A. $$\frac{{{{\text{e}}_1}{{\text{e}}_2}}}{{{{\text{e}}_1} + {{\text{e}}_2} - {{\text{e}}_1}{{\text{e}}_2}}}$$
B. $$\frac{1}{{{{\text{e}}_1}}} + \frac{1}{{{{\text{e}}_2}}}$$
C. e1 + e2
D. e1e2
Answer: Option A
This Question Belongs to Mechanical Engineering >> Refrigeration And Air Conditioning
Nusselt number (NN) is given by
A. $${{\text{N}}_{\text{N}}} = \frac{{{\text{h}}l}}{{\text{k}}}$$
B. $${{\text{N}}_{\text{N}}} = \frac{{\mu {{\text{c}}_{\text{p}}}}}{{\text{k}}}$$
C. $${{\text{N}}_{\text{N}}} = \frac{{\rho {\text{V}}l}}{\mu }$$
D. $${{\text{N}}_{\text{N}}} = \frac{{{{\text{V}}^2}}}{{{\text{t}}{{\text{c}}_{\text{p}}}}}$$
In case of sensible heating of air, the coil efficiency is given by (where B.P.F. = Bypass factor)
A. B.P.F. - 1
B. 1 - B.P.F.
C. $$\frac{1}{{{\text{B}}{\text{.P}}{\text{.F}}{\text{.}}}}$$
D. 1 + B.P.F.
The undesirable property of a refrigerant is
A. Non-toxic
B. Non-flammable
C. Non-explosive
D. High boiling point
The desirable property of a refrigerant is
A. Low boiling point
B. High critical temperature
C. High latent heat of vaporisation
D. All of these
Option a is incorrect. There is type error. Numerator is e1e2.not e1 + e2.interchange factor is 1/(1/e1 + 1/ e2).refer radiation heat transfer for more information
explain how