236 Meat refrigeration temperatures will be recorded. The difficulty of achieving this requirement has already been described in papers by Marriott(1992)and Gigiel and ames(1992). These two papers also clearly reveal the need for test proce- dures that will relate to the likely performance of the cabinets within the retail environment When the products do not meet the required temperatures it is often the air curtain that is to blame. The air curtain isible and so it needs to be made visible to check that it is doing what is required. Smoke is probably the most used method to view the air curtain. When smoke is blown into the air curtain it can be clearly seen. The cabinet can now be modified and its effect viewed using smoke 11.1.5 Computer modelling Developing a cabinet can be a very lengthy process. The cabinet tempera tures are not steady with time, as the cabinets coil ices up and then defrosts Any movement in front of the cabinet will have an effect on the air curtain and product temperatures. Any changes made to the cabinet may not have an immediate effect on product temperatures, therefore a number of small changes to a display cabinet can be a time-consuming and costly process Computational fluid dynamics(CFD)is becoming widely accepted as tool that can be used to aid development of display cabinets. CFD alloy the user to make changes to a computer model of the cabinet and see its effect before changing the real thing. If computing resources allow it,a number of changes can be made to a computer model relatively quickly and the best case tried on a real cabinet. mpt CFD has been used to show the effect of removing shelves from a retail display cabinet( Foster, 1995).A two-dimensional model of a chilled cabinet was used to predict the effect of removing shelves from the cabinet(Fig 11. 2). The predictions showed that the refrigeration consumption was least (570w per metre length of cabinet) when the case was fully loaded. As shelves were removed from either the top downwards or bottom upwards the energy consumption increased to a maximum of 653 Wm when all of he shelves were removed. CFD predictions of the cabinet with different configurations of shelving demonstrate that when shelves are removed, pressure differences between the cold cabinet and the store cause the curtain to bend inwards. This causes more mixing between the cold and warm air, increasing product temperature, reducing store temperatures and Increasing energy consumption 11.1.6 Store conditions One factor that can greatly effect the operation of a retail display cabinet is its positioning relative to the store's heating and ventilation system ( Foster, 1997). Because of the cold feet effect, supermarket stores are keentemperatures will be recorded.’ The difficulty of achieving this requirement has already been described in papers by Marriott (1992) and Gigiel and James (1992). These two papers also clearly reveal the need for test proce￾dures that will relate to the likely performance of the cabinets within the retail environment. When the products do not meet the required temperatures it is often the air curtain that is to blame. The air curtain is invisible and so it needs to be made visible to check that it is doing what is required. Smoke is probably the most used method to view the air curtain. When smoke is blown into the air curtain it can be clearly seen. The cabinet can now be modified and its effect viewed using smoke. 11.1.5 Computer modelling Developing a cabinet can be a very lengthy process. The cabinet tempera￾tures are not steady with time, as the cabinet’s coil ices up and then defrosts. Any movement in front of the cabinet will have an effect on the air curtain and product temperatures. Any changes made to the cabinet may not have an immediate effect on product temperatures, therefore a number of small changes to a display cabinet can be a time-consuming and costly process. Computational fluid dynamics (CFD) is becoming widely accepted as a tool that can be used to aid development of display cabinets. CFD allows the user to make changes to a computer model of the cabinet and see its effect before changing the real thing. If computing resources allow it, a number of changes can be made to a computer model relatively quickly and the best case tried on a real cabinet. CFD has been used to show the effect of removing shelves from a retail display cabinet (Foster, 1995).A two-dimensional model of a chilled cabinet was used to predict the effect of removing shelves from the cabinet (Fig. 11.2). The predictions showed that the refrigeration consumption was least (570 W per metre length of cabinet) when the case was fully loaded. As shelves were removed from either the top downwards or bottom upwards, the energy consumption increased to a maximum of 653 W m-1 when all of the shelves were removed. CFD predictions of the cabinet with different configurations of shelving demonstrate that when shelves are removed, pressure differences between the cold cabinet and the store cause the air curtain to bend inwards. This causes more mixing between the cold and warm air, increasing product temperature, reducing store temperatures and increasing energy consumption. 11.1.6 Store conditions One factor that can greatly effect the operation of a retail display cabinet is its positioning relative to the store’s heating and ventilation system (Foster, 1997). Because of the cold feet effect, supermarket stores are keen 236 Meat refrigeration