## Materials and Methods
### Operating Conditions and Energy Performance  
For the fixed-bed dryer, samples of cassava grits were collected just before starting the drying process and at the end of it. Both, wet and dried samples were collected following a three by three grid pattern, as shown in Figure 2(a). For the pneumatic dryer, samples of wet and dried cassava grits were collected at the dryer's feeder, and at the cyclone's solid outlet (Figure 2(b)), respectively, at 0.75-h intervals. At this dryer, sample collection started only after a steady-state condition was achieved, determined by observing the temperature, \(T_{\text{ex}}\) (\({}^{\circ}\)C), and relative humidity, \(\Psi_{\text{ex}}\) (\(\%_{\text{rh}}\)), trends at the cyclone air outlet, measured with a digital humidity-temperature probe (HC2A-S3, Rotronic, Bassersdorf, Switzerland). On average, a steady-state condition was achieved 0.75 \(\pm\) 0.01 h after the operator has started loading wet grits into the dryer. Samples collected from both dryers were placed on an airtight container and taken to the laboratory of the Food Research Institute (FRI) of the Council for Scientific and Industrial Research in Accra, for moisture content measurement. The moisture content was determined gravimetrically according to the AOAC method 935.29 [39]. Samples were dried for 3 h at 103 \(\pm\) 1 \({}^{\circ}\)C, using a convection oven (NE9-112S; Clifton, Weston-super-Mare, UK). On both dryers, the mass flow rate of the wet cassava grits, \(\dot{m}_{\text{ws}}\) (kg h\({}^{-1}\)), and the mass flow rate of the dried cassava grits, \(\dot{m}_{\text{ds}}\) (kg h\({}^{-1}\)) were measured using a digital balance (AWB120; Avery Weigh-Tronix, Smethwick, UK) and a chronometer. In addition, for the fixed-bed dryer, loading and unloading periods were measured with a chronometer. On both dryers, the temperature of the dried cassava grits, \(T_{\text{ds}}\) (\({}^{\circ}\)C) were measured with a resistance thermometer (PT100; Rotronic). For the fixed-bed dryer, measurements were made at the end of the drying process, using a six by six grid pattern. For the pneumatic dryer, temperature was continuously measured and recorded at a 1-min interval using a wireless data-logger (LOG-HC2-RC; Rotronic) with the thermometer placed at the material leaving the cyclone's solid outlet. On both dryers, the temperature of the air at the dryer inlet, \(T_{1}\) (\({}^{\circ}\)C), was measured with a resistance thermometer (PT100; Rotronic). For the fixed-bed dryer, the sensor was placed at the duct  
Figure 3: Measurements made at the dryers: (**a**) top-view of the fixed-bed dryer and (**b**) side-view of the pneumatic dryer (\(T\), temperature; \(\Psi\), relative humidity; \(P\), pressure; \(v\), air velocity; \(\dot{m}\), mass flow rate; \(X\), moisture content). that connects the fan to the dryer bed (Figure 3a). For the pneumatic dryer, the sensor was placed at the duct after the heat exchanger before the feeding point (Figure 3b). On both dryers, the sensors were connected to a wireless data-logger (LOG-HC2-RC; Rotronic) and temperature values were recorded at 1-min interval. Air static-pressure at the dryer inlet, \(P_{1}\) (Pa), was also measured at these locations using a manometer (922; Fluke, Norwich, UK). Ambient relative humidity, \(\Psi_{\mathrm{amb}}\) (\(\%_{\mathrm{orh}}\)), and ambient air temperature, \(T_{\mathrm{amb}}\) (\({}^{\circ}\)C), were measured with a digital humidity-temperature probe (HC2A-S3, Rotronic), connected to a wireless data logger (LOG-HC2-RC; Rotronic) recording values at 1-min intervals. The barometric pressure of the ambient air, \(P_{\mathrm{amb}}\) (Pa), was measured with a digital barometer (GBP 3300, Greisinger, Regenstauf, Germany) and recorded manually at 30 min intervals. Air velocity at the heat exchanger inlet, \(v_{\mathrm{amb}}\) (m s\({}^{-1}\)) was measured with a pitot tube connected to a manometer (922; Fluke).