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Numerical simulation of a tube in tube helical coiled heat

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Carnegie Mellon University
Carnegie Mellon University

Heat exchangers are used widely in industrial application such as chemical, food processing, power production, refrigeration and air-conditioning industries. Helical coiled heat exchangers are used in order to obtain a large heat transfer per unit volume and to enhance the heat transfer rate on the inside surface. In the present study, CFD simulations are carried out for a counter flow tube in tube helical heat exchanger where hot water flows through the inner tube and cold water flows through the outer tube. From the simulation results heat transfer coefficient, pressure drop and nusselt number are calculated. The heat transfer characteristics of the same are compared with that of a counter flow tube in tube straight tube heat exchanger of same length under same temperature and flow conditions. CFD simulation results showed that the helical tube in tube heat exchanger is more effective than the straight tube in tube heat exchanger.

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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 9, Number 18 (2014) pp. 5209-5220 © Research India Publications http://www.ripublication.com Numerical Simulation of a Tube in Tube Helical Coiled Heat Exchanger using CFD Soby P. Sunny1 , Siddharth D. Mhaske2 , Yash B. Parikh3 1 (PG Student, Mechanical Engineering Department, Symbiosis Institute of Technology, Pune) 2 (PG Student, Mechanical Engineering Department,, Symbiosis Institute of Technology, Pune) 3 (Assistant Professor, Mechanical Engineering Department, Symbiosis Institute of Technology, Pune) 1 sobzsunny@gmail.com 2 mhaskesiddharth@gmail.com 3 yash.parikh@sitpune.edu.in Abstract Heat exchangers are used widely in industrial application such as chemical, food processing, power production, refrigeration and air-conditioning industries. Helical coiled heat exchangers are used in order to obtain a large heat transfer per unit volume and to enhance the heat transfer rate on the inside surface. In the present study, CFD simulations are carried out for a counter flow tube in tube helical heat exchanger where hot water flows through the inner tube and cold water flows through the outer tube. From the simulation results heat transfer coefficient, pressure drop and nusselt number are calculated. The heat transfer characteristics of the same are compared with that of a counter flow tube in tube straight tube heat exchanger of same length under same temperature and flow conditions. CFD simulation results showed that the helical tube in tube heat exchanger is more effective than the straight tube in tube heat exchanger. Keywords: Heat exchanger, helical coil, CFD, simulation Introduction Flow through a helical coiled tube has observed extensive applications including power plants, chemical, refrigeration, air conditioning and food processing industries. Fluid flow in a coiled tube in tube will experience a centrifugal force, which results in a secondary flow. The secondary flow enhances the heat transfer rates as it reduces
5210 Soby P. Sunny et al the temperature gradient across the cross-section of the tube. Thus there is one more convective heat transfer mechanism in helical coils, perpendicular to the main flow, which does not exist in straight tube heat exchangers. An experimental study on helical coiled heat exchanger were done and results showed that heat transfer coefficient was affected by the geometry of the heat exchanger. It also showed that heat transfer coefficient was more for helical coiled tubes compared to the straight tube [1]. A CFD model was developed to be validated with the experimental values, the results showed the outlet temperatures and nusselt number were very close to the experimental values [2]. Numerical study of tube in tube helical heat exchanger for both parallel and counter flow was done. The result indicated that in the design of double pipe helical heat exchanger there must be more attention given to the annulus side as the thermal resistance is dominating in the annulus part [3]. Experimental and CFD study of helically coiled heat exchangers were done, results showed that CFD simulation results match reasonably well with the experiment [4]. A CFD analysis of helical tube in tube heat exchanger was done to determine the nusselt number and heat transfer coefficient. The result showed along the outer side of the pipes the velocity and pressure values were higher in comparison to the inner values [7]. A study of pressure drop characteristics of nano fluid flow inside a vertical helical coiled tube was conducted, the results indicated that using helical tubes instead of straight tube increases the pressure drop exponentially [5]. A comparative analysis was carried out for different correlations by different researchers for helical coil heat exchanger. Results showed that the ratio of the tube diameter to coil diameter should be large enough for large intensities of secondary flow inside the tube [6]. Objective The objective of the study is to determine the heat transfer characteristics of helical tube in tube heat exchanger. The helical coil tube in tube heat exchanger was initially modeled and then simulated using computational fluid domain with fixed wall temperature boundary conditions. The parameters like heat transfer rate, heat transfer coefficient, and Nusselt number were calculated. The result obtained from simulation is then validated with the literature study done on helical tube in tube with same dimensions and same flow rates. The straight tube in tube heat exchanger was also modeled of equal length and operating conditions, so as to compare with the heat transfer characteristics of helical tube in tube heat exchanger. Numerical modelling and simulation Geometry and parameters of tube in tube helical coil The major geometric dimensions include the inner diameter of the tube (d1), outer diameter of the tube (d2), curvature diameter (D) and the coil pitch (p). Table 1 below shows dimensional and used in the present study.
