Analysis Of Heat Transfer In Spiral Plate Heat Exchanger Using .

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IJSRD - International Journal for Scientific Research & Development Vol. 2, Issue 07, 2014 ISSN (online): 2321-0613 Analysis of Heat Transfer in Spiral Plate Heat Exchanger Using Experimental and CFD Prakash J. Sakariya1 Priyanka M. Jhavar2 Ravi D. Gujarati3 1 P.G. Student 2Professor 3Assistant Professor 1,2,3 Department of Mechanical Engineering 1,2,3 Shree Satya Saya Institute of Science and Technology - Sehore, India Abstract— Heat transfer is the key to several processes in industrial application. In a present days maximum efficient heat transfer equipment are in demand due to increasing energy cost. For achieving maximum heat transfer, the engineers are continuously upgrading their knowledge and skills by their past experience. Present work is a skip in the direction of demonstrating the use of the computational technique as a tool to substitute experimental techniques. For this purpose an experimental set up has been designed and developed. Analysis of heat transfer in spiral plate heat exchanger is performed and same Analysis of heat transfer in spiral plate heat exchanger can be done by commercially procurable computational fluid dynamic (CFD) using ANSYS CFX and validated based on this forecasting. Analysis has been carried out in parallel and counter flow with inward and outward direction for achieving maximum possible heat transfer. In this problem of heat transfer involved the condition where Reynolds number again and again varies as the fluid traverses inside the section of flow from inlet to exit, mass flow rate of working fluid is been modified with time. By more and more analysis and experimentation and systematic data degradation leads to the conclusion that the maximum heat transfer rates is obtained in case of the inward parallel flow configuration compared to all other counterparts, which observed to vary with small difference in each section. Furthermore, for the increase heat transfer rate in spiral plate heat exchanger is obtain by cascading system. Key words: Spiral Plate Heat Exchanger, Computational Fluid Dynamics (CFD), ANSYS CFX, Heat Transfer Rate, Reynolds Number, Nusselt Number. I. INTRODUCTION A. Heat exchanger A heat exchanger is a device used to transfer of heat from higher temperature to lower temperature. We can be done transfer of heat between two or more fluids, between two solid surfaces and a fluid, or between solid particulates and a fluid, at various temperatures and in thermal contact. B. Types of Heat Exchanger According to construction features According to heat transfer mechanisms According to flow arrangements According to transfer processes According to surface compactness According to number of fluids Classification According To Construction Features Generally, the most basic compact heat exchangers have a 50% less than volume of that of a comparable shell-and-tube heat exchanger, for a given work. Compact heat exchangers are classified into two types of spiral heat exchanger and plate type heat exchangers. Compact heat exchangers are characterized with its large amount of surface area in a given volume compared to other traditional heat exchangers, in particular the shell-and-tube type. The development and screening of compact heat exchangers has become an important requirement during the last few years. The interest stems from various reasons viz. less energy re-sources and decreasing raw material, the increasing pollution of environment and in-creasing operation costs and manufacturing costs of heat exchangers. The smooth and curved channels result in a very little fouling tendency with difficult fluids. Each fluid has only one channel and any localized fouling will result in degradation in the channel cross sectional area causing a increase velocity to roam the fouling layer. Spiral heat exchangers can be clean by itself. It is a main advantage of spiral heat exchanger so, the decreasing its operating cost due to self-cleaning effect, when the unit is horizontally mounted. The heat exchanger can be optimized for the process concerned by using various channel widths. Width of plate along the heat exchanger axis may be 2 m, as can the exchanger diameter, Heat transfer areas giving up to 600 m2 