Fix ASHRAE simple method for vertical surfaces

src/EnergyPlus/ConvectionCoefficients.cc

@@ -49,7 +49,6 @@
 #include <algorithm>
 #include <cassert>
 #include <cmath>
-#include <limits>
 #include <string>
 
 // ObjexxFCL Headers
@@ -3831,62 +3830,70 @@ namespace ConvectionCoefficients {
         //     NBSSIR 83-2655, National Bureau of Standards, "Surface Inside Heat Balances", pp 79.
         // 2.  ASHRAE Handbook of Fundamentals 1985, p. 23.2, Table 1.
 
-        // USE STATEMENTS:
-        // na
-
-        // Locals
-        // SUBROUTINE ARGUMENT DEFINITIONS:
-
-        // SUBROUTINE PARAMETER DEFINITIONS:
-        // na
 
-        // INTERFACE BLOCK SPECIFICATIONS:
-        // na
-
-        // DERIVED TYPE DEFINITIONS:
-        // na
+        //      +---------------------+-----------+---------------------------------------------+------------------+-----------------+-------------+
+        //      |      Situation      | DeltaTemp |                   CosTilt                   | cos(tilt)*deltaT | Convection Type | Coefficient |
+        //      +---------------------+-----------+---------------------------------------------+------------------+-----------------+-------------+
+        //      | Vertical Surface    | N/A       | -0.3827 to 0.3827 (67.5 to 112.5 degrees)   | N/A              | Normal          |       3.076 |
+        //      | Horizontal Surface  | Positive  | 0.9238 to 1.0 (0 to 22.5 degrees)           | Positive         | Enhanced        |       4.043 |
+        //      | Horizontal Surface  | Positive  | -0.9238 to -1.0 (157.5 to 180 degrees)      | Negative         | Reduced         |       0.948 |
+        //      | Horizontal Surface  | Negative  | 0.9239 to 1.0 (0 to 22.5 degrees)           | Negative         | Reduced         |       0.948 |
+        //      | Horizontal Surface  | Negative  | -0.9239 to -1.0 (157.5 to 180 degrees)      | Positive         | Enhanced        |       4.040 |
+        //      | Tilted Surface      | Positive  | 0.3827 to 0.9239 (22.5 to 67.5 degrees)     | Positive         | Enhanced        |       3.870 |
+        //      | Tilted Surface      | Negative  | -0.3827 to -0.9239 (157.5 to 157.5 degrees) | Positive         | Enhanced        |       3.870 |
+        //      | Tilted Surface      | Negative  | 0.3827 to 0.9239 (22.5 to 67.5 degrees)     | Negative         | Reduced         |       2.281 |
+        //      | Tilted Surface      | Positive  | -0.3827 to -0.9239 (157.5 to 157.5 degrees) | Negative         | Reduced         |       2.281 |
+        //      +---------------------+-----------+---------------------------------------------+------------------+-----------------+-------------+
 
-        // SUBROUTINE LOCAL VARIABLE DECLARATIONS:
-        Real64 DeltaTemp = Tamb - Tsurf;
 
