$15,0001$b$/$h of benzene will be heated from $80$F to $120$F by cooling a stream of orthotoluidine $($C$7$H$9$N$)$ from $160$F to $100$F Inlet pressures are $40$psia for ortho$-$toluidine and $50$psia for benzene. A maximum pressure drop of $15$ psia is specified for each stream. A

number of used carbon steel hairpins are available for this service. The hairpins are each

$20$ ft long with $3-$in$.$ schedule $40$ outer pipe, $1\mathrm{.}5-$in$.$ un$-$finned schedule $40$ inner pipe,

internal return bends and $2-$in$.$ schedule $40$ nozzles. Properties of ortho$-$toluidine at $130$F

are given below. Determine the number and configuration of hairpins required for this

service.

Property

Value

k $($BTU$/$h ft F$)$

$0\mathrm{.}081$

$($cP$)$

$1\mathrm{.}85*$

$($lbm$/$ft$3)$

$60\mathrm{.}5$

Pr

$26\mathrm{.}5$

Cp $($BTU$/$lbm F$)0\mathrm{.}48$

log$10()=1085\mathrm{.}1((1)$

$356$

$1\mathrm{.}46)$