in a exchanger. Width of channel is generally in the range 5 to 30 millimeters. C. Construction Spiral plate heat exchangers consist of plates forming in a spiral by plate rolled together. The space between the two plates is kept by welded bolts to form the channels for the flow of the working fluids. In single phase applications, it is common for the hot (water) fluid enters to the heat exchanger through the central part of the exchanger and to exit at the extent. The cold (Water) fluid also enters the exchanger through the central part of the exchanger and to exit at the extent. Typically spiral heat exchangers are available in three configurations: Media in full counter-current flow. Combination Spiral Flow and Cross-Flow. One medium in spiral flow whilst the other is in cross flow. All rights reserved by www.ijsrd.com 446

Analysis of Heat Transfer in Spiral Plate Heat Exchanger Using Experimental and CFD (IJSRD/Vol. 2/Issue 07/2014/099) D. Operating Limits Generally, the maximum design temperature is depending on the gasket material and it is normally 400 oC temperature set by the limits of the gasket material. For high temperature operating limit up to 850oC but it can be done by Special designs. Maximum design pressure is usually 15 bars in heat exchanger by without gasket, we can obtain maximum pressures up to 30 bar but we need some special design. Thus, an open loop is effectively generated. The supply from the sump is divided equally by a T-section. The flow is then individually controlled by a ball valve. These two loops used in the system supply water to the system for the heat transfer process. II. LITERATURE REVIEW They produced a thermal modeling of the heat exchangers in both time dependent and steady state cases with 2D spiral geometry, allowing computation with various materials, forced convective heat transfer models in geometrical parameters options and turbulent flow. Findings of the results were displayed in steady state conditions with a view to enhance the performance of the exchanger. [2] in his experimental paper studies and they are obtained a shortcut method for the sizing of the spiral plate heat exchanger. [4] The spiral coil tube was fabricated by bending 8.00mm diameter straight copper tube into a spiral coil of five turns. Water are used for Hot fluid and cold fluid as a working fluid. The k-ɛ standard two equation turbulence model is used to simulate the turbulent flow and heat transfer characteristics. [5]The test section consisted of a plate thickness 0.001m, width 0.3150 m, and mean hydraulic diameter 0.01m. The mass flow rate of water (hot fluid) was kept varying from 0.5kgs-1 to 0.8kgs-1 and the mass flow rate of benzene was kept varying from 0.4kgs-1 to 0.7kgs-1. Experiments were conducted by varying the temperature, mass flow rate, and pressure of cold fluid keeping the mass flow rate of the hot fluid constant.[8] Their work represents approach for an alternative design for the sizing of spiral heat exchangers in single phase countercurrent applications. In this approach, pressure due to fluid friction can be directly related to the heat transfer coefficient through the exchanger geometry, thus resulting maximizes pressure drop in a sizing methodology and results in the design of the possible smallest dimensions.[10] It is found that the specification of a constant heat flux or constant temperature boundary condition for an actual heat exchanger does not yield proper modeling. Hence, the heat exchanger is analyzed considering conjugate heat transfer and temperature dependent properties of heat transfer media. An experimental setup is produced for the estimation of the heat transfer characteristics. The experimental results are compared with the CFD analysis using the CFD package FLUENT 6.2. Based on the experimental results a correlation is developed which can be used for the calculation of the inner heat transfer coefficient of the helical coil. Fig. 3.1: Schematic diagram of the experimental setup. A. Description of Experimental Setup Two mild steel plate of 420*420*3 mm where bought and make straighten Holes were drilled in on one plate for allowing a passage for the thermocouple to enter inside these plates for experimental measurements. The copper strip of 8000*30*0.5 mm was fitted into the plate in which the holes