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2671
www.ijifr.com Copyright © IJIFR 2015
Reviewed Paper
International Journal of Informative & Futuristic Research ISSN (Online): 2347-1697
Volume 2 Issue 8 April 2015
Abstract
A model of solar assisted refrigeration system is presented in this paper. Principle that is used in this absorption refrigeration system is that it uses three gases to accomplish its cooling effect namely helium, water as absorbent and ammonia as refrigerant. It works without making use of any mechanical work. The purpose of helium in the system is to reduce the partial pressure of ammonia vapour in the evaporator chamber so that more ammonia evaporates yielding more cooling effect. Here ammonia is used as the refrigerant as it is easily available. Thermal (heat) energy is given as input to the generator where aqua ammonia is heated to get ammonia vapours. Heat pipe evacuated tube is used as the solar thermal energy collector. In this model, absorption refrigeration is made to work using solar energy by supplying heat to the system. Solar thermal energy is concentrated in the generator pipes by the evacuated tube solar thermal collector, heating the ammonia solution. This system has of no moving parts like compressor or pumps. For a driving temperature in the range of 120°C –150°C, low temperatures up to 8°C to 0°C is obtained at the refrigerator cabin.
Solar Assisted Refrigeration System Paper ID IJIFR/ V2/ E8/ 067 Page No. 2671-2676 Subject Area
Mechanical
Engineering
Key Words Ammonia Refrigeration, Evacuated Vacuum Tubes, Solar Collectors
Arjun V 1
B.E. Student
Department of Mechanical Engineering
SJB Institute of Technology , Kengeri, Bengaluru-Karnataka
Chetan Kumar 2
B.E. Student
Department of Mechanical Engineering
SJB Institute of Technology , Kengeri, Bengaluru-Karnataka
Narendra M 3
B.E. Student
Department of Mechanical Engineering
SJB Institute of Technology , Kengeri, Bengaluru-Karnataka
Vinay G 4
B.E. Student
Department of Mechanical Engineering
SJB Institute of Technology , Kengeri, Bengaluru-Karnataka
Madhusudhan. T 5
Professor & Head
Department of Mechanical Engineering
SJB Institute of Technology , Kengeri, Bengaluru-Karnataka
2672
ISSN (Online): 2347-1697 International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 8, April 2015 20th Edition, Page No: 2671- 2676
Arjun V, Chetan kumar, Narendra M, Vinay G and Madhusudhan. T :: Solar Assisted Refrigeration System
1. Introduction
Most of the refrigeration systems that are available uses electricity or mechanical energy as
the source of power. But mechanical energy causes wear and tear whereas there are remote places
where electrical energy is not available. This project was developed to provide refrigeration in
places where convectional energy sources were not available. The design of refrigeration system that
works on solar power is carried out. Solar power operated system is considered as an alternative for
convectional refrigeration system. And by adopting this method we can save electricity and also
provide refrigeration in all remote places.
An absorption refrigeration (DAR) cycle was first invented in 1920 by Platen and Munters,
students of Royal Institute of Technology, Stockholmin Sweden. It was a three fluid working system
where hydrogen, water as absorbent and ammonia as refrigerant were used. The system that was
invented used only thermal energy and no mechanical or electrical energy was required to run this
system. As there was no moving parts mechanical wear and tear or noise or mechanical vibrations
were not produced. These units were generally used in remote places where there was no electricity
and these systems were powered by kerosene lamp or candle flame.
2. Working Principle
2.1 Refrigerator
A schematic diagram of an ammonia refrigerator is shown in the figure 1
Figure 1: Absorption System
In the receiver the ratio of ammonia and water is 7:13 by mass. When a temperature of 105°C is
provided to the generator tubes vapours of ammonia are formed which forms bubbles that push
through the liquid column due to differences in its densities. The vapours also contain some liquid
which is separated by the separator. Solution with 10% to 15% concentration comes back. The
2673
ISSN (Online): 2347-1697 International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 8, April 2015 20th Edition, Page No: 2671- 2676
Arjun V, Chetan kumar, Narendra M, Vinay G and Madhusudhan. T :: Solar Assisted Refrigeration System
amount of ammonia and helium that leaves the separator is approximately 1 bar and 8 bar. Ammonia
evaporates at 30°C to 20°C in this condition. A partial pressure of 3 bar is obtained because
ammonia continues to evaporate. The air cooled absorber absorbs this ammonia vapor which is
converted into ammonia solution. The weak ammonia solution then moves to the receiver to
complete the cycle. There is a large density difference between ammonia and helium, where the
density of helium is very low.
