IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 05, 2016 | ISSN (online): 2321-0613
Experimental and Numerical Analysis of Cylindrical Pin Fins having VThread with and without Perforations by Natural and Forced Convection Basavaraj Olekar1 Ganesha T2 Department of Thermal Power Engineering 1,2 Visvesvaray Technical University, PG Studies, Mysuru, Karnataka, India 1,2
Abstract— Currently heat exchangers are used in almost all industrial fields. The heat exchanger design greatly affects the design of the entire system or process in which they are applied. Various factors influence the design of heat exchanger, major things are heat transfer rate, pumping power needs to run the heat exchanger and also heat exchanger size, weight, and production cost. The conduction losses are minimized by using higher thermal conductivity materials, radiation losses are less concern for heat exchangers operating under moderate temperature. Whereas the intensity of heat transfer by convection is the dominant challenge particularly on the gas side for the design of heat exchangers. From Newton’s law of cooling heat transfer rate mainly depends on Surface area and heat transfer coefficient. Heat transfer co-efficient can’t be changed but it can changed due increasing surface area by altering original shape such as pin fins. The main aim of this study is to find out the most effective pin fin from V-threaded pin fins having with and without perforations in inline and staggered arrangement. Trials were conducted for varying Reynolds number and results were found out respectively for each pin fins. Key words: V-Thread Pin Fin, Perforations, Staggered Arrangement, Inline Arrangement, Heat Transfer Coefficient, Nusselt Number, Reynolds Number
either a cylindrical or rectangular base, a pin fin is a circular or other shaped body fixed perpendicular to a wall with the transfer fluid passing in cross flow over the body. II. GEOMETRY OF PIN FIN USED In this experiment different test model is used for the calculation of natural and forced calculation such as VThreaded pin fins with and without perforations in inline and staggered patterns are used which shown below
Fig. 1: V-Thread pin fins with perforations in staggered pattern
I. INTRODUCTION Heat Sinks with fins are normally used to enhance the heat transfer rate in various industrial applications such as cooling of an Engine, Electronic components, and trailing edge of Gas turbine. Fins are best solution because of their less cost and trouble free operation. The weight and size of equipment are the most important parameters of design. In these days the general trend is to use compact systems especially in electronic devices, which leads to higher packing density of systems causing higher heat production. In convection heat transfer mechanism, there is possible ways to increase heat transfer is increase in temperature difference between fluid and surface of the body or increases in heat transfer coefficient or increase in surface area across which convection heat transfer occurs. Augmented or extended surface are generally known as pin fin are commonly used extended surface exchangers, to reduce the size of heat exchangers pin fins are used to enhance the surface area and the heat transfer rate between surface of the body and the surroundings. Pin fins are broadly utilized as a part of heat exchanging body which results in enhances the heat exchange between the surface of the body and ambient fluid. Different types of heat exchanger pin fins, varying from relatively simple shapes, for examples, dropped shape, square, rectangular, barrel shaped, annular, or pin fins of various geometries has been utilized. One of the commonly utilized fins is the pin fin; these fins may protrude from
Fig. 2: V-Thread pin fin with perforations in inline pattern
Fig. 3: V-Thread pin fins without perforations in staggered pattern
Fig. 4: V-Thread pin fin without perforations in inline pattern
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Experimental and Numerical Analysis of Cylindrical Pin Fins having V-Thread with and without Perforations by Natural and Forced Convection (IJSRD/Vol. 4/Issue 05/2016/377)
III. EXPERIMENTAL TEST RIG
Vf Af Av C As
Volume flow inside the duct Area of wetted perimeter Cross section area of V-thread Pitch length of V-thread Cross section area of Square thread Table 1: Symbols and Abbreviations IV. FORMULAE USED
