heat transfer ex 2

the velocity of a fluid relative to immersed solid body far away from body is, velocity of the approaching fluid far ahead of body is

free stream velo, upstream velo

identify how the average friction and heat transfer coeffs are determined in flow over flat plate

determined by integrating the local friction and heat transfer coeds over the entire plate, then dividing by length of plate

the level of turbulence and heat transfer coefficient ______ with row number

increases

heat transfer coefficient increases in the transverse direction for a given row number, true or false?

false, no change in transverse direction

in flow across tube banks, reynolds number is defined in the basis of max velocity because the flow characteristics are dominated by the _____

maximum velocity

true for laminar and turbulent flow

Pr » 1 for oils, thermal entry length is larger than hydrodynamic entry length in laminar flow

Pr«1 for liquid metal’s, thermal entry length is smaller than hydrodynamic entry length in laminar flow

in turbulent, hydrodynamic and thermal entry lengths are independent of Re and Pr numbers, and comparable in magnitude

the region in which the flow is both hydro dynamically and thermally developed is called the ____ region

fully developed

consider laminar forced convection in a circular tube. the heat transfer coefficient is the highest _____

at the inlet of the tube

what is the exact representation of the average temperature difference between the fluid and surface for an entire tube

delta T(ln)

force that causes natural convection currents is

buoyancy

(Y/N) the convection heat transfer coefficient is usually higher in natural convection than in forced

No

physically, the grashof number represents

the ratio of buoyancy force to the viscous force acting on the fluid

consider a heat sink with optimum fin spacing. removing some of the fins would :

decrease the heat transfer surface area, increase the heat transfer coefficient