Effectiveness and optimum jet velocity for a plane jet air curtain used to restrict cold room infiltration

In the present work, computational modeling and simulations of isothermal plane (linear) air jet velocity profile for slot diffusers are performed. Plane air jets are formed by linear slots or rectangular openings with a large aspect ratio. Numerical simulations are performed using the commercial computational fluid dynamics (CFD) code ANSYS FLUENT. Three plane air jet flow simulations will be investigated such as free plane (linear) jets, attached jets, and air flow through a slot diffuser in a room setting. The purpose of simulating the free plane jet through a slot diffuser is to study the behavior of jet velocity profile that is not blocked by side walls or ceilings. The jet velocity profile is modified when obstructed by the walls and the air jet desires to attach to the surfaces along its path. For this reason, attached jet simulations through a slot diffuser will be conducted. The CFD study of plane air jet flows will eventually be extended to jet flows through a slot diffuser to a room to investigate the fluid flow behavior that enters a room under a ceiling. In addition, effects of two-equation turbulence models such as standard, renormalization group (RNG), and realizable k-ε on the CFD simulations will be investigated. Predicted velocity profiles and decays of free plane jet through a slot diffuser will be validated with a semi-empirical model [1]. Predicted velocity profiles of attached jet simulations will also be compared with a semi-empirical expression [2]. The slot diffuser air flow simulations will be compared with experimental data by the work of Chen and Srebric [3]. All simulations will be conducted at a specified inlet air velocity. The effects of grid resolution are also examined. It is established that the standard k-ε turbulence model best simulates attached and free jet flows. The standard k-ε turbulence model is applied to a room setting under isothermal conditions. The results are compared with non-isothermal experimental data [3]. It is shown that temperature which is a passive scalar has less influence on the flow pattern at a high air velocity than at a low air velocity in a room setting.

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The Numerical Simulation and Research and Application of Energy-Saving Effect of Hot Air Curtain Jet Velocity of the Dining Room

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.919-921.1744 ◽

2014 ◽

Vol 919-921 ◽

pp. 1744-1747

Author(s):

Kun Ru Ma ◽

Xin Wang

Keyword(s):

Numerical Simulation ◽

Energy Saving ◽

Physical Model ◽

Outdoor Air ◽

Air Curtain ◽

Hot Air ◽

Jet Velocity ◽

Dining Room ◽

Set Up ◽

Saving Effect

There are often people and goods in and out of the dinning room door, so the door is often open. Heating and air conditioning construction to save energy and to prevent the outdoor air form influencing on indoor environment, set up the air curtain at the entrance of the dinning room to stop outdoor air, the frequently-used air curtain is beam type of air curtain.The project in view of the dinning room of the new campus of hebei university of science and technology, sets up air curtain physical model of the ground floor dining room door at the first area, and carry on reasonable simplification, make sure the numerical simulation calculation area and the sealing condition of air curtain. Then set up physical model for wind pressure, multiply of hot pressure and the local hot pressure at the dinning room door of the air curtain air flow in CFD method. Through the numerical simulation for different jet velocity of the hot air curtain, analysis the temperature field, velocity field, heat loss,heat load parameter, etc. and demonstrate the energy saving effect, and provide reference basis for the selection of air curtain.

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Evaluation of Horizontal Recirculatory Air Curtain Efficiencies: Cooler to Conditioned Space

ASME 2014 Citrus Engineering Conference ◽

10.1115/cec2014-5801 ◽

2014 ◽

Author(s):

Daniel J. Rhyner

Keyword(s):

Energy Transfer ◽

Energy Loss ◽

Cold Storage ◽

Theoretical Calculations ◽

Energy Losses ◽

Tracer Gas ◽

Environmental Chamber ◽

Air Curtain ◽

Cold Room ◽

Chamber Size

Air curtains have long been used to reduce losses from high traffic doorways in cold storage facilities. Different varieties of air curtains have been used including vertical (down blast) non-recirculatory, horizontal non-recirculatory and horizontal recirculatory. The effectiveness of air curtains to provide thermal separation between rooms of differing temperatures has long been a matter of debate. Previous experiments have been done to determine the effectiveness using tracer gas decay methods. This paper will evaluate the thermal effectiveness of the horizontal recirculatory air curtain when applied in a typical cooler application using an environmental chamber. This allowed testing of the air curtain’s ability to reduce infiltration on the actual thermal envelope. A vertical non-recirculatory air curtain was also evaluated for comparison purposes. The air curtains were tested in an environmental chamber that was divided into two rooms of differing temperature. The chamber was instrumented to measure all energy transfer into and out of each room. The cold room was maintained at a temperature of 4°C (39°F) and the warm room was maintained at a temperature of 24°C (75°F) and 60% RH throughout all tests. Three phases of testing were conducted for each air curtain to completely evaluate all energy losses — a completely closed doorway test for calibration, a completely open doorway test with no air curtains and an open doorway test with the air curtains adjusted and running. Completion of the testing revealed the horizontal recirculatory air curtain had a thermal efficiency of 71% while the vertical non-recirculatory air curtain had an efficiency of 38%. The results were slightly lower than theoretical calculations which may be attributable to chamber size. Additional tests were conducted using a smaller doorway for comparison. Applying the results from the smaller doorway yields an effectiveness of 76.2%. Using the theoretical open doorway energy loss yields an effectiveness of 80%. Paper published with permission.

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Effect of Air Curtain on Flow Regimes and Heat Transfer characteristics in a Refrigerated Cold Room

51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition ◽

10.2514/6.2013-1192 ◽

2013 ◽

Author(s):

Essam Khalil ◽

Gamal Elhariry ◽

Ahmed Mostafa

Keyword(s):

Heat Transfer ◽

Flow Regimes ◽

Heat Transfer Characteristics ◽

Air Curtain ◽

Transfer Characteristics ◽

Cold Room

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Verification of computational calculations based on physical tests of plane jet used to separate zones full of smoke

Budownictwo i Architektura ◽

10.35784/bud-arch.2112 ◽

2013 ◽

Vol 12 (2) ◽

pp. 135-141

Author(s):

Grzegorz Krajewski

Keyword(s):

Pressure Drop ◽

Scale Model ◽

Air Curtain ◽

Computational Calculations ◽

Physical Tests ◽

Flow Through ◽

Plane Jet ◽

Real Scale ◽

Thin Nozzle ◽

Transversal Flow

The aim of this paper is to take advantage of CFD application in calculating, optimizing, and designing air barriers used to separate smoke free zones in the case of fire. Properly designed air curtain produces a pressure drop which forbides transversal flow through the opening. It is hard to make a good quality CFD calculation of that kind of air curtain because of high velocity and relatively thin nozzle. Most air curtains are tested on scaled down models which are difficult to extrapolate. The author of this article performed tests in a real scale model. Tests results were used to verify chosen turbulence model. The intention of this paper is to present the comparison between CFD calculations and tests results.

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