Update utils/heat_transfer.py

utils/heat_transfer.py

@@ -2,6 +2,7 @@
 Heat transfer calculation module for HVAC Load Calculator.
 This module provides enhanced calculations for conduction, convection, radiation,
 infiltration, and solar geometry, with improved modularity and error handling.
+Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Sections 18.3-18.4.
 """
 
 from typing import Optional, Tuple
@@ -106,7 +107,7 @@ class SolarCalculations:
         """
         self.validate_angle(latitude, "Latitude", -90, 90)
         self.validate_angle(declination, "Declination", -90, 90)
-        self.validate_angle(hour_angle, "Hour angle", -180, 180)
+        self.validate_angle(hour_angle, "Hour angle", -180ublisher: https://www.w3schools.com/howto/tryit.asp?filename=trycss_form_checkbox
         self.validate_angle(altitude, "Altitude", 0, 90)
         
         lat_rad = math.radians(latitude)
@@ -236,6 +237,7 @@ class HeatTransferCalculations:
     def conduction_heat_transfer(self, u_value: float, area: float, delta_t: float) -> float:
         """
         Calculate heat transfer by conduction.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Equation 18.1.
         
         Args:
             u_value: Overall heat transfer coefficient in W/(m²·K)
@@ -253,6 +255,7 @@ class HeatTransferCalculations:
     def convection_heat_transfer(self, h: float, area: float, delta_t: float) -> float:
         """
         Calculate heat transfer by convection.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Section 18.3.
         
         Args:
             h: Convective heat transfer coefficient in W/(m²·K)
@@ -270,6 +273,7 @@ class HeatTransferCalculations:
     def radiation_heat_transfer(self, emissivity: float, area: float, t_surface: float, t_surroundings: float) -> float:
         """
         Calculate heat transfer by radiation using Stefan-Boltzmann law.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Section 18.3.
         
         Args:
             emissivity: Surface emissivity (0-1)
@@ -293,6 +297,7 @@ class HeatTransferCalculations:
     def thermal_lag_factor(self, thermal_mass: float, time_constant: float, time_step: float) -> float:
         """
         Calculate thermal lag factor for transient heat transfer.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Section 18.5.
         
         Args:
             thermal_mass: Thermal mass in J/K
@@ -311,41 +316,52 @@ class HeatTransferCalculations:
         
         return math.exp(-time_step / time_constant)
     
-    def infiltration_heat_transfer(self, flow_rate: float, delta_t: float) -> float:
+    def infiltration_heat_transfer(self, flow_rate: float, delta_t: float, t_db: float, rh: float, p_atm: float = 101325) -> float:
         """
         Calculate sensible heat transfer due to infiltration or ventilation.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Equation 18.5.
         
         Args:
             flow_rate: Air flow rate in m³/s
             delta_t: Temperature difference in °C
+            t_db: Dry-bulb temperature in °C (for air properties)
+            rh: Relative humidity in % (for air properties)
+            p_atm: Atmospheric pressure in Pa (default: 101325 Pa)
             
         Returns:
             Sensible heat transfer rate in W
         """
         self.validate_inputs(delta_t, flow_rate=flow_rate)
-        rho = 1.2  # Air density in kg/m³
-        cp = 1005  # Specific heat of air in J/(kg·K)
-        return flow_rate * rho * cp * delta_t
+        w = self.psychrometrics.humidity_ratio(t_db, rh, p_atm)
+        rho = self.psychrometrics.density(t_db, w, p_atm)
+        c_p = 1006 + w * 1860  # Specific heat of moist air in J/(kg·K)
+        return flow_rate * rho * c_p * delta_t
     
-    def infiltration_latent_heat_transfer(self, flow_rate: float, delta_w: float) -> float:
+    def infiltration_latent_heat_transfer(self, flow_rate: float, delta_w: float, t_db: float, rh: float, p_atm: float = 101325) -> float:
         """
         Calculate latent heat transfer due to infiltration or ventilation.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Equation 18.6.
         
