Specifying, designing and optimising refrigeration systems 31 20 Door open. Time(h) Fig. 15.2 An example of a refrigeration load profile for a beef chiller. 15.2.4 Refrigeration plant capacity The capacity of the refrigeration plant must now be decided. will the peak heat load be met? If so the planned chilling times and the specification agreed will be achieved. If not, the desired schedule will not be attained but there will be a saving in the capital costs of the refrigeration plant and more economical running will be achieved since the plant will be running at less than quarter capacity for over 71% of the time. Large refrigeration plants working at low loads are very inefficient and therefore very costly to run. If a smaller plant is used, it will have a smaller turn-down ratio and efficiency at part load, the majority of time that it will run, will be higher. therefore saving operating costs There are some possible solutions to the designer's dilemma If refrig eration capacity is demanded elsewhere in the plant, but at different times, he provision of a central plant serving both facilities can make use of this diversity. It is therefore important at this stage to look at the refrigeration load profile for the entire plant -there may be blast freezers which are only operated well after the time that the peak chilling load has passed and by careful design a refrigeration plant may be installed and shared between both facilities. However, this only applies to a part of the pla the compressors and condensers, and not the evaporators. Another solution15.2.4 Refrigeration plant capacity The capacity of the refrigeration plant must now be decided. Will the peak heat load be met? If so the planned chilling times and the specification agreed will be achieved. If not, the desired schedule will not be attained, but there will be a saving in the capital costs of the refrigeration plant and more economical running will be achieved since the plant will be running at less than quarter capacity for over 71% of the time. Large refrigeration plants working at low loads are very inefficient and therefore very costly to run. If a smaller plant is used, it will have a smaller turn-down ratio and its efficiency at part load, the majority of time that it will run, will be higher, therefore saving operating costs. There are some possible solutions to the designer’s dilemma. If refrig￾eration capacity is demanded elsewhere in the plant, but at different times, the provision of a central plant serving both facilities can make use of this diversity. It is therefore important at this stage to look at the refrigeration load profile for the entire plant – there may be blast freezers which are only operated well after the time that the peak chilling load has passed and by careful design a refrigeration plant may be installed and shared between both facilities. However, this only applies to a part of the refrigeration plant, the compressors and condensers, and not the evaporators. Another solution Specifying, designing and optimising refrigeration systems 311 Load Chillier Door open. unload/ washoown Unloading Load profile 80 60 40 20 0 0 20 30 40 48 10 Time (h) Fig. 15.2 An example of a refrigeration load profile for a beef chiller