Refrigerant Temperature Pressure Chart

Overview

Engineering reference data for Refrigerant Temperature Pressure Chart in fluid mechanics.

Key Formulas

Reynolds Number

$Re = \frac{\rho v D}{\mu}$

Ratio of inertial to viscous forces — determines flow regime.

Bernoulli's Equation

$P + \frac{1}{2}\rho v^2 + \rho g h = \text{const}$

Conservation of energy for steady, inviscid, incompressible flow.

Continuity Equation

$A_1 v_1 = A_2 v_2$

Conservation of mass for incompressible flow.

Darcy-Weisbach

$\Delta P = f \frac{L}{D} \frac{\rho v^2}{2}$

Pressure drop due to friction in a pipe.

Variables

Symbol	Description	Unit
$Re$	Reynolds number	—
$\rho$	Fluid density	kg/m³
$v$	Flow velocity	m/s
$D$	Characteristic dimension	m
$\mu$	Dynamic viscosity	Pa·s
$P$	Pressure	Pa
$f$	Darcy friction factor	—

Reading Temperature-Pressure Charts

These charts display the saturation temperature (boiling point) for a refrigerant at a given absolute pressure. They are fundamental tools for diagnosing system performance.

How to Use the Chart

1. Find your measured pressure. Locate the pressure (psig or kPa gauge) on the vertical axis of the chart for your specific refrigerant.
2. Move horizontally from your pressure reading to the refrigerant's curve.
3. Drop vertically down to the horizontal axis to read the corresponding saturation temperature (°F or °C).

This temperature is what the refrigerant should be at that pressure if it is in a stable liquid/vapor state (e.g., in the evaporator or condenser).

Key Interpretation

• Evaporator: The low-side pressure corresponds to the desired evaporator saturation temperature. A higher superheat reading indicates the refrigerant is fully vaporized and warming up.
• Condenser: The high-side pressure corresponds to the condenser saturation temperature. The subcooling reading indicates the refrigerant is fully liquid and cooling down below this point.

Important Note: Always use the chart specific to the exact refrigerant in the system. While pressure-temperature relationships are similar for some refrigerants (e.g., R-22 and its replacements), using the wrong chart will lead to incorrect diagnoses. Manufacturers often provide detailed charts with their equipment.

References

• Original Source