Various governing equations used in the experiment are as follows:
Fig. 1: Experimental Setup Following are the main components of Experimental Setup which shown in Fig 1. 1) Air Blower 2) Air duct 3. Test model 3) Heater Control 4) Air Blower Control 5) Current Indicator 6) Voltage Indicator 7) Temperature Indicator Test model is placed in air duct where one end connected suction side of air blower and other end is open to the atmosphere. Heater is placed below the test model and glass wool is placed in between Air duct and heater which acts as a insulator. Thermocouples are connected bottom and top sides of each pin fins and inlet and outlet sides of the air duct. Constant heat flux is provided to the heater plate by fixing the constant voltage and current. Continuous increase in temperature of the base plate of the pin fin, at some period temperature attains constant. Took the all temperature readings for calculation for natural convection. For forced convection air is supplied at constant velocity at constant heat flux to the base plate at some period temperature of base attains constant continuously. Taken the readings of velocity of air and temperature for the calculation of forced convection. Repeat the experiment by varying the velocity of air. A. Symbols and Abbreviations Symbols St Sl c,n U Ts Ta Tm Dh Nf Ap hf Lp
Abbreviations Pitch transverse to flow Pitch along the flow Constant values for number of rows of fins Free stream velocity of air just before fins Fin body surface temperature Ambient temperature Mean temperature Hydraulic diameter Number of fins Area of fins Height of fin Perimeter length of fin
2
∏
× (dp − 0.9381 × P) (1.1) At =Cross section area of thread pin fin, dp =Pitch diameter of V-thread, P =Pitch distance The total volume of fluid can flow inside the duct where the pin fins are placed. Vf = BHL − Nf × Av × hf (1.2) Vf = Volume of fluid, B=Breadth of duct, H=Height of duct, L=Length of duct. Nf = Number of fins, hf =Height of fin Air is supplied to duct from blower, the maximum contact surface between the air media and surface of the pin fins is the Wetted surface area Af of V-thread pin fin is given Af = 2(B + H)L+Nf (Lp hf − 2At ) (1.3) Af =Contactsurface area Lp =Perimeter length of pin fin Hydraulic diameter of duct Dh is 4×Vf Dh = (1.4) At=
4
Af
A. Natural Convection Grashof’s number (Gr ) is g×β×∆T×D 3
h Gr = (1.5) ν2 Where, ∆T = Ts − T∞ Ts =Surface temperature of pin fin, T∞ =Ambient temperature. ν=Kinematic viscosity The Relationship of Nusselt number is Nu = C × (Gr Pr )n (1.6) Pr =Prandtl number Co-efficient of Heat transfer is Nu×k h= (1.7)
Dh
B. Forced Convection Array of fins inside the duct, St 2
(St -D) < 2√( ) − Sl 2 -2D 2
Maximum velocity air in the duct is, S Vmax = t x U St −D
Reynolds number is given by the relation is, V D Re= max h ϑ Nusselt number is given by Nu=C (Re)n Co-efficient of Heat transfer is Nu×k h= Dh
(1.8) (1.9) (1.10) (1.11) (1.12)
V. RESULTS AND DISCUSSION Heat transfer coefficient is calculated for different test model for Natural convection by providing constant heat flux to base plate.
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Experimental and Numerical Analysis of Cylindrical Pin Fins having V-Thread with and without Perforations by Natural and Forced Convection (IJSRD/Vol. 4/Issue 05/2016/377)
Effect of Heat Transfer Co-efficient in Natural Convection.
Fig. 6: Heat Transfer Co-efficient for different test model for Natural Convection Calculated the different parameter such as Reynolds number, Nusselt number, and heat transfer coefficient for different test section in forced convection Type of U in h in Re Nu pattern m/s W/m²K 2 31352.1 174.31 46.0266 V-Thread pin 3 49041.9 245.02 61.632 fin in staggered 4 66295.5 313.65 80.213 pattern 5 85312.5 368.74 91.3698 2 31862.2 176.88 47.178 V-Thread pin 3 50127.6 243.25 62.0862 fin with 4 68274.5 319.87 81.08 perforations in staggered 5 87781.1 374.35 94.94 pattern 2 30338 169.25 43.167 V-Thread pin 3 47455.7 226.58 56.9012 fin in inline 4 64151.2 290.20 72.2054 pattern 5 82553.1 347.98 86.0489 V-Thread pin 2 30783.1 171.04 44.9496 fin with 3 48158.1 230.06 60.4918 perforations 4 65524.3 294.66 76.2901 in inline 5 77381.5 350.8 89.944 pattern Table 1: Heat transfer coefficient is calculated for different test model for forced convection by providing constant heat flux to base plate and varying air velocity 2m/s, 3m/s, 4m/s and 5m/s.
