Replace Sensible Capacity Curves with ADP/BF

HPXMLtoOpenStudio/measure.rb

@@ -485,7 +485,7 @@ def create_unit_model(hpxml, hpxml_bldg, runner, model, epw_path, epw_file, weat
     @hvac_unavailable_periods = Schedule.get_unavailable_periods(runner, SchedulesFile::Columns[:HVAC].name, @hpxml_header.unavailable_periods)
     airloop_map = {} # Map of HPXML System ID -> AirLoopHVAC (or ZoneHVACFourPipeFanCoil)
     add_ideal_system(model, spaces, epw_path)
-    add_cooling_system(model, runner, weather, spaces, airloop_map)
+    add_cooling_system(runner, model, weather, spaces, airloop_map)
     add_heating_system(runner, model, weather, spaces, airloop_map)
     add_heat_pump(runner, model, weather, spaces, airloop_map)
     add_dehumidifiers(runner, model, spaces)
@@ -1594,7 +1594,7 @@ def add_hot_water_and_appliances(runner, model, weather, spaces)
     Waterheater.apply_combi_system_EMS(model, @hpxml_bldg.water_heating_systems, plantloop_map)
   end
 
-  def add_cooling_system(model, runner, weather, spaces, airloop_map)
+  def add_cooling_system(runner, model, weather, spaces, airloop_map)
     conditioned_zone = spaces[HPXML::LocationConditionedSpace].thermalZone.get
 
     HVAC.get_hpxml_hvac_systems(@hpxml_bldg).each do |hvac_system|

HPXMLtoOpenStudio/resources/hvac.rb

@@ -2993,7 +2993,8 @@ def self.set_cool_rated_shrs_gross(runner, cooling_system)
       p_atm = UnitConversions.convert(1, 'atm', 'psi')
 
       ao = Psychrometrics.CoilAoFactor(runner, dB_rated, p_atm, UnitConversions.convert(1, 'ton', 'kBtu/hr'), cool_nominal_cfm_per_ton, cooling_system.cooling_shr, win)
-
+
+      clg_ap.a_o = ao
       clg_ap.cool_rated_shrs_gross = []
       clg_ap.cool_capacity_ratios.each_with_index do |capacity_ratio, i|
         # Calculate the SHR for each speed. Use minimum value of 0.98 to prevent E+ bypass factor calculation errors

HPXMLtoOpenStudio/resources/hvac_sizing.rb

@@ -33,8 +33,8 @@ def self.calculate(runner, weather, hpxml_bldg, hvac_systems, update_hpxml: true
     end
 
     # Assign initial loads for each HVAC system (before duct loads)
-    all_hvac_loads = {}
-    hvac_systems.each do |hvac_system|
+    all_hvac_loads = {} #assign hvac_sizing_values to empty hash
+    hvac_systems.each do |hvac_system| #loop thru each hvac_system object
       hvac_heating, hvac_cooling = hvac_system[:heating], hvac_system[:cooling]
       zone = hvac_heating.nil? ? hvac_cooling.zone : hvac_heating.zone
       next if is_system_to_skip(hvac_heating, hvac_cooling, zone)
@@ -1689,6 +1689,7 @@ def self.apply_hvac_duct_loads_cooling(mj, zone, hvac_loads, zone_loads, all_spa
   def self.apply_hvac_equipment_adjustments(mj, runner, hvac_sizings, weather, hvac_heating, hvac_cooling, hvac_system, hpxml_bldg)
     '''
     Equipment Adjustments
+    This is where the bulk of ACCA Man. S is applied
     '''
 
     # Cooling
@@ -1716,8 +1717,16 @@ def self.apply_hvac_equipment_adjustments(mj, runner, hvac_sizings, weather, hva
       # such as different indoor/outdoor coil combinations and different blower settings.
       # Ductless systems don't offer this flexibility.
 
