Original Article PERFORMANCE ANALYSIS OF FINNED TUBE AIR COOLED CONDENSING UNIT OF SPLIT AIR CONDITIONER

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Available online at http://.urpjournals.com Advanced Engineering and Applied Sciences: An International Journal Universal Research Publications.

com, Ph no: 9010131513 Received 21 December 2014; accepted 02 January 2014 Abstract The performance of residential and commercial air-conditioners has a large influence on electrical energy

Performance improvement of the condenser can be achieved by improving the heat transfer efficiency.

1 Available online at Advanced Engineering and Applied Sciences: An International Journal Universal Research Publications. All rights reserved ISSN Original Article PERFORMANCE ANALYSIS OF FINNED TUBE AIR COOLED CONDENSING UNIT OF SPLIT AIR CONDITIONER B. SREELAKSHMI, MTech, Ph no: Received 21 December 2014; accepted 02 January 2014 Abstract The performance of residential and commercial air-conditioners has a large influence on electrical energy consumption. The performance or specific energy consumption of air conditioning system depends upon the performance of condensers, compressors and evaporators. Performance improvement of the condenser can be achieved by improving the heat transfer efficiency. In the present ork, the performance analysis of air cooled condensing unit has been carried out by varying the fin material and fin thickness. At present aluminum alloy 204 is being used for fins. To fin materials namely, Aluminum alloys 1100 and 6063ere considered to study the effect of fin s thermal conductivity on the performance of the condenser. Pro Engineer is used to model the system. For thermal analysis purpose COSMOSWorks softare is used. Considering different factors for a condenser, such as heat transfer, density etc., Aluminum alloy 1100is found to be the best fin material Universal Research Publications. All rights reserved 1.1AIR CONDITIONER An air conditioner (often referred to as AC) is a home appliance, system or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle. In construction, a complete system of heating, ventilation and air conditioning is referred to as "HVAC. Its purpose, in a building or an automobile, is to provide comfort during either hot or cold eather. 1.2 AIR CONDITIONING SYSTEM BASICS AND THEORIES Fig1: Simple stylized diagram of the refrigeration cycle: In the refrigeration cycle, a heat pump transfers heat from a loer-temperature heat source into a higher-temperature heat sink. Heat ould naturally flo in the opposite direction. This is the most common type of air conditioning. A refrigerator orks in much the same ay, as it pumps the heat out of the interior and into the room in hich it stands. This cycle takes advantage of the phase change ork, here latent heat is released at a constant temperature during a liquid/gas phase change, and here varying the pressure of a pure substance also varies its condensation/boiling point. The most common refrigeration cycle uses an electric motor to drive a compressor. In an automobile, the compressor is driven by a belt over a pulley, the belt being driven by the engine's crankshaft (similar to the driving of the pulleys for the alternator, poer steering, etc.). Whether in a car or building, both use electric fan motors for air circulation. Since evaporation occurs hen heat is absorbed, and condensation occurs hen heat is released, air conditioners use a compressor to cause pressure changes beteen to compartments, and actively condense and pump a refrigerant around. A refrigerant is pumped into the evaporator coil, located in the compartment to be cooled, here the lo pressure causes the refrigerant to evaporate into a vapor, taking heat ith it. At the opposite side of the cycle is the condenser, hich is located outside of the cooled compartment, here the refrigerant vapor is compressed and forced through another heat exchange coil, condensing the refrigerant into a liquid, thus rejecting the heat previously absorbed from the cooled space. By placing the condenser (here the heat is rejected) inside a compartment, and the evaporator (hich absorbs heat) in the ambient environment (such as outside), or merely running a normal air conditioners refrigerant in the opposite direction, the overall effect is the opposite, and the compartment is heated. This is usually called a heat pump, and is capable of heating a home to comfortable temperatures (25 C; 70 F), even hen the outside air is belo the freezing point of ater (0 C; 32 F). 7

