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ABSTRACT
Heat transfer enhancement is an essential parameter of heat exchangers, that can increase by increasing the value of heat transfer coefficient. So, researchers used different types of inserts, in which, single strip helical screw tape showed excellent enhancement in heat transfer, due to the formation of high-intensity swirl flow. However, to increase more intensity of swirl flow, Double strip helical screw tape inserts (DS-HST) used in present work. An experimental analysis is carried out to analyze thermal and friction factor characteristics of fluid flow in heat exchanger tube, with DS-HST, at twist ratio of 1.5, 2.5, and 3, in the range of Reynolds number from 4000 to 16000, at constant heat flux condition. Experimental results showed that Nusselt number and friction factor achieved excellent enhancement with double strip helical screw tape insert than single strip helical screw tape insert (SS-HST) with decreasing value of twist ratio. The correlation developed for Nusselt number at a range of Reynolds number, twist ratio and a number of strips. Moreover, Thermal performance factor achieved maximum value at twist ratio of 2.5 and 3 for DS-HST, than SS-HST inserts in the higher values of Reynolds number, at constant pumping power. So this range of turbulent flow showed the suitability of DS-HST inserts, which can reduce the size of heat exchangers or thermal applications, utilize energy resources, and decrease pollution in the environment.
Nomenclature
| A | = | Surface area of heat transfer, m2 |
| D | = | Tube’s inside diameter, mm |
| h | = | Heat transfer coefficient, W/m2K |
| k | = | Fluid’s thermal conductivity, |
| L | = | Test section length, m |
| m | = | mass flow rate, Kg/s |
| Nu | = | Nusselt Number |
| d | = | Diameter of insert rod |
| δ | = | Twist tape Strip thickness, mm |
| P | = | Pressure, kPa |
| ΔP | = | Pressure drop, kPa |
| = | Prandtl Number | |
| Q | = | Rate of heat transfer, W |
| Re | = | Reynolds Number |
| t | = | Thickness of the test tube, mm |
| T | = | Temperature, ºC |
| ΔT | = | Temperature difference, ºC |
| V | = | Mean axial flow velocity, m/s |
| W | = | width of twist tape, mm |
| N | = | Number of strips of insert |
| cp | = | Fluids’s specific heat,kJ/kg-K |
| H | = | Pitch, m |
| y | = | Twist ratio (H/D) |
Greek Symbols
| ρ | = | Density of fluid, |
| η | = | Thermal performance factor |
| µ | = | Dynamic viscosity, |
Subscripts
| c | = | convection |
| b | = | bulk |
| o | = | outlet |
| i | = | inlet |
| s | = | surface |
| p | = | plain |
| w | = | water |
| t | = | twist |
Abbreviations
| PT | = | Plain tube |
Additional information
Notes on contributors
Shashank Ranjan Chaurasia
Shashank Ranjan Chaurasia is a Ph.D. scholar in Department of Mechanical Engineering at Maulana Azad National Institute of Technology, Bhopal, India. He has received M. Tech degree in Thermal Engineering from Maulana Azad National Institute of Technology, Bhopal, India. His research field is in combustion, pulse jet engine, heat transfer enhancement and CFD analysis.
R. M. Sarviya
R. M. Sarviya is serving as Professor in Department of Mechanical Engineering at Maulana Azad National Institute of Technology, Bhopal, India. He has received his Ph.D. from Indian Institute of Technology, Roorkee, India. His research interest includes Heat Transfer and Thermal Engineering. He has held the post of Head of Mechanical Engineering Department, Chairman Energy Centre and Dean (SW) at Maulana Azad National Institute of Technology, Bhopal, India. He has many Papers in international Journal and conferences. He has a research experience at Rediff University (UK), University of Wales (Cardiff, UK), University of Salford (Manchester, UK). He presented many Papers in conferences at different countries.