METAL SURFACES AND LIQUIDS IN CONTACT WITH THEM. 
85 
Case of Tixmsmission of Heat from Water to Metal. 
The theory for this case is the sarae as in the transmission of heat from the surface 
to the water, so far as the convection of the heat is concerned. It seemed jDrobable that 
the conductivity coefficients would also be the same, but on experiment this was found 
not to be so, the viscosity in this case having a much greater effect, the results of 
the experiments being that the heat transmitted was nearly inversely proportional 
to the mean viscosity of the film of liquid at the surface, so that the conductivity 
coefficient can be put in the form 
where is the mean value of P for the experiment, and 
P = 
1 + -0336 + -000221 
For this case equation (5) now takes the form 
^ _ U' ^ P2-« — To) 
dx A ’ D ' (2r)^~“ ' 
(9). 
The results of experiments made under these conditions are given in Table V., and 
the values of Jc calculated. These values do not show quite such a high degree of 
consistency as the values of Ic deduced from the other experiments, but this is 
probably due to the difficulty of working under the given conditions. Other experi¬ 
ments in which the heat flowed from water to metal were made, but always with the 
result that the heat transmitted was sensibly inversely proportional to the mean 
viscosity of the film at the surface, the deviation being never greater than 7 percent. 
The Transmission of Heat from the Jacket Water to the External Surface of the Pipe. 
During all the experiments the temperatures of the jacket water were taken, so 
that the rate of heat transmission from the jacket water to the surface of the pij^e 
could be calculated. 
It was found in this case also that the transmission of heat was sensibly inversely 
proportional to the mean viscosity of the film of w'ater at the surface of the pipe, the 
value of the conductivity coefficient being always slightly less than the mean value 
of P“^ for the film of water. 
This is shown in Table VL, in which the product in the last term is calculated on 
the assumption that the effect of velocity and range of temperature is the same as in 
the previous cases. 
It was found from these experiments on the jacket water that the value of n is 
practically the same as in the case of the pipe, the value for the jacket of No. 1 pipe 
being 1-855. 
