Experimental investigation and thermodynamic analysis of a cascaded latent heat storage system for diesel engine waste heat recovery

Abstract

There exists today worldwide concern about the best ways of using the depletable sources of energy, and of developing techniques to reduce pollution. This interest has encouraged research and development efforts in the fields of alternative energy sources, cost effective use of the exhaustible sources of energy, and the reuse of the usually wasted forms of energy. In the present work, the cascading arrangement of the phase change storage system is studied to analysis the improvement in the efficiency of the storage system during the charging and discharging processes. A charging experiment is conducted by integrating a two stage cascading thermal storage system with an internal combustion engine. The thermal performance of heat recovery heat exchanger and the storage system has been studied for the charging process of the phase change material in the thermal storage tank for various engine operating conditions. The work also deals with the use of exergy as an efficient tool to measure the quantity and quality of energy extracted from a diesel engine exhaust and stored in a phase change material based thermal storage system. This analysis provides a more realistic and meaningful assessment than the conventional energy analysis. Using actual system data, the assessment of energy and exergy saved, and the energy and exergy efficiencies are evaluated and reported. A comparison of performance has also been made through energy and exergy flow diagrams. The discharge process is analyzed with a case study and it is concluded that it is possible to improve both the energy and exergy efficiency appreciably, using the cascaded latent heat storage system, when the energy from the exhaust gas is to be stored at a high temperature. It is concluded that the cascaded arrangement with multiple phase change materials improves both the energy and exergy efficiency and the exergy analysis combined with environment and economic perspectives is the useful solution methodology for many of the energy and environment problems