18 May 2017
Owing to fossil fuel depletion, global warming, and other critical environmental issues, a conscious and efficient use of energy is required. In Japan, the manufacturing industry accounts for 40% of the national energy consumption. Moreover, factories produce a large amount of hot water at a temperature of approximately 100 °C, which cannot be directly used and, hence, is rejected to the atmosphere. However, by using absorption heat transformers, this exhaust heat can be utilized effectively. Absorption heat transformers can increase temperature by using the heat released inside its absorber. A conventional single-stage absorption heat transformer can use hot water at 90 °C to generate steam at 120 °C. However, the manufacturing industry usually demands a large amount of steam at a temperature of 160–180 °C. Therefore, a multistage configuration is needed to obtain temperatures up to 180 °C. Owing to the complexity of these systems, their performance characterization is difficult and as yet incomplete.
In this research, the performance of a double-lift heat transformer is evaluated by conducting a parameter study of the volume flow rate of cooling water. The experiment was conducted using test equipment that produced a 14 kW heat output. Using cooling water at a temperature from 20–30 °C, saturated vapor at 180 °C was generated from hot water at a temperature below 100 °C. With cooling water flows from 60 to 140 L/min, the COP didn’t change and steam generation rate increased as the flow rate of the cooling water increased.