In space-based systems, such as the International Space Station, for example, highly efficient cooling systems are deployed that involve force convection boiling. In a laboratory experiment to develop one such system, a test liquid, which has the physical properties given, flows inside a vertical tube of 1.905 cm (or 0.75 in) inner diameter with a mass flux (or mass velocity) of 680 kg/(m2s). Determine the heat transfer coefficient at a point along the length of the tube at which the quality is 0.3. The wall temperature at this location was measured to be 1800C.

Question

GIVEN

? 1.905 cm vertical tube with flowing, boiling water inside

? Test liquid with properties given above

? Mass flux (G)= 680 kg/(m2s)

FIND

(a) Heat transfer coefficient at a point along the length of the tube at which the quality is 0.3

ASSUMPTIONS

? The method of Chen is applicable

? Prandtl number of the fluid is Prl=1.0

PROPERTIES AND CONSTANTS

Answer 1

We will follow the method of Chen described in Section 9.3.2.



The convective component of the heat transfer coefficient is



The convective component of the heat transfer coefficient is



To find F, we must first find X from



then F is



and the convective heat transfer coefficient is



We have



Now, the boiling heat transfer coefficient is given by Equation (9.12)



To find S, we need ReTP



and we find S from



So the expression for the boiling heat transfer coefficient is



Thus, heat transfer coefficient at a point along the length of the tube at which the quality is 0.3