Some possibly "best case" sums may interest.
Using 2mm OD and photo of nozzle estimate Nozzle 1mm ID.
Offset (H) of 3mm
Taking 200 LPH ( 28.5714 LPH per Jet) which gives a Velocity of ~ 10.1m/s
Calculated for a Circular Die using Flomerics Jet Impingement calculator.
The Flomerics calculator does show an increase in Heat Transfer Coeff with decreasing offset(within the calculator limits of 2D <= H <= 12D) .
This is an Offshoot of other play and am not(ATM) pursuing.