Editing Heat exchanger (section)

===Direct contact===
Direct contact heat exchangers involve heat transfer between hot and cold streams of two phases in the absence of a separating wall.<ref>Coulson, J. & Richardson, J. (1983), Chemical Engineering – Design (SI Units), Volume 6, Pergamon Press, Oxford.</ref> Thus such heat exchangers can be classified as:
* Gas – liquid
* [[Miscibility|Immiscible]] liquid – liquid
* Solid-liquid or solid – gas

Most direct contact heat exchangers fall under the Gas – Liquid category, where heat is transferred between a gas and liquid in the form of drops, films or sprays.<ref name=":0" />

Such types of heat exchangers are used predominantly in [[air conditioning]], [[humidification]], industrial hot [[water heating]], [[water cooling]] and condensing plants.<ref>Hewitt G, Shires G, Bott T (1994), Process Heat Transfer, CRC Press Inc, Florida.</ref>

{| class="wikitable"
|-
! Phases<ref>Table: Various Types of Gas – Liquid Direct Contact Heat Exchangers (Hewitt G, Shires G & Bott T, 1994)</ref>
! Continuous phase
! Driving force
! Change of phase
! Examples
|-
| Gas – Liquid
| Gas
| Gravity
| No
| Spray columns, [[Packed bed#Packed column|packed columns]]
|-
|
|
|
| Yes
| [[Cooling tower]]s, falling droplet evaporators
|-
|
|
|Forced
|No
|Spray coolers/quenchers
|-
|
|
|Liquid flow
|Yes
|Spray condensers/evaporation, jet condensers
|-
|
|Liquid
|Gravity
|No
|[[Bubble column reactor|Bubble columns]], perforated tray columns
|-
|
|
|
|Yes
|Bubble column condensers
|-
|
|
|Forced
|No
|Gas spargers
|-
|
|
|Gas flow
|Yes
|Direct contact evaporators, submerged combustion
|}