+      #per E+ docs, capacity and SHR inputs should be “gross” values
+
       entering_temp = hpxml_bldg.header.manualj_cooling_design_temp
       hvac_cooling_speed = get_sizing_speed(hvac_cooling_ap, true)
+        #ADP/BF specified for Coil:Cooling:DX:SingleSpeed, but should be implemented for all coils
+        #rated total capacity and rated SHR are used to calculate coil bypass factor constant A_o at rated conditions
+        #this is already done in hvac.rb and stored in the hvac_cooling_ap object
+        #once A_o is determined, the BF at design conditions can be calculated and used to determine the design SHR
+        #last step is to calculate sensible capacity at design conditions using design_shr   
+
       if hvac_cooling.compressor_type == HPXML::HVACCompressorTypeVariableSpeed
         idb_adj = adjust_indoor_condition_var_speed(entering_temp, mj.cool_indoor_wetbulb, :clg)
         odb_adj = adjust_outdoor_condition_var_speed(hvac_cooling.cooling_detailed_performance_data, entering_temp, hvac_cooling, :clg)
@@ -1729,21 +1738,35 @@ def self.apply_hvac_equipment_adjustments(mj, runner, hvac_sizings, weather, hva
 
       cool_cap_rated = hvac_sizings.Cool_Load_Tot / total_cap_curve_value
 
-      hvac_cooling_shr = hvac_cooling_ap.cool_rated_shrs_gross[hvac_cooling_speed]
+      hvac_cooling_shr = hvac_cooling_ap.cool_rated_shrs_gross[hvac_cooling_speed] #same as net shr per comments in hvac.rb, see set_cool_rated_shrs_gross for details
       sens_cap_rated = cool_cap_rated * hvac_cooling_shr
 
       # Calculate the air flow rate required for design conditions
       hvac_sizings.Cool_Airflow = calc_airflow_rate_manual_s(mj, hvac_sizings.Cool_Load_Sens, (mj.cool_setpoint - leaving_air_temp), cool_cap_rated)
+      #units of Cool_Airflow are cfm
+      #calculate rated coil bypass factor HERE, then use rated BF --> design BF --> design SHR --> design sensible capacity
+
+      cool_airflow_rated = UnitConversions.convert(cool_cap_rated, 'Btu/hr', 'ton')*hvac_cooling.additional_properties.cool_rated_cfm_per_ton[-1] #rated cfm, check whether cfm/ton is net or gross?
+      #following Calculate max rated cfm section in hvac.rb, which sets rated airflow to the product of detailed performance capacity and the last (highest speed?) element of cool_rated_cfm_per_ton array
+      #for base.xml, cool_airflow_rated = 705.6 cfm and hvac_sizings.Cool_Airflow = 715.96 cfm
+      #assuming hvac_sizings.Cool_Airflow is the design airflow rate, inferred from comments in calc_airflow_rate_manual_s
+      #note: using MJ cooling setpoint as EDB in Psychrometrics.calculateSHR() ignores return duct losses
 
-      sensible_cap_curve_value = process_curve_fit(hvac_sizings.Cool_Airflow, hvac_sizings.Cool_Load_Tot, entering_temp)
-      sens_cap_design = sens_cap_rated * sensible_cap_curve_value
-      lat_cap_design = [hvac_sizings.Cool_Load_Tot - sens_cap_design, 1.0].max
+      hr_indoor_cooling_local = calculate_indoor_hr(hpxml_bldg.header.manualj_humidity_setpoint, mj.cool_setpoint, mj.p_atm)
+      #hr_indoor_cooling is calculated above in the script, but is calculated after the method call of apply_hvac_equipment_adjustments. Therefore, it needs to calculated from MJ objects locally in apply_hvac_equipment_adjustments for use in CalculateSHR(). 
+
+      hvac_cooling_ap.rated_shr = Psychrometrics.CalculateSHR(runner, mj.cool_setpoint, UnitConversions.convert(mj.p_atm, 'atm', 'psi'), UnitConversions.convert(cool_cap_rated, 'btu/hr', 'kbtu/hr'), hvac_sizings.Cool_Airflow, hvac_cooling_ap.a_o, hr_indoor_cooling_local)
+      #Calculate the coil SHR at the given incoming air state, CFM, total capacity, and coil Ao factor
+      #coil Ao needs to be in SI units, currently 0.38 for base.xml --> check if unit conversion is necessary?
+      puts(hvac_cooling_shr)
+      puts(hvac_cooling_ap.rated_shr)
+
+      sens_cap_design = cool_cap_design*hvac_cooling_shr_design
+
+      lat_cap_design = [hvac_sizing_values.Cool_Load_Tot - sens_cap_design, 1.0].max
+
+
 
