A FLASH TANK FOR AN HVAC SYSTEM

BACKGROUND

[0001]The present disclosure relates generally to HVAC systems.

[0002]An HVAC system, for example a chiller, includes a flash tank disposed between an evaporator and a condenser. The flash tank receives refrigerant as a condensate from the condenser and facilitates partial evaporation of the condensate to form a vapor refrigerant and a liquid refrigerant within the flash tank. The vapor refrigerant is extracted from the flash tank and conveyed to a compressor. The liquid refrigerant from the flash tank is conveyed to the evaporator. Size of the flash tank is related to mass flow rate of vapor produced in the flash tank. As mass flow rate or capacity of the flash tank increases, size of flash tank also increases making it difficult to be accommodated in an HVAC system.

[0003]A typical flash tank has a vertical shell that allows partial evaporation of the condensate therewithin. However, such flash tanks possess certain drawbacks. One of the major drawbacks is liquid carryover. In conventional vertical flash tanks, upward velocity of vapor within the shell may be higher due to limited internal diameter of the shell. Due to this, vapor tends to carry liquid droplets as vapor moves upward in the shell. This is termed as liquid carryover. Along with vapor, liquid droplets may escape out of the shell. Liquid droplets mixed with vapor may damage internal components of the compressor as vapor extracted from the flash tank is conveyed to the compressor. Further, the liquid carryover results in decrease in amount of liquid refrigerant being extracted from the flash tank. This causes reduction in efficiency of the refrigeration system.

[0004]Therefore, there is felt a need of a flash tank that alleviates aforementioned drawbacks of conventional flash tanks.

SUMMARY

[0005]The present disclosure discloses a flash tank for housing one or more flashing units. The one or more flashing unit comprises an inner shell, an outer shell maintaining a gap with the inner shell, and one or more inlets to direct flow of refrigerant through the gap to aid partial evaporation of the refrigerant. Preferably, the gap is sealed at top.

[0006]In some embodiments, the inner shell is hollow to allow passing of vapor refrigerant. The flashing unit may include a restrictor placed in the inner shell to minimize liquid refrigerant carryover. The restrictor comprises a restricting member and an end plate. The restricting member is attached to an inner surface of the inner shell and extends beyond the inner shell in a downward direction. The end plate is connected to the restricting member.

[0007]Preferably, the inner shell is shorter than the outer shell.

[0008]In some embodiments, the flash tank includes a horizontal housing. The flashing units are placed vertically in the housing.

[0009]In some embodiments, the flash tank includes one or more baffles arranged within the housing. The one or more baffles may be connected to the one or more flashing units. The one or more baffles are connected to the flashing unit and an eliminator in some other embodiments.

[0010]In accordance with another aspect, the flash tank comprises a horizontal housing and one or more vertical flashing units provided within the horizontal housing to at least partially evaporate refrigerant and separate vapor refrigerant from liquid refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]Various objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by referring to the detailed description taken in conjunction with the accompanying drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.

[0012]FIG. 1 is a perspective view of a building including a heating, ventilating, or air conditioning (HVAC) system, according to some embodiments.

[0013]FIG. 2 is an isometric view depicting a flash tank, according to one aspect of the present disclosure.

[0014]FIG. 3 is a side view of the flash tank of FIG. 2, according to some embodiments.

[0015]FIG. 4 is a front view of the flash tank of FIG. 2, according to some embodiments.

[0016]FIG. 5 is an isometric view of flashing units of the flash tank, according to some embodiments.

[0017]FIG. 6 is a top view of the flashing unit.

[0018]FIG. 7 is a sectional view of the flash tank of FIG. 2, according to some embodiments.

[0019]FIG. 8 is another sectional view of the flash tank of FIG. 2, according to some embodiments.

[0020]FIG. 9 is an isometric view depicting a flash tank, according to another aspect of the present disclosure.

[0021]FIG. 10 is a top view of the flash tank of FIG. 9, according to some embodiments.

[0022]FIG. 11 is a side view of the flash tank of FIG. 9, according to some embodiments.

