Patent Application
20170102174
The present disclosure is directed to HVAC systems and more particularly to pressure relief for these systems.
HVAC systems may have pressure sensitivities during operation. For example, air conditioners may include microchannel condensers (e.g., condenser with a channel size less than approximately 1 mm) rather than other types of condensers (e.g., condenser with tube size greater than 5 mm). The buildup of refrigerant pressure in HVAC systems is a common problem. The problem can be particularly acute in systems with a microchannel condenser because microchannel condensers may be sensitive to certain operating conditions. For example, when ambient temperatures (e.g., temperatures proximate a condenser or temperature proximate a condenser fan) are high, the pressure in the microchannel condenser may become elevated due to the refrigerant capacity size difference between the microchannel condenser and the evaporator. The high pressures (e.g., pressures greater than approximately 615 psi, in some embodiments) may cause mechanical failure, including prefailure events, such as excessive wear on parts. High pressures may also trip safety systems designed to prevent overpressure. One previous solution has been to limit refrigerant within an HVAC system. However, this solution leads to a loss in cooling capacity or efficiency.
A particular problem can occur upon startup of an HVAC system. Refrigerant may not be evenly/properly distributed within the system, leading to refrigerant and/or pressure imbalances. One solution has been to change the size of microchannels within the HVAC system, such as in the condenser. However, this may limit other properties or capabilities of the system, and such a solution may not be feasible as a retrofit solution.
One embodiment of the present disclosure is an HVAC system comprising an evaporator operable to receive refrigerant in a liquid state and evaporate the refrigerant into a gaseous state; a pressure sensor, the pressure sensor located within a liquid line of the HVAC system and operable to measure the pressure within the liquid line; a compressor operable to receive refrigerant from the evaporator; a condenser operable to receive refrigerant from the compressor in a gaseous state and condense the refrigerant into a liquid state; an expansion device operable to receive refrigerant from the condenser and direct the refrigerant toward the evaporator; a bypass line, the bypass line operable to direct refrigerant away from the expansion device and return the refrigerant to the HVAC system; and a controller, the controller coupled to at least the pressure sensor and the bypass line, the controller operable to direct refrigerant to the bypass line when the pressure reaches a predetermined value.
Another embodiment comprises a method of relieving pressure within an HVAC system comprising: receiving a signal to start the HVAC system; opening a bypass line, the bypass line capable of diverting refrigerant away from an expansion valve and returning the refrigerant to the HVAC system; starting the HVAC system; and closing the bypass line when a predetermined event has occurred.
Another embodiment comprises a method of operating an HVAC system comprising a controller, a condenser, a compressor, an evaporator, and an expansion device, the method comprising: receiving, at the controller, a pressure reading for the HVAC system; opening, by the controller, a valve to a bypass line when the pressure reading exceeds a predetermined value; wherein the bypass line directs refrigerant away from an expansion device and returns the refrigerant to the HVAC system.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
HVAC systems may have pressure sensitivities (surges) during operation. For example, air conditioners may include microchannel condensers (e.g., condenser with a channel size less than approximately 1 mm) rather than other types of condensers (e.g., condenser with tube size greater than 5 mm). Microchannel condensers may be sensitive to certain operating conditions, especially the pressure at the compressor discharge. For example, when ambient temperatures (e.g., temperatures proximate a condenser or temperature proximate a condenser fans) are high, the pressure in the microchannel condenser may become elevated due to the refrigerant capacity size difference between the microchannel condenser and the evaporator. The high pressures (e.g., pressures greater than approximately 615 psi, in some embodiments) may cause mechanical failure, including prefailure events, such as excessive wear on parts. High pressures may also trip safety systems designed to prevent overpressure. If air conditioner operation is allowed when the pressure exceeds a predetermined operational maximum (e.g., greater than approximately 615 psig and/or greater than approximately 620 psig for R410A, in some embodiments), mechanical failure events may occur. For example, mechanical failure events, including pre-failure events, may include wear on parts, damage to lines, damage to seals, and/or damage to components. Startup of HVAC systems can provide unique pressure problems as well. HVAC systems may have startup problems with microchannel condensers because of the refrigerant storage imbalance between a microchannel condenser and round tube flat fin coil evaporators. If the microchannel tube port size is too small, the HVAC system start up problem may be elevated. Various condenser and evaporator types and geometries can cause pressure spike or buildup problems.
