Patent Publication Number: US-10323868-B2

Title: Multi-coil microchannel evaporator

Description:
FIELD 
     Embodiments disclosed herein generally relate to providing good heat transfer performance and efficiency and reducing pressure drop through microchannel coil evaporators. In particular, apparatuses, systems and methods are directed to providing good heat transfer performance, capacity, and efficiency, and while reducing pressure drop through multi-coil microchannel evaporators. 
     BACKGROUND 
     Single circuit refrigerant systems, for example using an air to refrigerant heat exchanger as an evaporator can be susceptible to higher than desired pressure drop, which can impact maximum heat transfer performance from being achieved thereby affecting capacity and/or efficiency. Use of a single microchannel evaporator in such systems for example in applications of relatively high capacity (e.g. tonnage) can be susceptible to such effects. 
     SUMMARY 
     Embodiments disclosed herein generally relate to providing good heat transfer performance and efficiency and reducing pressure drop through microchannel coil evaporators. In particular, apparatuses, systems and methods are directed to providing good heat transfer performance, capacity, and efficiency, and while reducing pressure drop through multi-coil microchannel evaporators. 
     In an embodiment, methods, systems, and apparatuses are described that include the use of a multi-coil microchannel evaporator. 
     In an embodiment, the multi-coil microchannel evaporator is implemented in a refrigerant system that is a single circuit. A refrigerant system of a single circuit includes one or more compressors, a condenser, an evaporator, and an expansion device. In an embodiment, a single circuit includes a single working fluid, e.g. refrigerant, refrigerant blend. 
     In an embodiment, the multi-coil microchannel evaporator is an air to refrigerant type heat exchanger. 
     In an embodiment, the multi-coil microchannel evaporator includes a distribution to the multiple coils of the multi-coil microchannel evaporator. 
     In an embodiment, the distribution to the multi-coil microchannel evaporator includes one or more separations to transmit refrigerant to each of the coils of the multi-coil microchannel evaporator and one or more junctions to transmit refrigerant from the coils. 
     In an embodiment, the multi-coil microchannel evaporator has an even number of coils. In an embodiment, the multi-coil microchannel evaporator has its coils configured to be assembled to a height of about six feet tall and to a width of about eight feet wide. In an embodiment, the coils of the multi-coil microchannel evaporator are of similar or the same size. 
     In an embodiment, the distribution utilizes the number and size of each coil in the multi-coil microchannel evaporator to obtain a desired, targeted, and/or optimal refrigerant distribution. 
     In an embodiment, a method of refrigerant flow through a single circuit refrigerant system includes distributing refrigerant to coils of a multi-coil microchannel evaporator. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the multi-coil evaporator will become better understood when the following detailed description is read with reference to the accompanying drawings. 
         FIG. 1  is a schematic diagram of a refrigerant circuit, according to an embodiment. 
         FIG. 2  is a perspective view of an embodiment of a refrigerant circuit with a multi-coil evaporator. 
         FIG. 3  is a perspective view of the multi-coil evaporator of  FIG. 2 . 
     
    
    
