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1、Air Conditioning using Air Conditioning using Waste HeatWaste Heat（余热）and Solar Energy with and Solar Energy with Phase Change MaterialsPhase Change Materials 1唐小媛唐小媛201253762AbstractEnergy is an important phenomenon in todays hectic world.A lot of researchers are doing research in this field due to
2、 its wide importance and also due to the scarcity of sources of energy in modern world,which in turn needs new inventions and discoveries to satisfy the demands of this scientific world.Research works are done to examine different sources of energy and also to reduce its wastage.Reducing the wastage
3、 and utilizing the energy completely depicts the overall efficiency of any system.In todays modern world,air conditioning plays a major role due to the rapid increase in the earths temperature and therefore,people long for comfort cooling.Nowadays,a lot of energy is wasted in the form of heat which
4、eventually reduces the overall efficiency of any system.Therefore a system should be designed which shows a maximum efficiency by reducing its wastage to a very minimal amount.Complete utilization of both solar heat and waste heat is achieved using Phase Change Materials.Phase Change Materials are t
5、he materials,which is of greater thermal storage capacity.3Simulation contentvA：The methodology of providing air conditioningvB：The basic components of vapour absorption systemvC：Relevant calculationsvD：Results and Discussion41.IntroductionNowadays,people long for comfort cooling due to changes taki
6、ng place in the climate.Most of the people prefer air conditioning systems for comfort cooling.Several scientists worked on the advancements of the air conditioning systems and published their research works.W.B.Gosney 8 described the basic principle of refrigeration and also explained about the var
7、ious factor involved in the vapour absorption system in 1982.P.S.Asha Iyer 9 explained the thermo economic theory which is applied to the economic optimization of a single effect water/LiBr vapour absorption refrigeration system for air conditioning application.He aimed at minimizing its overall ope
8、ration and amortization cost.S.Iyoki 6 investigated the coefficient of performance was undertaken to examine the performance characteristics of the water-lithium bromide-zinc chloride-calcium bromide system(1.0:1.0:0.13 by mass,respectively)in 1990.1.Introduction5Vicatos 1 selected the operating con
9、ditions for existing systems and achievingautomatic control for maintaining optimum operation of the systemsin1995.S.Aphornratana 11studied the second law(of thermodynamics)method as applied to a single-effect absorption refrigeratorcycle in 1995.S.M Deng 2 discovered the absorber is an important co
10、mponent in absorption machines and its characteristics have significant effect on the overall efficiency of absorption machines in 1999.J.R.Khan 7 summarized the characteristic performance curves of vapour-compression refrigerationsystems are defined as a plot between the inverse coefficient of perf
11、ormance(1/COP)and inverse cooling capacity(1/)of the system in 1999.M.Talbi 12 used the thermodynamic processes in the absorption refrigeration system which releases a large amount of heat to the environment in 2000.Khalid A.Joudi 3explained steady state computer simulation model has been developed
12、to predict the performance of an absorption refrigeration system using LiBrH2O as a working pair in 2001.1.Introduction6D.Hudson 10 confabulatedthe majority of absorption cycles are based on water/lithium bromide cycle and many applications exist where ammonia/water can be used,especially where lowe
13、r temperatures are desirable in 2002.Antonio De Lucas 4 investigated and studied the addition of a surfactant like n-octanol improves the absorption capacity of the absorbent solutions employed in absorption refrigeration coolers in 2007.Xiaolin Wang 5 explained the Lithium bromide-water absorption
14、cooling technologies is underpinned by the continual circulation of water,which is the refrigerant,powered by the hygroscopic nature of aqueous lithium bromide solution in 2009.Therefore,our research paper concentrates on both the usage of Phase Change Materials and Vapour Absorption System in air c
15、onditioners.There are various sources in which waste heat is released and the corresponding waste heat is used as an input to our air conditioning system which in between packed with Phase Change Materials that absorbs heat periodically.Hence,when the Phase Change Material attains its melting point,
16、it gives heat to our air conditioning unit along with the solar heat and therefore it could work even when the machines releasing waste heat are in ideal conditions.7Nomenclaturehc out Outlet enthalpy of refrigerant which is coming out of condenser(kJ/kg)Tc Condenser temperature(C)he out Outlet enth
17、alpy of refrigerant which is coming out of evaporator(kJ/kg)Te Evaporator temperature(C)Xss Concentration of strong solutionXws Concentration of weak solutionTg Generator Temperature(C)Ta Absorber Temperature(C)Mr Mass flow rate of Refrigerant(kg/s)Mss Mass flow rate of strong solution(kg/s)Mxs Mass
18、 flow rate of weak solution(kg/s)E Solar Collector EfficiencyH Average solar heat falling on the earth surface(5.5 kWh/m2/day=230W/m2)A Area of Collector Plates(m2)2.Methodology8Vapour absorption system is one of the oldest method of providing air conditioning and refrigeration which operates with t
19、he input of heat.The basic components of vapour absorption system are same as that of compression system where compressor is replaced by absorber.The main parameters of vapour absorption system are condenser pressure,evaporator pressure,generator temperature and absorber temperature.The other parame
