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Review Paper on Optimisation of fins by modifying geometry and materials used for production.

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Abstract-Convection may be defined as a mode of heat transfer which occurs generally between a heated plate and a fluid stream. If this heat transfer takes place naturally, this phenomenon is known as free convection. On the other hand, if heat transfer takes place on the account of some external media like fan or blower, then it is termed as forced convection. The heat transfer rate can be increased by employing extended surfaces on the region where the heat transfer rate is intended to be increased. These extended surfaces are termed as fins. The main objective of using fins is to facilitate heat transfer and get improved values of convected heat. Fins are used in different places, particularly in automobiles and bikes, in engines for increasing the heat transfer rate.

Keywords-  Fins, heat transfer, film coefficient, yttrium oxide, reynolds number, nusselt number, efficiency, natural, forced, convection.

I. INTRODUCTION

​The main use of fins is to increase convective heat transfer and to achieve an increased heat transfer area without using excessive primary surface area. They are basically used in Internal Combustion engine cooling such as fins in a car radiator. It is of utmost importance to predict the distribution of temperature within the fins so as to choose a configuration that is most effective.

​Increase in efficiency of fins can be achieved by various methods which will be discussed in this paper. In an automobile, air-fuel mixture is used to produce power through combustion only. Out of the total energy liberated, only a part of it is used to run the automobile, the remaining energy is wasted in form of heat and exhaust gases. In case this excess heat is not dissipated from the engine, it results into overheating of the engine. This is accomplished with the help of cooling system. About 34% of the energy generated by the engine during combustion is lost in heat. In order to increase the cooling effect and minimise the stress on engine, it is necessary to redesign radiators in automobile to be more compact and still maintain high level of heat transfer performance. Size of the radiator becomes an important factor as small cars with powerful engines have become the need of the hour.

​Research has already been done in order to increase the heat transfer performance of radiator by using different parameters like material of the radiator tubes, discharge of the coolant, configuration of the tubes. diagram

II. LITERATURE REVIEW

Ebin Jose et al [1]- Experimentally investigated the effect of changing geometry of fins in automobile radiators on the efficiency and heat transfer rate of fins. The diameter of the circular shaped radiator is assumed to be equal to the length of the rectangular radiator. The fins are assumed to be arranged in same pattern for both radiators. The optimisation parameters for circular radiator are arrangement of tubes, number of tubes, shape of inlet tank of coolant. If ‘D’ is the length of one side of the square shaped radiator, then the area will be D2. The area for a circular shaped radiator with diameter ‘D’ will be π/ 4(D2).

 

Figue- Area Comparison

Reduction in area = Area of rectangular section- Area of circular section

= D2 - π/4(D2) Reduction in area = 21.4602%

So while selecting circular shape for radiator, about 21.46% of reduction in area can be achieved.

NUMERICAL METHODOLOGY

The radiator is assumed to be of symmetrical nature for the purpose of analysis. The inlet water velocity is considered to be 0.2072 m/s and inlet temperature of water is taken to be 328 K. Air velocity is assumed to be varying from 0 m/s to 2.4 m/s. At the wall of radiator, no slip condition is considered (u=v=w=0)

RESULTS AND DISCUSSION

Radiators

Heat transfer rate (watts)

Pressure drop (pa)

Conventional Rectangular radiator

Number of tubes- 38 tubes

tube arrangement- Parallel

893.47 W

29.25 Pa

Normal circular shape

Number of tubes- 38 tubes

Tube arrangement- Parallel

753.82 W

30.58 Pa

Modified circular radiator

Number of tubes- 40 tubes

Tube arrangement- Parallel

839.2 W

32.86 Pa

Modified circular radiator

Number of tubes- 37 tubes

Tube arrangement- Alternative

925.65 W

32.10 Pa

Modified circular radiator

Number of tubes- 38 tubes

Tube arrangement- Parallel

Tank shape changed

963.17 W

30.58 Pa (<5%)

Shivdas Kharche et al [2]:- Studied the effect of change in shape of the fins on the overall heat transfer. Different types of fins were used to increase the heat transfer rate. the fin shapes used was Rectangular, V-shaped, Triangular, Trapezoidal and circular. Some researchers used fins without notches and with notches. The heat transfer rate through notched fins was found to be more than that of fins without notches

 

Figue- Fin configurations.

