PERFORMANCE ANALYSIS ON DOUBLE PIPE HEAT EXCHANGER USING WIRE COILED AND PIN WIRE COILED TURBULATOR INSERTS

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1 June 217 IJIRT Volume 4 Issue 1 ISSN: PERFORMANCE ANALYSIS ON DOUBLE PIPE HEAT EXCHANGER USING WIRE COILED AND PIN WIRE COILED TURBULATOR INSERTS S.Shanmugapriya 1, M.Ganesh karthikeyan 2, Dr.M.Prabakar 3 and S. Senthilkumar 4 1 Thermal Engineering, TRPEC, Trichy, India 2,3,4 Mechanical Engineering, TRPEC, Trichy, India Abstract The heat exchanger is an important device in almost all of the mechanical industries as in case of process industries it is key element. Thus from long time many researchers in this area are working to improve the performance of these heat exchangers in terms of heat transfer rate, keeping pressure drop in limit by using various techniques. This project work deals with of such techniques keeping focus on passive augmentation techniques used in heat exchangers. Here the wire coiled turbulator and pin wire coiled turbulator are used to enhance the heat transfer rate in the double pipe heat exchanger by changing the flow of a liquid. Tests to be conducted at various mass flow rates by controlling the flow control valve, for the following valve opens (25%, 5%, 75%, 1% valve open). Results may indicate that the heat transfer rate enhances inversely with the pitch of the wire coiled turbulator and directly proportional to the mass flow rate. Index Terms Double pipe heat exchanger, Plain, Wire coiled turbulator inserts, Pin wire coiled turbulator inserts, Pressure drop, Friction Co-efficient. I. INTRODUCTION Heat transfer can be increased by active and passive techniques. In the active techniques external power is required to increase the heat transfer. For the passive technique method no external energy is required for the enhancement of heat transfer. Wire coiled coil matrix turbulator (WCCMT), taper wire coiled coil matrix turbulator, and pin wire coiled turbulators are falls under the category of passive techniques. In this experimental work, turbulators are used to increase the heat transfer. Three different types of wire coiled turbulators (shown in figs.) are used to increase the heat transfer. Due to the insertion of turbulators there is increase in pumping power due to the pressure drop. But when compared to enhancement in heat transfer the increase in pumping power is very less. II. TURBULATORS Heat exchangers with the convective heat transfer of fluid inside the tubes arefrequently used in many engineering applications. In order to augment heat transfer andincrease the system efficiency, turbulators with different geometries have been developedand many experimental investigations have been conducted to determine theirthermodynamic characteristics. The turbulators, when they are inserted into the flow, provide redevelopment ofthe boundary layer and increase the heat transfer surface area and cause enhancement ofconvective heat transfer by increasing turbulence. Thus, more compact and economicheat exchanger with lower operation cost can be produced. On the other hand, when thesedevices placed into the flow they deteriorate the flow. Major Applications for Turbulators: 1. Oil Coolers 2. Highly viscous liquids 3. Gas or Air heaters/coolers 4. Static Mixers 5. Falling Film Evaporators 6. Inline reactors 7. Prevention of scale formation on tube. a) Wire coiled and Pin Wire coiledturbulators: The wire coiled turbulator is the old war horse of the Turbulator world and ofcourse we make them in large quantities. This type is also featured in the HTRI softwareas a generic product so customers can do their own design. (A type of wire Turbulator isalso featured but as a proprietary product of Calgavin and customized as per theirconfigurations.) We can give all standard and a large range of custom pitches and offerthem in almost all materials. While in most cases the flexible wire type is a preferredoption, in the case IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 188

