Patent Publication Number: US-6986387-B2

Title: Multi-mode damper for an A-shaped heat exchanger

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an HVAC system (heating, ventilating, air-conditioning system) that includes a refrigerant circuit with an indoor coil having two coil slabs; the invention more specifically relates to a damper apparatus for determining whether airflow travels through the two coil slabs in parallel or series. 
   2. Description of Related Art 
   Typical split-system air conditioners and heat pumps comprise a refrigerant circuit with an indoor and an outdoor heat exchanger. Depending on the refrigerant&#39;s direction of flow through the circuit, the indoor heat exchanger may cool or heat a current of air, which is then conveyed to a comfort zone, such as room or other area within a building. 
   The indoor heat exchanger may comprise two sections, called coil slabs, which are often arranged in an A-shape. To heat or cool the air, a blower forces the air in parallel flow relationship across the two coil slabs. Such an airflow pattern provides several advantages, such as optimum system efficiency, maximum heating or cooling capacity, and plenty of airflow. In some applications, however, such a system has its drawbacks. 
   Many HVAC systems, for instance, exchange a considerable amount of indoor air with outside air to help keep the indoor air fresh. Unfortunately, the outdoor air may be humid, which can create a dank feeling within the building. The HVAC system, therefore, may require some means for reducing the humidity. 
   Another problem may exist with heat pumps operating in a heating mode. Although the heat pump may have sufficient capacity to maintain the building at a desired temperature, the heated air that a register discharges into a comfort zone may feel uncomfortably cool or drafty. This can be due to the supply air temperature being warmer than the room temperature but cooler than a person&#39;s body temperature. Consequently, the supply air temperature may need to be raised. 
   A further problem concerns systems that may operate the system blower with the refrigeration system de-activated. Examples of this would be for air circulation or when the refrigeration system is utilized with a combustion furnace. Here the resistance to airflow by the indoor heat exchanger becomes an undesirable system efficiency loss. 
   SUMMARY OF THE INVENTION 
   To overcome the limitations of current split-system air conditioners and heat pumps, it is an object of the invention to provide a damper system that determines whether the airflow though two coil slabs of an indoor heat exchanger passes through the coil slabs in a parallel or series flow relationship. 
   Another object of some embodiments is to provide a damper system with an enhanced mode position that helps a heating system raise the temperature of air being supplied to a comfort zone. 
   Another object of some embodiments is to provide a damper system with an enhanced mode position that helps a cooling system lower the temperature of air being supplied to a comfort zone. 
   Another object of some embodiments is to provide a damper system with an enhanced mode position that helps a cooling system lower the humidity of air being supplied to a comfort zone. 
   Another object of some embodiments is to provide a damper system with an enhanced mode position that helps reduce the airflow to a comfort zone by increasing the airflow resistance of an indoor heat exchanger. 
   Another object of some embodiments is to provide a damper system that is selectively movable to a normal mode position, an enhanced mode position and a bypass position. 
   Another object of some embodiments is to provide a damper system that upon switching from a normal mode position to an enhanced mode position reverses the direction of airflow through one coil slab of a dual-slab indoor heat exchanger. 
   Another object of some embodiments is provide a temperature conditioning system with a burner, a refrigerant heat exchanger, and a damper system, wherein the damper system is movable to a bypass position to allow furnace-heated air to bypass the refrigerant heat exchanger when the refrigerant heat exchanger is inactive. 
   Another object of some embodiments, is to provide an A-shaped indoor heat exchanger that operates in conjunction with a damper system, wherein refrigerant flows in a parallel flow relationship through two coil slabs of the indoor heat exchanger. 
   One or more of these and/or other objects of the invention are provided by a temperature conditioning system that includes a damper system that determines the pattern of airflow through two coil slabs of an indoor heat exchanger. In a normal mode position, the damper system directs the airflow in a parallel flow relationship through the two coil slabs. In an enhanced mode position, the damper system directs the airflow in a series flow relationship through the two coil slabs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of a temperature conditioning system operating in a cooling mode with a damper system in a normal mode position. 
       FIG. 2  is similar to  FIG. 1  but showing the temperature conditioning system operating in a cooling mode with the damper system in an enhanced mode position. 
       FIG. 3  is similar to  FIG. 1  but showing the temperature conditioning system operating in a heating mode with the damper system in the enhanced mode position. 
       FIG. 4  is similar to  FIG. 1  but showing the damper system in a bypass position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A temperature conditioning system  10 , shown in  FIGS. 1–4 , includes a blower  12  that can force air  14  across a heat exchanger  16  to heat, cool, and/or dehumidify the air. A damper system  18 , comprising dampers  20  and  22 , determines the air&#39;s flow path through or around heat exchanger  16 , thereby determining whether system  10  operates in a normal mode ( FIG. 1 ), an enhanced mode ( FIGS. 2 and 3 ) or a bypass mode ( FIG. 4 ). After air  14  travels past heat exchanger  16 , a supply air duct  24  can convey the air to a comfort zone, such as a room or other area within a building. To circulate air  14  between system  10  and the comfort zone, a conventional return air duct can convey air  14  from the comfort zone back to system  10 . Examples of system  10  include but are not limited to an air conditioner, a heat pump, a furnace, and various combinations thereof. For illustration, system  10  will be described with reference to a heat pump  26  associated with a furnace  28 . 
