Question

g Water at 25C, 20 bar is heated under constant pressure.a) Determine the final state if the amount of heat is 500 kJ/kgb) Determine the final state if the amount of heat is 1500 kJ/kgc) Determine the final state if the amount of heat is 3000 kJ/kg

Answer 1

Step-by-step explanation:

Given that:

At the inlet:

Temperature
`T_1 = 25^0 \ C`

Pressure
`P_1` = 20bar = 2000 kPa

At the outlet:

`P_2 = 2000 \ kPa`

a)

Q = 500 kJ/kg

Using the steam tables to determine the properties of water;

`h_1 = 106.6863 \ kJ/kg \\ \\ h_2 -h_1 = 500 \\ \\ h_2 = (500 + 106.6863) \ kJ/kg \\ \\ h_2 = 606.68 \ kJ/kg`

`at \ p_(sat)= 2000 \ kPa; \ h_f = 908.47 \kJ/kg; \ h_g = 2798.3 \ kJ/kg} \\ \\ h_2< h_f; \text{thus, the soil is compressed or subcooled liquid}`

b)

`Q = 1500 \ kJ/kg\\ \\ Q= (h_2-h_1) \\ \\ h_2 = 1500 + 106.6863 \\ \\ h_2 = 1606.6863 \ kJ/kg \\ \\ h_f < h_2<hg \ at \ 2000 \ kPa`

Thus, the outlet steam will be a vapor-liquid mixture at 212.38° C

c)

`Q = 3000 \ kJ/kg \\ \\ Q = h_2 -h_1 \\ \\ h_2 = Q + h_1 \\ \\ h_2 = 3000 + 106.6863 \\ \\ h_2 = 3106.6863 \ kJ/kg\\ \\ h_2 > hg \ at \ 2000 \ kPa`

Thus, the outlet steam will be a superheated vapor at 380° C