I have a complicated expression which involves RootOf. How to get rid of and simpliy the equation?

I am looking for an expression for eta(H) not a numerical value.  

eta(H)sheet1.mw  

restart:
nuhf:=0.294*10^(-6):
Rehf:=Vhf*H/nuhf:
Vhf:=0.5:
rhohf:=965.31:
Lhs:=2.5*10^(-3):
DP1:=f1*Lhs*rhohf*Vhf^2/(2*H):
f1:=4*18.3/Rehf:
Whs:=1:
mhf:=rhohf*Vhf*Whs*H:
Rehf:=Vhf*H/nuhf:
PL1:=DP1*mhf/rhohf:
DP2:=f2*Lhs*rhohf*Vhf^2/(2*H):
f2:=0.3164/(Rehf^(0.25)):
PL2:=DP2*mhf/rhohf:
procd:=proc(H)
    if Rehf<1000 then PL1 elif Rehf>1000 then PL2 else 0 fi;
   end;

plot('procd(H)',H=0..0.002);

I am facing difficulty to realize this double iterative process. 

The equations in question are 

The flow chart for the iterative process is given as