1 |

Introduction- Condensing Unit Components

2 |

Refrigeration System: realisation

• Evaporator ( 1 )

–low temperature

–low pressure

• Condenser ( 2 )

–high temperature

–high pressure

• Expansion device ( 3 )

–throttle

–keeps pressure differential

• Compressor ( 4 )

–pumps refrigerant

1

43

2Q.

Q.

P

3 |

The Simple Refrigeration System

Compressor

Condenser Evaporator

Expansion device

Low pressure sideHigh pressure side

4 |

The Simple Refrigeration System

Compressor

Evaporator

Condenser

Expansion valveIncrement pressure

Remove heat outdoor

Cooling air / WaterReduce pressure

5 |

Refrigeration Cycle

Enthalpy

Compressor

CondenserReceiver

Pressure

Evaporator

6 |

The compressor

The task of the compressor is to increase the pressure of the superheated vapour coming from the evaporator so that it can be condensed via a normal available media such as air or water.

The discharge pressure ( condensing pressure ) is solely determined through the medium ( water / air ) used in the condenser. The condensing pressure is not determined by the compressor.

The capacity of the compressor is normally controlled by the suction pressure. Capacity control can be performed via cut-in / cut-out of cylinders or by controlling the speed of the electric motor.

On very small plants the compressor is normally controlled synchronously with the thermostat, without capacity control.

7 |

Compressor

8 |

Semi Hermatic Compressor

9 |

Hermatic Compressor

10 |

Condenser

11 |

Condenser

The condenser is a heat exchanger in which the heat from the evaporatorand the electric motor isremoved from the refrigerationsystem.

In the condenser the heat fromthe discharge gas is transferredto the water, air or combinationof the two (evaporative).

Water-cooled

Air-cooled

Evaporative

12 |

Water-cooled condensers

Modern type with special copper tubes with very large internal and external surfaces

13 |

Air-cooled condenser

14 |

Ball Valve – Stop Valve

• The stop valve is used on discharge, liquid and suction line• The function is to isolate part of system for service, diagnostic

and measuring

15 |

Filter Drier

• Protect systems from moisture, acids, and solid particles

16 |

The Function of a Filter Drier in a Refrigeration System

Remove other solid contaminants, corroded materials and acid.

Protect the refrigeration system by capturing harmful substances.

Minimizes chemical reactions in the system by removing foreign particles.

Molecular sieve prevents ice formation in the expansion device.

Filter Driers – Operation

17 |

Sight Glass

• The sight glass is used to indicate the condition of liquid in the line

• The moisture content in the refrigerant

18 |

19 |

20 |

The expansion valve

The task of the thermostatic expansion valve ( TEV ) is to supply the evaporator with the correct amount of liquid during all load conditions.

It ensures that the refrigerant is evaporated and that the vapour has a certain amount of superheat when it leaves the evaporator.

This ensures that the evaporator is used to the optimum and that no liquid comes back to the compressor.

The TEV valve is designed for one specific refrigerant.The TEV valve is a P-controller, which means that superheat increases as the degree of opening of the valve increases.

TEV

21 |

22 |

Evaporator

• Protect systems from moisture, acids, and solid particles

23 |

The primary task of the evaporator is to cool the dedium to the required temperature. An air-cooled evaporator is, as the word indicates, surrounded by air.

Normally this air is cooled by counterflow.

The purpose of the fins on the evaporator is to make it more effective. The fin increase the heat transfer surface of the evaporator significantly.

Heat is transferred mainly by conduction.

The difference between evaporator temperature and air temperature is normally between 6 - 10 K. This difference ( LMTD) is an expression for the load on the evaporator.

To ensure that the evaporator is effective and has capacity to cool the air, it is defrosted at certain intervals.

Evaporator

24 |

Ceiling-mounted evaporatorNatural air circulation

Ceiling-mounted evaporatorForced air circulation

Evaporators

Fig. 20. The electronic expansion valve.

Set point

∆ts ∆t

ti = 0 °C

te = -4 °Cts = 1 °K

Plate heat exchanger

25 |

Evaporator cross-section

26 |

Solenoid Valve

• To automatic shut down the system when the temperature achieved

27 |

Pressure Switch

• Protect system from high and low pressure

28 |

Protective Function:pressure limiting and cut out against excessive pressures, against loss of charge

Control Function:compressor cycling, fan-cycling, pump-down

Application

Pressure Switch

29 |

Thermostat/Control

• Shut down the system when temperature achive