2 1.3. REFREGERENTS "Freon" is a trade name for a family of haloalkane refrigerants manufactured by DuPont and other companies. These refrigerants ere commonly used due to their superior stability and safety properties. Hoever, these chlorine-bearing refrigerants reach the upper atmosphere hen they escape. Once the refrigerant reaches the stratosphere, UV radiation from the Sun cleaves the chlorine-carbon bond, yielding chlorine radical. These chlorine atoms catalyze the breakdon of ozone into diatomic oxygen, depleting the ozone layer that shields the Earth's surface from strong UV radiation. Each chlorine radical remains active as a catalyst unless it binds ith another chlorine radical, forming a stable molecule and breaking the chain reaction. The use of CFC as a refrigerant as once common, being used in the refrigerants R-11 and R-12. In most countries the manufacture and use of CFCs has been banned or severely restricted due to concerns about ozone depletion. In light of these environmental concerns, beginning on November 14, 1994, the Environmental Protection Agency has restricted the sale, possession and use of refrigerant to only licensed technicians, per Rules 608 and 609 of the EPA rules and regulations; failure to comply may result in criminal and civil sanctions. Neer and more environmentally-safe refrigerants such as HCFCs (R-22, used in most homes today) and HFCs (R-134a, used in most cars) have replaced most CFC use. HCFCs in turn are being phased out under the Montreal Protocol and replaced by hydro fluorocarbons (HFCs) such as R-410A, hich lack chlorine. Carbon dioxide (R-744) is being rapidly adopted as a refrigerant in Europe and Japan. R-744 is an effective refrigerant ith a global arming potential It must use higher compression to produce an equivalent cooling effect. 1.4 THE CONSTRUCTION PRNCIPLE Refrigerant and air ill be physically separated, at air conditioner condenser, and evaporator. Therefore, heat transfer occurs by means of conduction. We ould like the heat exchanger that enables these processes, to have, High conductivity this property ill ensure that the lo temperature difference beteen the outside all, and inside all High contact factor this property ensures the passing air mass, ill come in contact ith the tubes, as much as possible 1.5 SPECIFICATIONS OF CONDENSOR The length and size of air conditioner condensers and evaporators have to be sized such that, the refrigerant is completely condensed before the condenser s exit, and the refrigerant is completely boiled before the evaporator s exit 1.6 CONTACT FACTOR It is the amount of media that needs to be heated up or cooled don, that comes directly in contact ith the tube alls. Contact factor ill be very lo, if the air inside a duct is passed through a straight tube ith refrigerant. This happens as the amount of air that contacts the tube ill be very lo. Therefore, e ill increase the contact factor, by constructing the condenser and evaporator to have many passes ithin a given duct area. Thus, the passing air ill see a lot of tubes on its passage. Hence the contact factor ill be improved The maximum theoretical contact factor is 100%. We ill have contact factors around 80% for commercially produced air conditioner evaporators and air conditioner condensers. The real figures really depend on each manufacturer. 2. COOLING LOAD CALCULATIONS Cooling load calculations for air conditioning system design are mainly used to determine the volume flo rate of the air system as ell as the coil and refrigeration load of the equipment to size the HVAC&R equipment and to provide the inputs to the system for energy use calculations in order to select optimal design alternatives. Cooling load usually can be classified into to categories: external and internal 2.1 External Cooling Loads. These loads are formed because of heat gains in the conditioned space from external sources through the building envelope or building shell and the partition alls. Sources of external loads include the folloing cooling loads: 1. Heat gain entering from the exterior alls and roofs 2. Solar heat gain transmitted through the fenestrations 3. Conductive heat gain coming through the fenestrations 4. Heat gain entering from the partition alls and interior doors 5. Infiltration of outdoor air into the conditioned space 2.2. Internal Cooling Loads. These loads are formed by the release of sensible and latent heat from the heat sources inside the conditioned space. These sources contribute internal cooling loads: 1. People 2. Electric lights 3. Equipment and appliances If moisture transfers from the building structures and the furnishings are excluded, only infiltrated air, occupants, equipment, and appliances have both sensible and latent cooling loads. The remaining components have only sensible cooling loads. All sensible heat gains entering the conditioned space represent radiative heat and convective heat except the infiltrated air, radiative heat causes heat storage in the building structures, converts part of the heat gain into cooling load, and makes the cooling load calculation more complicated. Latent heat gains are heat gains from moisture transfer from the occupants, equipment, appliances, or infiltrated air. If the storage effect of the moisture is ignored, all release heat to the space air instantaneously and, therefore, they are instantaneous cooling loads. 2.3 THERMAL FLUX CALCULATIONS Inside temperature = 50 0 C+273 = 323K Atmospheric temperature =40 0 C+273 = 313K Total area = Contact area = Discharge of heat flo = x = 21mm Tube thickness = 1 Calculating heat flux for 3 different materials: 1. Copper : Thermal conductivity = K =390W/mk 8

