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Title: Entrainment of refrigerated air curtains down a wall

Abstract

Refrigerated air curtains are used in open supermarket display cases as a barrier between the warm ambient air and the cold refrigerated air. Entrainment of ambient air into the curtain by shear layer mixing contributes to both the sensible and the latent heat load on the display case. To better understand the fluid dynamics which govern entrainment, velocity and temperature measurements of the curtains were made in a refrigerated display case, which was modified to allow a more fundamental flow. In particular, a vertical solid wall was installed to approximately represent a fully-stocked configuration. As such, negatively-buoyant wall jets (with high inflow turbulence) in the Reynolds number range of 4200-8000 and in the Richardson number range of 0.13-0.58 were examined. To define the air curtain vortex structures, flow visualization of the curtain interface was employed. The results of which showed that the entrainment of the ambient air was found to be governed by a variety of eddy engulfing structures. Particle Image Velocimetry was used to examine the velocity profiles of the air curtains in a non-intrusive manner, the measurements of which indicated negatively-buoyant acceleration following the jet exhaust, followed by a more linear curtain growth characteristic of isothermal wall jets.more » In addition, thermocouples were used to obtain the net increase in temperature of the curtain due to entrainment, where it was found that the dimensionless thermal energy loss decreased with decreasing Reynolds number.« less

Authors:
;  [1]
  1. Department of Aerospace Engineering, University of Illinois, Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)
Publication Date:
OSTI Identifier:
20685975
Resource Type:
Journal Article
Resource Relation:
Journal Name: Experimental Thermal and Fluid Science; Journal Volume: 30; Journal Issue: 3; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; AIR CURTAINS; GAS FLOW; FREEZERS; REFRIGERATORS; COMMERCIAL BUILDINGS; COOLING LOAD; VORTICES; VELOCITY

Citation Formats

Field, Brandon S., and Loth, Eric. Entrainment of refrigerated air curtains down a wall. United States: N. p., 2006. Web. doi:10.1016/j.expthermflusci.2004.01.012.
Field, Brandon S., & Loth, Eric. Entrainment of refrigerated air curtains down a wall. United States. doi:10.1016/j.expthermflusci.2004.01.012.
Field, Brandon S., and Loth, Eric. Sun . "Entrainment of refrigerated air curtains down a wall". United States. doi:10.1016/j.expthermflusci.2004.01.012.
@article{osti_20685975,
title = {Entrainment of refrigerated air curtains down a wall},
author = {Field, Brandon S. and Loth, Eric},
abstractNote = {Refrigerated air curtains are used in open supermarket display cases as a barrier between the warm ambient air and the cold refrigerated air. Entrainment of ambient air into the curtain by shear layer mixing contributes to both the sensible and the latent heat load on the display case. To better understand the fluid dynamics which govern entrainment, velocity and temperature measurements of the curtains were made in a refrigerated display case, which was modified to allow a more fundamental flow. In particular, a vertical solid wall was installed to approximately represent a fully-stocked configuration. As such, negatively-buoyant wall jets (with high inflow turbulence) in the Reynolds number range of 4200-8000 and in the Richardson number range of 0.13-0.58 were examined. To define the air curtain vortex structures, flow visualization of the curtain interface was employed. The results of which showed that the entrainment of the ambient air was found to be governed by a variety of eddy engulfing structures. Particle Image Velocimetry was used to examine the velocity profiles of the air curtains in a non-intrusive manner, the measurements of which indicated negatively-buoyant acceleration following the jet exhaust, followed by a more linear curtain growth characteristic of isothermal wall jets. In addition, thermocouples were used to obtain the net increase in temperature of the curtain due to entrainment, where it was found that the dimensionless thermal energy loss decreased with decreasing Reynolds number.},
doi = {10.1016/j.expthermflusci.2004.01.012},
journal = {Experimental Thermal and Fluid Science},
number = 3,
volume = 30,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}