1-Automobile - IJAuERD - EXPERIMENTAL - Ramu S

International Journal of Automobile Engineering Research and Development (IJAuERD ) ISSN 2277-4785 Vol.2, Issue 2 Sep 2012 1-10 © TJPRC Pvt. Ltd.,

EXPERIMENTAL AND ANALYTICAL COMPARISON OF HEAT TRANSFER IN DOUBLE PIPE HEAT EXCHANGER M.KANNAN1, S.RAMU2, S.SANTHANAKRISHNAN3 & G.ARUNKUMAR4 1 2

Adhiparasakthi Engineering College, Melmaruvathur, Tamil Nadu, India

Sri Ramana Maharishi College of Engineering, Cheyyar, Tamil Nadu, India 3 4

Shri Sapthagiri Institute of Technology, Vellore, Tamil Nadu, India

Adhiparasakthi Engineering College, Melmaruvathur, Tamil Nadu, India

ABSTRACT The experimental comparison of different types of heat transfer enhancement techniques or methods in heat exchangers by extended surfaces, obstruction devices and swirl flow device. The system has followed different geometric profiles for attainable heat transferred in experimental result and compare with simulation result. The objective of these Experiments is to assist the general heat transfer processes and the methods and devices that can be implemented to enhance more heat transfer rate. The experimental setup and apparatus required to carry out the double pipe heat exchanger experiment. The apparatus includes tube-within-a-tube heat exchangers with threaded thermometer at each end, measuring flask, a water pump and electric geyser device. Three of the four heat exchangers are modified by one type of the above-mentioned heat transfer enhancement techniques. These methods used to found out the heat loss from the surface and related temperature of fluid motions also used to found the effectiveness, the effectiveness are having to compare the different flow rates for which one is maximum possible heat transfer in double pipe heat exchanger. Annular method is higher rate of heat transfer than other three methods.

KEY WORDS: Heat Transfer, Heat Exchanger, Extended Surface, Obstruction Device, Swirl Flow Device, Electric Geyser, Effectiveness.

INTRODUCTION GENERAL INFORMATION Heat transfer enhancement in heat exchangers is gaining industrial importance because it gives one the opportunity to reduce the heat transfer surface area required for a given application. The automotive and refrigeration industries routinely use enhanced surfaces in their heat exchangers. Also, the process industry is aggressively working to incorporate enhanced heat transfer surfaces in their heat exchangers. Heat transfer enhancement in heat exchangers has been the subject of many experimental and analytical investigations techniques. These techniques can be categorized as ‘active’ or ‘passive’. The active techniques require

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M.Kannan, S.Ramu, S.Santhanakrishnan & G.Arunkumar

external power, such as surface vibration, fluid vibration, injection, suction, and electric or acoustic fields.

Passive techniques employ special surface geometries for enhancement, such as extended surfaces, rough surfaces. We are often presented with the problem of how to transfer energy between two fluids at different temperatures and not allow them to mix. In order to allow this exchange to occur, we use a heat exchanger.

The design, analysis, and implementation of heat exchangers are an important part of heat transfer that should be familiar to them. Two primary methods exist when analyzing heat exchangers: Logarithmic Mean Temperature Difference (LMTD), and E-NTU. Many researchers (Artit Ridluan et al., Somsak Pethkool 2006; (1) Noothong et al., 2006;(2) P.Murugesan et al., 2009;(3)) have developed the investigation effects, there were twisted louvered strips, twisted tape (ratio y=5 and y=7) and trapezoidal cut used to done the experimental performance taken as Reynolds number, nusselt number, heat transfer co-efficient, friction factor and empirical co-rrelation. The louvered strip three different angle attack of the strip investigated by 17, 26 and 31 degrees and specified different length, materials, annulus section, and tape design, cut sections changed to enhance the heat transfer. The concept of double pipe heat exchanger fitted with helical rod was introduced by Warakosam Nerdnoi et al., (4) they reported that the enhancement in the heat transfer for helical rod was better than plain tube. For engineering research since increases the effectiveness of heat exchanger through suitable heat transfer augmentation, while the parameters measured to arranged the fins. It suggested more complicated to the heat transfer enhancement. But the method much more effective than existing and then theoretical treatment proposed and derived by the researcher N.Sahiti et al., 2005 ;(5).

