DESIGN & DEVELOPMENT OF COMBINED UNIT FOR AN AIR CONDITIONING & REFRIGERATION AND SIMULATION OF SYSTEM

Transcription

1 ESIGN & EVELOPMENT OF COMBINE UNIT FOR AN AIR CONITIONING & REFRIGERATION AN SIMULATION OF SYSTEM Arif O. Hannure 1, Avinash M. Patil 2 1 PG Student PVPIT, Budhgaon, Sangli. (India) 2 Vice Principal of PVPIT, Budhgaon, Sangli. (India) ABSTRACT For any industrial and residential application, we require different teperature for different application, for exaple in office application one refrigeration syste require at low teperature for chiiling product atediu teperature, whereas one ore syste ay require, which has soewhat higher teperatures copare to other for huan cofort.to obtain such different teperature by noral single refrigeration syste is very difficult, as teperature requireent is different for different application but basic operation of cycle is sae so, to follow econoy, low initial cost, and operating cost it is essential to run a single refrigeration syste with ulti evaporator.in current research ulti-evaporator syste, with two evaporators is developed. These two evaporators are designed for three different teperatures. These two evaporators ay be used for different application one is for refrigerator & another is for air conditioner. The arrangeent is ade to vary the load on evaporator by using electrical heater. The prie objective is to check the perforance of syste with variation in the teperature and load on the evaporator and siulate the syste with Cool Pack software. Keywords: Multi Evaporator Cobined Refrigerator & Air Conditioner, Cool Pack, Siulation. I INTROUCTION General refrigeration syste is single evaporator syste at one teperature. But any refrigeration installation, different teperature are required to be aintained at various points in the plant such as in hotels, large restaurants, institutions, industrial plants and food arkets where the food products are received in large quantities and stored at different teperature. For exaple, the fresh fruit, fresh vegetables, cut eats, frozen products, dairy products, bottled goods, have all different conditions of teperatures and huidity for storage. In such cases each location is cooled by own evaporator in order to obtain ore satisfactory control of the condition. For any industrial application, we require different teperature for different application, for exaple if we are using the refrigerator and air conditioner in the coercial space then we can get the cooling effect for storing the water bottles as well as the cooling effect for the huan cofort.to obtain such different teperature by noral single refrigeration syste is very difficult, as teperature requireent is different for different application, to follow econoy, low initial cost and operating cost it is essential to run a single refrigeration syste with ulti evaporator. And siulation is useful tool to obtain the results of syste in different operating conditions. 43 P a g e

2 II ESIGN OF SYSTEM 2.1 eign of low teperature evaporator 1. It is recoended that the evaporator teperature should be kept 5 o C below the teperature of the fluid to be cooled. Here let us consider the teperature of the fluid to be cooled as -10 o C i.e.263k. The design teperature of the evaporator = (263 5) = 258K 2. Let us select an appropriate refrigerant for the evaporator teperature to be obtained. A little consideration shows that R 404a is a good choice because it is having a boiling point of about -47 o C (226 K). This is a coonly used refrigerant used in low teperature refrigeration. 3. a) Calculation of Refrigeration effect Let s consider the low teperature evaporator is used to store ilk chocklet having specific heat of 0.20 Btu/lb o f.ass of ilk chocklet to be stored= 1 kg.specific heat of chocklet(c p ) = 0.20 Btu/lb o f. = KJ/KgK Let us consider an abient teperature of 30 o C (303 K)The ilk chockletis supposed to store at teperature of -10 o C (263 K)Hence teperature difference, ΔT = ( ) K = 40 K. We can calculate the Refrigeration effect as Q. C. T p = 1 x x 40 = 18.59kJ. Fro p-h chart of R 404a, Enthalpy h 5 =360 kj/kg.enthalpy h 4 = 260kJ/Kg. b) Calculation of ass of the refrigerant flowing through the syste () 1 Q q c 1 1 Q ( h h ) ( ) kg a) Evaporator tube selection- Copper tube is selected due to its good workability, high theralconductivity, and corrosion resistance. b) Selection of copper tube diaeter is ade 3/8 or 10, as per anufacturer ssuggestion. c) Tube wall thickness is selected as 1, as per anufacturer s suggestion. 44 P a g e