Fig. 7: Effect of heat transfer co-efficient & Nusselt number on V-thread pin fins in inline and staggered pattern
Fig. 8: Effect of Reynolds number & Nusselt number on Vthread pin fins in inline and staggered pattern In this experiment Aluminium material of base plate and pin fins are used for both free and forced convection. In natural convection heat transfer co-efficient varied from 7 to 8 W/m²K. In forced convection supplying air velocity with 2 m/s, 3 m/s, 4 m/s and 5 m/s which affects the Reynolds number, Nusselt number, and heat transfer coefficient. Maximum heat transfer co-efficient varied from 47.17 to 94.94 W/m²K. VI. CONCLUSION This Experimental and numerical study the effects of various geometry of pin fin having with and without perforations in staggered and inline arrangement and sizes of pin fin on heat transfer rate. By altering the little change in its geometry such as V-Thread on cylindrical pin fin
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Experimental and Numerical Analysis of Cylindrical Pin Fins having V-Thread with and without Perforations by Natural and Forced Convection (IJSRD/Vol. 4/Issue 05/2016/377)
which leads to increase in the cross sectional area and turbulence. The effects of geometry and arrangements on flow characteristics and Thermal performance can be determined. From this experiment finally we concluded that V-Thread pin fin with perforations in staggered pattern shows higher heat transfer rate among each others. REFERENCES [1] Javid Siddiqui, A.V.Gadekar, “A review paper on CFD Simulation of square threaded & helical twisted pin fin array in a rectangular channel to enhance heat transfer”, International Journal of Science and Research, ISSN 2319-7064. 2013. pp 365-372. [2] Amol B. Dhumne, Hemant S. Farkade, “Heat Transfer Analysis of Cylindrical Perforated Fins in Staggered Arrangement”. International Journal of Innovative Technology and Exploring Engineering, ISSN: 22783075, Vol-2, Issue-5, April 2013, pp 225-230. [3] Akshaya. A.Shelar, Akshaya.B.Poman, Subodh U.Salunkhe, Pratik.M.Phadtare, “Thermal analysis of fin using different materials and forms”, International Journal for Scientific Research & Development, ISSN: 2321-0613 Vol- 3, 2015. pp 352-359. [4] J.Khalil Basha, Rajakrishnamurthy, S.suthagar, T.Gopinath, “Experimental study of the characteristics of various types of fins using forced convection heat transfer”, International Journal of Innovative Science, Engineering & Technology, ISSN: 2348-7968.Vol-2, issue 6,June 2015. Pp 354-361. [5] Ganesha Murali J. Subrahmanya S Katte, “Experimental Investigation of heat transfer enhancement in radiating pin fin”, Jordan Journal of Mechanical and Industrial Engineering, ISSN: 19956665, Vol- 2, No- 3, Sep 2008. pp 163-167. [6] M.Dogen, M.Sivrioglu, “Experimental investigation of mixed convection heat transfer from longitudinal fins in a horizontal rectangular channel”, International journal of heat and Mass transfer 53 (2010), pp 2149-2158 [7] Md.Farhad Ismail, M.O.Reza, M.A.Zobaer. Md.Ali, “Numerical investigation of turbulent heat conduction from solid and longitudinally perforated rectangular fins”, ELSEVIER, 2013, pp 497-502 [8] H.Azarkish, S.M.H. Sarvari, A behzadmehr, “optimization design of a longitudinal fin array with convection and radiation heat transfer using a genetic algorithm”. International Journal of thermal Sciences. Vol-49. ELSEVIER, 2010. pp 589-602. [9] N.B.Totala, V.P.Desai, Pratik Gawade, Nikhil Kakade, Ananth Paralkar,Arpit banerjee,Shreenath Agarwal, “Manufacturing and comparative analysis of threaded tube heat exchanger with straight tube heat exchanger”, International Journal of Engineering and Science, ISSN: 2278-4721 Volume 4, Issue 7, July 2014, pp 77-85.
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