Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
  • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
  • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
  • F24F3/153—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification with subsequent heating, i.e. with the air, given the required humidity in the central station, passing a heating element to achieve the required temperature

Definitions

• This invention relates to a refrigerant system wherein a closed-loop dehumidification circuit is incorporated into a system schematic.
• Refrigerant systems are utilized to control the temperature and humidity of air in various indoor environments to be conditioned.
• a refrigerant is compressed in a compressor and delivered to a condenser (or an outdoor heat exchanger in this case).
• heat is exchanged between outside ambient air and the refrigerant.
• the refrigerant passes to an expansion device, at which the refrigerant is expanded to a lower pressure and temperature, and then to an evaporator (or an indoor heat exchanger in this case). In the evaporator, heat is exchanged between the refrigerant and the indoor air, to condition the indoor air.
• the evaporator cools the air that is being supplied to the indoor environment.
• moisture usually is also taken out of the air. In this manner, the humidity level of the indoor air can also be controlled.
• the temperature level, to which the air is brought to provide comfort in a conditioned space may need to be higher than the temperature that would provide the ideal humidity level.
• One way to address such challenges is to utilize various schematics incorporating reheat coils.
• the reheat coils, placed in the indoor air stream behind the evaporator are employed for the purpose of reheating the air supplied to the conditioned space after it has been cooled in the evaporator, and where the moisture has been removed.
• reheat circuits require connections to the main refrigerant loop associated with specific flow control devices.
• flow control devices such as three-way valves, check valves or other valve systems, may need additional control functionality and frequently present reliability and refrigerant migration issues.
• the refrigerant would migrate to a coldest spot within a refrigerant system. The coldest spot will change depending on the mode of operation. In the conventional cooling mode, the refrigerant would naturally migrate to the non-functioning reheat coil and, in a reheat mode, the opposite phenomenon would typically take place.
• This refrigerant re-distribution within the refrigerant system affects amount of the refrigerant flowing through the main refrigerant loop that in turn may cause serious system malfunctioning and reliability issues.
• a reheat loop is closely coupled to a main refrigerant circuit the system control for both the reheat function and conventional cooling becomes more complicated than would be desirable. In other words, this complexity arises from the fact that the refrigerant is essentially shared between the main refrigerant loop and the reheat circuit.
• Another issue related to the reheat concepts employing main circuit refrigerant is associated with the fact that refrigerant system operational flexibility is compromised. Consequently, it becomes extremely difficult to satisfy a wide range of operational and environmental conditions and potential applications.
• a closed-loop reheat circuit is utilized in conjunction with a main refrigerant system.
• the closed-loop reheat circuit includes a pair of heat exchangers, with a reheat heat exchanger providing an effective reheat function by being placed in the path of at least a portion of the airflow having passed over the evaporator.
• this reheat heat exchanger will tend to reheat the air, such that the air can be cooled below its desired comfort temperature in the evaporator to remove an adequate amount of moisture and thus to provide a comfortable humidity level.
• the air then passes over the reheat heat exchanger, at which its temperature is increased to achieve a desired temperature set by an occupant of an environment to be conditioned.
• heat is transferred from refrigerant to air to reheat the air.
• the other heat exchanger is an auxiliary heat exchanger where, due to heat transfer interaction, the refrigerant in the closed-loop reheat circuit cools the refrigerant in the main refrigerant circuit.
• the auxiliary heat exchanger heat is transferred from the main circuit refrigerant to the refrigerant circulating through the reheat loop. Therefore, the refrigerant in the closed-loop reheat circuit is heated, while the refrigerant in the main refrigerant circuit will have an increased cooling potential when it reaches the evaporator.
• the refrigerant in the closed-loop reheat circuit leaves the auxiliary heat exchanger and returns to the reheat heat exchanger.
• a liquid pump is included to drive the refrigerant through the closed-loop reheat circuit.