2 June 217 IJIRT Volume 4 Issue 1 ISSN: of retrofitting, where there is a lower flexibility with regards toredesigning the existing equipment, this is very often a low pressure drop reasonableefficiency solution. So that I have selected wire coiled and pin wire coiled turbulatorsformy research work. d) Pin wire coiled turbulator: b) Specifications of Wire Coiled Turbulator: Fig. 5 Pin wire coiled turbulator for 15mm pitch Fig. 1.Wire Coiled Turbulator L = length of the wire coiled turbulator(15 mm) P = pitch, 1mm, 15mm) D1 = Outer Diameter of the wire coil turbulator(18mm) D2 = inner Diameter of the wire coil turbulator.(6mm) c) Wire Coiled Turbulator for Various Pitch: Fig. 2 Wire coiled turbulator for 5mm pitch Fig. 3 Wire coiled turbulator for 1mm pitch Fig. 4 Wire coiled turbulator for 15mm pitch III. EXPERIMENTAL SETUP AND PROCEDURE a) Double pipe heat exchanger: A simplest form of heat exchanger is double pipe Heat Exchanger where two pipes are constructed one inside the other. One fluid flows in each of the pipes and gets heated or cooled as per the application. The major use of double pipe heat exchangers is for sensible heating or cooling of process fluids where small heat transfer areas (5 m2) are required. This configuration is also suitable when one or both fluids are at high pressure. Double pipe heat exchangers Can operate between.5kw~15kw. Double pipe heat exchangers have an outer pipe I.D of 5 to 4 mm at a nominallength of 1.5 to 12. m per hairpin. The O.D of the inner tube may vary between 19 to 1 mm. b) Reasons for selection: The heat transfer coefficient and pressure drop are the most significant variables in reducing the size and cost of a heat exchanger. An increase in the heat transfer coefficient generally leads to another advantage of reducing the temperature driving force, which increases the second law efficiency and decreases entropy generation. Thus, research in this area captivated the interest of a number of researchers. So, the double pipe heat exchanger is selected. The experimental setup is shown in fig. 6. It consists of hot and water reservoir, Rota meter, thermocouples, pumps, flow control valves and two concentric tubes in which hot water flows through the inner tube (Copper tube, d= 33 mm, L= 155 mm) and cold water flows in counter flow through annulus.the outer tube is made of MS steel and it s insulated with the asbestos IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 189

3 June 217 IJIRT Volume 4 Issue 1 ISSN: rope to minimize the heat loss with surroundings. Six RTD Pt 1 type temperature sensors with ±.1 C accuracy are used to measure the inlet and outlet temperature of the hot and cold water.the water is heated using 3 KW water heaters in the hot water tank and the desired temperature controller. The water at constant temperature is taken from the tank using the centrifugal pump to the test section. c) Experimental procedure: The hot and cold water tank is filled with the required level water. The heater is switched on through the main power supply of the setup. The RTD (Relational Temperature Detector) is set with the required temperature of hot water inlet. Fig. 6Experimental setup In this experiment there are two flow control valves are used in that two initially one flow control valve is closed and another one is open this allow the fluid to fill in the container by using this we measure the flow rate. After that both the flow control valves are open the cold water is entered into the inner pipe of the setup. The hot water is entered into an outer tube of the heat exchanger through flow control valve. The sensor measures the hot water and inlet and outlet temperature and indicates in the temperature indicator. After taking the required readings the gate valves is adjusted to the initial position. Finally the heater and main power is switch OFF and the water is drained. d) Specifications: (1) Inner of the double pipe: i.material - Copper ii.inner diameter - 33 mm iii.outer diameter - 38 mm iv.length mm (2) Outer pipe of the double pipe: i.material - Mild steel ii.inner diameter mm iii.outerdiameter mm iv.length mm v.insulation material - Asbestos (3) Heater: i.capacity of heating coil 1W ii.number of heating coil - 3 no s (4) Pump: i.type - Centrifugal pump ii.power - ½ HP iii.number of pumps - 1no s iv. Cold water pump - 1no s e) Digital temperature indicator: i. Sensor - RTD-Pt 1 ii. Number of sensors - 6 no s iii. Range C iv. Display unit - Digital LED) v. Number of Channel - 1 f) Digital temperature controller: i. Sensor - k-type ii. Number of sensors - 6 no s. iii. Range - -4 C IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 19

