题目
题目

SPHY001 Practice Quiz - Unit 14 | LA054

单项选择题

A window conducts power P from a house to the cold outdoors. What power is conducted through a window of half the area and half the thickness?

选项
A.P/4
B.4P
C.P/2
D.P
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标准答案
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思路分析
Consider the relation for conductive power: P = k A ΔT / L, where k is the thermal conductivity, A is the area, ΔT is the temperature difference, and L is the thickness. Option 1: P/4. This would happen if the area were halved and the thickness remained......Login to view full explanation

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类似问题

Question text1. The one-dimensional heat flow equation is: [math: ρCP∂T∂t=κ∂2T∂z2+A] where ρ, Cp, and κ are the density, specific heat and thermal conductivity, and A represents heat sinks and sources. The boundary conditions in a given system are: (i) T=320 K at z=0 (ii) T=1200 K at z=40 km and we also have [math: κ=3Wm−1K−1]. Assuming no internal heat sources, calculate a) The thermal gradient of the equilibrium geotherm in [math: K/km] to two significant figures.Thermal gradient = Answer 1 Question 3[input] [math: K/km] [6] b) The temperature at a depth of 100km as predicted by this geotherm model. Give answer in K to two significant figures. T(z=100 km) = Answer 2 Question 3[input] K [4]

Question text1. The one-dimensional heat conduction equation for a cooling dyke with no internal heating can be written: [math: ∂T∂t=κ∂2T∂x2]Where [math: T] is temperature, [math: t] is time, [math: x] is horizontal distance, and [math: κ] is the thermal diffusivity, and has a solution of the form: [math: T(x,t)=T02[erf(w−x2(κt))+erf(w+x2(κt))]] At t=0, T=T0 for –[math: w] < x < [math: w], and at t=0, T=0 for |x| > [math: w]. If the half-width of the dyke is [math: w=2.7m], centred on x = 0, and if T0 = 1500 oC and [math: κ] = 10-6 m2s-1 a) calculate the temperature at the centre of the dyke after one week and after one year (365 days) in degrees Celsius to three significant figures. HINT: Use a calculator, an online tool or MATLAB to calculate the error function (in MATLAB simply use erf(your value) ). After one week: [math: T=] Answer 1 Question 1[input] degrees Celsius [3]After one year: [math: T=] Answer 2 Question 1[input] degrees Celsius [3]b) Calculate the temperature of the dyke at the edges after 1 year in degrees Celsius to three significant figures.[math: T=] Answer 3 Question 1[input] degrees Celsius [4]

Which of the following will result in the smallest rate of heat transfer?

What is the formula to calculate the rate of heat transfer in conduction?

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