Analysis of heat transfer flow rate on wall of coffee roaster machine made by stainless steel ceramic coated

Coffee Roasting process is part that change green beans into roast beans. This research identifies the effect of material roaster on heat transfer flow rate. The research was conducted experimentally using a ceramic coated roaster designed in 2 layers, the first layer is stainless steel which radiation occurs when contact with fire, conduction occurs in stainless steel when contact with ceramic, and convection occurs in ceramic with air and air with coffee beans. The experiment begins by inserting coffee beans into roaster for 10 minutes, obtained the initial temperature and time of combustion chamber, turning point, first crack, and end. First crack time of ceramic coated is 4.47 minutes and stainless steel is 5.39 minutes. Temperatures of turning point in ceramic coated at 84.7°C and stainless steel at 88°C. Result of temperature differences processed using Fourier’s Law and Log Mean Temperature Difference (LMTD) thus obtained heat transfer rate. Differences in coffee roaster materials also affect the roasting rate of coffee beans. Results of roasting classification used Red Green Blue (RGB) method on ceramic coated have a dark bean color while stainless steel has a medium bean color. Based on research data it can be concluded that ceramic coated roaster material has a higher heat transfer rate than stainless steel roaster, so the efficiency when roasting with ceramic coated roaster is higher.