4 June 217 IJIRT Volume 4 Issue 1 ISSN: iv. Display unit -Digital (LED) g) Hot and cold water tank: i. Length -.47 m. ii. Breadth -.47 m. iii. Height -.75 m.2 liter container(used for drinking water storage) PVC pipe.5 (length~1m) Funnel (for feed input) Rubber or plastic cap (to seal container) Cap.5 (to seal effluent pipe) Pipe (for gas output, was used LPG pipe) (1.5m) Tyre tube (for store the biogas) T- junction M seal Black paint (to absorb heat energy from surroundings) IV. DATA REDUCTION EQUATIONS 1. The average inside heat transfer coefficient and the mean Nusselt number for the plain and the wire coiled matrix turbulator cases are evaluated as: Q = m Cp (T T i) = h i A i ( T i) m Where, A i = π Di L ( T i) m = (T MW-T i) (T MW-T i) ln (T MW-T i) (T MW-T i) T MW=T W/2 2. The average inside heat transfer co efficient hi = (Q / A i ( T i)m) 3. Nusseltnumber, friction factor, pressure drop equations (plain tube): Δp = 4fLVc 2 2D 2 4. Nusselt number, friction factor, pressure drop equations (Plain tube with coiled turbulators): Δp = 4fLVc 2 2D 2 V. RESULT AND DISCUSSION The present experimental results on heat transfer and friction characteristics in a plain tube are first validated in terms of Nusselt number and friction factor. It is important to compare the experimental results obtained for the fully developed turbulent flow for various turbulator inserts. At 25% valve open, with a pitch of 5 mm, the wire coiled turbulators without bonding have resulted in almost 2 times enhancement when compared with plain tube. On the other hand, for pitches of 1 mm and 15 mm the enhancement were 1.75 times and 1.5 times, respectively. At 5% valve open, with a pitch of 5 mm, the wire coiled turbulators without bonding have resulted in almost 1.83 times enhancement when compared with plain tube. On the other hand, for pitches of 1 mm and 15 mm the enhancement were 1.66 times and 1.33 times, respectively. At 75% valve open, with a pitch of 5 mm, the wire coiled turbulators without bonding have resulted in almost 1.75 times enhancement when compared with plain tube. On the other hand, for pitches of 1 mm and 15 mm the enhancement were 1.63 times and 1.37, respectively. At 1% valve open, with a pitch of 5 mm, the wire coiled turbulators without bonding have resulted in almost 1.63 times enhancement when compared with plain tube. On the other hand, for pitches of 1 mm and 15 mm the enhancement were 1.45 times and 1.27 times, respectively. At 25% valve open, with a pin wire coiled turbulator without bonding have resulted in almost 2.5 times enhancement when compared with plain tube. At 5% valve open, with a pin wire coiled turbulator without bonding have resulted in almost 2.16 times enhancement when compared with plain tube. At 75% valve open, with a pin wire coiled turbulator without bonding have resulted in almost 2 times enhancement when compared with plain tube. At 1% valve open, IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 191

5 Theoretical Heat transfer coefficient friction factor Exp Heat transfer co-efficient hexp (W/m2K) friction factor June 217 IJIRT Volume 4 Issue 1 ISSN: with a pin wire coiled turbulator without bonding have resulted in almost 1.81 times enhancement when compared with plain tube. On other hand the Nusselt number, friction factor, and pressure drop are indirectly proportional to the pitch. wire coiled turbulator while compare with other turbulators. Vs Exp friction factor Plain Vs Exp Heat transfer co-efficient Plain Fig 7 Reynolds number Vs Experimental Heat transfer co-efficient. Vs Theoretical Heat transfer co-efficientplain Fig 8 Reynolds number Vs Theoretical Heat transfer co-efficient. Figures 7 and 8 shows variation of Nusselt number with Reynolds number for the different cases like plain tube, wire coiled turbulator, taper wire coiled turbulator, and pin wire coiled turbulator. It is observed that the heat transfer rate is higher for pin Fig 9 Reynolds number Vs Experimental friction factor Vs Theoretical friction factor Pin Wire Coiled Turbulator Plain Pin Wire Coiled Turbulator Fig 1 Reynolds number Vs Theoretical friction factor. Figures 9 and 1 shows variation of friction factor with Reynolds number for the different cases like plain tube, wire coiled turbulator, taper wire coiled turbulator,and pin wire coiled turbulator. It is observed that the friction factor is higher for pin wire coiled turbulator while compare with other turbulators. IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 192

