How to Calculate Heat Loss in a Hot Water Pipe?

In summary: The simple mean will do.In summary, a thick wall cylinder with a thermal conductivity of 60W/mK, 75mm inner diameter, and 2.5mm thickness carries water at 90 degrees celsius inside and is surrounded by air at 20 degrees celsius on the outside. With heat transfer coefficients of 500W m2 K and 35 W m2 K on the inside and outside respectively, the heat loss in W per unit length of the pipe can be calculated using q= K Delta U T1-T2/r1-r2 = T1-T2/r2-r/Kal. However, the calculations provided seem to have omitted the heat transfer resistance on both sides and may need to be revised.
  • #1
DerekWeir29
2
0

Homework Statement


A thick wall cylinder having a thermal conductivity of 60W/mK has a 75mm inner diameter and is 2.5mm thick. The pipe carries water at 90 degrees celsius inside and the outside is surrounded by air at 20 degrees celsius.

The heat transfer coefficients inside and outside the hot water pipe are 500W m2 K and 35 W m2 K respectively. Natural convection can be ignored.

Calculate the heat loss in W per unit length of the pipe

Homework Equations



q= K Delta U T1-T2/r1-r2 = T1-T2/r2-r/Kal

Alm = 2Pie Lr2- 2Pie Lr1/Ln(2(2{PieLr2/2pieLr1 [/B]

= A2-A1/ln(A2/A1)

The Attempt at a Solution



q = 90-20/0.03875-0.037
60 * (2Pie x 1 x 0.03875- 2Pie x 1 x 0.03875)/
ln (2Pie x 1 x0.3875/2Pie x 1 x0.3875/2Pie x 0.3875
 
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  • #2
Your equations are unreadable. Please use the symbols provided with the ∑ sign on the tool bar, or use Latex. There is a LaTex tutorial available on our sight.

Regarding your calculations, you seem to have omitted the heat transfer resistance on the air side and on the fluid side, which are in series with the pipe wall. Also, for such a thin wall, there is no need to use the log-mean.
 

Related to How to Calculate Heat Loss in a Hot Water Pipe?

What is heat transfer?

Heat transfer is the movement of thermal energy from one object or system to another due to a difference in temperature. It can occur through three main processes: conduction, convection, and radiation.

What is the difference between conduction, convection, and radiation?

Conduction is the transfer of heat through direct contact between two objects or substances. Convection is the transfer of heat through the movement of fluids or gases. Radiation is the transfer of heat through electromagnetic waves without the need for a medium.

How does heat transfer affect the temperature of an object?

Heat transfer can cause an object to increase or decrease in temperature, depending on the direction of the heat flow. If heat is transferred from a warmer object to a cooler object, the cooler object will increase in temperature. If heat is transferred from a cooler object to a warmer object, the warmer object will decrease in temperature.

What factors affect the rate of heat transfer?

The rate of heat transfer is affected by several factors, including the temperature difference between the objects, the thermal conductivity of the materials involved, the surface area of contact, and the distance between the objects.

How is heat transfer used in everyday life?

Heat transfer is used in many everyday applications, such as cooking, heating and cooling systems, and transportation. It is also important in industries like manufacturing and power generation, where controlling heat transfer is crucial for efficiency and safety.

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