A review of previous literature pertaining to the heating and cooling of viscous liquids and to the heat transfer of viscous liquids flowing in pipes was made. It was found that there was a marked lack of information on this subject. A double-pipe heat exchanger was constructed from standard iron pipe and copper tubing. The apparatus includes a circulation system so that the liquid could be re-circulated through the heat exchanger. Thermocouples were set in the heating surface wall in order that wall temperatures could be read. A series of twenty-six runs was made using water and oils of three different viscosities as the liquids being heated and cooled. These runs were made at various liquid velocities. The film coefficients and Reynold's numbers were calculated for both heating and cooling of the liquids. Curves were plotted for each liquid of Reynold's numbers versus film coefficients. It was found in all cases that the film coefficient for cooling was about 0.5 the coefficient for heating. It was also found that as the liquid approached the region of streamline flow, the slope of the plot of film coefficient versus Reynold's number changed and the film coefficient approached a constant value. An alignment chart was calculated from which the film coefficient could be read directly. This chart was so constructed that it multiplied the pipe diameter, the velocity, and the density, and divided these by the viscosity to give a value for the Reynold's number. The film coefficients corresponding to the various values of Reynold's number were then substituted on the Reynolds number scale. / M.S.