Abstract: The invention relates to a method and apparatus for heat exchange, especially for cooling at solid surfaces. At the solid surfaces, a locally uniform convective heat exchange is achieved. According to the invention, a sink flow is superimposed on a circular flow of a fluid in a flow chamber (1) at a surface of a heat-conducting solid wall (9) by means of a distributor, forming a vortex sink flow. The heat exchange surface of the component (9) to be cooled is at the same time the base plate (8) of a flow chamber (1).

Abstract: For the recording of local boundary-layer flow-line directions in liquid media by means of a photographic layer,(a) small reagent depots or deposits, with a volume of about 0.2 mm.sup.3, of a water-soluble substance reactive to silver ions ("chemical flow line indicators") are applied in raster fashion to the surface which is to be exposed to the flow and which surface is previously coated with a dry or swelled photographic sheet film,(b) the reagent deposits are covered with an inert layer which is soluble in the liquid flow medium,(c) the surface so prepared is exposed to the flow of an aqueous flow medium, and(d) the film is developed according to conventional means.The reagent deposits, which may be present as a paste, can contain a precipitation agent for silver ions. The deposits can be applied as a dot raster to the surface which is to be exposed to the flow (and which is coated with a photographic film) by means of screen printing or by means of a hole raster template.

Abstract: The disclosed method relates to a method for recording flow boundary layers in liquid media by photochemical means. According to the invention, surfaces which can be developed in a plane and to which a photographic film sheet is cemented are exposed under steady-state conditions to the flow of a liquid medium containing a dissolved agent reacting with the photo gelatin layer. The liquid medium may contain agents furnishing HS-ions or agents capable of dissolving silver halide or reducing silver halide. If a photographic film sheet is used, the silver ions of which are reduced to silver, the flow exposure is performed with an agent having oxidizing and dissolving action. With the method disclosed, half-tone photograms of flow boundary layers in liquids can be recorded.

Abstract: The invention relates to a method for making visible by photochemical means residual moisture distributions in photographic wet film layers subjected to a gas flow. According to the invention, a film diffusely pre-exposed is immersed in an aqueous swelling agent solution which contains either (a) a reducing agent or (b) an alkali. After being exposed to the air stream, the invisible residual moisture profile is immersed in an alcoholic solution of either (a) an alkali or (b) a reducing agent. The half-tone image produced serves for determining stationary local boundary layer thickness distributions, wall shearing stresses, material transfer coefficients and heat transfer coefficients.

Abstract: Stationary heat transfer coefficient fields are made visible by applying a swelled photographic film (original wet film) in daylight to the article to be exposed to the flow. The wet film obtained after it is exposed to a gas flow and removed from the article, is squeezed onto an unexposed dry photographic film. The separated wet copy (latent image) is seeded with reactive gas (H.sub.2 S) to make the moisture profile visible, and is developed into a wet-copy photogram (black-and-white picture), the sharp contours of which (line equidensities, isohumids) can optionally be translated into colors, corresponding to the stationary mass transfer distribution, and with which definite heat transfer coefficients can thereby be correlated.