Embodiments of an HVAC system as described in the present disclosure can provide a system and method for relieving pressure buildup within an HVAC system, during operation or upon startup. The present disclosure can be adapted to various condenser, evaporator and HVAC system types.
In a typical prior art system, refrigerant passes through an evaporator, pulling heat from surrounding air, and evaporating the refrigerant to gas form. Then the gas can be compressed in a compressor before passing through a condenser. As gas refrigerant passes through a condenser it loses heat to the surrounding air, leaving the refrigerant again in liquid form. The refrigerant then flows through an expansion device to the evaporator. In some embodiments, the evaporator is located within a room or building, creating a cooling effect (an air conditioner). Other embodiments may place the condenser inside a room or building, creating a warming effect (a heat pump).
Referring to
The embodiment shown in
In some implementations, the condenser may be a microchannel condenser. A microchannel condenser may include channels less than approximately 1 mm. The channels of the microchannel condenser may have a cross-sectional area similar to a rectangle, an oval, and/or any other appropriate shape. A microchannel condenser may increase the efficiency and/or decrease energy consumption of an air conditioner (e.g., when compared to an air conditioner with a condenser with a tubing diameter greater than 5 mm). A microchannel condenser may be able to operate with less refrigerant (e.g., when compared to an air conditioner with a condenser with a tubing diameter greater than 5 mm).
In some implementations, a part of the refrigerant may flow through the bypass line (elements 68, 58, 158 from
The sensors 256, 266 may detect other properties of the air conditioning system 200. For example, the sensor 256, 266 may detect properties such as temperature, pressure, and/or other appropriate properties. The sensor 256, 266 may detect the property at various positions in lines and/or components of the air conditioning system. For example, the sensors 256, 266 may detect a property (e.g., temperature and/or pressure) such as an ambient temperature (e.g., a temperature proximate the condenser). The sensors 256, 266 may also be disposed at a plurality of other locations within system 200.
In keeping with the teachings of the present disclosure, a high pressure switch can be located at any suitable location within an HVAC system. For example, the high pressure switch may be disposed proximate an outlet of the compressor, and/or proximate an outlet of the condenser.
In some implementations, when the air conditioner includes a condenser that it not a microchannel condenser, high pressures (e.g., greater than predetermined maximum and/or predetermined operational maximum) may not occur (e.g., during high ambient temperature operations) due to the smaller capacity difference between the condenser and the evaporator (e.g., when compared to the capacity difference between a microchannel condensers and an evaporator). But the teachings of the present disclosure can still be used for non-microchannel implementations.
If the pressure reading exceeds a predetermined maximum, flow through the bypass line may be allowed. For example, the controller may transmit a signal to a valve disposed in the bypass line. The valve may at least partially open if the property reading exceeds the predetermined maximum property. In some implementations, the amount of refrigerant allowed to flow through the bypass line may be based at least partially on the degree of openness of the valve. The amount of refrigerant allowed to flow through the bypass line may be based on the size of the bypass line. Allowing fluid flow through the bypass line may reduce a pressure of at least a part of the high pressure portion of the air conditioner. If the property reading does not exceed the predetermined maximum property, flow through the bypass line may be restricted. For example, a valve disposed in the bypass line may be closed if the property reading is does not exceed the predetermined maximum property.
