COST OF PIPES AND PUMPS
Now we need to find expressions for the capital cost of the pipes and pumps. In
general, for the entire system the pump capital costs will be assumed to be of the
following form
Cpumps = A1np + A2( md /ρd) ∆Pd
˙
(2-14)
where A1 =
empirical constant ($/pump)
A2 =
empirical constant ($/W)
np =
number of pumps
∆Pd =
total pressure drop (supply and return) at design flow rate (N/m2).
The total pressure drop at maximum flow conditions is given by
∆Pd = a εb (4/π)2+c A6 md 2+c L d(5+b+c)
˙
(2-15)
where A6 = [(ρ1 c)d,s+ (ρ1 c)d,r]/2 (m3+c sc/kg1+c).
So, our pump cost becomes
Cpumps = A1 np + A5 d (5+b+c)
(2-16)
where A5 = A2a εb(4/π)2+c A7,d md 3+c L ($ m5+b+c)
˙
A7,d = A7 evaluated at the design condition (m6+c sc/kg2+c).
For the capital cost of the supply and return piping, including installation, we
assume the following form
Cpipes = (A3 + A4d)L
(2-17)
where A3 = empirical constant ($/m)
A4 = empirical constant ($/m2).
COST OF MAINTENANCE AND REPAIR
The cost of maintenance and repair is assumed to be of the following form
Cm&r = PVFm&r Am&r Cpp
(2-18)
where Am&r = annual maintenance and repair rate as a fraction of initial capital cost
(dimensionless)
PVFm&r = present value factor for maintenance and repair costs (dimension-
less).
TOTAL COST
With each of the component costs defined, our expression for the objective
function, the total cost Ct, becomes
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