Experimental Analysis on Pin Fin Heat Exchanger Using Different Shapes of the Same Material

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1 DOI / ISSN IJESC Research Article Volume 6 Issue No. 4 Experimental Analysis on Pin Fin Heat Exchanger Using Different Shapes of the Same Material Zaharaddeen Aminu Bello 1, Pankaj Rao 2, Nabil Isyaku mu az 3, Umar Gali Ahmad 4, Anas Abdullahi Muhammad 5, Sulaiman Muhammad Musa 6 Department of Mechanical Engineering 1, 2,3,5,6, Department of Physics 4 Jodhpur National University, Rajasthan, India zabgaya@gmail.com 1, pankajarao2308@gmail.com 2, nabilisyaku@gmail.com 3, umarghali2008@gmail.com 4, mohdanasabdullahi1@gmail.com 5, sulaiman.muhammad63@gmail.com 6 Abstract: In this paper, the heat transfer rate, effectiveness, efficiency, Nusselt number, Reynolds number and temperature distribution of various pin fin shape (morphology) of the same material (Aluminum) are analyzed by design of fin with various extensions of circular extension, triangular extension, and square extensions. In the case of free convection, the heat transfer rate of circular is 0.996W with the effectiveness, efficiency and Nusselt number of 32, 95.4% and 4.55 respectively. In the case of triangular pin fin the heat transfer rate is with the effectiveness, efficiency and Nusselt number of 45, 96.8%, and respectively. For square pin fin the heat transfer rate is with the effectiveness, efficiency and Nusselt number of 33, 97.7%, and respectively. In the case of force convection, the heat transfer rate of circular is 1.128W with the effectiveness, efficiency, Nusselt number and Reynolds number of 31, 91%, 9.09 and respectively. In the case of triangular pin fin the heat transfer rate is with the effectiveness, efficiency Nusselt number and Reynolds number of46, 95.5%, and respectively. For square pin fin the heat transfer rate is 0.729with the effectiveness, efficiency Nusselt number Reynolds number of 33, 96.8%, 24.75, and respectively. In this thermal analysis, temperature variations with respect to distance at which heat flow occur through the fin is analyzed. Extensions on the finned surfaces is used to increases the surface area of the fin in contact with the fluid flowing around it and heat transfer coefficient. So, as the surface area increase the more fluid contact to increase the rate of heat transfers from the base surface as compare to fins of different shape. On comparison, circular extensions provide on fin gives the greatest heat transfer than that of other extensions having the same length but different cross sectional area. The effectiveness of triangular fin is greater as compare to others followed by square and lastly with circular fin. But square fin provided greatest efficiency then others fins. Key Words: Effectiveness, Nusselt number, Reynolds number efficiency and temperature distribution. INTRODUCTION A heat exchanger is a device to transfer heat from a hot fluid to cold fluid across an impermeable wall. Fundamental of heat exchanger principle is to facilitate an efficient heat flow from hot fluid to cold fluid. This heat flow is a direct function of the temperature difference between the two fluids, the area where heat is transferred, and the conductive/convective properties of the fluid and the flow state. This relation was formulated by Newton and called Newton s law of cooling, which is given in Equation (1.1) Q = h A T (1.1) Where h is the heat transfer coefficient [W/ K], where fluid s conductive/convective properties and the flow state comes in the picture, A is the heat transfer area (, and T is the temperature difference (. Heat exchangers are one of the vital components in diverse engineering plants and systems. So the design and construction of heat exchangers is often vital for the proper functioning of such systems. It has been shown in [Barron, 1985] that the low temperature plants based on Linde Hampson cycle cease to produce liquid if the effectiveness of the heat exchanger is below 86.9%. On the other hand in aircrafts and automobiles, for a given heat duty, the volume and weight of the heat exchangers should be as minimum as possible. Most of the engineering problems require high performance heat transfer components with progressively less weights, volumes, accommodating shapes and costs. Extended surfaces (fins) are one of the heat exchanging devices that are employed extensively to increase heat transfer rates. The rate of heat transfer depends on the surface area of the fin. In this the heat transfer rate and efficiency for circular, rectangular and square fins were analyzed for same environmental conditions. International Journal of Engineering Science and Computing, April

2 Figure.1.1shows the basic heat transfer mechanism Figure 0.1: Basic heat transfer mechanism. Types of extension provided on fin such as (a) Rectangular extensions, (b) Trapezium extensions, (c) Triangular extension, and (d) Circular Segmental extension NOMENCLATURE A= cross sectional area of fin, P= circumference of the fin, m L= length of the fin, m = Base temperature of the fin Duct fluid temperature, Diameter of orifice, m = coefficient of discharge of orifice Dynamic viscosity, = Specific heat of air, Kinematic viscosity, = thermal conductivity of air, Manometer difference of water, m Volume expansion coefficient, /k = Velocity of air in duct, m/s Volume flow rate of air, = velocity of air at mean film temperature m/s Heat transfer coefficient, Thermal conductivity of the fin material, w/mk Average fin temperature, = mean film temperature, = Density of water, Kg/ = Density of air Kg/ Diameter of pin fin, m International Journal of Engineering Science and Computing, April

Experimental Setup We designed and manufactured the experimental setup for current study. Following figure shows the test rig used for the study.

