Utilization the Heat Pipe Heat Exchanger Techniques at Low Enthalpy Geothermal Energy to Coffee Drying Process

Abstract

Coffee is one of Indonesia’s main commodity which competes in international market. However, Indonesia’s coffee production still faces some problems. One of the main problems is for the drying process. Moisture contents of coffee need to be reduced to 12%. All this time, most coffee producers use conventional method by using heat source from sunlight. However, uncertain weathers become one of the factors which slows down the drying process. Therefore, the purpose of this research is to find and utilize an alternative energy to solve the drying process problem. One of energy sources which is possible to be used for those criteria is geothermal energy especially with low enthalpy that usually is used for daily activities such as bathing, cooking, and warming houses. In this research, Heat Pipe Heat Exchanger (HPHE) which consists of 42 straight heat pipes with staggered configuration is used for utilizing geothermal energy. The heat pipe has a length of 700 mm OD 10 mm with filling ratio of 50% and added by 181 pcs of aluminum with dimension size of 76 x 345 x 0.105 mm as a fin. Geothermal fluid is simulated by water that heated by 9000 watt heater. Temperature of hot water with range of 50, 60, and 70˚C and air speed of 0.2, 0.4, 0.6 m/s are variations for the experiment. The result shows that the highest effectiveness of HPHE is 78.8% with the temperature of 70˚C and 0.2 m/s air speed while the lowest effectiveness is 68.8% with the temperature of 50˚C and 0.6 m/s air speed. Other than that, the drying process with the temperature of 70˚C and 0.6 m/s air speed is the fastest while the slowest is at 50˚C and air speed of 0.2 m/s. This result proves that increasing the temperature and air speed lead to the less time needed for the drying process.