Problem 3.4) a) Standard sea level pressure is approximately 1013 hPa and standa

Question

Problem 3.4)

a) Standard sea level pressure is approximately 1013 hPa and standard surface temperature in the U.S. Standard Atmosphere is 15C. What is the density of dry air under these conditions?

b) A sample of dry air has a pressure of 400 hPa and a density of 0.7 kg/m3. What is its temperature in degrees Celsius?

c) A sample of dry air has a temperature of 30C and a specific volume of 2.0 m3/kg. What is its pressure?

d) The record low observed surface pressure (in Typhoon Tip, 1979) was 870 hPa; the record high (Mongolia, 2011) was 1087 hPa. Air temperature at the surface can easily vary between -40C and +50C. Find the densities of air corresponding to all four possible combinations of the above extremes.

e) Based on your answers to (b), which of the two variables, pressure or temperature, is typically responsible for the most pronounced variations in the density of air at sea level?

Explanation / Answer

Given that

Standard sea level pressure is approximately (P) =1013 hPa =101300Pa

The standard surface temperature in the U.S. Standard Atmosphere is (T) =15C. =288K

What is the density of dry air under these conditions is given by

p =P/Rspecific*T

Where R specific =287.058J/(Kg.K)

Therefore p =101300/287.058*288 =1.2253kg/m3

2)

A sample of dry air has a pressure of 400 hPa =40000Pa nd a density of 0.7 kg/m3. What is its temperature in degrees Celsius is given by

p =P/Rspecific*T

Where R specific =287.058J/(Kg.K)

T =P/Rspecific*p = 40000Pa/287.058J/(Kg.K)*0.7 kg/m3 =199.06K nearly 200K

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