[0023]FIG. 12 is a bottom view of the flash tank of FIG. 9, according to some embodiments.

[0024]FIG. 13 is a front view of the flash tank of FIG. 9, according to some embodiments.

DETAILED DESCRIPTION

[0025]One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0026]When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

Building HVAC System

[0027]Referring now to FIG. 1, a perspective view of a building 10 is shown. Building 10 is served by a heating, ventilating, or air conditioning (HVAC) system 100. HVAC system 100 can include a plurality of HVAC devices (e.g., heaters, chillers, air handling units, pumps, fans, thermal energy storage, etc.) configured to provide heating, cooling, air conditioning, ventilation, and/or other services for building 10. For example, HVAC system 100 is shown to include a waterside system 120 and an airside system 130. Waterside system 120 may provide a heated or chilled fluid to an air handling unit of airside system 130. Airside system 130 may use the heated or chilled fluid to heat or cool an airflow provided to building 10.

[0028]HVAC system 100 is shown to include a chiller 102, a boiler 104, and a rooftop air handling unit (AHU) 106. Waterside system 120 may use boiler 104 and chiller 102 to heat or cool a working fluid (e.g., water, glycol, etc.) and may circulate the working fluid to AHU 106. In various embodiments, the HVAC devices of waterside system 120 can be located in or around building 10 (as shown in FIG. 1) or at an offsite location such as a central plant (e.g., a chiller plant, a steam plant, a heat plant, etc.) that serves one or more buildings including building 10. The working fluid can be heated in boiler 104 or cooled in chiller 102, depending on whether heating or cooling is required in building 10. Boiler 104 may add heat to the circulated fluid, for example, by burning a combustible material (e.g., natural gas) or using an electric heating element. Chiller 102 may place the circulated fluid in a heat exchange relationship with another fluid (e.g., a refrigerant) in a heat exchanger (e.g., an evaporator) to absorb heat from the circulated fluid. The working fluid from chiller 102 and/or boiler 104 can be transported to AHU 106 via piping 108.

[0029]AHU 106 may place the working fluid in a heat exchange relationship with an airflow passing through AHU 106 (e.g., via one or more stages of cooling coils and/or heating coils). The airflow can be, for example, outdoor air, return air from within building 10, or a combination of both. AHU 106 may transfer heat between the airflow and the working fluid to provide heating or cooling for the airflow. For example, AHU 106 can include one or more fans or blowers configured to pass the airflow over or through a heat exchanger containing the working fluid. The working fluid may then return to chiller 102 or boiler 104 via piping 110. The function of boiler 104 and chiller 102 may be replaced by a heat pump, which not only can make chilled water but also hot water.

[0030]Airside system 130 may deliver the airflow supplied by AHU 106 (i.e., the supply airflow) to building 10 via air supply ducts 112 and may provide return air from building 10 to AHU 106 via air return ducts 114. In some embodiments, airside system 130 includes multiple variable air volume (VAV) units 116. For example, airside system 130 is shown to include a separate VAV unit 116 on each floor or zone of building 10. VAV units 116 can include dampers or other flow control elements that can be operated to control an amount of the supply airflow provided to individual zones of building 10. In other embodiments, airside system 130 delivers the supply airflow into one or more zones of building 10 (e.g., via supply ducts 112) without using intermediate VAV units 116 or other flow control elements. AHU 106 can include various sensors (e.g., temperature sensors, pressure sensors, etc.) configured to measure attributes of the supply airflow. AHU 106 may receive input from sensors located within AHU 106 and/or within the building zone and may adjust the flow rate, temperature, or other attributes of the supply airflow through AHU 106 to achieve setpoint conditions for the building zone.

A Flash Tank for an HVAC System

[0031]The present disclosure further discloses a flash tank that can be employed in an HVAC system. The flash tank comprises a housing and one or more flashing units in the housing. In some embodiments, the flashing units may be defined within the housing. In some other embodiments, the flashing units may be provided in the housing as separate units.

