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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



Narendra M 3

B.E. Student



Vinay G 4

B.E. Student



Madhusudhan. T 5

Professor & Head



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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

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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

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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

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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.

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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.

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