Question

A piston-cylinder device initially contains water liquid-vapor mixture at the pressure of 700 kPa. The liquid-vapor mixture has 0.1 m3 of liquid water and 0.9 m3 of water vapor. Heat is transferred at constant pressure until the temperature reaches 320 °C. (a) What is the initial temperature of the water

Answer 1

Given question is incomplete. The complete question is as follows.

A piston-cylinder device initially contains water liquid-vapor mixture at the pressure of 700 kPa. The liquid-vapor mixture has 0.1 m3 of liquid water and 0.9 m3 of water vapor. Heat is transferred at constant pressure until the temperature reaches 320 °C.

(a) What is the initial temperature of the water.

(b) Determine the total mass of the water.

Explanation:

(a) We are given that initially there are two phase regions present.

       Initial temperature = saturation temperature at 700 Kpa

                                       = $165^{o}C$

Hence, the initial temperature of the water is $165^{o}C$.

(b)  At 700 Kpa, the saturation pressure will be as follows.

       $v_{f} = 1.108 \times 10^{-3} m^{3}/kg$

      $v_{g} = 0.273 m^{3}/kg$

So,    $m_{f} = \frac{0.1}{1.108 \times 10^{-3}}$

                    = 90.25 kg

        $m_{g} = \frac{0.9}{0.273}$

                    = 3.3 kg

Therefore, total mass will be calculated as follows.

               90.25 kg + 3.3 kg

            = 93.55 kg

Hence, total mass of the water is 93.55 kg.