Constant Boiling Refrigerants

Overview

Engineering reference data for Constant Boiling Refrigerants 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

Symbol	Description	Unit
$U$	Internal energy	J
$Q$	Heat	J
$W$	Work	J
$P$	Pressure	Pa
$V$	Volume	m³
$T$	Temperature	K

Common Refrigerants

The following table lists the refrigerants referenced in this content.

Refrigerant Code	Chemical Name / Description
R-717	Ammonia
R-134a	Tetrafluoroethane (HFC-134a)
R-22	Hydrochlorofluorocarbon (HCFC-22)
R-507	Azeotropic mixture (R-125/R-143a)
R-290	Propane
R-744	Carbon Dioxide (CO₂)

Pressure-Temperature Relationship

The fundamental relationship governing a refrigerant's boiling point is described by its vapor pressure curve. A simplified form derived from the Clausius-Clapeyron equation is often used:

$$\ln\left(\frac{P}{P_0}\right) = -\frac{\Delta H_{vap}}{R} \left(\frac{1}{T} - \frac{1}{T_0}\right)$$

Where:

• $P$ is the pressure at temperature $T$.
• $P_0$ is a reference pressure at reference temperature $T_0$ (e.g., 101.325 kPa at $T_0 = 273.15$ K).
• $\Delta H_{vap}$ is the enthalpy of vaporization.
• $R$ is the universal gas constant (8.314 J/mol·K).

This equation shows that for a given refrigerant, the boiling temperature $T$ is a direct function of the applied pressure $P$.

References

• Original Source