4 ms·
Can you list some examples of where this is used in engineering (software or otherwise)?
by umvi 6y ago
Can you list some examples of where this is used in engineering (software or otherwise)?
- throwawayboise 6y agoA fresh air exchanger in an HVAC system. The fresh external air coming in is [warmed|cooled] by the interior air being exhausted.
- fy20 6y agoAlso know as a heat recovery ventilator. If you are building a new house, read up on these, as you probably want one.
- pfdietz 6y agoOpen hearth steel mills. Regenerators in some gas turbines. Dialysis machines. Liquid-liquid extraction. Isotope separation cascades. Fractional distillation columns. Most heat exchangers are countercurrent, as it minimizes entropy generation.
- Retric 6y agoMilk pasteurization is one of the best examples. You start with milk at 4C, heat it to ~70C via heat exchanger (+66C), then 75c via heating (+5C), wait 15 seconds for pasteurization, cool down to ~9C via heat exchanger (-66C), then just chill to 4C via refrigeration (-5C). This requires ~1/14th the energy to heat the milk and also rapidly cools it down below ambient temperature afterwards saving even more energy. You see similar approaches for a lot of large scale chemical processes.
- dorfsmay 6y agoI had never heard of this, the use of already existing heat is amazing! Do they run 24/7? If not, they must use a lot of energy to cold start the process. One classic example I always hear about efficient use of heat exchanger is the building of.swimming pool in the same building as ice rink. The heat produce cooling one is used to warm the other.
- iancmceachern 6y agoIntercooler, dialysis
- datameta 6y agoHVAC systems. The outgoing air goes through a heat exchanger to transfer heat to the colder incoming air.
- amluto 6y agoAs far as I know, most HRVs are cross-current. I don’t know why.
- pfdietz 6y agoAvoiding condensation? Rotating disk heat recovery devices can also recover humidity.
- amluto 6y agoI think most HRVs have condensation drains, so I doubt that avoiding condensation is the major consideration. I would guess it’s more of a geometric consideration. A square cross-current heat exchanger can have each port on a different side, so the whole perimeter is used. A counter-current exchanger would have two ports on each of two sides and no ports in the other sides, leading to a rather more complicated and larger arrangement.
- _Microft 6y agoCheck Wikipedia, the article has examples: https://en.wikipedia.org/wiki/Countercurrent_exchange https://en.wikipedia.org/wiki/Countercurrent_exchange
- pfdietz 6y agoThe page also talks about a variant, countercurrent multiplication. There's a really nice example of this in hydrogen isotope separation. The technique, called CECE (Combined Electrolysis Catalytic Exchange), was developed in Canada for production of heavy water and removal of tritium from heavy water. The centerpiece of the system is a catalytic exchange column. In the column, liquid water flows down, while hydrogen gas (of various isotopes) flows up. At each point, a wet-proofed catalyst promotes the exchange of hydrogen atoms between the water and the gas. In equilibrium, protium partitions more into the gas phase than into the liquid, so as the gas goes up the tower the heavier isotopes are stripped into the liquid phase and carried back down. At the bottom, the water is fed into electrolysis cells to produce gas to feed back into the tower. Over time, the water in the cells becomes enriched in heavier isotopes and can be tapped off. With this system, any H2 electrolysis plant could modified to also produce heavy water. This has troubling implications for nuclear proliferation in the coming "hydrogen economy", as heavy water reactors can be small and easy to hide, and have been used in the past for nations to enter the "Nuclear Club".