epsilon_SensibleHeatRatio

Mollier Epsilon (ε)

It is defined as Δ enthalpy/Δ humidity ratio. In thermodynamic terms, it represents the rate of change of enthalpy to the humidity ratio at constant pressure and temperature.

ε = Δh / Δx

Where:

• Δh is the change in enthalpy
• Δx is the change in humidity ratio.

Mollier Epsilon (ε) can also be defined in terms of the total heat gain in relation to the moisture gain under design conditions. This definition provides a perspective on the total heat (both latent and sensible) added per unit of moisture added to the system.

The equation for this definition of ε is:

ε = (Sensible Gain + Latent Gain) / w

Where:

• Sensible Gain is the sensible heat gain in the system.
• Latent Gain is the latent heat gain in the system.
• w is the moisture gain (water vapor emission) under design conditions, measured in kg/s.

Sensible Heat Ratio (SHR)

This is defined as the ratio of the sensible heat gain to the total (sensible plus latent) heat gain.

SHR = Sensible Gain / (Sensible Gain + Latent Gain)

Latent Heat Gain Calculation

Latent Heat Gain is a crucial factor in HVAC systems, representing the energy associated with the phase change of water from liquid to vapor. This energy transfer can be quantified using the formula:

Latent Heat Gain = w × r_0 + c_p,W * (t-t_ref)

Where:

• w: Represents the moisture gain, indicating the rate at which water vapor is introduced into the air. It's quantified in kilograms per second (kg/s).
• r_0: Stands for the Latent Heat of Vaporization of water. This value is essential for understanding the energy required to effect a phase change in water at a given temperature and pressure. 2501 [kJ/kg] at temparture 0 degC
• c_p,W: Represents Specific Heat Capacity of Water Vapor [kJ/kg°C]
• t: Represents actual temperature of the air [°C]
• t_ref: Represents baseline temperature used to define the standard conditions - commonly, this is 0°C,

In the realm of HVAC and building systems design, accurately calculating the Latent Heat Gain is imperative for effective humidity control and maintaining indoor air quality.

$$ SHR=1-\frac{r_0+c_{p,W}\cdot\left(t-t_{\mathrm{ref}}\right)}{\epsilon} $$

$$ \epsilon=\frac{r_0+c_{p,W}\cdot\left(t-t_{\mathrm{ref}}\right)}{1-SHR} $$