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Refrigeration Cycle (Air Conditioning)

This example shows a refrigeration cycle for a home air conditioning system. See Modeling Refrigeration Cycle for the recommended steps to build this model in the two-phase fluid domain.

The refrigerant in this system is R-410a. The evaporator absorbs heat from the air in the house and turns the refrigerant into a superheated vapor. The compressor then pressurizes and drives the refrigerant through the condenser, where the heat absorbed by the refrigerant as well as the compression work is rejected to the external environment. This causes the refrigerant to condense into a subcooled liquid and is then stored in the liquid receiver. The thermostatic expansion valve controls the amount of refrigerant that flows from the liquid receiver to the evaporator to maintain a desired amount of superheat. The valve also causes a drop in pressure which cools the refrigerant and allows it to absorb heat in the evaporator.

The cooling load in this model is the house, respresented as a volume of air in the moist air domain. A thermal network models heat transfer between the hot external environment and the air in the house via the walls, roof, and windows. Additionally, occupants and appliances generate heat inside the house. A fan circulates air between the house and the evaporator for cooling. The system is controlled by a thermostat which turns the system on and off to maintain a temperature of 22 degC.

Model

External Environment Subsystem

House Subsystem

House Thermal Network Subsystem

Simulation Results from Scopes

Simulation Results from Simscape Logging

This plot shows the heat transfer in the condenser and the evaporator as well as the power consumed by the compressor and fans. The coefficient of performance is the ratio of the evaporator heat transfer to the total power consumed.

This plot shows the high and low pressure in the refrigeration cycle and the corresponding saturation temperatures. The design condensing temperature is 45 degC and the design evaporating temperature is 5 degC. The design refrigerant mass flow rate is 0.1 kg/s.

This plot shows the subcooling at the condenser outlet and the superheat at the evaporator outlet. The thermostatic expansion valve meters the flow into the evaporator in order to maintain a superheat of 5 degC.

Pressure-Enthalpy Diagram

This figure shows the fluid states in the refrigeration cycle plotted on a p-h diagram. The cycle points are compressor inlet, condenser inlet, liquid receiver inlet, thermostatic expansion valve inlet, and evaporator inlet. The background contours are lines of constant temperatures for the refrigerant R-410a and the grey curve represents the saturation dome.