Hotel Service Unit 11 Q6

A vapor-compression refrigeration system is a widely used method of cooling spaces or substances. It operates based on the principle of transferring heat from a low-temperature region (the refrigerated space) to a high-temperature region (the surroundings). This heat transfer is achieved by utilizing a refrigerant, a substance that can readily change its state between liquid and gas, and by manipulating its pressure and temperature.  

1. How Does a Compression Refrigeration System Work? | Process Solutions, Inc.

2. Vapor-compression refrigeration – Wikipedia

3. What is refrigerant, and how does it work? – Advanced Commercial Group

Main Components:

1. Compressor:

• Function: The compressor is the “heart” of the system, responsible for circulating the refrigerant. It draws in low-pressure, low-temperature refrigerant vapor from the evaporator and compresses it into a high-pressure, high-temperature vapor.   1. A Review of Small-Scale Vapor Compression Refrigeration Technologies – MDPI www.mdpi.com2. The 4 Main Refrigeration Cycle Components | The Super Blog www.superradiatorcoils.com
• Types: Reciprocating, rotary, scroll, or centrifugal compressors may be used depending on the system’s size and requirements.   1. The Vapor Compression Refrigeration Cycle, Step By Step – ARANER www.araner.com

2. Condenser:

• Function: The condenser receives the hot, high-pressure refrigerant vapor from the compressor. It facilitates heat transfer from the refrigerant to the surrounding environment (air or water), causing the refrigerant to condense into a high-pressure liquid.   1. What’s the difference between an A/C compressor and an A/C condenser? – Ernst Heating & Cooling www.ernstheating.com2. The 4 Main Refrigeration Cycle Components | The Super Blog www.superradiatorcoils.com
• Types: Air-cooled condensers use fans to dissipate heat, while water-cooled condensers utilize water circulation for heat removal.   1. Fans for heat exchangers and condensers www.ebmpapst.com.cn

3. Expansion Valve (or Metering Device):

• Function: This valve controls the flow of refrigerant from the high-pressure liquid line into the low-pressure evaporator. As the refrigerant passes through this valve, its pressure and temperature drop significantly.   1. What Is an Expansion Valve? -HUBHVACR hubhvacr.com
• Types: Several types exist, including thermostatic expansion valves (TXVs), capillary tubes, and electronic expansion valves (EEVs).   1. What Are the Different Types of Expansion Valves?-HUBHVACR hubhvacr.com

4. Evaporator:

• Function: Located in the refrigerated space, the evaporator absorbs heat from the surroundings. The low-pressure, low-temperature liquid refrigerant entering the evaporator absorbs heat and evaporates into a vapor, thereby cooling the space.   1. What is an Evaporator? What does the evaporator do? Types of evaporator – 2pt3q www.2pt3q.com2. 2-1. The refrigerant cycle – Apiste www.apiste-global.com
• Types: Evaporators can be finned-tube coils, plate evaporators, or other designs, depending on the application.   1. Evaporator – Wikipedia en.wikipedia.org

5. Refrigerant:

• Function: The refrigerant is the working fluid that circulates through the system, undergoing phase changes (liquid to gas and vice-versa) to transfer heat.   1. How does air conditioning work? – Austin Community College sites.austincc.edu
• Types: Common refrigerants include hydrofluorocarbons (HFCs), hydrocarbons, and natural refrigerants like ammonia or carbon dioxide. The choice depends on environmental considerations, safety, and efficiency.   1. Hydrocarbon Refrigerant Advantage And Disadvantage – Starget www.stargetgas.com

Additional Components:

