Patent Publication Number: US-2021164671-A1

Title: Condensing Dehumidifier for an Arena or the Like

Description:
FIELD 
     The present disclosure relates to air conditioning. More specifically, the present disclosure concerns a condensing dehumidifier for an arena or the like. 
     BACKGROUND 
     Condensing dehumidifiers are well known in the art. They work by drawing moist air with a fan over the refrigerated coil of an evaporator  10 , which condenses the water vapors in the air (See  FIG. 1 ). The air is then reheated by a condenser coil and released into the room. The humidity is collected in a tank or pan  12  or discharged to the drain by a pipe. Similarly than with a refrigerator or an air conditioning system, a condensing dehumidifier requires a compressor and refrigerant in its design. 
     Condensing dehumidifiers work most effectively at higher ambient temperatures with a high dew point temperature. In cold climates, such as in an arena, the process is less effective. 
       FIG. 1  shows typical operating temperatures of an evaporator  10  according to the prior art having three rows of tubes  14 . 
     Providing the well-known refrigerant fluid R134a (1,1,1,2-Tetrafluoroethane) pumped by the compressor, the refrigerant temperature at the inlet  16  of the evaporator  10  is around −10° C. For an air entering the evaporator  10  at around between 13° C. and 15° C. and having a relative humidity of between about 80% and 60%, the temperature at the inlet of the evaporator is typically −2° C. This results in the formation of ice (not shown) on the evaporator  10 . 
       FIG. 2  is the enthalpy diagram of the R134a refrigerant fluid for a condensing dehumidifier according to the prior art, that incorporates the evaporator  10  under the above-mentioned operating conditions. 
     The point  18  corresponds to the entry of the refrigerant in the compressor, and the end of the expansion in the evaporator at −10° C., wherein the temperature of the refrigerant is at 10° C. 
     The points  22  and  24  on the diagram correspond respectively to the start and end of the condensation at around 40° C. 
     Point  26  corresponds to the maximum of undercooling, while point  28  corresponds to the entry point in the evaporator  10 . The cycle ends at point  18  discussed above. 
     The compression work of the R134a refrigerant fluid expressed in kj/kg is shown as the delta enthalpy  30 . 
     However, the power consumption (in kw/h) for each kg of water withdrawn should not be considered instantly, but within a 24 hours period. 
     When the air is below a certain temperature, about 18° C., some of the water condensing on to the evaporator  10  turns to ice before it has time to drip into the pan  12 . 
     As the frost builds up, it insulates the evaporator and reduces the amount of water vapor condensing on it. If this went on unchecked the dehumidifier would eventually be damaged, causing refrigerant leaks. 
     To protect the dehumidifier and to enable it to remove more water from the air, the dehumidifier stops cooling the evaporator coil to allow the ice to melt. A sensor detects the formation of ice, triggers a switch, which turns off the compressor and the evaporator is no longer cooled. The fan continues to run so that the flow of air from the room can pass over the evaporator and assist with the thawing process. 
     With reference to the psychometric diagram shown in  FIG. 6 , the evaporator  10 , under the above-described operating conditions, will take 3 g (see  33 ) of water per kg of treated air while requiring 25 kj (31.5 kj (see point  32 )−6 kj (see point  34 )), resulting in 8.3 kj per gram of water taken from the air. 
     However, as mentioned hereinabove, there will be formation of ice in the evaporator  10 . That ice has to be melted frequently and about 8.3 kj of energy for each g of water taken will have to be provided therefore. Current dehumidifiers operating in relatively cold conditions, such as in an arena, spend 25 to 50 percent of their time and energy to defrosting. 
     The energy that has to be provided increases the energy balance of the dehumidifiers from the prior art over a 24-hour period. 
     A dehumidifier operating within the 5° C. to 20° C. that prevents the formation of ice into the evaporator is therefore desirable. 
     SUMMARY 
     According to an illustrative embodiment, there is provided a dehumidifier for operation within the 5° C. to 20° C. range and within the 50 to 100 percent relative humidity range of an air, comprising: 
     an evaporator having an evaporation temperature maintained at −4° C. or above, resulting in a temperature within the evaporator and at the outlet thereof being greater than 0° C. 
     Such a dehumidifier prevents the formation of ice in the evaporator which yields the following benefits:
         the evaporator can be operated to its full power all the time;   removes the need to regularly defrost the evaporator;   increase the quantity of water withdrawn in the air in a day; and   therefore reduce the power consumption for each kg of water taken in the air.       

