Water source heat pump with hot gas reheat

A refrigerant system selectively operable in a cooling mode, a reheat cooling mode, and a heating mode, includes a primary heat exchanger and a reheat heat exchanger that condition air for a room. In the cooling mode, the primary heat exchanger functions as an evaporator that cools the air, while the reheat heat exchanger is inactive. In the reheat cooling mode, the primary heat exchanger cools the air, and hot refrigerant in the reheat heat exchanger reheats the air to provide dehumidified air at or near room temperature. In the heating mode, the primary heat exchanger functions as a condenser that heats the air, while the reheat heat exchanger is inactive. When the reheat heat exchanger is inactive, a unique venting arrangement prevents the inactive heat exchanger from becoming flooded with liquid refrigerant.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The subject invention generally pertains to refrigerant systems and more
 specifically to refrigerant systems that provide a reheat function in a
 cooling mode.
 2. Description of Related Art
 Refrigerant systems operating in a normal cooling mode typically have a
 refrigerant evaporator that cools a stream of air that is delivered to a
 room or some other comfort zone. Once the room's temperature (i.e., dry
 bulb temperature) reaches its target temperature, the refrigerant system
 may stop running. At times, however, this may leave the room uncomfortably
 humid. Thus, in some cases, the system may continue operating to reduce
 the humidity even after the sensible cooling demand of the room has been
 met.
 To avoid over cooling the room in such cases, a heater downstream of the
 evaporator can be added to reheat the air after the evaporator cools and
 removes moisture from the air. Operating a refrigerant system in such a
 manner can be referred to as operating in a reheat cooling mode. In a
 reheat cooling mode, a refrigerant system can deliver relatively dry air
 to a room at a temperature close to its target temperature.
 Often the heater is an electric coil, which effectively reheats the air,
 but wastes electrical energy. As an alternative to electric heat, a
 refrigerant condenser conveying hot refrigerant can possibly reheat the
 air. However, such an approach may create problems when the refrigerant
 system operates in modes other than the reheat cooling mode.
 For example, when a refrigerant system with a reheat refrigerant condenser
 operates in a normal cooling mode without reheat, the inactive reheat
 condenser may flood with liquid refrigerant. The flooding may starve the
 rest of the system of its proper charge of refrigerant, thus reducing the
 system's overall efficiency in the normal cooling mode. Likewise, an
 inactive reheat condenser may flood and starve the rest of a refrigerant
 system when the system is operating in a heating mode to heat the comfort
 zone.
 SUMMARY OF THE INVENTION
 To provide a refrigerant system with a reheat cooling mode, it is an object
 of the invention to provide the system with an additional refrigerant
 condenser, which reheats the air that has been previously cooled by the
 system's evaporator.
 Another object of the invention is to vent a reheat heat exchanger to an
 evaporator of a refrigerant system that is operating in a normal cooling
 mode, thereby preventing the reheat heat exchanger from flooding with
 liquid refrigerant.
 Another object of the invention is to vent a reheat heat exchanger to an
 evaporator of a refrigerant system that is operating in a heating mode,
 thereby preventing the reheat heat exchanger from flooding with liquid
 refrigerant.
 Yet another object is to use a flow restriction to vent a reheat heat
 exchanger to an evaporator of a refrigerant system, whereby additional
 cooling is achieved as the refrigerant expands upon passing through the
 flow restriction.
 A further object of the invention is to provide a valve system that
 selectively reconfigures a refrigerant system in a normal cooling mode, a
 reheat cooling mode, and a heating mode.
 A still further object of the invention is to split the flow of refrigerant
 flowing from a reheat condenser into a major portion and a minor portion
 of refrigerant, wherein the major portion is directed toward a
 water-cooled condenser to expel an appreciable amount of heat to the
 water, whereby a refrigerant system operating in a reheat cooling mode can
 still provide an appreciable amount of latent cooling.
 Another object is to provide a refrigerant system with a check valve that
 allows deactivating a reheat heat exchanger when the system is operating
 in a normal cooling mode.
 Another object is to provide a refrigerant system with a check valve that
 allows deactivating a reheat heat exchanger when the system is operating
 in a heating mode.
