Solar Flat Plate Collectors for Solar Thermal Refrigeration
Evaluation of the use of Solar Flat Plate
Collectors for Solar Thermal Refrigeration
Student Name-Dinesh Khanna
M.Tech in Energy Systems
Engineering. NMAMIT, Nitte.
Project guide: Mr. Aneesh
Jose(Asst. Professor) NMAMIT,
• PROJECT OBJECTIVE
• LITERATURE SURVEY
• COP CALCULATIONS FOR THE STVARS
• DESIGN OF STVARS
• FABRICATION OF STVARS
• OPTIMIZATION OF DESIGN
• RESULT AND DISCUSSION
• Refrigeration is the thermodynamic process to
produce cooling effect below the atmospheric
• Refrigeration may be defined as the process of
achieving and maintaining a temperature
below that of the surroundings, the aim being
to cool some product or space to the required
• Refrigeration has many applications, including
household refrigerators, industrial freezers
and air conditioning .
• The performance of refrigeration system is
evaluated in terms in Coefficient of
Performance (COP) .
1.2 Types of Vapour Refrigeration
1. Compression Refrigeration Cycle.
• The most popular and widely used system in
refrigeration and air conditioning both for
industrial and domestic applications.
1.3 Problems with VCRS
• The major share of electricity that is being
supplied with a refrigerator is consumed by the
• Since a refrigerator is operated 24 hours a day,
there is considerable energy consumption.
• The refrigerants used in these refrigerators are
• The Freon gases that are popularly used in
compression refrigerators are ozone depleting
and add on to global warming.
• The performance of vapour compressing system
is very poor at partial load.
2. Absorption Refrigeration Cycle.
• The vapour absorption system replaces the
compressor with a generator absorber set.
• The first NH3-H2O absorption refrigeration
system was developed by Ferdinand Carre in
• Combination of refrigerant and absorbent.
• Most widely use NH3-H2O & LiBr-H2O.
• In addition, the VARS use natural substances
which do not cause ozone depletion as
1.4 Solar Energy for Cooling
• Solar energy is the most readily available source
among renewable energy sources.
• With the use of solar energy, usage of
conventional energy sources and its peak
demand will be reduced.
• Utilization of solar energy for cooling was an
attractive one, as the demand for cooling is some
what in tune with the availability of heat.
• The VARS being a heat operated system, is
especially suited for refrigeration using solar
1.4.1 PV Operated Refrigeration Cycle
• PV involve the direct conversion of solar
radiation to direct current (DC) electricity
using semiconducting materials.
• DC electrical power that can be either used to
operate a dc motor, which is coupled to the
• Inverter can be used to convert this DC
current to AC current for running the
compressor of a vapour compression
1.4.2 Solar Thermal Refrigeration
• Solar thermal systems use solar heat rather than
solar electricity to produce refrigeration effect.
• The thermal component of solar energy is taken
up the working fluids in solar collector.
• The heat energy will be supplied to generator
unit that has a strong solution of refrigerant-
absorbent mixture, wherein the concentration of
refrigerant is high.
• This heat energy heats up the mixture and the
mixture should be chosen in such that, the
refrigerant has a lower boiling point than the
absorbent, so the refrigerant boils and gets
converted to vapour phase.
• The main objective of this project work is to
design and fabricate a solar thermal vapour
absorption system using ammonia as refrigerant
and water as absorbent.
• A solar flat plate collector will be used, that is
capable of providing the thermal energy required
to operate vapour absorption refrigeration unit.
• A detailed analysis on solar radiation, collector
area has to be done. After which the vapour
absorption system is to be designed and
• This new solar thermal refrigeration system
should prove better than PV refrigeration system.
Sl.No Author Title Year
1 Eng. Naser R. M. AL-
Coefficient of Performance Enhancement of
2 M. Krishna Prasanna
& P. S. Kishore
Enhancement of COP in Vapour Compression
3 Shoyab hussan Improve the cop of Vapour compression
cycle with change in Evaporator and
4 F. Memet A Performance Analysis on a Vapour
Compression Refrigeration System Generated
by the Replacement of R134a
5 Dr. A.C. Tiwari and
Performance Analysis of Vapour Compression
Refrigeration Systems Using
3.2 PV operated refrigeration
Sl.No Author Title Year
1 Navneet Kumar
Sharma, Hari Singh
Sharma and B. L.