     Also, consequently, or proportionally to the decrease of electrical energy required per kg of water withdrawn, the quantity of heat released into the ambient is decreased. 
     Other objects, advantages and features of the dehumidifier will become more apparent upon reading the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the appended drawings: 
         FIG. 1 , which is labelled “Prior Art” is a schematic view of an evaporator according to the prior art further showing typical operating conditions therefore; 
         FIG. 2 , which is labeled “Prior Art” is an enthalpic diagram of the R134a refrigerant fluid, showing the typical operating conditions of a dehumidifier from the prior art; 
         FIG. 3  is a schematic view of a dehumidifier according to an illustrative embodiment; 
         FIG. 4  is a schematic view of the evaporator and condenser part of the humidifier from  FIG. 3 , showing the change in the air condition as it moves therethrough; 
         FIG. 5  is an enthalpic diagram of the R134a refrigerant fluid, showing the typical operating conditions of the dehumidifier from  FIG. 3 ; and 
         FIG. 6  is a psychometric diagram showing the comparative evolution of the air hygrometry as it passes through the evaporator from  FIG. 3  and through the evaporator from  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, similar features in the drawings have been given similar reference numerals, and in order not to weigh down the figures, some elements are not referred to in some figures if they were already identified in a precedent figure. 
     The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more. 
     As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements. 
     A dehumidifier  40  for an arena according to a first illustrative embodiment will be described with reference to  FIG. 3 . 
     The dehumidifier  40  comprises an evaporator  42 , including a condensate pan  43  thereunder, a condenser  44 , a compressor  46 , a bypass circuit  48 , including two valves  50  and  82 , and a fan (not shown) that conventionally draws humid air through the evaporator  42  and condenser  44 . 
     For illustrative purposes, the refrigerant used in the dehumidifier  40  is the well-known R134a (1,1,1,2-Tetrafluoroethane) refrigerant fluid. However, other refrigerant fluids, such as, without limitations, the R404/507 can also be used. 
     The evaporator  42  is selected so as to yield a latent power/total power ratio that allows a very low T° delta (evaporation/treated air) (typically of less than 10° K) without the formation of ice. 
     The evaporator  42  includes seven (7) rows of tubes  52  so as to increase the surface contact of the humid air therewith (see  FIG. 4 ). According to other embodiments, the evaporator includes another number of rows of tubes above five (5) rows of tubes  52 . 
     The evaporator  42  is further configured to drain the water to the condensate pan  43  as quickly as possible to prevent ice formation. For such purpose, the evaporator  42  has a height of about 200 mm. According to another embodiment, the evaporator has another height that is lower than about 300 mm. 
     According to another embodiment (not shown), the condensate pan is substituted by another water collecting element, such as, without limitations, a tank. 
     The compressor  46  is for example a Copeland Scroll™ ZB26 compressor. An illustrative embodiment of a dehumidifier is however not limited to such compressor model. 
     The compressor  46  pumps the refrigerant fluid through the condenser  44  and then the evaporator  42 . 
     Since evaporators, condensers, compressors and refrigerant fluids are believed to be well-known in the art, they will not be described herein in more detail for concision purposes. 
     Further characteristics of the dehumidifier  40  will become more apparent upon reading the following description of the operation thereof, with reference to  FIGS. 3 to 5  and with an air entering the dehumidifier  40 , and more specifically the evaporator  42 , at 15° C. with a relative humidity of  60  percent. 
     The refrigerant fluid enters the evaporator  42  at −3° C. (see point  60  on  FIGS. 3 and 5 ). The expansion of the fluid starts at point  62  and ends at point  64  in  FIG. 5 ). The temperature of the fluid remains at −3° C. during the expansion, which corresponds to the evaporation temperature. 
     The refrigerant fluid is then pumped through the compressor  46  thereby (see arrow  66  in  FIG. 3 ), wherein the refrigerant fluid exits the evaporator at 8° C. and enters the compressor  46  at 10° C. (see point  68 ). 
     The refrigerant fluid then enters the condenser at 45° C. (see point  70 ) and the condensation starts and ends at 25° C. (see points  72  and  74  respectively). Then the fluid enters a sub cooling phase at 15° C. which ends at point  76 . 
     The work  78  of the compressor  46 , which occurs between point  68  and  70 , is lower than for the dehumidifier from the prior art, as shown in  FIG. 2 , for a same refrigerant fluid (R134a according to the illustrated embodiment). 
