Lab-scale experiment of a closed thermochemical heat storage system including honeycomb heat exchanger

摘要

A lab-scale thermochemical heat storage reactor was developed in the European project "thermal battery" to obtain information on the characteristics of a closed heat storage system, based on thermochemical reactions. The present type of storage is capable of re-using waste heat from cogeneration system to produce useful heat for space heating. The storage material used was SrBr2 center dot 6H(2)O. Due to agglomeration or gel-like problems, a structural element was introduced to enhance vapour and heat transfer. Honeycomb heat exchanger was designed and tested. 13 dehydration-hydration cycles were studied under low-temperature conditions (material temperatures < 100 degrees C) for storage. Discharging was realized at water vapour pressure of about 42 mbar. Temperature evolution inside the reactor at different times and positions, chemical conversion, thermal power and overall efficiency were analysed for the selected cycles. Experimental system thermal capacity and efficiency of 65 kWh and 0.77 are respectively obtained with about 1 kg of SrBr2 center dot 6H(2)O. Heat transfer fluid recovers heat at a short span of about 43 degrees C with an average of 22 degrees C during about 4 h, acceptable temperature for the human comfort (20 degrees C on day and 16 degrees C at night). System performances were obtained for a salt bed energy density of 213 kWh.m(3). The overall heat transfer coefficient of the honeycomb heat exchanger has an average value of 147 W m(2) K-1. Though promising results have been obtained, ameliorations need to be made, in order to make the closed thermochemical heat storage system competitive for space heating. (C) 2016 Elsevier Ltd. All rights reserved.