ABSTRACT The demand of air conditioning is increasing day by day and it has become the major source of energy consumption

ABSTRACT
The demand of air conditioning is increasing day by day and it has become the major source of energy consumption. According to a research till 2050 it would be three times to the current usage. In Pakistan demand of air conditioning has been increased suddenly in recent past due to climate changes and the other reason is due to technology revolution living standards has been improved. But our real problem is energy crises and electricity prices are much higher and electricity produced from fuel burning has its own environmental impacts because fuel burning is one of the major sources of global warming. Because of electricity shortfall and higher cost a larger population cannot get this. So, we should go to the alternate options that we could acquire to meet the maximum demand of air conditioning. For that purpose Solar operated vapor absorption refrigerating system is one of the most attractive options available because it uses solar energy as primary source but it can be operated through waste heat but solar energy is green energy and it is free of cost so, we preferred it.
Our design is based on solar energy for operating the vapor absorption refrigerating system. For that purpose solar collector is used to provide heat in generator and photovoltaic cells are used to operate fans and pump. Less energy is required to operate this system that’s why it’s COP is less. But our requirement is to design a system that uses renewable to operate the system for sensible cooling.
The vapor absorption cooling system is an attractive option due to high energy efficiency and reduction in required power input. The solar energy provides enough energy to drive vapor absorption cooling system and can supply enough cooling in the areas that does not have electricity or it can also be used for houses in day time because peak hours for air condition demand are day timings so it can provide cooling all the day using solar energy.
Vapor absorption cooling system of 35.16 kW is analyzed in EES software. Required parameters have been analyzed in EES. Effect of different parameters on COP is observed and discussed in the report based on the values of heat transfers, mass flow rates, temperatures and pressures obtained from EES, the components of the system like Evaporator, condenser, generator and absorber are designed.
In this project we have also done thermodynamic analysis for two working refrigerants (lithium bromide and ammonia water solution) are performed. Theanalyzed parameters of working refrigerants were operating temperatures of components (i.e. evaporator and generator), coefficient of performance (COP) and chemical properties of the refrigerants. Based on the high coefficient of performance (COP), low operating temperatures and eco-friendly and suitable chemical properties, we selected lithium bromide water solution as working fluid for our project.

Contents:
General vi
Chapter 1 1
INTRODUCTION 1
1.1 Overview 1
1.2 Problem Statement 2
1.3 Project Specifications 3
1.4 Purpose of the project 3
1.5 Project Applications 3
Chapter 2 4
LITERATURE REVIEW 4
2.1 Difference between VARS and VCRS 5
2.1.1 Vapor Absorption Refrigerating System: 5
2.1.2 Vapor Compression Refrigerating system: 5
2.2 Related Studies: 5
2.2.1 Solar Cooling 5
2.2.2 Geothermal Cooling 6
2.3 Limitations 6
2.3.1 Cost: 6
2.1.1 Refrigerant Comparison 6
2.1.2 Operating pressure: 6
2.1.3 Low Coefficient of Performance: 6
Chapter 3 7
PROJECT DESIGN 7
3.1 Design and Analysis of Components 7
3.2 Comparison of the on basis of Desirable Properties 8
3.2.1 Lithium bromide-water solution system: 8
3.3 Mathematical Modeling 9
3.3.1 Operating conditions for lithium bromide water system: 9
3.3.2 Calculation of lithium bromide water system: 10
3.3.3 Graphs: 13
3.3.4 Calculation of lithium bromide water system on EES: 14
3.3.5 Pump Selection: 21
3.4 Results: 22
Chapter 4 23
TOOLS AND TECHNIQUES 23
4.1 Hardware used with technical specifications 23
4.1.1 Evaporator: 23
4.1.2 Condenser: 23
4.1.3 Absorber: 23
4.1.4 Generator: 23
4.1.5 Pump: 24
4.2 Software and simulation tools used: 24
4.2.1 Engineering Equation solver (EES): 24
4.3 Summary: 24
Chapter 5 29
Project Results and Evaluation 29
5.1 Presentation of finding: 29
5.1.1 Hardware results: 29
5.1.2 Software results: 31
5.2 Discussion of the findings: 32
5.2.1 Comparison with initial Project Specification: 32
5.2.2 Reasoning for short coming: 32
5.3 Limitations: 32
5.4 Recommendations: 33
5.5 Summary: 33
Chapter 6 34
Conclusion 34
References 35

List of Tables
Table 1: Operating condition (NH3-H2O) system. 11
Table 2: Operating conditions for (libr-H2O) system 14
Table 3: Effect of temperature on COP 25
Table 4: Final results of Evaporator 31
Table 5: Final results for condenser 32

Table of Figure
Figure 1: Absorption cycle 2
Figure 2: Vapor Absorption Cycle 8
Figure 3: Block diagram of Ammonia water system 12
Figure 4: Block diagram for lithium bromide water system. 15
Figure 5: Use for percentage concentration lithium bromide in solution. 18
Figure 6: For enthalpies calculation. 19
Figure 7: Effect of generator temperature on COP 26
Figure 8: Effect of evaporator temperature on COP 26
Figure 9: Absorber 29
Figure 10: Generator 30
Figure 11: Evaporator 30
Figure 12: DC Pump 30
Figure 13: Condenser 31
Figure 14: Manufactured Model 33

LIST OF ACRONYMS

General
SymbolDefinition

HoD Head of department
evp Evaporator
cond Condenser
shx Solution heat exchanger
abs Absorber
rec Rectifier
gen Generator

