A closed, rigid tank contains a two‐phase liquid–vapor mixture of Refrigerant 22 initially at −20°C with a quality of 50.36%. Energy transfer by heat into the tank occurs until the refrigerant is at a final pressure of 6 bar. Determine the final temperature, in °C. If the final state is in the superheated vapor region, at what temperature, in °C, does the tank contain only saturated vapor?

Respuesta :

Explanation:

The given data is as follows.

      Initial temperature of the system ([tex]T_{1}[/tex]) = [tex]-20^{o}C[/tex]

So, at state 1 quality of the system is ([tex]x_{t}[/tex]) = 0.5036

     Pressure at state 2, ([tex]P_{2}[/tex]) = 6 bar

As, it is a rigid tank hence, the specific volumes at state 1 and state 2 are equal.

So,       [tex]\nu_{2} = \nu_{t}[/tex]

Now, from the saturated refrigerant-22 table taking specific volume at [tex]-22^{o}C[/tex] is as follows.

                   [tex](\nu_{f})_{t} = 0.7427 \times 10^{-3} m^{3}/kg[/tex]

                   [tex](\nu_{g})_{t} = 0.0926 m^{3}/kg[/tex]

Thus,    [tex]\nu_{2} = \nu_{t}[/tex]

                       = [tex](\nu_{f})_{t} + x_{t} ((\nu_{g})_{t} - (\nu_{f})_{t})[/tex]

                       = 0.0007427 + 0.5036 (0.0926 - 0.0007427)

                       = [tex]0.04700 m^{3}/kg[/tex]

Hence,   [tex]\nu_{g}[/tex] = [tex]0.04700 m^{3}/kg[/tex]

Super heated refrigerant-22 tables take pressure at 6 bar. Interpolation method used to find the temperature is as follows.

             [tex]\nu_{t} = 0.04628 m^{3}/kg[/tex]    and    [tex]T_{t} = 40^{o}C[/tex]  

             [tex]\nu_{t} = 0.04724 m^{3}/kg[/tex]     and [tex]T_{2} = 45^{o}C[/tex]

        [tex]T_{vap} = T_{t} + \frac{(\nu_{g} - \nu_{t})(T_{2} - T)_{t}}{\nu_{2} - \nu_{t}}[/tex]

                    = [tex]40^{o}C + \frac{(0.04700 - 0.04727) \times (45 - 40)}{0.04724 - 0.04628}[/tex]

                    = 40 + 3.75

                    = [tex]43.75^{o}C[/tex]

Saturated vapor refrigerant-22 takes specific volume at [tex]0.04700 m^{3}/kg[/tex].

Therefore, interpolation method used to find the temperature will be as follows.

               [tex]\nu_{t} = 0.0492 m^{3}/kg[/tex]    and    [tex]T_{t} = -1.45^{o}C[/tex]

                [tex]\nu_{2} = 0.0469 m^{3}/kg[/tex]    and    [tex]T_{2} = 0.12^{o}C[/tex]    

             [tex]T_{\text{saturated vapor}} = T_{t} + \frac{(\nu_{g} - \nu_{t})(T_{2} - T_{t}}{\nu_{2} - \nu_{t}}[/tex]

                               = [tex]-1.45^{o}C + \frac{(0.04700 - 0.0492) \times (0.12 - (-1.45))}{0.0469 - 0.0492}[/tex]

                          = -1.45 + 1.50

                          = [tex]0.051^{o}C[/tex]

Thus, we can conclude that at [tex]0.051^{o}C[/tex] tank contains only saturated vapor.

A saturated vapor is when a substance exists as vapor at its saturation temperature.

At 0.05 °C, the tank will contain only saturated vapor.

What is the energy transfer?

The transfer of energy from one form to other is called energy transfer.

Given,

Initial temperature is −20°C

The state quality of the system is 50.36%

The specific volume of state 1 and state 2 are equal

So,  [tex]\bold{V_2 = V_t}[/tex]

Now, taking the specific volume is -22°C

[tex]\bold{(v_f)_t = 0.7427\times10^-^3 m^3/kg}[/tex]

[tex]\bold{(v_g)_t = 0.926 \; m^3/kg}[/tex]

Therefore,

[tex]\bold{V_2 = V_t}[/tex]

[tex]v_g = (V_f)_t+ x_t( (v_q)-(v_t)_t)\\\\v_g= 0.0007427+ 0.5036(0.0926-0.0007427)\\\\v_g= 0.04700\; m^3/kg\\\\v_g= 0.04700\; m^3/kg\\[/tex]

The pressure is 6 bar at Super heated refrigerant-22 table. Interpolation method will use here to find the temperature.

[tex]\bold{v_t = 0.04628\;m^3/kg\; and \; T_t= 40^\circ C}\\\\\bold{v_t = 0.04724\;m^3/kg\; and \; T_2= 45^\circ C}\\\\\\\bold{T_v_a_p= T_t + \dfrac{(v_q-v_t)(T_2-T_1)_t}{v_2-v_t}}\\\\\\\\\bold{T_v_a_p = 40^\circ c+ \dfrac{(0.04700-0.04727)(45-40)_t}{0.04724- 0.04628}}\\\\\\\\\bold{T_v_a_p = 40^\circ c + 3.75}\\\\\bold{T_v_a_p = 43.75^\circ c}[/tex]

The volume is [tex]v_g= 0.04700\; m^3/kg\\[/tex]

The interpolation method will be used to find the temperature

[tex]\bold{v_t = 0.0492\;m^3/kg\; and \; T_t= -1.45^\circ C}\\\\\bold{v_t = 0.0469\;m^3/kg\; and \; T_2= 0.12^\circ C}\\\\\\\bold{T _s_/_v= T_t + \dfrac{(v_q-v_t)(T_2-T_1)_t}{v_2-v_t}}\\\\\\\\\bold{T_v_a_p = 1.45^\circ c+ \dfrac{(0.04700-0.0492)(0.12-(-1.45)}{0.0469- 0.0492}}\\\\\\\\\bold{T_v_a_p = 1.45^\circ c + 1.50}\\\\\bold{T_v_a_p = 0.051^\circ c}[/tex]

Thus, At 0.05 °C, the tank will contain only saturated vapor.

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