 Yet, another object of the invention is to take the refrigerant discharging
 from a secondary heat exchanger and divide the refrigerant into two
 portions with one having a higher concentration of liquid than the other,
 so that the liquid portion can be directly flashed into an evaporator
 without having to first pass through a condenser.
 These and other objects of the invention are provided by a refrigerant
 system that includes an evaporator for cooling air and a reheat heat
 exchanger that reheats the air in a reheat cooling mode. The reheat heat
 exchanger actively heats the air in the reheat cooling mode, but is
 relatively inactive in a normal cooling mode. In the normal cooling mode,
 a flow restriction vents the inactive reheat heat exchanger to the
 evaporator to help prevent the reheat heat exchanger from flooding with
 liquid refrigerant.
 The present invention provides a refrigerant system using a refrigerant to
 transfer heat between air and a fluid, wherein the air is supplied to a
 comfort zone. The system comprises: a compressor adapted to compress and
 discharge the refrigerant; a fluid heat exchanger having a refrigerant
 passageway in heat transfer relationship with the fluid; a primary heat
 exchanger that places the refrigerant in heat transfer relationship with
 the air; a secondary heat exchanger exposed to the air; a primary
 refrigerant flow restriction that helps couple the primary heat exchanger
 to the fluid heat exchanger; a secondary refrigerant flow restriction that
 helps couple the primary heat exchanger to the secondary heat exchanger;
 and a flow divider having an inlet, a first outlet and a second outlet.
 The inlet is adapted to receive the refrigerant discharged from secondary
 heat exchanger, the first outlet is adapted to discharge a first portion
 of the refrigerant toward the primary heat exchanger and the second outlet
 is adapted to discharge a second portion of the refrigerant toward the
 refrigerant passageway of the fluid heat exchanger. The first portion has
 a greater concentration of refrigerant in a liquid state than the second
 portion.
 The present invention also provides a refrigerant system using a
 refrigerant to transfer heat between air and a fluid, wherein the air is
 supplied to a comfort zone. The system comprises a compressor adapted to
 compress and discharge the refrigerant; a fluid heat exchanger having a
 refrigerant passageway in heat transfer relationship with the fluid; a
 primary heat exchanger that places the refrigerant in heat transfer
 relationship with the air; a secondary heat exchanger exposed to the air;
 a primary refrigerant flow restriction that couples the primary heat
 exchanger to the fluid heat exchanger; a secondary refrigerant flow
 restriction that couples the primary heat exchanger to the secondary heat
 exchanger; and a reheat valve. The reheat valve is selectively operable in
 a normal mode and a reheat cooling mode and has a first outlet in
 refrigerant communication with the refrigerant passageway of the fluid
 heat exchanger, a second outlet in refrigerant communication with the
 secondary heat exchanger, and an inlet situated to receive compressed
 refrigerant from the compressor. With the reheat valve in the normal mode
 most of the refrigerant discharged from the compressor bypasses the
 secondary heat exchanger and the secondary refrigerant flow restriction
 and passes in series through the inlet of the reheat valve, the first
 outlet, the refrigerant passageway of the fluid heat exchanger, the
 primary refrigerant flow restriction, and the primary heat exchanger. With
 the reheat valve in the reheat cooling mode most of the refrigerant
 discharged from the compressor bypasses the secondary refrigerant flow
 restriction and passes in series through the inlet of the reheat valve,
 the second outlet, the secondary heat exchanger, the fluid heat exchanger,
 the primary refrigerant flow restriction, and the primary heat exchanger.