         // Set HConvIn using the proper correlation based on DeltaTemp and Cosine of the Tilt of the Surface
-        if (std::abs(cosTilt) >= 0.9239) {   // Horizontal Surface
-            if (DeltaTemp * cosTilt < 0.0) { // Horizontal, Reduced Convection
-                return 0.948;
-            } else if (DeltaTemp * cosTilt == 0.0) { // Vertical Surface
-                return 3.076;
-            } else /*if (DeltaTemp * cosTilt > 0.0)*/ { // Horizontal, Enhanced Convection
-                return 4.040;
-            }
-        } else {                             // Tilted Surface
-            if (DeltaTemp * cosTilt < 0.0) { // Tilted, Reduced Convection
-                return 2.281;
-            } else if (DeltaTemp * cosTilt == 0.0) { // Vertical Surface
-                return 3.076;
-            } else /*if (DeltaTemp * cosTilt > 0.0)*/ { // Tilted, Enhanced Convection
-                return 3.870;
+        if (std::abs(cosTilt) < 0.3827) {  // Vertical Surface
+            return 3.076;
+        }
+        else {
+            Real64 DeltaTempCosTilt = (Tamb - Tsurf)*cosTilt;
+            if (std::abs(cosTilt) >= 0.9239) { // Horizontal Surface
+                if (DeltaTempCosTilt > 0.0){ //Enhanced Convection
+                    return 4.040;
+                }
+                else if (DeltaTempCosTilt < 0.0){ // Reduced Convection
+                    return 0.948;
+                }
+                else { // Zero DeltaTemp
+                    return 3.076;
+                }
+            }
+            else { // tilted surface
+                if (DeltaTempCosTilt > 0.0){ // Enhanced Convection
+                    return 3.870;
+                }
+                else if (DeltaTempCosTilt < 0.0){ // Reduced Convection
+                    return 2.281;
+                }
+                else { // Zero DeltaTemp
+                    return 3.076;
+                }
             }
         }
+
     }
 
     void CalcASHRAESimpleIntConvCoeff(int const SurfNum,                  // surface number for which coefficients are being calculated
                                       Real64 const SurfaceTemperature,    // Temperature of surface for evaluation of HcIn
                                       Real64 const ZoneMeanAirTemperature // Mean Air Temperature of Zone
     )
     {
-
-        if (std::abs(Surface(SurfNum).CosTilt) >= 0.3827) { // Recalculate HConvIn
-            if (Surface(SurfNum).ExtBoundCond == DataSurfaces::KivaFoundation) {
-                SurfaceGeometry::kivaManager.surfaceConvMap[SurfNum].in = [](double Tsurf, double Tamb, double, double, double cosTilt) -> double {
-                    return CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, cosTilt);
-                };
-            } else {
-                HConvIn(SurfNum) = CalcASHRAESimpleIntConvCoeff(SurfaceTemperature, ZoneMeanAirTemperature, Surface(SurfNum).CosTilt);
-            }
+        if (Surface(SurfNum).ExtBoundCond == DataSurfaces::KivaFoundation){
+            SurfaceGeometry::kivaManager.surfaceConvMap[SurfNum].in = [](double Tsurf, double Tamb, double, double, double cosTilt) -> double {
+              return CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, cosTilt);
+            };
+        }
+        else {
+            HConvIn(SurfNum) = CalcASHRAESimpleIntConvCoeff(SurfaceTemperature, ZoneMeanAirTemperature, Surface(SurfNum).CosTilt);
         }
 
         // Establish some lower limit to avoid a zero convection coefficient (and potential divide by zero problems)
-        if (HConvIn(SurfNum) < LowHConvLimit) HConvIn(SurfNum) = LowHConvLimit;
+        HConvIn(SurfNum) = max(HConvIn(SurfNum), LowHConvLimit);
     }
 
     Real64 CalcASHRAETARPNatural(Real64 const Tsurf, Real64 const Tamb, Real64 const cosTilt)

