Question

Какое количество каменного угля необходимо для нагревания от 10 до 50 градусов кирпичной печи массой 1,2 т ,если КПД печи 30%

Answer 1

Δt = 40° C
m = 1200 кг
КПД = 30 %
с (кирпича) = 880 Дж/(кг*C)
q (угля) = 29 300 000 Дж/кг

Qнагр. = c*m*Δt =  880 Дж/(кг*C) * 1200 кг * 40° C = 42240000 Дж

 0,3*Q (сгорания) = Qнагр
Q (сгорания) = 140800000 Дж
Q (сгорания) = q (угля) * m (угля)
m (угля) = Q (сгорания) / q (угля) = 140800000 Дж / 29 300 000 (Дж/к) = 4,8 кг

Answer 2

Calculating the Amount of Coal Needed to Heat a Brick Oven

To calculate the amount of coal needed to heat a brick oven from 10 to 50 degrees Celsius, we can use the formula:

Q = mcΔT

Where: - Q = heat energy required (in joules) - m = mass of the brick oven (in kilograms) - c = specific heat capacity of the brick oven material (in joules per kilogram per degree Celsius) - ΔT = change in temperature (in degrees Celsius)

Given: - Mass of the brick oven, m = 1.2 tons = 1200 kg - Change in temperature, ΔT = 50°C - 10°C = 40°C - Specific heat capacity of the brick oven material, c = 0.84 kJ/kg°C = 840 J/kg°C (specific heat capacity of brick)

Calculation Steps

1. Convert the mass of the brick oven from tons to kilograms: - 1 ton = 1000 kg - Therefore, 1.2 tons = 1200 kg

2. Calculate the heat energy required using the formula: - Q = mcΔT - Q = (mass) x (specific heat capacity) x (change in temperature)

Substituting the given values: - Q = (1200 kg) x (840 J/kg°C) x (40°C)

This will give us the amount of heat energy required to raise the temperature of the brick oven.

3. Calculate the amount of coal needed based on the efficiency of the oven: - Given that the efficiency of the oven is 30%, we can calculate the total energy needed and then divide by the efficiency to find the amount of coal needed.

Result

The amount of coal needed to heat the brick oven from 10 to 50 degrees Celsius can be calculated using the above steps.

Note: The specific heat capacity of the brick material is assumed to be 0.84 kJ/kg°C, which is equivalent to 840 J/kg°C.