3 5. Calculation of surface area of evaporator (A)- For this calculation we need the values of ΔT = Log ean teperature difference (LMT).AndU = overall heat transfer coefficient. LMT is given as L M T [( T T ) ( T T )] 1 L 2 ( T T ) 1 L ln ( T T ) 2 L L where, T L is the boiling teperature of the refrigerant and T 1, T 2 are teperatures of the ilk chocklet before storage and final teperature of chock let respectively. Here, T L is boiling point of R 404a,(as we know that the refrigerant teperature should be 5 o C less than that of the evaporator teperature i.e.263k ) = 268 K. For getting the values of T 1, T 2 let us decide ΔT. T 1 = 303 K and T 2 = 263 so that ΔT = 40 K. Thus, we can calculate L M T [( ) ( )] ( ) ln ( ) Thus, ΔT = K Thus, surface area of evaporator, A Q ( T. U ) A x 5 A = Calculation of length of Evaporator L A d L ( x ) L = 6.49 = ft, say 21 ft. 45 P a g e

4 2.2 eign of ediu teperature evaporator 1. It is recoended that the evaporator teperature should be kept 5 K below the teperature of the fluid to be cooled. Here the teperature of Evaporator to be aintained is 273K. The design teperature of the evaporator = (273 5) K = 258 K. 2. It is quite obvious that refrigerant selected while designing the low teperature evaporator i.e. R-404a will serve the purpose in ediu teperature evaporator also 3. a) Calculation of Refrigeration effect Let s consider the ediu teperature evaporator is used to store vegetable let having specific heat of 0.29 Btu/lb o f.vegetable to be stored = 1 kg. Specific heat of vegetable (C p ) = 0.29 Btu/lb o f. =1.172 KJ/KgK Let us consider an abient teperature of 30 o C (303 K) The vegetable is supposed to store at teperature of 0 o C (273 K) Hence teperature difference, ΔT = ( ) K = 30 K. We can calculate the Refrigeration effect as Q. C. T p = 3 x x 30 = kJ Fro p-h chart of R 404a, Enthalpy h 7 =362 kj/kg.enthalpy h 6 = 260kJ/Kg. b)calculation of ass of the refrigerant flowing through the syste ()- 2 Q q c 2 Q ( h h ) ( ) = kg. 4. a) Evaporator tube selection- Copper tube is selected due to its good workability, high theral conductivity, and corrosion resistance. b) Selection of copper tube diaeter is ade 3/8 or 10, as per anufacturer s suggestion. 46 P a g e

5 c) Tube wall thickness is selected as 1, as per anufacturer s suggestion. 5. Calculation of surface area of evaporator (A) For this calculation we need the values of ΔT = Log ean teperature difference (LMT). and U = overall heat transfer coefficient. LMT is given as L M T [( T T ) ( T T )] 1 L 2 ( T T ) 1 L ln ( T T ) 2 L L where, T L is the boiling teperature of the refrigerant and T 1, T 2 are teperatures of the vegetable before storage and final teperature respectively. Here, T L is boiling point of R 404a,(as we know that the refrigerant teperature should be 5 o C less than that of the evaporator teperature i.e.273k ) = 258 K. For getting the values of T 1, T 2 let us decide ΔT. T 1 = 303 K and T 2 = 263 so that ΔT = 40 K. Thus, we can calculate L M T Thus, [ ( ) -( ) ] ln ( ) / ( ΔT = K A Q ( T. U ) Thus, surface area of evaporator, A ( x 5 0 ) A = Calculation of length of Evaporator- L A d L ( x ) 47 P a g e

6 L = 4.35 = 14.27ft, say 14 ft. III SIMULATION BY USING COOL PACK COP of achine can be found out by using cool pack software: Cool pack Approach In the software siulation, soe of the readings that taken actually on the achine are required to check the results obtained fro the actual achine are ok or not. The cool pack gives us the direct calculations of the actual COP of the achine for the given pressure and the teperature. So that we can check that achine is working well or not. Figure 2: Cycle generated by cool pack software 48 P a g e

