ANALYSIS AND VALIDATION OF FIN TUBE EVAPORATOR

7/30/2019 ANALYSIS AND VALIDATION OF FIN TUBE EVAPORATOR

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International Journal of Application or Innovation in Engineering& Management (IJAIEM)Web Site: www.ijaiem.org Email: [email protected], [email protected]

Volume 2, Issue 3, March 2013 ISSN 2319 - 4847

Volume 2, Issue 3, March 2013 Page 430

ABSTRACTAn Evaporator is the Main component of Air-conditioning system. An evaporator is mainly used in different refrigeration and

air-conditioning applications in food and beverage industry, in thepharmaceutical industry etc. An evaporator in air

conditioning system is used to evaporate liquid and convert in to vapour while absorbing heat in the processes, this paperpresents the study of the fin tube type Evaporator; An Experimental data were collected from the IC ICE MAKE Company.

After collecting data of fin tube evaporator model is prepared using solid works. At the end, FEA analysis is carried out on it

using ANSYS CFX, The result of analysis is compared with Experimental result. 3.7% variation found in both results.

Key words: Fin-tube Evaporator, Experimental Data, Solid-Works, ANSYS-CFX, FEA

1.INTRODUCTIONAn evaporator is used in an air-conditioning system or refrigeration system to allow a compressed cooling chemical,such as Freon or R-22, to evaporate from liquid to gas while absorbing heat in the process. It can also be used to

remove water or other liquids from mixtures. The process of evaporation is widely used to concentrate foods andchemicals as well as salvage solvents. In the concentration process, the goal of evaporation is to vaporize most of thewater from a solution which contains the desired product.

Evaporation is an operation used to remove a liquid from a solution, suspension, or emulsion by boiling off a portionof the liquid. It is thus a thermal separation, or thermal concentration, process. We define the evaporation process asone that starts with a liquid product and ends up with a more concentrated, but still liquid and still pumpableconcentrate as the main product from the process.

In the evaporator, the refrigerant is evaporated by the heat transferred from the heat source. The heat source may be agas or a liquid or, e.g. in food freezers, a solid. During evaporation, the temperature of a pure refrigerant is constant, aslong as the pressure does not change. The basic temperature profile through an evaporator with liquid or gas phase heatsource is therefore as shown in Figure .As shown; the temperature of the refrigerant must be below that of the heatsource. This low refrigerant temperature is attained as a result of the reduction in pressure caused by the compressor:When the compressor is started and the pressure reduced, the equilibrium between liquid and vapour in the evaporatoris disturbed. To re-establish equilibrium, more vapour is formed through evaporation of liquid. The heat of vaporizationnecessary for this is taken from the liquid itself, and therefore the liquid temperature drops. As heat starts to flow from

the heat source, a new equilibrium temperature is established. In the evaporator there is thus a balance between the heattransferred to it due to the temperature difference between the evaporator and the surroundings, and the heat transferredfrom it in the form of heat of vaporization of the vapour drawn into the compressor.

ANALYSIS AND VALIDATION OF FIN TUBE

EVAPORATORKiran.B.Parikh1, Tushar.M.Patel2

1M.E Scholar, Thermal Engineering, LDRP-ITR, Gandhinagar, Gujarat.

2 Associate professor, LDRP-ITR, Gandhinagar, Gujarat.


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The evaporator is one of the four basic and necessaryhardwarecomponents of the refrigeration system. Pressuredrop, heat transfer rate, evaporation rate and most important thing is efficiency of evaporator, all four things areincrease and improve by getting optimum parameter of evaporator, this optimum parameter of evaporator aregenerated with the help of experimental data and CFD analysis.

