Patent Publication Number: US-2023151979-A1

Title: Two-phase pre-cooling method for air conditioning system

Description:
CROSS-REFERENCE TO OTHER APPLICATION 
     This Application claims the benefit of and priority to U.S. Provisional Application No. 63/279,528 filed Nov. 15, 2021, the content of which is hereby incorporated by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to systems and methods for improving the efficiency and effectiveness of existing dehumidifiers. 
     BACKGROUND OF THE DISCLOSURE 
     Air conditioning systems generally provide some amount of dehumidification of air as part of the cooling process. These systems can be used to cool air already within an enclosed, conditioned space. Alternatively, such systems can be used to cool external air prior to introducing it to a conditioned space. However, such systems generally are inefficient and as a result, when external air is introduced into a conditioned room, the external air can introduce significant amounts of moisture that the air conditioning system may be unable to quickly or fully address. This introduction of external, humid air increases the perceived temperature of the conditioned space and decreases the comfort of individuals therein. 
     These problems are typically mitigated by using a separate dehumidification process (beyond the cooling system) on the external air prior to introducing the air to a conditioned room. However, such dehumidification processes are generally inefficient and require the expenditure of significant amounts of additional energy. 
     Thus, there exists a long-felt and currently unmet need for a system which allows for the more efficient dehumidification of external air prior to introducing it to a conditioned space. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure relates to systems and methods of controlling the temperature and humidity of a defined space. More specifically, the present disclosure is directed to systems and methods employing a two-phase process for pre-cooling air prior to dehumidification. In an embodiment of the present disclosure, external air is passed through a dry channel of a heat exchanger for pre-cooling prior to undergoing dehumidification. Any additional energy requirements for the heat exchanger are reduced or eliminated by simultaneously passing conditioned air through a wet channel of the heat exchanger prior to venting the conditioned air to the environment. Liquid in the wet channel evaporates into the exhausted, conditioned air, cooling the channel. The wet channel is thermally coupled to the dry channel, thereby cooling the dry channel and initially cooling and dehumidifying the external air before it enters the dehumidifier for additional dehumidification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description, given by way of example, but not intended to limit the disclosure solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings. 
         FIG.  1    shows a diagram of the air conditioning system comprising a heat exchanger, dehumidifier, conditioned room, and the airflow into and out of the system. 
         FIG.  2    displays a first embodiment of the system of  FIG.  1    comprising a heat exchanger with a plurality of channels. 
         FIG.  3    displays a second embodiment of the system of  FIG.  1    comprising a heat exchanger with a plurality of channels. 
         FIG.  4    displays a third embodiment of the system of  FIG.  1    which includes exhaust and supply fans. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     For the purposes of promoting and understanding the principles disclosed herein, reference is now made to the preferred embodiments illustrated in the drawings, and specific language is used to describe the same. It is nevertheless understood that no limitation of the scope of the invention is hereby intended. Such alterations and further modifications in the illustrated devices and such further applications of the principles disclosed and illustrated herein are contemplated as would normally occur to one of skill in the art to which this disclosure relates. 
     The inventors of the present disclosure have created a new method for controlling the air temperature, air flow, and humidity of a space which comprises an air conditioning system  100 . 
       FIG.  1    shows an air conditioning system  100  for a conditioned room  106  in accordance with an embodiment of the present disclosure. As shown, the air conditioning system  100  comprises a heat exchanger  102  and a dehumidifier  104 . The heat exchanger  102  and dehumidifier  104  are coupled together such that air is passed from the heat exchanger  102  to the dehumidifier  104 . The dehumidifier  104  is in turn coupled to the conditioned room  106 . In the embodiment shown in  FIG.  1   , the heat exchanger  102  and dehumidifier  104  and the dehumidifier  104  and conditioned room  106  are coupled together, respectively, using pipes, ductwork, or another physical linkage that is generally impermeable to air such that substantially all of the air that passes through the heat exchanger  102  is received by the dehumidifier  104  and substantially all of the air received by the dehumidifier  104  is passed on to the room  106 . 
