I. INTRODUCTION. Types of Fins:

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International Journal of Advances in Applied Science and Engineering (IJAEAS) ISSN (P): 2348-1811; ISSN (E): 2348-182X Vol.

1 International Journal of Advances in Applied Science and Engineering (IJAEAS) ISSN (P): ; ISSN (E): X Vol. 3, Issue 2, May 2016,19-24 IIST HEAT TRANSFER ANALYSIS ON RECTANGLE AND TRAPEZOIDAL FINS M. VARA PRASAD 1, G.PREM KUMAR 2, T.SAIVENKATESH BABU 3 A.V.S.PRASAD 4,K.APARNA 5 1 Assistant Professor, Dept. of ME, KKR&KSR Inst of. Tech & Sci., Guntur, AP, India 2,3,4,5 UG Students, Dept. of ME, KKR&KSR Inst of. Tech & Sci., Guntur, AP, India ABSTRACT Heat transfer by convection between a surface and the fluid surrounding can be increased by attaching to the surface thin metallic strips called Fins. The heat conducting through solids, walls or boundaries has to be continuously dissipated to the surrounding or environment to maintain the system in a steady state condition. In many engineering applications large quantities of heat need to be dissipated from small area. The fins increase the effective area of the surface there by increasing the heat transfer by convection. In many industrial applications where there is necessity for effective dissipation of heat fins are inadvertently used. The use of fin under such circumstances not only improves the rate of heat transfer rate but also help in optimizing the equipment design with respect of space, cost etc. This paper is aimed at fabrication of trapezoidal and rectangular fins of variable fin cross section. With the help of the experimental setup made under different heat input conditions the temperature variations along the length of the fin is measured. The above methods available to analyze the heat transfer through variable cross section fin viz. analytical, numerical graphical and solutions that can be obtained with the existing packages are compared with the readings taken from the experimental setup. KEYWORDS Heat Transfer, Fins, heat transfer coefficients. I. INTRODUCTION Heat transfer by convection between a surface and the fluid surrounding can be increased by attaching to the surface thin metallic strips called Fins. The heat conducting through solids, walls or boundaries has to be continuously dissipated to the surrounding or environment to maintain the system in a steady state condition. In many engineering applications large quantities of heat need to be dissipated from small area. The fins increase the effective area of the surface there by increasing the heat transfer by convection. The fin is generally used when the convection heat transfer coefficient is low, especially under free convection. In the field of industry the fin is used widely, for instance, in cooling of electronic accessories, motorcycle engine and in air cooling of molecules with in a material. Extended surfaces may exist in many situations but are commonly used as fins to enhance heat transfer by increasing the surface area available for convection. They are particularly beneficial when small, as for a gas and natural convection. Types of Fins: The fins are also referred as extended surfaces. Fins are manufactured in different geometries, depending upon the practical applications. The ribs attached along the length of a tube are called longitudinal fins. The concentric macular discs around a tube are termed circumferential fins. Pin fins or spines are rods protruding from a surface. The fins may be of uniform or variable cross-section. They have many different practical applications, via cooling of electronic components, cooling of motor cycle engines, compressors, electric motors transformers, refrigerators, high-efficiency boiler super heater tubes etc. Solid gas turbines blades often act as fins, conducting heat down their length to a cool disc. Figure 1 Types of Fins 19

While the heat is propagating through fin due to temperature difference existing between the fin surface and environment.