 The present invention further provides a refrigerant system using a
 refrigerant to transfer heat between air and a fluid, wherein the air is
 supplied to a comfort zone. The system comprises a compressor adapted to
 compress and discharge the refrigerant; a fluid heat exchanger having a
 refrigerant passageway in heat transfer relationship with the fluid; a
 primary heat exchanger that places the refrigerant in heat transfer
 relationship with the air; a secondary heat exchanger exposed to said air;
 a primary refrigerant flow restriction coupling the primary heat exchanger
 to the fluid heat exchanger; a secondary refrigerant flow restriction
 coupling the primary heat exchanger to the secondary heat exchanger; and a
 valve system. The valve system is situated to receive compressed
 refrigerant from the compressor and is selectively operable in a heating
 mode, a normal cooling mode, and a reheat cooling mode to selectively
 direct refrigerant flow. In the heating mode, most of the refrigerant from
 the compressor bypasses the secondary heat exchanger and the secondary
 refrigerant flow restriction and passes in series through the primary heat
 exchanger, the primary refrigerant flow restriction, and the refrigerant
 passageway of the fluid heat exchanger. In the normal cooling mode, most
 of the refrigerant from the compressor bypasses the secondary heat
 exchanger and the secondary refrigerant flow restriction and passes in
 series through the refrigerant passageway of the fluid heat exchanger, the
 primary refrigerant flow restriction, and primary heat exchanger. In the
 reheat cooling mode, most of the refrigerant from the compressor passes in
 series through secondary heat exchanger, the refrigerant passageway of the
 fluid heat exchanger, the primary refrigerant flow restriction, and the
 primary heat exchanger.
 The present invention additionally provides a method of conveying
 refrigerant flow through the refrigerant system. The method applies to a
 refrigerant system that includes a primary heat exchanger that places a
 refrigerant in heat transfer relationship with air, a secondary heat
 exchanger exposed to the air, a fluid heat exchanger having a refrigerant
 passageway in heat transfer relationship with a fluid, and a primary
 refrigerant flow restriction that couples the refrigerant passageway of
 the fluid heat exchanger to the primary heat exchanger. The method
 comprises conveying most of the refrigerant in series through the
 refrigerant passageway of the fluid heat exchanger, the primary
 refrigerant flow restriction, and the primary heat exchanger; directing
 most of the refrigerant to bypass the secondary heat exchanger; and
 venting the secondary heat exchanger to the primary heat exchanger to
 prevent the secondary heat exchanger from flooding with liquid
 refrigerant.
 The present invention yet further provides a method of conveying
 refrigerant flow through the refrigerant system. The method applies to a
 refrigerant system that includes a primary heat exchanger that places a
 refrigerant in heat transfer relationship with air, a secondary heat
 exchanger exposed to the air, a fluid heat exchanger having a refrigerant
 passageway in heat transfer relationship with a fluid, and a primary
 refrigerant flow restriction that couples the refrigerant passageway of
 the fluid heat exchanger to the primary heat exchanger. The method
 comprises conveying a major portion of the refrigerant in series through
 the secondary heat exchanger, the refrigerant passageway of the fluid heat
 exchanger, the primary refrigerant flow restriction, and the primary heat
 exchanger; and directing a minor portion of the refrigerant to pass from
 the secondary heat exchanger to the primary heat exchanger, whereby the
 minor portion bypasses the refrigerant passageway.
 The present invention still further provides a refrigerant system
 comprising a refrigeration cycle and an air movement section. The
 refrigeration cycle including a compressor, a primary flow restrictor, and
 first, second and third heat exchangers operably connected into a
 refrigeration cycle. The air movement section includes a fan moving air
 sequentially over the first heat exchanger and then the second heat
 exchanger. The second heat exchanger has a liquid refrigerant outlet
 connected to an inlet of the first heat exchanger and a gas refrigerant
 outlet connected to an inlet of the third heat exchanger. The system
 further includes a valving arrangement for shiftably connecting and the
 second heat exchanger to either a series or a parallel arrangement with
 the third heat exchanger.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 A refrigerant system 10, shown in FIG. 1, can cool, heat, and/or dehumidify
 a stream of air 12 that a blower 14 forces through a supply air duct 16.
 Duct 16 conveys the conditioned air 12 to a room 18 or some other comfort
 zone within a building 20. A return air duct 22 returns air 12 from within
 room 18 to a sheet metal enclosure 24. Within enclosure 24, blower 14
 forces air 12 first across a primary heat exchanger 26 and then across a
 reheat heat exchanger 28, before discharging air 12 back out through
 supply air duct 16.
