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HVAC System Diagram AirLoopHVAC:UnitaryHeatCool Coil:Cooling:DX: SingleSpeed Coil:Heating:GasFan:OnOff Air Supply Inlet Node Air Supply Outlet Node Heating.

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Presentation on theme: "HVAC System Diagram AirLoopHVAC:UnitaryHeatCool Coil:Cooling:DX: SingleSpeed Coil:Heating:GasFan:OnOff Air Supply Inlet Node Air Supply Outlet Node Heating."— Presentation transcript:

1 HVAC System Diagram AirLoopHVAC:UnitaryHeatCool Coil:Cooling:DX: SingleSpeed Coil:Heating:GasFan:OnOff Air Supply Inlet Node Air Supply Outlet Node Heating Coil Inlet Node Cooling Coil Inlet Node Zone [Living] Living Zone Air Node AirTerminal: SingleDuct:Uncontrolled DXDehumidifier Outlet Node List: Living Supply Nodes List: Living Exhaust Nodes DXDehumidifier Inlet Node Zone [RA Duct Zone] RA Plenum Air Node Living Return Node Air Demand Outlet Node Splitter Air Demand Inlet Node Living Supply Node Plenum ZoneHVAC: Dehumidifier:DX Single-Family Infiltration & Ventilation Modeling25 May 2011 No outside air flow (exhaust or supply) via HVAC system

2 HVAC System Diagram – with ERV AirLoopHVAC:UnitaryHeatCool Coil:Cooling:DX: SingleSpeed Coil:Heating:GasFan:OnOff Air Supply Inlet Node Air Supply Outlet Node Heating Coil Inlet Node Cooling Coil Inlet Node Zone [Living] Living Zone Air Node AirTerminal: SingleDuct:Uncontrolled DXDehumidifier Outlet Node List: Living Supply Nodes List: Living Exhaust Nodes DXDehumidifier Inlet Node Zone [RA Duct Zone] RA Plenum Air Node Living Return Node Air Demand Outlet Node Splitter Air Demand Inlet Node Living Supply Node Plenum ZoneHVAC: Dehumidifier:DX Single-Family Infiltration & Ventilation Modeling25 May 2011 Outside air flow (supply and exhaust) via ERV Fan:OnOff ERV Exhaust Fan Outlet Node ERV Exhaust Fan Inlet Node ERV Outside Air Inlet Node ERV Supply Fan Inlet Node Living Exhaust Node ERV Supply Fan Outlet Node

3 Infiltration Calculations Single-Family Infiltration & Ventilation Modeling25 May 2011 EnergyManagementSystem:Program, InfiltrationProgram, Set Tdiff = Tin - Tout, Set DeltaT Tdiff, Set c = , Set Cs = , Set Cw = , Set n =0.67, Set sft = , Set Qn = (((c*Cs*(DeltaT^n))^2)+(((c*Cw)*((sft*Vwind)^(2*n)))^2))^0.5, !Section above: !This is equation 41 + equation 42 from ASHRAE Fundamentals 2005 Ch 27 !"Enhanced Model. This section presents a simple, single-zone approach !to calculating air infiltration rates in houses based on the AIM-2 model !(Walker and Wilson 1998). The airflow rate due to infiltration is !calculated using: ! Qs = c * Cs * DeltaT^n (41) ! Qw = c * Cw (sU)^2n (42) ! where: Qs = stack airflow rate, m3s ! Qw = wind airflow rate, m3/s ! c = flow coefficient, m3/(s/Pa^n) ! Cs = stack coefficient, (Pa/K)^n ! Cw = wind coefficient, (Pa-s^2/m^2)^n ! s = shelter factor ! Several assumptions made when calculating Cs, Cw, s ! including: n = 0.67 ! Equation (39) then describes superposition for the total infiltration rate: ! Q = ((Qs^2)+(Qw^2))^0.5 Set Tdiff = Tin - Tout, Set DeltaT Tdiff, Set QWH = WH_sch* , Set Qrange = Range_sch* , Set Qdryer = Clothes_dryer_sch* , Set Qbath = Bath_sch* , Set Qu = QWH+Qrange+Qbath+Qdryer+DuctLeakOAMakeupFlowRate, Set Qb = 0, Set faneff_wh = , Set WholeHouseFanPowerOverride= (QWH*300)/faneff_wh, Set faneff_sp = , Set RangeHoodFanPowerOverride = (Qrange*300)/faneff_sp, Set BathExhaustFanPowerOverride = (Qbath*300)/faneff_sp, Set Infilflow = ((Qu^2) + (Qn^2))^0.5, Set InfMechVent = Qb + Infilflow; !Two lines above described by Equation (43) in ASHRAE Fundamentals 2005 Ch 27 !Says that you can combine residential infiltration and mechanical ventilation flows: ! Qcomb = Qbal + ((Qunbal^2)+(Qinfil^2)) Qn = infiltration flow Qu = unbalanced exhaust flow = QWH + Qrange + Qdryer + Q bath + DuctLeakage QWH = Whole house exhaust fan Qrange = Kitchen range hood Qbath = Bath point exhaust Qdryer = Dryer exhaust DuctLeakage = Calculated from DuctLeakageProgram Qb = balanced ventilation = 0 InfMechVent = Total flow Parameters to change infiltration rates

