Abstract:
Apparatus for and method of use for a heat exchanger in an HVAC system having a system refrigerant for heat transfer between a radiator and a heat exchanger, in heat transfer communication through the heat exchanger. Single or multiple heat exchange loops and flow controllers maintain system balance during operation of the system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The method and apparatus of the present invention relate to the field of heat exchangers, and more particularly to heating, ventilation and air conditioning systems. 
     2. Description of the Related Art 
     There are numerous heating, ventilation and air conditioning protocols in use today, for use in industrial, commercial, automotive, and residential applications. Generally, a heating system heats a selected environment by using the heat which is generated when a fuel is combusted in a burner, for heating a liquid or gaseous fluid, and then circulating the heated fluid through a circulatory system including radiators or outlets installed in the selected environment. Likewise, cooling systems including prior art air conditioning systems and heat pumps utilize a refrigerant to extract a heat component from the refrigerant flow on a continuous flow basis. In all of these systems, bidirectional flow relative to a heat exchanger is required to achieve the desired level of heat exchange necessary to heat/cool the selected environment. Specifically, the heat exchanger of the related art includes a first fluid that flows from one chamber to another chamber through bypass or cross-flow conduits, so as to exchange heat with a second fluid flowing in the passages of adjacent, heat-conductive conduits. Such heat exchangers are used as evaporators in coolant fluid circuits in stationary residential, commercial, industrial and automotive applications. Typically, a refrigerant fluid is the first fluid, the second fluid being atmospheric air. Alternatively, the second fluid is typically available in large quantities at substantially low cost, for use in bulk flow heat exchangers, such as water. As is well known in the art, larger industrial heat exchangers are located near large bodies of water, while smaller installations and mobile applications require either a piped-in or on-board supply of water. In any case, however, the prior art relies on relatively high flow through rates of a coolant, such as water, to provide acceptable levels of heat transfer. 
     Generally, the prior art utilizes plate-type heat exchangers, wherein each plate of the heat exchanger is provided in the form of a fin or shallow tray, and is formed with two apertures serving as the inlet and outlet, respectively, for the first refrigerant fluid. The chamber which is defined between the two plates of any single pair of plates includes an internal partition which gives the fluid flowing in the chamber a generally U-shaped flow path between the inlet aperture and the outlet aperture. This partition is generally formed by sealingly joining together two longitudinal projecting ribs each of which forms part of a respective one of the plates in that pair of plates. The communicating apertures are typically formed in a projecting element or pocket which is arranged at one end of each plate. In addition, the plates are generally joined together at their other end by a base plate which provides spacing between the pair of plates. 
     When the heat exchanger serves as an evaporator, the refrigerant fluid enters the heat exchanger in the liquid state and leaves the heat exchanger in the vapor state, after having cooled a stream of air by evaporation. Often, water or water-based solutions are used as the second fluid in the so-described systems. Such use is common to HVAC systems both small and large due to a relatively low water costs, as described above, especially in larger systems with long pipe runs and large fluid capacity and heat transfer requirements. However, a water or water-solution based refrigerant/coolant system does not provide optimized, high efficiency operation due primarily to relatively poor heat exchange properties on a specific mass basis. As a result, the necessary plumbing systems mandate massive space and weight requirements. 
     Accordingly, there is a need for a system and apparatus for overcoming the shortcomings of the related, prior art HVAC systems. 
     SUMMARY OF THE INVENTION 
     The present invention is a method and apparatus of use of a heat exchanger in an HVAC system utilizing a system refrigerant for heat transfer between a radiator and a heat exchanger, for flowing the refrigerant in heat transfer communication through the heat exchanger. Single or multiple heat exchange loops and flow controllers maintain system balance during operation of the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram representation of a first embodiment of the HVAC system of the present invention, showing a single circuit reversing valve system switchable between heating and air-conditioning functions. 