     As shown, the heat exchanger  102  receives and pre-cools outdoor air  124 . During pre-cooling, the temperature of the air  124  is reduced, thereby causing water vapor in the air to condense into liquid form and removing water vapor from the air  124 . 
     In an embodiment, the heat exchanger operates as both a passive heat exchanger  102  (as further described herein) while also including an active cooling system to further cool the air during the pre-cooling step. 
     After exiting the heat exchanger  102 , the pre-cooled and partially dehumidified air is then passed through the dehumidifier  104 , which further dehumidifies the pre-cooled air. The dehumidifier  104  may comprise a membrane dehumidifier, desiccant dehumidifier, mechanical compression dehumidifier, or such other form of dehumidification system that is known in the art. After further dehumidification, the air is passed from the dehumidifier  104  to the conditioned room  106 . 
     In an alternative embodiment, the dehumidifier  104  may be omitted and the pre-cooled air may be passed directly from the heat exchanger  102  to the conditioned room  106 . In a second alternative embodiment, the dehumidifier  104  may be combined with the heat exchanger  102  such that a single device performs the functions of both as described herein. 
     In the embodiment shown in  FIG.  1   , the conditioned room  106  accepts the dehumidified and pre-cooled air from the dehumidifier  104 . The air then passes through the room at the desired temperature before exiting the room as exhaust  120 . 
     In alternative embodiments, an additional cooling system may be employed to further cool the air prior to introduction into the conditioned space  106  and/or to cool air within the conditioned space. In one such alternative embodiment, a separate air conditioning system (such as a central air conditioner) cools air within the conditioned space. In another such alternative embodiment, a further air conditioning system is employed to further cool the pre-cooled air before it is introduced into the conditioned space. 
     As shown, air from the conditioned room  106  is expelled from the conditioned room  106  as exhaust  120 . The exhaust  120  is passed through the heat exchanger  102  before being released into another environment. In embodiments, fresh external air is continuously brought into the conditioned space while a corresponding volume of exhaust  120  is expelled, such that the pressure in the conditioned room  106  is maintained substantially unchanged while constantly ventilating the conditioned space. 
       FIG.  2    shows an embodiment of a system  200  comprising a heat exchanger  202  comprising at least one dry channel  208  and at least one wet channel  210 . Hereafter, use of the singular version of “dry channel” and “wet channel” comprise both the plural or singular use of these terms. 
     In the embodiment shown in  FIG.  2   , external air is pulled into and passes through the dry channel  208  before being provided to the dehumidifier  104 . Similarly, the exhaust  120  is passed through the wet channel  210  before being expelled. The walls of the dry channel  214   a,    214   b  and the walls of the wet channel  214   c,    214   d  are thermally coupled, such that a change in temperature of any one wall  214  results in a corresponding change of temperature of the other walls  214 . In the embodiment shown, the surfaces of the walls of the wet and dry working channels may be connected to form a shared wall made from a thermally conductive material  217 . Each channel  208 ,  210  forms an enclosed space passing from a respective air inlet  213   a,    213   b  to an air outlet  215   a,    215   b.  Air flows from each inlet, through the respective channel, to the outlet. The walls  214   c,    214   d  of the wet channel are coated in a liquid. In the embodiment shown, the walls  214   c,    214   d  are coated in water. As exhaust  120  passes through the wet channel  210 , water from the walls  214   c,    214   d  evaporates, thereby reducing the temperature of the walls  214   c,    214   d.  As the exhaust has already been conditioned, it will generally have a low moisture content and thus effectuate significant evaporation. As the walls of the wet channel  210  cool, heat is transferred from the dry channel  208  to the wet channel  210 . External air passing through the dry channel  208  is thereby cooled through contact with the dry channel walls  214   a,    214   b,  and results in condensation and removal of moisture from the air. 
