Heat transfer from a fluid to a solid

[avery64]

I need a hand understanding the behaviour of a system which follows:

Hot combustion gases emerge from an aperture at a fixed temperature and pressure and pass through a length of tube.
How does the diameter of the aperture and tube, plugged into bernoulli's principle, turbulence of the gas, surface area of the inside of the tube, length of tube, heat capacity and conductivity all effect how much heat is transferred to it.

Heat in the combustion gases are to be considered lost if they emerge from the end of the tube, and only useful if the heat radiates from the surface of the tube according to Stefan's law (emissivity constant 0.8 let's say), and that being a real world situation, the tube has to fit into a fixed volume, and that too much resistance to flow would probably not be good for the heat source ... what is the best configuration for the tube?

 

[Aaron Barnard]

The diameter of the aperture will affect the rate of flow and the pressure of the gases as they emerge. This, in turn, affects the turbulence of the gases and their ability to transfer heat to the tube. The surface area of the inside of the tube is a key factor in determining how much heat is transferred as it directly affects the amount of contact between the hot gases and the tube. The length of the tube also affects how much heat is transferred as it determines how long the gases remain in contact with the tube. The heat capacity and conductivity of the tube material determine the rate at which heat is transferred from the hot gases to the tube.

In order to optimize the heat transfer from the combustion gases to the tube, the diameter of the aperture should be chosen so that the pressure of the gases is such that the flow is turbulent, but not too turbulent as to cause excessive resistance to flow. The surface area of the inside of the tube should be maximized to ensure maximum contact between the gases and the tube, while the length of the tube should be chosen to ensure sufficient time for the heat transfer to take place. Finally, the heat capacity and conductivity of the tube material should be chosen to maximize the rate of heat transfer from the gases to the tube.

 

[astrokreng]

I would approach this problem by first understanding the fundamental principles of heat transfer and fluid dynamics. Heat transfer from a fluid to a solid occurs through convection, conduction, and radiation. In this scenario, convection is the main mechanism of heat transfer, as the hot combustion gases are in direct contact with the tube.

The diameter of the aperture and tube will affect the velocity and pressure of the gases passing through, which in turn will affect the convective heat transfer coefficient. According to Bernoulli's principle, as the diameter of the aperture decreases, the velocity of the gases will increase, resulting in higher convective heat transfer. However, too small of an aperture may create too much resistance to flow, which could negatively impact the heat source. Similarly, the diameter of the tube will also affect the convective heat transfer, as a smaller diameter will increase the velocity of the gases passing through.

The turbulence of the gas will also play a role in heat transfer. Turbulent flow is known to have a higher convective heat transfer coefficient compared to laminar flow. Therefore, a design that promotes turbulent flow, such as using vanes or fins in the tube, may increase heat transfer.

The surface area of the inside of the tube will also impact heat transfer. A larger surface area will increase heat transfer, as there will be more area for the hot gases to come into contact with the tube. This can be achieved by increasing the length of the tube or by using a tube with internal fins or roughness.

The heat capacity and conductivity of the tube material are also important factors to consider. A material with a high heat capacity will be able to absorb more heat from the gases, while a material with high heat conductivity will be able to transfer the heat more efficiently. Choosing a tube material with these properties will optimize heat transfer.

Finally, the configuration of the tube will also play a role in heat transfer. In this scenario, the goal is to maximize heat transfer through radiation, which is dependent on the surface area and emissivity of the tube. A tube with a larger surface area and higher emissivity will radiate more heat, resulting in higher overall heat transfer.

In conclusion, the best configuration for the tube will depend on various factors such as the diameter of the aperture and tube, turbulence of the gas, surface area of the inside of the tube, length of the tube, heat capacity and conductivity of the tube material, and the desired method of heat transfer