Ventilation Heat Recovery

Overview

Engineering reference data for Ventilation Heat Recovery in thermodynamics.

Key Formulas

First Law

$\Delta U = Q - W$

Energy is conserved — heat added minus work done.

Ideal Gas Law

$PV = nRT$

Relates pressure, volume, and temperature of an ideal gas.

Heat Transfer

$Q = mc\Delta T$

Sensible heat transfer.

Carnot Efficiency

$\eta = 1 - T_C/T_H$

Maximum efficiency between two temperatures.

Variables

Heat Recovery Formulas

Sensible Heat Recovery: $H = 1.08 \times q \times (t_2 - t_1) \times \eta$

Where $q$ is airflow (cfm), $t_1$ is exhaust air temperature (°F), $t_2$ is outside air temperature (°F), and $\eta$ is recovery efficiency.

Total (Enthalpy) Heat Recovery: $H = 4.5 \times q \times (h_2 - h_1) \times \eta$

Where $q$ is airflow (cfm), $h_1$ is exhaust air enthalpy (Btu/lb), $h_2$ is outside air enthalpy (Btu/lb), and $\eta$ is recovery efficiency.

References

• Original Source