Heat Recovery Efficiency Calculator
Calculate temperature, moisture, and enthalpy transfer efficiency for heat recovery units in ventilation and air conditioning systems. Supports both Imperial and Metric units.
Common Energy Recovery Principles
Heat recovery units used in ventilation and air conditioning systems are based on these principles:
- Return Air Recovery Units: Used air is mixed into the supply air, transferring both sensible and latent heat directly.
- Rotating Heat Exchangers: Outlet air heats or cools an exchanger wheel that transfers energy to make-up air, including latent heat via moisture condensation.
- Air-Fluid-Air Exchangers: Heat is transferred from outlet air to a circulating fluid, then to supply air.
- Cross Flow Heat Exchangers: Heat is transferred directly through separating walls from outlet to make-up air.
- Heat Pumps: Uses additional energy to move more outlet air energy to make-up air than other systems (consumes 1/3 to 1/5 of recovered energy).
Variable Definitions
Temperature Transfer Efficiency (μt)
- t1: Temperature in outside make-up air before the heat exchanger (°C, °F)
- t2: Temperature in outside make-up air after the heat exchanger (°C, °F)
- t3: Temperature in outlet air before the heat exchanger (°C, °F)
Moisture Transfer Efficiency (μm)
- x1: Moisture in outside make-up air before the heat exchanger (kg/kg, grains/lb)
- x2: Moisture in outside make-up air after the heat exchanger (kg/kg, grains/lb)
- x3: Moisture in outlet air before the heat exchanger (kg/kg, grains/lb)
Enthalpy Transfer Efficiency (μe)
- h1: Enthalpy in outside make-up air before the heat exchanger (kJ/kg, Btu/lb)
- h2: Enthalpy in outside make-up air after the heat exchanger (kJ/kg, Btu/lb)
- h3: Enthalpy in outlet air before the heat exchanger (kJ/kg, Btu/lb)