Performance Analysis of Vapour Compression
Vapour Absorption Refrigeration Units
Photovoltaic Power Supply
2 S. R. Kalbande and
Photovoltaic Based Vapour Compression
Refrigeration System for Vaccine Preservation
3 Armand Noël
Noël Djongyang and
Modelling of the Performance of a Solar
Electric-Vapour Compression Refrigeration
System in Dry Tropical Regions
4 Kapil K. Samar, S.
Kothari and S. Jindal
Thermodynamic and economic analysis of
operated vapour compressor refrigeration
5 Mehmet Azmi
Experimental study of a multi-purpose PV-
3.3 Solar Thermal VARS
Sl.No. Author Title Year
1 D.S. Kima and C.A.
Solar refrigeration options – a state-
2 Preethu Johnson and K.
B. Javare Gowda
Fabrication of Solar of Thermal
Vapour Asorption Refrigeration
3 Subi Salim and Rajesh V Thermodynamic Analysis of Aqua-
Ammonia Based Miniaturized Vapor
Asorption Refrigeration System
Utilizing Solar Thermal Energy
4 Narale Pravin et al. Vapour Absorption Refrigeration
System by using Solar Energy
5 Anadi Mondal et al. Design & Construction of a Solar
Driven Ammonia Absorption
Sl.No Author Title Year
6 Dr. Adel et al. The use of Direct Solar Energy in
Absorption Refrigeration Employing NH3-
7 Jasim Abdulateef et
Experimental Investigation on Solar
Absorption Refrigeration System
8 Rahul Yadav and
Analytical Study of Ammonia –Water
(NH3-H2O) Vapor Absorption
Refrigeration System Based On Solar
9 K.V.N. Srinivasa Rao Low Cost Solar Cooling System 2013
Development of a solar intermittent
refrigeration system for ice production
11 Abhishek Sinha and
A review on Solar Powered Refrigeration
and the Various Cooling Thermal Energy
Storage (CTES) Systems
Sl.No Author Title Year
12 V.K.Bajpai Design of Solar Powered Vapour Absorption
13 Sameh Alsaqoor
& S. AlQdah
Performance of a Refrigeration Absorption
Cycle Driven by Different Power Sources
14 O. Babayigit et
Investigation of Absorption Cooling Application
Powered by Solar Energy in the South Coast
Region of Turkey
15 Dillip Kumar and
Thermodynamic Performance Analysis of a
Solar Vapour Absorption Refrigeration System
16 K Karthik Design, Fabrication and Analysis of Solar Vapour
Absorption Refrigeration System
17 N.D. Hingawe
Design and Analysis of Solar Electrolux Vapour
Absorption Refrigeration System
18 K.R. Ullah et al. A review of solar thermal refrigeration and
Observation from Literature Review
• Replacing the electrical energy with solar
energy will reduce the consumption of high
grade electrical energy.
• Also the replacement of compression system
with absorption system eliminates the energy
consumption by compressors.
• The overall system energy efficiency of PV
operated refrigerator was found low because
of energy conversion efficiency and exergy
efficiency of the photovoltaic system was low.
• Thermal cooling technology is preferred to PV-
based cooling systems because it can utilize
more incident sunlight than a PV system.
• Evacuated collectors have less heat loss and
perform better at high temperatures.
• Solar thermal Vapour absorption refrigeration
technology has great potential to offer
economical and innovative solutions to
various refrigeration requirements.
• Using ammonia as refrigerant in VARS has
• Aqua-ammonia VAR system integrated with solar
collector that can be used small and large scale
• The COP depends primarily on the temperatures
of the evaporator and the condenser. Also
depends on Refrigerant and the model of
generator used in VARS.
• The detailed study of these papers gave a good
idea about solar thermal vapour absorption
• It was observed that the accumulation of
ammonia, solar collector efficiency, clearness of
sky played great factor for overall efficiency.