This ammonia helium vapour tends to flow down as it is heavy and it enters the evaporator (cabin)
and heat is transferred between the two. As a result the temperature of the cabin reduces. Then it
enters the absorber where the ammonia is absorbed by the solution. The vapour becomes lighter and
hence moves upwards. This causes the circulation of the helium in circuit. This circulation has
effects the absorption rate in the absorber and the evaporation rate in the evaporator. Helium reduces
the cooling capacity of the system as the gas is comparatively warmer and also effects the mass
transfer rate in the system.
Even though this refrigeration has many advantages the COP of this refrigerator is comparatively
less. It is very complicated in design and also if there is some problem with the circuit the whole
circuit has to be replaced which increases the cost of the system.
2.2 Solar Evacuated Vaccum Tubes
Evacuated vacuum tubes works based on the principle of thermo siphon as shown in figure 2. The
manifold is always located high above the collector. Sun rays falls on the outer glass tube and then
falls on the absorptive layer of the tube. The rays that are absorbed are converted into heat which is
then transferred to the inner glass tube and then to the fluid inside the tube. Due the rise in the
temperature of the fluid the hot fluid rises up towards the manifold and the fluid which was lower
temperature flows down to the tubes to be heated up. This fluid displacement is continuous and
hence the whole fluid gets heated up. For a driving temperature of 25°C to 35°c the temperature of
the fluid increases up to 100°C to 185°c depending on the fluid used . The tilt angle may vary from
15° to 55° depending on the purpose for which the tubes are used. Even the tilt angle has great effect
on the efficiency of the tubes. The specifications of the tubes that are used are given below in table
1.2.1.
Figure 2 : Evacuated Vacuum Tubes
2674
ISSN (Online): 2347-1697 International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 8, April 2015 20th Edition, Page No: 2671- 2676
Arjun V, Chetan kumar, Narendra M, Vinay G and Madhusudhan. T :: Solar Assisted Refrigeration System
Table 1: Specifications
Length (Nominal) 1800 mm
Inner tube diameter 47 mm
Outer tube diameter 58 mm
Glass thickness 2.0mm
Material Borosilicate glass 3.3
Absorptive coating Graded A1/N/A1ALN/AINSS/CU
Vacuum P< 5 X10-3
Pa
Thermal expansion 3.3 x10-6
/°C
Stagnation temperature ˃250°C
Absorbance (AM 1.5) >93 %( A1/N/A1) / >96 %
(ALN/AIN-SS/CU)
Emittance (80°C/176°F) <8 %( A1/N/A1) / <5 %
(ALN/AIN-SS/CU)
Heat loss <0.8W/(m2°C)
Start-up temperature <= 25°C (77°F)
3. Solar assisted refrigeration setup
In this setup the refrigerator is kept at a certain height as the heat has to be transmitted by
thermosiphon. Tubes are run from the manifold to the heat exchanger and these tubes are insulated.
The heat exchanger is attached to the generator by means of clamp. The heat exchanger is also well
insulated with rock wool. When the solar evacuated vacuum tubes are exposed to sun, heat is
absorbed by the tubes which is transferred to the manifold and then to the heat exchanger. This
temperature is transferred to the generator pipes which will start the refrigeration process. The
proposed model is shown in the below figure 3.
