Final answer:
In a 1-D, steady subsonic flow, the stagnation pressure will decrease along the direction of the flow as the stagnation temperature decreases due to heat transfer.
Step-by-step explanation:
According to the equation of continuity for incompressible fluids, when the cross-sectional area of a flow decreases, the velocity of the fluid must increase to maintain a constant flow rate. In this case, as the stagnation temperature decreases along the direction of the flow due to heat transfer, the fluid velocity will increase to compensate for the decrease in density, ensuring that the flow rate remains constant.
As a consequence of the increased fluid velocity, there will be a pressure drop in the rapidly-moving fluid. This can be understood by considering the net force on the fluid resulting from the pressure difference. The pressure times area equals force equation indicates that as the area decreases, the force acting on the fluid decreases, leading to a drop in pressure. Therefore, along the direction of the flow, the stagnation pressure will decrease.