5 ms·

Ships, Bananas, Logistics, Math and a Big Dose of Engineering

• weinzierl 7y ago
  > Those reefer positions all need power. We used to factor around 4kW for a reefer... so that would be around 4MW total. Easy! Problem is, bananas are not average. Most frozen cargo is taken onboard frozen. It doesn't take much power to keep it frozen at -21degC > Bananas are different though - they are often packed warm, and brought directly to the ship. They are also kept at +14degC. This means the refrigeration needs to work harder. > We are now looking at as much as 20kW to cool that container when it comes onboard, and 8kW to maintain the temperature. We've jumped to 8MW at least! I don't buy that. Sure, cooling to 14C will require some extra energy for a limited amount of time, but why would 4 kW be enough to keep a -21C container at that temperature while it takes 8 kW to keep a container at 14 C. Doesn't make any sense. Of course that doesn't mean the conclusion that regular container ships cannot go 100% bananas is wrong. At least @cybergibbons seems know what they are talking about. I just think there is a gap in the argumentation or that I just misunderstood. EDIT: @cybergibbons address this objection [1]. What I understand is that frozen cargo is stored at -21C but then allowed to warm up wheres bananas are cooled and then held at a constant temperature in the ship. [1] https://twitter.com/cybergibbons/status/1213593041740664832 https://twitter.com/cybergibbons/status/1213593041740664832
  • jamez1 7y ago
    It takes a lot of energy for matter to change states from frozen. This would be a large buffer: https://en.wikipedia.org/wiki/Latent_heat https://en.wikipedia.org/wiki/Latent_heat