Numerical Simulation of a Tube 5211 Table 1: Dimensional and operating parameters of the heat exchanger S. No. Dimensional Parameters Values 1 Inner tube diameter 15.8mm 2 Outer tube diameter 22.5mm 3 Curvature radius 76.2mm 4 Inlet temperature 345 5 Outlet temperature 280 6 Working fluid Water Figure 1. Schematic diagram of helical and straight tube in tube helical heat exchanger
5212 Soby P. Sunny et al Calculation of heat transfer coefficient and nusselt number The heat transfer Q, can be obtained from the simulated result of the heat exchanger. Then heat transfer coefficient, h can be calculated from the equation, TA Q h   . (1) Q = heat transfer (W), h = heat transfer coefficient (W/m2 K), A = area of heat transfer (m2 ), ∆T = difference between temperature average fluid temperature and average helical coil temperature (K) Nusselt number, Nu can be calculated by using the relations, K hD Nu h)(  (2) Nu = Nusselt Number, h = heat transfer coefficient, Dh = hydraulic diameter, k = thermal conductivity The heat transfer coefficient, nusselt number are calculated for the tube in tube helical heat exchanger and further compared with straight tube in tube heat exchanger. 3.2. Numerical Simulation The CFD software ANSYS Fluent 14.0 was used to solve the governing equations of mass, momentum and heat transfer. The tube in tube helical heat exchanger was modeled in ANSYS fluent geometry module, then the meshing of the model was done in ANSYS fluent meshing module. In order to get good results fine mesh was employed, hexahedral and tetrahedral mesh was used for the model. Also at high temperature region near boundaries we employed structured hexahedral mesh. The k- Ɛ standard turbulence model was used as the viscous model suggested by Wang and Chen. In the simulation of the turbulent flow, simple scheme algorithm for pressure velocity coupling was used. The assumptions used for the simulation of the helical heat exchanger are: 1. The flow is steady and incompressible. 2. Radiation and natural convection effects are ignored. 3. Constant wall temperature at the boundary. The inputs are given at the two inlets of the inner tube and outer tube. The conservation equations were solved for the control volume to yield the velocity and temperature fields for the fluid flow in the model. The model was converged when all the residuals fell below 10-6 in the computational domain.
Numerical Simulation of a Tube 5213 Results and discussions The CFD simulation was done for the three different mass flow rates of water respectively for both straight and helical tube ranging from 0.2kg/s to 0.7kg/s. Reynolds number corresponding to these mass flow rates were varying from 4000 to 9000. The parameters that are adopted for comparison are temperature of water at the outlet, heat transfer rate, nusselt number, pressure drop and heat transfer coefficient. The flow of fluid in helical coil is shown in the figure 2, the fluid particles moves towards the outer wall then returns to the inner portion of tube by flowing back along the wall. The figure 3 shows the close view of the velocity vectors, the fluid in the curve of the tube moves towards the outer wall and then returns to the inner portion of tube by flowing back along the wall. Figure 4 shows the temperature contour for the helical tube in tube. It can be seen that temperature drop for helical tube in tube is higher than the straight tube, which is due to the curvature effect of the helical shape of the coil. Fluid flow in the outer layer of the tube in tube moves faster than the fluid flow in the inner layer due this a secondary flow is set which enhances the heat transfer. Figure 5 shows the temperature contour for the straight tube in tube, it shows the temperature drop in the inner tube from inlet to outlet. Figure 6 and 7 shows the variation of heat transfer coefficient for different mass flow rates for the inner and outer tube of helical and straight tube in tube heat exchanger. From the graph it is clear that as mass flow rate increases heat transfer coefficient also increases as expected since heat transfer rate is proportional to the mass flow rate. The heat transfer coefficient for helical tube in tube shows a remarkable increase of heat transfer coefficient by 10.5% when compared to the straight tube in tube heat exchanger. Figure 8 and 9 shows the variation of inner tube and outer tube nusselt number for helical and straight tube in tube heat exchanger. Nusselt numbers corresponding to the helical is higher than the straight tube in tube for all mass flow rates. This is due to the secondary flow in the helical tube in tube which aids the heat transfer. The nusselt number increased by 10.9% for helical tube in tube when compared to straight tube in tube for a particular mass flow rate. In the helical coils at higher mass flow rates the Reynolds number increases and the fluid turbulence also increases. Thereby due to higher turbulence the intensity of secondary flow increases and hence nusselt number. Figure 10 shows the variation of pressure drop over the entire length of helical tube in tube heat exchanger. From the figure 11 it is clear that the pressure drop in helical tube in tube is higher than that in straight tube in tube, this is due to the centrifugal force and secondary flow in helical tube in tube. Secondary flow dissipates kinetic energy which increases the resistance to flow. The present study was validated from the literature work done by Soumya Ranjan, 2013. Figure 12 shows the Total pressure at different points along the pipe length for the outer wall were checked and an accuracy of 94.56% was achieved.
