Question

Consider a mixing chamber in which liquid water at 40°C mixes with superheated steam at 5 MPa and 300°C and converts it into dry saturated steam which leaves the chamber. If the inlet steam mass flowrate is 0.5 kg/s, determine the corresponding liquid water injection rate. (A) 0.0121 kgs(B) 0.0185 kgs (C) 0.0248 kgs

Answer 1

so correct option is (C) 0.0248 kg/s

Step-by-step explanation:

given data

liquid water = 40°C

steam pressure = 5 MPa

steam temperature = 300°C

steam mass flow rate = 0.5 kg/s

solution

we will apply here energy balance equation that is

m1 × h1 + m2 × h2 = (m1+m2) × h3 ................1

so we can say

m1 × ( h3-h1) - m2× ( h2 - h3) ..............2

and here m1 will be

m1 =
`m2 * (h2-h3)/(h3-h1)` ....................3

here we know at 40 degree h1 is 167.50 kJ/kg

and for pressure 5MPa we have know saturated temperature is 264 degree

but we have 300 degree that is supersaturated region

so by steam table we get

h3 enthalpy of dry saturated T3 is 2.63.977 degree C

and h3 = h at pressure 5MPa

T = 263.977 so it will 2793.7 kJ/kg

so now put all value in equation 3 we get

m1 =
`0.5 * (2923.5-2793.7)/(2793.7-167.50)`

m1 = 0.02471 kg/s

so correct option is (C) 0.0248 kg/s