Vapour Absorption System | Mechanical Engineering SSC JE (Technical) PDF Download

VAPOUR ABSORPTION SYSTEM

In this system, absorber, pump and generator combindely replaces compressor of vapour compression system. The refrigerant flows as
absorber ® Pump® Generator® Condenser® Expander® Evaporator

  •  Absorber: Here lies a weak solution which after absorbing the refrigerant becomes rich solution.
  •  Pump:it pumps rich solution raising its pressure to condenser pressure.
  •  Generator: It distills vapour refrigerant from rich solution making it weak solution for recycling in absorber.
    the cycle of rich solution flows as absorber ® pump ® generator ® valve ® absorber

COP = 
Vapour Absorption System | Mechanical Engineering SSC JE (Technical)

  • Vapour absorption system may be considered as a combination of heat engine & refrigerating machine.

Vapour Absorption System | Mechanical Engineering SSC JE (Technical)
Vapour Absorption System | Mechanical Engineering SSC JE (Technical)

Maximum COP

Vapour Absorption System | Mechanical Engineering SSC JE (Technical)
Vapour Absorption System | Mechanical Engineering SSC JE (Technical)

  • So for maximum COP
    •  Th should be as high as possible
    •  Tk should be as low as possible
    • T0 should be as high as possible 
    • COP of vapour absorption system first increases with generator temperature
      (Th). reaches an optimum then it decreases

REQUIREMENT OF REFRIGERANT ABSORBENT PAIR

  •  Low viscosity to minimize pump work
  •  Low freezing point
  •   Chemical & thermal stability
  •  Refrigerant should be highly soluble in absorbent
  •  Their boiling point difference should be large.

Ex. Refrigerant NH3 + Absorbent H2O
Refrigerant H2O + Absorbent LiBr2

ELECTROLUX REFRIGERATOR

  •   It works on 3 fluid System e.g.,

NH3 + H2O + H2

  •  There is no solution circulation pump
  •  Third fluid remains in the evaporator.
  •  H2 is chosen as it is non corrosive & insoluble in water.
  •  Two U bends are provided to prevent H2 from going to solution
  •  The cycle runs on the basis of partial pressure variation.

Vapour Absorption System | Mechanical Engineering SSC JE (Technical)

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FAQs on Vapour Absorption System - Mechanical Engineering SSC JE (Technical)

1. What is a vapour absorption system in mechanical engineering?
Ans. A vapour absorption system is a type of refrigeration system that uses a heat source to generate refrigeration effect. It works on the principle of absorption, where a refrigerant vapor is absorbed into a solution and then desorbed to produce cooling. This system is commonly used in industrial applications where waste heat or low-grade heat is available.
2. How does a vapour absorption system differ from a vapour compression system?
Ans. The main difference between a vapour absorption system and a vapour compression system is the method used to compress the refrigerant. In a vapour absorption system, the refrigerant is absorbed into a solution and then desorbed using a heat source, whereas in a vapour compression system, a mechanical compressor is used to directly compress the refrigerant. Vapour absorption systems are generally more energy-efficient and environmentally friendly, but they are also more complex and require a heat source.
3. What are the advantages of using a vapour absorption system?
Ans. Some advantages of using a vapour absorption system include: 1. Energy efficiency: Vapour absorption systems can utilize waste heat or low-grade heat sources, making them more energy-efficient compared to vapour compression systems. 2. Environmentally friendly: Vapour absorption systems do not require ozone-depleting refrigerants, making them more environmentally friendly. 3. Flexibility in heat source: Vapour absorption systems can use a variety of heat sources, such as natural gas, steam, or solar energy, providing flexibility in system design and operation. 4. Low noise levels: Vapour absorption systems generally produce less noise compared to vapour compression systems, making them suitable for noise-sensitive environments. 5. Long lifespan: Vapour absorption systems are known for their durability and long lifespan, resulting in lower maintenance and replacement costs over time.
4. What are the applications of vapour absorption systems in mechanical engineering?
Ans. Vapour absorption systems find various applications in mechanical engineering, including: 1. Industrial refrigeration: Vapour absorption systems are commonly used in large-scale industrial refrigeration applications, such as food processing, chemical manufacturing, and cold storage facilities. 2. Air conditioning: Vapour absorption systems can be used for air conditioning in commercial buildings, hotels, and hospitals, especially in areas where waste heat or low-grade heat is readily available. 3. Power generation: Vapour absorption systems can be integrated with power plants to utilize waste heat for cooling purposes, improving overall energy efficiency. 4. District cooling: Vapour absorption systems can be used in district cooling systems, where a centralized cooling plant supplies chilled water to multiple buildings, reducing the energy consumption of individual cooling systems. 5. Solar cooling: Vapour absorption systems can be combined with solar thermal collectors to provide cooling using renewable energy sources, making them suitable for off-grid or environmentally conscious applications.
5. What are the challenges or limitations of vapour absorption systems in mechanical engineering?
Ans. Some challenges or limitations associated with vapour absorption systems include: 1. High initial cost: Vapour absorption systems often have higher initial costs compared to vapour compression systems due to their complex design and additional components required. 2. Size and weight: Vapour absorption systems are typically larger and heavier than vapour compression systems, making them more challenging to install and transport. 3. Limited cooling capacity: Vapour absorption systems usually have lower cooling capacities compared to vapour compression systems, which may limit their applications in certain industries or environments. 4. Complex maintenance: Vapour absorption systems require regular maintenance and servicing, including monitoring the concentration of the absorbent solution and maintaining proper heat source temperatures. 5. Limited availability of suitable heat sources: Vapour absorption systems heavily rely on the availability of waste heat or low-grade heat sources, which may not always be readily available or economical to utilize.
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