How to find the heating calculations for degester system

[aniruddin]

I am looking at sizing a heat exchanger for the heating requirements for an anaerobic Digester.
The digester is a concrete tank with balloon roof. The set point temperature is 36 deg C.
The inside wall diameter is 28m with a sidewalk height of approx 9m. wall thickness is 0.7m.
The volume of sludge is 7000m3 and is 8-12% dry solids content.The slurry inside the digester is pressmud.
The pipe winding is placed inside the digester tank and the clearance between the digester wall and pipe is 20cm. Outer diameter is 60.3mm and pipe thickness is 2.77mm.
I want to know the length of pipe we need to consider and input temperature of the steam water which comes to this pipe, what are the calculations I must consider?

I believe these are the three I must calculate:

1) to heat the raw sludge feed from 5 deg C to 36 deg C
2) to calculate the heat loss from the digester
3) to calculate the input temperature of stream water need to pass through the pipes(SS304)

I would be grateful if anyone can provide any typical calculation examples / website links that I could base the design on.

Regards
Aniruddin