4. COP Calculations for the STVARS
• The Coefficient of performance (COP) of the
system as theoretically known is given by
• COP= Heat Absorbed in the Evaporator / (Work
done by pump +Heat Supplied in the evacuated
or COP =Qe/(Qg+Wp).
• Negelecting pump work,
Theoretical COP = Qe/Qg
• Assumed values as follows.
High pressure = 7 bar
Generator temperature (max) = 110°C
Evaporator temperature (max) = -5°C
Qe= 1TR = 3.516 KW (Theoretical valve)
• Let m = mass flow rate of refrigerant, kg/s
• Heat absorbed at generator Qg= m (h3-h2)
• COP=3.516/m (h3-h2)
• Mass Concentrations: X1 = X2 = 0.55
X3=X5= X6 = X7= X8 = 1
X4 = 0.42
Figure 5 Circuit of STVARS
• At Pump (Aqua ammonia liquid state), Pressure = 7 bar, X2= 0.55
Temperature = 40°C, h2= 130 kj/kg
• At Evacuated tube (Ammonia vapour state), X3=1 and temperature
Pressure =7 bar, h3= 1716.4 kj/kg
• At Evaporator, taking concentration X7=1 and temperature = -5°C,
Pressure =3 bar
Applying the Energy balance
• Qe = Refrigerating effect =3.516kW = m (h8 – h7)
• = m× (1461.56-176.9)
• m=3.788/ (1461.56-176.9) = 2.94×10^-3 kg/s
• m =2.94×10^-3 kg/s = mass flow rate of refrigerant.
• Now circulation ratio, λ= X4/(X1-X4) = 3.23
• Strong solution, m1=m2= λ× m= 9.49×10^-3 kg/s
• Weak solution, m4=(1+ λ)m= 12.43×10^-3 kg/s
• So, Qg= m(h3-h2)= 2.94×10^-3 (1716.4-130) =4.66 kj/sec = 4.66 KW
• Theoretical COP=3.516/4.66 = 0.75
Statement: For such a design circuit the refrigeration system produce a
cooling capacity of COP 0.75 which a good value for applications such as
air conditioning where the temperature is not much of concern.
5. Design of STVARS
The design of solar thermal refrigeration designed considering
various criteria and assumptions. The design is done to get the
refrigeration capacity of 1 ton with required COP. The calculated
COP of the system is 0.75.Design depends on the individual
components used in the system. Following are the individual
components used in STVARS are as follows.
• Absorber tank
• PV panel
• Generator tank
• Evacuated Tubes
• Rectifier tank
• Capillary tube
• Evaporator tank
5.1 Absorber Tank
• Absorber tank is designed according the volume of
evacuated tube collectors (6ltrs) and specification of the
• Type: cylindrical tank
• Material used: Mild Steel
• Refrigerant= R717 (Ammonia)
• Absorber = Water
• Inner diameter of the tank = 260mm
• Outer diameter of the tank = 263mm
• Length of the tank = 370mm
• Total volume of the tank = V = π r^2 h=
π×(0.153m)^2×0.4m= 0.02m^3= 20.10 litres
• Volume of ammonia water solution used= V = π r^2 h =
π×(0.13m)^2×0.3m= 16 litres
Fig.7 Designed Absorber tank
WEAK SOLUTION IN
• Pump is used to pump the ammonia hydroxide
from the absorber to the generator tank attached
to the evacuated tube. It is used according to the
maximum pressure rate required and also
maintain adequate discharge flow rate at the
• Type: Auto Diaphragm DC pump
• 0.08 Hp = 60 W
• Pump flow rate = 5 ltrs/min
• Rated pressure = max 8bar
• Dimensions: 165×95×60mm
5.3 Generator Tank
Generator tank is designed to maintain steady
state level for continuous discharge and act as
accumulator above the evacuated tube. Figure 8
shows design of a generator tank .
