A water block will transfer more heat if water is left in place, but you'll get a temp rise which is'nt wanted...
You were
trying to heat the coolant/water no?. we're not. Leaving the water in place longer will cause a higher temp which will cause a higher DT(?) which will heat the water more
but we are trying not to let the temp rise, but to cool it. Carrying the heat off at the lowest temp...
PS. This is'nt a statement, it's my guess. I don't understand fully heat transfer 'lingo/theory' much either. Unfortunatly I don't have the interest/drive to investigate it fully so I only dabble when I feel I need to
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PPS. Halo BillA!!, hows work?. Getting your own way I hope!...