     In the embodiment shown in  FIG.  2   , a fluid connection between the dry channel  208  and the wet channel  210  continuously replenishes the supply of liquid in the wet channel  210  with moisture derived from the air passing through the dry channel  208 . In an alternative embodiment, the fluid connection is entirely passive, such that no external energy is needed to transport moisture from the dry channel  208  to the wet channel  210 . 
     The dry channel  208  and wet channel  210  may be arranged in multiple configurations. As will be clear to one of skill in the art, combinations of these embodiments and other passive transport techniques may be used to effectuate the transfer of moisture from the dry channel  208  to the wet channel  210  while preventing backflow of moisture from the wet channel  210  to the dry channel  208 . In an embodiment, the dry channel  208  is located above the wet channel  210  such that gravity effectuates the transfer of moisture from the dry channel  208  to the wet channel  210 . In an alternative embodiment, the fluid connection is structured such that capillary action effectuates the transfer of moisture from the dry channel  208  to the wet channel  210 . Regardless of the arrangement of the dry channel  208  and wet channel  210 , the walls  214   a,    214   b  of the dry channel  208  may be coated with a hydrophobic substance, such that water collecting thereon is driven through the fluid connection to the wet channel  210 . 
     In an alternative embodiment, an active source is used, such as a pump or like means, to effectuate the transfer of moisture from the dry channel  208  to the wet channel  210 . Alternatively, both active and passive mechanisms are combined to ensure continuous and efficient movement of water from the dry channel  208  to the wet channel  210 . 
     In another embodiment of the disclosure shown in  FIG.  2   , an external source is used to replenish the water in the wet channel  210 . The external source may comprise a connection to a local water supply and/or distilled water that is obtained from a reservoir. 
     In an embodiment, the heat exchanger  202  comprises a plurality of dry channels  208  and a plurality of wet channels  210 . In an embodiment, each dry channel  208  is thermally coupled to a single wet channel  210 . In an alternative embodiment, multiple dry channels  208  are thermally coupled to one or more wet channels. In a further embodiment, an alternating series of wet channels  210  and dry channels  208  are interspaced, such that the walls of each are thermally coupled together. In each of the embodiments described above, a channel plate may act as a wall of the heat exchanger  202  and serve to thermally couple the dry and wet channels  208 ,  210  together. In other embodiments, the channels  208 ,  210  are set in alternative arrangements that permit heat transfer between the channels. 
     Although the foregoing discussion refers to the dry channel  208  and wet channel  210  as having “walls”  214 , it will be understood that any three-dimensional arrangement could be used. In an embodiment, the channels  208 ,  210  each comprise a cylinder. Substantially all of the wall of the wet channel  210  may be coated in water. Alternatively, the channels  208 ,  210  may comprise rectangular prisms. In such embodiment, only the “floor” of the wet channel may be coated in water. As will be clear to one of skill in the art, the cooling capacity of the system  200  may be selected by adjusting the number of channels  208 ,  210  and/or the area of contact between the walls  214  of the channels  208 ,  210  and the air passing through the channels  208 ,  210 . Greater contact area will increase the amount of evaporation and/or condensation, thereby enabling both the degree of pre-cooling and the amount of dehumidification to be adjusted based on the desired capacity of the system. 
     In the preferred embodiment, the liquid  216  used in the wet working channel  210  is water. In alternative embodiments, any liquid may be used to facilitate heat transfer between the channels. 