     While the above-identified figures set forth particular embodiments of a multi-coil evaporator, other embodiments are also contemplated, as noted in the descriptions herein. In all cases, this disclosure presents illustrated embodiments of a multi-coil evaporator by way of representation but not limitation. Numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of a multi-coil evaporator described and illustrated herein. 
     DETAILED DESCRIPTION 
     Embodiments disclosed herein generally relate to providing good heat transfer performance and efficiency and reducing pressure drop through microchannel coil evaporators. In particular, apparatuses, systems and methods are directed to providing good heat transfer performance, capacity, and efficiency, and while reducing pressure drop through multi-coil microchannel evaporators. 
       FIG. 1  is a schematic diagram of a heat transfer or refrigerant circuit  10 , according to an embodiment. The refrigerant circuit  10  generally includes a compressor  12 , a condenser  14 , an expansion device  20 , and an evaporator  16 . The refrigerant circuit  10  is exemplary and can be modified to include additional components. For example, in an embodiment the refrigerant circuit  10  can include other heat exchangers such as for example an economizer heat exchanger, one or more flow control devices, a receiver tank, a dryer, a suction-liquid heat exchanger, or the like. In an embodiment, the refrigerant circuit  10  can include a plurality of compressors  12 . In an embodiment, the plurality of compressors  12  can include compressors having the same or different capacities. 
     The refrigerant circuit  10  can generally be applied in a variety of systems used to control an environmental condition (e.g., temperature, humidity, air quality, or the like) in a space (generally referred to as a conditioned space). Examples of systems include, but are not limited to, heating, ventilation, and air conditioning (HVAC) systems, transport refrigeration systems, or the like. 
       FIGS. 2 and 3  respectively show a refrigerant circuit  100  with a multi-coil evaporator  116  and the multi-coil evaporator  116  alone. 
     The refrigerant circuit  100  includes a compressor  112 , a condenser  114 , an expansion device  120 , and the multi-coil evaporator  116  (hereafter evaporator  116 ). A refrigerant flows through the refrigerant circuit as a working fluid. As with the refrigerant circuit  10 , the refrigerant circuit  100  is also exemplary and can be modified to include additional components. For example, in an embodiment the refrigerant circuit  100  can include other heat exchangers such as for example an economizer heat exchanger, one or more flow control devices, a receiver tank, a dryer, a suction-liquid heat exchanger, or the like. 
     The refrigerant circuit  100  can generally be applied in a variety of systems used to control an environmental condition (e.g., temperature, humidity, air quality, or the like) in a space (generally referred to as a conditioned space). Examples of systems include, but are not limited to, heating, ventilation, and air conditioning (HVAC) systems, transport refrigeration systems, or the like. 
     In an embodiment such as shown in  FIG. 2 , the refrigerant circuit  100  includes a plurality of compressors  112 . In an embodiment, the plurality of compressors  112  can include compressors having the same or different capacities. Three compressors  112  are shown, such as for example scroll compressors, however, it will be appreciated that more or less than three compressors may be implemented in the refrigerant circuit  100 . It will also be appreciated that the compressor(s)  112  may be scroll compressors, but can be other types of compressors. For example, the compressor(s)  112 , may be screw compressor, rotary compressor, reciprocating compressor, and/or centrifugal compressor types. 
     The condenser  114  is fluidly connected with the compressor(s)  112 . The compressors  112  each include a discharge  122  which is fluidly connected with fluid line  126  to the condenser  114 . In the embodiment shown, the fluid line  126  is fluidly connected between the two coils of the condenser and feeds two lines from the fluid line to an upper and lower part of each coil or side relative to the fluid line  126 . In the embodiment shown, the fluid line  126  is fluidly connected to multiple inlets (e.g. four) branching off the fluid line  126 . The condenser  114  is fluidly connected with the evaporator  116  by way of fluid line  128  and fluid line  118 , which are liquid lines. In the embodiment shown, the condenser  114  has four outlets (two per coil side) which are in fluid communication with fluid line  128 , where there is an outlet for the upper part of the coil and an outlet for the lower part of the coil, and where each side of the condenser has two outlets. In the embodiment shown, the fluid lines  128  fluidly join before a valve, e.g., service valve  129 . The evaporator  116  is fluidly connected with the compressor  112  by way of fluid line  119  or suction line. In the figure shown, a single circuit three compressor system is illustrated. The three compressors shown are manifolded together. In an embodiment, each discharge  122  feeds the fluid line  126 . In an embodiment, the three compressor discharge lines plum together behind the unit into one common discharge line (e.g.  126 ). 