-      shr_biquadratic = get_shr_biquadratic
-      a_sens = shr_biquadratic[0]
-      b_sens = shr_biquadratic[1]
-      c_sens = shr_biquadratic[3]
-      d_sens = shr_biquadratic[5]
 
       # Adjust Sizing
       if hvac_cooling.is_a?(HPXML::HeatPump) && (hpxml_bldg.header.heat_pump_sizing_methodology == HPXML::HeatPumpSizingHERS)
@@ -2876,10 +2899,12 @@ def self.process_curve_fit(airflow_rate, capacity, temp)
 
   def self.get_shr_biquadratic
     # Based on EnergyPlus's model for calculating SHR at off-rated conditions. This curve fit
-    # avoids the iterations in the actual model. It does not account for altitude or variations
+    # avoids the iterations in the actual model. The ADP/BF method incorporates these iterations. It does not account for altitude or variations
     # in the SHRRated. It is a function of ODB (MJ design temp) and CFM/Ton (from MJ)
     return [1.08464364, 0.002096954, 0, -0.005766327, 0, -0.000011147]
   end
+  #get_shr_biquadratic will be replaced with ADP/BF method for calculating SHR at off-rated conditions
+
 
   def self.get_sizing_speed(hvac_ap, is_cooling)
     if is_cooling && hvac_ap.respond_to?(:cool_capacity_ratios)

HPXMLtoOpenStudio/resources/pseudo_code_heat_pump_sizing.txt

@@ -0,0 +1,14 @@
+#Pseudo-Code for Heat Pump Sizing Condition
+def assign_hvac_sizing_condition(mj, system_design_loads, hvac_heating, hvac_cooling)
+Assign HVAC sizing condition "String Classification" that takes in system design loads from MJ
+Step 1: produce MJ load calc (already done)
+Step 2: follow equipment selection and sizing procedure flowchart
+	- if system is heat pump, determine HP sizing condition
+	- else, either clg only, furnace, or boiler yes/no checks
+Step 3: procure OEM performance data
+	- is forced air system?
+	- water-air system?
+	- ACF required? (altitude above 2,500 ft)
+	- extract capacity from OEM performance data, interpolate if necessary
+	- determine blower CFM
+Step 4: apply sizing requirements (normative section N2)

HPXMLtoOpenStudio/resources/psychrometrics.rb

@@ -395,7 +395,7 @@ def self.CoilAoFactor(runner, dBin, p, qdot, cfm, shr, win)
     '''
     Description:
     ------------
-        Find the coil Ao factor at the given incoming air state (entering drybubl and wetbulb) and CFM,
+        Find the coil Ao factor at the given incoming air state (entering drybulb and wetbulb) and CFM,
         total capacity and SHR
 
 
@@ -428,7 +428,7 @@ def self.CoilBypassFactor(runner, dBin, p, qdot, cfm, shr, win)
     '''
     Description:
     ------------
-        Find the coil bypass factor at the given incoming air state (entering drybubl and wetbulb) and CFM,
+        Find the coil bypass factor at the given incoming air state (entering drybulb and wetbulb) and CFM,
         total capacity and SHR
 
 
@@ -514,7 +514,7 @@ def self.CalculateMassflowRate(dBin, p, cfm, win)
     '''
     Description:
     ------------
-        Calculate the mass flow rate at the given incoming air state (entering drybubl and wetbulb) and CFM
+        Calculate the mass flow rate at the given incoming air state (entering drybul and wetbulb) and CFM
 
     Source:
     -------