Effects of internal surface roughness and viscous friction on mass flow rate and conductive heat transfer across a pipe element: Simulink Approach

The study, effects of internal surface roughness and viscous friction on mass flow rate and conductive heat transfer across a pipe element using simulink approach was successfully achieved. Block models were used to represent all the elements of pipe flow model.  Pipe element was modeled to retain hydraulic diameter of 0.4 m within a length of 100 m. The shape factor and internal surface roughness were chosen to be 80 and 3e+3m, respectively. Initial temperature and pressure were set to 300k or 27 ºC and 1 atm. turbulent regime Nusselt number correlation coefficients were 0.023, 0.8, 0.33, 0, and 0. The mass flow rate from the reservoir had initial value of 0.6 kg/s and signal block was adjusted to 1, 6, 5 for slope, start and maximum respectively. With Ode15s solver, simulation was allowed to run for 15seconds. System model mass flow rate, conductive heat transfer and temperature difference were found to be 0.6kg/s (same with initial value), 5.0346 x 10⁶ J/s and -80K or 193ºC within 15seconds of simulation. Findings depicted the effects of internal surface roughness and viscous friction on mass flow rate and conductive heat transfer. Also, simulation was run with the shape factor and internal surface roughness chosen to be 64 and 1.5e-5m, respectively. Under viscous friction influence, initial temperature and pressure were set to 298k or 25ºC and 1 atm. turbulent regime Nusselt number correlation coefficients were 0.023, 0.8, 0.33, 0, and 0. The mass flow rate from the reservoir had initial value of 0.6 kg/s. Results also showed that the system model mass flow rate, conductive heat transfer and temperature difference were found to be 0.058kg/s, -275J/s and 100K or -173ºC within 15seconds of simulation. Hence, increasing value of internal surface roughness increases conductive heat transfer at a constant mass flow rate of fluid and increasing value of viscous friction, decreases mass flow rate of fluid as well as conductive heat transfer across the pipe wall.