Calculate the total energy radiated from the sun to the earth each hour

6.1 × 10^20J

Analysis:

Find out the average power p of solar radiation and calculate the total energy of solar radiation per hour.

Look at the table and find out that the average power of solar radiation on the Earth's surface is 1.7 × 10 ^ 17 W, so the energy radiated by the sun to the Earth's surface per hour.

E=p·t=1.7×10^17W×3600s=6.1×10^20J

There are 40 kg of water in the solar water heater. Under sunlight, the water temperature increases by 25℃. . Find: (1) The heat absorbed by the water; (2) These heat quantities

Calculation of heat absorption by solar water heaters

Heat absorption area: 0.058*1.8=0.1044 . square meters

Volume of water: 200 liters = 200 kg = 200 kg (calculated based on water density: 1.0*1000kg/m?)

Heat absorption power: 2500 watts, then the heat absorbed in one second is: 2500/1000*860/3600 (kcal) = 0.597 kcal (1 kWh = 860 kcal) (Note: the power input here should refer to the total power input of a water heater with a capacity of 200 kg)

So 200 kilograms of water in 4 The total heat absorbed in one hour is: 0.597*4*3600=8596.8 kcal

The total heat absorbed after taking into account, the efficiency of the water heater is: 8596 .8*0.6=5158 kcal=21595.8 kilojoules (1 Kcal = 4.1868 kilojoules)

Specific heat of water: 4186.8J/kg.℃=4.1868kJ/kg .℃

The temperature rise of the water heater is: 21595.8 kilojoules/4.1868 (kJ/kg.℃)/200kg=25.79℃

If heat dissipation loss is not considered, the water in the water tank will theoretically reach 45.79℃ after 4 hours. However, there is actually a loss of heat dissipation, the main reason is that there is a difference between the ambient temperature and the water tank surface temperature (affected by the water temperature in the rtank). water tank), there is therefore a heat loss by radiation and convection, which can be calculated theoretically, which requires computer programming, because the water temperature (and therefore the surface temperature of the water tank water) and ambient temperature are different. constantly changing, so heat loss is also constantly changing. Therefore, after calculating the heat loss, the actual water temperature will be lower than 45.79°C.

Actually, the calculation above assumes that the heat absorption power you indicate is the total theoretical heat absorption power of the water heater, therefore the efficiency of the water heater is taken into account.