• Type: Cylindrical tank
• Inner Diameter= 100mm
• Thickness = 2mm
• Length = 300mm
• Volume=πr^2h=π×(50)^2×300= 2.3litres
• All dimensions in cm
Fig.8 Generator tank
5.4 Evacuated Tubes
• To get higher temperature to vaporize ammonia
refrigerant, Evacuated tube collectors are used
instead of solar flat collectors. Figure 9 shows the
design of evacuated tube collectors.
• No. of Tubes = 2
• Length of the Tube = 1500mm
• Outer diameter of the tube = 58mm
• Inner diameter of the Tube = 48mm
• Volume of one tube = V = π r^2 h=
π×(23.5)^2×1500= 2.6 litres
All dimensions in cm
Fig.9 Design of Evacuated tube collectors
5.5 Rectifier Tank
• Rectifier tank is designed according to the volume of
absorber, evacuated tube collectors and cooling
required converting water vapour to liquid state. Figure
10 shows a design of rectifier tank.
• Type: Water cooled tank
• Material used = Mild steel
• Inner diameter of tank one = 200mm
• Outer diameter of the tank= 203mm
• Length of the tank = 200mm
• Thickness of inner tank = 3mm
• Capacity of the tank = V = π r^2 h = π
×(0.115m)^2×0.3m= 6.28 litres
• Copper coil length= 3m
• Copper tube diameter= 9mm
Fig.10 Design of Rectifier tank
WEAK SOLUTION OUT
• Condenser is selected to withstand the
temperature and pressure and that amount of
heat to be removed from ammonia vapour and
convert it into liquid state.
• Type: Wire and tube coil
• Material: Mild steel
• No. of turns = 26
• Outer diameter of condenser pipe= 6mm
• Thickness = 1mm
• Area of the condenser = 0.95m × 0.4 m = 0.38
5.7 Capillary tube
• Capillary tube has very small internal diameter
and it is of very long in length. It is coiled to
several turns, so that it would occupy less space.
This device connects between condenser and
evaporator to reduce the pressure. The
refrigerant comes out of capillary tube to
evaporator this change in diameter drops the
refrigerant pressure there by reducing its
• Material: Copper
• Inner diameter = 0.3mm
• Thickness = 0.1mm
• Capillary tube length = 3m
• In evaporator low temperature, low pressure
refrigerant extract the heat from the cabin or system
which we have to cool. Evaporator should be designed
to get capacity of 1 ton as the heat input is of 4.65 KW
(from COP calculations).
• Material : Mild steel
• Cylinder inner diameter = 200mm
• Cylinder length = 300mm
• Cylinder thickness= 3mm
• Volume of the thank V = π r^2 h = π×(100)^2×2= 9.42
• Coil material= Copper
• Coil length = 3m
• Coil outer diameter = 6mm
6. Fabrication of STVARS
The solar vapour absorption refrigeration system is
fabricated with reference to the designed details
using available parts and materials in market, which
is cost effective. The following are steps involved in
• 1. Selecting the type of materials and parts to be
• 2. Fabricating the cylinders and modifying the
• 3. Assembling the system as per design and
installing the instruments.
• 4. Sealing done at required spots in the system.
• 5. Testing and modifying the assembly.
• The fabrication process is done in Gajanana
machine works, Bunder Mangaluru
Fig.11 Fabricated STVARS
6.1 Fabricated Absorber Tank
• Absorber tank is fabricated with reference to
the designed details of capacity 20 litres. The
material used to fabricate is galvanized mild
steel and the thickness is 3mm.
• Arc Welding
Fig.12 Absorber tank
6.2 Diaphragm Pump
• Pump is fixed between absorber tank and
generator tank using union coupling parts of ¾
inch stainless steel, both in inlet and outlet of
• 60W DC pump
• Threading on
Fig.13 60W pump
6.3 Generator Tank with Evacuated Tubes
• Tank is fabricated with reference to designed model
of generator tank that can attached to evacuated
tubes with the help of bush, so there will be no
Fig.14 Generator tank with Evacuated tubes
6.4 Fabricated Rectifier Tank
• Rectifier tank is made up of mild steel of capacity
6.28 litres is fabricated according to the design
Fig.15 Rectifier tank
6.5 Wire and Tube Condenser
• The condenser is selected depending upon the area of the
condenser that able to give required condensation to the system.
