"Refrigerants absorb heat by boiling in cold spaces and reject heat by condensing in warm spaces. By controlling pressure, we control when and where these phase changes occur; this enables heat to be moved from cold to warm places."
Assumptions
Thermodynamic Model: This simulation uses the Antoine equation (an empirical fit) to calculate how pressure and temperature relate to each other when the refrigerant changes phase (boils or condenses). This gives us a simplified but accurate view of how real refrigerants behave.
Refrigerant Properties: Select a refrigerant below. Key properties include latent heat of vaporization (energy needed for phase changes), boiling point at atmospheric pressure, and specific heat values for liquid and vapor phases.
Simplifications: The simulation assumes that all energy changes (enthalpy) represent heat transfer to/from the environment. In real systems, energy also goes into compression work, but we're focusing on heat transfer to understand the basic cooling effect.
Pressure Units: All pressures are in bar absolute (not gauge). 1 bar ≈ 1 atm ≈ 100 kPa. "Absolute" means 0 bar = perfect vacuum. A tire gauge reads gauge pressure (absolute minus atmospheric), so 3 bar absolute ≈ 2 bar gauge. Absolute pressure is standard for thermodynamic calculations and refrigerant tables.
Refrigerant State
Pressure?7.0 bar
Temperature?-10.0 °C
Boiling Point?22.8 °C
Specific Enthalpy?186.0 kJ/kg
Latent Heat?228.1 kJ/kg
Phase State
SUBCOOLED LIQUID
Heat Transfer
P-H Diagram
Current Enthalpy?420.5 kJ/kg
Previous Enthalpy?420.5 kJ/kg
Heat Transfer (ΔH)?0.0 kJ/kg
Process Type?No Change
Latent Contribution?0.0 kJ/kg
NO HEAT TRANSFER
Start here!
VALUES
PRESS
0 bar
TEMP
0 °C
ENV
0 °C
ENTHALPY
0 kJ/kg
LATENT
0 kJ/kg
Key Terms
Refrigerant
A special liquid that can easily change between liquid and gas at normal temperatures. It's like the "blood" of your air conditioner; it flows through the system, absorbing heat in one place and releasing heat somewhere else.
Enthalpy
The total heat energy stored in the refrigerant. Think of it like a rechargeable battery; the more energy it has, the higher the enthalpy number. Includes both temperature energy and phase-change energy.
Latent Heat
The "hidden" energy needed to change between liquid and gas without changing temperature. When water boils at 100°C, it needs extra energy just to turn into steam; that's latent heat!
Evaporation
Liquid turning to gas, which absorbs heat and cools the surroundings. This is what happens in your AC's indoor unit; the refrigerant boils and sucks heat out of your room air.
Condensation
Gas turning to liquid, which releases heat and warms the surroundings. This happens in your AC's outdoor unit; hot vapor turns back into liquid and heats up the outside air.
Sensible Heating/Cooling
Temperature going up or down without changing phase. You can "sense" this heat transfer because the temperature changes; for example, heating water from 20°C to 80°C.
Subcooled Liquid
Liquid that's cooler than its boiling point. Like water at room temperature; perfectly happy being liquid with room to absorb more heat before boiling.
Saturated
Right at the boiling point; ready to change phase. Any heat added causes boiling; any heat removed causes condensation. Temperature stays constant during phase change.
Superheated Vapor
Gas that's hotter than it needs to be to stay gas. It has extra heat energy stored beyond what's needed to just be vapor.
Refrigerant Comparison
Property
R-134a
R-290 (Propane)
Contrast
Latent Heat
217 kJ/kg
425 kJ/kg (nearly double)
Huge visible jump in the enthalpy bar and latent bar during evaporation/condensation. Shows why hydrocarbons can provide more cooling per kg of refrigerant (higher efficiency).
Boiling Point (1 bar)
-26.1 °C
-42.1 °C
Different saturation curves on the phase chart; propane boils at much colder temperatures at the same pressure. Demonstrates how refrigerant choice affects operating temperature range.
GWP
1430 (high)
3 (near zero)
Stark environmental difference; illustrates the push away from high-GWP synthetic HFCs toward natural refrigerants.
Safety Class
A1 (non-flammable, non-toxic)
A3 (highly flammable)
Highlights real-world trade-offs: excellent environmental/efficiency properties come with significant safety challenges (charge limits, special system design).
Typical Use
Automotive AC, older systems
Small commercial fridges, some heat pumps, growing in eco-friendly applications