- (a) Sketch a vapour compression refrigeration system, labelling the main components.(5)
(b) Indicate the refrigerant conditions at the salient points on the sketch in part(a).(5)
A vapour compression refrigeration system
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:
- 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
- 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
- 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
- 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
- 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:
- The refrigerant vapor enters the compressor at low pressure and temperature. 1. The Vapor Compression Refrigeration Cycle, Step By Step – ARANER www.araner.com
- The compressor increases the pressure and temperature of the vapor. 1. How Vapor-Compression Cooling Works www.electronics-cooling.com
- 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
- 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
- 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
- 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.
Refrigerant conditions at the salient points
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.