4 Building America House Simulation Protocol, pg 16: “Additional air exchange whole-house mechanical ventilation shall be calculated assuming a single point exhaust ventilation system with the same ventilation rate used for the NCTH, up to a maximum value consistent with the rate recommended by ASHRAE Whole-house mechanical ventilation air shall be added to the natural infiltration rate in quadrature, assuming no heat recovery. Ventilation fan energy use for the Benchmark shall be calculated using a fan efficiency of 0.5 W/cfm. In addition to whole-house ventilation, the Benchmark shall include a kitchen range hood, spot ventilation fan in each bathroom, and exhaust from the clothes dryer. The flow rates of the kitchen and bathroom fans shall be the same as those in the NCTH, and their efficiency shall be assumed to operate 60 min/day (between 6:00 pm and 7:00 pm), and each bathroom fan (including those in central restrooms) is assumed to operate 60 minutes per day (between 7:00 am and 8:00 am). The clothes dryer fan will operate for 60 minutes per day between 11:00 am and 12:00 pm. Interactive effects between these spot exhaust ventilation fans and natural infiltration shall be included in the analysis.” Ventilation Components & Schedules Single-Family Infiltration & Ventilation Modeling25 May 2011

5 ASHRAE 62.2 Ventilation Requirements Q fan = fan flow rate in L/s; A floor = floor area in m 2 ; N br = number of bedrooms For N br = 3, A floor = 222 m 2 (2400 ft 2 ): Q fan = 25.1 L/s = m 3 /s = 54 cfm Single-Family Infiltration & Ventilation Modeling25 May 2011 ASHRAE , Section 4.1: “A mechanical exhaust system, supply system, or combination thereof shall be installed for each dwelling unit to provide whole-building ventilation with outdoor air each hour at no less than the rate specified in Table 4.1a and Table 4.1b, or, equivalently, Equations 4.1a and 4.1b, based on the floor area of the conditioned space and number of bedrooms.”

6 Modeling Results – Exhaust Flows – Summer Design Day Single-Family Infiltration & Ventilation Modeling25 May 2011

7 Modeling Results – Qu & Qn – Summer Design Day Single-Family Infiltration & Ventilation Modeling25 May 2011

8 Modeling Results – Total Flow – Summer Design Day Single-Family Infiltration & Ventilation Modeling25 May 2011

9 Modeling Results – Hours not meeting ASHRAE Single-Family Infiltration & Ventilation Modeling25 May 2011 RunHours not met (Qn)Hours not met (Total Flow) CHI_ICF4in_BaseInfil_GndTemps 5450 CHI_ICF4in_Infil_a_GndTemps 7760 CHI_ICF4in_Infil_b_GndTemps 7800 PHX_ICF4in_BaseInfil_GndTemps PHX_ICF4in_Infil_a_GndTemps PHX_ICF4in_Infil_b_GndTemps 30190