 Heat exchangers 26 and 28 are part of a hermetically sealed refrigerant
 circuit 30 that also includes a refrigerant compressor 32 that compresses
 and discharges refrigerant, a fluid heat exchanger 34 (e.g., a
 water-cooled heat exchanger), a primary refrigerant flow restriction 36
 (e.g., thermal expansion valve, electronic expansion valve, orifice,
 capillary tube, etc.), a secondary refrigerant flow restriction 38
 (preferably a 1/8-inch diameter capillary tube, but could also be an
 orifice or an expansion valve), a first check valve 40, and a second check
 valve 42.
 To reconfigure system 10 to operate in a normal cooling mode, a heating
 mode, or a reheat cooling mode, system 10 includes a valve system 44 that
 directs the flow of refrigerant along various paths through circuit 30. In
 some embodiments of the invention, valve system 44 comprises a reversing
 valve 46 and a reheat valve 48, with valve system 44 and valves 46 and 48
 being schematically illustrated to encompass a broad range of readily
 available structures (and their locations) that can redirect the flow of
 refrigerant so as to achieve the results specified herein. The actuators
 of valve system 44 are also schematically illustrated to encompass the
 wide variety of well-known modes of actuation including, but not limited
 to, manual, solenoid, spring-return, detent or maintained positions, pilot
 actuation, and various combinations thereof. Nonetheless, for sake of
 example, reversing valve 46 is a 4-way, two-position, solenoid actuated,
 spring-return valve and reheat valve 48 is a 3-way, two-position, solenoid
 actuated, spring-return valve. The normal positions of valves 46 and 48
 are as shown in FIG. 1, which places system 10 in the normal cooling mode.
 In the normal cooling mode, relatively hot, compressed refrigerant
 discharged from compressor 32 passes in series through an inlet port 50, a
 passageway 52, and a first port 54 of reversing valve 46; an inlet 56, a
 passageway 58, and an outlet 60 of reheat valve 48; and through a
 refrigerant passageway 62 of fluid heat exchanger 34. Upon passing through
 passageway 62, the refrigerant is cooled and condensed by a relatively
 cool fluid, such as ground water from a well. The water or other fluid
 passes through a second passageway 64 in fluid heat exchanger 34 to place
 the fluid in heat exchange relationship with the warmer refrigerant,
 whereby heat exchanger 34 serves as a condenser. From there, the
 refrigerant passes through restriction 36, which causes the refrigerant to
 expand and cool. Next, the refrigerant passes through primary heat
 exchanger 26, as check valve 40 inhibits flow to restriction 38. Primary
 heat exchanger 26 serves as an evaporator as the cool refrigerant passing
 through it cools air 12. After leaving primary heat exchanger 26, the
 refrigerant returns to compressor 32 by passing in series through a second
 port 66, a passageway 68, and an outlet port 70 of reversing valve 46.
 While in the normal cooling mode, secondary heat exchanger 28 is relatively
 inactive. Check valve 42 inhibits refrigerant flowing into secondary heat
 exchanger 28 from outlet 60 of reheat valve 48. And check valve 40
 inhibits refrigerant flowing into secondary heat exchanger 28 from a point
 72 between primary flow restriction 36 and check valve 40. Nonetheless, if
 high pressure refrigerant leaks into secondary heat exchanger 28 through
 slight clearances or leaks in check valve 42 or reheat valve 48, secondary
 flow restriction 38, in series with check valve 40, vents any buildup of
 high pressure refrigerant in secondary heat exchanger 28 to a low pressure
 side of circuit 30, such as into primary heat exchanger 26. The venting
 helps prevent secondary heat exchanger 28 from becoming flooded with
 liquid refrigerant.
 In the reheat cooling mode as shown in FIG. 2, energizing a solenoid 74
 shifts the position of reheat valve 48, while reversing valve 46 remains
 in its normal position. Thus, relatively hot, compressed refrigerant from
 port 54 of reversing valve 46 now passes in series through inlet 56, a
 passageway 76, and an outlet 61 of reheat valve 48. The hot, pressurized
 refrigerant passes through a line 78 and secondary heat exchanger 28 to
 heat air 12. In other words, secondary heat exchanger 28 reheats air 12
 after primary heat exchanger 26 cools air 12.