2.EXPERIMENTAL DATA OF FIN TUBE EVAPORATORThe experimental investigation has been carried out at IC ICE MAKE REFRIGERATION to improve the performancecharacteristics of evaporator. The following data are collected during experiment.Parameter of Evaporator:

1)Tube Outer Diameter:9.53 mm2)Tube Inner Diameter:8.53 mm3)Tube thickness: 0.5mm4)Tube Pitch(Longitudinal and Transverse both): longitudinal pitch=25mm,transverse pitch=30mm

5)Tube Material: Copper6)No. of Turns:97)Fin Pitch and thickness: pitch=4.33mm,fins thickness=0.25mm

Figure 2.1Experimental model of evaporator8)Position of inlet and Outlet:


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9)Overall Size of Evaporator:1448*406.4mm

10)Material of Fin: aluminium11)Tube bending Radius:30mm

12) Inlet Temperature and Pressure(Experimental):259k13)Outlet Temperature(Experimental):269k14)Mass flow rate:1.5 kg/sec15)Tube Fluid:R-2216)Refrigerant : R-2217)Mass of refrigerant: 1.5kg18)Capillary length: 11' +6_ coil19)Capillary diameter: 0.036 mm

An evaporator is the main component of heat exchange between the working fluid (The refrigerant) and theenvironment of freezer.REVIEWT. Sriveerakul et al [1] investigated the use of CFD in predicting performance of a steam ejector used in refrigerationapplications. This study is reported in a series of two papers. In this part, the CFD results were validated with theexperimental values. The effects of operating conditions and geometries on its performance were investigated. TheCFDs results were found to agree well with actual values obtained from the experimental steam jet refrigerator. DavidYashar at al [2] presented a comparable evaluation of R600a (isobutene), R290 (propane), R134a, R22, R410A, andR32 in an optimized finned-tube evaporator, and Analyzes the impact of evaporator effects on the System coefficient ofperformance (COP), The study relied on a detailed evaporator model derived from NISTs EVAP-COND simulationpackage and used the ISHED1 scheme employing a non-Darwinian learnable evolution model for circuitry

optimization. Devendra A. Patel et al [3] observed that 1. Case-I shows calculation for actual readings and case-IIshows calculation for simulation when inlet temperature of oil & cooling water are kept unchanged. 2. As the outlettemperature of oil is 1 degree less in case-II, the values of heat transfer rate, overall heat transfer co-efficient &effectiveness are higher for case-I I compared to the case-I . 3. Case-I I, III & IV shows the calculation and results forsimulation readings. The cooling water inlet temperature is gradually decreased by 2 degree in each case. 4. As thetemperature difference between oil inlet temperature and water inlet temperature, becomes larger, the values of qmaxincreases. This is why, the heat transfer rate, overall heat transfer co-efficient and effectiveness is higher in case-III andcase-VI compared to case-II. The CFD analysis enables us to find out, on an average base, the performance of anactually operating heat exchanger. We can also come to know the temperatures at any points in heat exchanger.However, the results available through CFD analysis are for the ideal condition, i.e. for no-loss operating condition. QiFan et al [4] said that the numerical simulations of dimple jacket constructions were performed by a computationalfluid dynamics (CFD) program FLUENT in this work. The effects of geometrical parameters such as cone angle,

arrangement, interval and height of dimple on heat transfer and pressure drop of dimple jackets in thin-film evaporatorwere investigated numerically. The results of numerical simulations were provided for comparison in order to getadvisable configuration. The distance between dimples was found to have a considerable effect On heat transfer and in-line configuration was recommended because the pressure drop in it was smaller under the same heat transfer rate.

Inlet:

Outlet:


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3.MODELLINGOFFINTUBEEVAPORATORAfter Getting Experimental data, the modeling has been performed on the Solid works 2009 version and then after theanalysis work has been performed on the ANSYS 12.0 version.

