Waste heat from industries such as steam power plants can be utilized to meet the world’s electricity need. However, it cannot be converted efficiently to electric power by using conventional power generation methods as opposed to a technology called Organic Rankine Cycle (ORC). ORC is one of the power plant systems that is a modification of the Rankine Cycle using organic working fluid. In this research, ORC was designed and manufactured using R-134a as working fluid and helical heat exchanger as evaporator and condenser. The design of ORC systems based on simulation using Cycle Tempo 5.0 with evaporator temperature of 90°C, condenser temperature of 10°C, inlet pressure of pump of 0.55 MPa, and inlet pressure of turbine of 0.79 MPa. The results of this study showed the length of tube evaporator and condenser of 10.61 m and 10.56 m, respectively, with system efficiency achieved at 3.8%. Based on experiment, with evaporator temperature of 95°C, condenser temperature of 10°C, inlet pressure of pump of 0.48 MPa and inlet pressure of turbine of 0.52 MPa so resulted of system efficiency of 3.33%.

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The volume of Indonesian tea exports to the European Union (EU) decreased by 43% in 2014 because of the EU setting a maximum residue limit of anthraquinone (AQ) for tea as 0.02 mg/kg. The content of AQ in tea leaves increases when there is incomplete combustion in the combustion of firewood for the energy source of withering and drying of tea leaves. This study aims to develop and test a new concept for the direct use of low-temperature geothermal energy with a heat pipe heat exchanger (HPHE) for the withering of tea leaves as a solution for energy sources free from AQ. The geothermal fluid simulators use water, which is heated by heater and flowed by a pump. The HPHE used consists of 42 heat pipes and 181 fins. The heat pipe used has a length of 700 mm with an outer diameter of 10 mm. Each fin is made of aluminum with a thickness of 0.105 mm and a size of 76 × 345 mm2. The results show that the effectiveness of the HPHE varies from 66% to 79.59%. For 100 g of fresh tea leaves, the heating energy produced ranges from 15.21 W to 45.07 W, meaning it can wither tea leaves from 80% (w.b.) to 54% (w.b.) in a variety of 11 h 56 min to only 49.6 min. The Page mathematical model is the best model to represent the behavior of the tea leaves with this HPHE system.

Organic Rankine Cycle (ORC) system is a modification of the conventional Rankine cycle to generate electricity from the utilization of low-grade temperature heat sources. Experiment on ORC systems was conducted to analyse the performance of a small scale ORC system with 1 kW capacity using R134a as working fluid. A helical type of evaporator and condenser were used as heat exchangers and a scroll type car compressor was used to generate power with variation in heat source temperatures of 75°C, 85°C, and 95°C. Turbine power is calculated theoretically based on the experimental data obtained due to the turbine was not able to rotate. This experiment results show the optimum efficiency and theoretical power of ORC is respectively 3.33% and 279.58 Watt with inlet pressure and temperature of turbine are respectively 1.25 MPa and 67.7°C.

Thermoacoustic refrigerator has emerged as one of new alternative ways of cooling. The use of this technology which converts sound energy to heat energy has not been popular despite its environmentally friendly and simple construction. A laboratory scale thermoacoustic cooling device has been constructed to conduct experiments on three different shapes of resonators that results in temperature difference occurring at its stack ends. Geometry of the device parts is one of the parameter that holds importance to its characteristic. The device applied a different shape of resonator for each experiment and record temperature data at stacks ends. The experiments were conducted with variations in resonator which are square tube, cylinder tube and tapered tube. The material of resonator is acrylic and its inner volume remains unchanged.