Question

Consider the freezing of packaged meat in boxes with refrigerated air. How do \((a)\) the temperature of air, \((b)\) the velocity of air, \((c)\) the capacity of the refrigeration system, and \((d)\) the size of the meat boxes affect the freezing time?

Short answer

Answer: The freezing time of packaged meat is affected by the following factors: 1. Air temperature: Lower air temperatures result in faster heat transfer and faster freezing times, while higher air temperatures result in slower heat transfer and increased freezing times. 2. Air velocity: Higher air velocities increase the rate of heat transfer, leading to faster freezing times. Lower air velocities result in slower heat transfer and increased freezing times. 3. Refrigeration system capacity: A system with a higher capacity can remove heat more efficiently, reducing freezing time. A system with a lower capacity takes longer to reach and maintain the desired air temperature, increasing freezing time. 4. Meat box size: Larger meat boxes take longer to freeze due to their greater mass and larger surface area, while smaller meat boxes freeze more quickly due to their lower mass and smaller surface area.

Step-by-step solution

Effect of Air Temperature

The temperature of the refrigerated air is a critical factor in determining freezing time. Lower air temperatures will result in faster heat transfer from the meat, thus reducing the time it takes for the meat to reach the freezing point. Conversely, higher air temperatures will result in slower heat transfer and increase the freezing time.

Effect of Air Velocity

The velocity of the air flowing around the meat boxes also plays a significant role in the freezing process. Higher air velocities will result in an increased rate of heat transfer due to the reduction in the thickness of the thermal boundary layer around the meat. This will lead to faster freezing times. On the other hand, lower air velocities will result in slower heat transfer and increased freezing times.

Effect of Refrigeration System Capacity

The capacity of the refrigeration system will also impact the freezing time. A refrigeration system with a greater capacity can remove heat from the air more efficiently, which will reduce the time taken in reaching the desired air temperature and maintaining it, resulting in faster freezing times. Conversely, a refrigeration system with a lower capacity will take longer to reach and maintain the desired air temperature, increasing the freezing time.

Effect of Meat Box Size

The size of the meat boxes affects the freezing time because larger meat boxes have a greater mass and take longer to freeze. The larger the meat box, the more heat that needs to be extracted from the meat before it reaches the freezing point. It also has a larger surface area, which may affect the rate of heat transfer. Smaller meat boxes will freeze more quickly due to their lower mass and smaller surface area.