Thermohydraulic efficiency assessment for pulsating fluid flow in channels
2021
Sidenko, S., Riga Technical Univ. (Latvia) | Dzelzitis, E., Riga Technical Univ. (Latvia) | Sidenko, N., Riga Technical Univ. (Latvia)
Superimposed flow pulsations promote heat transfer intensification. Usage of such flows allows to increase the thermal characteristics aimed at the energy saving. However, the question of the thermohydraulic efficiency of this method remains open, since there are little data of changing in hydraulic resistance in the case of non-isothermal pulsating flow in the channels. To solve this problem, CAD/CFD software SolidWorks/ FlowSimulation was used. Smooth and profiled channels were investigated. A model of periodically pulsating fluid flow in channels with sinusoidal velocity pulses was considered. Pulsating frequency range was set from 0 to 30 Hz. The results showed that a periodic change in the Reynolds number leads to a change in the value of hydraulic resistance over time. At a flow pulsation frequency of 0.5 ≤ f ≤ 5 Hz and 2.8 ≤ lgRe ≤ 3.5 for a smooth channel there are characteristic zones of a laminar (Re≈2000) and transient flow regime (Re = 2000–4000), and a turbulent zone at 3.5 ≤ lgRe ≤ 4.7. With increasing of the flow pulsations frequency f is greater than 5 Hz, there are no zones of laminar and transient regimes, and the flow can be characterized as a stabilized turbulent flow. In contrast to the pulsating flow in a smooth channel, in a profiled channel a stabilized turbulent flow appears already at a pulsation frequency f = 2 Hz (Sh = 0.09). The relative coefficient of hydraulic resistance for non-isothermal fluid movement in a profiled channel is 10−15% higher than in a smooth one. Increasing in the thermohydraulic efficiency, both in smooth and profiled channels, can reach up to 20–40%.
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