Design and Construction of Thermochemical Heat Storage Test Bench dor Automotive Thermal Management

Kurzfassung

As an implication from increasing mobility of people and goods over lands, across oceans and air, transportation demand is expected to rise continuously for the next 30 years. Until today, internal combustion powertrains still dominate current vehicle propulsion systems. Fuel shortages and CO2 emission problems have renewed concerns for higher efficiency of fuel use and eventually alternative engine propulsion methods to meet the increasing transportation needs. To improve fuel efficiency in internal combustion powertrains and hybrid vehicles, automotive thermal management has become important subject of research for the past years. One of the research goals in automotive thermal management is the storage of waste heat recovered for cabin heating, air-conditioning and improving engine warm-up during cold start. In conjunction with the project "Next Generation Car" at Institute of Technical Thermodynamics of German Aerospace Center (DLR), an automotive heating and cooling system utilizing metal hydrides and hydrogen is suggested. Waste heat recovered is stored in the form of chemical compound and can be used on-board for heating and cooling demands in summer and winter. The fundamental principle of this concept is the enthalpy change of a reversible sorption reaction between metal hydrides and hydrogen. The system consists of two connected reactors, which contain two different types of metal hydrides. The absorption of hydrogen into metal hydrides is an exothermic reaction, which produces heat output. On the other hand, desorption of hydrogen from metal hydrides is an endothermic reaction that produces cold output. In the framework of this research, a test bench is planned and constructed. To stimulate cold and heat output in summer and winter conditions using waste heat from coolant loop, -20 °C to 130 °C is defined as the temperature range in this work. Among the choices of metal hydrides present, C5 and LaNi4.85Al0.15 are chosen for both heating and cooling modes. Tube bundle heat exchanger is chosen as the reaction beds due to its large heat transfer area and performance.