Heat Transfer of a Plate in Air

In summary, the conversation is about setting up a system to heat a rectangular plate using heater cartridges and free convection air. The purpose is to melt plastic at regular intervals and control the system using Simulink. The person is having trouble linking equations together and is looking for a way to calculate the temperature drop when the plate comes in contact with the plastic, as well as the time it takes for the temperature to increase again. They compare it to a fridge where an object's temperature affects the interior temperature. They are asking for help in finding the equations needed to model this system in Simulink.
  • #1
rjsfocus
2
0
I am setting up a system where a rectangular plate is heated by a set of heater cartridges, producing about 4000 watts. This plate is in free convection air. It is used to melt plastic at regular invervals. I am trying to model the system so we can estimate temperatures of the plate to control the system better, by using Simulink. I am having trouble linking several equations together though. I can figure out the temperature and time it takes to reach the temperature, in a vacuum at least, through Q=CM(Tf-Ti), and q=Q/t. The heaters are heated like a convection oven, electricity is either supplied or stopped, based on the temperature of the plate.
What I am looking to do is find the temperature of the plate during a cycle, such as when temperature is roughly steady state, but is then decreased when energy is transferred to the plastic, and to air as well if I can. Does anyone have any idea how to calculate the temperature drop when it hits the plastic, and then how long it takes for the temperature to increase? I feel it is similar to say a fridge, it runs at a constant temperature until an item is put into it. The temperature drops and then rebounds.
Thanks for any help that can be provided.
Rich
 
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  • #2
If you put an object in a refrigerator and the object is hotter than the interior of the fridge, then heat will transfer from the object to the interior of the fridge and raise the temperature. Once the increased temperature goes past the thermostat set point, then the refrigeration unit starts to remove the excess heat from the interior until the temperature drops below the thermostat set point. If the object is colder, there is no excess heat to remove.
 
  • #3
Is there a way to calculate both temperatures? I plan on modeling in Simulink but I really don't know what equations to start with.
 

FAQ: Heat Transfer of a Plate in Air

1. What is heat transfer and how does it occur in a plate in air?

Heat transfer refers to the movement of thermal energy from a hotter object to a cooler object. In the case of a plate in air, heat transfer occurs through convection, where the air surrounding the plate is heated and rises, while cooler air moves in to take its place, creating a continuous cycle of heat transfer.

2. How does the material of the plate affect heat transfer?

The material of the plate can greatly affect heat transfer. Materials with high thermal conductivity, such as metals, allow for faster heat transfer compared to materials with lower thermal conductivity, such as plastics. This is because materials with higher thermal conductivity can transfer heat more easily.

3. What factors affect the rate of heat transfer in a plate in air?

The rate of heat transfer in a plate in air is affected by several factors, including the temperature difference between the plate and the surrounding air, the surface area of the plate, the material of the plate, and the movement of the air (wind speed) over the plate.

4. How does the shape and size of the plate affect heat transfer?

The shape and size of the plate can affect heat transfer in several ways. A larger surface area allows for more heat to be transferred, while a smaller surface area will result in slower heat transfer. The shape of the plate can also impact heat transfer, as different shapes have different surface areas and can affect the movement of air around the plate.

5. What are some practical applications of understanding heat transfer in a plate in air?

Understanding heat transfer in a plate in air is important in various industries, such as HVAC (heating, ventilation, and air conditioning) systems, where heat transfer is used to regulate the temperature of a space. It is also relevant in the design of cooking and refrigeration systems, as well as in the study of meteorology and weather patterns.

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