EES code

Mi Mass flow rate (i=1, 2, 3…..)
P, p Pressure
Q, q Quality, Heat Transfer
T, t Temperature
h Enthalpy
x Lithium-Bromide concentration
v Specific volume
s Entropy
mls Mass on left side
msr Mass on right side
eshx Effectiveness of solution heat exchanger

Chapter 1
INTRODUCTION

These days world is marked with a rigorous use of energy, cooling and air conditioning remains having the large contribution towards energy consumption. In this context, solar chilled water invention through absorption cycles may be considered one of the most attractive applications to reduce energy utilization and CO2 gas emissions.This study reveal an experimental examination of a solar thermal powered lithium bromide-water absorption refrigeration system1. The absorption refrigeration system consist of condenser, evaporator, absorber, solution heat exchanger and generator.The first loop is form the solar collectorsand the second loop is the absorption’s system loop. The solar energy is gain through the collector and is accumulated in the system. Then the solution in the absorber is given to the generator to boil off water vapor from a solution of lithium bromide-water.The water vapor is cooled down in the condenser by rejecting heat to the air and then passed to the evaporator where it is again evaporated at low pressure, thereby providing air conditioning to the required space. The strong solution leaving the generator to the absorber goes through a heat exchanger in order to preheat the weak solution entering the generator. In the absorber, the strong solution absorbs water vapor out through evaporator. The mixing process of the absorbent and refrigerant vapor generates latent heat of condensation and this heat rejected to atmospheric air23. Vapor absorption system using lithium bromide and water solution has been used widely in large capacity. In such a system, the water is used as a refrigerant and lithium bromide is used as absorbent. It is only used in applications where cooling is required above temperature of 0 degree Celsius. Because of water as a refrigerant, it is not possible to obtain cooling at temperatures below zero. Unlike Ammonia-water system, the analysis of this system is quiet easy because the vapor generated at the generator is composed of pure water.

Overview
Vapor Absorption Refrigeration system consist of four major components evaporator, condenser, generator and absorber. All these components are connected by valves and capillary tubes and pump and we are using solar energy so for that solar collector are used and for operating pump and fans photovoltaic cells are used.

Figure 1: Basic Absorption cycle

Solar energy is required to drive the above system which is collected by solar collectors. In general, low pressure vapors are absorbed by the weak solution in the absorber from evaporator. Then this solution is pumped to the generator and thus increases its pressure. The heat is supplied to the generator to evaporate the water from the lithium bromide and water solution in the form of vapors. These vapors enter into the condenser where heat is removed from the vapors and passed to the evaporator through the capillary tube, by which sudden decrease intemperature and pressure occurs and the whole cycle repeats.
Problem Statement
The project is to design a vapor absorption cooling system which uses solar energy to produce 35.16kW of refrigeration. In absorption cooling system a refrigerant and an absorber are used together. Both refrigerant and absorber combinations can be used that we are using in our project (lithium-bromide and water solution). Project should be totally solar assisted. In VARS we have two options we can either use Lithium bromide and water solution or ammonia water solution. We know that NH3 solution can produce more cooling than LiBr solution but due to its environmental hazards it is avoided in now days. Moreover ammonia based systems have some own design difficulties but major thing is environmentally hazard so avoided.

Project Specifications
Our designed project is off 35.16kW (10 ton of refrigeration) of refrigeration capacity and calculations have been done on the basis of design conditions and mathematical modeling by using software EES. But our designed and manufactured working prototype is of 3.51kw (1 ton of refrigeration) .Our design is totally solar energy based project solar collector is used for heat generation and photovoltaic cells are used for fans and pump operation.
Purpose of the project
The purpose of our project is to design a solar assisted air cooling system so that we use green energy for air cooling because most part of energy produced is used in air conditioning. So, we are going to design a system on small scale. For that purpose we also designed a prototype for such areas where electricity is unavailable and the only source to run this system is by using solar energy which is naturally available abundantly or we can also use it the areas where electricity is available because it does not have any operational cost so it can be used in day timings as for as sunlight available.
Project Applications
The Absorption refrigeration system is mostly used on large scale and it is more attracted than vapor compression system on large scale. Our large buildings or industries mostly use vapor absorption refrigerating system because of its variety of functionality for example we can run this system on hot flue gasses that are emitted by industries or we have solar energy for this purpose or we can burn fuel or natural gas for this. So, there is also a proposed solution that we can use solar and electric cooling system in parallel as for as the sunlight is available we can use solar based chillers or cooling system and mostly this system is required in day times so we can save our money by using this system and it is pollution free.
Vapor absorption refrigerating system is based on heat because it uses heat energy for its operation so that’s why is mostly used in industries, power plants etc because there is much waste energy available in the form of flue gasses or steam or hot water that is rejected to the environment. By using that we can operate cooling system. So, that’s why mostly industries or plants use vapor absorption refrigerating system .4

