Influences of pitch-length louvered strip insert on thermal characteristic in concentric pipe heat exchanger

Abstract

Abstract. The effects of pitch-length louvered strip inserts with a forward arrangement on heat transfer and friction factor characteristics in a concentric pipe heat exchanger were experimentally investigated. Louvered strip insert was installed inside the tube. For comparison, the experiment without louvered strip (plain tube) was conducted. All cases were tested under steady state condition for Reynolds number ranging from 5300-17,500. The results show that the utilization of louvered strip insert produced a higher heat transfer rate compare to a plain tube. Nusselt number, friction factor, and heat transfer coefficient ratio increased with decreasing pitch length. The Nusset number for louvered strip insert with S of 40, 50, and 60 mm increasing in the value of 67% -77%; 48% -53%; and 21% -24% than plain tube, respectively. While the tube fitted with louvered strip insert by S of 40, 50, and 60 mm, friction factor increased 2.91 -3.84; 2.41 -2.92; and 1.88 -2.08 times greater than a plain tube. The addition of louvered strip insert with S of 40, 50, and 60 mm producing heat transfer coefficient ratio in the range of 1.02 -1.12; 1.03 -1.07 and 1.03 -1.04.

Computational Fluid Dynamics Analysis of an Enhanced Tube with Backward Louvered Strip Insert

“…Re, and therefore also the convective heat transfer, improved accordingly. These results are in coherence with previously conducted studies [13][14][15]. Figure 5 also shows that, for backward louvered strip inserts, a pitch S of 40 mm provided the highest Nu and was followed by those of 50 and 60 mm.…”

“…Moreover, as represented in Figures 5 and 10, the present calculation provides the correlation of the Nu and f to Re, respectively. The tendency is considered consistent with the experimental results from previous works [13][14][15]. It is reasonable that the backward louvered strip inserts can give a higher friction factor compared to the forward design [14] because the fluid flow is directly blocked by the louvered strip inserts with the backward arrangement.…”

“…Most published reports on heat transfer augmentation by louvered strip inserts are experimental studies, which are lacking the evidence to describe the mechanism of both fluid flow and heat transfer. Hence, after studying and publishing the research works in [13,14], we were strongly motivated to continue the work to a numerical analysis of the thermal hydraulic performance inside an enhanced tube equipped with a louvered strip insert with various pitches for turbulent single-phase flow. This is the reason that this work is believed to be able to give a novel academic contribution, especially when compared with the currently available and previously published studies.…”

Experimental analysis to study the effect of perforated louvered strip‐coiled spring insert on heat transfer performance in a double pipe heat exchanger

“…Nowadays, the most commonly used turbulators are twisted tapes (TTs), [2][3][4][5][6][7] swirl generating curved conical turbulators, 8 wire coils (WCs), [9][10][11][12][13][14][15][16][17][18][19][20] perforated inserts, [2][3][4][5][6][7][21][22][23][24] and so forth. Out of so many different shapes and sized inserts, the louvered strips (LS) 21,22,[25][26][27][28][29][30][31] turbulator is one of them. LS looks like ellipticalshaped leaves that are mounted on a small diameter core rod.…”

“…The maximum positive result was seen with , the corresponding increase in heat transfer ratio was between 1.03 and 1.12. Yaningsih and Wijayanta 30 have experimented with deducing the effect of different pitches of LS on thermohydraulic properties inside a tube. It has been observed that Nu and f both increase as pitch values of LS decreased, and maximum enhancement of 1.12 in heat transfer was reported for 40 mm pitched LS insert.…”