     FIG. 2 is a front view of one embodiment of the heat exchanger of the present invention, showing a coaxial arrangement of thermally contacting refrigerant flow conduits. 
     FIG. 3 is a block diagram representation of a second embodiment of the HVAC system of the present invention, showing a dual circuit reversing valve system switchable between heating and air-conditioning functions. 
     FIG. 4 is a block diagram representation of a third embodiment of the HVAC system of the present invention. 
     FIG. 5 is a schematic representation of the control system of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to the drawings, FIG. 1 schematically illustrates one embodiment of the heat exchanger apparatus and system of the present invention. As shown, system  10  includes a compressor  12  in fluidic communication with a radiator such as a fan coil  14 . A thermal transfer fluid such as the system refrigerant SR of the present invention is flowed through an interconnected network of conduits  16 ,  18 ,  20 ,  22 ,  24 ,  25 ,  26 ,  28 , and through a heat exchanger  30 , as will be more filly described below. 
     Specifically, during a heating cycle, system refrigerant SR is directed in a closed loop system in vapor form through conduit  16  through compressor inlet  17  and into compressor  12  which could be a scroll compressor or the like. After compression, the resulting hot compressed gas flow is directed through compressor outlet  19  to conduit  18  and directed by reversible gas flow valve  32  toward and through conduit  24  and then into outer jacket  25  of heat exchanger  30 . The cooled hot gases are then directed through conduit  26  and flowed into fan coil inlet  34 , through the fan coil  14  via fan coil conduits  36  for further heat exchange. The flow is then outputted through fan coil outlet  38  to conduit  20  in the closed loop system. During the heating cycle, a restrictor  40  having a predetermined Joule-Thompson coefficient further allows the liquid flow to expand as it enters conduit  20 , which flow cools refrigerant SR in the outer jacket  25  of heat exchanger  30 . Also, check valve  42  is closed during the heating cycle, and all liquidus fluid flow is directed into conduit  28 . Check valve  42  may be a spring-checked directional check valve or the like as will be apparent to one skilled in the relevant art. 
     Heat exchanger  30  has a shell and tube construction, or other construction as will be apparent to the skilled artisan. For example, the heat exchanger  30  may have a double pipe or double-tube construction, an open vertical shell and tube construction, a horizontal shell and tube construction as shown herein, or a shell and coil construction. 
     For a double-tube condenser, coolant initially flows through an interior tube, which may be about 0.75-0.87 inch diameter copper or steel construction, although heat conductive tubing having a lesser or greater diameter may be used. An exterior tube also of heat conductive metal such as copper or steel construction surrounds the interior tube in generally concentric arrangement for refrigerant flow in the annular space defined between the tubes. The double-tube condenser may be formed into a coil to achieve a compact package for installation and servicing convenience. The exterior tube may be fabricated of about 1.0 to 1.25 inch diameter metal, although heat conductive tubing having a lesser or greater diameter may be used to accommodate refrigerant flow rates and heat transfer requirements. According to any construction, and according to the invention, outer conduit  25  is coiled about an axial extent of conduit  20  as necessary to effect the desired heat transfer quantity for a selected range of fluid flow rates through the system  10 , or may be provided in closed shell form with an internal baffle arrangement (not shown). With reference to FIG. 2, heat exchanger  31  has a serpentine construction, with conduit  25  circumferentially extending about an axial length of conduit  20 . A refrigerant such as Dupont brand Freon, R22, R134A or other refrigerant is selected to meet heat capacity, compressibility and volatility characteristics required for a specific application. 
     Again referring to FIG. 1, system  10  is selectively operable between heating and cooling applications. In the cooling mode, fluid refrigerant SR is flowed in a reverse cycle. Specifically, superheated vapor flow exiting from conduit  25  encompassing conduit  20  is directed toward valve  32 , which shunts that flow toward conduit  16  and into compressor  12 , to be returned via conduit  20  through heat exchanger  30  in the direction of arrow B. The resulting cooled fluid flow is flowed through open directional valve  42  and then toward restrictor  40 , which allows the liquid to vaporize as it passes through conduit  26  and then through conduit  25  and then enters conduit  26  leading back to the compressor  12 . 
