Cooling Heating Efficiency

Overview

Engineering reference data for Cooling Heating Efficiency in HVAC systems.

Key Formulas

Sensible Heat

$Q = \dot{m} c_p \Delta T$

Heat causing temperature change.

Latent Heat

$Q = \dot{m} h_{fg} \Delta\omega$

Heat causing moisture change.

COP (Cooling)

$COP = Q_c / W$

Coefficient of performance.

Variables

Performance & Efficiency Terminology

The table below summarizes the key efficiency metrics used in cooling and heating systems, categorized by their operating mode and typical application conditions.

Key Efficiency Formulas

Coefficient of Performance (COP):

$$COP = \frac{\text{useful energy transferred per hour}}{\text{energy applied per hour}}$$

Integrated Part-Load Value (IPLV):

$$IPLV = \frac{1}{\frac{0.01}{A} + \frac{0.42}{B} + \frac{0.45}{C} + \frac{0.12}{D}}$$

where $A$, $B$, $C$, and $D$ are the efficiency values (in kW/ton) at 100%, 75%, 50%, and 25% load, respectively.

Hot Water Radiator System COP:

$$COP = \frac{500 \cdot q \cdot \Delta t}{3143 \cdot P}$$

where $q$ is the hot water flow (gal/min), $\Delta t$ is the temperature difference between supply and return water (°F), and $P$ is the input power to the pump (kW).

Key Metric Definitions

• SEER (Seasonal Energy Efficiency Ratio): A weighted average of EER values over a range of outdoor conditions, representing the seasonal cooling efficiency for systems less than 60,000 Btu/h. Units are Btu/Wh. Higher SEER indicates greater efficiency.
• COP (Coefficient of Performance): The ratio of useful heating or cooling output to required energy input. A COP of 4 means the system moves 4 Watts of heat for every 1 Watt of electricity consumed.
• EER (Energy Efficiency Ratio): A measure of cooling efficiency at a specific, standard operating condition. Units are Btu/Wh. For hot climates, select units with an EER >10.
• IPLV (Integrated Part-Load Value): A seasonal efficiency metric for larger equipment, calculated as a weighted average of efficiency at 100%, 75%, 50%, and 25% load. It is commonly reported in kW/ton for chillers.
• Ec (Combustion Efficiency): For fuel-fired systems, the ratio of (fuel input minus flue gas losses) to fuel input. In the U.S., it is based on the higher heating value of the fuel.
• Et (Thermal Efficiency): The ratio of heat absorbed by water/steam to the heat value of fuel consumed. Combustion efficiency is typically higher than thermal efficiency.

References

• Original Source