Question

Refrigerant-134a enters the expansion valve of a refrigeration system at 130 psia as a saturated liquid and leaves at 20 psia. Determine the temperature and internal energy changes across the valve. Use data from the steam tables.

Answer 1

The answer is "
`\bold{-98.079 ^(\circ) F \ \ and \ -2.6686 (Btu)/(lbm)}`"

Step-by-step explanation:

Calculating the value from the property tables of R-134a,

At 130 psia:

`T_1= 95.64^(\circ) \ F`

Internal energy:

`u_1= 43.258 \ (Btu)/(lbm)`

At 20 psia:

`T_2= -2.43^(\circ) \ F`

Internal energy

`u_2= 40.5894 \ (Btu)/(lbm)`

Calculating temperature:

`\to \Delta T= T_2-T_1`

`= -2.43-95.64\\\\= -98.079^(\circ) \ F`

Calculating internal energy:

`\to \Delta u= u_2-u_1\\\\`

`= 40.5894 -43.258 \\\\=-2.6686 \ (Btu)/(lbm)`