Engineering consideration 3 - Cooling gases or liquids

Gases

A spray of coolant can be used to cool a gas.  In most cases the gas will be in motion - for example, the cooling of a gas steam to protect equipment further downline in the process.  A gas stream can be cooled directly or indirectly by cooling the pipe through which it flows.  In the case of direct cooling, where the coolant is sprayed into the gas, one needs to consider whether the gas is soluble in the coolant.  If the gas is insoluble or if solubility does not matter (i.e. the loss of some gas by dissolving in the coolant) then direct cooling can be safely used.

Furthermore, one needs to consider whether it is acceptable to have water vapour (coolant) mixed with the gas.  If, for whatever reason, water vapour cannot be present, then if direct cooling is to be performed, consideration will need to be given to its removal.  Typically a mist eliminator will be deployed to catch any coolant.  Eliminators will be rated up to a certain volume per minute and this will impose a limit on the amount of coolant that can be sprayed.  With this limitation present careful consideration will need to be given to which consistency of spray will produce the required cooling within those restricted parameters. (See the droplet size key Engineering Considerations for more details).

Liquids

Similar decisions need to be made when cooling liquids but clearly removal of mixed fluids by mist eliminators or evaporation is not an option.