Nongravitational condensate removal

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One of the more intriguing applications in the future of heat transfer is condensation in microgravity environments. Space missions will require condensers that can perform at least an order of magnitude higher than today’s technology. Constraints on the new designs include stringent weight requirements, compactness, and, of course, heat transfer performance. The condensate removal poses the biggest challenge in a microgravity environment, since gravity cannot help in the removal process. It is already known that thinner condensate film correlates to better heat transfer rates due to conduction. Four methods have been proposed for the removal of condensate in a microgravity environment; these include (1) suction through a porous wall; (2) forced vapor shear at the liquid-vapor interface; (3) centrifugal force; and (4) capillary force.


Suction at the Porous Wall

In condensation, both vapor shear and suction through a porous wall directly reduce the film thickness on the wall and, therefore, significantly increase the heat transfer. The Nusselt analysis for laminar film condensation was extended to flow inside a tube with a constant-temperature porous wall. The shear stress at the liquid-vapor interface decreases due to condensation.

See Main Article Suction at the Porous Wall

Condensate Removal by Forced Vapor Flow in Microgravity Environment

In condensation application, the main resistance to heat transfer comes from conduction across the condensate film. Therefore, thinning the condensate film is crucial for better heat transfer in a microgravity environment. This thinning is difficult for two main reasons: (1) no gravity is present to help flush the condensate away, and (2) lightweight designs are critical, so bulky pumps and blowers are not feasible. As mentioned above, one mechanism of condensate removal in a microgravity environment is vapor shear at the liquid-vapor interface.

See Main Article Condensate Removal by Forced Vapor Flow in Microgravity Environment

Condensation Removal by a Centrifugal Field

Another method to create artificial gravity involves use of a centrifugal field that is, a rotating disk. The problem studied here addresses a cooled rotating disk in a large quiescent body of pure saturated vapor, as shown in the figure on the right. The liquid forms a continuous film on the disk, and the fluid in this film will move radially outward due to the centrifugal force.

See Main Article Condensation Removal by a Centrifugal Field

Condensation Removal by Capillary Action

In a zero gravity environment, capillary action is one mechanism of condensate removal. Heat pipes fall under the category of capillary driven devices. Gas-loaded heat pipes have been applied in many diverse fields, and are useful when the temperature of a device must be held constant while a variable heat load is dissipated.

See Main Article Condensation Removal by Capillary Action


Faghri, A., and Zhang, Y., 2006, Transport Phenomena in Multiphase Systems, Elsevier, Burlington, MA

Faghri, A., Zhang, Y., and Howell, J. R., 2010, Advanced Heat and Mass Transfer, Global Digital Press, Columbia, MO.