OBJECTIVE

It was observed from the literature survey that the material used for manufacturing of fins was aluminium. The effects were analysed by changing the parameters such as length, height, spacing on the film coefficient. The dimensions used for experimental investigation of copper are, length 127 mm, height 38 mm, space between the fins is 9 mm. The thickness of fin is considered to be 1 mm. The shape of the notch is rectangular. The effect of film coefficients for fins with and without notches was examined

EXPERIMENTAL SETUP AND PROCEDURE

Experimental setup consists of base copper plate of 190x110mm having thickness 1 mm. the dimensions of the fins is length is  127 mm, height is 38 mm and thickness 1 mm. Number of fins are 7 and the fins are joined to base plate by brazing. The spacing between fins is 9 mm, whereas the length, height is fixed. A heater coil is used for the heating plate. The plate is fixed in a insulating material to avoid the heat losses from either side of plate. The whole assembly is placed in a wooden block for the purpose of natural convection. Heat inputs of varying values are given to the plate and temperatures were noted down at the plate and fins.

OBSERVATIONS

Sr No

Heat input in W

h without notch (W/m^2K)

h for 20% notched fin (W/m^2K)

1

50

8.05

9.33

2

60

8.23

9.62

3

70

8.55

10.01

4

80

8.71

10.27

Figure- Comparison between normal and notched fins

Arun.S et al [3]:- Studied the effect on the heat transfer rate of fins by coating the fin surface by Yttrium oxide. It is a conversion oxide coating formed on the metal surface as a result of a chemical reaction between the metal atoms and oxidising agent specifically air, molten salts. Yttrium oxide coating of steel comprises of magnetite-ferrous-ferric oxide.

Physical and Thermal properties of Yttrium oxide-

Property

Metric unit

Density

5.01 g/ml

Molecular Weight

225.8

Melting point

2410 deg Celcius

SURFACE PREPARATION

Surface preparation is the most important part in computing the success rate of any coating system. It affects the performance of the coating drastically. Hence it is important for the coating to be very accurately applied to surface otherwise the results of the protective coating will fail.

RESULT AND DISCUSSION

SR NO

VOLTS

AMPS

T1

T2

T3

T4

1

40

0.3

38

35

33

29

2

45

0.36

40

39

36

31

3

50

0.42

41

38

37

33

Calculations-

For Aluminium fin,

1. Reynolds Number:-

Re= (v mf*Lc)/va

Re= 2315.34

2. Nusselt Number:-

Nu=0.615*Re0.466

Nu=22.73

3. Coefficient of Heat transfer:-

h=Nu*Kair/Lc

h=119.3836

4. Fin efficiency=92%

For Yttrium oxide coating fin,

1. Reynolds Number= 2412.53

2. Nusselt Number= 24.95

3. Fin Parameter= 4.65

4. Fin efficiency= 94%

Figure- Comparison of Natural and Coated fin

PARAMETERS

ALUMINIUM

YTTIRUM OXIDE

REYNOLDS NUMBER

2315.3413

2412.53

NUSSELT NUMBER

22.73

24.95

FILM COEFFICIENT

119.3836

141.834

FIN PARAMETERS

5.73

4.65

EFFICIENCY

92%

94%

III. CONCLUSION

This review paper is focussed on achieving higher heat transfer rate and higher film coefficient. The methodology for achieving this objective can be different. The heat transfer rate can be increased by modifying the geometry of the fins as studied in this paper as in the case of automobile radiators. Also the dramatic change in the heat transfer coefficient by notches and thereby the increase in heat transfer rate was observed in this paper. Employing a coating of yttrium oxide increases the fin efficiency and has advantages over the conventional fins.

IV. REFERENCES

[1]  Jose, E., Ramesh, A. V., & P, N. (2015, September 3). Optimization of Circular Shaped Automobile Radiator. International Journal of Innovative Research in Science, Engineering and Technology, 4(Special issue 12), 2015th ser.

[2]Kharche, S. S., & Farkade, H. S. (2012, April). Heat Transfer Analysis through Fin Array by Using Natural Convection. IJETAE, 2(4), issn2250-2459.

[3] A. S, A. A, A. Murugan P, A. S, and A. Kumaur E, \"Experimental Analysis of Fin Coated with Yetrium Oxide to Improve Heat Transfer,\" IRJET, vol. 5, no. Special Issue 8, Jun. 2016.

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