Recent content by BradP

I'm looking at the dynamic state of heat transfer through a concrete slab. Suppose heat is turned on at t=0 and the coils/tubing are 6 inches below the surface. Is there a formula or way of calculating the temperature at the surface at time = t? I found a formula for thermal lag on wikipedia...

Two questions. I have read that wind chill is a measurement (or calculation, more accurately) that describes how cold the wind feels, even though the wind isn't actually colder than still air. What I am wondering is why isn't the wind actually colder? If it is moving faster it is lower pressure...

Well, that is a bit off-topic :) But both the company of my current job and my prospective job do the manufacturing. I am not too worried, as there are some things that just can't be outsourced effectively. Manufacturing is where the real value is -- not just holding a place in the line of...

I am early in my career working for a small niche company right now, doing a lot of mechanical design. It seems like great experience to me; I am learning a lot about machine parts, manufacturing processes, and drawings. However, I might have an opportunity to move into a large, well-connected...

Thanks for that thorough explanation. Essentially, what is throwing me off was whether the pressure was really zero at the duct outlet. It is going to have a significant velocity for some distance after exiting, so I was thinking it must have a different pressure than the stagnant air. Because...

I only know the pressure at one location: immediately after the fan. I just know that at some point further down the duct, it will be at some lower pressure. I don't know the exact location where it will reach 10 psi. I just know that it is pulled from a room where it is roughly stagnant and...

Yeah, if I knew flow rate velocity would be simple. I don't know it. All I will know is: - friction factor (using an estimated velocity) - initial pressure - duct length - duct diameter And it is assumed the air is room temperature. This is a determinate system. If you set up a pressure...

I don't remember why I said frictionless. I do want to account for friction, but I just don't care about a specific value right now. I will have one eventually, but right now I am just trying to get the concept straight. I was reviewing the Darcy-Weisbach, and I can enter everything into it...

Hm, okay. Appreciate it!

Suppose I have a straight, frictionless duct, with consistent cross-sectional area, and air is flowing straight through and exiting into a free stream. A fan at the beginning of the duct draws stagnant air at atmospheric pressure, and then the air exits the end of the duct into another room also...

Great points Euler. Thanks.

I have read that many tea masters insist that when infusing a tea that requires less-than-boiling water, you should first let the water reach a full 100 degrees C and let it cool back down to the target temperature, rather than take it off the burner as it is approaching boiling. I think it was...

Thanks everyone; I guess it is time to stop shooting myself in the foot. I am glad I asked.

Oh wow, I thought I was getting the same thing. I don't know how I overlooked the (1/2), sorry. Well, the point was that I formed a ring by subdividing the point mass, but that doesn't matter anymore.

I know. This is the formula I derived for a ring, not a disc. My question is why I ended up with the same formula as that of a disc. The derivation seems sound to me.