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Cake day: November 14th, 2023

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  • Heat pumps work by using a high power pump to compress the working fluid from its gas state to liquid. This compression heats the gas to 30 C over ambient. That high temp is then cooled through coils to air temp (30C on a hot day). In the winter it runs in reverse. It takes expands gas which in the case of a heat pump fluid like R-410a boils at -48C, runs that -48C gas through the coils which picks up heat from the outside at -1C (48C hotter than the gas). It then compresses that fluid to 20C which is then released into the house. That’s why heat pumps can freeze up in the winter. The cold cycle is so far below freezing that ice will form on the coils. So heat pumps switch to AC mode every now and then in the winter to warm up their coils to melt the ice off (while turning off the fan in the house). The need for a large temperature difference is why heat pumps don’t work if it gets below -20C.

    So a heat pump moves heat but requires a large temp difference which comes from the electric compressor. You also can’t extract significant work from that heat difference once you factor the energy input of the compressor. Otherwise heat pumps would have a device to power part of itself from the heat that it is moving.


















  • Makes me feel better about not buying Bambu. At the time of their closing off their printers fans claimed it was a technicality in their change to their license and wouldn’t affect anything.

    They’re no longer the best in their price ranges. Under $500 there are several enclosed CoreXY that are better than the A1 and even an Anycubic X that’s has a far more advanced print head over the A1.

    In the under $1000 category the U1 outclasses everything Bambu while being completely open source.

    The “eco system” claim for Bambu is a marketing lie. Any printer lets you download models from any website, including Bambu, and print. Most all printers let you scan the RFID tag on compatible filament to save the time of adding it on the printer’s screen. But other printers like Snapmaker are adding rfid support for all filament brands.