   Heat pump  26  includes a refrigerant circuit  30  that interconnects a refrigerant compressor  32 ; an outdoor heat exchanger  34 ; an indoor heat exchanger, such as heat exchanger  16 ; and an expansion device  36 , such as a conventional expansion valve, orifice, capillary, etc. When operating in a cooling mode, as shown in  FIGS. 1 and 2 , heat exchanger  16  functions as an evaporator to cool air  14 , and outdoor heat exchanger  34  functions as a condenser to expel waste heat. 
   In a heating mode, as shown in  FIG. 3 , a valve  38  can be used to reverse the direction of refrigerant flow through much of circuit  30 . The reversed flow direction reverses the roles of heat exchangers  16  and  34 ; that is, heat exchanger  16  becomes a condenser that heats air  14 , and heat exchanger  34  becomes an evaporator that absorbs outdoor heat. 
   Heat exchanger  16  comprises two tube and fin heat exchangers that are referred to as coil slabs  40  and  42 . Heat exchanger  16  is generally A-shaped in that coil slabs  40  and  42  are closer to each other at an upper portion  44  than at a lower portion  46  of heat exchanger  16 . Refrigerant in circuit  30  preferably travels in a parallel flow relationship through slabs  40  and  42 . 
   For additional heat, or for refrigerant circuits designed for cooling only, system  10  may include a furnace burner  48  with a clamshell heat exchanger  50  and a flue gas exhaust pipe  52 . Burner  48  and heat exchanger  50  can be installed beneath heat exchanger  16 . In this way, blower  12  forces air  14  across the furnace&#39;s heat exchanger  50  before the air passes through or around the upper heat exchanger  16 . 
   Regardless of whether system  10  operates in a cooling mode ( FIGS. 1 and 2 ) or a heating mode ( FIG. 3 ), the positioning of damper system  18  determines whether system  10  further operates in a normal mode ( FIG. 1 ), enhanced mode ( FIGS. 2 and 3 ), or bypass mode ( FIG. 4 ). Separate actuators  54  can individually control the movement of dampers  20  and  22 . Alternatively, a single actuator  54  can be mechanically coupled to move both dampers, wherein a mechanical linkage  56  coordinates the movement of the two dampers. Linkage  56  is schematically illustrated, for such a linkage can assume a variety of configurations that are well known to those skilled in the art. Actuator  54  can be any device capable of moving a damper. Examples of actuator  54  include, but are not limited to, an electric motor, a pneumatic cylinder, bellows, etc. 
   When damper system  18  is in its normal mode position and system  10  is operating in a cooling mode, as shown in  FIG. 1 , air  14  travels in parallel flow relationship through coil slabs  40  and  42 . Some of the airflow travels from an upstream side  58  to a downstream side  60  of coil slab  42 . And some airflow travels from a first side  62  to a second side  64  of coil slab  40 . 
   When damper system  18  is in its enhanced mode position and system  10  is operating in a cooling mode, as shown in  FIG. 2 , air  14  travels sequentially or in series through coil slabs  40  and  42 . In this case, dampers  20  and  22  direct substantially all or most of the airflow sequentially through second side  64 , first side  62 , upstream side  58  and downstream side  60 . 
   The dampers&#39; normal mode position and the enhanced mode position each have their own advantages when operating system  10  in the cooling mode. The normal mode position provides an airflow rate, system efficiency, and cooling capacity that is greater than that which can be achieved with damper system  10  in the enhanced mode position. The enhanced mode position, however, provides greater dehumidification. This is due to air  14  having to pass sequentially through coil slabs  40  and  42 , which provide a greater airflow resistance than when air  14  is able to pass in parallel flow relationship through the coil slabs. For a given blower speed, greater airflow resistance reduces the airflow, which enables heat exchanger  16  to reduce the air temperature and humidity more than it could otherwise. In some embodiments, blower  12  operates at a substantially constant speed regardless of whether damper system  18  is at its normal mode position or enhanced mode position. 
   The dampers&#39; normal mode position and the enhanced mode position each have their own advantages when operating system  10  in the heating mode as well. The normal mode position provides an airflow rate, system efficiency, and heating capacity that is greater than that which can be achieved with damper system  10  in the enhanced mode position. The enhanced mode position, as shown in  FIG. 3 , provides a greater supply air temperature, which can feel pleasantly warm near a register that feeds the air into the comfort zone. Again, this is due to air  14  having to pass sequentially through coil slabs  40  and  42 , which provide a greater airflow resistance than when air  14  is able to pass in parallel flow relationship through the coil slabs. For a given blower speed, greater airflow resistance reduces the airflow, which enables heat exchanger  16  to raise the air temperature more than it could otherwise. 
   In some cases, system  10  may be operated with damper system  18  in its bypass position, as shown in  FIG. 4 . There may be a need, for instance, for circulated or filtered air  14  that is neither heated nor cooled. Or furnace  28  may need to operate with heat pump  26  deactivated. In either case, heat exchanger  16  serves no purpose, so the air preferably bypasses heat exchanger  16  to avoid unnecessary airflow resistance. Damper system  18 , thus, moves to its bypass position of  FIG. 4  to allow air  14  the freedom to blow past heat exchanger  16 . 
   Although the invention is described with reference to a preferred embodiment, it should be appreciated by those skilled in the art that other variations are well within the scope of the invention. The shape of the indoor heat exchanger, for instance, can be other than an A-shape. The coil slabs can be arranged in a V-shape, the slabs can be offset and parallel to each other, or three or more slabs can be arranged in various other configurations. Moreover, the airflow does not necessarily have to reverse direction through either coil slab upon switching between the normal mode and enhanced mode. The scope of the invention, therefore, is to be determined by reference to the claims, which follow.