# Heat up steel by resistance

1. Aug 9, 2006

### nurtas

Hi everyone,
Normally have a power generator of 200kW, 380V
I need to heat up the steel pipe by means of resistance, so that I will have inside temperature of the pipe 80C. The function of pipe is to transfer, heat the oil.
As a first step of this question, I have to calculate how much area can this power generator heat up.
If you have any idea, can you help me please,
Regards,
Nurtas

2. Aug 9, 2006

### FredGarvin

If you are heating oil in the pipe, the power requirement is going to depend heavily on the flow rate through the pipe. Look at the power required to heat the oil to a given $$\Delta$$T at a specific flow rate. You will then need to balance the velocity of the oil in the pipe and the residency time of the oil in the pipe. That will give you the length of pipe you will be using. Then you have to add the power required to heat that amount of pipe to that value to get your overall power requirement (in a perfect world).

3. Aug 9, 2006

### nurtas

ok

Ok, lets think that there is no oil, the only i have to calculate how much area I can heat with so much power.i think this will be the analogue of the electric oven.The problem is now i am not able to calculate the area, i know the pipe/material characteristics, I am just stuck on.

4. Aug 9, 2006

### Gokul43201

Staff Emeritus
Please describe the geometry (pipe dimensions and materials, location of current leads) and requirements (what length of pipe do you wish to heat) in more detail. The numbers for still air will turn out to be completely different from the numbers for flowing oil (huge difference in convective heat transfer coefficient).

Last edited: Aug 9, 2006
5. Aug 9, 2006

### nurtas

Material is carbon steel, OD:3.5 in, thickness:0.398 in, Specific heat:105 kCal/kg C, thermal conductivity:360,
generator is:200kW
I dont know the length, as you know length and resistance are directly proportional.

6. Aug 9, 2006

### FredGarvin

If you calculate the length/surface area of the pipe using 200 kW as the input power without taking into account the cooling effects of the flowing oil, you're going to be making your pipe too long and the power available will not be enough to get the pipe to the desired temperature.