for thermocouples were not drilled. The M.S. plate with drilled hole was fit over the other plate one after the other. The plate was set in the spaces between the copper strip and equal spaces were created between profile curves using hammer and a pair of tongs. After the plate was adjusted over the copper strip, it was carefully shouldered with the copper strip. The distances between the two pates were decided and the distances between them were accordingly kept with the help of screw, nut and bolts. The experimental setup thus prepared in the absence of thermocouple looked as shown in figure. Four copper tubes were brought for the supply of fluids through the spiral plate heat exchanger and were shouldered in the setup. The thermocouple were inserted in to drilled hole and shouldered. The entire experimental setup was thus prepared. Prevent leakage of water at any point in the set up Mseal was glued on shouldered portion. III. EXPERIMENTAL SET UP AND PROCEDURE The experimental setup was designed essentially to investigate the forced convection heat transfer in a spiral plate heat exchanger. The setup was fabricated in Sehore, and erected in the Mechanical Engineering Department at Faculty of Technology & Engineering, RGPV Bhopal. The schematic diagram of the heat exchanger test loop used for the study is as shown. Water, the working fluid, is drawn from a large sump and discharged in to the drainage. Fig. 3.2: Experiment set up B. Experimental Procedure Establish the flow of working fluid and cold fluid from sump to the main valve. Setup the temperature in the container holding the working fluid i.e. the hot water to a predetermined All rights reserved by www.ijsrd.com 447

Analysis of Heat Transfer in Spiral Plate Heat Exchanger Using Experimental and CFD (IJSRD/Vol. 2/Issue 07/2014/099) Description ThermocoupleK-Type, One end Heating Element Digital Voltmeter Valve Test Rig Quantity 42 Grounded Induction type 750W 1 0.1mV-100 mV 1 10 mm inner 2 dia. Mild Steel 2 Platte 420*420*3 Copper 1 3 Strip mm 8000*30* Coppe 3 4 0.5mm r Pipe D0 10 Table. 3.1: List of instrument mm, Diused 8 in experiment set up C. Computational analysis mm The exchanger geometry was modeled using Pro-E (Fig.2) and mesh was generated in ICEM CFD (shown in Fig.3).Boundary condition and solution done in CFX. Grid sensitivity study is carried out in order to access an optimum balance between computer resources and accuracy of results on that basis 28 lac element was selected for analysis. RNG k-epsilon model was used in simulation. Simulation was run for steady state conditions and average physical properties were used. Fig. 3.3: Geometry of Single Stage Spiral Plate Heat Exchanger Fig. 3.4: Mesh of single stage spiral plate heat exchanger IV. RESULTS A. Comparison Between the two parallel flow conditions for Experimental and Computational HIGH TO LOW Re Ln (Nu/Pr 0.3) degree using a thermostat heater. Allow the flow of cold water from the sump directly to the test section. Control the flow of working fluid and cold fluid to the test section using a ball valve. Set the direction of flow to the test section i.e. parallel-inward/outward or counter- inward/outward. Ground the thermocouple with reference thermocouple which is kept in SAE 30 oil surrounded by an ice bath. Close the circuit using Digital Volt Meter (DVM). The circuit is then completed by joining one end of thermocouple to the reference thermocouple and the other end to the DVM. Readings are displayed by the DVM in mV which are converted to using standard available tables and statistical tool. Repeat the same process for every thermocouple in sequence. Stop the flow once all readings are taken and setup the temperature of working fluid to another degree and repeat the procedure again for a given type of flow. Repeat the procedure for different inlet and outlet temperatures for various flow conditions. Ln Re LOW TO HIGH Re Fig. 4.1: Thermal performance of parallel flow inward and outward Configuration for experiment Ln (Nu/Pr 0.3) comp. y Exp 0.5131x PFO 6.549 2 R Comp 0.6727 PFO EXP. y 0.5342x 6.7499 Ln Re R2 0.7317 Fig. 4.2: thermal performance of parallel flow outward configuration for computational Figure 4.1 and Figure 4.2 shows the thermal performance of inward as well as outward flow on the same scale. The data fitting trend