[0032]The flashing units include an inner shell and an outer shell arranged such that a gap is defined between the inner shell and the outer shell. One or more inlets are provided on the flashing unit to direct flow of refrigerant through the gap for aiding partial evaporation of the refrigerant. the flashing unit assist in separating vapor from liquid refrigerant. The flash tank of the present disclosure minimizes liquid carryover and make the flash tank be compact.

[0033]The flash tank of the present disclosure is now described in detail with reference to accompanying FIGS. 2-13.

[0034]Referring to FIGS. 2-4, a flash tank 200 is shown in accordance with one aspect of the present disclosure. The flash tank 200 includes a housing 210 for housing one or more flashing units. The housing 210 can have any suitable shape, size and configuration. In one example, the housing 210 may have a cylindrical shape with horizontal orientation as shown in FIG. 2. The housing 210 has a vapor outlet 220 and a liquid outlet 230. The vapor outlet 220 is provided at substantial upper portion of the housing 210, whereas the liquid outlet 230 is provided at substantial lower portion of the housing 210. The liquid outlet 230 may be in fluid communication with a conduit 240 for carrying liquid refrigerant out of the housing 210.

[0035]One or more flashing units 250 are disposed within the housing 210. Although accompanying figures depict two flashing units, the present disclosure is not limited to two flashing units and the flash tank of the present disclosure can have one or more than two flashing units in other embodiments. The flashing units 250 are placed vertically in the housing 210.

[0036]The housing 210 may include an eliminator 260 provided between the vapor outlet 220 and the flashing units 250. More specifically, the eliminator 260 is provided below the vapor outlet 220 and above the flashing units 250 to prevent liquid droplets of refrigerant from reaching the vapor outlet 220. The eliminator 260 allows vapor refrigerant to pass through it but prevents liquid droplets from passing through it. The eliminator 260 can have any suitable configuration. In some embodiments, the eliminator 260 may include a diffuser plate having serrations configured on the diffuser plate. In some other embodiments, the eliminator 260 may include a filter and the diffuser plate placed on the filter. The eliminator 260 is attached to an inner surface of the housing 210 using any suitable attaching means.

[0037]The flashing units 250 are provided to at least partially evaporate refrigerant and separate vapor refrigerant from liquid refrigerant. The flashing unit 250 is now described in detail with reference to FIGS. 5-6. It is to be noted that each flashing unit of the present disclosure can have same configuration as described in following paragraphs or at least one flashing unit of the present disclosure can have the following configuration. In some embodiments, out of all flashing units in the housing, one or more flashing units can have same configuration as described in following paragraphs and remaining flashing units may have different configuration than the configuration described below.

[0038]The flashing unit 250 comprises an inner shell 270 and an outer shell 280. The inner shell 270 and the outer shell 280 are arranged such that a gap 290 is maintained between the inner shell 270 and the outer shell 280. The shells 270, 280 can have any suitable configuration. In some embodiments, the shells 270, 280 have a cylindrical shape, wherein the outer shell 280 covers the inner shell 270. Preferably, the gap 290 is sealed at top with a sealing member 300. In one example, the sealing member 300 can be a circular plate having a central hole of diameter equal to diameter of the inner shell 270. The inner shell 270 and the outer shell 280 extend downwards from the sealing member 300.

[0039]The flashing unit 250 comprises one or more inlets 310 for directing flow of refrigerant through the gap 290 to aid at least partial evaporation of the refrigerant. Although accompanying figures show single inlet 310, the flash tank 250 can have more than one inlet in other embodiments of the present disclosure. The inlet 310 is in fluid communication with the gap 290. The inlet 310 may include a conduit 320 that is in fluid communication with an HVAC equipment, for an example, a condenser, to receive refrigerant. The conduit 320 may pass from the flashing unit 250 to out of the housing 210 through a body of the housing 210. The inlet 310, more specifically the conduit 320, is tangential to the outer shell 280. Due to tangential connection between the inlet 310 and the outer shell 280, refrigerant undergoes swirling motion while passing through the gap 290. More specifically, refrigerant enters the flashing unit 250 through the inlet 310. Further, the refrigerant passes through the gap 290. As the gap 290 is circular in shape, refrigerant undergoes swirling motion when it passes through the gap 290. Configuration of the gap 290, the inner shell 270, and the outer shell 280 facilitate at least partial evaporation of refrigerant forming a vapor refrigerant and liquid refrigerant. Further, the flashing unit 250 also facilitate separation of vapor refrigerant from liquid refrigerant.

