modelExercise10HeatPump

Information

Example of a two-stage vapor-compression heat pump with an intermediate-pressure flash chamber to heat a residential building.

Index reduction requires considerInertance = false in Open Modelica, see UsersGuide.InertanceNeglect.

English problem description

The system consists of a low-pressure circuit (states 1 to 4) and a high-pressure circuit (states 5 to 8). Both circuits are coupled via an externally adiabatic intermediate pressure flashChamber at 6 bar.

The working medium for this refrigeration process is R134a, passing through the following states and processes:

Low-pressure circuit:

• 1 → 2: adiabatic throttling of the saturated liquid to p2 = 1.00 bar in the lowPressureValve
• 2 → 3: complete, isobaric evaporation with heat uptake from the environment in the evaporator
• 3 → 4: adiabatic compression of dry saturated vapor to p4 = 6.00bar in the lowPressureCompressor; isentropic compressor efficiency 0.800

High-pressure circuit:

• 5 → 6: adiabatic compression of dry saturated vapor to p6 = 14.0 bar in the highPressureCompressor; isentropic compressor efficiency 0.800
• 6 → 7: complete, isobaric condensation with heat transfer to the heating water in the condenser
• 7 → 8: adiabatic throttling to p8 = 6.00bar in the highPressureValve

In the externally adiabatic waterHeater, the heating water mass flow (200 g/s, cW = 4.18 kJ/(kg·K)) is heated from 20.0 degC to 44.0 degC.

All state changes are considered steady-state.

Components

Contents

Revisions

• 2026, by Raphael Gebhart (raphael.gebhart@dlr.de):
  Initial version.