6 Theoretical Pressure Drop ( P) (bar) Exp Pressure Drop ( P) (bar) June 217 IJIRT Volume 4 Issue 1 ISSN: Vs Exp Pressure Drop Plain Fig 11.Reynolds number Vs Experimental Pressure drop. Figures 11 and 12 shows variation of pressure drop with Reynolds number for the differentcaseslike plain tube, it is observedthat the pressure dropis higher for pin wire coiled turbulator while compare with other turbulators. Vs Theoretical Pressure Drop Plain Fig 12 Reynolds number Vs Theoretical Pressure drop VI. CONCLUSION Experimental data obtained were compared with those obtained from the theoretical data of plain tube. The maximum Nusselt number for pitch 5 mm was obtained which indicates that heat transfer coefficient increases with the decreasing pitch of the turbulator. The friction factor also increases with the decreasing pitch. The above findings indicate that the use of wire coiled coil matrix turbulator and pin wire coiled turbulators in the tube-in-tube heat exchanger enhances the heat transfer with considerable pressure drop. The experimental data which indicates the heat transfer rate of pin wire coiled turbulator is higher than the wire coiled turbulators. REFERENCES [ 1 ] P. Murugesan, K. Mayilsamy, S. Suresh, P.S.S. Srinivasan,Heattransfer and pressure drop characteristics in a circular tube fitted with and without V-cut twisted tape insert: International Communications in Heat and Mass Transfer 38(211) [ 2 ] PaisarnNaphon, TanaponSuchana,Heat transfer enhancement andpressure drop of the horizontal concentric tube with twisted wires brush inserts:international Communications in Heat and Mass Transfer 38 (211) [ 3 ] Halit Bas, VeyselOzceyhan,Heat transfer enhancement in a tube withtwisted tape inserts placed separately from the tube wall: Experimental Thermaland Fluid Science 41 (212) [ 4 ] PaisarnNaphon,Second law analysis on the heat transfer of the horizontalconcentric tube heat exchanger: Heat and Mass Transfer 33 (26) [ 5 ] PaisarnNaphon,Effect of coil-wire insert on heat transfer enhancement andpressure drop of the horizontal concentric tubes: International Communications inheat and Mass Transfer 33 (26) [ 6 ] Suresh S., M. Chandrasekar, S. Chandra Sekhar,(21) ExperimentalStudies On Heat IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 193

7 June 217 IJIRT Volume 4 Issue 1 ISSN: Transfer And Friction Factor Characteristics Of Cuo/Water NanoFluid Under Turbulent Flow In A Helically Dimpled, ExperimentalThermal and Fluid Science, page no [ 7 ] Juin Chen a, Hans Muller-Steinhagen b, Geoffrey G. Duffy a, (21) Heat Transfer Enhancement in Dimpled s, Applied Thermal Engineering,page no [ 8 ] Pedro g, Vicente, Alberto Garcia, Antonio Viedma, (21) Heat Transfer And Pressure Drop For Low Reynolds Turbulent Flow In Helically Dimpleds,International journal of Heat and Mass Transfer, page no [ 9 ] Suresh S., K.P. Venkitaraj, P. Selvakumar, (21) Comparative Study OnThermal Performance Of Helical Screw Tape Inserts In Laminar Flow UsingAl2o3/Water And Cuo/Water Nanofluids, Super lattice Microst, page no [ 1 ] Juin Chen a, Hans Muller-Steinhagen b, Geoffrey G. Duffy a, (21) Heat Transfer Enhancement In Dimpled s, Applied Thermal Engineering,page no [ 11 ] Eiamsa-ard S. and Promvonge P. (26) Experimental investigation ofheat transfer and friction characteristics in a circular tube fitted with V-nozzleturbulators, International Communications in Heat and Mass Transfer, Vol.33,No.5, pp [ 12 ] Eiamsa-ard S. and Promvonge P. (27) Heat transfer characteristics in atube fitted with helical screw-tape with/without core-rod inserts, InternationalCommunications in Heat and Mass Transfer, Vol.34, No.2, pp IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 194