Fig 3.1 Isometric Model of Evaporator

Fig 3.2Top view

Fig 3.3side view


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Fig 3.4Front view

4.CFDANALYSISOFEVAPORATORThe equations of fluid mechanics which have been known for over a century are solvable only for a limited no. of flows.The known solutions are extremely useful in understanding fluid flow but rarely used directly in engineering analysis ordesign. CFD makes it possible to evaluate velocity, pressure, temperature, and species concentration of fluid flowthroughout a solution domain, allowing the design to be optimized prior to the prototype phase.Availability of fast and digital computer makes techniques popular among engineering community. Solutions of theequations of fluid mechanics on computer has become so important that it now occupies the attention of a perhaps athird of all researchers in fluid mechanics and the proportion is still is increasing. This field is known as computationalfluid dynamics. At the core of the CFD modeling is a three-dimensional flow solver that is powerful, efficient, andeasily extended to custom engineering applications. In designing a new mixing device, injection grid or just a simple

gas diverter or a distribution device, design engineers need to ensure adequate geometry, pressure loss, and residencetime would be available. More importantly, to run the plant efficiently and economically, operators and plant engineersneed to know and be able to set the optimum parameters.4.1 PROCEDURE OF CFD ANALYSIS FOR EVAPORATOR

1) Create Simplified 3D Model of Evaporator Single Path in Solid works 2009.

Fig 4.1Evaporator Single Path

Fig 4.2Porous Domain for Air


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2) Create Cavity Domain for CFD Analysis.

Fig 4.3Cavity Domain for Inner and Outer Fluid3) Assemble Simplified 3D Model and Cavity Domain.

Fig 4.43D and Cavity Domain4) Save above model in *.IGES Format for Importing into ANSYS Workbench Mesh Module.5) Import Above Saved *.IGES File in ANSYS Workbench.

Fig 4.5Mesh Module6) Define Connection between Pipe and Fin for Heat Transfer.

Fig 4.6Connection between Pipe and Fin for Heat Transfer7) Create Mesh.

Type of Analysis: - 3D


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Type of Element: - Tetrahedral (10 Node)

Fig 4.7Tetrahedral (10 Node) Element

Fig 4.8Tetrahedral (10 Node) Element define in ANSYS CFX

Number of Nodes: - 410634Number of Element: - 1185861

8) Save above meshed model in *.CMDB Format for Importing into ANSYS CFX.9) Import above *.CMDB File in ANSYS CFX PRE.

Fig 4.9CMDB Format for Importing into ANSYS CFX

10) Define Type of Analysis.


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Type of Analysis: - Steady State

Fig 4.10Steady State analysis

11) Define Porous Domain for Fins.Domain Type: - PorousDomain Material: - Air Ideal GasDomain Motion: - StationaryVolume Porosity: - 0.8

Fig 4.11Porous Domain for Fins

Fig 4.12Porous Domain for Fins


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12) Define Heat Transfer and Turbulence model for Porous Domain.Heat Transfer Model: - Total Energy

Turbulence Model: - K-Where k is the turbulence kinetic energy and is defined as the variance of the fluctuations in velocity. It hasdimensions of (L2 T-2); for example, m2/s2.

is the turbulence eddy dissipation (the rate at which the velocity fluctuations dissipate), as well as dimensionsof k per unit time (L2 T-3) (e.g., m2/s3).

The k- model introduces two new variables into the system of equations. The continuityEquation is then:

And the momentum equation becomes

Fig 4.13Heat Transfer and Turbulence model for Porous Domain13) Define Inlet for Porous Domain.

Inlet Velocity: - 10 m/sInlet Temperature: - 300 K

Fig 4.14Inlet for Porous Domain14) Define Outlet.

Static Pressure: - 1.01325 bar


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Fig 4.15Outlet for Porous Domain

15) Define Solid Domain for Copper Pipe.

Fig 4.16Solid Domain for Copper Pipe Type of Domain: - SolidType of Material: - CopperDomain Motion: - Stationary

16) Define Heat Transfer Model for Solid Domain.Heat Transfer Model: - Thermal Energy

Fig 4.17Heat Transfer Model for Solid Domain


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17) Define Domain for Refrigerant.Domain Type: - FluidDomain Material: - R22Domain Motion: - Stationary

Fig 4.18Domain for Refrigerant18) Define Heat Transfer and Turbulence Model for Refrigerant.

