The use of CFD for predicting buoyant and forced convection flows occurring in food refrigeration

Abstract

Being able to maintain the temperature of food is of vital importance to ensure optimal food quality, safety and shelf life. Most unwrapped food and all types of wrapped foods are stored in large refrigerated rooms with forced air circulation. A reduction in the average storage temperature can significantly increase the length of retention and quality of many chilled foods. Air infiltration through entrances can account for more than half the total heat load for refrigerated stores.
Chilled foods are often transported to supermarkets where they are then displayed in open fronted refrigerated display cabinets. These cabinets are one of the weakest links in the chilled food chain with large temperature ranges between products in the same cabinet. This range in temperature causes problems for food manufacturers when defining shelf life and results in shelf lives that are either unduly cautious or potentially risky.
The aim of this thesis was to use CFD to solve problems encountered in the food/refrigeration industry. It describes the use of CFD for two separate problems (cold store door opening and open fronted refrigerated display cabinets) which are caused by the same physical phenomena (natural convection between air at different temperatures).
CFD predictions of unprotected entrances give a significant improvement in accuracy over the fundamental analytical equations. Factors such as the extent of the ambient domain that needs to be modelled are an important consideration in gaining accurate predictions. A 2D CFD model was able to predict the effectiveness of an air curtain; however, the predictions were higher than measured. A 3D CFD model was able to provide a better prediction of effectiveness and optimum jet velocity than the 2D model. This thesis highlights the importance of setting up a cold store air curtain properly, if it is to work at its optimum efficiency.

Date of Award	30 Jul 2007
Original language	English
Awarding Institution	University of Bristol
Supervisor	Michael J Tierney (Supervisor)