Mlind V.Rane et al., (6) investigated the heat transfer rate due to temperature difference conducted along the pipe section heat losses occurred by serpentine layout and straight line THE. They concluded that increased 17% higher than the straight tube TTHE.

THEORETICAL ANALYSIS For fluid flows in a heat exchanger, the heat transfer rate can be expressed as: Q hot fluid = m. Cp. (To – Ti)

(1)

Q cold fluid = m. Cp. (To – Ti)

(2)

Q avg = Q hot fluid + Q cold fluid / 2

(3)

The conduction heat transfer from the test section can be written as: Q cond = - K. A. dT / dX

(4)

The convection heat transfer from the test section can be written as: Q conv = h. A fin. (Tw – T∞) Whereas, T∞ = (To + Ti) / 2

(5)

Experimental and Analytical Comparison of Heat Transfer in Double Pipe Heat Exchanger

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Effectiveness of heat exchanger: € = Q with fin/Q without fin

(6)

Overall heat transfer co-efficient: U = Q avg / A1. ∆Tm

(7)

A1 = π. d1. L

EXPERIMENTAL SETUP The basic heat exchanger was hooked up to both hot and cold water flows in a parallel-flow mode.

The cold water flow was an open circuit while the hot water flow was a closed circuit. This method having to construct as usually like tube within a tube. The water was heated to the desired temperature by a heating element. Adjusting the electrical energy input to the heating element controlled the water temperature. The temperatures at the inlet and exit were measured by the use of threaded thermometer. In the present work only passive enhancement techniques were considered. Two of these techniques were simply modifications to the annulus into the inner G.I tube one of the modifications to the annulus was the use of extended surfaces. This type of modification is routinely employed in many heat exchangers. Fins were placed on the outer surface of G.I tube. The Fins are arranged as inline method. The pipe carries on the weight of fin is longitudinal direction and the fins are placed on both sides. Each side carried 10 fins and the location of fin is splited to share the dimensions of the pipe and the overall pipe carried 20 fins along the pipe and the reaction of heat transferred from the fluid through the passes.

Figure 1.Experimental Setup

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M.Kannan, S.Ramu, S.Santhanakrishnan & G.Arunkumar

Figure 2. Profiles The heat were transferred by conduction and convection, the conduction happened by mean from fin and wall tube and the convection reaction done by fluid of hot and cold and extended surfaces. These two heat transfer were identically found by “Temperature mean� and other modification technique to the annulus was an obstruction device. This was accomplished by periodically restricting the flow with annulus rings or disks. The opening in the disk is located in the center and forces the liquid to pass through a narrow opening near the surface of the G.I tube. Because this opening is much smaller than the rest of the annulus, the liquid velocity is high through the opening. The rapid expansion on the far side of the opening triggers transition from laminar to turbulent flow, thus enhancing the rate of heat transfer. The spiraled rod, shown in crosssection was basically a 12.5 mm diameter Mild steel rod with pins inserted into it. The diameter of the pins was 5 mm and the angle of rotation of the pins was 90 degrees. They were arranged at 75 mm intervals along the axial length. The spiraled rod should enhance the heat exchanger for three reasons. First, the Pins act as triggers and promoters of turbulence. Secondly, secondary flow develops as the flow field is spiraled inside the annulus. And thirdly, the spiraled rod reduces the hydraulic diameter of the heat exchanger.

EXPERIMENTAL RESULTS &SIMULATION SIMULATION

Figure 3. Methods of extended surface

Experimental and Analytical Comparison of Heat Transfer in Double Pipe Heat Exchanger

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The mass flow rate of hot water was 23.88kg/s and the mass flow rate of cold water was 16.21kg/s.

The energy loss was occurred by hot fluid and energy gain by cold water and the experiment verified as average heat transfer (q) = 783.65Watts. Mass flow rate of hot water =70.01kg/s and mass flow rate of cold water = 23.59kg/s. The actual heat transfer gave higher heat losses from the modified heat exchanger. So, minimum mass flow rate have done as possible in second flow rate and more progression predicted on average heat transfer (q) = 534.24 Watts and Effectiveness (E) = 0.3574.The performance of heat transfer and effectiveness are enhanced to compared for these methods (basic tube-tube, rectangular fin, annular disk and spiral rod). Finally, annular method reached the higher rate of heat transfer than the other methods and the conducted experiment is completed successfully.

