desiccant dehumidification wheel desiccant dehumidification wheel

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Design Considerations and Control StrategiesControl of moisture levels in spaces or process air streams isgenerally accomplished by either regulating reactivation heator bypassing a portion of the air around the dehumidificationwheel. The response time, energy efficiency, and dewpointbandwidth determine what level of control is required. Thedegree of control varies from the simplest form of on/offcontrol to maintain a space condition, to the most comprehensivewhich would include wheel bypass dampers (andperhaps face dampers) plus reactivation heat modulated tocontrol an exit exhaust air temperature.Humidity sensors vary in type, principle of operation, accuracy,and precision, and need to be chosen to suit the controlrequirements. Placement of sensors in well-mixed airstreams is critical to performance monitoring.Reactivation heaters should be equipped with suitable safetydevices and interlocks to prevent overheating the wheel.The maximum operating temperature is 350°F. Separatehigh temperature cutouts should be provided if this temperaturecould be exceeded during operation. Reactivation airflowshould be maintained and proven anytime reactivationheat is energized.Software Selection ProgramFor a more comprehensive analysis of performance, NovelAire offers a model selection software program available fordownload at www.novelaire.com. The program models the performance of a wide array of input parameters to ensure theproper selection of desiccant wheel size and type.NovelAire Desiccant Wheel Simulation Software
Wheel PerformanceNovelAire desiccant wheels are designed to operate witheither a 25% area for reactivation and 75% area for process(25/75 split), or with 50% area for reactivation and 50% forprocess (50/50 split). Generally, the 25/75 split is used forindustrial dehumidification, low dewpoint and compact desiccantcooling applications. The 50/50 split is more often usedfor commercial cooling applications, or application where lowtemperature waste heat is available for reactivation.NovelAire desiccant wheels are designed to be reactivatedwith either electric resistance, (indirect) steam, (indirect) hotwater, or direct (or indirect) fired natural (or propane) gas.Additionally, solar or waste heat sources may be utilized.NovelAire desiccant wheels are designed for regenerationtemperatures up to a maximum temperature of 350°F.In addition to the regeneration temperature and cassette zoning,several other factors influence the performance of thedesiccant wheel. Process and regeneration inlet humidityand temperature, regeneration to process flow ratio, facevelocity, and wheel rotational speed all has an impact onperformance. The following curves show the relationshipbetween some of these parameters on performance for theWSG desiccant wheel.600 sfpm, Regen Ratio = 0.33, Tr=284F120160WSG WheelPerformance600 sfpmR/P ratio .33Tr= 284°FOutlet Moisture, gr/lb100806040200140120100806040Outlet Temperature,FGrains Out, 95 FGrains Out, 75 FGrains Out, 55 FTout, 95 FTout, 75 FTout, 55 F0 50 100 150 200Inlet Moisture, gr/lb400 sfpm, Regen Ratio = 1.0, Tr=190F120160WSG WheelPerformance400 sfpmR/P ratio 1.0Tr= 190°FOutlet Moisture, gr/lb100806040201401201008060Outlet Temperature FGrains Out, 95 FGrains Out, 75 FGrains Out, 55 FTout, 95 FTout, 75 FTout, 55 F0400 50 100 150 200Inlet Moisture, gr/lb
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desiccant dehumidification wheel desiccant dehumidification wheel

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