Chapter 2
LITERATURE REVIEW
Vapor Absorption Cycle invented in 1847 by Ferdinand Carre because he was willing to make ice by using heat energy. In start it was ammonia based. It produces cooling effect by using heat energy and less energy is required and this process is done by using different heat exchangers fans and pump. It is almost the same as VCR cycle but only difference is replace compressor with pump, absorber and generator. It does not have any part to destroy ozone layer. .
The Heat used can be from combustion of fuels like natural gas, waste heat, flue gasses, solar heat etc. Vapor absorption cycle can use variety of fluids for cooling processes typically ammonia or water; lithium-bromide-water; TriDroxide-water; and Alkitrate-water. Tridroxide and Alkitrate are Energy Concepts patented working pairs with specialty applications in industry. Vapor Absorption cycles can be operated at high efficiency by using more advanced cycles.
The vapor compression and absorption refrigerating systems both have almost same working principle both have evaporation, compression, expansion and condensation. These processes are same but the difference is of compressor that does not exist in absorption cooling system and generator and absorber that are present in absorption cycle. Moreover in compression cycle only one refrigerant is used and in absorption cycle two refrigerants are used one is called refrigerant and other is called absorbent. Two types of refrigerants are available in absorption cycle one is LiBr-water solution and the other is ammonia water solution. As we know that ammonia has the ability of cooling below zero or in negative temperature. But its smell is very arrogant and it has environmental hazards so that’s why we didn’t use it. And is also very complicated to design and on the other side LiBr-water solution does not have as such environmental impacts but it can cool up to 0o C.
The refrigerants enter the condenser and after condensation in the condenser then refrigerant enters into evaporator through capillary. The heat absorbed into the evaporator and generates the cooling effect and rejects the heat to the environment through condenser. That’s the basic working principle of the vapor absorption cooling system. The only difference between the vapor compression refrigerating system and vapor absorption refrigeration systems is the process of compression and suction of the refrigerant in the cycle. The compressor draws refrigerant from the evaporator and raise the pressure of refrigerant by compression in the vapor compression system. The compressor also allows the refrigerant to cycle through the whole system. The suction and compression is done by two different components, absorber and generator in vapor absorption cycle. In the vapor absorption cycle, the absorber and the generator are replaced with compressor. The absorbent absorbs the refrigerant and solution is pumped from absorber to the generator by using pump.A major difference between the VCR cycle and VAR cycle is VCR cycle use electrical energy and VAR cycle use heat energy.

Difference between VARS and VCRS
Both are almost same but working principle and some components are different:
Vapor Absorption Refrigerating System:
In vapor absorption cycle the mixture of refrigerant and absorbent both are pumped into generator from absorber and solar collector provides heat into the generator and that evaporates the refrigerant and refrigerant gives its heat to the generator and pass through tube to the evaporator carrying low pressure and temperature and absorb heat at evaporator from the surrounding and because of its low pressure it boils at low temperature and that moved into absorber. That process or cycle repeat itself in same order and rejects its heat to the environment through condenser. The compressor that is used in compression cycle is replaced by absorber, pump and generator and its working is on heat energy.

Vapor Compression Refrigerating system:

In vapor compression cycle Compressor is used. Compressor does the compression of refrigerant and increases its pressure and temperature then it moves to the condenser for condensation that decrease its temperature and after that it passes through expansion valve and because of expansion further temperature and pressure drops and low pressure low temperature working fluid enters into the evaporator and absorbs heat from the surrounding and boils at low temperature because of low pressure and then it again moved to the compressor where again this cycle starts and keep on working. For small scale like in houses and offices vapor compression cycle gets the priority because of its high coefficient of performance .6
Related Studies:
Solar Cooling
Two distinct wayscan be used to produce cooling using solar energy. To convert solar radiation into thermal energy for driving Rankine vapor compression system, an absorption cooler or a desiccant system is most famous way. Solar radiation can be directly converted into electricity by solar cells for driving electric system of cooling units. This method is limited to small application. Present costs of solar cooling systems are high. This shows that solar refrigerating system is achievable for various cities of developing countries. Improvements required to make cooling through solar cooling cost effective are:

Use light weight and inexpensive material for the solar collectors with improvement of thermal efficiency and optical efficiency.
Coefficient of performance can be increased by refining the absorption technology.5

Geothermal Cooling
It has been probablethat the potential assets of high enthalpy geothermal energy, for the production of electricity in Mexico could be larger than 1 EJ yr-1.Mexico has large amounts of geothermal salt-water at temperatures thatare very low to assist electricity to be produced efficiently and less costly. One of the low and medium enthalpy geothermal energy is used to drive an absorption system but selection of enthalpy of geothermal energy depends on better potential to provide cold storage services for consumable food.
Limitations
Both vapor compression and vapor absorption have some its limitations so here are some parameters:
Cost:
VCRS has high operational cost and lower initial cost
VARS has lower operational cost but higher initial cost
Refrigerant Comparison
LiBr is highly corrosive so reduce system life
NH3 is also corrosive but very less as compared to other one
(highly corrosive for copper Cu)
Operating pressure:
VARS has lower operational pressure
VCRS has higher operational pressure
Low Coefficient of Performance:
VCRS has higher COP as compared to VARS( from 7 to 9)
VARS has lower COP as compared to compression cycle (less than 1)

Chapter 3
PROJECT DESIGN
In this chapter we will design the components of the vapor absorption cooling system by mathematical modeling and through simulations. We will use different techniques like mass balance and other designing techniques for heat exchangers design and absorber and generator design. We have to design for 35.16kW or 10 ton of refrigeration for that we are doing calculations of mass flow rates and evaporator design and condenser design software tool that we are using is EES (Engineering Equation Solver). COP of the system would be measured and effect of different parameters on the coefficient of performance would be measured by using the refrigerant LiBr and water solution .7
Design and Analysis of Components
The major components of the project are evaporator, absorber, generator, condenser and solar collector. All of the components has been designed according to their standards area for generator and absorber and length of tubes and radius of tubes have be calculated and effected area for solar collector and focal point of solar collector have be calculated. Numerical techniques and software results are used for design and both results matched to check both results.8

