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<p class="MsoNormal">I have a project aiming for careful temperature and humidity control of an interior zone – looking for cool, dry space conditions at 50F and 40% rh – which results in an absolute humidity of 0.003 lb//lb-da or 21 grains.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The mechanical system has:<o:p></o:p></p>
<p class="MsoNormal"> Enthalpy heat recovery wheel<o:p></o:p></p>
<p class="MsoNormal"> Solid desiccant dehumidification – only on the outdoor air stream<o:p></o:p></p>
<p class="MsoNormal"> Cooling coil served by low temperature chilled water (glycol)<o:p></o:p></p>
<p class="MsoNormal"> Reheat<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">What I am seeing is excessive dehumidification by the desiccant system – and corresponding humidification in the same timestep – especially in the summer months. In the extreme, there are some timesteps where the absolute enthalpy leaving
the desiccant unit is negative (a neat trick). The problem occurs when I specify an enthalpy heat recovery wheel. It does not occur when I specify a sensible heat recovery wheel. I have tried broadening the deadband between max and min humidity without
resolving the issue.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My hypothesis is that while the desiccant dehumidification sees the heat recovery wheel output air conditions, it is “controlling” to conditions upstream of the wheel.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have attached a sample project that displays the same behavior – significant humidification in the summer months when an enthalpy wheel is included but none when only a sensible wheel is used. The sample project hourly report is also
attached as a spreadsheet. I ran it on Toronto CWEC2016 weather but I see the same phenomena on other weather data sets.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am running the model DOE-2.2 in build 7175 but it also occurs using 7173. DOE-2.3 does not have the desiccant keywords implemented so there is no help there.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I would appreciate any suggestions and or observations. Have others also encountered this situation?
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Brian<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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