Aaditya V Mishra1 2 6 4 8 4 0 0 0 1
Abdul K Fahad1 2 6 4 8 4 0 0 0 2
Abhijeet Singh1 2 6 4 8 4 0 0 0 3
“ Lithium Bromide absorption Refrigeration System ”
Mechanical EngineeringPresentation on
Introduction to Absorption System
• An absorption refrigerator is a refrigerator that uses a heat source which provides the energy needed to drive the cooling process.
• Absorption cooling was invented by the French scientist Ferdinand Carré in 1858.
• The original design used water and sulphuric acid.
Comparison between Absorption and Compressor refrigerators
• The main difference between the two systems is the way the refrigerant is changed from a gas back into a liquid so that the cycle can repeat.
• The Compressor refrigerators used to contain compressor as a necessary Integral where as Absorption System replaces this with a chemical Compression System.
• Lithium bromide is a highly hydroscopic salt which acts as an absorbent in case of Lithium Bromide Absorption Refrigeration System.
• The Lithium bromide solution has a strong affinity for water vapour because of its very low vapour pressure.
• It is corrosive, so care needs to be taken.
Lithium Bromide absorption refrigeration System
• This system uses a solution of lithium bromide in water.
• The water is being used as a refrigerant where as lithium bromide is used as an absorbent.
• This system is much similar to the any other absorption refrigeration system and somewhat to compressor refrigeration system.
Process 1-2-3• The water vapours from
the evaporator pass through absorber.
• Strong Lithium bromide solution is spread on this water vapour.
• This makes the solution weak.
Process 3-4-5-6• The solution is pumped to
Generator passing through a heat exchanger.
• This solution is now heated to disperse weak and Strong lithium bromide solutions.
• The additional heat supply is done in Generator.
Process 6’-7’-8’• The strong Solution is
processed through a heat exchanger and expansion valve to absorber.
• This solution is sprayed on the water vapour coming from evaporator.
Process 6-7-8• The weak solution is
passed through Condenser where it is cooled and condensed.
• The refrigerant heat exchanger looses some more heat to the vapour passing to absorber.
Process 8-9-1• The condensed solution is
passed through expansion device resulting in high pressure drop.
• This low pressure solution absorbs heat from the material in order to vaporize.
• This vapour is again fed as in process 1-2-3
ADVANTAGES OF VAPOUR ABSORBTION CYCLE• except for two small centrifugal pumps, there
are no moving parts so less number of moving parts
• step less capacity control down to 0%capacity which is not possible with reciprocating machines and centrifugals
• No Freon used • no recharging cost of refrigerant ,which will be
quite substantial and inevitable in vapor compression cycle
• low working pressure
ADVANTAGES OF REFRIGERANT MOTORS
• may be loaded until full standstill• overload safe• torque increase at mounting load• low installation cost• maintenance friendly• high power density• can be sterilized
LIMITATIONS OF ABSORPTION CYCLE• low COP• high heat rejection factor, so requirement
of higher cooling tower and pump capacities
• corrosive nature of lithium bromide corrodes the heat exchanger
LIMITATIONS OF AIR MOTORS• total used energy• noise level• maintenance intervals
• Condensed liquid refrigerant from the condenser can be used for refrigeration by passing the same through capillary tube and then to evaporator
• All the accessories of a vehicle can be made to run with the power obtained from refrigerant turbine, so as to reduce the energy loss of 2.2%
A lot of references have been made to complete this presentations which are a real research work. They Include:-• http://en.wikipedia.org/wiki/Absorption_refrigerator
• Refrigeration and Air-conditioning (http://www.textofvideo.nptel.iitm.ac.in/112105128/lec15.pdf)
• “A Textbook of Refrigeration and AirConditioning” by R.S. Khurmi and J.K.Gupta
• Absorption Heat Pumps (http://apps1.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12680)
• Lithium-Bromide Absorption Chiller (http://chem.engr.utc.edu/engr435/LiBrChiller/LiBr-Chiller.htm)
• “Quantum Series for Mechanical – 6 Sem”
• Various youtube lectures and other paper notes.
• Aaditya Vashishtha Mishra
• Abdul Kreem Fahad
• Abhijeet Singh