5214 Soby P. Sunny et al Figure 2. Velocity vectors colored by velocity magnitude (m/s) Figure 3. Close view of velocity vectors of helical tube in tube
Numerical Simulation of a Tube 5215 Figure 4. Contours of static temperature in K of helical tube in tube Figure 5. Contours of static temperature for inner tube of straight tube in tube
5216 Soby P. Sunny et al Figure 6: Variation of heat transfer coefficient with mass flow rate for inner tube of helical and straight tube in tube Figure 7: Variation of heat transfer coefficient with mass flow rate for outer tube of helical and straight tube in tube
Numerical Simulation of a Tube 5217 Figure 8: Variation of Nusselt Number with mass flow rate for inner tube of helical and straight tube in tube Figure 9: Variation of Nusselt number with mass flow rate for outer tube of helical and straight tube in tube
5218 Soby P. Sunny et al Figure 10: Pressure drop along the length of the helical tube in tube Figure 11: Total Pressure Plot for outer wall of helical tube in tube and straight tube in tube
Numerical Simulation of a Tube 5219 Figure 12: Total Pressure Plot for outer wall of helical tube in tube Conclusion In this present work CFD simulation for helical tube in tube heat exchanger was carried out and the results of heat transfer parameters have been compared with the straight tube in tube under same geometrical and operating conditions. The CFD results are validated with the literature work, the results achieved were well within the error limits. Simulation results indicated that heat transfer rate, nusselt number and heat transfer coefficient are higher in case of helical tube in tube when compared with the straight tube in tube. For different mass flow rates, the helical tube in tube heat exchanger provides an increase in heat transfer coefficient by 10.5%. The pressure drop for helical coil tube in tube is found to be more when compared with the straight tube in tube for identical conditions and varies exponentially indicating the necessity of higher pumping power for helical tube in tube heat exchanger. Table 2: Nomenclature Nomenclature Re, Reynolds number Dh, Hydraulic Diameter (m) Q, Heat transfer rate (W) Nu, Nusselt Number A, Area of heat transfer (m2 ) k, Thermal conductivity (W/mK) ∆T, Temperature difference (K) ∆P, Pressure drop (Pa) 6. References [1] Prabhanjan D.G., Raghavan G.S.V., and Rennie T.J., “Comparison of heat transfer rates between a straight tube heat exchanger and a helically coiled heat exchanger”, Heat and mass transfer, Vol. 29, No. 2, (2002), pp.185-191.
5220 Soby P. Sunny et al [2] Prabhanjan D.G., Raghavan G.S.V., and Rennie T.J., “Natural convection heat transfer from helical coiled tubes”, International Journal of Science, Vol. 43, No. 4, (2004), pp. 359-365. [3] Timothy J.R., Vijaya G.S., “Numerical studies of a double-pipe helical heat exchanger”, Applied Thermal Engineering, Vol. 26, (2006), pp. 1266-1273. [4] J.S. Jayakumar, S.M. Mahajani, J.C. Mandal, “Experimental and CFD estimation of heat transfer in helically coiled heat exchangers”, Chemical engineering research and design, Vol. 86, (2008), pp. 221-232. [5] Pramod S. P., Mandar M. L., Rajkumar G., “Parametric analysis of helical coil heat exchanger”, International Journal of Engineering Research & Technology, Vol.1, Issue 8, (2012), pp. 1-5. [6] M. P. Fakoor-Pakdaman, M.A. Akhavan-Behabadi, P. Razi, “An empirical study on the pressure drop characteristics of Nano fluid flow inside helically coiled tubes” International Journal of Thermal Sciences, Vol. 65, (2013), pp. 206-213. [7] Soumya R.M., “CFD analysis of heat transfer in a helical coil heat exchanger using fluent”, Maser Thesis, NIT Rourkela, India, (2013), pp. 1-33.

