Question

Чавун массою 20 т нагріли в печі від 20 °С до 1200 ⁰С. обчисліт масу камяного вугілля яке для цього преба спожити?

Answer 1

Дано:
m1=20*10^3 кг
t1=20
t2=1200
Знайти
m2-?

Q1=q*m2;
Q2=c*m1*(t2-t1);
Q1=Q2;
q*m2=c*m1*1180

q=20900кДЖ/кг
с=0.5кДЖ/кг*К
20900m2=0.5*20000*1180
m2=(10000*1180)/20900
m2=564.6кг

Answer 2

Calculation of the Mass of Coal Required to Heat 20 t of Cast Iron

To calculate the mass of coal required to heat 20 t (tonnes) of cast iron from 20°C to 1200°C, we need to consider the specific heat capacity of cast iron and the heat of combustion of coal.

The specific heat capacity of cast iron is approximately 0.46 J/g°C This means that it takes 0.46 Joules of energy to raise the temperature of 1 gram of cast iron by 1 degree Celsius.

To calculate the amount of heat energy required to raise the temperature of 20 t of cast iron from 20°C to 1200°C, we can use the formula:

Q = m * c * ΔT

Where: - Q is the heat energy - m is the mass of the cast iron - c is the specific heat capacity of cast iron - ΔT is the change in temperature

Let's calculate the heat energy required:

Q = 20,000 kg * 0.46 J/g°C * (1200°C - 20°C)

Q = 20,000,000 g * 0.46 J/g°C * 1180°C

Q = 10,960,000,000 J

Now, we need to calculate the heat of combustion of coal. The heat of combustion is the amount of heat energy released when a substance is burned. The heat of combustion of coal can vary depending on the type of coal, but for this calculation, we will assume an average value of 24 MJ/kg (megajoules per kilogram).

To calculate the mass of coal required, we can use the formula:

Q = m * H

Where: - Q is the heat energy required (10,960,000,000 J) - m is the mass of coal - H is the heat of combustion of coal (24 MJ/kg)

Let's calculate the mass of coal required:

10,960,000,000 J = m * 24,000,000 J/kg

m = 10,960,000,000 J / 24,000,000 J/kg

m = 456.67 kg

Therefore, approximately 456.67 kg of coal would be required to heat 20 t of cast iron from 20°C to 1200°C.

Please note that this calculation assumes ideal conditions and does not take into account any losses or inefficiencies in the heating process.