Bubble column, tube side slurry process and apparatus

A hydrocarbon synthesis process comprising reacting a gaseous mixture of hydrogen and carbon monoxide at a pressure of 1 to 100 atmospheres and a temperature of about 175.degree. C. to about 400.degree. C. in the presence of a hydrocarbon synthesis catalyst dispersed in a liquid thereby forming a slurry liquid, wherein the catalyst dispersion is disposed in a plurality of vertically arranged elongated reaction tubes having an L/D (length/diameter) of at least about 10, each tube being surrounded by a common heat transfer medium disposed within the shell of a shell and tube reactor, the heat transfer medium not being in fluid communication with the slurry liquid.