Heat transfer from composite pipe -- Is my answer right?

In summary, the conversation discusses a problem involving a water pipe insulated with fire glass lagging and surrounded by outside air. The heat loss per meter and over a 30 meter length of the pipe are calculated, as well as the interface temperature. The final temperature (t2) is determined to be 75.0797 degrees Celsius.
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Homework Statement
A water pipe of bore 65 mm bore and 6mm wall thickness, carrying water at 85ºC is
insulated with one layer of lagging. The lagging is made from fire glass which is 35 mm thick
and has a thermal conductivity of 0.04 W/m K. The outside air temperature is 10ºC and the
thermal conductivity of steel is 48 W/m K. Calculate the heat loss per metre length of pipe,
the total heat loss over a 30 m length of the pipe and the interface temperature (t2).
[Answers: 57.99 W/m: 1739.7 W: 84.9ºC].
Relevant Equations
Q = 2 x 3.142 x L (t1 – t3) / {[Ln (r2/r1)/k1] + [Ln (r3/r2)/k2]}


t2 – t3 = Q Ln (r3/r2) / k2 x 2 x 3.142 x L
Im practicing the questions in the problem book and seem to be getting different answers to the book can somebody check cheers.
[Answers: 57.99 W/m: 1739.7 W: 84.9ºC] textbook answers
A water pipe of bore 65 mm bore and 6mm wall thickness, carrying water at 85ºC is
insulated with one layer of lagging. The lagging is made from fire glass which is 35 mm thick
and has a thermal conductivity of 0.04 W/m K. The outside air temperature is 10ºC and the
thermal conductivity of steel is 48 W/m K. Calculate the heat loss per metre length of pipe,
the total heat loss over a 30 m length of the pipe and the interface temperature (t2).
  1. r1 = 65/2 = 32.5/1000 = 0.0325m
  2. r2 = 0.0325 + 0.006 = 0.0385m
  3. r3 = 0.385 + 0.035 = 0.0735m

Q = 2 x 3.142 x L (t1 – t3) / {[Ln (r2/r1)/k1] + [Ln (r3/r2)/k2]}

  1. Q = (2 x pi x 1 x (85-10)) / ((Ln (0.0385/0.0325))/48) + ((Ln(0.0735/0.0385))/0.04)
  2. Q = 471.239 / 0.00353 + 16.166
  3. Q = 471.239 / 16.170
  4. Q = 29.143
heat loss over whole pipe

t2 = (Q Ln (r3/r2) / k2 x 2 x 3.142 x L) + t3
  1. t2 = (29.143 x Ln (0.0735/0.0385)) / ( 0.04 x 2 x pi x 1 )
  2. t2 = 18.845 / 0.251
  3. t2 = 75.0797

  1. 29.143 x 30 = 874.29
Find temperature (t2)
 
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  • #2
I confirm your answer.
 

Related to Heat transfer from composite pipe -- Is my answer right?

1. What is heat transfer from composite pipe?

Heat transfer from composite pipe refers to the process of thermal energy being transferred from one medium (such as a fluid or gas) to another through a composite pipe made of multiple materials.

2. How does heat transfer occur in a composite pipe?

Heat transfer in a composite pipe occurs through conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between the materials, convection is the transfer of heat through the movement of fluids, and radiation is the transfer of heat through electromagnetic waves.

3. What factors affect heat transfer in a composite pipe?

The factors that affect heat transfer in a composite pipe include the thermal conductivity of the materials, the thickness of the pipe, the temperature difference between the two mediums, and the flow rate of the fluid or gas.

4. How can heat transfer from a composite pipe be calculated?

The rate of heat transfer from a composite pipe can be calculated using the heat transfer coefficient, which takes into account the thermal conductivity of the materials, the thickness of the pipe, and the temperature difference between the two mediums.

5. What are some applications of heat transfer from composite pipes?

Heat transfer from composite pipes is commonly used in industries such as oil and gas, chemical processing, and power generation. It is also used in household appliances such as refrigerators and air conditioners, as well as in heating and cooling systems for buildings.

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