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2 years ago

How much thermal energy is needed to raise the temperature of 15kg gold from 45⁰ C up to 80⁰ C

Engineering

1 answer:

Levart [38]2 years ago

6 0

Answer:

68.25 kJ

Explanation:

The thermal energy Q required to raise the temperature of 15kg gold from 45⁰ C up to 80⁰ C is Q = mcΔθ where m = mass of gold = 15 kg, c = specific heat capacity of gold = 130 J/kg°C and Δθ = temperature change = θ₂ - θ₁ where θ₁ = 45 °C and θ₂ = 80 °C

So, Q = mcΔθ = mc(θ₂ - θ₁)

= 15 kg × 130 J/kg°C × (80 °C - 45 °C)

= 1950 J/°C × 35 °C

= 68,250 J

= 68.25 kJ

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Answer:

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3 years ago

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3 years ago

A composite wall is composed of 20 cm of concrete block with k = 0.5 W/m-K and 5 cm of foam insulation with k = 0.03 W/m-K. The

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Answer:

4.8°C

Explanation:

The rate of heat transfer through the wall is given by:

$q=\frac{Ak}{L}dT$

$\frac{q}{A}=\frac{k}{L}dT$

Assumptions:

1) the system is at equilibrium

2) the heat transfer from foam side to interface and interface to block side is equal. There is no heat retention at any point

3) the external surface of the wall (concrete block side) is large enough that all heat is dissipated and there is no increase in temperature of the air on that side

${k_{fi}= 0.03 W/m.K$

${L_{fi}= 5 cm = 0.05 m$

${T_{fi}= 25 \°C$

${k_{cb} = 0.5 W/m.K$

${L_{cb}= 20 cm = 0.20 m$

${T_{cb}= 0 \°C$

${T_{m}= ? \°C =$ temperature at the interface

Solving for ${T_{m}$ will give the temperature at the interface:

$\frac{q}{A}=\frac{k_{fi} }{L_{fi} }(T_{fi} -T_{m})=\frac{k_{cb} }{L_{cb} }(T_{m} -T_{cb})$

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3 years ago

assume a five layer network model. There are 700 bytes of application data. There is a 20 bye header at the transport layer, a 2

amm1812

Answer: The overhead percentage is 7.7%.

Explanation:

We call overhead, to all those bytes that are delivered to the physical layer, that don't carry real data.

We are told that we have 700 bytes of application data, so all the other bytes are simply overhead, i.e. , 58 bytes composed by the transport layer header, the network layer header, the 14 byte header at the data link layer and the 4 byte trailer at the data link layer.

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3 years ago

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