10 Natural Ventilation Calculations Single-Family Infiltration & Ventilation Modeling25 May 2011 EnergyManagementSystem:Program, NaturalVentilationProgram, Set Tdiff = Tin - Tout, Set DeltaT Tdiff, Set Phiin Tin Win Pbar, ! RhFnTdbWPb: Calculates RH (fraction) from DB, Humidity Ratio, Barometric Pressure Set Hin Tin Phiin Pbar, ! HFnTdbW: Calculates Enthalpy of moist air (J/kg) from DB and Humidity Ratio Set NVArea = , !Not clear how this number is determined, but it is cm^2 Set Cs = , Set Cw = , Set MaxNV = , Set SGNV = (NVAvail*NVArea)*((((Cs*DeltaT)+(Cw*(Vwind^2)))^0.5)/1000), !Line above based on equation (40) from ASHRAE Fundamentals 2005 Ch 27 !This is the basic model for calculating the airflow rate due to infiltration ! Q = AL/1000((Cs*DeltaT)+(Cw(U^2))^0.5 ! where: Q = airflow rate m3/s ! AL = effective air leakage area, cm2 ! DeltaT = Avg indoor-outdoor temp difference, K ! Cw = wind coefficient ! U = avg windspeed measured at local weather station If Wout NVSP, !Line above sets outdoor conditions for nat vent !Wout is Outdoor Humidity Ratio; Phiin is RH; Tin is Zone MAT; NVSP is NatVentTemp Schedule Value. Set NVadj1 = (Tin - NVSP)/(Tin - Tout), Set NVadj2 NVadj1 1, Set NVadj3 NVadj2 0, Set NVadj = SGNV*NVadj3, Set NatVentFlow NVadj MaxNV, Else, Set NatVentFlow = 0, EndIf; Qn = infiltration flow Qu = unbalanced exhaust flow = QWH + Qrange + Qdryer + Q bath + DuctLeakage QWH = Whole house exhaust fan Qrange = Kitchen range hood Qbath = Bath point exhaust Qdryer = Dryer exhaust DuctLeakage = Calculated from DuctLeakageProgram Qb = balanced ventilation = 0 InfMechVent = Total flow

11 Modeling Results – BEOpt Vent Options Single-Family Infiltration & Ventilation Modeling25 May 2011

12 Modeling Results – BEOpt NatVent Options Single-Family Infiltration & Ventilation Modeling25 May 2011

13 Modeling Results – BEOpt Slab Options Single-Family Infiltration & Ventilation Modeling25 May 2011

14 Modeling Results – NatVent Single-Family Infiltration & Ventilation Modeling25 May 2011 This report variable represents the sensible heating energy in Joules that is actually supplied by the system to that zone for the timestep reported. This is the sensible heating rate multipled by the simulation timestep. “Zone/Sys Sensible Heating (and Cooling) Energy all report the heating or cooling delivered by the HVAC system to a zone. These values are calculated by multiplying the supply air mass flow rate by the difference between the supply air temperature and the zone air temperature. This does not always indicate the operation of heating or cooling coils. For example, cooling will be reported if the supply air is cooled due to the introduction of outside air, event if all coils are off.” I/O pg. 168

15 Modeling Results – NatVent Single-Family Infiltration & Ventilation Modeling25 May 2011

16 Modeling Results – NatVent Single-Family Infiltration & Ventilation Modeling25 May 2011

17 Modeling Results – NatVent Single-Family Infiltration & Ventilation Modeling25 May 2011 This is the total (sensible plus latent) cooling output of the DX coil in Joules over the timestep being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. I/O pg. 168

18 Modeling Results – NatVent - SFO Single-Family Infiltration & Ventilation Modeling25 May 2011

19 Modeling Results – NatVent - SFO Single-Family Infiltration & Ventilation Modeling25 May 2011

20 Modeling Results – MechVent (w and w/o nat vent) Single-Family Infiltration & Ventilation Modeling25 May 2011

21 Modeling Results – MechVent (w and w/o nat vent) Single-Family Infiltration & Ventilation Modeling25 May 2011

22 Modeling Results – MechVent (w and w/o nat vent) Single-Family Infiltration & Ventilation Modeling25 May 2011

23 Modeling Results – MechVent (w and w/o nat vent) Single-Family Infiltration & Ventilation Modeling25 May 2011


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