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Numerical simulation of a tube in tube helical coiled heat

  • 1. International Journal of Applied Engineering Research ISSN 0973-4562 Volume 9, Number 18 (2014) pp. 5209-5220 © Research India Publications http://www.ripublication.com Numerical Simulation of a Tube in Tube Helical Coiled Heat Exchanger using CFD Soby P. Sunny1 , Siddharth D. Mhaske2 , Yash B. Parikh3 1 (PG Student, Mechanical Engineering Department, Symbiosis Institute of Technology, Pune) 2 (PG Student, Mechanical Engineering Department,, Symbiosis Institute of Technology, Pune) 3 (Assistant Professor, Mechanical Engineering Department, Symbiosis Institute of Technology, Pune) 1 sobzsunny@gmail.com 2 mhaskesiddharth@gmail.com 3 yash.parikh@sitpune.edu.in Abstract Heat exchangers are used widely in industrial application such as chemical, food processing, power production, refrigeration and air-conditioning industries. Helical coiled heat exchangers are used in order to obtain a large heat transfer per unit volume and to enhance the heat transfer rate on the inside surface. In the present study, CFD simulations are carried out for a counter flow tube in tube helical heat exchanger where hot water flows through the inner tube and cold water flows through the outer tube. From the simulation results heat transfer coefficient, pressure drop and nusselt number are calculated. The heat transfer characteristics of the same are compared with that of a counter flow tube in tube straight tube heat exchanger of same length under same temperature and flow conditions. CFD simulation results showed that the helical tube in tube heat exchanger is more effective than the straight tube in tube heat exchanger. Keywords: Heat exchanger, helical coil, CFD, simulation Introduction Flow through a helical coiled tube has observed extensive applications including power plants, chemical, refrigeration, air conditioning and food processing industries. Fluid flow in a coiled tube in tube will experience a centrifugal force, which results in a secondary flow. The secondary flow enhances the heat transfer rates as it reduces
  • 2. 5210 Soby P. Sunny et al the temperature gradient across the cross-section of the tube. Thus there is one more convective heat transfer mechanism in helical coils, perpendicular to the main flow, which does not exist in straight tube heat exchangers. An experimental study on helical coiled heat exchanger were done and results showed that heat transfer coefficient was affected by the geometry of the heat exchanger. It also showed that heat transfer coefficient was more for helical coiled tubes compared to the straight tube [1]. A CFD model was developed to be validated with the experimental values, the results showed the outlet temperatures and nusselt number were very close to the experimental values [2]. Numerical study of tube in tube helical heat exchanger for both parallel and counter flow was done. The result indicated that in the design of double pipe helical heat exchanger there must be more attention given to the annulus side as the thermal resistance is dominating in the annulus part [3]. Experimental and CFD study of helically coiled heat exchangers were done, results showed that CFD simulation results match reasonably well with the experiment [4]. A CFD analysis of helical tube in tube heat exchanger was done to determine the nusselt number and heat transfer coefficient. The result showed along the outer side of the pipes the velocity and pressure values were higher in comparison to the inner values [7]. A study of pressure drop characteristics of nano fluid flow inside a vertical helical coiled tube was conducted, the results indicated that using helical tubes instead of straight tube increases the pressure drop exponentially [5]. A comparative analysis was carried out for different correlations by different researchers for helical coil heat exchanger. Results showed that the ratio of the tube diameter to coil diameter should be large enough for large intensities of secondary flow inside the tube [6]. Objective The objective of the study is to determine the heat transfer characteristics of helical tube in tube heat exchanger. The helical coil tube in tube heat exchanger was initially modeled and then simulated using computational fluid domain with fixed wall temperature boundary conditions. The parameters like heat transfer rate, heat transfer coefficient, and Nusselt number were calculated. The result obtained from simulation is then validated with the literature study done on helical tube in tube with same dimensions and same flow rates. The straight tube in tube heat exchanger was also modeled of equal length and operating conditions, so as to compare with the heat transfer characteristics of helical tube in tube heat exchanger. Numerical modelling and simulation Geometry and parameters of tube in tube helical coil The major geometric dimensions include the inner diameter of the tube (d1), outer diameter of the tube (d2), curvature diameter (D) and the coil pitch (p). Table 1 below shows dimensional and used in the present study.
