Study of the Effect of Mass flow Rate of Air on Heat Transfer Rate in Automobile Radiator by CFD Simulation using CFX.

Study of the Effect of Mass flow Rate of Air on Heat Transfer Rate in Automobile Radiator by CFD Simulation using CFX.

P.K.Trivedi1 , N.B.Vasava2

Students, IInd year M.E (Cad/Cam), Department of Mechanical Engineering.

Government Engineering College, Dahod, Gujarat-389151, India.

Abstract the radiator, heat is transferred through the fins and tube

It is generally known that the velocity of the airflow walls to the air by conduction and convection. The Radiator through the radiator is a function of the vehicle speed and of Tata indigo diesel car is analyzed to get heat transfer rate the heat transferred by a radiator is a function of the airflow at different air velocity in this study.

rate across the radiator This paper presents a

ComputationalFluidDynamics (CFD) modeling simulation 2. Experimental heat transfer calculation

of mass flow rate of air passing across the tubes of an

Radiator is considered as a Shell and Tube Type Heat

automotive radiator. An introduction to mass flow rate and Exchanger and Overall Dimensional Experimental Radiator its significance was elaborated in order to understand the are as under.

complications involved in the research and thereafter arrive

at the objectives. Knowing the geometry of tube in radiator is the crucial application of CFD to numerically model and thereby analyze the simulation. The Air flow simulation is conducted using commercial software ANSYS 12.1 The CFD process starts with defining the geometry using the CAD software Solid works and then it is followed by the meshing which create the surface mesh as well as volume mesh accordingly. After meshing, the boundary conditions are defining before solving that represents flow fields of the simulation. The flow characteristics are then analysed, compared and verified according to known physical situation and existing experimental data. The results obtained serve as good database for the future investigations.

Key words: Modeling, Simulation, CFD, Heating, Convection, Radiation, Heat transfer.

1. Introduction

Figure (1): Experimental heat exchanger

Shell Side Data:-

Media: – Air

There are two main types of cooling system for keeping Temperature: – 35°C

the temperature of the automobile engine within the Inlet Velocity: – 30 Kmph (Vehicle Speed) reasonable limits. These are the direct cooling or Air Outlet Pressure: – 1.01325 bar

Cooling and the indirect Air or Water cooling systems. The

indirect air cooling is called water cooling system. In Tube Side Data:-

indirect cooling, as the coolant flows through the tubes of Diameter of Tube: – 7 mm

Table A: Experimental Results Given by Company

No. of Tubes: – 29

Media: – Water + Ethanol (50%) Temperature (Engine):- 95 °C Inlet Velocity: – 2m/s

Outlet Pressure: – 1.01325 bar

Mass Flow Rate, Heat Transfer Rate and Overall Heat transfer Co-efficient are calculated as per its respective equations e.g. m = A * V * , Q = m * Cp * T and

1. CFD analysis

   1. Modeling of radiator

      After performing simple calculation, the modeling has been performed on the Solid works 2009 version and then after the analysis work has been performed on the ANSYS12.0 version.

      Figure (2): CAD model of radiator

      U = Q

      A (Toutlet Tmean )

      Table B: Experimental Result summary

      Sr No.	Velocity of Car Kmph	Engi ne Tem perat ure Tube Side Inlet	Tube Side Outlet Temper ature	Shell Side inlet temp eratu re	Shell Side Outlet temper ature	Mass of Air( m)	Heat Transfer Rate
      1	30	95	87.12	35	60.52	2.013	53.3696625
      2	40	95	86.92	35	62.15	2.684	76.4727964
      3	50	95	86.52	35	63.52	3.355	98.200179
      4	60	95	86.14	35	63.89	4.026	121.7438244
      5	70	95	85.95	35	64.52	4.697	143.267894
      6	80	95	85.14	35	65.27	5.368	169.5901504
      7	90	95	84.96	35	66.29	6.039	195.9124068
      8	100	95	84.52	35	68.26	6.71	231.980133

      Figure (3): Meshed model of radiator

   2. CFD analysis

      The Cavity Pattern method is used for CFD Analysis of radiator in this study. In cavity model, there are basically two Domains. D-1:-Water with addition of glycols & D- 2:- Air Domain The input data and boundary conditions are chosen from the study of Changhua Lin and Jeffrey Saunders [5]. The properties of air and

      coolant were defined for standard conditions and kept constant throughout the analysis.