Figure 2: Vapor Absorption Cycle
.
Comparison of the on basis of Desirable Properties
Solution of any absorption system consist of two main liquids.
Refrigerant
Absorbent
Absorbent and refrigerant mix together to form a complete solution. Refrigerant circulate into the whole cycle but Absorbent move between two component which is absorber and generator. Main purpose of the Absorbent to help the refrigerant to pump from absorber to generator, so refrigerant should be unique physical properties as compare to absorbent. Boiling point of refrigerant should be less as compare to absorbent which help to evaporate the refrigerant from absorbent. We can say that refrigerant should be more volatile than absorbent. In this way pure refrigerant would move to condenser from generator and then goes toward evaporator. Second property of refrigerant is it should be more soluble to the absorbent and pump can easily pump the solution to the generator. Pressure adjust in such a way to avoid the crystallization which would cause the blockage of tubes. Other properties of mixture should be less toxic, chemically stable, inexpensive and non-corrosive. Refrigerant must contain high heat of vaporization.
The two types of Vapor Absorption air conditioning systems are present.
Lithium bromide-water solution
Ammonia-water solution

Lithium bromide-water solution system:
In this system of refrigeration solution contains mixture of lithium bromide and water .Lithium bromide work as Absorbent and water work as refrigerant in this system. In the absorber water engrosses the lithium bromide absorbent, creating a solution of lithium bromide and water. After that increase the pressure of this solution with the help of pump and enter this solution into the generator where heat is supplied to the solution. The refrigerant absorbed heat from heat source then evaporate and passes through the condenser. Lithium bromide from generator go back to the absorber where it absorb water which is coming from evaporator and ready to pump again. Lithium bromide water vapor absorption cycle used in different application. This system is more suitable for where temperature needed more than 32 F.9

Advantages:

In the lithium bromide water solution system rectifier is not required.
In lithium bromide water solution system refrigerant has greater heat of vaporization.
Working pressure of this solution is less as compare to ammonia water solution.

Disadvantages:

Crystallization of solution will formed if we use high concentration of the solution.
Coefficient of performance of this solution is low as compare to ammonia water solution.
Corrosive nature of the lithium bromide damage the heat exchanger.
Crystal formation, leakage of air and drops in pressure are also problems using this solution.
Mathematical Modeling
Mathematical model of our project is given in this section. We model two system one system have capacity for 35.2 KW and second system have capacity of 2.64 KW. First of all we will move toward operating conditions.

Operating conditions for lithium bromide water system:
There is different operating condition for different system, so operating conditions for lithium bromide water system is tabulated as.

Components Temperature ? Pressure (kpa)
Generator 100 7.38
Condenser 37 7.38
Absorber 27 1.23
Evaporator 10 1.23
Table 2: Operating conditions for (libr-H2O) system
Above table is telling us about temperature of different units of lithium bromide water system which would be more helpful during the design of condenser and evaporator.
Block diagram is best way to understand the any process in detail so we are using same techniques for the understanding of flow of lithium bromide and water system. Block diagram of lithium bromide water system is given below

Figure 4: Block diagram for lithium bromide water system.
Above diagram giving knowledge about different components ammonia water system and flow of refrigerant through different components.11
Calculation of lithium bromide water system:
This calculation is for the system who have capacity of 35.2KW. On the base of above block diagram we mention number of each component and that number would be in subscript of each property.
Mass flow rate of pump:
W1 = mass flow rate from Pump to Generator.
W2 = mass flow rate from Generator to Absorber.
W3 = mass flow rate from Generator to Condenser.
W4 = mass flow rate from Condenser to Evaporator.
W5 = mass flow rate from Evaporator to Absorber.

Mass flow rate delivered by the pump = w_1 = 0.06 kg/s

Total mass flow balance at generator:
w_2 + w_3 = w_1 = 0.06 kg/s
w_1 x_1= w_2 x_2
The solution leaving the component is the representative of the solution in the component, so the state point of the solution at point 2 leaving the generator is found from graph/figure-3 at intersection of solution temperature of 100? and pressure of 7.38 kPa. Which is
x_2= 0.664
Similarly at absorber the solution leaving at 27? and pressure of 1.23 kPa
x_1 = 50

Mass balance Equations:

(0.06)(0.5) = w_2(0.664)
w_2 = 0.045 kg/s
w_3 = w_1-w_2 = 0.06 – 0.045

w_3= 0.0148
w_3=w_4=w_5=0.0148 (since there is no pump between generator, condenser and evaporator before absorber)

Enthalpies of different point:

Enthalpies of solution can be found from the figure-5:
h_1= enthalpy at 27? and x of 50% = -172 kJ/kg
h_2= enthalpy at 100? and x of 66.4% = -52 kJ/kg

Enthalpies of water, liquid and vapor are found from the property table for water as

h_3 = 2676 kJ/kg
h_4 = 167.5 kJ/kg
h_5 =2512 kJ/kg

Rate of heat transfer for Evaporator:

Q_E= w_5 h_5 – w_4 h_4 = 0.0148(2512-167.5)
Q_E=35 kW = 10 tons approx.