Heat Transfer Model: - Total EnergyTurbulence Model: - K-Where k is the turbulence kinetic energy and is defined as the variance of the fluctuations in velocity. It hasdimensions of (L2 T-2); for example, m2/s2.

is the turbulence eddy dissipation (the rate at which the velocity fluctuations dissipate), as well as dimensionsof k per unit time (L2 T-3) (e.g., m2/s3).

The k- model introduces two new variables into the system of equations. The continuityEquation is then:

and the momentum equation becomes

Fig 4.19Heat Transfer and Turbulence Model for Refrigerant


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19) Define inlet for Refrigerant.Mass Flow Rate: - 1.5 Kg/sInlet Temperature: - 259 K

Fig 4.20inlet for Refrigerant

Fig 4.21inlet for Refrigerant20) Define Outlet.

Fig 4.22outlet for Refrigerant

21) Define Interface for Heat Transfer. Interface between Inner Refrigerant and Copper Pipe.Interface Type: - Fluid Solid


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Fig 4.23 Interface for Heat Transfer

Interface between Outer Air and Copper Pipe.Interface Type: - Porous Solid

Fig 4.24Interface between Outer Air and Copper Pipe22) Define Solver Control Criteria.

Convergence ControlResidual Target: - 1e-4

Fig 4.25Solver Control Criteria

23) Run the Analysis


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24) Get the ResultsResults of AnalysisOutlet Temperature of Refrigerant

Fig 4.26Outlet Temperature of Refrigerant

5. CONCLUSIONThe analysis gives outlet Temperature which is in desired limit as shown in table.

Table 1Comparison of Experimental Results and CFD Analysis Results.

The deviation in results is due to perfectness of CFD analysis and uncertainty of experiments.6. ACK NOWLEDGMENT

Authors are thankful to the IC ICE MAKE Pvt. Ltd Ahmadabad for providing very useful data and allowing to conductthe several tests & measurements at their Works.

REFERENCES[1] T. Sriveerakul, S. Aphornratana, K. Chunnanond, Performance prediction of steam ejector using computational

fluid dynamics: Part 1. Validation of the CFD results, International Journal of Thermal Sciences 46 (2007) 812822

[2] David Yashar, Piotr A. Domanski, Minsung Kim, Performance of a finned-tube evaporator optimized for differentrefrigerants and its effect on system efficiency, International Journal of Refrigeration 28 (2005) 820827

[3] Devendra A. Patel, Milap M. Madhikar, Kunal A. Chaudhari, Nirav B. Rathod, Heat Transfer Analysis of Oil

Cooler Shell and Tube Type Heat Exchanger using CFD, ISSN 0974-3146 Volume 4, Number 1 (2012), pp. 41-46

[4] Qi Fan, Xia Yin, 3-D numerical study on the effect of geometrical parameters on thermal behavior of dimple jacketin thin-film evaporator, Applied Thermal Engineering 28 (2008) 18751881

AUTHORMr. K iran.B.Parikh received the B.E. degree in Mechanical Engineering from L.D.R.P. I.T.R., Sector 15, Gandhinagar in 2011.Perusing in Master of Engineering in Thermal Branch at L.D.R.P. I.T.R.Gandhinagar, Gujarat, India.

Prof. Tushar M. Patel received the B.E. and M.E. degrees in Mechanical Engineering from GEC,

Modasa and LDCE, Ahmadabad in 1999 and 2008, respectively. He is working as an Associate professorat LDRP-ITR, Gandhinagar. He has total 13 years of experience. He is author of several books.

Description Experimental CFD Analysis % Deviation

Temperature 269 268.9 3.7

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ANALYSIS AND VALIDATION OF FIN TUBE EVAPORATOR

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