• the liquid pump may be provided with a variable speed drive or an external flow control device such as an adjustable valve can be used to achieve variable refrigerant flow and consequently variable capacity in the reheat heat exchanger.
• the invention may be utilized with the option of bypassing at least a portion of refrigerant around the condenser to achieve a variable cooling potential in the evaporator.
• This control feature may be employed separately or in conjunction with a variable speed liquid pump or/and with adjustable reheat circuit valve.
• a refrigerant different from the refrigerant circulating through the main circuit is used in the closed-loop reheat circuit.
• the refrigerant composition in the reheat circuit can be formulated to sustain a liquid phase throughout the circuit or to change phases from vapor to liquid in the reheat heat exchanger and back from liquid to vapor in the auxiliary heat exchanger.
• a natural convection or thermosiphon is employed for refrigerant circulating through the reheat circuit in place of a forced fluid flow by the liquid pump. Obviously, in this embodiment refrigerant phase change would be required.
• Figure IA shows a first schematic of the present invention.
• Figure IB shows an alternate schematic of the Figure IA schematic.
• Figure 2A shows a second schematic of the present invention.
• Figure 2B shows an alternate schematic of the Figure 2A schematic.
• Figure IA shows a refrigerant system 20 incorporating a compressor 22, compressing refrigerant and delivering it through a condenser 24.
• a fan 26 moves air over the condenser 24.
• Refrigerant flow through a bypass line 28 is controlled by a flow control device such as a valve 30.
• Another optional valve 25 may be positioned upstream of the condenser 24 (but downstream of the diversion point of the bypass line 28) to assist in refrigerant routing through the condenser 24 and bypass line 28.
• a control 21 can control the valves 30 and 25 to selectively bypass at least a portion of the refrigerant around the condenser 24.
• Such a bypass will typically be utilized when full cooling capacity of the refrigerant system 20 in the reheat mode of operation is not required.
• the two refrigerant flows mentioned above are combined downstream of the condenser 24.
• the control 21 controls other components of the refrigerant system 20 such as the compressor 22 and fans 26 and 48.
• An auxiliary heat exchanger 32 is positioned on a liquid refrigerant line downstream of the condenser 24.
• An expansion device 34 is positioned downstream of the auxiliary heat exchanger 32, and an evaporator 36 is located downstream of the expansion device 34.
• the refrigerant in the main circuit of the refrigerant system 20 flows through the auxiliary heat exchanger 32, through the expansion device 34 to the evaporator 36 and then is returned to the compressor 22.
• a closed-loop reheat circuit 38 is also incorporated into the refrigerant system
• the refrigerant in the closed-loop reheat circuit flows through a reheat heat exchanger 42.
• a fan 48 blows air over the evaporator 36, and then over the reheat heat exchanger 42.
• a reheat function allows the evaporator to be controlled to cool the air to a lower temperature than would be desired by an environment into which the air is being delivered. This permits the removal of an adequate amount of moisture (significantly more than might otherwise be available given the desired temperature) and thus to provide a comfortable humidity level in an environment to be conditioned.
• the refrigerant in the reheat heat exchanger 42 reheats this air, such that when the air approaches the environment to be conditioned, it will be at the desired temperature. During this heat transfer interaction in the reheat heat exchanger 42, the heat is transferred from the refrigerant in the reheat loop to the conditioned air.
• a liquid pump 44 circulates the refrigerant through the closed-loop reheat circuit 38 from the reheat heat exchanger 42, through an optional flow control device such as valve 43, through the auxiliary heat exchanger 32 and then returns it back to the reheat heat exchanger 42.
• the heat is transferred from the refrigerant in the reheat circuit to the conditioned air
• the auxiliary heat exchanger 32 the heat is transferred from the refrigerant in the main circuit to the refrigerant in the reheat circuit (in this case, to cool the refrigerant in the main circuit).
• the preferred flow configuration in the auxiliary heat exchanger 32 is a counterflow arrangement.
• the refrigerant flow in the reheat circuit can be controlled independently by the system control 21 through the adjustable valve 43 or by a variable speed drive 46 for the liquid pump 44. Therefore, the reheat capacity can be controlled.