Rate of heat transfer for condenser:

Q_G = w_3 h_3 + w_2 h_2 – w_1 h_1
=0.0148(2676) + (0.045) (-52) – (0.06) (-172)
= 47.58 kW

Rate of heat transfer for Generator:

Q_A = w_2 h_2 + w_5 h_5 – w_1 h_1
= (0.045) (-52) + (0.0148) (2520) – (0.06) (-172)
=45.276 kW

Rate of heat transfer for Absorber:

Q_C = w_3 h_3 – w_4 h_4
= (0.0148) (2676) – (0.0148) (155.035)
=37.30 kW

Coefficient of performance:

COP= Q_E/Q_G = 35/47.58

COP = 0.73

Graphs:
Graph that is used in our above calculations are given below.

Figure 5: Use for percentage concentration lithium bromide in solution.

In above graph wecan find concentration of lithium bromide in the solution with help of known vapor pressure and saturation temperature of pure water. When we have find concentration of lithium bromide automatically we can find concentration of water.
This graph also help out to find other unknown. We can find vapor pressure, crystallization temperature, solution Temperature and saturation temperature of pure water. Let’s suppose we need to find the concentration of lithium bromide in solution percentage by mass. Known values for this calculation are 7.38KPa vapor pressure, 40 Celsius is the saturation temperature of pure water and 80 Celsius is the temperature of the solution. Corresponding to these values the concentration of lithium bromide in solution is 59.60 % by mass.

Figure 6: For enthalpies calculation.
This graph is same as above but difference is its y-axis contain enthalpies while in previous graph it was saturation temperature of pure water. Using this we can find the enthalpy of solution because we know the concentration of lithium bromide from the previous graph and we know about solution temperature so we can easily find the enthalpy of the solution.12
Calculation of lithium bromide water system on EES:
This section of the report is related to calculation of the lithium bromide water system with capacity of 2.64 KW. Our prototype calculation is based on this section of report. We use Engineering equation solver (EES) to reduce calculation of the system with capacity of 35.2 kW to the system having a capacity of 2.64kw.

Calculation for mas flow rates on EES:
W1 = mass flow rate from Pump to Generator.
W2 = mass flow rate from Generator to Absorber.
W3 = mass flow rate from Generator to Condenser.
W4 = mass flow rate from Condenser to Evaporator.
W5 = mass flow rate from Evaporator to Absorber.
These all point on the base of figure 3 which is given before.
This tab shows the equation which we have written in engineering equation solver
W1 = 0.005KG/S
“W1 = mass flow rate at point 1”
W1*X1 = W2*X2
“W2 = mass flow rate at point 2”
“X1 and X2 are concentration at point 1 and point 2”
X1 = 0.50
X2 = 0.664
“W2, W3, W4 are mass flow rates at point 3, 4 and 5”
W3=W1 – W2
W3 = W4
W4 = W5

The results EES calculation are following:
W1=0.005 kg/s
W2=0.003765 kg/s
W3=0.001235 kg/s
W4=0.001235 kg/s
W5=0.001235kg/s

Calculation for Condenser Design:
For the design of condenser we need to calculate its area and then calculate the length of tube which is used in condenser. We did this calculation on engineering equation solver (EES).we use NTU method for the design of condenser.
Density = 1.16 m3/kg
Cpc = 1.007
Cph = 4.178
Tci = 25oC
Thi = 40oC
Tho = 40oC
Wc=0.001235kg/s
Qc = 3.117kW
Tco = Tci + qe / (mc*Cpc)
Cmin=mc*Cpc
Qmax=Cmin*(Thi-Tci)
?=0.98
NTU = -ln (1-?)
U=0.026
Area = (NTU*Cmin)/U
r = 0.0072 m
L = (Area-(6.28*r2))/3.14*r

Result of above equations are taken from the EES to show that the results of above given equationwith SI units setting
Area=0.1871m2, Cmin=0.001244, Cpc=1.007,Cph=4.178,
Density=1.16kg/m3, L=8.262m, NTU=3.912, qc=3.117kW,
Qmax=0.01865kW,r=0.0072m, Tci=25oCTco=31oC,
Thi=40oC, Tho=40oC, U=0.026,Wc=0.001235kg/s, X=0.98

Calculation for Evaporator Design:
This calculation is for the design of evaporator and we use same technique and method as we use in condenser design.
Density= 1.16 m3/kg
Cpc= 1.007
Cph = 4.178
Tci = 25oC
Thi = 40oC
Tho= 40oC
“mc=me”
mc=0.001235kg/s
Qe = 2.892kW
Tco = Tci + qe / (me*Cpc)
Cmin=mc*Cpc
Qmax=Cmin*(Thi-Tci)
?=0.85
NTU = -ln (1-?)
U=0.026
Area = (NTU*Cmin)/U
r = 0.006 m
L = (Area-(6.28*r2))/3.14*r
Results of above equation that we have written in EES aregiven below with SI units setting clearly which are
Area=0.09074m2,Cmin =0.001244,Cpc =1.007,Cph =4178, Density=1.16 kg/m3
L=4.805m,Wc=0.001235 kg/s, NTU=1.897, qe=2.892 kW, qmax=0.01865 kW
r=0.006m, Tci=25oC, Tco=23oC, Thi=40oC, Tho=40oC, U=0.026, X=0.85

Calculation for Generator:
For the calculation of the generator first we calculate the volume of the generator then we make box of with copper plate of same volume. Similarly we can find the volume of absorber. We use copper material for this purpose because it have high conductivity.