line shows confidence level of 95.78% and 66.74% for inward and outward flow respectively for experimentally and 94.09% and 67.27% for inward and outward flow respectively for computationally. Comparing both experimental and computational confidence level, both case it deviate within 1.5% range. The higher confidence level justified the logarithmic trend fitting assumption. The figure shows the parallel flow inward and outward flow configurations. From the figure 4.2 and 4.3, it is observed that the variation in the Re for the inward flow configuration is from high to low, whereas the same for outward flow configuration will be from lower to higher, as shown by arrow. Take the case for the outward flow configuration, the flow will be accelerated as it traverses from inlet to exit of the cross section. As a result, there will be a corresponding increase in the Reynolds Number. However, it is important to note that as Re increases, the thermal performance or Nusselt Number of flow decreases. This leads one to believe that the acceleration in the flow due to the passage swirl is not helpful in increasing Nusselt Number, it rather decreases Nusselt Number. Further it is observed that spacing of the observation All rights reserved by www.ijsrd.com 448

Analysis of Heat Transfer in Spiral Plate Heat Exchanger Using Experimental and CFD (IJSRD/Vol. 2/Issue 07/2014/099) points also tend to become dense as flow move towards the outer periphery. This is because of the fact that each incremental contribution in thermal performance in the spiral (or more precisely deterioration) is less and less significant for steady state conditions and average physical properties were used. Ln (Nu/Pr 0.3) y 0.8276x 8.765 R2 Ln Re 0.9632 Fig. 4.3: Comparison between two counter flow configurations for experiment comp. y 0.7682x 8.5245 R2 0.9969 Exp EXP. Comp y 0.8296x 9.0324 Ln Re R2 0.9671 between two counter outward Fig. 4.4: comparisons configurations for experimental and computational From figure 4.3 & 4.4. it is observed that the variation in the Re for the inward flow configuration is from the high to low, whereas the same for outward flow configuration will be from lower to higher, as shown by arrow. Consider the case of the outward flow condition; the flow will be accelerated as it traversed from inlet to exit of the cross section. So, there will be corresponding increase in the Reynolds Number. However, with increase in Reynolds Number, the thermal performance or Nusselt Number decreases. This indicates that the acceleration in the flow which is due to the swirl in the passage is not helpful in increasing the Nusselt Number. The swirl in the flow passage rather decreases Nusselt Number. It is also observed that the spacing of the observation points also tend to become dense with the increase in Reynolds Number. This is due to that fact that each incremental contribution in thermal performance in the spiral (more precisely deterioration) is less and less significant. C. Computational analysis The exchanger geometry was modeled using Pro-E (Fig.2) and mesh was generated in ICEM CFD (shown in Fig.3).Boundary condition and solution done in CFX. Grid sensitivity study is carried out in order to access an optimum balance between computer resources and accuracy of results on that basis 28 lac element was selected for analysis. RNG k-epsilon model was used in simulation. Simulation was run Fig. 3.3: Geometry of single stage spiral plate heat exchanger Fig. 3.4: Mesh of single stage spiral plate heat exchanger V. RESULTS A. Comparison Between th e two parallel flow conditions for Experimental and Computational HIGH TO LOW Re Ln (Nu/Pr 0.3) y -0.603x 7.6172 R2 0.9322 Ln Re LOW TO HIGH Re Fig. 4.1: Thermal performance of parallel flow inward and outward Configuration for experiment Ln (Nu/Pr 0.3) Ln (Nu/Pr 0.3) B. Comparison between the two counter flow condition for Experimental and computational comp. y Exp 0.5131x PFO 6.549 R2 Comp 0.6727 PFO EXP. y 0.5342x 6.7499 Ln Re R2 0.7317 Fig. 4.2: thermal performance of parallel flow outward configuration for computational Figure 4.1 and Figure 4.2 shows the thermal performance of inward as well as outward flow on the same scale. The data fitting trend line shows confidence level of 95.78% and 66.74% for inward and outward flow respectively for experimentally and 94.09% and 67.27% for inward and outward flow respectively for computationally. Comparing both experimental and computational confidence level, both case it deviate within 1.5% range. The higher confidence level justified the logarithmic trend fitting assumption. The figure shows the parallel flow inward and outward flow configurations. From the figure 4.2 and 4.3, it is observed that the variation All rights reserved by www.ijsrd.com 449

