Equations

Enthalpy:

1. For Humidity Ratio Greater Than Saturation Humidity Ratio and Dry Bulb Temperature Greater Than 0 (Liquid Fog Scenario):

$$ \text{result} = c_{\text{air}} \times T_{\text{db}} + W_{\text{sat}} \times (L_{\text{vap}} + c_{\text{vap}} \times T_{\text{db}}) + (W - W_{\text{sat}}) \times c_{\text{water}} \times T_{\text{db}} $$

$$ \begin{aligned} &\text{Where:} \\ &c_{\text{air}} = \text{Specific heat of air (kJ/kg K)} \\ &T_{\text{db}} = \text{Dry bulb temperature (°C)} \\ &W_{\text{sat}} = \text{Saturation humidity ratio (kg/kg)} \\ &L_{\text{vap}} = \text{Latent heat of vaporization (kJ/kg)} \\ &c_{\text{vap}} = \text{Specific heat of water vapor (kJ/kg K)} \\ &W = \text{Humidity ratio (kg/kg)} \\ &c_{\text{water}} = \text{Specific heat of water (kJ/kg K)} \end{aligned} $$

2. For Humidity Ratio Greater Than Saturation Humidity Ratio and Dry Bulb Temperature Less Than or Equal to 0 (Ice Fog Scenario):

$$ \text{result} = c_{\text{air}} \times T_{\text{db}} + W_{\text{sat}} \times (L_{\text{vap}} + c_{\text{vap}} \times T_{\text{db}}) + (W - W_{\text{sat}}) \times (-L_{\text{melt}} + c_{\text{ice}} \times T_{\text{db}}) $$

$$ \begin{aligned} &\text{Where:} \\ &L_{\text{melt}} = \text{Latent heat of melting (kJ/kg)} \\ &c_{\text{ice}} = \text{Specific heat of ice (kJ/kg K)} \end{aligned} $$

3. For Humidity Ratio Less Than or Equal to Saturation Humidity Ratio (Moist Air Scenario):

$$ \text{result} = c_{\text{air}} \cdot T_{\text{db}} + W \cdot (L_{\text{vap}} + c_{\text{vap}} \cdot T_{\text{db}}) $$