Specific volume = (mass flow rate)/density

?=m/?
?=0.005/2225.08
?=2.25×?10?^(-6) m^3/min

Calculation for DC Pump:
For the selection of the pump we need our required parameters i.e. the maximum head required at which we have to pump the solution, maximum pressure, flow rate and the power required.
Designed Parameters
NPSHR = 1.524m
Mass flow rate = 0.005kg/s
Pressure = 7.38kPa
Selected Pump Specifications
Maximum head = 5m
Max. flow rate = 0.22kg/s
Pressure = 110kPa

Calculation for solar panel
The solar panel is selected on the basis of the power consumed, we have calculated the power consumed by each component in our project then compared the suitable solar panel for our system. The calculation of power load are following:

Equipment
Quantity
Load/unit
(W)
Total Load
(W)

Absorber and Condenser Fan 2 25 50
Evaporator Fan 1 50 50

DC Pump 1 35 35

Total 135

Calculation for Coefficient of Performance:
For the coefficient of performance use same method of EES so it’s equations are given below.
W1=0.005kg/s
W2=0.003765kg/s
W3=W1-W2
W3=W4
W4=W5
h1=-168KJ/kg
h2=-38KJ/kg
h3=2691.3KJ/kg
h4=167.5KJ/kg
h5=2509.7KJ/kg
“h1,h2,h3,h4 and h5 are enthalpies at representative points”
Qe = W5*(h5-h4)
Qg = W3*h3+W2*h2-W1*h1
Qc = (W3*h3)-(W4*h4)
Qa = (W2*h2)+(W5*h5)-(W1*h1)
COP = Q_e/Q_g
Results of above equations are
COP=0.7194, h1=-168 kJ/kg, h2=-38 kJ/kg, h3=2691 kJ/kg
h4=167.5 kJ/kg, h5=2510 kJ/kg,qa=3.796 kW,qc=3.117 kW
qe=2.893 kW,qg=4.021kW, W1=0.005kg/s, W2=0.003765kg/s
W3=0.001235kg/s, W4=0.001235kg/s, W5=0.001235kg/s

Effect of Generator temperature on COP:
We observed the Effect of temperature of the generator on coefficient of performance (COP). Coefficient of performance increase with increase of generator temperature.13
EES Equations:
W1=0.005Kg/s
W2=0.003765Kg/s
W3=W1-W2
W3=W4
W4=W5
Cp=1007
h1=-168KJ/kg
h2=-38KJ/kg
h3=2691.3KJ/kg
h4=167.5KJ/kg
h5=2509.7KJ/kg
h1=Cp*T1
h2=Cp*T2
h3=Cp*T3
h4=Cp*T4
h5=Cp*T5
“Te=T5-T4″
Tg=T1-T2-T3”
Qe = W5*Cp*Te
Qg = W3*Cp*Tg
Qc = (W3*Cp*T3)-(W4*Cp*T4)
Qa = (W2*Cp*T2)+(W5*Cp*T5)-(W1*Cp*T1)
COP = Q_e/Q_g

Above equation is for observing the effect of change in generator temperature on coefficient of performance.
Then we run iteration for COP with different ranges of evaporative temperature and generator temperature.

Table 3: Effect of temperature on COP

Figure 7: Effect of generator temperature on COP

Figure 8: Effect of evaporator temperature on COP

Pump Selection:
Volumetric Flow rate =Q ? = 2.26534773 x 10-6 m3/s
NPSHR = 0.9144m
Mass flow rate = m ? = 0.005kg/s
Temperature = 24.4 o C
Pressure = 101.352kPa
Diameter = 0.0635m
P_v= 3.10kPa @ 25o C
?_1=0.042 @ 25o C
Q ?= AV
Velocity = V =Q ?/(?/4 d^2 ) = (2.26534773 x 10-6 )/(?/4 ?(0.0635)?^2 )
V = 2.45 m/s
NPSHA= P_atm/? – z_1 – P_v/?
(z_1 )_max = P_atm/?- P_v/? – NPSHA_R
(z_1 )_max = 10.48 – 0.32 – 2.43 = 7.62m
As NPSHA > NPSHR so pump will work.
Now work of the pump is to be calculated as:
W_p= ?_1 (P_2- P_1) / ? = 0.042 x (0.748-0.123) / 0.70

Results:
From the above calculation we conclude that which factor effect the COP.All the components of absorption cooling system including the absorber, evaporator, condenser and generator greatly affect the cycle coefficient of performance. We have observed these results through calculation of cop. The temperature also affect the Coefficient of performance COP.
We can make changes to make system efficient, also can save the money or material using effective ways. We have been study that there are many factors that are needed for making effective system. We will use these effective way to fabricate the system.5

