Concept explainers
Complete the blank cells in the following table of properties of refrigerant-134a. In the last column, describe the condition of refrigerant-134a as compressed liquid, saturated mixture, superheated vapor, or insufficient information, and, if applicable, give the quality.
The following table for refrigerant-134a which are blank.
P, kPa | u, kJ/kg | x, quality | Phase description | ||
320 | -12 | ||||
1000 | 39.37 | ||||
40 | 1.17794 | ||||
180 | 0.0700 | ||||
200 | 249 |
Explanation of Solution
State 1
Refer to Table A-12, obtain the value of saturated temperature at a pressure of 320 kPa as
The given temperature in state 1 is less than the saturated temperature at a pressure of 320 kPa.
Hence, state 1 is compressed liquid.
As wee see now there is no data for compressed liquid water in table A-7 for pressure 320 kPa, so calculate the specific internal energy and specific volume of a mixture at a saturated refrigerant-134a at a temperature of
State 2
Refer to Table A-4, obtain the specific volume at saturated liquid and specific internal energy at saturated liquid at a temperature of
Thus, the state 2 condition is saturated liquid.
State 3
Refer to Table A-13, “Superheater refrigerant-134a”, obtain the pressure and specific internal energy at a temperature and specific volume of
The given specific internal energy is greater than the specific internal energy at saturated vapour at a pressure of 140 kPa refer from Table A-12.
Thus, state 3 is a superheated steam.
State 4
Refer to Table A-12, obtain the specific volume and specific internal energy at saturated liquid
As we see now the given specific volume of the mixture
Hence, the state 4 is known as saturated mixture.
Refer to Table A-12, obtain the temperature at a pressure of 180 kPa as
Calculate the quality at state 1.
Substitute
Calculate the specific internal state.
Here, specific internal energy at saturated liquid and saturated vapour is
Substitute
State 5
Since
Thus, the state 5 is superheated steam.
Convert the unit of pressure from kPa to MPa.
Refer to Table A-13, obtain the temperature and specific volume at a pressure of 0.20 MPa and specific intenal energy of 249 kJ/kg as
From the above calculations and referred from the steam table, complete the table of
P, kPa | u, kJ/kg | x, quality | Phase description | ||
320 | -12 | --- | compressed liquid | ||
1000 | 39.37 | -- | saturated liquid | ||
40 | 1.17794 | - | superheated steam | ||
180 | 0.0700 | saturated mixture | |||
200 | 249 | -- | superheated steam |
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