20、ters are fixed with respect to the main parameter.Fig.1.2.Methodology9Fig.1.Overall system of Air Conditioning using Waste heat and Solar Energy102.1.CondenserThe pressure of the condenser is very vital which depends upon the refrigerants used in the absorption system.Water ammonia vapour absorption
21、 system is used and so water is used as a condensing medium.The pressure is maintained for changing ammonia vapour into ammonia liquid which also relies upon the type of condensing medium used.For condensing ammonia vapour at condenser temperature,corresponding pressure is chosen in refrigeration ta
22、ble.The outlet enthalpy of refrigerant which is coming out of condenser must be known for calculating mass flow rate of refrigerant.hc out=(Tc-25)*4.187112.2.EvaporatorThe evaporator pressure is also equally important as that of condenser pressure because it decides the minimum temperature of the ro
23、om to be cooled.In order to avoid high pressure maintenance and leakage problem,the pressure of evaporator is chosen moreover equal to atmospheric pressure.The design of evaporator is in such a way to absorb heat effectively and efficaciously.Mass of flow rate of ammonia is increasingly important to
24、 increase the effective heat transfer.The enthalpy of refrigerant which is coming out of evaporator has to be calculated in order to calculate the mass flow rate of refrigerant.he out=(572.8+0.417 Te)*4.187122.3.AbsorberIn absorber,mixing of pure NH3 vapour and weak aqua solution happens.The process
25、 speed is inversely proportional to the high temperature and the process itself is an exothermic process.So it isinevitable to get rid of the heat generated in the absorber and it catalyses the process.Because of this reason,cooling water is provided to the absorber.Next to the absorber,there is a p
26、ump to accelerate the mixture to the generator through the regenerator.Regenerator is more or like heat exchanger which exchanges the heat from weak solution to mixture.There are many important parameters to be considered in the absorber which are concentration of weak and strong solution and the ma
27、ss flow rates of weak and strong solution.All the parameters are calculated in the calculation part14.132.4.GeneratorIn generator,heat is supplied to the strong aqua solution.Due to the input of heat,pure ammonia vapour gets escaped from generator but still has some amount of water vapour.Rectifier
28、is placed next to the generator to screen the escaped water vapour from ammonia vapour.The phase change materials are placed prior to the generator which has both inputs.Waste heat from industries is one of the inputs and the other one is solar panels.Heat required at generator is achieved by both w
29、aste heat and heat from solar panels and heat calculations are performed.This process is clearly shown in the figure1143.CalculationsTable 1.Temperatures of all parametersParameters Temperature(C)Generator 100Condenser 40Absorber 35Evaporator 10153.1.Concentration of strong solution:Xss=(49.04+1.25
30、Tg-Tc)/(134.65+0.47 Tg)=0.6523.2.Concentration of weak solution:Xws=(49.04+1.25 Ta-Te)/(134.65+0.47 Ta)=0.543.3.Mass flow rate of refrigerant:Enthalpy of refrigerant which is coming out of evaporator he out=2892.42 kJ/kgEnthalpy of refrigerant which is coming out of condenser,hcout=1205.856 kJ/kgMr=
31、Qe/(he out-hc out)=1.037 gm/s163.4.Mass flow rate of strong solution:Mss=Mr*(Xws/(Xss-Xws)Mss=5.09 gm/s3.5.Mass flow rate of weak solution:Mws=Mr*(Xss/(Xss-Xws)=6.127 gm/s3.6.Heat required at Generator:Heat load required to run 1 ton AC=5kW=300 kJ/minOf these approximately 150kJ/min is given from wa
32、ste heat in the industry which may vary.Let us take to the minimum of 100kJ/min from waste heatThe remaining 200kJ/s is given by the solar panels.173.7.Calculations of Solar Panels:Energy absorbed by the solar Collector13 is given byQa=E*H*AHeat required in the generator by solar panels=200kJ/min=(2
33、00*1000)/60 W=3330 WHence Area of Solar panels=3330/(230*0.87)=17 sq mArea of Solar panels=17 sq mTherefore,3 collector plates of dimensions 2.8*2 sq m are neededThus,Qa=0.87*230*16.8Heat Generated in the solar Panels=3360W183.8.Calculation for Phase Change Materials:Phase change materials are insta
34、lled for the backup time of 1 hourHeat load to run 1 ton AC=5kWSo,Heat required for 1 hour=18000kJLatent heat of PCM=200kJ/kgMass of PCM=Heat required/Latent Heat=18000/200=90 kgMass of PCM needed for 1 hour backup time=90 kgWe can also extend the backup time for air conditioning3.9.COP of Refrigera
35、tion:COP=Refrigeration Effect/Heat input in the generatorCOP=211/300COP=0.74.Results and Discussion19Vapour absorption system is designed using phase change materials and solar panels and the various parameters are compared with COP calculated with respective temperatures.The figure2 shows that the
36、Coefficient of Performance increases with the increase in generator temperature.The figure3 reveals that the Coefficient of Performance decreases with the increase in condenser temperature.The figure4 explains that the Coefficient of Performance increases with the increase in evaporator temperature4
37、.Results and Discussion20Fig.2.(a)Generator Temperature vs.COP 4.Results and Discussion21Fig.2.(b)Condenser Temperature vs.COP4.Results and Discussion22Fig.3.Evaporator Temperature vs.COP5.Conclusion23The theoretical design of vapour absorption system is designed and back up of operation up to 1 hou
38、rwithout heat input is also designed.Mass of phase change and heat load for operating the system is also calculated.The heat which is emitted as waste in industry is effectively used by the system and it runs the vapour absorption system.It acts as a multipurpose one because it absorbs the waste hea
39、t and it also runs the vapour absorption system.The backup time of PCM helps to run the system uninterruptedly.This system reduces the usage of power to a great extent thereby saving energy.With the increasing demand of Air conditioning systems,this system would give a better replacement with better efficiency and reduced cost.24Thanks!Thanks!