The concepts behind different heat transfer equations?

• Ciocolatta
In summary, the conversation discusses various equations used for heat transfer and their applications. The equations include Q = UA delta T for general heat transfer, Q = UA delta T (log mean temperature difference) for calculating the overall area required for a heat exchanger, Q = mC delta T for calculating sensible heat change, and Q = (latent heat of vaporisation) x mass/time for calculating heat consumed/released during phase change. These equations require a thorough understanding of thermodynamics and heat transfer and are commonly used in engineering applications.
Ciocolatta
Heya,

I'm a little confused about the heat equations and the difference in concepts and applications.

So there's:

Q = UA delta T <- I've used this for general heat transfer, like conduction through walls...

Q = UA delta T(log mean temperature difference) <- I've used that for calculating the overall area required for a heat exchanger, using log mean temp diff if i can assume rate of temperature change throughout is proportinoal and there's no phase change.

Q = mC delta T <- i already forgot what i use this for. its just like...how much energy i put in for sensible heat change right?

Q = (latent heat of vaporisation) x mass/time <- i used that to calc. the amount of heat consumed/released when fluid vaporises/condenses

how else can they be used for, how are they different and what other applications?
thanks!

Well, your question requires way more explanation than I think you realize. It's very hard to give you a concise and, more importantly, a complete answer. To be honest, to understand how to properly use the equations you posted, it takes a couple of classes in thermodynamics and heat transfer. If you've already had that, then maybe we can give you a refresher.

1) This equation isn't used for conduction, unless your U=k/delta_x. This would be more accurate for convection, if your U is the convection heat transfer coefficient.

2) You're right on that one.

3) It's accurate for heat transfer into solids, if c_p = c_v roughly.

4) You've got that one right.

As far as other applications, you can't really use them for something else other than heat transfer. However, those equations have kept engineers busy for a long time, so they're pretty good as they are.

1. What is heat transfer and why is it important?

Heat transfer is the movement of thermal energy from one object to another. It is important because it explains how heat flows and affects the temperature of different materials and systems, and is essential in many industrial processes and everyday life.

2. What are the different types of heat transfer?

The three main types of heat transfer are conduction, convection, and radiation. Conduction is the transfer of heat through direct contact, convection is the transfer through a fluid medium, and radiation is the transfer through electromagnetic waves.

3. What are the equations used to calculate heat transfer?

The equations used to calculate heat transfer depend on the type of heat transfer being considered. For conduction, the most commonly used equation is the Fourier's law of heat conduction; for convection, the Newton's law of cooling is often used; and for radiation, the Stefan-Boltzmann law is frequently used.

4. How do different materials affect heat transfer?

Different materials have different thermal conductivities, which affect how quickly heat can be transferred through them. Materials with high thermal conductivity, such as metals, allow heat to transfer more easily than materials with low thermal conductivity, such as wood or plastic.

5. What are some real-world applications of heat transfer equations?

Heat transfer equations are used in a variety of industries and applications, including designing and optimizing thermal systems like heat exchangers and refrigeration systems, understanding and predicting weather patterns, and developing insulation materials to improve energy efficiency.

Replies
14
Views
2K
Replies
7
Views
1K
Replies
1
Views
1K
Replies
2
Views
2K
Replies
15
Views
2K
Replies
28
Views
2K
Replies
8
Views
2K
Replies
5
Views
2K
Replies
5
Views
1K
Replies
5
Views
1K