Coolant Properties

Overview

Engineering reference data for Coolant Properties 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

Symbol	Description	Unit
$Q$	Heat transfer	W
$\dot{m}$	Mass flow rate	kg/s
$c_p$	Specific heat of air	J/(kg·K)
$\Delta T$	Temperature difference	K

Coolant Properties Overview

Secondary coolants are essential in refrigeration and HVAC systems for heat transfer when direct cooling isn't feasible. The main types include:

• Ethylene glycol – widely used in automotive and industrial applications
• Propylene glycol – preferred in food/pharmaceutical applications due to lower toxicity
• Calcium chloride – common in industrial applications requiring low temperatures
• Sodium chloride – used in ice-making and some industrial cooling systems

Temperature Conversion Formula

The relationship between Fahrenheit ($t_F$) and Celsius ($t_C$) temperatures is:

$t_C = \frac{5}{9}(t_F - 32)$

This conversion is essential when working with engineering data from different unit systems.

Key Property Comparisons

When selecting a secondary coolant, engineers typically evaluate three critical properties:

1. Specific gravity – affects system pumping power and heat transfer capacity
2. Freezing point – determines minimum operating temperature
3. Viscosity – impacts pumping requirements and heat transfer efficiency

These properties vary significantly with concentration and temperature, requiring careful system design.

References

• Original Source