HEAT TRANSMISSION

Please elaborate.

Ask your instructor for the composition of the gas. Or look up thermal conductivity of the pipe material.

Dear Guest. I take your message back here on the Forum, because other people might as well, or have their say too or want to get more knowledge about this post:

ELABORATION OF THE PROBLEM

QUESTION

[pTo: dvmdsc

Most engineers when are confronted with a problem involving the flow of heat, the average engineer will look up the formulas in his elementary physics text, and a table of thermal conductivities in a handbook, and considers that he has the complete data for solving the problem.

Just to clarify this point, in the published proceedings of a technical society some years ago it was stated that since copper had seven times the thermal conductivity of iron, substituting copper tubes for iron tubes in a piece of heat-transfer equipment should increase the capacity to seven times the original figure using iron.

This, of course, is not true. It is doubtful if the substitution would actually increase the capacity 10 percent.

What do you think?

ANSWER AS EXPLANATION

What you describe as heat transmission is only a part of the story. Heat transmission is the capability to "transmit" heat through the metal e.g. from point A to B. I should also refer to heat (or thermal)conductivity. This is different with each material and is a specific parameter and specification to it.

What you describe is IMO heat transfer. Through your metal - to a different medium - here as example water.

Many parameters will be determining your end result:

Some thoughts:

1. Heat source temperature and energy applied - in relation to the pipe surface. Is the source and pipe free to air - or is the process going on in a oven?

2. What is the time your process runs? Continuous, short intermittent? 3. How much is the flow of water in the pipe and what is the direction - with, or opposed to the heat flow spread?

As you can assume, not the material of the pipe will here be the main player, but your heat source and your consumed hot water. Pipe material and wall thickness will affect the heat- up and cool down hysteresis. The 7 doesn't count here, and the 10 %, depending on the application and the design, can make sense or may be not attainable at all. The design will show - elaboration needed.

Far too little information is given.

Apparently the fluid outside the pipe is intended to condense from a gas to a liquid.

If the notation is meant to be standard, h_g would be the enthalpy of the gas and h_f that of the liquid. If so, these numbers appear to be reversed.

→ Welty, Wicks & Wilson, "The Fundamentals of Heat, Mass and Momentum Transfer", any edition.

Por lo que veo, faltan especialistas en la materia o no han comprendido el problema!

Esperaba encontrar en este sitio lleno de humo, una respuesta, pero creo que andamos en el mismo nivel!

Hay que ponerse a estudiar!