Figure 3: Solar Refrigeration System
2675
ISSN (Online): 2347-1697 International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 8, April 2015 20th Edition, Page No: 2671- 2676
Arjun V, Chetan kumar, Narendra M, Vinay G and Madhusudhan. T :: Solar Assisted Refrigeration System
4. Benefits
These systems have greater advantage over the convectional refrigeration because they use solar
energy as their input, they don’t have any moving parts which increases the life of the system, can be
used in remote and rural areas where electrical energy is not available, with minimum running
expense this system can be used efficiently and this design can be used to build cold-room’s to
preserve vegetables and fruits. However the COP of the system is comparatively low when
compared to conventional refrigeration systems, solar energy is not available all 365 days and hence
and another backup of heat source should be provided for the functioning of system when solar
energy is not available and hence a hybrid system proves better efficient when compared to
complete solar refrigeration.
5. Conclution
A solar thermal driven absorption system is designed. And for a driving temperature in the range of
120°C –150°C, low temperatures up to 8°C to 0°C is obtained at the refrigerator cabin can be
achieved by using this design. Even though this design are certain disadvantages the advantages are
very high and to attain a year round working an electrical heater can be combined with this device.
This system would reduce the power consumption and would direct us towards the path of green
energy.
References
[1] K. Lingeswaran and C. Hemalatha, “Experimental Studies on Solar Powered Diffusion Absorption
Refrigerator”, Middle-East Journal of Scientific Research 20 (7): 876-880, 2014 IDOSI Publications,
2014 , pp 879-880 (2014)
[2] Dharamvir Mangal, Devander Kumar Lamba, Tarun Gupta & Kiran Jhamb, “Acknowledgement Of
Evacuated Tube Solar Water Heater Over Flat Plate Solar Water Heater”. International Journal of
Engineering (IJE), Volume (4): Issue (4), pp 279-284
[3] O.B Akinbisoye, I.F Odesola, “Experimental Study of Absorptive Solar Powered Refrigerator in
IBADAN (Nigeria) - 1: Performance in Actual Site”, International Journal of Engineering and
Technology Volume 3 No. 3, March, 2013, pp 381-389 (2013)
[4] R T Dobson and J C Ruppersberg, “Flow and heat transfer in a closed loop thermosyphon. Part I –
theoretical simulation”, Journal of Energy in Southern Africa • Vol 18 No 3 • August 2007, pp 32-40
(2007)
[5] Dimitrios A. Kouremenos, Athina Stegou-Sagia and Rizos Krikis, “Quantum Effects and Properties
of the Helium-Ammonia Mixture for Neutral Gas Absorption Refrigeration”, Forschung Im
Ingenieurwesen Bd. 55 (1989) Nr. 4 , pp 110-116 (1989) [6] Pongsid Srikhirin, Satha Aphornratana, “Investigation of a diffusion absorption refrigerator”, 2002
Elsevier Science Ltd. PII: S1359-4311(02)00049-2 (2002)
Biographies
Arjun.V is a B.E student in department of mechanical engineering from SJB
Institute of Technology, Bangalore. His interests are in the fields of solar
energy, refrigeration, air-conditioning, thermodynamics and fluid dynamics.
2676
ISSN (Online): 2347-1697 International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 8, April 2015 20th Edition, Page No: 2671- 2676
Arjun V, Chetan kumar, Narendra M, Vinay G and Madhusudhan. T :: Solar Assisted Refrigeration System
Cheatan Kumar is a B.E student in department of mechanical engineering from SJB
Institute of Technology, Bangalore. His interests are in the fields of solar energy,
refrigeration, air-conditioning, thermodynamics and fluid dynamics.
Narendra M is a B.E student in department of mechanical engineering from SJB
Institute of Technology, Bangalore. His interests are in the fields of solar energy,
refrigeration, air-conditioning, thermodynamics and fluid dynamics.
Vinay G is a B.E student in department of mechanical engineering from SJB Institute
of Technology, Bangalore. His interests are in the fields of solar energy, refrigeration,
air-conditioning, thermodynamics and fluid dynamics.
Prof. Madhusudhan T is a faculty serving as head of department of mechanical
department SJBIT, has a vast experience in engineering academics. His special
interest areas are automobile systems, polymer composites, renewable energy sources
and dynamics of machines.