Fourier's Law of Heat Conduction:
1. Heat flows through things more when they are hotter.
2. Heat flows more easily through materials that are hotter and thinner, or have better ability at letting heat through.
3. Heat doesn't flow through things as much when they are thicker or not good at letting heat through.
Answer:
.8215 MJ <- question is saying its hard for heat to go thru a thick brick wall <- thats why they are great to make homes with <- in winter brick homes stay warm!
Step-by-step explanation:
Heat Flow Calculation.
The brick wall (of thermal conductivity 0.32 W/m · ◦ C) of a building has dimensions of 2.7 m by 4 m and is 11 cm thick. How much heat flows through the wall in a 18.4 h period when the average inside and outside temperatures are, respectively, 11◦C and 7◦C? Answer in units of MJ.
To calculate the heat flow through the wall, we can use Fourier's law of heat conduction, which states that the heat flow through a material is proportional to the temperature difference across it and inversely proportional to its thickness and thermal conductivity:
Heat flow (Q) = (thermal conductivity) x (area) x (temperature difference) / (thickness)
Area = length x width = 2.7 m x 4 m = 10.8 m^2
Next, we need to calculate the temperature difference across the wall:
Temperature difference = inside temperature - outside temperature = 11◦C - 7◦C = 4◦C
Now we can calculate the heat flow through the wall:
Q = (0.32 W/m · ◦C) x (10.8 m^2) x (4◦C) / (0.11 m) = 125.45 W
To convert the heat flow to energy, we need to multiply by the time period:
Energy = Power x Time = 125.45 W x (18.4 h x 3600 s/h) = 821503.68 J
Finally, we convert Joules to MegaJoules:
Energy in MJ = 821503.68 J / 1,000,000 = 0.8215 MJ
Therefore, the heat flow through the wall over an 18.4 hour period is 0.8215 MJ.
The formula used to calculate the heat flow through a material is called Fourier's law of heat conduction. It is given by:
Heat flow (Q) = (thermal conductivity) x (area) x (temperature difference) / (thickness)
The formula used to convert power to energy is:
Energy = Power x Time
In this case, we used the unit of Watts for power and the unit of Joules for energy.
1. Insulation reduces heat flow: Insulation is a special material that helps stop heat from flowing through walls, ceilings, and floors.
2. Temperature difference: When it's colder outside than inside, heat tries to escape from the warm house to the cool outdoors.
3. Insulation slows down heat flow: But when a house is insulated well, the insulation slows down the heat flow, making it harder for heat to escape.
4. Factors affecting heat loss: The amount of heat lost from a house depends on things like the thickness of the walls, the type of insulation used, and the difference in temperature between inside and outside.
5. Using Fourier's law: Engineers and architects can use a special math formula called Fourier's law to figure out how much heat is likely to escape from a house under different conditions, and use that information to decide on the best insulation and building materials to use to save energy.
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