Heat Transfer

1

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 K/D `((Dvp)/(mu))^0.8 . ((C_(p mu))/(K))^0.4`
This is valid for the value of NRe equal to

A. . < 2100
B. 2100-4000
C. > 4000
D. > 10000

2
`( N_(Re) . N_(Pr))`  (D/L) is called the __________ number 
A. Peclet
B. Stanton
C. Graetz
D. none of these

3
For a counter current heat exchanger with Tih =` 80^circC`, `T^circ`c=` 60^circC`, `T^circ`h =` 50^circC` andTic = `30^circC`, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy


A. `(d^2T)/(dZ^2) > 0`
B. `(d^2T)/(dZ^2) = 0`
C. `(d^2T)/(dZ^2) < 0`
D. `(dT)/(dZ) = 0`

4

Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface)

A. `U_1 - U_2`
B. `1/U_1 - 1/U_2`
C. `1/U_2 - 1/U_1`
D. `U_2 - U_1`

5

In case of surface condensers, a straight line is obtained on plotting `1/U`    vs__________ on an ordinary graph paper.


A. 1/`overline(V) `- 0.8
B. `overline(V) `- 0.8
C. `overline(V) `- 2
D. 1/`overline(V) `- 2