Local Heat Transfer Dynamics in the In-Line Tube Bundle under Asymmetrical Pulsating Flow

Abstract

The pulsating flow is one of the techniques that can enhance heat transfer, therefore leading to energy saving in tubular heat exchangers. This paper investigated the heat transfer and flow characteristics in a two-dimensional in-line tube bundle with the pulsating flow by a numerical method using the Ansys Fluent. Numerical simulation was performed for the Reynolds number Re = 500 with different frequencies and amplitude of pulsation. Heat transfer enhancement was estimated from the central tube of the tube bundle. Pulsation velocity had an asymmetrical character with a reciprocating flow. The technique developed by the authors to obtain asymmetric pulsations was used. This technique allows simulating an asymmetric flow in heat exchangers equipped with a pulsation generation system. Increase in both the amplitude and the frequency of the pulsations had a significant effect on the heat transfer enhancement. Heat transfer enhancement is mainly observed in the front and back of the cylinder. At a steady flow in these areas, heat transfer is minimal due to the weak circulation of the flow. The increase in heat transfer in the front and back of the cylinder is associated with increased velocity and additional flow mixing in these areas. The maximum increase in the Nusselt number averaged over space and time in the entire studied range was 106%, at a pulsation frequency of 0.5 Hz and pulsation amplitude of 4.5. A minimum enhancement of 25% was observed at a frequency of 0.166 Hz and amplitude of 1.25.

Heat Transfer in 3D Laguerre–Voronoi Open-Cell Foams under Pulsating Flow

“…Figure 13 shows the ratios of the Nusselt number averaged over one period of pulsation for the various porosities, Reynolds numbers, and duty cycles of pulsation. An increase in the intensity of pulsations (A/D s )St leads to an increase in the Nusselt number ratio, which is consistent with the data of other researchers [18,19,22,28,29,49,58]. The intensification of heat transfer is associated with a decrease in the boundary layer, an increase in local velocities, homogenization, and, additionally, more intense mixing of the flow [28,49].…”

“…The nature of the flow was consistent with the flow with the pulsations in the tube bundles [49]. Haibullina et al [49] studied asymmetric pulsations in an inline tube bundle at a Reynolds number of 500. Pulsating flows in the VF have some similarities with pulsating flows in tube bundles, while the flow has a three-dimensional structure with unsteady vortex separation at the lower Reynolds number.…”

“…An in- Due to flow pulsations, a constant restructuring of the flow occurred, which led to the equalization of velocities with a decrease in local stagnant zones. The nature of the flow was consistent with the flow with the pulsations in the tube bundles [49]. Haibullina et al [49] studied asymmetric pulsations in an inline tube bundle at a Reynolds number of 500.…”

“…In all the studies mentioned in the review, the flow pulsations are symmetrical. The pulsations can be both symmetric and asymmetric [49]. The heat transfer enhancement with asymmetric pulsations can exceed symmetrical pulsations.…”

Cooling of Concentrated Photovoltaic Cells—A Review and the Perspective of Pulsating Flow Cooling

“…In pulsating flow, Equation (5) gives the Reynolds number associated with the oscillating Re ω and the stable components Re s [90]. The pulsating velocity is given by u s = v(1 + ksinωt), k = 2π f A o /v refers to as waviness of the flow, where v is the average velocity [94], A o = u s D h /υ [95], f = 1/T is the frequency of pulsation, and T = T 1 + T 2 is the period where T 1 and T 2 are the first and second-half periods of pulsating [96].…”