118to the variable expansion device106that is proportional to the temperature of the evaporator. The fluid or gas118is transferred to the flexible diaphragm202of the variable expansion device106which then applies a first force to the pin204of the variable expansion device106that is proportional to the temperature of the evaporator.

At step410, the pin of the variable expansion device106applies a second force to a valve206of the variable expansion device106based on the first force. The first force repositions the pin204within the variable expansion device106which then causes the second force to be applied to the valve206of the variable expansion device106. A downward movement of the pin204applies a downward force to a valve206that is operably coupled to the pin204. As the valve206moves downward, the flow rate of the variable expansion device106increases. An upward movement of the pin204decreases the downward force that is applied to the valve206which allows the valve206to move upward. As the valve206moves upward, the flow rate of the variable expansion device106decreases.

At step412, the variable expansion device106outputs a second portion of the working fluid to a second downstream HVAC component at a variable flow rate based on the second force. As an example, the variable expansion device106may output the second portion of the working fluid to an evaporator, for example, the evaporator108shown inFIG.1, the primary evaporator310shown inFIG.3, or the secondary evaporator304shown inFIG.3. As another example, the variable expansion device106may output the second portion of the working fluid to an orifice, for example, the orifice308shown inFIG.3.

While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated with another system or certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants note that they do not intend any of the appended claims to invoke 35 U.S.C. § 112(f) as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.