Abstract
We propose a couple of assessment-indexes on energy utilization from two viewpoints of reasonable consumption of energy resource and less environmental thermal-load. The exergy quantity in a demand, AD, is defined as a basis of the new indexes. For the assessment of energy resource, we consider the exergy quantity in consumed energy resource, AR, and propose an index of AR /AD as an exergy-balance-ratio, EBR. The absolute value of EBR is always greater than unity and the EBR being unity is the ideal system. In addition, we also consider the exergy quantity in exhaust heat, AE. We can evaluate the environmental-thermal-load from the whole system by using a ratio of (AE + AD) /AD, which we call the index as an exhaust-exergy-ratio, EER. In case of the EER being unity is no environmental thermal load from the supply system. We could judge the best system by selecting both of EBR and EER to be closest to unity, respectively. The combination of the new indexes would be a useful tool to develop or select an environmentally better system. The quantitative assessment for various thermal devices for air heating will be shown as an example.