Chapter 4
TOOLS AND TECHNIQUES
Hardware and Analyzing Tools

Solar Collector:
Solar collector is a component that absorbs the radiations of the sun and converts into heat energy in a useful manner to get desired output. Solar collector is of different type’s flat plate solar collector, parabolic solar collector, line focused and evacuated tube solar collectors but in our case we used parabolic solar collector (dish type) to focus all the sun rays on its focal point a shining surface is obtained by chrome plating and from calculations we find out the effective area required and its focal point. Sun rays focused on a point and at that point we placed in such a manner that it directly on generator and that side of generator copper plates are welded because copper is a good conductor So, maximum heat transferred through that area.
Photovoltaic Cells:
In our project we used fans to for evaporator and condenser and a pump is used to pump the fluid into generator we calculated the total power required for operating fans and pump and according to that requirement we needed a PVC of 140 Watt but tha available in market was of 150Watt so we used that.
Generator:
Generator is component of VARS that is of box shaped and it contains strong solution of refrigerant and absorbent that is connected through a pump to the absorber and heat generated from solar collector evaporates the strong solution containing refrigerant and that moves into evaporator. It is made of plates that we used copper plates and plates are welded
Absorber:
Absorber is a box that is quite similar the generator and it contains the weak solution coming from the generator and it consist of LiBr and water solution with equal concentration and water vapors coming from evaporater that are called boiled refrigerant enter into absorber that make strong solution after mixing with that solution and heat is rejected to the surrounding and for that purpose fins are attached to th walls of absorber for more cooling and after that this mixture is pumped into generator through the pump.

Evaporator:
Evaporator is a heat exchanger that we are using flat plate fins. Refrigerant enters into the heat exchanger with low pressure and low boiling point. Heat is absorbed through the surrounding and that heat causes the refrigerant to boil and that’s how cooling phenomena occur. Evaporator is air cooled so a fan is attached on the backside of the evaporator. By experimentation we noted that a change of 10o C to the surrounding temperature. It can produce more cooling with the time because by using solar energy it takes more time to cool.
Condenser:
Condenser is a component or heat exchanger that is used to reject the heat to environment. It removes the heat from the coolant. In our prototype we used air cooled heat exchanger with flat plate fins. Different designs can be made according to the requirement and design specifications.
Pump:
Pump is device which is used to increase the pressure of the solution. It help to move the solution from absorber to generator. Generator is placed at elevated pressure we have to use device which help the solution to move from low pressure absorber to high pressure vapor, so the suitable device is pump. Pump increase the pressure up to 10 bar.14
Simulation tools:
We used Engineering Equation solver (EES) as a simulation tool in our project. All calculations have been done by using this tool.
Engineering Equation solver (EES):
Engineering equation solver is the software which is used for the solution of nonlinear equation. This is the main tool for the solution of the heat transfer and thermodynamics problem and it is widely used tool in mechanical engineering. Many thermodynamics properties are built in EES which help in solving thermodynamics equation. We can also compare different variable in short time using parametric table which is also help in plotting. We can also solve integration through this engineering tool. This tool is very easy to use user can save his data in and accesses that data later with their codes. User can put input equation in any form EES give him solution it’s user friendly software. So, we done all simulations through this software codes and results are attached to the report.
Summary:
In this chapter we discussed about the simulation tools we used and major hardware components that we used in our project. We used EES as simulation tool and solar collector, PV cells, evaporator, condenser, generator, absorber are some hardware components that we used.
Chapter 5
Results and Evaluation
We have designed a 35.16kW VAR system for that we have done calculations and on the basis of our design we have made a system and to observe our result we made a prototype on small scale of 3.51kW and on the basis of our design we made that model and we achieved the success criteria of our project. Because we had to show the sensible cooling effect during our experimentation process we have measured a temperature change of 10o C and according to our success criteria that’s more than enough.
Results and findings:
We will explain the results and findings of our project:
Results:
Major parts of my project is solar collector, absorber, generator, condenser, evaporator, pump and photovoltaic cells. Absorber would contain solution of the lithium bromide and water which is then pumped to the generator.

Figure 9: Absorber
Above is the figure of absorber with fins. We used fin to increase the surface area of the absorber for the heat transfer. Material of the fin is copper which is attached through the process of brazing. In local language they call it kali it’s the same process which is use for the radiator fins.
Second part of the our project is generator I already told you in previous chapter about the function of the generator but in this chapter I will explain you about the results and finding of the generator so it’s figure given below.

Figure 10: Generator
Materail for the generator is mild steel and copper. Material for the Base plate of the generator is copper and rest of the body is made up of mild steel.

Figure 11: Evaporator
Above figure is for evaporator its working already describe in previous chapters. We design this evaporator with its area and length of the tube and bend of the tube.
Figure 12: DC Pump
We are using solar panel that’s why we need DC pump for project. This pump is according to our desired flow rate we purchased this from the market on basis of pump selection calculation.

Figure 13: condenser
Condenser is also an important component of vapor absorption system. We design this condenser on the base of its frame area and its total tube length. This is a type of air cooled condenser.

Software results:
We did All calculation using Engineering equation solver. Important thing was how to design condenser and evaporator so the results of evaporator and condenser on EES given below.
Evaporator:

We are showing you final results of engineering equation solver (EES). Detail calculation already explain in previous chapters.

Length 0.43 m
Height 0.23 m
Width 0.041 m
Length of the tube 5.72 m
Number of bends 13
Table 4: Final results of Evaporator

This is the final result for the design of evaporator on the base of engineering equation solver. All measurements are in inches so we can convert it into any unit according to our desired units.
Condenser:

We are showing you final results of engineering equation solver (EES). Detail calculation already explain in previous chapters.

