306 Meat refrigeration be in a single stage, in which case steady values will be specified, or they may be time dependent, as in a multi-stage process. In choosing the proce conditions there will be an interaction with the earlier specified constraints. Some compromise may be needed, adjusting the time available for the process in order to obtain an optimal solution. Once the process conditions re fixed and the throughput and materials specified, the product load will also be fixed although this may not always be known. Where design data exist, they should be utilised to specify the product load Other refrigeration loads also need to be specified. Many of these, such as infiltration through openings, the use of lights, machinery and people working in the refrigerated space, are all under the control of the user and must be specified so that the heat load given off by them can be incorpo- rated in the final design. Ideally, all the loads should then be summed ime basis to produce a load profile. If the refrigeration ess is to be incorporated with all other processes within a plant, in orde to achieve an economic solution, the load profile is important The ambient design conditions must be specified. These refer to the temperatures adjacent to the refrigerated equipment and the temperatures of the ambient surroundings to which heat will ultimately be rejected. In stand-alone refrigerated processes this will often be the wet and dry bulb emperatures of the outside air. If the process is to be integrated with heat reclamation then the temperature of the heat sinks must be specified Finally, the defrost regime should also be specified. There are times in any process where it is critical that a defrost does not take place and that the oil is cleared of frost before commencing this part of the process. The above requirements should all be specified by the end-user. It ommon practice throughout European industry to leave much of this specification to refrigeration contractors or engineering specialists. Often they are in a position to give good advice on this. However, since all the above are outside their control, the final decision should always be taken by the end-user, using their knowledge of how well they can control their overall process. 15.2 ngineering specification The aim of drawing up an engineering specification is to turn the process- ing conditions into a specification that any refrigeration engineer can then construct and deliver without knowledge of the meat process involved. If he first part of the process specification has been completed, the engi neering specification will be largely in place. It consists of the environmen- tal conditions within the refrigerated enclosure, air temperature, air velocity ind humidity(the way the air will move within the refrigerated enclosure), the size of the equipment, the refrigeration load profile, the ambient design conditions and the defrost requirements. The final phase of the engineeringbe in a single stage, in which case steady values will be specified, or they may be time dependent, as in a multi-stage process. In choosing the process conditions there will be an interaction with the earlier specified constraints. Some compromise may be needed, adjusting the time available for the process in order to obtain an optimal solution. Once the process conditions are fixed and the throughput and materials specified, the product load will also be fixed although this may not always be known. Where design data exist, they should be utilised to specify the product load. Other refrigeration loads also need to be specified. Many of these, such as infiltration through openings, the use of lights, machinery and people working in the refrigerated space, are all under the control of the user and must be specified so that the heat load given off by them can be incorpo￾rated in the final design. Ideally, all the loads should then be summed together on a time basis to produce a load profile. If the refrigeration process is to be incorporated with all other processes within a plant, in order to achieve an economic solution, the load profile is important. The ambient design conditions must be specified. These refer to the temperatures adjacent to the refrigerated equipment and the temperatures of the ambient surroundings to which heat will ultimately be rejected. In stand-alone refrigerated processes this will often be the wet and dry bulb temperatures of the outside air. If the process is to be integrated with heat reclamation then the temperature of the heat sinks must be specified. Finally, the defrost regime should also be specified. There are times in any process where it is critical that a defrost does not take place and that the coil is cleared of frost before commencing this part of the process. The above requirements should all be specified by the end-user. It is common practice throughout European industry to leave much of this specification to refrigeration contractors or engineering specialists. Often they are in a position to give good advice on this. However, since all the above are outside their control, the final decision should always be taken by the end-user, using their knowledge of how well they can control their overall process. 15.2 Engineering specification The aim of drawing up an engineering specification is to turn the process￾ing conditions into a specification that any refrigeration engineer can then construct and deliver without knowledge of the meat process involved. If the first part of the process specification has been completed, the engi￾neering specification will be largely in place. It consists of the environmen￾tal conditions within the refrigerated enclosure, air temperature, air velocity and humidity (the way the air will move within the refrigerated enclosure), the size of the equipment, the refrigeration load profile, the ambient design conditions and the defrost requirements. The final phase of the engineering 306 Meat refrigeration