• A wire and tube type condenser used to household refrigerator of
system 1TR is purchased in micro refrigeration bunder,
• Wire and tube condenser
is a type of natural convection
condenser used in small capacity
Fig.16 Wire and tube condenser
6.6 Copper Capillary Tube
• A capillary tube is selected by its length and
diameter for capacity one ton refrigeration
and fabricated in Christal refrigeration,
Fig. 17 Capillary tube
6.7 Evaporator tank
• Evaporator tank is fabricated according to the
design details of capacity 9.42 litres, material used
is mild steel.
• It is insulated by asbestos webbing tape.
• A 6mm diameter of 2m
copper coil is used.
Operation Performed :
• Sealing Fig.18 Evaporator tank
• Two pressures gauges of 150psi are installed, one
pressure gauge is threaded in 20mm diameter
stainless steel pipe after the pump and other one
between evaporator and absorber tank.
• Three digital thermometers
rated from -50°C to +300°C
is installed in the system,
one in absorber tank and
other two in rectifier tank
and evaporator tank .
Fig.19 Pressure gauge
• Modification is done after testing of fabricated
Fig.20 Modified System
6.10 Ammonium Hydroxide as Working fluid
• Ammonium hydroxide (NH3+H2O) solution (13 litres) is
filled in absorber tank where ammonia is the refrigerant
and water acts as absorber.
• Ammonia Solubility in H2O = 47% at 0°C , 31% at 25°C
and 18% at 50 °C
Fig.21 Ammonium hydroxide
7.Optimization of Design
• The fabricated system was found to be not
holding the system pressure in evacuated tube
The following are the areas where new
modification is put in the place due to the above
• Design of solar collector area.
• Connective areas of generator tank.
• Identification of valves
• Proper insulation in the system.
• Better instrumentations in the system.
7.1 Stainless tube Collectors
• Maximum temperature of 65 to 70°C can obtain by using
stainless tube collector.
• Rectangular box dimensions = L×W×H=
• Absorber plate area (copper)= 342mm×286mm = 0.097m^2
• Tube material used = Stainless steel
• Number of tubes = 2
• Length of the tube = 150mm
• Outer diameter of the tube= 64mm
• Thickness = 2mm
• Volume of generator tank = 2.97 litres
• Volume of the two tubes = 0.96 litres
• Quantity of ammonium hydroxide used in absorber tank = 6
• All dimensions in mm
Fig.22 Designed stainless tube collector
• Insulation is done to rectifier tank and the
stainless steel pipe connections to maintain the
required temperature in the system.
• Asbestos tapes can be used for insulation the
7.3 Finned tube Condenser
• Finned tube condenser is a type of natural convection heat
exchanger (condenser), it is suggested to a solar vapour absorption
• The optimum heat and mass transfer area can be calculated using
• t1= 70°C, t2= 45°C, T1= 30°C and T2 = 35°C
• P = 0.62 and R= 0.2, from graph F= 0.97
Fig.23 Correction factor F chart
• Assuming heat transfer co-efficient, h =10W/(m^2×K)
• The heat flow rate is the mass flow rate times the latent heat of
condensation of the ammonia = Q = m×Δh
• Mass flow rate of refrigerant = 2.94×10^-3 kg/s
• If ammonia vapour entering condenser at maximum
temperature of 70°C then
• Δh = (1484-545) = 939 kj/kg
• The log mean temperature difference ΔT = (Tc-Tai)×(Tc-Tao) /
• Tc is Condenser temperature = 45°C = 318 K
• Tai is air inlet temperature = 30°C = 303 K
• Tao is air outlet temperature = 35°C = 308 K
• ΔT = (318-303)× (318-308)/log((318-303)/(315-308) = 851.83 K
• A = (2.94×10^-3 × 939)/ (0.97×10×851.83) = 330.93
(kj/sec×m^2/w)= 0.34 m^2
7.4 Optimized Instrumentations
• For calculating COP of the system, temperature and
pressure of refrigerant flow is required to be noted at
• High pressure P1=P2=P3=P5
• Low pressure= P6=P7
• T1=Absorber temperature
• T2=Generator temperature
• T3=Rectifier temperature
• T4=Condenser temperature
• T5= Evaporator temperature
Fig.24 Circuit diagram of STVARS for instrumentations
8.Result and Discussion
• Literature review is done on different type refrigeration system mostly based on solar
• Solar thermal refrigeration is designed and fabricated with reference to the COP
• System fabrication components had drilling, welding, brazing and other operations.