A determination may be made whether a pressure reading exceeds a predetermined maximum pressure reading. For example, a predetermined maximum pressure reading may be retrieved from a memory of the air conditioner and/or controller. The pressure reading and the predetermined reading may be compared (e.g., by a processor of the controller of the air conditioner, by a valve controller, and/or by the sensor). In some implementations, the pressure reading may be a pressure differential across the compressor and the predetermined maximum pressure differential across the compressor may be 460 psi for R410A. The pressure reading may be an absolute pressure and the predetermined maximum pressure may be 600 psig. For example, a pressure of refrigerant in a line may be a measured pressure reading and the associated predetermined maximum pressure reading may be 600 psig. In some implementations, the predetermined maximum pressure may be a preselected amount (e.g., 10 psi, 15 psi, and/or 20 psi) less than the maximum operational pressure (e.g., the pressure at which a high pressure switch restricts operation of at least a portion of the air conditioning system to inhibit mechanical failure of the system). The predetermined maximum pressure may be selected such that operation of the high pressure switch may be avoided when using the bypass line.
In some implementations, in an air conditioner that includes a microchannel condenser, as the ambient temperature becomes elevated (e.g., ambient temperatures greater than 125 degrees Fahrenheit and/or 116 degrees Fahrenheit), the pressure in the microchannel condenser increases (e.g., due to the capacity differences between the evaporator and the microchannel condenser). A sensor can be disposed proximate at least a portion of the condenser and may measure the pressure (e.g., pressure reading). As the pressure (e.g., inlet, outlet, differential, and/or average) of the microchannel increases, the likelihood of mechanical failure increases, and so a high pressure switch may operate at a predetermined activation pressure (e.g., a maximum operational pressure) to inhibit mechanical failure of the air conditioner. For example, the high pressure switch may restrict operation of one or more components of the air conditioner (e.g., compressor) and/or open a vent. The predetermined maximum pressure may be determined based on the high pressure switch activation pressure, in some implementations. For example, the predetermined maximum pressure may be a predetermined amount less than the maximum operational pressure (e.g., the predetermined maximum pressure may be approximately 15 to approximately 20 psi less than the predetermined maximum operational pressure). The measured pressure may be compared to the predetermined maximum pressure to determine whether to allow a part of the refrigerant to be diverted to the bypass line. When the measured pressure exceeds the predetermined maximum pressure, a valve coupled to the sensor may open and allow refrigerant to flow through the bypass line. The bypass may reduce the pressure and/or inhibit pressures in the microchannel condenser from elevating to the activation pressure. When the measured pressure does not exceed the predetermined maximum pressure, fluid flow through the bypass line may be restricted (e.g., by the valve coupled to the sensor). For example, the bypass line may be utilized to reduce the pressure, when needed to control pressure in the microchannel condenser and/or to inhibit mechanical failure. When the pressure of the microchannel condenser is within operational parameters (e.g., less than the predetermined maximum pressure and/or predetermined maximum operational pressure), the fluid flow through the bypass line may be restricted to increase efficiency of the system and/or control of pressure within the evaporator.
Although various implementations have been described in terms of pressure and pressure sensors, other properties may be utilized in the various systems and/or processes. For example, a temperature sensor may be utilized. Temperatures, such as ambient temperature may be measured by sensors and the valve in the bypass line may operate based on the measured temperature. Although a valve coupled to the bypass line that opens to allow fluid flow through the bypass line has been described, other valve configurations may be allowed as appropriate. For example, a three way valve coupled to the junction between the bypass line and the high pressure portion and/or low pressure portion, may direct fluid flow.
In some implementations, ambient temperature may include a temperature proximate the high pressure portion, a temperature proximate the condenser, and/or a temperature proximate a condenser fan. For example, ambient temperature may include a measure of the temperature of the air proximate an outdoor portion (e.g., a condenser) of an air conditioning system. As another example, ambient temperature may include a measure of the temperature of a fluid removing heat from the refrigerant in the condenser. Temperature measurements may cause an adjustment to the maximum allowed pressure, depending on the properties of the refrigerant used, or other factors.
