Calculating Heat Transfer Rate and Length of Pipe

In summary, the problem involves saturated liquid water flowing at a rate of 2 kg/s in a metal pipe with a 5 cm inner diameter and 3 mm wall thickness. The pipe is exposed to ambient gas at 500 degrees C with a heat transfer coefficient of 100 W/m^2 K. The water is being boiled to saturated vapor at 500 kPa and the temperature is assumed to be uniform with no convective layer. The task is to find the total rate of heat transfer and the required length of the pipe. The relevant equation is the latent heat of vaporization. However, the method of calculation is not clear and further assistance is needed.
  • #1
ladydon2
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Homework Statement



Saturated liquid H2O @ 500 kPa flows in a metal pipe, 5 cm inner diameter and k=40 W/m K, with wall thickness 3 mm @ a rate of 2 kg/s. The pipe is exposed to ambient gas @ 500 degrees C with h=100 W / squared K. The water is being boiled to come out as saturated vapor @ 500 kPa. Assume the H2O temp is uniform and there is no inside convective layer. Find the total rate of heat transfer that must take place and the needed length of pipe.

Homework Equations





The Attempt at a Solution


 
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  • #2
I am not sure how to approach this problem. I know that the heat transfer has to be equal to the latent heat of vaporization, but I am not sure how to calculate it. Any help would be greatly appreciated.
 

1. How do you calculate heat transfer rate?

The heat transfer rate can be calculated using the formula Q = U*A*(T2-T1), where Q is the heat transfer rate, U is the overall heat transfer coefficient, A is the surface area, and T2 and T1 are the temperatures on either side of the surface.

2. What is the overall heat transfer coefficient?

The overall heat transfer coefficient (U) is a measure of the overall efficiency of heat transfer in a system. It takes into account the individual heat transfer coefficients of the materials and surfaces involved, as well as any resistances to heat transfer, such as fouling or fouling. It is typically expressed in units of W/m2K.

3. How do you calculate the length of a pipe for a given heat transfer rate?

The length of a pipe can be calculated using the formula L = (Q/U*A)*(T2-T1), where L is the length of the pipe, Q is the desired heat transfer rate, U is the overall heat transfer coefficient, A is the surface area, and T2 and T1 are the temperatures on either end of the pipe.

4. What factors affect the heat transfer rate in a pipe?

The heat transfer rate in a pipe is affected by various factors, including the temperature difference between the two ends of the pipe, the surface area of the pipe, the type of fluid flowing through the pipe, the flow rate of the fluid, and the material and thickness of the pipe walls.

5. How can I increase the heat transfer rate in a pipe?

To increase the heat transfer rate in a pipe, you can increase the temperature difference between the two ends of the pipe, increase the surface area of the pipe, increase the flow rate of the fluid, or use materials with higher heat transfer coefficients. Additionally, you can minimize any resistances to heat transfer, such as fouling or fouling, by regularly cleaning and maintaining the pipe and its surrounding environment.

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