2 Fin is meant for increasing the rate of heat transfer from the base side. In general to improve cooling rate a group of fins called fin array is used on the surface from the base surface the heat enters into the fin by means of conduction. While the heat is propagating through fin due to temperature difference existing between the fin surface and environment. The actual mode of heat transfer involved is convection and radiation to the surrounding and by means of conduction through the fin. Conductions heat transfer through fin occurs in all possible 3 directions. Hence a practical fin problem is so complicated that it involves 3-dimensional conduction associated with the convection and radiation. However the present analysis the conduction through the fin is assure in one dimensional i.e. directional length of the fin only. Further due to low temperature prevailing on the surface of the fin the heat transfer by means of radiation is so small. Hence radiation of the theoretical or numerical methods considers the above assumptions which are far off from the reality due to large thickness of fin for example triangular fin. Multi dimensional analysis cannot be neglected and also when the temperature is neglected and also when the temperature is neglected and also when the temperature is above 150⁰ radiation place a dominant role than convection and is not negligible II. EXPERIMENTAL SETUP switch. By connecting this we can able to measure the temperature at every node. The circuit connection for the experiment is shown in figure.2 Component Description Figure 2 Experimental set up Two aluminium rectangular blocks of 15*5*5cm are taken first and marking is done according to required dimensions. Aluminium rectangular blocks are made into cylinder upto 4cm (base) to insert in heater. Then the remaining blocks are machined into the trapezoidal and rectangular shapes by using shaping machine. The fin edge should be 10mm. The experimental setup consists of two Aluminium rods of 15cm long and 5*5 cm area, voltmeter of 0-300v, ammeter of 0-20amps, temperature indicator degree centigrade, 2-pole 6 way selector switch, 6 way peri connector, k-type thermocouples of 1m length, electronic dimmer 1.5kw or 1kw, band heater 250w, asbestos support pipe for heater, glass wool, heater socket and Al rod 110*50*10mm long for heating test specimen. An Al rod of 15*5*5 cm long is taken and design into required trapezoidal fin and the other into rectangular fin of 110*50*10mm. 4 slots are arranged on the both the fins. First take the trapezoidal fin and from every slot a thermocouple is inserted without any gap. Every thermocouple is connected to the 6 peri connector. Over the fin a band heater is fixed then, it is given power supply. After connecting thermocouples to the peri connector, one end of the peri-connector is connected with wires from there it is connected to the 2-pole 6 way 20 Figure 3 Experimental set up connections The Trapezoidal fin should have 3cm at base and 1cm at tip and the Rectangular fin should have 1cm throughout the fin. After finishing the fin, the cylindrical part of the either rectangular or trapezoidal fin (4cm long) inserted in a MS knob of diameter 4cm. After inserting it a band heater is put around it and is placed in an asbestos shell. The specimen of Al rod is fitted in a

3 rectangular duct in horizontal position. Heater side of the fin is inserted in duct. Other side of the fin is cooled by natural convection A heating element is kept on the horizontal rod, which heats the rod surface. Heat lost from the fin is done by natural convection. Temperature indicator measures the temperature ranging from 0c to 400c.temperature at different points can be measured by using sensors. Sensors used are k-type thermocouple. The heat input to the heater is measured by ammeter which ranges from 0 to 20ams A.C. and a voltmeter ranges from 0 to 300 volts and voltage can be regulated by electronic dimmer of 1.5kw or 1kw. Figure 4 Rectangular and Trapezoidal fins For temperature measurement we use k type thermocouple. A thermocouple is a junction between two different metals that produces a voltage related to a temperature difference. Thermocouples are widely used type of temperature sensor and can also to convert heat into electric power. Thomas johann see beck discovered that when any conductor is subjected to thermal gradient, it will generate a voltage. This is now known as the thermoelectric effect. Thermocouple measures the temperature difference between two points, not absolute temperature. In traditional application, one of the junction- the cold junction- was maintained at a know temperature, while the other end was attached to a probe. Thermocouple may be classified into different types. They are 1) K-type 2) E-type 3) J-type 4) N-type 5) B,R, and S-type 6) T,C, M-type 7) Chromel-gold/iron. K-type thermocouple (chromel-alumel) is most commonly general purpose thermocouple. It is inexpensive available in a wide variety of probes. They are available in the -200c to +1350c range. E-type thermocouple (chromel-constant) has a output (68µv/c) which makes it well suited to cryogenic use. J-type thermocouple (iron-constant) is less popular than type k due its limited range (-40 to 750c). N-type (nicrosil-nisil) are suitable for high temperatures, exceeding 1200c, due to their stability and ability high temperature oxidation. B, R, and S thermocouples use platinum or a platinumrhodium alloy for each conductor. These are among the most stable thermocouples, but have lower sensitivity, approximately 10µv/c, than other types. T-type thermocouple (copper-constant) are suited for measurements in the -200 to 350c range and sensitivity of about 43µv/c. C type thermocouple (tungsten 5% rhenium tungsten 26% rhenium) are suited for measurements in 0c to 2320c range. M-type thermocouple use a nickel ally for each wire and upper temperature is limited to 1400c. Chromel-gold/iron type thermocouples, the positive wire are chromel and the negative wire is gold with a small fraction of iron and has sensitivity around 15 µv/c at low temperature and lowest usable temperature varies between 1.2 and 4.2 k. III. RESULTS AND CONCLUSIONS In this section different temperature readings are taken at different voltages at variable cross sections of the fin and are tabulated. Graphs are drawn for the variation of the temperature with the fin length and variation of the temperature to heat transfer rate. For each heat input of fixed value the temperature along the length of the fin are recorded and tabulated. Nearly 20 such readings are taken at one fixed input with a time interval of 15-20min to reached study state condition. After obtaining satisfactory study state the readings are taken as final readings. However only the last sets of 3 readings taken before attaining steady state are presented for simplicity and convince in present work. 21

4 Figure 5 Variation of temperature with fin length(rectangular-natural) Figure 8 Variation of temperature with heat flow rate (Trapezoidal-natural) Figure 9 Variation of temperature with fin length(rectangular-forced) Figure 6 Variation of temperature with heat flow rate (Rectangular-natural) Figure 10 Variation of temperature with heat flow rate (Rectangular-Forced) Figure 7 Variation of temperature with fin length(trapezoidalnatural) Figure 11 Variation of temperature with fin length (Trapezoidal- Forced) 22

In case of trapezoidal fin, heat transfer coefficient is more at 28 watts in the forced convection.

