Mitigation of Flow Maldistribution in Minichannel and Minigap Heat Exchangers by Introducing Threshold in Manifolds

Abstract

In the present paper, a detailed numerical investigation has been carried out to analyze the flow maldistribution in 50 parallel rectangular cross-section (1 mm depth and 1 mm width) minichannels and minigap section (1 mm depth and 99 mm width) with rectangular/trapezoidal manifolds in Z-type flow configuration. The author carried out numerical investigation with various mass flow rates, namely 0.05 kg/s, 0.1 kg/s and 0.2 kg/s which results in Reynolds number of 1532, 3064, 6128 respectively. A novel approach for the mitigation of non-uniform flow has been proposed introducing threshold at the entrance of the minigeometry section. The conventional case without threshold (as reference) and 1 mm, 3 mm and 7 mm threshold were introduced. The threshold has been employed by making a manifolds' depth bigger than section's depth. The maldistribution coefficient can be reduced twice in minigap section or three times in the minichannel section already with the 1 mm threshold as compared to the arrangement without threshold. It is found that rectangular manifold gives lower maldistribution coefficient than trapezoidal manifold which corresponds with actual state of the art. The distribution is more uniform in minichannel section than in minigap section for the same inlet parameters. To obtain uniform distribution of fluid flow should be stabilized already at the inlet manifold, at the entrance to the minichannel or minigap section. That was done by introducing the threshold in the manifolds, which is novelty of this study.

Experimentally Verified Flow Distribution Model for a Composite Modelling System

“…The observed maximal relative difference of 4.91% between analytically and numerically predicted flow rates indicates that Model BJ-Mod might be suitable for minichannel applications. A pilot study of possible utilization of analytical models for minigap geometries was conducted using the numerical data reported on the Z-system by Dąbrowski [29]. Dąbrowski's paper covers numerous cases of minigap geometries and inlet flow rates, of which three are discussed here.…”

“…In all three cases, the inlet mass flow rate was 0.05 kg/s, which corresponded in the discretized branches to the Reynolds number of 1950. For the sake of consistency, the following figures show the obtained A pilot study of possible utilization of analytical models for minigap geometries was conducted using the numerical data reported on the Z-system by D ąbrowski [29]. D ąbrowski's paper covers numerous cases of minigap geometries and inlet flow rates, of which three are discussed here.…”

“…In all three cases, the inlet mass flow rate was 0.05 kg/s, which corresponded in the discretized branches to the Reynolds number of 1950. For the sake of consistency, the following figures show the obtained normalized velocities (ratio of fluid velocity in the i-th branch and the average value) and the local maldistribution coefficient (12) together with those provided by the respective study [29].…”

“…The authors concluded that pressure drop increased more significantly with a higher mass flow rate in the minichannel system, yet the obtained heat transfer coefficient was also higher in the minichannel system than in the minigap of the same size. Results of D ąbrowski's analyses [29] then showed similarities in flow distribution trends between minichannel and minigap systems, although minigap systems provided much worse flow uniformity.…”

Tailoring the fluid flow distribution in a parallel mini-channel heat sink under multiple-peak heat flux

“…Their results showed that the triangular inlet header and the trapezoidal outlet header provided better flow uniformity than others. Many other novel header designs [11,[14][15][16][17] have also been proposed and tested, as summarized in the review paper by Ghani et al [18]. Different from the studies on the inlet header shapes, Song et al [19] proposed to add a staggered pin-fin array in the inlet header of the watercooled heat sink.…”