Extended HI followup: fix speed issue

doc/engineering-reference/src/special-modules-reporting/resilience-metrics.tex

@@ -66,69 +66,17 @@ \subsubsection{Heat Index}\label{heat-index}
 \end{tabular}
 \end{table}
 
-The computation of the heat index is a refinement of a result obtained by
+Before version 24.2, the computation of the heat index is a refinement of a result obtained by
 multiple regression analysis carried out by Lans P. Rothfusz and described in a
-1990 National Weather Service (NWS) Technical Attachment (SR 90-23) [4-5]. The
-calculation is based on degree Fahrenheit.
+1990 National Weather Service (NWS) Technical Attachment (SR 90-23) [4-5].
 
-The regression equation of Rothfusz is
-\begin{equation}  \label{eq:rm-1}
-HI = c_1 + c_2T + c_3R + c_4TR + c_5T^2 + c_6R^2 + c_7T^2R + c_8TR^2 + c_9T^2R^2
-\end{equation}
-
-where
-
-HI = heat index (expressed as an apparent temperature in degrees Fahrenheit),
-
-T = ambient dry-bulb temperature (in degrees Fahrenheit),
-
-R = relative humidity (percentage value between 0 and 100),
-
-$c_1$ = -42.379,
-
-$c_2$ = 2.04901523,
-
-$c_3$ = 10.14333127,
-
-$c_4$ = -0.22475541,
-
-$c_5$ = -0.00683783,
-
-$c_6$ = -0.05481717,
-
-$c_7$ = 0.00122874,
-
-$c_8$ = 0.00085282,
-
-$c_9$ = -0.00000199.
-
-If the RH is less than 13\% and the temperature is between 80 and \IP{112}{\fahrenheit}, then
-the following adjustment is subtracted from HI:
-
-\begin{equation}  \label{eq:rm-2}
-HI = (13 - R) / 4 * ((17 - |T - 95|) / 17)^{0.5}
-\end{equation}
-
-Otherwise, if the RH is greater than 85\% and the temperature is between 80 and
-\IP{87}{\fahrenheit}, then the following adjustment is added to HI:
-
-\begin{equation}  \label{eq:rm-3}
-HI = (R - 85) / 10 * (87 - T) / 5
-\end{equation}
-
-The Rothfusz regression is not appropriate when conditions of temperature and
-humidity warrant a heat index value below about \IP{80}{\fahrenheit}. In those cases, a simpler
-formula is applied to calculate values consistent with Steadman's results:
-
-\begin{equation}  \label{eq:rm-4}
-HI = 0.5 * (T + 61.0 + (T - 68.0) * 1.2 + (R * 0.094))
-\end{equation}
-
-In practice, the simple formula is computed first based on the temperature and
-humidity. If this heat index value is \IP{80}{\fahrenheit} or higher, the full regression
-equation along with any adjustment as described above is applied. The Rothfusz
-regression is not valid for extreme temperature and relative humidity conditions
-beyond the range of data considered by Steadman.
+Starting from version 24.2, the heat index calculation adopts the extended heat
+index method developed by Lu \& Romps [17]. The previous heat index gives
+unrealistic results for very hot and humid or very cold and dry conditions. The
+extended index extends the domain of the heat index calculation to all
+combinations of temperature and relative humidity and gives a more realistic heat
+index for the extreme conditions. The implementation in EnergyPlus is based on
+the released Python code by Lu and Romps [18].
 
 The Heat Index Hours (accumulated hours for a space) and Heat Index
 OccupantHours (accumulated hours for the sum of all occupants in a space) of
@@ -516,3 +464,11 @@ \subsection{References}
 
 {[}16{]} ACGIH, Threshold Limit Values (TLVs) and Biological Exposure Indices
 (BEIs), 2012. doi:10.1073/pnas.0703993104.
+
+{[}17{]} Lu, Yi-Chuan, and David M. Romps. ``Extending the heat index''. Journal
+of Applied Meteorology and Climatology 61, no. 10 (2022): 1367-1383.
+doi:10.1073/pnas.0703993104.
+
+{[}18{]} Lu, Yi-Chuan, and David M. Romps. ``Lu and Romps, Extending the heat index, JAMC, 2022'',
+Physics of Climate, February 23, 2023.
+https://romps.berkeley.edu/papers/pubs-2020-heatindex.html.

idd/Energy+.idd.in

@@ -977,6 +977,17 @@ HVACSystemRootFindingAlgorithm,
        \type integer
        \default 5
 
+HeatIndexAlgorithm,
+       \memo Specify whether the simplified or the extended method should be used
+       \memo Simplified: based on regression analysis carried out by Lans P. Rothfusz
+       \memo Extended: Based on paper by Lu & Romps
+       \unique-object
+  A1 ; \field Algorithm
+       \type choice
+       \key Simplified
+       \key Extended
+       \default Simplified
+
 \group Compliance Objects
 
 Compliance:Building,

src/EnergyPlus/CMakeLists.txt

@@ -262,6 +262,8 @@ set(SRC
     EvaporativeFluidCoolers.hh
     ExhaustAirSystemManager.cc
     ExhaustAirSystemManager.hh
+    ExtendedHI.cc
+    ExtendedHI.hh
     ExteriorEnergyUse.cc
     ExteriorEnergyUse.hh
     ExternalInterface.cc

src/EnergyPlus/DataHeatBalance.hh

@@ -547,6 +547,19 @@ namespace DataHeatBalance {
         {
         }
     };
+
+    enum class HeatIndexMethod : int
+    {
+        Invalid = -1,
+        Simplified,
+        Extended,
+        Num
+    };
+    static constexpr std::array<std::string_view, static_cast<int>(HeatIndexMethod::Num)> HeatIndexMethodUC = {
+        "SIMPLIFIED",
+        "EXTENDED",
+    };
+
     struct ZoneData : ZoneSpaceData
     {
         // Members
@@ -1847,6 +1860,7 @@ struct HeatBalanceData : BaseGlobalStruct
     bool NoRegularMaterialsUsed = true;
     bool DoLatentSizing = false; // true when latent sizing is performed during zone sizing
     bool isAnyLatentLoad = false;
+    DataHeatBalance::HeatIndexMethod heatIndexMethod = DataHeatBalance::HeatIndexMethod::Simplified;
 
     Array1D<Real64> ZoneListSNLoadHeatEnergy;
     Array1D<Real64> ZoneListSNLoadCoolEnergy;