The more I look this over the better it looks. I've seen flat tubes like he's using at a site that is involved in new and advanced designs that intends to replace the now common alum. car heater cores & rads with these flat thin walled tubing along with copper fins.
Just the fact his tubes are copper instead of brass should offer a pretty pronounced boost in heat transfer. Then couple in the lower flow resistence of the flat tubes vs. a heater cores Z type flat tubes and it gains a second boost from increased flow rates.
I like your design work Copyman, looks to me like you've done some serious design work.
Would still be interested in the inlet/out let design and the L x W x H demensions.
