Chapter 1
Three mechanisms by which heat is transferred
Heat moves from areas of higher temperature to areas of lower temperature. This movement can be broadly categorized into conduction, convection, and radiation.
Respect
Transmission
This is a phenomenon in which heat is transferred within an object or between objects in contact.
For example, this phenomenon occurs when heat is transferred from the inside of a heated furnace through the walls to the outside.
Convection
Convection
This is a phenomenon in which heat is transported by the flow of air, liquid, or other fluids.
When high-temperature air flows out from an opening, heat is transferred along with the fluid.
Radiation
Radiation
This is a phenomenon in which heat is transferred by electromagnetic waves emitted from an object.
This relates to situations such as when heat is transferred from high-temperature furnace walls or products to the surrounding area.
In actual equipment, it's not always the case that only one of conduction, convection, or radiation is occurring; multiple heat transfer mechanisms are happening simultaneously.
Chapter 2
"Heat escape routes" that are often overlooked in factories
It's relatively easy to imagine that heat escapes through the furnace door and large openings.
However, when considering heat loss in a factory, it's not enough to only look at the most obvious areas.
| Place to check | Possible heat transfer | Things I want to confirm |
|---|---|---|
| Furnace and equipment surface | Conduction and radiation | Are there any areas that are hotter than the surrounding area? |
| Doors and openings | Convection and radiation | Check the outflow of hot air and the duration of opening. |
| Piping | Conduction, convection, and radiation | Check the insulation condition and surface temperature. |
| Valve flange | Conduction and radiation | Check the temperature difference and insulation condition with surrounding pipes. |
| Equipment connection part | Conduction and convection | Check for any areas with locally high temperatures or any gaps. |
Just because something is insulated doesn't mean it's safe.
Even if insulation is used in equipment and piping, surface temperatures may vary depending on the construction conditions, aging, and the shape of the equipment.
The important thing is not to judge solely based on whether or not there is insulation, but to check the actual temperature conditions.
Chapter 3
Uneven temperature distribution is another point you don't want to overlook.
When we talk about heat loss, we tend to only imagine the heat escaping from the equipment to the outside.
However, the temperature distribution inside the furnace and equipment is also an important point to check.
The set temperature and the temperature in all locations may not be the same.
Inside the furnace, temperature differences may occur in different areas due to factors such as the heater's position, airflow, product placement, and door opening/closing.
Therefore, looking at only one measurement point may not provide a complete picture of the overall condition inside the furnace.
Temperature variations should be considered from both a quality and energy perspective.
If there are variations in temperature distribution, a margin may be added to the operating conditions to avoid affecting product quality.
Therefore, by understanding the temperature distribution and comparing the required conditions with the actual state, it becomes easier to consider whether there are any areas that can be improved while maintaining quality.
If the furnace temperature is unstable, it is necessary to check multiple factors, including not only the heater but also sensors, control, load, and airflow.
Chapter 4
How to detect invisible heat loss
Heat cannot be seen directly with the naked eye.
Therefore, starting with the feeling of unease we experienced on-site, we check the condition by measuring the temperature.
Step 1
notice
We gather observations from the field, such as "It's only hot in this area" or "The area around the equipment is hotter than before."
Step 2
Measure
We use temperature sensors, radiation thermometer, thermal imaging cameras, etc., to check the temperature state.
Step 3
compare
We will compare differences based on location, changes over time, and differences before and after improvement.
Step 4
Prioritize
Based on the data obtained, we will organize where to begin considering improvements.
Use both point temperature and surface temperature to differentiate between them.
The appropriate measurement method differs depending on whether you want to continuously measure a specific location or check the temperature distribution over a wide area.
Measure the temperature
Confirm without contact.
Next episode
If heat loss is observed, should I simply lower the temperature?
Understanding the thermal state might inspire you to change the conditions to save energy.
However, in a manufacturing setting, you cannot make a judgment based solely on energy consumption.
There is another important condition: product quality.
In episode 4, we will explore the theme of "the balance between quality and energy saving," considering the role that temperature measurement plays in reducing waste while maintaining quality.
Read Chapter 4: "The Balance Between Quality and Energy Saving"
Series
Factory decarbonization series
Episodes 1 to 3
- Episode 1: Why is decarbonizing factories not a simple task?
- Episode 2: The True Nature of Intuition and Experience
- Episode 3: Where does the heat escape from?
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Continue reading the series
In Episode 2, we explored the meaning of combining "intuition and experience" with data. In Episode 4, we will move on to how to utilize that data to achieve both quality and energy efficiency.