• Filter-Drier: Removes moisture and contaminants from the refrigerant to protect the system and ensure efficient operation.   1. Filter driers: just the facts – Danfoss www.danfoss.com
• Accumulator: Prevents liquid refrigerant from entering the compressor, protecting it from damage.   1. Suction Line Accumulator Tank Function, Location, & Purpose – AC Service Tech www.acservicetech.com
• Sight Glass: Allows visual inspection of the refrigerant flow and condition.   1. Sight glasses in refrigeration systems – cold.world cold.world
• Pressure Gauges: Monitor the pressures on the high and low sides of the system for troubleshooting and diagnostics.   1. Performance Evaluation of Vapour Compression Refrigeration System With Three Layer Zig -Zag Shaped Evaporator – IJSER www.ijser.org
• Controls and Safety Devices: Thermostats, pressure switches, and other controls regulate the system’s operation and ensure safety.   1. Vol. 22 – Control, Safety & Protection Devices used in the Vapour Compression Cycle www.evomart.co.uk

The Refrigeration Cycle:

1. The refrigerant vapor enters the compressor at low pressure and temperature.   1. The Vapor Compression Refrigeration Cycle, Step By Step – ARANER www.araner.com
2. The compressor increases the pressure and temperature of the vapor.   1. How Vapor-Compression Cooling Works www.electronics-cooling.com
3. The hot vapor flows into the condenser, where it releases heat and condenses into a liquid.   1. How Does a Compression Refrigeration System Work? | Process Solutions, Inc. processsolutions.com
4. The high-pressure liquid passes through the expansion valve, expanding and cooling.   1. The 4 Main Refrigeration Cycle Components | The Super Blog www.superradiatorcoils.com
5. The cold liquid enters the evaporator, absorbs heat from the surroundings, and evaporates back into a vapor.   1. [Solved] In a Vapour Compression Refrigeration System, refrigerant ex – Testbook testbook.com
6. The vapor returns to the compressor, and the cycle repeats.   1. Vapor-compression refrigeration – Wikipedia en.wikipedia.org

By continuously circulating and changing the refrigerant’s state, a vapor-compression refrigeration system effectively transfers heat from the refrigerated space to the external environment, providing cooling and maintaining the desired temperature.  

1. Vapor-compression refrigeration – Wikipedia

The salient points in a vapor-compression refrigeration system, along with the typical refrigerant conditions at those points, are as follows:

• Compressor Suction:
  • State: Low-pressure, low-temperature vapor
  • The refrigerant enters the compressor as a vapor, having absorbed heat from the refrigerated space in the evaporator. It’s at a low pressure and temperature, typically slightly superheated (above its saturation temperature at that pressure).
• Compressor Discharge:
  • State: High-pressure, high-temperature vapor
  • The compressor does work on the refrigerant, raising its pressure and temperature significantly. The refrigerant leaves the compressor as a hot, high-pressure vapor.
• Condenser Inlet:
  • State: High-pressure, high-temperature vapor
  • The refrigerant enters the condenser in the same state as it leaves the compressor.
• Condenser Outlet:
  • State: High-pressure, warm liquid (subcooled)
  • In the condenser, heat is rejected from the refrigerant to the surrounding environment (air or water), causing it to condense into a liquid. The liquid refrigerant leaving the condenser is typically subcooled, meaning its temperature is slightly below its saturation temperature at that pressure.
• Expansion Valve Inlet:
  • State: High-pressure liquid
  • The refrigerant enters the expansion valve as a high-pressure liquid, having been condensed in the condenser.
• Expansion Valve Outlet:
  • State: Low-pressure, low-temperature liquid-vapor mixture
  • The expansion valve drastically reduces the pressure and temperature of the refrigerant, causing a portion of it to evaporate. The refrigerant leaving the expansion valve is a mixture of liquid and vapor at low pressure and temperature.
• Evaporator Inlet:
  • State: Low-pressure, low-temperature liquid-vapor mixture
  • The refrigerant enters the evaporator in the same state as it leaves the expansion valve.
• Evaporator Outlet:
  • State: Low-pressure, slightly superheated vapor
  • In the evaporator, the refrigerant absorbs heat from the refrigerated space, causing the remaining liquid to evaporate completely. The refrigerant leaving the evaporator is a slightly superheated vapor, ready to be compressed again by the compressor.

These refrigerant conditions at the salient points are crucial for the efficient operation of the vapor-compression refrigeration cycle. The pressure and temperature changes facilitate the heat transfer process, allowing the system to extract heat from the refrigerated space and reject it to the environment.