3 Experimental Setup We designed and manufactured the experimental setup for current study. Following figure shows the test rig used for the study. Figure 1-1: Test rig Apparatus Specifications: Diameter of pin fin, d = 12mm for circular fin, 14.6mm for triangular fin and 12mm for square fin 5 numbers of thermocouples position along the length of Aluminum Fin is screwed in heater which is heated by a band heater Duct is 1 100mm cross section, 1000mm long connected to suction side of blower. F.H.P centrifugal blower with orifice and flow control valve on discharge side Orifice diameter 22mm, coefficient of discharge Length of pin fin, L = 102mm. Thermal conductivity of fin material (Aluminum) = 232 W/mK Multichannel digital temperature indicator Dimmerstat for heat input control0-230v, 2 Amps. Water manometer connected to orifice meter Voltmeter = 0 2 V. Ammeter = 0 1 Amps. International Journal of Engineering Science and Computing, April

Figure 1-2: Circular, Triangular and Square fins THEORY Let A= cross sectional area of fin, P= circumference of the fin, m L= length of the fin, = 0.

material, w/mk = 232w/mk for aluminum This is the equation for temperature distribution along the length of the fin.

Heat is conducted along the fin and also lost to the surroundings.

4 Figure 1-2: Circular, Triangular and Square fins THEORY Let A= cross sectional area of fin, P= circumference of the fin, m L= length of the fin, = 0.102m = Base temperature of the fin Duct fluid temperature, Figure 0-1: Assuming tip to be insulated Heat transfer coefficient, Thermal conductivity of the fin material, w/mk = 232w/mk for aluminum This is the equation for temperature distribution along the length of the fin. Temperature and will be known for the given situation and value of h, depends upon mod of convection i.e. natural or force. Heat is conducted along the fin and also lost to the surroundings. Applying first law of the thermodynamics to control volume along the length of the fin at a station which is at length from the base, Heat transfer rate is given by, Efficiency is given by For insulted tip effectiveness of the fin: Where, With boundary conditions of International Journal of Engineering Science and Computing, April

5 NUSSELT NUMBER Temperature (oc) Temperature (oc) Result and Discussion 60 Free convection Temperature Distribution for Three fins Circular fin Triangular fin Square fin Distance (mm) Force convection Temperature Distribution for three fins Circular fin Triangular fin Square fin Distance (mm) 9.2 NUSSELTS NUMBER VS REYNOLDS NUMBER GRAPH FOR CIRCULAR FIN REYNOLDS NUMBER International Journal of Engineering Science and Computing, April

6 EFFECTIVENESS NUSSELT NUMBER NUSSELT NUMBER 26.0 NUSSELT NO. VS REYNOLDS NO. FOR TRIANGULAR FIN REYNOLDS NUMBER 25.0 NUSSELT NO. VS REYNOLDS NO. FOR SQUARE FIN REYNOLDS NUMBER EFFECTIVENESS GRAPH FREE CONVECTION TRIANGULAR FIN 40 CIRCULAR FIN SQUARE FIN FINS International Journal of Engineering Science and Computing, April

7 EFFECTIVENESS EFFECTIVENESS GRAPH FORCE CONVECTION TRIANGULAR FIN CIRCULAR FIN SQUARE FIN FINS CONCLUSION Experimental Analysis to determine the effectiveness, efficiency, Heat transfer rate, Heat transfer coefficient, Nusselt number and Reynolds number for three fin pins with different shapes of the same length. The temperature distribution along the fin length has negative gradient i.e. Temperature reduces as along the fin length. The theoretical values of the temperatures for all three fins are slightly greater than the practical values because of heat lost by radiation. Consideration about insulated tip is true that is as fin tip temperature is approximately equal to the ambient temperature, fin tip can be considered as insulated. Also the temperature distribution curves for both experimental values and theoretical values have the same nature. The heat transfer rate for free convection has greatest value in the case of circular fin, followed by triangular fin and least is square fin, but in case of force convection circular fin has the greatest value fallowed by square fin and last is triangular fin. The triangular fin has the highest effectiveness 45 to 46 for both free and force convection cases, followed by the square fin and then the circular fin, but the square fin is the most efficient of 96.8 to 97.7, and triangular fin is more efficient then the circular fin. Journal of Engineering and Innovative Technology (IJEIT), 7, 2013, N. Sahiti, F. Durst, A. Dewan, Heat transfer enhancement by pin elements, International Journal of Heat and Mass Transfer, 48, 2005, D.Roncati, Iterative calculation of the heat transfer coefficient, Progettazione Ottica Roncati, David Ramthun, An Experimental Study of a Pin-Fin Heat Exchanger Naval Postgraduate School, U. Akyol, K. Bilen, (2006) Heat transfer and thermal performance analysis of a surface with hollow rectangular fins, Applied Thermal Engineering, 26, pp References 1. Ito, M., Kimura, H. And Senshu, T. (1977) Development of high efficiency air-cooled heat exchanger, Hitachi Review, Vol. 26, pp U S Gawai, Mathew V K, Murtuza S D, Experimental Investigation of Heat Transfer by PIN FIN International International Journal of Engineering Science and Computing, April

Heat Transfer Enhancement Through Perforated Fin

IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-issn: 2278-1684,p-ISSN: 2320-334X PP. 72-78 www.iosrjournals.org Heat Transfer Enhancement Through Perforated Fin Noaman Salam, Khan Rahmatullah,