_In a double pipe (concentric) heat exchanger, the hydraulic radius for heat transfer (for a fluid flowing through the annulus) would be$?

D‚Äö√á√á - D‚Äö√á√Ö (D‚Äö√á√Ö and D‚Äö√á√á are I.D. of inner and outer pipes respectively)

_In a double pipe (concentric) heat exchanger, the hydraulic radius fo

1.	_In a double pipe (concentric) heat exchanger, the hydraulic radius for heat transfer (for a fluid flowing through the annulus) would be$?
A.	Same as that for fluid flow
B.	Less than that for fluid flow
C.	More than that for fluid flow
D.	D‚Äö√á√á - D‚Äö√á√Ö (D‚Äö√á√Ö and D‚Äö√á√á are I.D. of inner and outer pipes respectively)
Answer» D. D‚Äö√á√á - D‚Äö√á√Ö (D‚Äö√á√Ö and D‚Äö√á√á are I.D. of inner and outer pipes respectively)