tst/EnergyPlus/unit/ConvectionCoefficients.unit.cc

@@ -1242,3 +1242,139 @@ TEST_F(ConvectionCoefficientsFixture, CalcBeausoleilMorrisonMixedUnstableCeiling
     convCoeff = CalcBeausoleilMorrisonMixedUnstableCeiling(deltaTemp, height, surfTemp, zoneNum);
     EXPECT_NEAR(convCoeff, 9.999, tolerance);
 }
+
+
+TEST_F(ConvectionCoefficientsFixture, ConvectionCoefficientsTest_CalcASHRAESimpleIntConvCoeff)
+{
+    // Unit test for the function CalcASHRAESimpleIntConvCoeff, used to determine the Convection Coefficient
+    // for the Ashrae Simple algorithm setting
+
+    Real64 Tsurf;
+    Real64 Tamb;
+    Real64 CosTilt;
+    Real64 ConvectionCoefficient;
+    Real64 ExpectedCoefficient;
+
+    // Scenario: Vertical Surface
+    // Hcov expected = 3.076
+    // Delta_T is not relevant for this calculation
+
+    Tsurf = 30.0;
+    Tamb = 20.0;
+    CosTilt = 0.0; // cos(90 degrees)
+    ExpectedCoefficient = 3.076;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+    //Scenario: Vertical Surface, CosTilt not exactly zero
+    // Hcov expected = 3.076
+
+    Tsurf = 19.0;
+    Tamb = 20.0;
+    CosTilt = 0.0001; // cos(90 degrees)
+    ExpectedCoefficient = 3.076;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+    //Scenario: Vertical Surface, Zero Delta T
+    // Hcov expected = 3.076
+
+    Tsurf = 23.0;
+    Tamb = 23.0;
+    CosTilt = 0; // cos(90 degrees)
+    ExpectedCoefficient = 3.076;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+    // Scenario: Horizontal Surface with reduced convection
+    // Hcov expected = 0.948
+    // A negative Delta_T is required for reduced convection
+
+    Tsurf = 30.0;
+    Tamb = 20.0;
+    CosTilt = 0.9239; // cos(22.5 degrees)
+    ExpectedCoefficient = 0.948;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+
+    //Scenario: Horizontal surface with enhanced convection:
+    // Hcov expected = 4.040
+    // A positive Delta_T is required for enhanced convection
+
+    Tsurf = 20.0;
+    Tamb = 30.0;
+    CosTilt = 0.9239; // cos(22.5 degrees)
+    ExpectedCoefficient = 4.040;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+    //Scenario: horizontal surface, enhanced convection
+    // 180 degree surface, negative Delta_T
+    // Hcov expected = 4.040
+
+    Tsurf = 30.0;
+    Tamb = 20.0;
+    CosTilt = -1; // cos(180 degrees)
+    ExpectedCoefficient = 4.040;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+    //Scenario: horizontal surface, reduced convection
+    // 180 degree surface, positive Delta_T
+    // Hcov expected = 0.948
+
+    Tsurf = 20.0;
+    Tamb = 30.0;
+    CosTilt = -1; // cos(180 degrees)
+    ExpectedCoefficient = 0.948;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+    //Scenario: tilted surface with reduced convection
+    // Hcov expected = 2.281
+    // A negative Delta_T is required for reduced convection
+
+    Tsurf = 30.0;
+    Tamb = 20.0;
+    CosTilt = 0.707; // cos(45 degrees)
+    ExpectedCoefficient = 2.281;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+
+    //Scenario: tilted surface with enhanced convection
+    // Hcov expected = 3.870
+
+    Tsurf = 20.0;
+    Tamb = 30.0;
+    CosTilt = 0.707; // cos(45 degrees)
+    ExpectedCoefficient = 3.870;
+
+    ConvectionCoefficient = CalcASHRAESimpleIntConvCoeff(Tsurf, Tamb, CosTilt);
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+}
+
+TEST_F(ConvectionCoefficientsFixture, ConvectionCoefficientsTest_HConvInDependence)
+{
+    Real64 ConvectionCoefficient;
+    Real64 ExpectedCoefficient = 3.076;
+
+    DataSurfaces::Surface.allocate(1);
+    DataSurfaces::Surface(1).CosTilt = 0;
+
+    DataHeatBalance::HConvIn.allocate(1);
+
+    CalcASHRAESimpleIntConvCoeff(1, 20.0, 30.0);
+
+    ConvectionCoefficient = DataHeatBalance::HConvIn(1);
+
+    EXPECT_EQ(ConvectionCoefficient, ExpectedCoefficient);
+}