In some implementations, a pressure across a line coupling components may be substantially constant. For example, a pressure drop across a line coupling components may be less than approximately 5 percent. As an example, a pressure proximate an inlet of a high pressure portion and/or condenser may be substantially equal to the pressure proximate an outlet of a compressor. A sensor measuring a pressure in a line may not substantially affect the pressure. In some implementations, a pressure across the high pressure portion and/or the pressure across the low pressure portion may be substantially constant. For example, a pressure drop across the high pressure portion may be less than approximately 5 percent. The pressure drop across the low pressure portion may be less than approximately 5 percent.
Although an expansion valve has been described, any appropriate metering device may be utilized to control fluid flow into the evaporator. For example, a thermal expansion valve may be utilized.
Although an operation of the cycle is described where cool air is provided to a location by the evaporator which is the indoor coils, the cycle may be reversed such that hot air is provided to a location by the indoor coils. For example, heat may transfer from refrigerant in the indoor coils to the air from the indoor blower.
In some implementations, the air conditioning system may include a controller. The control device for the bypass valve may be a portion of the controller and/or separate from the controller. A controller may be coupled to various components of the air conditioning system. For example, the controller may be communicably coupled to an evaporator, an evaporator blower, a compressor, a condenser, a condenser fan, bypass line, sensor, high pressure switch, control device of the sensor, valve, and/or thermal expansion valve. The controller may be a computer or other programmable logic device. The controller may include a processor that executes instructions and manipulates data to perform operations of the controller and a memory. The processor may include a programmable logic device, a microprocessor, or any other appropriate device for manipulating information in a logical manner and memory may include any appropriate form(s) of volatile and/or nonvolatile memory, such as a repository. A memory may include data, such as predetermined maximum operating properties (e.g., temperatures and/or pressures), activation pressures, predetermined maximum properties (e.g., temperatures and/or pressures), periods of time that operations should run, and/or any other data useful to the operation of the air conditioner. In addition, various types of software may be stored on the memory. For example, instructions (e.g., operating systems and/or other types of software), an operation module, a bypass operation module, and/or a high pressure switch module may be stored on the memory. The operation module may operate the air conditioner during normal operations (e.g., operations based at least partially on requests for operation from a user, operations in which flow though the bypass is restricted). The bypass operation module may measure and/or monitor properties of the air conditioning system, retrieve data (e.g., predetermined operational maximums and/or predetermined maximum values), compare data to monitored properties, determine whether to open and/or close a bypass line, etc. A high pressure switch module may measure and/or monitor properties, such as pressure, retrieve data (e.g., predetermined operational maximum), compare monitored properties to retrieved data, and/or determine an appropriate action based on the retrieved data (e.g., restrict operation of one or more components of the air conditioner and/or allow normal operations).
A communication interface may allow the controller to communicate with components of the air conditioner, other repositories, and/or other computer systems. The communication interface may transmit data from the controller and/or receive data from other components, other repositories, and/or other computer systems via network protocols (e.g., TCP/IP, Bluetooth, and/or Wi-Fi) and/or a bus (e.g., serial, parallel, USB, and/or FireWire).
The controller may include a presentation interface to present data to a user. For example, to provide for interaction with a user, the systems and techniques described here can be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a track pad) by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user by an output device can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input. The controller may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. A client may allow a user to access the controller and/or instructions stored on the controller. The client may be a computer system such as a personal computer, a laptop, a personal digital assistant, a smart phone, or any computer system appropriate for communicating with the controller. These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the term “machine-readable medium” refers to any computer program product, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and/or data to a programmable processor.
Although users have been described as a human, a user may be a person, a group of people, a person or persons interacting with one or more computers, and/or a computer system. Various implementations of the systems and techniques described here can be realized in digital electronic circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to a storage system (e.g., repository), at least one input device, and at least one output device.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