     With reference to  FIGS. 3 and 4 , it is interesting to note that the air entering the evaporator  42  at 15° C. (see arrows  76 ) exits the evaporator  42  at 1° C. (see arrows  78 ), thereby preventing the formation of ice in the evaporator  42 . 
     As it is well-known to a person skilled in the art, the compression work varies depending on the refrigerant fluid used and compressor  46 . However, for same refrigerant fluid and compressor, the compression work remains lower for the dehumidifier  40  compared to a dehumidifier from the prior art, considering an operating range of operation between 5° C. to 20° C. Also, with reference to  FIGS. 2 and 5 , the delta between evaporation and condensation temperatures is minimized. 
     The air then continues through the condenser  44  where it exits at 20° C. (see arrows  80 ). 
     Returning to  FIGS. 3 and 5 , while the evaporation temperature according to the illustrated embodiment is −4° C., it has been found that maintaining the evaporator temperature at any value of −4° C. and above allows maintaining the air temperature at the exit of the evaporator  42  above the freezing point, thereby preventing the formation of ice therein. 
     To maintain such a temperature in the evaporator  42 , a bypass circuit  48  is provided, wherein refrigerant exiting the compressor  46  at 45° C. is directed into the evaporator  42 . The bypass circuit  48  includes a first valve  50  between the compressor  46  and evaporator  42 , and a second valve  82  is provided between the condenser  44  and evaporator  42 . 
     According to another embodiment (not shown), the bypass circuit  48  is omitted. According to still another embodiment, the compressor&#39;s pump speed is varied to maintain the temperature in the evaporator  42  to the desired value. According to a further embodiment, the dehumidifier includes a power capacity reducing system for the compressor. 
     With reference to  FIG. 6 , the evaporator  42  withdraws 2.5 g of water per kg of air (see  84 ), while using 25 kj/g (31.5 kj-6.0 kj) (point  32 -point  86 ). This results in 8 kj/g of withdrawn water. This is compared to the 8.3 kj/g for the system from the prior art described hereinabove. However, as already mentioned, additional energy is required in the systems form the prior art to melt the ice formed into the evaporator. 
     Considering the above, and the fact that the work of the compressor is lower in the dehumidifier  40  compared to in systems from the prior art (see  78  on  FIG. 5  vs  30  in  FIG. 2 ), it results that the dehumidifier  40  is more efficient and consumes less energy. 
     However, the advantages of the dehumidifier  40  compared to systems from the prior art do not end there. 
     First the number and dimensions of the components of the dehumidifier  40  is reduced compared to dehumidifiers from the prior art. This is allowed by the improved efficiency of the overall system  40  to withdraw water vapor from the air compared to systems from the prior art. 
     Since the quantity of water withdrawn from the air is increased, the air flow is lower. This results in less work for the fan, less clogging of the fan filters, and therefore less frequent changes thereof, and a reduced sound level of the overall system  40 . 
     It is to be noted that many modifications could be made to the dehumidifier  40  described hereinabove and illustrated in the appended drawings. For example:
         when greater dehumidifying power is required, a dehumidifier according to another embodiment may include a plurality of evaporators  42 , each equipped with its own condensate pan  43 . The power and dimensions of the other components are of course adapted to the application;   other compressor and/or refrigerant fluid than the ZB26 and R134a respectively can be used;   the heat returned by the dehumidifier  40  in its surrounding may be lowered by heating the condensed water using discharge gas from the condenser  44 . Thus, the condensates which flow at a temperature of 1 to 3° C., can be warmed up to 25° C., yielding a dissipated heat gain of 91.96 kJ/kg of water drained ((25−3)×4.18);   the condenser can be positioned outside while the remaining components of the dehumidifier remains inside. This would allow the dehumidifier to operate in a dehumidification/heating during winter and dehumidification/cooling during summer.       

     While the dehumidifier  40  has been described with reference to its use in an arena, an illustrative embodiment of a dehumidifier can also be used in other contexts such as without limitation in the food industry, and in any spaces wherein significant amounts of water is present in the air, including slaughterhouses, sports halls, churches, mines, ship holds, storage, bridge pilings, underground parking, heritage buildings, sheers, forage and cereal dryers, etc. 
     Although a dehumidifier has been described hereinabove by way of illustrated embodiments thereof, it can be modified. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that the scope of the claims should not be limited by the preferred embodiment but should be given the broadest interpretation consistent with the description as a whole.