Cross Flow Heat Transfer

[StevenKingdon]

Hello, I am new to the forum (and engineering)

I'm completing a work term for university, and my mentor suggested a report topic that involves cross flow heat transfer. The only problem is that I have not taken the course yet, so I am trying to learn it all myself with no luck.

My question is how much heat is lost in a 0.1016 m (4") Carbon Steel Pipe (wall thickness 0.006 m or 0.237") carrying water at 80°C (176°F). The outside temperature is -2.37°C (27.7°F) with a wind speed of 5 m/s (16.4ft/s).

I am trying to determine how much input would be required from a furnace to increase the heat if the pipe had insulation stripped, while relating length of pipe stripped to loss in heating therefore increased cost. These are the values I was using.

----------------------------Water @ 80°C------------Carbon Steel-----------Calcium Silicate------------------Air @ -2.31
Density---------------------9.7121E+2 kg/m^3----------------------------------------------------------------1.3043 kg/m^3
Dynamic Viscosity-----------3.4599E-4 kg/ms-----------------------------------------------------------------1.7116E-5 kg/ms
Kinematic Viscosity---------3.5625E-7 m^2/s-----------------------------------------------------------------1.3123E-5 m^2/s
Specific Heat---------------4.0696E+3 J/kgK-----------------------------------------------------------------1.0055E+3 J/kgK
Conductivity----------------0.67 W/mK------------------54 W/mK-----------------0.063 W/mK-------------------0.023895 W/mK
Prandtl Number--------------2.1015--------------------------------------------------------------------------0.72029

I have found the heat content of No.1 Furnace oil to be 134000 BTU/gallon.

I have used the formula q=2πkL(T1-T2)/ln⁡(r_2/r_1 ) , and recieved an answer of q = 237,106*L and this would give me my W/m. But I'm not sure if this is remotely correct as is doesn't take into consideration wind.

Sorry for being long winded, I'm just all out of options.

 

[georgeverghese]

We normally dont assist with student postings, but your answer may well be within 10% of the estimate obtained with a great deal more work - this is because the insulation resistance to heat transfer may well be more than 90% of the total heat transfer resistance. Heat content for fuel oil sounds about right, and so does your formual for heat transfer across an insulation layer.

 

[StevenKingdon]

I worked it out and found an answer that my supervisor and I are satisfied with which includes losses due to cross flow.