Inlet tube spacing and protrusion inlet effects on multiple circular tubes in the laminar, transitional and turbulent flow regimes

Abstract

Highlights • Inlet effects of tube spacing and a protrusion inlet on transitional flow. • Inlet flow maldistribution delayed and decreased the transitional flow regime. • Decreased tube spacing led to increased maldistribution. • Free convection dampened maldistribution effect for a square-edged inlet. • Free convection did not dampen maldistribution effect due to protrusion inlet.

Heat transfer and pressure drop characteristics of alternating clockwise and counter clockwise twisted tape inserts in the transitional flow regime

“…8(a) The same trends were found in the friction factor results ( Fig. 8(b) and Table 3), the results of the other connection angles, as well as previous studies [57,59,[65][66][67][68][69].…”

“…The data reduction methodology followed was in general the same as in refs [57,[65][66][67][68][69].…”

Influence of inlet contraction ratios on the heat transfer and pressure drop characteristics of single-phase flow in smooth circular tubes in the transitional flow regime

“…The transitional flow regime has been receiving great attention in recent years due to its good compromise between high heat transfer and low pressure drop [1], making it a potential heat exchanger operating flow regime. Several articles [2][3][4][5][6][7][8][9][10][11][12][13][14] have been published in recent years on the characteristic behaviour of heat transfer and pressure drop in the transitional flow regime under various operating conditions. The influence of heating, buoyancy, inclination and inlet geometry on the transition from laminar to turbulent flow regimes were extensively investigated.…”

“…Meyer and his co-workers were the second group of researchers that worked on the characteristic behaviour of heat transfer and pressure drop in the transitional flow regime of smooth and enhanced tubes, focussing on inlet geometry effects [9,10,21,22], buoyancy effects [7,11,23], inclination angles [23], enhancement with twisted tape inserts [9,24,25] and annular flow [26]. These analyses involved both cooling and heating conditions under constant wall temperature and constant heat flux boundary conditions, mostly with flow-calming sections and different inlet contraction ratios.…”

“…Different flow-calming section diameters with a constant test section diameter would lead to different inlet disturbances, especially with square-edged and re-entrant inlets [2,11,18,22].…”