Analysis of Heat Transfer in Spiral Plate Heat Exchanger Using Experimental and CFD (IJSRD/Vol. 2/Issue 07/2014/099) in the Re for the inward flow configuration is from high to low, whereas the same for outward flow configuration will be from lower to higher, as shown by arrow. Take the case for the outward flow configuration, the flow will be accelerated as it traverses from inlet to exit of the cross section. As a result, there will be a corresponding increase in the Reynolds Number. However, it is important to note that as Re increases, the thermal performance or Nusselt Number of flow decreases. This leads one to believe that the acceleration in the flow due to the passage swirl is not helpful in increasing Nusselt Number, it rather decreases Nusselt Number. Further it is observed that spacing of the observation points also tend to become dense as flow move towards the outer periphery. This is because of the fact that each incremental contribution in thermal performance in the spiral (or more precisely deterioration) is less and less significant Ln (Nu/Pr 0.3) B. Comparison between the two counter flow condition for Experimental and computational y -0.603x 7.6172 R2 0.9322 Ln (Nu/Pr 0.3) y 0.8276x 8.765 R2 Ln Re 0.9632 Fig. 4.3: Comparison between two counter flow configurations for experiment comp. y 0.7682x 8.5245 R2 0.9969 increase in Reynolds Number. This is due to that fact that each incremental contribution in thermal performance in the spiral (more precisely deterioration) is less and less significant. VI. CONCLUSION From the results obtained from the experimentation, it is evident that highest heat transfer rate is obtained in case of parallel inward flow conditions. In case of other variations of fluid flow through the heat exchanger, the heat transfer rates obtained are nearly similar. It can also be observed from the graph that for a particular range of Reynolds No., the heat transfer rates almost become stagnant. This indicates an area of the heat exchanger where equal amount of heat transfer takes place between the two fluids. Furthermore heat transfer rate in spiral plate heat exchanger is enhanced by cascading of the heat exchangers. This can be carried out using the simulation techniques. By doing so, the heat transfer rate increase by 26.25 % of single stage heat transfer rate as we are going on increasing stages of spiral plate heat exchanger, heat transfer rate is increases. A. Sample Calculation Time required to fill 2 Liters of hot water 120 sec Time required to fill 2 Liters of cold water 120 sec Mass flow rate for hot side, m1 ρ1A1V1 2/120 0.01667 kg/s Exp EXP. Comp y 0.8296x 9.0324 Ln Re R2 0.9671 between two counter outward Fig. 4.4: comparisons configurations for experimental and computational From figure 4.3 & 4.4. it is observed that the variation in the Re for the inward flow configuration is from the high to low, whereas the same for outward flow configuration will be from lower to higher, as shown by arrow. Consider the case of the outward flow condition; the flow will be accelerated as it traversed from inlet to exit of the cross section. So, there will be corresponding increase in the Reynolds Number. However, with increase in Reynolds Number, the thermal performance or Nusselt Number decreases. This indicates that the acceleration in the flow which is due to the swirl in the passage is not helpful in increasing the Nusselt Number. The swirl in the flow passage rather decreases Nusselt Number. It is also observed that the spacing of the observation points also tend to become dense with the Mass flow rate for hot side, m1 ρ2A2V2 2/120 0.01667 kg/s Base radius, Rb 0.085m, Radius at Corresponding points is R0 Rb 0.085m, R1 2Rb 0.017m, R2 3Rb 0.255m Cross Section of Hot and Cold Side: Width, b 2*Rb 0.020m, Height, d 2*Rb 0.020m Velocity of flow V0 m/ρ b d 0.01667/1000*0.020*0.020 