  • 3. Numerical Simulation of a Tube 5211 Table 1: Dimensional and operating parameters of the heat exchanger S. No. Dimensional Parameters Values 1 Inner tube diameter 15.8mm 2 Outer tube diameter 22.5mm 3 Curvature radius 76.2mm 4 Inlet temperature 345 5 Outlet temperature 280 6 Working fluid Water Figure 1. Schematic diagram of helical and straight tube in tube helical heat exchanger
  • 4. 5212 Soby P. Sunny et al Calculation of heat transfer coefficient and nusselt number The heat transfer Q, can be obtained from the simulated result of the heat exchanger. Then heat transfer coefficient, h can be calculated from the equation, TA Q h   . (1) Q = heat transfer (W), h = heat transfer coefficient (W/m2 K), A = area of heat transfer (m2 ), ∆T = difference between temperature average fluid temperature and average helical coil temperature (K) Nusselt number, Nu can be calculated by using the relations, K hD Nu h)(  (2) Nu = Nusselt Number, h = heat transfer coefficient, Dh = hydraulic diameter, k = thermal conductivity The heat transfer coefficient, nusselt number are calculated for the tube in tube helical heat exchanger and further compared with straight tube in tube heat exchanger. 3.2. Numerical Simulation The CFD software ANSYS Fluent 14.0 was used to solve the governing equations of mass, momentum and heat transfer. The tube in tube helical heat exchanger was modeled in ANSYS fluent geometry module, then the meshing of the model was done in ANSYS fluent meshing module. In order to get good results fine mesh was employed, hexahedral and tetrahedral mesh was used for the model. Also at high temperature region near boundaries we employed structured hexahedral mesh. The k- Ɛ standard turbulence model was used as the viscous model suggested by Wang and Chen. In the simulation of the turbulent flow, simple scheme algorithm for pressure velocity coupling was used. The assumptions used for the simulation of the helical heat exchanger are: 1. The flow is steady and incompressible. 2. Radiation and natural convection effects are ignored. 3. Constant wall temperature at the boundary. The inputs are given at the two inlets of the inner tube and outer tube. The conservation equations were solved for the control volume to yield the velocity and temperature fields for the fluid flow in the model. The model was converged when all the residuals fell below 10-6 in the computational domain.
  • 5. Numerical Simulation of a Tube 5213 Results and discussions The CFD simulation was done for the three different mass flow rates of water respectively for both straight and helical tube ranging from 0.2kg/s to 0.7kg/s. Reynolds number corresponding to these mass flow rates were varying from 4000 to 9000. The parameters that are adopted for comparison are temperature of water at the outlet, heat transfer rate, nusselt number, pressure drop and heat transfer coefficient. The flow of fluid in helical coil is shown in the figure 2, the fluid particles moves towards the outer wall then returns to the inner portion of tube by flowing back along the wall. The figure 3 shows the close view of the velocity vectors, the fluid in the curve of the tube moves towards the outer wall and then returns to the inner portion of tube by flowing back along the wall. Figure 4 shows the temperature contour for the helical tube in tube. It can be seen that temperature drop for helical tube in tube is higher than the straight tube, which is due to the curvature effect of the helical shape of the coil. Fluid flow in the outer layer of the tube in tube moves faster than the fluid flow in the inner layer due this a secondary flow is set which enhances the heat transfer. Figure 5 shows the temperature contour for the straight tube in tube, it shows the temperature drop in the inner tube from inlet to outlet. Figure 6 and 7 shows the variation of heat transfer coefficient for different mass flow rates for the inner and outer tube of helical and straight tube in tube heat exchanger. From the graph it is clear that as mass flow rate increases heat transfer coefficient also increases as expected since heat transfer rate is proportional to the mass flow rate. The heat transfer coefficient for helical tube in tube shows a remarkable increase of heat transfer coefficient by 10.5% when compared to the straight tube in tube heat exchanger. Figure 8 and 9 shows the variation of inner tube and outer tube nusselt number for helical and straight tube in tube heat exchanger. Nusselt numbers corresponding to the helical is higher than the straight tube in tube for all mass flow rates. This is due to the secondary flow in the helical tube in tube which aids the heat transfer. The nusselt number increased by 10.9% for helical tube in tube when compared to straight tube in tube for a particular mass flow rate. In the helical coils at higher mass flow rates the Reynolds number increases and the fluid turbulence also increases. Thereby due to higher turbulence the intensity of secondary flow increases and hence nusselt number. Figure 10 shows the variation of pressure drop over the entire length of helical tube in tube heat exchanger. From the figure 11 it is clear that the pressure drop in helical tube in tube is higher than that in straight tube in tube, this is due to the centrifugal force and secondary flow in helical tube in tube. Secondary flow dissipates kinetic energy which increases the resistance to flow. The present study was validated from the literature work done by Soumya Ranjan, 2013. Figure 12 shows the Total pressure at different points along the pipe length for the outer wall were checked and an accuracy of 94.56% was achieved.