Figure 4.

Maximum temperature = 2111.58 k Minimum temperature = 351.07 k

Contour Temperature for Fin

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M.Kannan, S.Ramu, S.Santhanakrishnan & G.Arunkumar

Figure 5. Contour Temperature for Annular

Maximum temperature = 1376.94 k Minimum temperature = 463.22 k

Figure 6. Contour Temperature for Spiral Rod.

Maximum temperature = 558.42 k Minimum temperature = 537.66 k

Experimental and Analytical Comparison of Heat Transfer in Double Pipe Heat Exchanger

Figure 7. Average Heat Transfer Vs Mass Flow Rate of hot water

Figure 8. Effectiveness Vs Mass Flow Rate of hot water

Figure 9. Comparison of Mass Flow Rate and Effectiveness

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M.Kannan, S.Ramu, S.Santhanakrishnan & G.Arunkumar

Figure 10. Residual History for fin

Figure 11. Temperature Distribution for fin

Figure 12 Residual History for annular

Figure 13 Temperature Distribution for annular

Experimental and Analytical Comparison of Heat Transfer in Double Pipe Heat Exchanger

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Fig. 7 indicated the performance of heat transfer the mass flow rates were adjusted and the corresponding rate of the average heat transfer were increased and decreased. The mass flow rate decreased and the heat transferred has gained more than the expected heat transfer due to enhancement technique used.

Fig 8 indicated the mass flow rate and effectiveness. The mass flow rate increased, the heat transferred performed overall system and then the method with maximum possible heat transfer and effectiveness was identified in double pipe heat exchanger.

Fig. 10 to Fig. 15 shows the variations of temperature mean with respect to iteration and the comparison of simulation results of different methods. The experimental and analytical data were obtained and the results were identical. The experimental and analytical results compared, annular method reached higher heat transfer and effectiveness than other methods.

Figure 14. Residual History for spiral rod

Figure 15. Temperature Distribution for spiral rod

CONCLUSIONS This project has discussed and outlined an experimental setup for the evaluation of different heat exchanger enhancement techniques. Different mass flow rate readings were recorded. It was observed that the heat transfer loss and gain by hot and cold fluid. Finally, from the experimental and analytical results it is concluded that the annular method reached higher heat transfer than other methods.

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Artit Ridluan*, Somsak Pethkool1., Effect Of Louvered Strips On Heat Transfer In A Concentric Pipe Heat Exchanger, The 2nd Joint International Conference On “Sustainable Energy And Environment (See 2006)” A-028 (P) 21-23 November 2006, Bangkok, Thailand.

2.

Watcharin Noothong, Smith Eiamsa-Ard and Pongjet Promvonge1., Effect of Twisted-Tape Inserts on heat transfer in a tube the 2nd joint international conference on “sustainable energy and environment (see 2006)” a-030 (p) 21-23 november 2006, bangkok, thailand.

3.

P. Murugesan *, K. Mayilsamy, S. Suresh , P.S.S. Srinivasan., Heat Transfer and pressure drop characteristics of turbulent flow in a tube fitted with trapezoidal-cut twisted tape insert, International journal of academic research Vol. 1. No. 1. September 2009.

4.

N. Sahiti, F. Durst *, A. Dewan., Heat Transfer Enhancement By Pin Elements, International Journal Of Heat And Mass Transfer 48 (2005) 4738–4747

5.

Warakorm Nerdnoi, Putchaya Somravysin and Pongjet Promvonge., Heat Transfer and pressure drop characteristics in a double-pipe heat exchanger fitted with a turbulator.

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Milind V. Rane *, Madhukar S. Tandale., Water-To-Water Heat Transfer in Tube–Tube Heat Exchanger Experimental and Analytical Study.

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J.Y. jang., Numerical and experimental analytical of heat transfer and fluid flow in 3-D circular finned-tube heat exchanger, inter conf on CFD mineral and minning processing power generation, csiro 1997

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N.Nagarani, Experimental Heat Transfer Analysis on Annular Circular and Elliptical Fins, International Journal of Engineering Science and Technology, Vol. 2(7), 2010, 2839-2845.

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