[0040]In some embodiments, the inner shell 270 is shorter than the outer shell 280. More specifically, the outer shell 280 extends beyond the inner shell 270 in vertically downward direction. Further, the inner shell 270 is hollow defining a passage 330. The refrigerant passing through the gap 290 can move either radially outwards or inwards of the flashing unit 250. As the inner shell 270 is shorter than the outer shell 280, vapor refrigerant passes through the passage 330. Liquid refrigerant exits the gap 290 through bottom portion thereof and is accumulated at bottom of the housing 210. Liquid refrigerant can be extracted from the housing 210 through the liquid outlet 230 and the conduit 240.

[0041]When vapor is passing through the passage 330, vapor may carry liquid droplets along with it through the passage 330. To minimize this liquid carryover, the flashing unit 250 includes a restrictor placed in the passage 330. The restrictor prevents swirling of the vapor in the passage 330 and thus, minimizes liquid carryover. The restrictor may have any suitable configuration for preventing liquid droplets to travel with vapor through the passage 330. In some embodiments, the restrictor comprises a restricting member 340 attached to an inner surface of the inner shell 270 using suitable attaching means. In some embodiments, the restricting member 340 may be welded to the inner shell 270. The restricting member 340 may extend beyond the inner shell 270 in a downward direction. The restricting member 340 can have a cross-shaped configuration or any other suitable configuration. The restrictor may include an end plate 350 connected to the restricting member 340. The end plate 350 prevents vapor refrigerant from mixing with liquid refrigerant present below the plate 350, thereby minimizing liquid carryover.

[0042]The end plate 350 can be integrally formed with the restricting member 340 or can be attached to the restricting member 340. The refrigerant exiting the gap 290 encounters with the end plate 350, wherein liquid refrigerant is directed towards bottom of the housing 210 and most of vapor refrigerant, being lighter than the liquid refrigerant, passes through the passage 330 and rises up in the housing 210, however some of the vapor can rise up through the space between the outer shell 280 and the housing 210. Further, the vapor refrigerant passes through the eliminator 260, wherein liquid droplets are separated from vapor. Vapor refrigerant is then extracted from the flash tank 200 via the vapor outlet 220. Liquid droplets separated in the eliminator 260 settle down in the housing 210.

[0043]In some embodiments, the end plate 350 may have a slope initiating from center of the plate 350 and reducing towards periphery of the end plate 350. The slope facilitates removal of liquid droplets from surface of the end plate 350 and directing droplets towards bottom of the housing 210.

[0044]Referring to FIGS. 7-8, the flash tank 200 further comprises one or more baffles 360 arranged within the housing 210 to minimize liquid carryover. When refrigerant exits through the gap 290, vapor refrigerant can move radially inwards or radially outwards. A first portion of vapor moving radially inwards towards center of the inner shell 270 passes through the passage 330. A second portion of vapor moving radially outwards rises up in the housing 210 and passes through the eliminator 260. The second portion of vapor may carry liquid droplets alongside. To minimize or prevent this liquid carryover, the flash tank 200 is provided with the baffles 360. In some embodiments, the baffle 360 is connected to the flashing unit 250. The flash tank 200 includes one or more supports 370, 380 provided to support the flashing units 250 within the housing 210. The supports may include a first support 370 and a second support 380 connected to the flashing unit 250 such that an opening 390 is defined between the supports 370, 380. The supports 370, 380 are further connected to an inner surface of the housing 210. The baffles 360 may be attached to the flashing unit 250 and/or the housing 210 at a level above the supports 370, 380 such that the baffle 360 covers the opening 390. This arrangement allows vapor to pass through the opening 390 and space between the baffle 360 and supports 370, 380, however, liquid droplets are restricted by the baffle 360. If vapor is carrying liquid droplets, the droplets are restricted from rising up with the vapor by the baffle 360.