     Accordingly, the refrigerant passing through conduit  20  in the direction of arrow B in a superheated, gaseous stage is condensed to a primarily liquid stage, and recycled through the system  10  in the mode required. It will be understood that the gaseous refrigerant flow may not be entirely condensed to a pure liquidus state, and such mixed liquidus-gaseous state does not hamper the operation of inventive system. 
     With reference now to FIG. 3, a second embodiment of the invention is shown with a dual return loop for enhancing heat exchange capacity of the inventive system. Accordingly, FIG. 3 includes all so-numbered elements of the first described embodiment, additionally showing elements of dual circuit reversing valve system. Specifically, system  50  further includes a return conduit  52  introducing a return vapor flow into reversing valve  54  to be directed toward and through conduit  56  in fluid connection with return conduit  58  which converges with outflow directed through conduit  24 , the aggregate fluid flow then directed toward valve  32  in the manner previously described with respect to the embodiment shown and described in FIGS. 1 and 2. An intermediate coil extends through fan coil  14  for air-to-air heat transfer to further increase thermal efficiency of the operating system. During cooling operation of system  50 , system refrigerant SR is flowed in the direction of arrow C through a directionally oriented restrictor  62 , and then into coil  58  in the manner previously described. Another directionally oriented restrictor  60  is mounted for fluid flow in the reverse direction for operation of system  50  in the heating mode. A further directionally oriented restrictor  64  is mounted downstream of conduit  58  for operation in the cooling mode. Accordingly, whether during operation in heating mode or cooling mode, the present invention ensures a change of state necessary to cool hot gas flow to a substantially saturated liquid flow, as required for the required change of state in the heat exchanger. 
     With reference now to FIG. 4, a third embodiment of the invention is shown for enhancing heat exchange capacity of the inventive system. Accordingly, FIG. 4 includes all so-numbered elements of the first and second described embodiments, additionally showing an alternative arrangement including directional restrictors for diverting and directing system refrigerant SR between the compressor  12  and fan coil  14  via the double-tube heat exchanger  30 . Specifically, FIG. 4 shows the cool mode, and that drawing figure also shows the heating mode of this alternative arrangement, to achieve the operational goals set forth above. 
     With reference now to FIG. 5, control circuitry is utilized for control and operation of the present invention, whether for the single circuit or the dual circuit of the various embodiments of the invention. This control circuitry includes input and process controllers, as will be apparent to the skilled artisan. Specifically, input/output/process/conditional steps shown in FIG. 4 reference the inputs and controls for operation in heating and cooling modes. More specifically, a bi-directional valve  80  is controlled by a first relay  82  and a second relay  84 . In order for the bi-directional valve  80  to operate in the heating mode, after first relay  82  turns off, second relay  84  is switched over to the heating mode and first relay  82 , successively, turns on. In order that bidirectional valve  80  operates in the cooling mode, after first relay  82  turns off, second relay  84  is switched over to the cooling mode and first relay  82  returns to the turn-on state. 
     Prior to operation of the bi-directional valve  80 , a control section  86  checks whether or not the system is in heating mode or cooling mode. When receiving a cooling mode selection signal, the control section  86  provides an electric power control section  88  with a first control signal. Depending on the first control signal, the control section  86  provides a second control signal which is a mode terminal switching signal and controls the system to switch between the heating mode and the cooling mode. The necessary control signals and feedback system provides consistent transition between modes and between a selected mode and a system shut-down mode. 
     As the skilled artisan will appreciate, the inventive system according to any of the disclosed embodiments may be operated with a millivolt control system,  24  volt control system, or other system as will be apparent to the skilled artisan. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.