Question

A direct contact heat exchanger (where the fluid mixes completely) has three inlets and one outlet. The mass flow rates of the inlets are 1kg/s, 1.5kg/s and 2 kg/s. The enthalpy of those inlets are the 100kJ/kg, 120kJ/kg, and 500kJ/kg, respectively. What is the enthalpy at the outlet?

Answer 1

Enthalpy at outlet=284.44 KJ

Step-by-step explanation:

`m_1=1 Kg/s,m_2=1.5 Kg/s,m_3=22 Kg/s`

`h_1=100 KJ/Kg,h_2=120 KJ/Kg,h_3=500 KJ/Kg`

We need to Find enthalpy of outlet.

Lets take the outlet mass m and outlet enthalpy h.

So from mass conservation

`m_1+m_2+m_3=m`

m=1+1.5+2 Kg/s

m=4.5 Kg/s

Now from energy conservation

`m_1h_1+m_2h_2+m_3h_3=mh`

By putting the values

`1* 100+1.5* 120+2* 500=4.5* h`

So h=284.44 KJ