2. Aluminum(204): K = 150 W/mk 3. Aluminum(1100): K = 220 W/mk 4. Aluminum(6063): K = 193W/mk For HCFC Heat Transfer Coefficient = 243 1.

Heat flux for Aluminum 1100 and HCFC as refrigerant Heat flo is given by = q = U A product development cycle typically includes the folloing steps: 1. Build your model in the Solid Works CAD system.

3 2. Aluminum(204): K = 150 W/mk 3. Aluminum(1100): K = 220 W/mk 4. Aluminum(6063): K = 193W/mk For HCFC Heat Transfer Coefficient = Heat flux for aluminum (204) and HCFC Heat flo is given by = q = U 2. Heat flux for Aluminum 1100 and HCFC as refrigerant Heat flo is given by = q = U A product development cycle typically includes the folloing steps: 1. Build your model in the Solid Works CAD system. 2. Prototype the design. 3. Test the prototype in the field. 4. Evaluate the results of the field tests. 5. Modify the design based on the field test results 5. THERMAL ANALYSIS OF AC CONDENSER Fig3: Aluminium 204-Temperature 3. Heat flux for Aluminum 6063 and HCFC as refrigerant Heat flo is given by = q = U 3. MODEL OF CONDENSER Fig4: Aluminium 204-Themal Gradient Fig2: model of condenser 4. ANALYSIS SOFTWARE Cosmos orks is useful softare for design analysis in mechanical engineering. COSMOS Works is a design analysis automation application fully integrated ith Solid Works. This softare uses the Finite Element Method (FEM) to simulate the orking conditions of your designs and predict their behavior. FEM requires the solution of large systems of equations. Poered by fast solvers, COSMOS Works makes it possible for designers to quickly check the integrity of their designs and search for the optimum solution. Fig5: Aluminium 204-Thermal flux Fig6: Aluminium 1100-Temperature 9

By observing optimization results, the optimum thickness value for decreased volume is 1mm. 7.