 From secondary heat exchanger 28, the flow of refrigerant splits, with a
 major portion (i.e., most of the refrigerant) passing through check valve
 42 to enter passageway 62 of fluid heat exchanger 34, and a minor portion
 (i.e., less than half of the refrigerant) passing through secondary
 restriction 38 and check valve 40 to enter primary heat exchanger 26. Upon
 passing through secondary restriction 38, the minor portion of refrigerant
 expands and cools, which helps cool air 12 that is passing across primary
 heat exchanger 26.
 Meanwhile, the major portion of refrigerant entering passageway 62 of fluid
 heat exchanger 34 is cooled and condensed by the fluid passing through
 passageway 64. The condensed refrigerant then passes through primary flow
 restriction 36, which causes the refrigerant to expand and cool before
 joining the minor portion of refrigerant in primary heat exchanger 26.
 After providing most of the cooling of air 12, the major portion of
 refrigerant along with the minor portion leaves primary heat exchanger 26
 and returns to compressor 32 by passing in series through port 66,
 passageway 68, and outlet port 70 of reversing valve 46.
 In some forms of the invention, a flow divider 71 promotes the separation
 of refrigerant so that the minor portion of refrigerant passing through
 check valve 40 is of a higher concentration of liquid refrigerant than the
 major portion of refrigerant passing through check valve 42. Flow divider
 71 is schematically illustrated to encompass a wide variety of well-known
 liquid/gas separators, such as those operating under the same basic
 principles as steam traps. Other examples of flow divider 71 include, but
 are not limited to, a simple T-connection. With the T-connection turned
 sideways, as shown, flow divider 71 includes a horizontal inlet 73, a
 lower leg 75 (first outlet) pointing downward, and an upper leg 77 (second
 outlet) pointing upward. In this orientation, liquid refrigerant may tend
 to gravitate downward through lower leg 75, while gaseous or vaporous
 refrigerant blows freely upward through leg 77 without having to overcome
 the restriction of secondary flow restriction 38.
 In the heating mode as shown in FIG. 3, energizing a solenoid 80 shifts the
 position of reversing valve 46, while de-energizing solenoid 74 allows
 reheat valve 48 to return to its normal position. Compressed refrigerant
 from compressor 32 now passes through a passageway 82 of reversing valve
 46 to enter primary heat exchanger 26 as relatively hot refrigerant that
 heats air 12. From primary heat exchanger 26, the refrigerant passes
 through primary flow restriction 36, since check valve 40 blocks
 refrigerant flow to secondary flow restriction 38. Upon passing through
 primary flow restriction 36, the refrigerant expands and cools. The
 relatively cool refrigerant then passes through passageway 62 of fluid
 heat exchanger 34 to absorb heat from the warmer fluid passing through
 passageway 64. Thus, in the heating mode, fluid heat exchanger 34
 functions as an evaporator. From fluid heat exchanger 34, the refrigerant
 returns to compressor 32 by passing in series through passageway 58 of
 reheat valve 48 and a passageway 84 of reversing valve 46.
 Since check valve 40 helps prevent pressurized refrigerant in primary heat
 exchanger 26 from entering secondary heat exchanger 28, secondary heat
 exchanger 28 is relatively inactive during the heating mode. However, if
 some high pressure refrigerant happens to leak into secondary heat
 exchanger 28, check valve 42 vents the pressurized refrigerant to a low
 pressure side of circuit 30, e.g., between passageway 62 of fluid heat
 exchanger 34 and passageway 58 of reheat valve 48. Such venting, thus,
 avoids flooding secondary heat exchanger 28 during the heating mode.
 Although the invention is described with respect to a preferred embodiment,
 various modifications thereto will be apparent to those skilled in the
 art. For example, although refrigerant system 10 is described as what is
 known as a heat pump that selectively provides cooling and heating modes,
 system 10 could be a cooling-only refrigerant system having a reheat mode.
 In other words, the heating mode, and thus reversing valve 46, can be
 eliminated, and such a refrigerant system would still be well within the
 scope of the invention. Also, the preferred implementation as a water
 source heat pump with hot gas reheat can be modified to encompass other
 HVAC applications such as split systems, rooftop systems and systems using
 air handlers. Therefore, the scope of the invention is to be determined by
 reference to the claims, which follow.