Abstract:
The present invention discloses a heat exchanging apparatus including a plate type heat exchanger auxiliary vessel arrangement whereby the auxiliary vessel contains fluid in more than one phase to enable the corresponding plate type heat exchanger to be flooded with heat exchanger fluid in order to fully employ its heat exchange surfaces in the task of exchanging heat.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to improvements in plate type heat exchangers, particularly plate type heat exchangers used as evaporators in vapor compression refrigeration, heat pump systems, and dedicated heat recovery chiller systems. 
         [0003]    2. Description of the Related Art 
         [0004]    Plate type heat exchangers have been utilized in the past in many applications, including vapor compression refrigeration systems. 
         [0005]    However, these heat exchangers suffer from a problem, in that when employed as an evaporator in a vapor compression refrigeration cycle, they are often just upstream of a compressor. Because liquid plate refrigerant entrained in a gas phase refrigerant flowing from the evaporator into the compressor tends to damage the compressor and also reduces its efficiency, fluid emerging from an evaporator is ideally essentially vapor. 
         [0006]    In the past, prior art plate heat exchanger evaporators in these applications could not be fully utilized regarding their heat transfer capabilities. Particularly the total available heat exchange surface area could not be fully utilized, because a portion of the plate heat exchanger, usually near the top, would be purposely kept essentially free of liquid evaporant, ensuring that eventually any vapor state refrigerant would exit at the top, adjacent the outlet to the plate type heat exchanger. In this manner, a portion of the heat transfer area of the plates would be used to contain vapor refrigerant just prior to exiting the exchanger, instead being used to evaporate liquid refrigerant. 
         [0007]    The result is that a portion of the plate heat exchanger would be underutilized for its intended purpose of evaporating liquid refrigerant. 
         [0008]    This situation resulted in plate heat exchangers which were oversized and meanwhile underutilized for their intended purpose. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The present invention is directed toward providing a plate heat exchanger apparatus which fully utilizes the heat exchanger areas of the plates. 
         [0010]    Particularly, the present invention sets out a plate heat exchanger apparatus having an secondary or auxiliary vessel for containing liquid, gas, and/or a liquid-gas mixture. 
         [0011]    More particularly, the present invention provides an arrangement for accommodating fluid exiting a plate heat exchanger which is employed as an evaporator in a vapor compression refrigeration cycle. The arrangement includes an auxiliary vessel downstream of the evaporator heat exchanger, upstream of the compressor. 
         [0012]    In this manner, the evaporation plate heat exchanger may be filled (flooded) with refrigerant in order to utilize all available plate heat exchange surface area for exchanging heat, while allowing the exiting fluid to travel to the auxiliary vessel, such that substantially only vapor exits the auxiliary vessel. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic view of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    The present invention sets out a two chamber plate heat exchanger having an additional chamber for accepting and controlling refrigerant or other fluid in two thermodynamic phases—gas and liquid. The invention further sets out a system for utilizing and controlling the fluid in the system. 
         [0015]    The inventive two chamber plate heat exchanger may be advantageously employed as an evaporator for refrigerant in a closed-loop vapor compression refrigerant cycle. 
         [0016]    Referring to  FIG. 1 , a vapor compression refrigeration cycle including the present invention is shown. 
         [0017]    Refrigerant  11  is condensed to a liquid state  12  in the condenser element  11  before exposure to the expansion valve  9 . The expansion valve  9  may be controlled as set out below. 
         [0018]    Depending on the position of the expansion valve  9 , the thermodynamic condition of the condensed refrigerant  8  is variously, entirely, in liquid state, or a two-phase liquid vapor state. It is introduced into the plate heat exchanger  1  which together with the secondary or auxiliary vessel  4  forms the evaporative heat exchanger apparatus of the present invention. 
         [0019]    The refrigerant in the secondary vessel or auxiliary vessel  4  may be in liquid phase, gas phase, and/or a mixed liquid gas phase. 
         [0020]    The secondary vessel  4  may be arranged above or on top of the evaporative plate heat exchanger  1 . 
         [0021]    Liquid refrigerant  8  is introduced into the evaporative plate heat exchanger  1  at or near a bottom portion of the exchanger  1 . Warm fluid  5  from the building load  16  which is to be chilled via the phase change of the refrigerant in the evaporative plate heat exchanger  1  is introduced into the exchanger  1 . Because the secondary vessel  4  is arranged to accommodate the gas and non-gas phases of this refrigerant, the evaporative plate heat exchanger  1  can be more effectively utilized to exchange heat from the building load  16  to the refrigerant  8 . Specifically, there is no need to allow empty space at the top of the evaporative plate heat exchanger  1  to ensure that no liquid leaves the exchanger en route to the compressor  10  inlet, because the inventive element of the secondary vessel  4  is specifically arranged to perform the function of holding and managing the gas and non-gas phase refrigerant. In this way, the entire surface area of the evaporative plate heat exchanger  1  can be utilized to exchange heat from the building load  16  to the refrigerant  8 . 
         [0022]    In another embodiment, the evaporative plate heat exchanger may include a dual refrigerant inlet, to minimize maldistribution of heat and fluid flow in the exchanger. 
         [0023]    In one embodiment, a fluid connection is arranged from the bottom of the secondary vessel  4  to the top of the evaporative plate heat exchanger  1 , in order to communicate the refrigerant between the secondary vessel and the heat exchanger. 
         [0024]    The evaporated refrigerant  7  travels through the secondary vessel  4  and exits at the top of the vessel  4 . The system is arranged to ensure that any gas-phase refrigerant  7  exits the secondary vessel  4 , while liquid and two-phase fluids remain in the secondary vessel  4 , to be delivered back into the evaporative plate heat exchanger  1  for evaporation, in a closed-loop manner. 
         [0025]    A secondary vessel liquid level sensor  2  monitors the level of liquid in the secondary vessel  4 , and sends a corresponding liquid level signal  3  back to the expansion valve controller  18 . The liquid level signal  3  indicates to the controller  18  whether to variably open or close the expansion valve  9 , in order to supply essentially liquid or gas phase refrigerant to the evaporative plate heat exchanger  1 . 
         [0026]    The expansion valve controller  18 /expansion valve  9  assembly is arranged to adjust the thermodynamic characteristics of the refrigerant  12 ,  8  in order to supply the secondary valve  4 /evaporative plate heat exchanger  1  structure with refrigerant  8  in a condition which is determined to be required for most effective and efficient heat transfer, and energy consumption in the form of compressor work. 
         [0027]    The secondary valve  4 /evaporative plate heat exchanger  1  structure may be utilized in connection with dedicated heat recovery chillers, heat pump systems, and/or conventional chiller refrigeration cycles.