     The evaporator  116  herein can provide good heat transfer performance, capacity, and efficiency and while reducing pressure drop or minimizing its effect therethrough. 
     In an embodiment, the evaporator  116  is made of multiple coils  117   a , each having microchannel tubes and has appropriate inlet and outlet headers  117   b ,  117   c  (one set of inlet and outlet headers  117   b ,  117   c  of a coil of microchannel tubes  117   a  are labeled for purposes of description). In an embodiment, the microchannel tubes of a coil  117   a  may have fins disposed between the tubes. As shown, the evaporator  116  has four coils, however, this is exemplary, as less than four or more than four may be implemented. 
     In an embodiment, the evaporator  116  is implemented in a refrigerant system that is a single circuit. A refrigerant system of a single circuit includes one or more compressors, a condenser, an evaporator, and an expansion device. 
     In an embodiment, the evaporator  116  is an air to refrigerant type heat exchanger. 
     In an embodiment, the evaporator  116  has an even number of coils. In an embodiment, the evaporator  116  has its coils configured to be assembled to a height of at or about six feet tall and to a width of at or about eight feet wide. In an embodiment, the coils of the evaporator  116  are of similar or the same size relative to each other. In the embodiment shown, for example, the four coils are the same or about the same size. 
     In an embodiment, the evaporator  116  includes a distribution to the multiple coils of the multi-coil microchannel evaporator. In an embodiment, the refrigerant distribution to the evaporator  116  includes one or more separations to transmit refrigerant to each of the coils of the evaporator  116  and one or more junctions to transmit refrigerant from the coils. 
     With specific reference to the evaporator  116 , the fluid connections for refrigerant flow into and out of the evaporator  116  are further described below. 
     As shown in  FIGS. 2 and 3 , the fluid line  118  delivers refrigerant from the condenser  114  to the evaporator  116 . In an embodiment, the fluid line  118  is a liquid fluid line through which refrigerant flows to the evaporator  116 . A separation or split  130  at the evaporator will separate the liquid flow to flow through multiple lines. In an embodiment, the separation  130  leads to two fluid lines  132  to deliver refrigerant through one of the lines  132  to a top and bottom coil  117   a  on one side of the evaporator  116  and to deliver refrigerant through the other line  132  to a top and bottom coil  117   a  on the other side of the evaporator  116 . It will be appreciated that two fluid lines  132  are shown, however, more than two fluid lines may come from the separation  130  if desired for other designs. 
     Expansion devices  120  are fluidly connected with the fluid lines  132 . The expansion devices  120  further reduce the pressure of the refrigerant, and expand and cool the refrigerant. In an embodiment, one expansion device services multiple coils of the evaporator. For example, each expansion device  120  as shown services two coils  117   a  of the evaporator  116 . 
     In an embodiment, there are multiple expansion devices for a multiple coil evaporator arrangement, where there may be an expansion device for each coil or a number of coils, or sides of coils in the overall evaporator arrangement. 
     In an embodiment, each expansion device  120  is disposed downstream of the separation  130 . In an embodiment, each expansion device  120  is disposed upstream of the separation  134 . In an embodiment, the expansion device  120  is disposed between any separations (e.g.  130 ,  134 ) of the evaporator. It will be appreciated that the expansion devices  120  may be thermostatic expansion devices (e.g. thermostatic expansion valve TXV), but may also be electronic expansion devices and/or valves. The number and placement of the expansion devices can facilitate the metering of refrigerant evenly through the evaporator, for example by balancing the number of expansion devices per side of the coil or portion of the coil, and depending on the number of coils implemented in the evaporator. 
     At separation  134 , the fluid lines  132  are each separated so that refrigerant can flow through multiple lines. In an embodiment, the separation  134  leads to two fluid lines  136  to deliver refrigerant through one of the lines  136  to one of a top and bottom coil  117   a  on one side of the evaporator  116 , and to deliver refrigerant through the other line  136  to the other of the top and bottom coil  117   a  on the same side of the evaporator  116 . It will be appreciated that two fluid lines  136  are shown per separation  134 , however, more than two fluid lines may come from the separation  130  if desired for other designs. 
     The fluid lines  136  respectively lead to a coil  117   a . As shown, each fluid line  136  is fluidly connected with an inlet header  117   b  of a respective coil  117   a . In the embodiment shown, there are four fluid lines  136 , one for each coil  117   a . The refrigerant flow through the coil  117  to undergo heat exchange (i.e. evaporation) before being directed back to the compressor  112 . 
