Question

A stream of refrigerant- 134a at 1 MPa and 20°C is mixed with another stream at 1 MPa and 80°C. If the mass flow rate of the cold stream is twice that of the hot one, determine the temperature of the exit stream. Put in the temperature as answer. In °C.

Answer 1

Answer: The exit temperature will be 40 C

Step-by-step explanation:

Using a baseline of 0 C, the heat content of the streams will be:

H (hot stream) = mass rate x Cp (heat capacity) x (80 - 0)

H (cold stream) = 2 x mass rate x Cp x (20 - 0)

H (exit stream) = 3 x mass rate x Cp x (T exit - 0)

But the exit heat content equals the sum of the cold and hot streams, so

3 x (Texit) = 80 + (2 x 20) = 120 C

So T exit = 40 C