Chimney (Stack) Data

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Does this help:

CHOOSING THE SIZE OF THE STACK

Stack draft

This is the possibility the fumes stack has of eliminating all the combustion products of a boiler without forming counter pressures. Remember the stacks must be:

• completely airtight with smooth internal surfaces.

• appropriately insulated to avoid fumes cooling too much.

• the connection between the boiler and the stack must be as short as possible, avoiding bends and long horizontal sections.

T = draft of the stack in mm column of water

h = working height of stack (net of bends and sub horizontal sections)

s.a.w. = specific air weight

s.f.w. = specific fumes weight corresponds to the average temperature taken inside the stack.

T = h x (p.s.a - p.s.f.)

Specific weight of air s.a.w. (at a pressure of 760 mmHg)

Air temperature -5 0 5 10 15 20 25 30

°C

p.s.a. (Kg/m3) 1,317 1,293 1,27 1,247 1,226 1,205 1,185 1,165

Specific weight of fumes (at a pressure of 760 mmHg)

Exhaust gas 160 180 200 220 240 260 280 300

temperature °C

p.s.f. (Kg/m3) 0,848 0,81 0,776 0,774 0,715 0,688 0,664 0,64

Example: external temperature: 5°C;

fumes temperature: 180 °C;

working height of stack: 10 m

T = 10 x (1.27 – 0.81) = 10 x 0.46 = 4.6 mm