Exit Temp / Heat Loss in External Pipework

In summary, the conversation discusses the attempt to determine the heat loss and exit temperature for 100ml of water traveling down a pipe located externally to a building, exposed to -10degC air temperatures. The pipe has an internal diameter of 19mm and a length of 3m, with the water traveling at a rate of approximately 0.5m/s. The water is being released from a siphon and the flow rate is approximately 14.3ml/s. Both conduction and convection heat losses are occurring, with uncertainty about which is greater. The properties of water at 20degC are provided for calculations, and a formula is mentioned for convection calculations. The problem has since been solved and the thread
  • #1
sam...wise
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I have been trying to establish what the heat loss and exit temp (in deg C) for 100ml of water traveling down a pipe located externally to a building and subjected to -10degC air temperatures will be if:

The pipe has an internal diameter of 19mm and a length of 3m.
100ml of water with initial temp of 20degC is traveling in the pipe at approximately 0.5m/s. (The pipe is not full of water).
The 100ml water is being released from a siphon, which takes approximately 7seconds. Flow rate = approx. 14.3ml/s.
Assuming material is temp of external air and thickness is negligible.

Both conduction and convection heat losses will be occurring, but I am not sure which is the greater.

Using, the below for water at 20degC:
density = 998kg/m^3
thermal conductivity = 0.598 W/m.degC
Dynamic viscosity = 1.002 kg/m.s
Kinematic viscosity = 1.004 x10-6
Cp = 4182 J/kg.degC
Pr = 7.01

For convection calcs I have been trying to use Texit = (Tsurface - Tin)e^-(h.A/mdot.Cp) but I could do with clarification of my results, as I am not sure they are correct.

Thank you for any assistance. Please let me know if additional information is required.
 
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  • #2
I have solved this problem. This thread can be deleted.
 

1. What is "Exit Temp / Heat Loss in External Pipework"?

"Exit Temp / Heat Loss in External Pipework" refers to the temperature of a fluid (such as water or steam) as it exits a pipe and the amount of heat that is lost from the fluid as it travels through external pipes.

2. Why is it important to measure exit temperature and heat loss in external pipework?

Measuring exit temperature and heat loss in external pipework is important because it can help determine the efficiency of a system, identify any potential issues or inefficiencies, and inform decisions on how to improve the system's performance.

3. How is exit temperature and heat loss calculated?

Exit temperature and heat loss can be calculated using a variety of methods, such as mathematical equations or thermal imaging. The specific calculation method will depend on the type of fluid, the properties of the pipe, and the environmental conditions.

4. What factors can affect exit temperature and heat loss in external pipework?

There are several factors that can affect exit temperature and heat loss in external pipework, including the type of fluid, the flow rate, the material and insulation of the pipe, the ambient temperature and humidity, and any external forces (such as wind or sun exposure).

5. How can exit temperature and heat loss be minimized in external pipework?

To minimize exit temperature and heat loss in external pipework, proper insulation and maintenance of the pipes is crucial. Additionally, controlling the flow rate of the fluid, using more efficient materials for the pipes, and reducing external forces can also help decrease heat loss.

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