A closed tank contains oxygen at 20°C at a gage pressure of 150 kPa. Determine the temperature if the oxygen is compressed isentropically to a gage pressure of 325 kPa. The atmospheric pressure is 101.3 kPa and the specific heat ratio of oxygen is 1.40. Express your answer in °C to three significant figures.

Respuesta :

Explanation:

As it is given that process is entropic which means that it is reversible adiabatic in nature.

Also, the given data is as follows.

      [tex]T_{1}[/tex] = [tex]20 ^{o}C[/tex] = (20 + 273) K = 293 K

           Gage pressure = 150 kPa,      Atmospheric pressure = 101.3 kPa

Hence, pressure ([tex]P_{1}[/tex]) will be (150 kPa + 101.3 kPa) = 251.3 kPa

and,  pressure ([tex]P_{2}[/tex]) will be (325 kPa + 101.3 kPa) = 426.3 kPa

Also, specific heat ratio ([tex]\gamma[/tex])is given as 1.40.

Hence, relation between T and P is as follows.

       [tex]T \times P \times (\frac{1 - \gamma}{\gamma})[/tex] = constant

      [tex]T_{1}P_{1} \times (\frac{1 - \gamma}{\gamma})[/tex] = [tex]T_{2}P_{2} \times (\frac{1 - \gamma}{\gamma})[/tex]

             [tex]T_{2}[/tex] = [tex]T_{1} \times \frac{P_{1}}{P_{2}} \times \frac{-0.4}{1.4}[/tex]

                          = [tex]293 K \times \frac{251.3kPa}{426.3kPa} \times \frac{-0.4}{1.4}[/tex]

                          = 340.758 K

Hence, convert this temperature into degree celsius as follows.

                          [tex](340.758 - 273) ^{o}C[/tex]

                           = [tex]67.758 ^{o}C[/tex]

Thus, we can conclude that the temperature is [tex]67.758 ^{o}C[/tex].

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