   3. Results of Analysis

      1. Tube Side Results: –

         Figure (4): Inlet Temperature:-368*F (95* C)

         Figure (5): Outside Temperature:-359.94*F (86.94* C)

      2. Shell Side Results:-

         Figure (6): Inlet Temperature:-308*F (35* C)

         Figure (7): Outside Temperature:-334.25*F (61.25* C)

         As Per above Procedure, We have done 8 iteration for different Velocity and inlet temperature configuration which results are as below.

         Table C: CFD Resut summary

         S r N o .	Vel oci ty of Car K mp h	En gin e Te mp era tur e Tu be Sid e Inl et	Tube Side Outlet Tempe rature	Sh ell Sid e inl et te mp era tur e	Shell Side Outlet tempe rature	Mass of Air(m)	Heat Transfer Coefficient	Thermal Efficiency
         1	30	95	86.94	35	61.25	2.013	53.3696625	42.857143
         2	40	95	86.652	35	63.21	2.684	76.4727964	44.629014
         3	50	95	86.24	35	63.98	3.355	98.200179	45.295405
         4	60	95	85.96	35	64.94	4.026	121.7438244	46.104096
         5	70	95	85.79	35	65.2	4.697	143.267894	46.319018
         6	80	95	84.15	35	66.28	5.368	169.5901504	47.193724
         7	90	95	83.86	35	67.12	6.039	195.9124068	47.854589
         8	10 0	95	83.15	35	69.23	6.71	231.980133	49.443883

   4. CFD Validation

To validate the CFD results, comparisons were drawn between obtained results and received experimental data which is given below.

Table D: Comparison of Experimental results and CFD Results

1. References

   1. J.P.Holman, 2002, Heat transfer, Tata-McGraw-Hill Publications.

   2. ANSYS 12.1 User Guidelines.

   3. Hucho, W.H., Aeodyanamics of Road Vehicles, 4th Edition, SAE International, 1998.

   4. Hucho, W.H., Aeodyanamics of Road Vehicles, 4th Edition, SAE International, 1998.

      S r N o .	Vel ocit y of Car Km ph	En gin e Te mp era tur e Tu be Sid e Inl et	Tube Side Outlet Temp eratur e (Expe rimen tal)	Tube Side Outlet Temper ature	Sh ell Sid e inl et te mp era tur e	Shell Side Outlet tempe rature (Expe rimen tal)	Shell Side Outlet tempe rature	Percent age of variatio n Tube Side Temper ature	Percent age of variatio n Shell Side Temper ature
      1	30	95	87.12	86.94	35	60.52	61.25	0.2066	1.2062
      2	40	95	86.92	86.652	35	62.15	63.21	0.3083	1.6954
      3	50	95	86.52	86.24	35	63.52	63.98	0.3236	0.7241
      4	60	95	86.14	85.96	35	63.89	64.94	0.2089	1.6434
      5	70	95	85.95	85.79	35	64.52	65.2	0.1861	1.0539
      6	80	95	85.14	84.15	35	65.27	66.28	1.1745	1.5474
      7	90	95	84.96	83.86	35	66.29	67.12	1.2947	1.2520
      8	100	95	84.52	83.15	35	68.26	69.23	1.6209	1.4210

   5. Changhua Lin and Effect of Changes in

      Jeffrey Saunders, 2000, The mbient and Coolant Radiator

      Inlet Temperatures and Coolant Flow rate on Specific Dissipation, SAE Technical Papers, 2000-01-0579.

   6. Wikipedia, the free encyclopedia, Radiator, Wikipedia@ Wikimedia Foundation, Inc, 2006.

   7. Incropera, F.P.; and DeWitt, D.P. (2002).

4. Conclusion and future scope

The heat transfer analysis of an automotive radiator is successfully carried out using numerical simulation built in commercial software ANSYS 12.1. Above Results Shows that the heat transfer rate as well as efficiency is increased, as the air mass flow rate increases. With the computational time and resources available, the results obtained were found to be satisfactory. However, to account for the variation of the inlet conditions with time as in practical cases, transient analysis can be done.

Figure (8): Velocity v/s heat transfer rate

Fundamentals of heat and mass Transfer. (5th Ed.), Wiley, New York.