Family Stove Critical Dimensions and Calculations

Critical Dimensions

1. Top of combustion chamber (CC) to top of adobe or regular brick = 2 cm. With 1.3 cm Rebar, the distance from the top of the CC to the bottom of the pot, pan, or grille = 3.3 cm

2. The gap all around between the pot and the pot skirt (PS)

Calculations

1. Pot skirt

Diameter of pot in cm 20.0 22.0 24.0 26.0
Gap all around 2.2 2.0 1.8 1.6
Diameter of pot skirt (PS) 24.4 26.0 27.6 29.2
Circumference of pot skirt (PS) 76.0 81.0 87.0 92.0
Length of pot skirt (PS) 81.0 86.0 92.0 97.0

2. Flow calculations for a 24 cm pot, pan, or grille

Input flow A = w x h = 14 x 11.5 = 161 cm2

Output at flue pipe A = πr2 = 3.1428 x 25.8 = 81 cm2

This difference will be OK, because the area of the wood and ashes is not calculated and the stove works very well in practice.

Institutional Stove Critical Dimensions and Calculations for 40 cm Pot

Critical Dimensions

(Source: Design Principles for Wood Burning Cook Stove, Aprovecho Research Center page 14)

1. Top of combustion chamber (CC) to top of adobe or regular brick = 3.7 cm

2. Between the pot and the pot skirt the gap all around for a 40 cm diameter pot is 1.5 cm

Calculations

1. Pot skirt

Diameter of pot skirt = 40 + 1.5 + 1.5 = 43 cm

Circumference of pot skirt C = πD = 3.1428 x 43 = 135 cm

Add a 5 cm overlap for joining together and the sheet metal will be 140 cm long.

Therefore, make the cut 140 cm long at a width of say 13 cm. The sheet metal should be thin.

2. Flow calculations

Input flow A = w x h = 19.3 x 11.5 = 222 cm2

Output between pot skirt and 40 cm pot

Area of skirt = πr2 = 3.1428 x (43/2)2 = 1452 cm2
Area of pot   = πr2 = 3.1428 x (40/2)2 = 1257 cm2
                                       =  195

Thus inflow is greater than outflow by 222 – 195 = 27 cm2 which is OK, because no calculations are made for the area taken by the wood and coals.

If the stove is to be used indoors, then a flue pipe will need to be added and the pot skirt will need to be wider so it is above the top of the stove and crimped like the family stove. Also the pot skirt will need to be cut at the bottom where the hot gases exit to the flue pipe.