Transportation 199 → No food 0 mm to 5 kw 42186420 50100150200 Fig 9.4 Heat extracted by the refrigeration plant during the standard journey for vans with different thickness of insulation, with and without food(source refrigeration system, the vehicles construction, the air movement within he vehicle, the external environment, the operation of the vehicle and the temperature of the foodstuff. a project recently completed by the Food Refrigeration and Process Engineering Research Centre(FRPERC)as part of a MAFF LINK scheme has produced a predictive model that will assist fleet operators in specifying the design of and the equipment for small delivery vehicles(Gigiel, 1998) Refrigerated vehicles are developed and tested in carefully controlled conditions. Owing to the large number of interacting variables, as many as possible are held constant during the tests. The prediction programme allows for systematic alteration of one or more variables whilst simulating the operation of a vehicle in a complex, realistic way. The verified model has provided valuable data on the factors influenc- ing food temperature and van performance. 93. 4. Van insulation The heat extracted by the refrigeration system during the journey is she plotted against the thickness of insulation in Fig. 9.4. Only a small thickness of insulation greatly reduces the amount of heat that has to be extracted, the amount decreasing with the reciprocal of the thickness of insulation. In all cases, van and food temperatures were maintained at less than 5C. This was only achieved in the case with no insulation by fitting the vehicle with a refrigeration system with a nominal capacity of 10kW. The food in the van modified the action of the thermostat and reduced the running time of he refrigeration system and the heat extracted by it. The reduction was 43% when the insulation was 75 mm thick 9.3. 4.2 Infiltration The heat extracted from a poorly sealed van was 86% more than from a well-sealed van(Fig. 9.5). However, infiltration during the time that therefrigeration system, the vehicle’s construction, the air movement within the vehicle, the external environment, the operation of the vehicle and the temperature of the foodstuff. A project recently completed by the Food Refrigeration and Process Engineering Research Centre (FRPERC) as part of a MAFF LINK scheme has produced a predictive model that will assist fleet operators in specifying the design of and the equipment for small delivery vehicles (Gigiel, 1998). Refrigerated vehicles are developed and tested in carefully controlled conditions. Owing to the large number of interacting variables, as many as possible are held constant during the tests. The prediction programme allows for systematic alteration of one or more variables whilst simulating the operation of a vehicle in a complex, realistic way. The verified model has provided valuable data on the factors influenc￾ing food temperature and van performance. 9.3.4.1 Van insulation The heat extracted by the refrigeration system during the journey is shown plotted against the thickness of insulation in Fig. 9.4. Only a small thickness of insulation greatly reduces the amount of heat that has to be extracted, the amount decreasing with the reciprocal of the thickness of insulation. In all cases, van and food temperatures were maintained at less than 5 °C. This was only achieved in the case with no insulation by fitting the vehicle with a refrigeration system with a nominal capacity of 10 kW. The food in the van modified the action of the thermostat and reduced the running time of the refrigeration system and the heat extracted by it. The reduction was 43% when the insulation was 75 mm thick. 9.3.4.2 Infiltration The heat extracted from a poorly sealed van was 86% more than from a well-sealed van (Fig. 9.5). However, infiltration during the time that the Transportation 199 2 1.8 0.8 0.6 0.2 0.4 0 0 1.6 1.4 1.2 1 50 100 150 200 No food 1 tonne food 0 mm to 5 kW Thickness (mm) Heat extracted (J) Fig. 9.4 Heat extracted by the refrigeration plant during the standard journey for vans with different thickness of insulation, with and without food (source: Gigiel, 1998)