Heat Transfer Through Vertically Downward-Blowing Single-Jet Air Curtains for Cold Rooms

Belleghem, Marnix Van; Verhaeghe, Gregory; T’Joen, Christophe; Huisseune, Henk; Jaeger, Peter De; Paepe, Michel De

doi:10.1080/01457632.2012.677724

Cited by 33 publications

(11 citation statements)

References 20 publications

(22 reference statements)

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“…In addition, the values of γ sf = M jet,sf /M cf are provided, which are the values of γ min corrected by a safety factor of 2, as recommended in previous studies (e.g. Stoecker 1969a, Foster et al 2006;Van Belleghem et al 2012). Moreover, a comparison is provided between these values of γ min and the values of the optimal momentum flux ratios γ CFD = M jet,CFD /M cf as obtained from the CFD simulations (see Table 1 with the values of γ for four jet height-to-width ratios and for four jet discharge angles).…”

Section: Deflection Modulusmentioning

confidence: 99%

Minimum momentum flux ratio required to prevent air curtain breakthrough in case of cross-curtain pressure gradients: CFD versus analytical equation

Khayrullina¹,

Hooff

Ruiz

et al. 2020

Build. Simul.

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This paper presents a numerical study on the required momentum flux ratio to prevent air curtain breakthrough in case of cross-curtain (i.e. cross-jet) pressure gradients. 2D steady Reynolds-averaged Navier-Stokes (RANS) CFD simulations with the RNG k-ε turbulence model are employed for jet Reynolds numbers ranging from 5,000 to 30,000. First, the computational model is validated based on particle image velocimetry (PIV) measurements. Second, the influence of several jet parameters on the separation efficiency is evaluated for a moderate cross-jet pressure difference of 10 Pa. These are the ratio of the jet discharge momentum flux to the jet cross-flow momentum flux (momentum flux ratio), the jet height-to-width ratio and the jet discharge angle. Finally, the minimum deflection modulus to prevent jet breakthrough and the corresponding momentum flux ratio by an analytical equation and by CFD are compared. The results show that, for the configuration under study: (1) jets with the smallest height-to-width ratios (β = 18) provide the highest separation efficiency; (2) inclined jets with discharge angles α0 = 5° and 10° provide slightly higher separation efficiency than straight jets (α0 = 0°) and jets with α0 = 20°; (3) the maximum modified separation efficiency is reached at lower momentum flux ratios for jets with smaller height-to-width ratios and for inclined jets; (4) the analytical and CFD values of the optimal momentum flux ratio differ with up to 31.2%. This study shows how the separation efficiency of air curtains can be improved by adjusting certain jet parameters.

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Section: Deflection Modulusmentioning

confidence: 99%

Minimum momentum flux ratio required to prevent air curtain breakthrough in case of cross-curtain pressure gradients: CFD versus analytical equation

Khayrullina¹,

Hooff

Ruiz

et al. 2020

Build. Simul.

View full text Add to dashboard Cite

show abstract

“…Another typical application is the confinement of cold rooms, as it allows the energy consumption reduction of the cooling equipment in applications where the cooled space needs to be open, such as retail stores or commercial display cabinets. This type of application has been deeply assessed, analytically [23], numerically and experimentally [24].…”

Section: Air Curtains Possible Use In Stentersmentioning

confidence: 99%

Heat Recovery for a Textile Stenter: CFD Analysis of Air Curtain Benefits

et al. 2019

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Modern textile stenters are designed to reduce the inefficiency of the process and to recover the flow stream, which still contains a relatively high energetic value. In recent years, research has focused on the recovery of the energy content of the low-temperature exhaust flow; nonetheless, another important aspect that may increase the efficiency of the process is the reduction of the ambient air suction. In the present research, an innovative way to improve both machine insulation and energy savings, by using preheated air, was numerically evaluated. The proposed solution utilizes an air stream transverse to the fabric (generally called air curtain), either preheated or not, to create soft gates both at the inlet and at the outlet section of the drying machine. Several valuable advantages can be listed when using this solution: reduction of the dispersion of heat and humid polluted air to the work environment, limitation of air ingestion from outside, and effective heat recovery coupled to a uniform temperature profile around the textile fabric. To analyze the insulation capability of the air curtains in terms of mass and energy transfer, a two-dimensional CFD model of the machine was realized. A test matrix including three possible fabric speeds (20, 40 and 60 m/min), three tilt angles (−15°, 0° and 15°), four mass flow rates (0% with no air curtains and 3%, 5% and 7% of the total flow rate through the machine, where the 5% case is equivalent to the flow rate ingested from the ambient) and two temperatures (15 °C and 70 °C) of the plane jets exiting from the air curtains was considered, thus covering a wide range of possible practical applications. The obtained results demonstrate that warm air curtains at both the inlet and outlet are very effective in a fabric speed range up to 40 m/min; at higher fabric speed, entrainment of warm gases from inside the machine at the fabric outlet becomes relevant, and the adoption of a cold air curtain (capable of better insulation) can be recommended in this position.

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“…As indicated in the above-mentioned overview of previous studies, different indicators have been used to mark the performance of ACs, including heat transfer correlations [8,25,[34][35][36][37]43,44], infiltration or mass transfer correlations [8,26,38,39,41,42], concentration distributions [4,45], temperature distributions [46,47] and jet stability parameters [28,48,49]. However, the most commonly used performance indicator in both the scientific literature and the industry is the 'separation/sealing efficiency' (or 'separation effectiveness') η s (e.g., Ref.…”

Section: Introductionmentioning

confidence: 99%

“…However, the most commonly used performance indicator in both the scientific literature and the industry is the 'separation/sealing efficiency' (or 'separation effectiveness') η s (e.g., Ref. [2,4,6,8,[25][26][27][29][30][31][34][35][36][37]40,43,46,49,50]). This parameter is based on the heat or mass flow across an opening with AC as compared to the same opening without AC:…”

Section: Introductionmentioning

confidence: 99%

Air curtain performance: Introducing the adapted separation efficiency

Ruiz

Hooff

Blocken

et al. 2021

Building and Environment

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Heat Transfer Through Vertically Downward-Blowing Single-Jet Air Curtains for Cold Rooms

Abstract: One of the major sources of heat gain in refrigerated storage rooms is the infiltrationFinally, an expression to estimate the heat transfer rate through the air curtain is proposed.

Cited by 33 publications

References 20 publications

Minimum momentum flux ratio required to prevent air curtain breakthrough in case of cross-curtain pressure gradients: CFD versus analytical equation

Minimum momentum flux ratio required to prevent air curtain breakthrough in case of cross-curtain pressure gradients: CFD versus analytical equation

Heat Recovery for a Textile Stenter: CFD Analysis of Air Curtain Benefits

Air curtain performance: Introducing the adapted separation efficiency

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