Length 0.53 m
Height 0.36 m
Width 0.036 m
Length of the tube 8.64 m
Number of bends 16
Table 5: Final results for condenser
This is the final result for the design of evaporator on the base of engineering equation solver. All measurements are in inches so we can convert it into any unit according to our desired units. For other units like generator and absorber we have calculate their volumes which is 13.5 cm3. Then we make boxes on the base of calculated volume.15

Discussion of the findings:
This is the vapor absorption system exist in the world the basic principle is same but we are manufacturing prototype on small scale by using solar energy as source. Before this there is only theory about this we convert that theory into the practical work. But at small level no heat exchangers available for that we have manufacture it from locally available welders that’s why we could not get our desired results and heat exchanger specially evaporator and condenser we could not get according to our design because it’s not locally available and manufacturers ask for so much money so we had to stick with the available options. It can be improved we every thing is available according to design.

Limitations:
Because total project is solar operated project so sunlight is one of the main limitation of this project . In the absence of sunlight hot or flue gasses that we say industrial waste can be used but in homes we can burn natural gas but that can be costly but not as compared to electricity we use.
Recommendations:
There are further changes and improvements that can be made in our project. If someone is willing of doing this project then they should design a voltage controller because we used direct current from PVC to pump and fans as a result we had to change pump or fans because of sudden voltage drop and rise and a heat exchanger can be used between absorber and generator. Heat source other than solar can also be used or if solar collector has to be used than evacuated tubes are the best option because that has the maximum efficiency among all type of solar collectors and after that line concentrated solar collectors are the second best option. But we used parabolic because of cost effective and easy manufacturing.

Summary:
So, here is our complete working model that’s a prototype of actual design our prototype has very very small deviation from the actual theoretical results but that can be ignored because the manufacturing like welding etc is not upto the standards. So because of locally manufacturing these deviations are not so alarming. But our working model is showing sensible cooling effect of 10o C and that was actually our success criteria.

Figure 14: Manufactured Model

Chapter 6
Conclusion
We are in learning stage as a student. Because it was the time when we have to implement our knowledge that we learnt in a classroom and labs and in workshops we done. But at start we were unaware of the practical life we didn’t had the idea that how to start it. Actually we got panic but than our Supervisor Dr. Saif Ur Rehman helped us and ask us to start without any fear of failure. Because, failure is the best way to learn . In start we failed a lot of time but eventually we have achieved our goal. Although we failed a lot of time, we had to change the components and our design but we didn’t lose hope and at last we achieved our goal and we have made the working model. We learned a lot from this project. We got the exposure to the practical life where we can’t make a single mistake. So, this experience will help us all of our life.
We must say it is the result of combine effort of supervisor Dr. Saif ur Rehman who helped us in our each failure and suggest a new way to solve this problem and all group members, we worked very hard and that’s how we achieve our goal. Because hard work is the only key to success.

References
1 R. E. Critoph and K. Thompson, “Solar energy for cooling and refrigeration,” EC BREC/WREN Proc. Eur. Semin. ‘Renewable Energy – A Strateg. Sustain. Dev. IBMER, Warsaw, 17-19th November, 1997, pp. 47–57, 1997.
2 S. A. M. Said et al., “Design, construction and operation of a solar powered ammonia-water absorption refrigeration system in Saudi Arabia,” Int. J. Refrig., vol. 62, pp. 222–231, 2016.
3 F. Boudéhenn, H. Demasles, J. Wyttenbach, X. Jobard, D. Chèze, and P. Papillon, “Development of a 5 kW cooling capacity ammonia-water absorption chiller for solar cooling applications,” Energy Procedia, vol. 30, pp. 35–43, 2012.
4 R. GOMRI, “Solar energy to drive absorption cooling systems suitable for small building applications,” 2010.
5 C. Robbins, “Solar Cooling Technology Review.”
6 Z. . Li and K. Sumathy, “Technology development in the solar absorption air-conditioning systems,” Renew. Sustain. Energy Rev., vol. 4, no. 3, pp. 267–293, 2000.
7 P. N. Ananthanarayanan, Basic Refrigeration and Air Conditioning. Tata McGraw-Hill Publishing Company Limited.
8 N. K. Sharma and D. Gaur, “Design& Analysis Of Solar Vapour Absorption System Using Water And Lithium Bromide,” Int. J. Eng. Res. Technol., vol. 2, no. 6, pp. 2599–2610, 2013.
9 J. Chakraborty and V. K. Bajpai, “A Review Paper On Solar Energy Opearted Vapour Absorption System Using Libr-H 2 o,” vol. 2, no. 8, pp. 5–7, 2013.
10 G. Q. S.B. Riffat, “‘Comparative investigation of vapour compression and vapour absorption airconditioners,'” Appl. Therm. Eng., vol. Vol. 24, p. pp 1979-1993, 2004.
11 Z. Q. X. R.Z. Wang, T.S. Ge, C.J. Chen, Q. Ma, “”Solar absorption cooling systems for residential applications: options ; guidelines”,” Int. J. Refrig., vol. Vol.32, p. pp 638-660, 2009.
12 S. Kaushik and S. Singh, “Thermodynamic Analysis of Vapor Absorption Refrigeration System and Calculation of COP,” I Jraset, vol. 2, no. 2, pp. 73–80, 2014.
13 G. Hernández, J.A., Rivera, W., Colorado, D., Moreno-Quintanar, “Optimal COP prediction of a solar intermittent refrigeration system for ice production by means of direct and inverse artificial neural networks.,” Sol. Energy 86, pp. 1108–1117, 2012.
14 Carrier, “Lithium Bromide Absorption Chiller 16JL(R),” p. 20.
15 D. Of and M. Engineerin, “LECTURE-18 Vapour Absorption Refrigeration System.”