How much dry wood is required to heat 166 kg of water from 15 degrees to a boil, if the efficiency

How much dry wood is required to heat 166 kg of water from 15 degrees to a boil, if the efficiency of the stove is 50 percent. specific heat of combustion of firewood 8.3 per 10 in 6 J / kg.

Data: m1 (mass of water) = 166 kg; t0 (initial water temperature) = 15 ºС; η (efficiency of the furnace with which the water was heated) = 50% (0.5).

Constants: Sv (specific heat capacity of water) = 4200 J / (kg * ºС); tboil (boiling point) = 100 ºС; according to the condition q (specific heat of combustion of dry wood) = 8.3 * 10 ^ 6 J / kg.

The required amount of dry firewood is determined from the formula: η = Sv * m1 * (tboil – t0) / (q * m2); m2 = Sv * m1 * (tboil – t0) / (η * q).

Calculation: m2 = 4200 * 166 * (100 – 15) / (0.5 * 8.3 * 10 ^ 6) = 14.28 kg.