     From each coil, refrigerant flows through the outlet header  117   b , the microchannel tubes, and the header  117   c  to a respective fluid line  138 . As shown, each fluid line  138  is fluidly connected with a header  117   c  of a respective coil. In the embodiment shown, there are four fluid lines  138 , one for each coil. 
     In an embodiment, a junction  140  receives fluid lines  138  to join the fluid flow at the junction  140 . As shown, each of the junctions  140  receives two fluid lines  138  respectively. Two junctions  140  are shown. The junctions  140  are fluidly connected with fluid lines  142 . In an embodiment, the junctions  140  leads to fluid lines  142  to deliver refrigerant through the lines  142  to another junction  144 . It will be appreciated that the two fluid lines  142  shown is exemplary, for example depending on the junctions  140  needed to join fluid lines which may be dependent for example on the number of coils present. 
     Junction  144  is in fluid connection with the fluid line  119 . In an embodiment, the fluid line  119  is a suction line for evaporated refrigerant to flow back to the compressor  112 . 
     In an embodiment, by having multiple relatively shorter coils along with an intermediate drain pan  150  (see e.g.  FIG. 3 ), there is less chance for water to carryover than if we had taller coils that span from the top of the unit to a bottom drain pan (see e.g. bottom of  FIG. 3 ). 
     In an embodiment, the distribution arrangement (e.g., the separations/splits and junctions) utilizes the number and size of each coil in the evaporator  116  to obtain a desired, targeted, and/or optimal refrigerant distribution. In an embodiment, the number of coils present in the arrangement can impact the number of separations and junctions to distribute the refrigerant to the evaporator and to exit the refrigerant from the evaporator to suction. Balancing the number of expansion devices, e.g. per coil, per groups of coils, based on side and/or location of the coil arrangement, and the like, can help meter and distribute refrigerant evenly through the evaporator coils. 
     In an embodiment, the evaporator  116  with its coils, separation/junction, and expansion device arrangement may be implemented and/or optimized in systems with air flows of at or about 200 to at or about 400 cubic feet per minute (CFM). 
     In an embodiment, a bank of multiple coils is oriented in a vertical orientation, and generally in the same plane (e.g. as shown in  FIGS. 2 and 3 ). It will be appreciated, however, that depending on how the airflow is entering the coil, other designs may also include staggering the coils and/or spacing them in a different orientation relative to each other. For example, one or more of the coils shown in  FIGS. 2 and 3  may be moved forward or backward relative to the other coils so that they are not in the same plane, or angled so that they are not all vertically oriented. 
     In an embodiment, a method of refrigerant flow through a single circuit refrigerant system includes distributing refrigerant to coils of a multi-coil microchannel evaporator, including directing the refrigerant to and from the multi-coil microchannel evaporator using the distribution including its separations and junctions. 
     In an embodiment, such as for the example shown in  FIGS. 2 and 3 , airflow can be assumed to be uniform across all coils of the evaporator  116 . The multiple coils (e.g. respective tubes  117   a  and headers  117   b, c ), for example the four coils shown in  FIGS. 2 and 3  are used to reduce refrigerant pressure drop. In an embodiment, the coils are the same height and width. There are two left hand and two right hand coils. Liquid refrigerant separations or splits from a liquid line (e.g. at split  132  from line  118  into two lines  132 , and then to split  134  into two lines  136  after passing through the expansion devices  120 ). In an embodiment, the left hand top and bottom coils are fed refrigerant using one of the expansion devices  120 , which in some embodiments may be a thermal expansion device. The right hand top and bottom coils are fed refrigerant using the other expansion device  120 , which may also be a thermal expansion device. After passing through each coil, the refrigerant is combined into one main suction line (e.g. line  119 ). By having the four coils refrigerant can be distributed to each coil evenly in order to maximize performance. 
     The Table includes averaged data that represents a unit tested (e.g. with the multi-coil configuration of  FIGS. 2 and 3  at 50 ton capacity) at 80/67-95 (Indoor Drybulb/Indoor Wetbulb—Outdoor temperatures). These conditions are the full load rating conditions. The unit was tested with both fin and tube and multi-micro channel evaporator configurations at full load (all components energized—compressors, condenser fan motors, and supply fan motor). The data is compared to a fin and tube evaporator design 
     In general, the data shows similar unit balance points (saturated discharge/suction pressures—Tests/IDs 1 and 2), similar airside pressure drop across evaporator coils (Tests/IDs 3 and 4), similar conditions (Tests/IDs 5 to 7) leaving air Drybulb/Wetbulb temperatures (Tests/IDs 8 and 9). 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 
               