7 IV RESULTS AN ISCUSSION Figure 2: Cycle generated by cool pack software Table No.1 Result for COP with variation of load on syste Graph No.1 Coparison of actual COP and COP by cool pack 49 P a g e

8 Above graph no.1 shows that as the load on the evaporator increases the COP also increases. Rise in actual COP is observed fro the load change fro 0.9kW to 2.4kW. Graph No.2 Coparison of actual, theoretical and Carnot COP Above graph no.4 shows the coparison of COP actual, COPth and COP Carnot. COP Carnot is greater than COP actual and COPth. COP actual varies fro 1.07 to 2.43, COP theoretical varies fro 4.47 to 5.44 and COP Carnot varies fro 5.22 to Graph No.3 Refrigerating effect Above graph no.6 shows the refrigerating effect. Refrigerating effect increases because of its heat transfer coefficient increases. At higher load refrigerating effect is about 16% ore but as load decreases refrigerating effect decreases. 50 P a g e

9 Graph No.4 Copressor work Above graph no.6 shows copressor work. Copressor work is ore it because of ore pressure drop across evaporator so ore copressor work required. At higher load up to 6.67% ore work required. V COMPARISON OF RESULTS Following conclusion are ade fro the work carried out on effect of cobined unit of VCR syste. When syste is operated at sae loading conditions in individual ode and in cobined ode, the actual COP increased about 1.27% to 7.28%, theoretical COP about 2.07% to 5.93% and Carnot COP 2.38% to 7.42%. At the sae when syste siulate with Cool pack software results obtained are close to the actual output given by the cobined unit, the difference in the results of actual output and siulation varies fro 6% to 13%. The ain reason for the iproved perforance of this syste in cobined ode is due to reduction in copressor work and increase in refrigeration effect. Refrigerant effect also iproved about 2% to 16%. As the syste is siulated with Cool Pack software, so we can get any output by varying the different paraeters which will gives us very close results as that of actual working achine or syste. VI CONCLUSIONS AN SCOPE FOR FUTURE WORK Conclusions The current project work can be continued and thus has a scope for further of work. For this purpose, the following points can be considered with the sae set-up. They are as follows- 1. There is scope for analyzing the syste perforance by using different feasible refrigerants. 2. Perforance evaluation of the syste can be perfored at different abient teperatures. For this purpose, change in the teperature of local abient air should be done by artificial eans. 51 P a g e

10 3. Siulation of the syste can be done by using various software s like Matlabetc, and can be copared with experiental result. 4. Effect of heat transfer coefficient of refrigerant in evaporator can be studied. REFERENCES Cook R, Air Cooler & refrigerator, US patent No , June 11, Patrick E, Cobined Refrigerator & Air conditioner, US patent No , January 26, Ledbetter R, Air conditioning refrigerator, US patent No , April 18, Sanaye S and Malekohaadi H, Theral and econoical optiization of air conditioning units with vapor copression refrigeration syste, Applied Theral Engineering 24 (2004) Elliott M and Rasussen B, Model-Based Predictive Control of a Multi-Evaporator Vapor Copression Cooling Cycle Aerican Control Conference, Washington, USA (June 2008) 8. Hu T and Yoshino H, Analysis on Energy Consuption and Indoor Environent in Kuning China Sustainability 2012,Vol 4, Afonso C, Household refrigerators: Forced air ventilation in the copressor and its positive environental ipact, International Journal of Refrigeration,Vol.36 (2013) Niro G, Salles, Alcantara M, asilva L, Large-scale control of doestic refrigerators for deand peak reduction in distribution systes Electric Power Systes Research (2013) vol Zhu Y, Jin X, u Z, Fan B, Fu S, Generic siulation odel of ulti-evaporator variable refrigerant flow air conditioning syste International Journal of Refrigeration,Vol.36 (2013) P a g e