[0045]Referring to FIGS. 9-13, another configuration of the flash tank 200 is shown. Common parts have been given like reference numerals, and a description thereof has been omitted unless there is a particular need. It is understood that description of common parts described in foregoing paragraphs applies to parts of FIGS. 9-13 unless it is specifically described

[0046]Referring to FIGS. 9-13, the flashing unit 250 includes two inlets 310a, 310b to receive the refrigerant and direct the refrigerant in the gap 290 (shown in FIG. 5). The inlets 310a, 310b may include conduits 410, 420. The conduits 410, 420 are in fluid communication with refrigerant source via a joint 400. The joint 400 can be a T-joint for directing refrigerant flow through the conduits 410, 420. Preferably, the inlets 310a, 310b are arranged diametrically opposite on the flashing unit 250. In some other embodiments, the inlets 310a, 310b can be arranged at any other suitable location on the flashing unit 250. It is to be noted that although the FIGS. 9-12 show the flashing unit 250 with two inlets, the present disclosure is not limited to two inlets and the flashing unit 250 can include more than two inlets in alternative embodiments of the present disclosure.

[0047]Although the FIGS. 9-12 show single flashing unit 250 with multiple inlets, the flash tank 200 may include more than one flashing unit having multiple inlets in other embodiments of the present disclosure.

[0048]In some embodiments, an eliminator 430 is arranged in the housing 210 between the vapor outlet 220 and the flashing unit 250. The eliminator 430 acts as a vertical partition dividing the housing 210 in two sections. In a first section 440, the flashing unit 250 is arranged, wherein the vapor outlet 220 is provided in a second section 450. The first section 440 and the second section 450 are defined side by side. In some embodiments, the eliminator 430 may include a knitted wire mesh. Typically, vapor passes through a substantial upper portion of the eliminator 430 to reach to the vapor outlet 220, whereas liquid refrigerant passes through a substantial lower portion of the eliminator 430. In case vapor has liquid droplets, the droplets are restricted to pass through the upper portion of the eliminator 430 due to wire mesh configuration and the droplets trickle down through the eliminator 430. As pressure in the first section 440 of the eliminator 430 is slightly higher than pressure in the second section 450, liquid refrigerant passes through the lower portion of the eliminator 430 and is accumulated in the second section 450.

[0049]In some other embodiments, the eliminator 430 may have similar configuration as that of the eliminator 260 or any other suitable configuration.

[0050]The flash tank 200 further includes one or more baffles 460 connected to the flashing unit 250 and the housing 210 and contact with the eliminator 430. In some embodiments, the baffle 460 can be welded to the housing 210. The baffle 460 creates a partition between vapor refrigerant and liquid refrigerant present in the first section 440 to prevent liquid carryover. The baffle 460 prevents vapor present above the baffle 460 to mix with liquid refrigerant present below the baffle 460.

[0051]Referring to FIGS. 12 and 13, the housing 210 includes an outlet 470 provided in a substantial lower portion of the housing. The outlet 470 is arranged in the second section 450. The outlet 470 may include a pipe 480 having an end 490 cut at a predetermined angle. The end 490 of the pipe 480 is provided in the housing 210 and remaining portion of the pipe 480 extends out of the housing 210. In some embodiments, the pipe 480 is arranged such that the end 490 extends up to a vertical line passing through the vapor outlet 220. Liquid refrigerant accumulated in the second section 450 enters the pipe 480 through the end 490. This may cause liquid refrigerant to swirl in the second section 450. Due to swirling, a portion of vapor present in the second section 450 may enter the pipe 480 through the end 490. To prevent this, the end 490 is cut at a predetermined angle so that an upper portion of the end 490 extends beyond a lower portion of the end 490 in a radial direction of the housing 210 to form a cover, thereby preventing vapor to enter the pipe 480.

Configuration of Exemplary Embodiments

[0052]The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements can be reversed or otherwise varied and the nature or number of discrete elements or positions can be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps can be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.

[0053]Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also, two or more steps can be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.