               
                   
               
               
                   
                   
                   
                   
                 Multi-coil 
               
               
                   
                   
                   
                 Fin and Tube 
                 Microchannel 
               
               
                 ID 
                 Test 
                 Units 
                 Evaporator 
                 Evaporator 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 1 
                 System 
                 ° F. 
                 120.9 
                 121.9 
               
               
                   
                 saturated 
               
               
                   
                 discharge 
               
               
                 2 
                 System 
                 ° F. 
                 48.6 
                 48.7 
               
               
                   
                 saturated 
               
               
                   
                 suction 
               
               
                 3 
                 Static pressure 
                 Inches H 2 0 
                 −0.32 
                 −0.35 
               
               
                   
                 drop before coil 
               
               
                 4 
                 Static pressure 
                 Inches H 2 0 
                 −0.93 
                 −1.07 
               
               
                   
                 drop after coil 
               
               
                 5 
                 Entering indoor 
                 ° F. 
                 80 
                 80 
               
               
                   
                 Air 
               
               
                 6 
                 Entering indoor 
                 ° F. 
                 67 
                 67 
               
               
                   
                 Air 
               
               
                 7 
                 Outdoor Air 
                 ° F. 
                 95 
                 95 
               
               
                 8 
                 Leaving indoor 
                 ° F. 
                 58 
                 59 
               
               
                   
                 Air 
               
               
                 9 
                 Leaving indoor 
                 ° F. 
                 56 
                 56 
               
               
                   
                 Air 
               
               
                   
               
            
           
         
       
     
     The multiple coil configuration along with the distribution (separations/junctions) internal to the coil provides the proper refrigerant pressure drop to match balance points. By matching balance points, larger ton units/designs have been able to maintain the same efficiency levels as compared against a fin and tube evaporator currently used in smaller designs. 
     Any one or more of aspects 1 to 6 may be combined with any one or more of aspects 7 to 8, and aspect 7 may be combined with aspect 8. 
     1. An evaporator comprising: multiple coils, the multiple coils are microchannel tubed coils and a distribution to the multiple coils. The distribution to the multiple coils includes one or more separations to transmit refrigerant to each of the coils of the multi-coil microchannel evaporator and one or more junctions to transmit refrigerant from the coils. Multiple expansion devices are in fluid communication with the separations of the distribution. 
     2. The evaporator of aspect 1, wherein the evaporator has an even number of coils. 
     3. The evaporator of aspect 1 or 2, wherein the multiple coils are configured to be assembled to a height of about six feet tall and to a width of about eight feet wide. 
     4. The evaporator of any of aspects 1 to 3, wherein the coils are of similar or the same size. 
     5. The evaporator of any of aspects 1 to 4, wherein the distribution utilizes the number and size of each coil in the multi-coil microchannel evaporator to obtain a desired, targeted, and/or optimal refrigerant distribution. 
     6. The evaporator of aspect 1 to 5, wherein the multiple coils are configured as an air to refrigerant type heat exchanger. 
     7. A refrigerant compression system, comprising: a single circuit that includes one or more compressors, a condenser, and an evaporator of any of aspects 1 to 6. 
     8. A method of refrigerant flow through a single circuit refrigerant compression system includes distributing refrigerant through the evaporator of any of aspects 1 to 6. 
     With regard to the foregoing description, it is to be understood that changes may be made in detail, without departing from the scope of the present invention. It is intended that the specification and depicted embodiments are to be considered exemplary only, with a true scope and spirit of the invention being indicated by the broad meaning of the claims.