4 Fig7: Aluminium 1100-Themal Gradient Fig8: Aluminium 1100-Thermal flux Fig 9: Aluminium 6063-Temparature 6. OPTIMIZATION OF CONDENSER BY CHANGING THICKNESS: I have optimized the condenser to reduce the volume, by changing the thickness of the fin. By observing optimization results, the optimum thickness value for decreased volume is 1mm. 7. RESULTS AND DISCUSSIONS The Thermal Analysis of the Condensing unit has been carried out using COSMOSWORKS softare. The result obtained the analysis ere summarized in Table 1 and 2. TABLE1: Thermal analysis result table HCFC AL204 AL1100 AL6063 TEMP(K) TG(K/m) TF (W/m 2 K) Table1 shos Thermal flux obtained for different Fin material at a thickness of 1mm, so it can be observed from the table the maximum Heat Flux has been obtained for a Fin made up of AL1100. TABLE 2: Optimization result table THICKNESS Al e THER Al MAL 110 FLUX 0 Al e Table 2. shos Thermal Flux for different Fin material ith different Thickness. From the table it can be observed that the condensing unit made up of AL1100 Fins ith 0.75mm thickness rejects maximum Heat to the surrounding air.hence 0.75mm thickness is considering to the optimum thickness for Fins 8. GRAPH: Fig10: Aluminium 6063-Thermal gradient Fig11: Aluminium 6063-Thermal flux Graph1: Thermal flux Vs Thickness From the Graph 7.1 it is observed that the maximum Thermal Flux has been obtained for a Fin made up of AL1100 ith 0.75mm thickness is considering to the maximum 9. CONCLUSIONS In this study, condenser model as developed in Pro Engineer and COSMOSWorks softare is used for thermal analysis. The effects of changing the fin material 10

5 and fin thickness on condenser performance have been investigated. The folloing conclusions ere dran from the analysis: 1. Considering different factors for a condenser, such as heat transfer, density, etc., Aluminum alloy 1100 is found to be the best fin material. 2. The results sho that the heat transfer decreases ith an increased fin spacing. These differences are caused by decreased fin ake interactions ith increased fin spacing. 3. Fin thickness of 0.75 mm is found to be the optimum. 10. REFERENCES 1. Wang, C. C., Lee, C. J., Chang, C. T., and Chang Y. J., Some Aspects of Plate Fin-and-Tube Heat Exchangers ith and ithout Louvers, J. Enhanced Heat Transfer, vol. 6, no. 5, pp Wang, C. C., Chi, Y. P. Chang, K. Y. C., and Chang, Y. J., An Experimental Study of Heat Transfer and Friction Characteristics of Typical Louver Fin and Tube Heat Exchangers, Int. J. of Heat and Mass Transfer, vol. 41, no. 4-5, pp Chi, K., Wang, C. C., Chang, Y. J., and Chang, Y. P., A Comparison Study of Compact Plate Finand-Tube Heat Exchangers, ASHRAE Transactions, vol. 104, no. 2, pp Kays, W. M. and London, A. L., Compact Heat Exchangers, 3rd Edition, McGra- Hill, Ne York. 5. Shepherd, D. G., Performance of One-Ro Tube Coils ith Thin Plate Fins, Heating, Piping, & Air Conditioning, vol. 28, no. 4, pp Rich, D. G., The Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Ro, Smooth Plate Fin-and-Tube Heat Exchangers, ASHRAE Transactions, vol. 79, pt. 2, pp ASHRAE Handbook of Fundamentals ASHRAE Handbook of Fundamentals 9. ASHRAE Cooling and Heating Load Calculation Manual [10] ASHRAE Standard 62, Indoor Air Quality 10. Bivens, D. B., Shiflett, M. B., Wells, W. D., Shealy, G. S., Yokozeki, A., Patron, D. M. Kolliopoulos, K. A., Allgood, C. C., and Chisolm, T. E. C., HFC-22 Alternatives for Air Conditioners and Heat Pumps, ASHRAE Transactions, vol. 101, pt. 2, pp [12]Baxter, V., Fischer, S., and Sand, J., Global Warming Implications of Replacing Ozone- Depleting Refrigerants, ASHRAE Journal, vol. 40, no. 9, pp International Journal of Engineering Research & Technology (IJERT) Vol. 2 Issue 1, January ISSN: Air Conditioning Engineering by R.S.KURMI Source of support: Nil; Conflict of interest: None declared 11

Improving The Heat Transfer Rate For Ac Condenser By Material And Parametric Design Optimization

Improving The Heat Transfer Rate For Ac Condenser By Material And Parametric Design Optimization V Srividhya 1, G Venkateswara rao 2 PG Student 1, Asst Professor 2 Department of Mechanical Engineering,