     In the preferred embodiment of  FIG.  2   , exhaust air  220  exits the conditioned room  206  and is delivered to the wet working channel  210 . As the exhaust air passes through the wet working channel  210 , the exhaust air  220  absorbs the liquid  216  on the channel walls  214 . The absorption of liquid  216  removes heat from the wet channel walls  214  and cools the shared wall  217 . In turn, the shared wall  217  cools the dry working channel  208  as well as the outdoor air  224  passing through the dry working channel  208 . As the outdoor air  124  cools, its moisture content is reduced. The partially cooled and dehumidified outdoor air  226  is then delivered to a dehumidifier  204  where it is further dehumidified. After passing through the dehumidifier, the outdoor air  228  is delivered to the conditioned room  106  where it compensates the cooling and moisture loads in the conditioned room, before reaching the parameters for exhaust and exiting the conditioned room. The exhaust air  120  is then delivered to the working channels  208 ,  210  and the cycle begins again. 
     The placement of the two-phase heat exchanger  202  before the dehumidifier  104  dramatically reduces the required capacity of the dehumidifier  104  because the bulk of the cooling and dehumidification process can occur during the pre-cooling process  226  before the air reaches the dehumidifier  104 . In embodiments, the degree of pre-cooling provided by the heat exchanger  202  entirely eliminates the need for subsequent dehumidification  204 . 
     In an embodiment of the heat exchanger  202 , the plates and walls  214  are comprised of a non-woven fabric, such as a Polyethylene Terephthalate (PET) non-woven fabric. In other embodiments, the plates and walls  214  are comprised of materials suitable for heat exchange which include but are not limited to metals and metal alloys, such as aluminum, copper, carbon steel, stainless steel, nickel alloys, and titanium. In another embodiment, the plates and walls  214  are comprised of ceramic material. 
     In an additional embodiment, the heat exchanger  202  may further comprise plates and walls  214  which provide an extended surface so as to increase the contact area between the air and water. In order to reduce a thickness of the liquid on the surface of the walls, the walls  214  may be coated with a hydrophilic surface. 
       FIG.  3    shows a second embodiment of the air conditioning system  300 , wherein the heat exchanger  302  comprises a second dry working channel  318  for additional pre-cooling of the exhaust air  120 . As will be clear to one of skill in the art, any number of wet and/or dry channels may be used based on the desired capacity of the system. 
     In the embodiment of  FIG.  3   , the exhaust air  320  is delivered to the additional dry working channel  318  before moving on to the wet working channel  210 . In this embodiment, the heat exchanger  302  comprises an alternating series of thermally coupled wet working and dry working channels  208 ,  210 ,  318 . 
     In an embodiment of  FIG.  3   , the air conditioning system  300  comprises the same elements and steps as the described embodiment of  FIG.  2   . 
       FIG.  4    shows a system  400  generally equivalent to the embodiment of  FIG.  1    discussed above except as otherwise noted. In system  400 , an exhaust fan  440  is placed along the path of movement of the exhaust air  120 . The exhaust fan  440  functions to expel the exhaust  120  from the conditioned space  106  and drive it through the wet channel of the heat exchanger  402 . Similarly, a supply fan  450  is placed along the path of movement of the outdoor air  124  into the dry channel of the heat exchanger  402 . As will be clear to one of skill in the art, any number of exhaust fans  440  and supply fans  450  may be used depending on the requirements of the system. Further, the fans  450 ,  440  may be located at one or more points along the respective supply and exhaust air paths in order to effectuate the desired movement of air through the system. In an embodiment, only a single fan is used in order to effectuate the desired movement. 
     In the present disclosure, the heat exchanger  102 ,  202 ,  302 ,  402  acts passively on the exhaust and outside air. No energy is required for the cooling and dehumidification that occurs during the heat exchange process. In alternative embodiments, active cooling and dehumidification may also occur in the heat exchanger in addition to the passive cooling and dehumidification discussed above, thereby improving on the efficiency of traditional active cooling systems while still ensuring the desired degree of cooling is consistently provided. 
     Having thus described in detail preferred embodiments of the present disclosure, it is to be understood that the disclosure defined by the above paragraphs is not to be limited to particular details set forth in the above description as many apparent variations thereof are possible without departing from the spirit or scope of the present disclosure.