• Fabrication model is tested, and find out that there is leakage in pump outlet coupling
part due to pressure as the pump in working condition.
• Modification is done by removing pump from the system and changing the position of
absorber and generator setup, also replacing the stainless steel pipes to flexible pipe.
• Ammonia solution is filled successfully as per the procedure of handling ammonium
• As the absorber tank valve is opened the solution entering evacuated tubes by
generator is failed to hold up the pressure developed by ammonia vapour and there
was gas leakage in bush to that connects generator tank and evacuated tubes.
• Design has optimized on the system by replacing evacuated tube collector by stainless
steel flat plate collectors and some minor modifications in piping and insulations.
• Optimized design is better to the system’s new design which can deal with pressure
and leakage problems and quantity of ammonia ammonium hydroxide is used is 6
• Instrumentations like new pressure gauges and ball valve has been introduced to be
used in the system as per the requirements.
• The new solar thermal refrigeration has been introduced with
ammonia as working fluid Evacuated tubes mainly to replace the
high grade electricity.
• Reviews of different area of solar thermal refrigeration system have
been carried out, designed components used in solar thermal
refrigeration system are shown in detailed with its pictures.
• To find the performance parameter of refrigeration system
instrumentation studies has been carried out and different types of
gauges and exact locations have been represented.
• The designed refrigeration system is fabricated, tested and modified
as per the requirement.
• The fabricated system when tested it was found incapable of
holding the system pressure and the evacuated tubes could not
keep itself in place. The evacuated tubes lost its vacuum pressure
not suitable for ammonia solution for present design.
• Considering the factor a new design has been introduced after
optimization which takes care of problems encountered in the
•  Prof. Dr. Adel A. Al-Hemiri and Ahmed Deaa Nasiaf, ‘‘The use of direct Solar energy
in Absorption Refrigeration employing NH3 – H2O system’’, Iraqi Journal of Chemical
and Petroleum Engineering, Vol.11 No.4 (December 2010) 13-21.
•  Preethu Johnson and K. B. Javare Gowda, ‘‘Fabrication of Solar Thermal Vapour
Absorption Refrigeration System’’, International Research Journal of Engineering and
Technology, Volume: 02 Issue: 05 | Aug-2015.
•  Shireesha Mary Ch, Nandini Ch, Divya Samala, Siva Kumar B and Parthasarathy
Garre, ‘‘A Review: Increase in Performance of Vapour Compression Refrigeration System
Using Fan’’, International Journal of Engineering and Applied Sciences (IJEAS) ISSN:
2394-3661, Volume-2, Issue-4, April 2015.
•  F. Memet, ‘‘A Performance Analysis on a Vapour Compression Refrigeration System
Generated by the Replacement of R134a’’, Journal of maritime research, Vol XI. No. III
(2014) pp 83–87.
•  Shubham Srivastava, Ravi Kumar Sen, Arpit Thakur and Manish Kumar Tated,
‘‘Review paper on analysis of Vapour Absorption Refrigeration System’’, International
Journal of Research in Engineering and Technology, Volume: 04 Issue: 06 June 2015.
•  Sachin Kaushik and Dr. S. Singh, ‘‘Thermodynamic Analysis of Vapour Absorption
Refrigeration System and Calculation of COP’’, International journal for research in
applied science and engineering technology’’, Vol. 2 Issue II, February 2014.
•  Jose Â FernaÂndez-Seara and Manuel VaÂzquez, ‘‘Study and control of the optimal
generation temperature in NH3-H2O absorption refrigeration systems’’, Applied
Thermal Engineering 21 343±357 @ Elsevier Science Ltd., March 2000.