On Wed, Nov 13, 2013 at 6:43 AM, Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx> wrote: > Keith Henson wrote: >> >> On Wed, Nov 13, 2013 at 12:49 AM, Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx> >> wrote: >> >>> Keith Henson wrote: >>> >>>> I have a fairly bizarre problem. Need to get rid of 3 GW of waste >>>> heat from lasers in orbit. The pump diodes use a total flow of 60 >>>> cubic meters per second at 22 deg C inlet and 34 deg C outlet. >>> >>> Take the working temperature further down ? ( increases efficiency ) >> >> The laser efficiency goes up as you take the working temperature down, >> but not much. > > 300K to 100K can give you 50% Do you have a reference for this? > Other effects work against it, though looking around > theres quite a bit of work around on cryogenically cooled laser diodes. > so it must make some sense. ( But I haven't kept current in that area ) >> >>> look into other coolants that are lighter and have less viscosity? >> >> It's hard to beat water >> >>> wild shot: >>> find a way to compress (centrifuge ? ) the evaporated coolant >>> to higher temperatures, radiate away the heat ... >> >> this is a possibility. It gets tricky not just because of the extra >> energy needed to pump the heat uphill, but because the radiator walls >> must be thicker to take the higher pressure. >> > What about that heat exchanger from the Sabre project :-? I am reluctant to use heat exchangers at all because of the temperature drop across the exchanger, even counter current ones. Keith > uwe > >