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ABSTRACT
To enhance overall thermal performance factor of tubular heat exchanger, use of twisted tape has been very effective. Twisted tape creates turbulence in the flow which enhances rate of heat transfer and friction factor. Present experimental study aims to limit this penalty of increase in friction factor and achieve high thermal performance factor. For this, present article analyzes the effect of different design modifications in twisted tape on thermo-hydraulic performance of heat exchanger tube. Different inserts, i.e. Simple Twisted tape (STT), Double V-Cut Twisted Tape (DVCTT) and Perforated Double V-Cut Twisted Tape (PDVCTT), of varying twist ratio (TR) 3, 4 and 5 are considered for the investigation. Further design modification such as V-cut with width of cut (wc) 5 mm, depth of cut (dc) 4 mm, and perforation of 5 mm diameter is produced in twisted tape. Water is used as the working fluid for the study. Data pertaining to Nusselt number and friction factor is collected for the analysis in turbulent region where Reynolds number varied from 4000 to 16,000. Maximum enhancement in Nusselt number and friction factor is recorded 2.44 times and 3.71 times of plain tube respectively at Re = 4000 in case of TR = 3. Further PDVCTT leads to maximum decrement in Nusselt number and friction factor 3.83% and 27.35% when compared with DVCTT. Maximum thermal performance obtained is 1.71 in case of PDVCTT with TR of 3 at Re = 4000.
Nomenclature
| A | = | Convection heat transfer area(m2) |
| cp | = | Specific heat capacity(J/kg-K) |
| D | = | Inner diameter of tube(m) |
| h | = | Coefficient of heat transfer(W/m2K) |
| k | = | Thermal conductivity(W/m-K) |
| L | = | Length of test section(m) |
| m | = | Mass flow rate(kg/s) |
| Nu | = | Nusselt number |
| p | = | Pitch of twisted tape(m) |
| P | = | Pressure(Pa) |
| p/w | = | Twist Ratio |
| Pr | = | Prandtl number |
| Q | = | Rate of heat transfer(W) |
| Re | = | Reynolds number |
| T | = | Temperature(K) |
| t | = | Thickness of twisted tape(m) |
| U | = | Mean flow velocity(m/s) |
| w | = | Width of twisted tape(m) |
| Greek symbols | = | |
| ρ | = | Density(kg/m3) |
| ƞ | = | Thermal performance factor |
| µ | = | Viscosity(kg/m-s) |
| Subscript | = | |
| b | = | Bulk |
| c | = | Convection |
| h | = | Surface |
| i | = | Inlet |
| o | = | Outlet |
| p | = | Plain |
| w | = | Water |
| Abbreviations | = | |
| ATSG | = | Alternatively twisted swirl generator |
| DVCTT | = | Double V-Cut Twisted Tape |
| HEx | = | Heat Exchanger |
| LPM | = | Litre Per Minute |
| PDVCTT | = | Perforated Double V-Cut Twisted Tape |
| PT | = | Plain Tube |
| STT | = | Simple Twisted Tape |
| TR | = | Twist Ratio |
| TT | = | Twisted Tape |
| TPF | = | Thermal Performance Factor |
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Notes on contributors
Prashant Kumar
Prashant Kumar is a Ph.D. scholar in Department of Mechanical Engineering at Maulana Azad National Institute of Technology, Bhopal, India. He has received an M. Tech degree from the Maulana Azad National Institute of Technology, Bhopal, India. His research fields include computational fluid dynamics, heat transfer and nanofluid.
R. M. Sarviya
R. M. Sarviya is a Professor in Department of Mechanical Engineering at Maulana Azad National Institute of Technology, Bhopal, India. He has received his Ph.D. from the Indian Institute of Technology, Roorkee, India. His research fields include heat transfer, thermal engineering, and solar energy. He has undergone research-training experience at Rediff University (UK), University of Wales (Cardiff, UK), and University of Salford (Manchester, UK). He has published more than 125 papers. He has guided 14 Ph.D. and presented papers in many countries at conferences.