1.2 Measurement set-up

On the basis of simulation results and available air heater capacities an experimental heat exchanger set-up with nominal heat flow of 15 kW, maximum air inflow temperature of 800 °C and dimensions of 0.5 m height,

0.05 m width and depth of 0.1 m was designed and manufactured. The sand inflow and outflow were extended by ducts of 0.5 m height to reduce air leakages. The crucial elements of the heat exchanger are two porous walls for filtration of air at the air entrance and exit.

Fig. 3 Experimental air-sand heat exchanger unit

The filtering walls have to meet various requirements including

• Abrasion resistance for continuous sand flow

• Thermal stability up to 800 °C

• Low pressure drop

In view of the two requirements mentioned first, recrystallized silicon carbide (RSiC) was chosen as wall material.

For calculation of heat transfer, heat losses and blower energy demand volume flows, air pressure drop and air and sand temperatures were measured at different positions.