We want to insulate a 25 cm radius 2 mm thick cast iron pipe with glass wool. Water at 80 C flows through the pipe at a linear velocity of 2 m/s. The outside temperature is 10 C.

a) Is the flow in the tube laminar or turbulent?

b) What will be the minimum insulation thickness (excel diagram)?

c) What will be the optimum insulation thickness if the pipe is 100 m long and a temperature drop of 5 C is allowed?

To gather data, use engineeringtoolbox.com and the data (prices) of any glass wool manufacturer. To find the energy cost for reheating water, look up current electricity or gas prices and calculate with an 80% efficiency. Calculate for a period of 1 year for subsection c). (Like this)

Optimum insulation thickness Economy requirement: The addition of insulation reduces heat loss and therefore saves money. However, the cost of insulation can be high. The optimal insulation thickness must be determined. For flat walls, any thickness of insulation will reduce heat loss! Optimum insulation thickness The total heat flux Q=RtotalT,1T,2 Rtotal=Rconv,1+R1+R2+Rconv,2Theconvectiveresistanceofmembers:Rconv,1=h1A11Rconv,2=h2A21 Optimum insulation thickness