Update Qinf=f(NL) equation.

NREL · Dec 18, 2023 · 85b4086 · 85b4086
1 parent bddcef9
commit 85b4086
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Showing 2 changed files with 10 additions and 5 deletions.
diff --git a/HPXMLtoOpenStudio/resources/airflow.rb b/HPXMLtoOpenStudio/resources/airflow.rb
@@ -219,7 +219,7 @@ def self.get_default_mech_vent_flow_rate(hpxml_bldg, vent_fan, weather, cfa, nbe
     sla, _ach50, _nach, _volume, height, a_ext = get_values_from_air_infiltration_measurements(hpxml_bldg, cfa, weather)
 
     nl = get_infiltration_NL_from_SLA(sla, height)
-    q_inf = nl * weather.data.WSF * cfa / 7.3 # Effective annual average infiltration rate, cfm, eq. 4.5a
+    q_inf = get_infiltration_Qinf_from_NL(nl, weather, cfa)
 
     q_tot = get_mech_vent_qtot_cfm(nbeds, cfa)
 
@@ -2012,6 +2012,11 @@ def self.get_infiltration_ACH50_from_SLA(sla, n_i, floor_area, volume)
     # Returns the infiltration ACH50 given a SLA.
     return ((sla * floor_area * UnitConversions.convert(1.0, 'ft^2', 'in^2') * 50.0**n_i * 60.0) / (0.283316478 * 4.0**n_i * volume))
   end
+
+  def self.get_infiltration_Qinf_from_NL(nl, weather, cfa)
+    # Returns the effective annual average infiltration rate in cfm
+    return nl * weather.data.WSF * cfa * 8.202 / 60.0
+  end
 
   def self.calc_duct_leakage_at_diff_pressure(q_old, p_old, p_new)
     return q_old * (p_new / p_old)**0.6 # Derived from Equation C-1 (Annex C), p34, ASHRAE Standard 152-2004.

diff --git a/HPXMLtoOpenStudio/tests/test_defaults.rb b/HPXMLtoOpenStudio/tests/test_defaults.rb
@@ -2303,7 +2303,7 @@ def test_mech_ventilation_fans
     hpxml_bldg.air_infiltration_measurements[0].infiltration_type = HPXML::InfiltrationTypeUnitExterior
     XMLHelper.write_file(hpxml.to_doc, @tmp_hpxml_path)
     _default_hpxml, default_hpxml_bldg = _test_measure()
-    _test_default_mech_vent_values(default_hpxml_bldg, false, 24.0, 27.2, 77.3)
+    _test_default_mech_vent_values(default_hpxml_bldg, false, 24.0, 27.1, 77.3)
 
     # Test defaults w/ MF building, compartmentalization test
     hpxml, hpxml_bldg = _create_hpxml('base-bldgtype-mf-unit.xml')
@@ -2328,7 +2328,7 @@ def test_mech_ventilation_fans
                                     used_for_whole_building_ventilation: true)
     XMLHelper.write_file(hpxml.to_doc, @tmp_hpxml_path)
     _default_hpxml, default_hpxml_bldg = _test_measure()
-    _test_default_mech_vent_values(default_hpxml_bldg, false, 24.0, 21.6, 61.7)
+    _test_default_mech_vent_values(default_hpxml_bldg, false, 24.0, 21.7, 61.9)
 
     # Test defaults w/ CFM50 infiltration
     hpxml, hpxml_bldg = _create_hpxml('base-enclosure-infil-cfm50.xml')
@@ -2355,7 +2355,7 @@ def test_mech_ventilation_fans
                                     used_for_whole_building_ventilation: true)
     XMLHelper.write_file(hpxml.to_doc, @tmp_hpxml_path)
     _default_hpxml, default_hpxml_bldg = _test_measure()
-    _test_default_mech_vent_values(default_hpxml_bldg, false, 24.0, 27.0, 77.1)
+    _test_default_mech_vent_values(default_hpxml_bldg, false, 24.0, 27.0, 77.2)
 
     # Test inputs not overridden by defaults w/ CFIS
     hpxml, hpxml_bldg = _create_hpxml('base-mechvent-cfis.xml')
@@ -2396,7 +2396,7 @@ def test_mech_ventilation_fans
     vent_fan.cfis_addtl_runtime_operating_mode = nil
     XMLHelper.write_file(hpxml.to_doc, @tmp_hpxml_path)
     _default_hpxml, default_hpxml_bldg = _test_measure()
-    _test_default_mech_vent_values(default_hpxml_bldg, false, 8.0, 149.4, 298.7, 1.0, HPXML::CFISModeAirHandler)
+    _test_default_mech_vent_values(default_hpxml_bldg, false, 8.0, 149.4, 298.8, 1.0, HPXML::CFISModeAirHandler)
 
     # Test inputs not overridden by defaults w/ ERV
     hpxml, hpxml_bldg = _create_hpxml('base-mechvent-erv.xml')