312 Meat refrigeration is to install a plant that is smaller than needed and recalculate the extended cooling times that will occur, still meeting the chilling/freezing specification. When the refrigeration load increases above that at which the refrigeration plant can extract air, temperature in the chiller/freezer will rise. As the air temperature rises two things happen: the product load is reduced and he capacity of the refrigeration plant will increase. The effect of these two changes is that after a time a balance is achieved when the load arising from the carcasses is extracted by the plant and cooling can then continue in the normal way until the temperature is reduced back down to its original level. If data were available on cooling during pull-down it would be possible to calculate the extended cooling periods, check whether these fitted with the other user requirements and still install a refrigeration plant which would meet an agreed specification Another option is to spread the loading time of the chiller/freezer over a longer period, and so reduce the peak product loads. However, this decreasing productivity, and is therefore rarely used of the abattoir, with Whatever decision is taken, the peak product load that the refrigeration plant is expected to accommodate should be clearly stated in the agreed ngineering specification and a load profile should also be given to ensure that the refrigeration designer provides a plant that will run efficiently over the entire product load range 15.2.5 Relative humidity The relative humidity in the chill room must also be defined in the engi- neering specification. When the chiller is empty and the latent heat load negligible, relative humidity depends upon the evaporation temperature The wet bulb temperature will slowly be reduced until it approaches evapo ration temperature, at which point no more water will be extracted from the room and the humidity will remain stable. As the latent heat load in the room increases from the loading of warm wet carcasses, the amount of water vapour evaporated increases the relative humidity in the room. The relationship between latent heat load and relative humidity depends upon wo factors: the design of the evaporator coil and plant cycling. Only an infi nitely deep coil will produce discharged air with a wet bulb temperature equal to the evaporator temperature During refrigeration plant off-cycles, no water is extracted from the air and the relative humidity will rise, only to be pulled down again when the refrigeration plant is switched back on. Therefore, to obtain a high relative humidity in the room to reduce weight loss during the latter parts of chilling and storage, a high evaporation tem perature and a large coil area are needed. This ensures that the refrigera tion plant runs for only very short periods of time and when it is running it only extracts the minimum amount of water from the Since humidity is normally only important in the latter stages of chilling,is to install a plant that is smaller than needed and recalculate the extended cooling times that will occur, still meeting the chilling/freezing specification. When the refrigeration load increases above that at which the refrigeration plant can extract air, temperature in the chiller/freezer will rise. As the air temperature rises two things happen: the product load is reduced and the capacity of the refrigeration plant will increase. The effect of these two changes is that after a time a balance is achieved when the load arising from the carcasses is extracted by the plant and cooling can then continue in the normal way until the temperature is reduced back down to its original level. If data were available on cooling during pull-down it would be possible to recalculate the extended cooling periods, check whether these fitted with the other user requirements and still install a refrigeration plant which would meet an agreed specification. Another option is to spread the loading time of the chiller/freezer over a longer period, and so reduce the peak product loads. However, this normally causes disruption in the planned operation of the abattoir, with decreasing productivity, and is therefore rarely used. Whatever decision is taken, the peak product load that the refrigeration plant is expected to accommodate should be clearly stated in the agreed engineering specification and a load profile should also be given to ensure that the refrigeration designer provides a plant that will run efficiently over the entire product load range. 15.2.5 Relative humidity The relative humidity in the chill room must also be defined in the engi￾neering specification. When the chiller is empty and the latent heat load negligible, relative humidity depends upon the evaporation temperature. The wet bulb temperature will slowly be reduced until it approaches evapo￾ration temperature, at which point no more water will be extracted from the room and the humidity will remain stable. As the latent heat load in the room increases from the loading of warm wet carcasses, the amount of water vapour evaporated increases the relative humidity in the room. The relationship between latent heat load and relative humidity depends upon two factors: the design of the evaporator coil and plant cycling. Only an infi- nitely deep coil will produce discharged air with a wet bulb temperature equal to the evaporator temperature. During refrigeration plant off-cycles, no water is extracted from the air and the relative humidity will rise, only to be pulled down again when the refrigeration plant is switched back on. Therefore, to obtain a high relative humidity in the room to reduce weight loss during the latter parts of chilling and storage, a high evaporation tem￾perature and a large coil area are needed. This ensures that the refrigera￾tion plant runs for only very short periods of time and when it is running it only extracts the minimum amount of water from the air. Since humidity is normally only important in the latter stages of chilling, 312 Meat refrigeration