         Args:
             flow_rate: Air flow rate in m³/s
             delta_w: Humidity ratio difference in kg/kg
+            t_db: Dry-bulb temperature in °C (for air properties)
+            rh: Relative humidity in % (for air properties)
+            p_atm: Atmospheric pressure in Pa (default: 101325 Pa)
             
         Returns:
             Latent heat transfer rate in W
         """
-        self.validate_inputs(0, flow_rate=flow_rate)
-        rho = 1.2  # Air density in kg/m³
-        h_fg = 2501000  # Latent heat of vaporization in J/kg
+        self.validate_inputs(t_db, flow_rate=flow_rate)
+        w = self.psychrometrics.humidity_ratio(t_db, rh, p_atm)
+        rho = self.psychrometrics.density(t_db, w, p_atm)
+        h_fg = 2501000 + 1840 * t_db  # Latent heat of vaporization in J/kg
         return flow_rate * rho * h_fg * delta_w
     
     def wind_pressure_difference(self, wind_speed: float, wind_coefficient: float = 0.4) -> float:
         """
         Calculate pressure difference due to wind.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 16, Section 16.3.
         
         Args:
             wind_speed: Wind speed in m/s
@@ -359,12 +375,13 @@ class HeatTransferCalculations:
         if not 0 <= wind_coefficient <= 1:
             raise ValueError(f"Wind coefficient {wind_coefficient} must be between 0 and 1")
         
-        rho = 1.2  # Air density in kg/m³
+        rho = 1.2  # Air density in kg/m³ (simplified for wind calculations)
         return 0.5 * wind_coefficient * rho * wind_speed**2
     
     def stack_pressure_difference(self, height: float, indoor_temp: float, outdoor_temp: float) -> float:
         """
         Calculate pressure difference due to stack effect.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 16, Section 16.3.
         
         Args:
             height: Height difference in m
@@ -380,7 +397,7 @@ class HeatTransferCalculations:
             raise ValueError("Temperatures must be positive in Kelvin")
         
         g = 9.81  # Gravitational acceleration in m/s²
-        rho = 1.2  # Air density in kg/m³
+        rho = 1.2  # Air density in kg/m³ (simplified for stack calculations)
         delta_t = abs(indoor_temp - outdoor_temp)
         t_avg = (indoor_temp + outdoor_temp) / 2
         return rho * g * height * delta_t / t_avg
@@ -388,6 +405,7 @@ class HeatTransferCalculations:
     def combined_pressure_difference(self, wind_pd: float, stack_pd: float) -> float:
         """
         Calculate combined pressure difference from wind and stack effects.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 16, Section 16.3.
         
         Args:
             wind_pd: Wind pressure difference in Pa
@@ -404,6 +422,7 @@ class HeatTransferCalculations:
                                 pressure_difference: float) -> float:
         """
         Calculate infiltration flow rate using crack method.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 16, Section 16.4.
         
         Args:
             crack_length: Total crack length in m
@@ -427,6 +446,7 @@ class HeatTransferCalculations:
                            surface_absorptivity: float, surface_resistance: float) -> float:
         """
         Calculate sol-air temperature for a surface.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Section 18.4.
         
         Args:
             outdoor_temp: Outdoor air temperature in °C
@@ -453,6 +473,7 @@ class HeatTransferCalculations:
                        shading_coefficient: float = 1.0) -> float:
         """
         Calculate solar heat gain through a surface.
+        Reference: ASHRAE Handbook—Fundamentals (2017), Chapter 18, Section 18.4.
         
         Args:
             irradiance: Solar irradiance on surface in W/m²
@@ -498,11 +519,16 @@ if __name__ == "__main__":
     u_value = 0.5  # W/(m²·K)
     area = 20.0  # m²
     delta_t = 10.0  # °C
+    t_db = 25.0  # °C
+    rh = 50.0  # %
     conduction = heat_transfer_calculator.conduction_heat_transfer(u_value, area, delta_t)
     print(f"Conduction Heat Transfer: {conduction:.2f} W")
     
+    # Example infiltration calculation
+    flow_rate = 0.05  # m³/s
+    infiltration = heat_transfer_calculator.infiltration_heat_transfer(flow_rate, delta_t, t_db, rh)
+    print(f"Infiltration Heat Transfer: {infiltration:.2f} W")
+    
     # Example psychrometric calculation
-    temp = 25.0  # °C
-    rh = 50.0  # %
-    humidity_ratio = heat_transfer_calculator.psychrometrics.humidity_ratio(temp, rh)
+    humidity_ratio = heat_transfer_calculator.psychrometrics.humidity_ratio(t_db, rh)
     print(f"Humidity Ratio: {humidity_ratio:.6f} kg/kg")