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IV. Oil the Passage of Heat between Metal Surfaces and Liquids in contact ivith them. 
By T. E. Stanton, M.Sc., Assistant Lecturer in Engineering at 
University College^ Liverqwol. 
Communicated by Professor Osborne Reynolds, F.R.S. 
Received April 7 ,—Read May 13, 1897. 
Lnt7'oduction. 
The determination of tlie rate of transmission of heat from the surface of a heated 
metal to water in contact with it, or from hot water to a colder surface, is a problem 
of some difficulty, but is of such great importance in the theory of boilers and surface 
condensers, that further investigation would seem to be justified, especially as, 
although the theory of the subject has been much studied, yet owing to practical 
difficulties, the constants involved, so far as the author is aware, have not been 
definitely determined for cases which occur in practice.* 
Peclet’s experiments on the rate of transmission of heat from ivater to watei' across 
a metal plate,t throw much light on the question. His experiments were made to 
determine the thermal conductivities of various metals by measuring the heat passed 
through a metal plate, one side ol which was exposed to steam and the other to 
water which was kept agitated by a stirrer. In these experiments, Peclet found 
that the heat transmitted was sensibly independent of the nature and thickness of 
the metal used, the conclusion being that on each side of the plate there was a film 
of water tlirough which the heat was transmitted by conduction, and that compared 
to these, the thermal resistance of the plate was small. 
This difficulty was overcome by an arrangement consisting of revolving brushes in 
contact with each side of the plate, so as to prevent the formation of a film on the 
su)-faces, and by keeping the water in a violent state of agitation. In this way it 
was possible to keep the surfaces of the plate at the same temperature as the water 
in contact with them, and the conductivities of metals determined by this method 
agree with carefully determined conductivities obtained by other methods. 
Peclet further pointed out, that before the brushes were used to prevent the 
* Rankine’s ‘ Steam Engine,’ p. 266. 
t ‘ Traite de la Clialenr,’ p. 388. 
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16.9.97 