When compared to both the fins, the heat transfer coefficient is twice in trapezoidal fin than the heat transfer coefficient in the Rectangular fin in both the natural and forced convections.

5 In case of trapezoidal fin, heat transfer coefficient is more at 28 watts in the forced convection. Heat transfer coefficient is more in forced convection than in natural convection in the case of both the fins. When compared to both the fins, the heat transfer coefficient is twice in trapezoidal fin than the heat transfer coefficient in the Rectangular fin in both the natural and forced convections. References Figure 12 Variation of temperature with heat flow rate (Trapezoidal-Forced) From the above experiment the temperature values obtain at different heat inputs are tabulated as shown in the tables1 to 10. The values are plotted considering 2 model graphs one is variation of temperature along fin length at different heat inputs and other one variation temperature at given location for different heat inputs for both the fins and for both natural and forced convections. Figures shows temperature variation along length of fin. It is clear from the figure that along length of fin as we proceed, the temperature goes on decreases. Further the variation of temperature is more at the beginning of the fin rather than at the end because of larger temperature between the fin and surrounding near the base point. It is also noted that it increase heat transfer Q temperature at a given position is increased. Further to note that at high heat flux the variation temperature is more rapid compares to the low heat supply conditions. Figures show the variation of temperature at given location with respect to applied heat at its base point. It is evident from the figures increase in heat transfer Q the temperature at any point exponentially increases. Further the rate of temperature rise is found higher at the base than at the end. Fin with extensions provide near about 5 % to 13% more enhancement of heat transfer as compare to fin without extensions. Temperature at the end of fin with rectangular extensions is minimum as compare to fin with other types of extensions. Choosing the minimum value of ambient fluid temperature provide the greater heat transfer rate enhancement. Temperature variation at the nodes near the base is more when compared to the distant nodes. In case of Rectangular fin, heat transfer coefficient is more at 34.1watts than the other considered heat flow rates from above graphs In case of trapezoidal fin transfer coefficient is more at 40.8watts in the natural convection. 1. Y. Xia and A.M Jacobi, 2004, An exact solution to steady heat conduction I a two-dimensional slab on a one-dimensional fin, international journal of heat and mass transfer.. 2. Haw-long lee, huann-mig chou and yu-ching yang, 2004, the function estimation in predicting heat flux of pin fins with variable heat transfer coefficients, energy conversion and management. 3. Chien-Nan Lin and Jiin-Yuh Jang, 2002, A two-dimensional fin efficiency analysis of combined heat and mass transfer in elliptic fins, international journal of heat and mass transfer. 4. Kang, H. S. ad look, D. C. Jr., 2004, Thermally Asymmetric Annular Rectangular fin Optimization, AIAA Journal of Thermophysics and heat transfer. 5. Burmeister, L. C., 1979, Triangular fin performance by the heat balance integral method, ASME J. of heat trans., vol. 101, pp Abrate, S. and newnham, P., 1995, Finite Element Analysis of Triangular fins 7. Heat mass transfer- yunus A. Cengel Tata McGraw special edition 2007 AUTHORS PROFILE: M. Vara Prasad is an Assistant Professor in the Department of Mechanical Engineering at KKR & KSR s Institute of Technology, Vinjanampadu, Guntur. G.Prem Kumar is pursuing his B. Tech in Department of Mechanical Engineering from KKR & KSR s Institute of Technology, Vinjanampadu, Guntur. T.Saivenkatesh Babu is pursuing his B. Tech in Department of Mechanical Engineering from KKR & KSR s Institute of Technology, Vinjanampadu, Guntur. 23

6 A.V.S.Prasad is pursuing his B. Tech in Department of Mechanical Engineering from KKR & KSR s Institute of Technology, Vinjanampadu, Guntur. K.Aparna is pursuing her B. Tech in Department of Mechanical Engineering from KKR & KSR s Institute of Technology, Vinjanampadu, Guntur. 24

Heat Transfer Enhancement using Herringbone wavy & Smooth Wavy fin Heat Exchanger for Hydraulic Oil Cooling

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