0.041675 m/s Angular velocity, ω V/R 0.041675/0.085 4.9029 rad/s The characteristic hydraulic diameter for this test section can be determined using the following equation Deq 4*0.020*0.020/2*(0.020 0.020) 0.020m The wetted perimeter is given by 2 * (b d) 2 * (0.020 0.020) 0.080m The Reynolds No. is given by, Rex 2* 0.01667 * 0.085/0.000819 * 0.020 * 0.020 1896 The mean temperature between two thermocouples on hot side is, Th (44.23 43.98)/2 44.54 0C The mean radius between two thermocouples on hot side is, Rh (0.085 0.020)/2 0.01575m The mean temperature between thermocouples on cold side is, Tc two (32.93 33.91)/2 24.980C All rights reserved by www.ijsrd.com 450

Analysis of Heat Transfer in Spiral Plate Heat Exchanger Using Experimental and CFD (IJSRD/Vol. 2/Issue 07/2014/099) Coefficients for Spiral Plate Heat Exchanger”, Modern Applied Science, volume 2 (September 2008), pp.14-20. [8] M. Picón Núñez, L. Canizalez Dávalos and A. Morales Fuentes, “Alternative design approach for spiral plate heat exchangers ”, Institute for Scientific Research, University of Guanajuato Lascurain de Retana No. 5, 36000 Guanajuato, Gto, México. [9] S. Ramachandran, P. Kalaichelvi and S. Sundaram, “Heat Transfer Studies In a Spiral Plate Heat Exchanger for Water – Palm Oil Two Phase System ”, Brazilian Journal of Chemical Engineering, Vol. 25, No. 03, pp. 483 - 490, July September, 2008. [10] J.S. Jayakumara,b, S.M. Mahajania, and J.C. Mandala, “Experimental and CFD estimation of heat transfer in helically coiled heat exchangers ”, Indian Institute of Technology, Mumbai, India, Bhabha Atomic Research Centre, Mumbai, India, pp. 222232. [11] Zeid Y. Munir, “Numerical Investigation of the Thermal Effectiveness of Spiral-Plate Heat Exchangers”, the thesis of Faculty of the Graduate School of the University of Kansas in 2006. The mean radius between two thermocouples on cold side is, Rc (0.085 0.020)/2 0.01575m The heat transfer area for hot side is, Ah R1 * π* A1 0.01575* π * 0.020 0.0008 Heat transfer area for cold side is, Ac R2 * π* A2 0.01575* π * 0.020 0.00078 m2 Heat lost, Q1 m1.cp.ΔT 0.025 * 4.179 * 2.058 * 1000 215 J/s Heat gain, Q2 m2.cp.ΔT 0.025 * 4.179 * 2.579 * 1000 269 J/s Over all wall temperature, Tw (44.54 24.98) / 2 37.54 0C Over all mean radius, (0.01575 0.01575) / 2 0.01575 m Heat transfer coefficient for hot side, Hh 215 / (0.0008 * 7) 44890 W/m2K Heat transfer coefficient for cold side, Hc 269 / (0.0008 * 7) 32512 W/m2K Over all heat transfer coefficient, H (44890*32512)/(44890 32512) 18855 W/m2K Nusselt number for hot fluid side, Nuh (44890 * 0.020) / 0.0626857 14322.24 Nusselt number for hot fluid side, Nuc (32512 * 0.020) / 0.0626857 953.85 Over all Nusselt number, N H* Deq /K (18855 *0.020) / 0.0626857 601 R REFERENCES Journal Papers [1] J. F. Devois et al., “Numerical Modeling of the Spiral Plate heat Exchanger”, journal of thermal analysis, volume 44 (1995), pp. 305-312. [2] M. Pico n-Nu n ez et al., “Shortcut Design Approach for Spiral Heat Exchangers”, Trans IChemE, Part C, Food and Bioproducts Processing, 2007, 85(C4): 322–327. [3] Paisarn Naphon, “Study on the heat transfer and flow characteristics in a spiral-coil tube”, International Communications in Heat and Mass Transfer 38 (2011), pp. 69–74. [4] R.Rajavel1, K. Saravanan, “An Experimental Study of Spiral Plate Heat Exchanger for Electrolytes”, Journal of the University of Chemical Technology and Metallurgy, 43, 2, 2008, 255-260. [5] Dr. Kaliannan Saravanan et al., “Analysis of Heat Transfer Enhancement in Spiral Plate Heat Exchanger”, Modern Applied Science, volume 2 (July 2008), pp. 68-75. [6] P. Kalaichelvi et al., “Heat Transfer Studies for Two Phase Flow In a Spiral Plate Heat Exchanger”, Journal of the University of Chemical Technology and Metallurgy, 41, 4, 2006, 439-444. [7] Rangasamy Rajavel, Kaliannan Saravanan, “An Experimental Investigation of Heat Transfer All rights reserved by www.ijsrd.com 451

A. Heat exchanger A heat exchanger is a device used to transfer of heat from higher temperature to lower temperature. We can be done transfer of heat between two or more fluids, between two solid surfaces and a fluid, or between solid particulates and a fluid, at various temperatures and in thermal contact. B. Types of Heat Exchanger

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