Jet entrainment minimization in an air curtain of open refrigerated display case

Navaz, Homayun K.; Amin, Mazyar; Rasipuram, Srinivasan C.; Faramarzi, Ramin

doi:10.1108/09615530610653064

Cited by 13 publications

(4 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 4 shows the velocity profile at different Reynolds numbers. It is shown [12] that the Top-Hat profile is the best practical profile that can exist at the DAG for reducing the infiltration rate. Carbon dioxide (CO 2 ) has been used as the tracer gas in the current work.…”

Section: Resultsmentioning

confidence: 99%

“…They have shown that this hybrid approach can effectively quantify the effect of individual flow/geometrical parameters on the air curtain performance. They have also mentioned that certain operating conditions can result in improved performance of an air curtain [12,13]. Field et al [14,15] studied circulating air curtains of a display case by the PIV visualization.…”

Section: Nomenclaturementioning

confidence: 99%

See 1 more Smart Citation

Air curtains of open refrigerated display cases revisited: a new technique for infiltration rate measurements

Amin¹,

Navaz

Dabiri³

et al. 2008

WIT Transactions on Engineering Sciences

View full text Add to dashboard Cite

Air curtains are created in open refrigerated vertical display cases for creating an invisible barrier between the cold air inside and the warm air outside the case. A systematic approach is developed to minimize the entrainment and infiltration of warm air into the case by optimizing the performance of an air curtain through adjusting pertinent flow parameters and case geometry. A modular display case was manufactured for the parametric studies. In this modular display case the geometry and flow parameters were changed and the infiltration rate was measured using a new technique, tracer gas method, which could be performed noticeably faster than the conventional methods. This apparatus is referred to as the proof-of-concept air curtain (POCAC). A matrix of all possible permutations was constructed with the infiltration rate being the outcome of this matrix. This matrix was populated by actual experimental measurements as well as using validated Computational Fluid Dynamics (CFD) computer programs as a tool to acquire better resolution of the input and output datasets. All the problem variables are referred to as the input vector of all parameters that can be altered, and the output is the infiltration rate. An artificial neural network (ANN) program was used to provide the linkage between the input vector (problem variables) and the problem outcome (infiltration). This program can also be used by industry as a tool to estimate the infiltration rate for all existing open vertical display cases.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Nomenclaturementioning

confidence: 99%

Air curtains of open refrigerated display cases revisited: a new technique for infiltration rate measurements

Amin¹,

Navaz

Dabiri³

et al. 2008

WIT Transactions on Engineering Sciences

View full text Add to dashboard Cite

show abstract

“…Obviously, the amount of infiltrated warm air should be kept to a minimum to conserve energy for running the cooling cycle to maintain a prescribed cold air temperature that is being driven to the DAG and the back panel. There have been numerous studies by Navaz et al (2002Navaz et al ( , 2004Navaz et al ( , 2006aNavaz et al ( , b, 2007a to identify parameters that can affect the infiltration rate in open refrigerated display cases. They have used a hybrid numerical and experimental approach to calculate the infiltration rate of the warm air into these display cases.…”

Section: Application Of Ann To An Open Refrigerated Display Case-steamentioning

confidence: 99%

A Systematic Approach for Solving Large-Scale Problems by Neural Network: Open Refrigerated Display Cases and Droplet Evaporation Problems

Amin

Navaz

Kehtarnavaz

et al. 2008

Food Bioprocess Technol

Self Cite

View full text Add to dashboard Cite

A systematic approach for solving a large-scale design problem is proposed. The method consists of building a multidimensional test case matrix connecting an output (scalar or vector) to an input vector. Every element of the input vector spans over its possible minimum and maximum values with one or more levels in between. The experimental and validated computational methods are combined to find the output as a function of all permutations of the input variables. The results are used to train a neural network program to perform the proper interpolation for any other expected scenario. The number of required experiments is obtained asymptotically by adding more data to the neural network training set and examining the error. The applicability and feasibility of this approach is shown in two different problems: first, predicting and minimizing the infiltration rate into an open refrigerated display case; and second, predicting the evaporation rate of sessile microdroplets on a nonpermeable surface.

show abstract

“…This year Navaz et al [32] have presented a work to address the effects of velocity profile at the discharge air grill on the amount of entrained air into an open refrigerated display case. The study was carried out using experimental techniques (DPIV and LDV) and also by means of CFD simulations.…”

