Abstract:
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.

Description:
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&#39;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&#39;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&#39;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. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a refrigerant system in a normal cooling mode of operation according to one embodiment of the invention. 
     FIG. 2 is a schematic diagram of the refrigerant system of FIG. 1 in a reheat cooling mode of operation. 
     FIG. 3 is a schematic diagram of the refrigerant system of FIG. 1 in a heating mode of operation. 
    
    
     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 ⅛-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.