  • 6. 5214 Soby P. Sunny et al Figure 2. Velocity vectors colored by velocity magnitude (m/s) Figure 3. Close view of velocity vectors of helical tube in tube
  • 7. Numerical Simulation of a Tube 5215 Figure 4. Contours of static temperature in K of helical tube in tube Figure 5. Contours of static temperature for inner tube of straight tube in tube
  • 8. 5216 Soby P. Sunny et al Figure 6: Variation of heat transfer coefficient with mass flow rate for inner tube of helical and straight tube in tube Figure 7: Variation of heat transfer coefficient with mass flow rate for outer tube of helical and straight tube in tube
  • 9. Numerical Simulation of a Tube 5217 Figure 8: Variation of Nusselt Number with mass flow rate for inner tube of helical and straight tube in tube Figure 9: Variation of Nusselt number with mass flow rate for outer tube of helical and straight tube in tube
  • 10. 5218 Soby P. Sunny et al Figure 10: Pressure drop along the length of the helical tube in tube Figure 11: Total Pressure Plot for outer wall of helical tube in tube and straight tube in tube
  • 11. Numerical Simulation of a Tube 5219 Figure 12: Total Pressure Plot for outer wall of helical tube in tube Conclusion In this present work CFD simulation for helical tube in tube heat exchanger was carried out and the results of heat transfer parameters have been compared with the straight tube in tube under same geometrical and operating conditions. The CFD results are validated with the literature work, the results achieved were well within the error limits. Simulation results indicated that heat transfer rate, nusselt number and heat transfer coefficient are higher in case of helical tube in tube when compared with the straight tube in tube. For different mass flow rates, the helical tube in tube heat exchanger provides an increase in heat transfer coefficient by 10.5%. The pressure drop for helical coil tube in tube is found to be more when compared with the straight tube in tube for identical conditions and varies exponentially indicating the necessity of higher pumping power for helical tube in tube heat exchanger. Table 2: Nomenclature Nomenclature Re, Reynolds number Dh, Hydraulic Diameter (m) Q, Heat transfer rate (W) Nu, Nusselt Number A, Area of heat transfer (m2 ) k, Thermal conductivity (W/mK) ∆T, Temperature difference (K) ∆P, Pressure drop (Pa) 6. References [1] Prabhanjan D.G., Raghavan G.S.V., and Rennie T.J., “Comparison of heat transfer rates between a straight tube heat exchanger and a helically coiled heat exchanger”, Heat and mass transfer, Vol. 29, No. 2, (2002), pp.185-191.
  • 12. 5220 Soby P. Sunny et al [2] Prabhanjan D.G., Raghavan G.S.V., and Rennie T.J., “Natural convection heat transfer from helical coiled tubes”, International Journal of Science, Vol. 43, No. 4, (2004), pp. 359-365. [3] Timothy J.R., Vijaya G.S., “Numerical studies of a double-pipe helical heat exchanger”, Applied Thermal Engineering, Vol. 26, (2006), pp. 1266-1273. [4] J.S. Jayakumar, S.M. Mahajani, J.C. Mandal, “Experimental and CFD estimation of heat transfer in helically coiled heat exchangers”, Chemical engineering research and design, Vol. 86, (2008), pp. 221-232. [5] Pramod S. P., Mandar M. L., Rajkumar G., “Parametric analysis of helical coil heat exchanger”, International Journal of Engineering Research & Technology, Vol.1, Issue 8, (2012), pp. 1-5. [6] M. P. Fakoor-Pakdaman, M.A. Akhavan-Behabadi, P. Razi, “An empirical study on the pressure drop characteristics of Nano fluid flow inside helically coiled tubes” International Journal of Thermal Sciences, Vol. 65, (2013), pp. 206-213. [7] Soumya R.M., “CFD analysis of heat transfer in a helical coil heat exchanger using fluent”, Maser Thesis, NIT Rourkela, India, (2013), pp. 1-33.