Section: Cui and Wangmentioning

confidence: 99%

Numerical study and experimental optimization of air curtains

Giráldez García

View full text Add to dashboard Cite

The main objective of the present thesis is to study and optimize the sealing efficiency of air curtains. Therefore, the phenomenology of the breakthrough and the parameters which affect it has been studied. However, considering the level of turbulence in the studied flowfields, this work employs numerical methods which will allow us to take all the transport phenomena into account, for both laminar and turbulent regimes. This is not the first effort within the {\sc cttc} (``Centre Tecnològic de Transferència de Calor'') research group on this subject, but the continuation of a research activity carried out in the past years. For this purpose, chapter 1 contains an introduction to air curtains, and the basic phenomenology is discussed. The different stages of an air jet are detailed. It is also given a discussion on when the installation of these devices should be considered as a good solution for air flow sealing. In this chapter are also defined the basic concepts used throughout this work. It ends with a brief description of the three main approaches employed in this thesis to analyse air curtains: computational fluid dynamics, semianalytical methods and experimental measurements. The semianalytycal methods, which are suitable only for steady regime calculations, are introduced in chapter 2. In this chapter it is also described the interface developed at Centre Tecnològic de Transferència de Calor to evaluate the thermal efficiency and other relevant aspects for different configurations of air curtains. The main results obtained in such geometries are also presented. The semiananlytycal approach allows to characterize the air curtains with a much less time consuming method than higher level calculations. In chapter 3, the Computational Fluid Dynamics methodology is described, with Large Eddy Simulation as approach. The models employed to solve the Navier Stokes equations are Smagorinsky and Wale. A simmetry preserving discretization is employed. The solvers employed are also outlined. Finally, illustrative results obtained with the air curtain under several conditions are presented. In chapter 4 special emphasis has been placed on the experimental measurements of actual air curtains. This interest resulted on a detailed study about the standard on the characterization of air curtains, and the construction of an experimental set up according the standard requirements.The more significant results are presented. In chapter 5 a plenum optimization procedure is carried out. Both experimental and numerical approaches are employed. In chapter 6 the appplication of air curtains to refrigerating chambers is studied in detail. The results obtained from CFD simulation, semianalytical calculations and experimental measurements have been compared. According to the results obtained and presented the objective of optimizing air curtains proposed in this thesis have been satisfied. El principal objetivo de la presente tesis es el estudio y la optimización de cortinas de aire. Para ello, la fenomenologia de la ruptura y los parametros que la afectan han sido estudiados. Considerando el nivel de turbulencia en los flujos estudiados, este trabajo emplea metodos numericos que permiten tener en cuenta los fenomenos de transporte, tanto en regimenes laminar como turbulento. Esta no es la primera labor de investugación en este campo llevada a cabo en el Centro Tecnologico de Transferencia de Calor, sino la continuación de una labor llevada a cabo durante los ultimos años. E el capitulo 1 se presenta una introduccion a las cortinas de aire, y se presenta su física básica. Las diferentes regiones del jet son detalladas. También se discuten las situaciones en las cuales se han de emplear estos dispositivos. Se realiza un breve resumen de los metodos que se emplearán: semianaliticos, CFD y mediciones experimentales. En el capitulo 2 se presentan los metodos semianaliticos, que son aplicables tan solo a situaciones de regimen permanente. En este capitulo se describen las ecuaciones que nutren la interfaz desarrollada en el Centro Tecnologico de Transferencia de Calor para evaluar la eficiencia y otros aspectos de interés en diferentes configuraciones de estos dispositivos. El enfoque semianalitico permite obtener resultados en tiempos de cálculo menores que con métodos numericos de más alto nivel. En el capitulo 3 se presenta la metodologia CFD empleada, con Large Eddy Simulation como enfoque. El modelo de turbulencia empleado es WALE. Una discretización symmetry prreserving es empleada, Los solvers empleados también se detallan. En el capitulo 4 se han presentado las mediciones experimentales de prototipos reales. Se ha estudiado con detalle el estandard internacional AMCA de caracterización de cortinas. los resultados más significantes son presentados. En el capitulo 5 se presenta el proceso de optimización de un plenum. Se emplean enfoques tanto experimental como numerico. En el capitulo 6 la aplicación de las cortinas de aire a salas refrigeradas se ha estudiado con detalle. Contrastando los resultados obtenidos con los diferentes enfoques se puede concluir que se han alcanzado los objetivos de optimización y estudio propuestos en la presente tesis.

show abstract

Jet entrainment minimization in an air curtain of open refrigerated display case

Cited by 13 publications

References 3 publications

Air curtains of open refrigerated display cases revisited: a new technique for infiltration rate measurements

Air curtains of open refrigerated display cases revisited: a new technique for infiltration rate measurements

A Systematic Approach for Solving Large-Scale Problems by Neural Network: Open Refrigerated Display Cases and Droplet Evaporation Problems

Numerical study and experimental optimization of air curtains

Contact Info

Product

Resources

About