• a variable flow of the reheat circuit refrigerant circulating through the heat exchangers 32 and 42 can be utilized in conjunction with the control 21 controlling the bypass valve 30 and valve 25 to achieve a desired temperature of the air leaving the reheat heat exchanger 42 and supplied to the conditioned space.
• the valves 30 and 25 will control the amount of sub-cooling of the refrigerant entering the auxiliary heat exchanger 32 and consequently, to a great extent, its cooling potential in the downstream evaporator. For instance, if humidity control with lower cooling is desired, then, as is known, the amount of refrigerant bypassing the condenser 24 is increased.
• the reheat circuit subsystem consisting of the liquid pump 44 and upstream valve 43 could be also placed upstream of the reheat heat exchanger 42 (downstream of the auxiliary heat exchanger 32). In this case, the refrigerant flowing through the entire reheat circuit 38 has to be in a liquid phase. This position is illustrated in phantom at X.
• the refrigerant in the reheat circuit can undergo phase transformation and change from liquid to vapor in the auxiliary heat exchanger 32 and from vapor to liquid in the reheat heat exchanger 42.
• an additional expansion device may be required, and the cavitation conditions at the entrance to the liquid pump 44 should be prevented to ensure reliable operation.
• the refrigerant in the reheat circuit may be different in nature, have different constituents and/or composition and may have substantially different operating parameters (such as pressure, controlled by the refrigerant charge).
• FIG. IB Another schematic 120 shown in Figure IB has the auxiliary heat exchanger 132 positioned upstream of the condenser 24 in the main refrigerant circuit.
• heat transfer interaction in the auxiliary heat exchanger 132 is between the refrigerant in the reheat circuit 138 and a discharge line refrigerant vapor (in comparison to a liquid line refrigerant in Figure IA).
• a reheat circuit expansion device 47 may be required if the reheat circuit refrigerant changes phases (between liquid and vapor), and a liquid refrigerant state is to be maintained at the entrance of the liquid pump 44 to prevent cavitation.
• this embodiment is identical to the Figure IA embodiment.
• FIG. 2A Another embodiment 50 is shown in Figure 2A, wherein the forced flow of refrigerant in the reheat circuit 38 provided by the liquid pump 44 of Figures IA and IB is substituted by the natural convection phenomenon or so-called thermosiphon action. Therefore, in this case, a liquid pump 44 is not anymore required, but, for this concept to function properly, the refrigerant in the reheat circuit should change phases between liquid and vapor.
• a closed-loop reheat circuit 52 incorporates a shutoff valve 54, the auxiliary heat exchanger 32, and a reheat heat exchanger 58. As before, the reheat heat exchanger 58 is placed in the path of at least a portion of airflow blown by a fan 56 over the evaporator 36.
• the refrigerant within the reheat circuit 52 circulates due to the force of gravity.
• the refrigerant condenses in the reheat heat exchanger 58 and naturally flows down due to the force of gravity.
• This refrigerant then gets drawn to the auxiliary heat exchanger 32 where it evaporates and raises due to the density difference. Then the refrigerant, once again, enters the reheat heat exchanger 58 and the cycle repeats itself. In this manner, natural circulation is accomplished throughout the reheat circuit 52.
• FIG. 2B Another embodiment 150 is shown in Figure 2B. This embodiment is analogous to the embodiment 50, with the exception that the reheat heat exchanger 158 utilizes refrigerant vapor in the discharge line of the main circuit as a source of heat for the refrigerant in the reheat circuit 152.
• the present invention provides the reheat function as a separate closed-loop circuit decoupled form the main refrigerant circuit.
• a control of such a system is less complex and more flexible than the control for a refrigerant system that selectively taps refrigerant from the main refrigerant circuit to provide the reheat function.
• the control and operation of the known systems is less reljable and frequently needs additional components due to changing environmental conditions and refrigerant migration issues.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Air Conditioning Control Device (AREA)
• Other Air-Conditioning Systems (AREA)
• Compression-Type Refrigeration Machines With Reversible Cycles (AREA)

Applications Claiming Priority (1)

Publications (2)

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• 2005
  • 2005-07-28 US US11/995,142 patent/US20080202155A1/en not_active Abandoned
  • 2005-07-28 EP EP05777509A patent/EP1915580A4/de not_active Withdrawn
  • 2005-07-28 CN CN2005800512210A patent/CN101443608B/zh not_active Expired - Fee Related
  • 2005-07-28 WO PCT/US2005/027090 patent/WO2007018524A2/en not_active Ceased
  • 2005-07-28 CA CA2615781A patent/CA2615781C/en not_active Expired - Fee Related

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