# Heat Loss of Hot Air: Get the Facts on Temperature & Insulation

• RayJalaly
In summary, the person is seeking help with a project involving transferring hot air from a chimney stack to a holding tank using a 35-meter stainless steel pipe with 3mm wall thickness. They are wondering about the temperature of the air after traveling through the pipe, which will be insulated for most of its length but exposed to outside temperatures at some points. They are also requesting additional information such as the thickness and conductivity of the lagging and the flow rate of the air.

#### RayJalaly

Hi everyone

I'm new around here and I wonder if anyone can help please. I'm taking hot air off the chimney stack inside a factory at a temperature ranging between 700 and 400 degrees going through a 4 inch stainless steel pipe with 3mm wall thickness. This pipe line will be about 35 meters long in total carrying the hot air to a holding tank in order to keep it warm. I like to know what the temperature of the air would be once its traveled about 35 meters of pipeline totally lagged. About 10 meters of the pipe line will be outside but will be insulated. If we assume the temperatures outside could get as low as say -5 degrees in the winter in the worst case scenario, I'd like to know what the air temperature inside the pipe would be once its delivered to the tank outside if the input temperature at source ranges between 400 and 700 degrees. I'd like to thank anyone who can help in advance. Cheers

RayJalaly said:
totally lagged
Need to know the thickness and conductivity of the lagging.

CWatters
...and flow rate of the air. Also, a sketch would help visualize this.

If the entire run is insulated, then it is an easy problem because you don't have to try tackling the convective heat loss.

## 1. What is heat loss and why does it occur?

Heat loss is the transfer of thermal energy from a hotter object to a cooler one. It occurs because heat naturally moves from areas of higher temperature to areas of lower temperature in an attempt to reach equilibrium.

## 2. How does hot air lose heat and why is it important to understand?

Hot air loses heat through convection, conduction, and radiation. Convection is the transfer of heat through the movement of air or liquid, while conduction is the transfer of heat through direct contact. Radiation is the transfer of heat through electromagnetic waves. It is important to understand how hot air loses heat because it affects the efficiency of heating systems and can impact energy costs.

## 3. Can insulation prevent heat loss in hot air?

Yes, insulation can prevent heat loss in hot air. Insulation acts as a barrier to slow the transfer of heat, keeping hot air inside and preventing it from losing its heat to the colder environment. This can help maintain a comfortable temperature and reduce energy usage.

## 4. How does temperature affect heat loss in hot air?

The difference in temperature between the hot air and the surrounding environment plays a significant role in heat loss. The greater the difference in temperature, the faster heat will be lost. For example, if the outside temperature is much colder than the temperature inside a room, heat loss will occur more quickly.

## 5. What are some common ways to reduce heat loss in hot air?

Some common ways to reduce heat loss in hot air include using insulation, sealing any air leaks, and using energy-efficient windows and doors. Other measures such as maintaining a consistent temperature and using a programmable thermostat can also help reduce heat loss and save energy.