Generally we say an engine has x number of flues (the big ones that the super heater units go in) and y number of tubes (the 2.0" or 2.25" ones). The K-36 have 30 5.5" flues and about 100 2.25" tubes. Note the number of tubes is from memory. I know the sizes are right and the number of flues is correct but number of tubes is a guess. If you ask any rabid railfan they can tell you the number, but those of us who work on them count them when we need to order them and other than that we let the number go.
Anyway hope this info helps
John Bush