Evaporation and Drying: Concentration and drying of liquid foods – evaporators, tray, drum and spray dryers; osmotic dehydration and freeze drying; hydrothermal treatments; drying and milling of cereals, pulses and oilseeds; drying kinetics; psychrometry – properties of air-water vapor mixture.
Air-water vapour mixture at 1 atmosphere pressure has 0.035 kg water vapour (kg dry air)⁻¹ and dry-bulb temperature of 37°C. Universal gas constant = 8.314 kJ (kg mole K)⁻¹. The humid volume (m³ (kg dry air)⁻¹) (rounded to 3 decimals) is ______.
Official Answer Key:
0.920 to 0.930
Step-by-Step Solution & Explanation
Standard psychrometric humid-volume relation (SI units):
vh = (2.83×10⁻³ + 4.56×10⁻³ × W) × T, with W in kg water/kg dry air and T in Kelvin.
T = 37 + 273.15 = 310.15 K; W = 0.035.
vh = (0.00283 + 0.00456×0.035) × 310.15 = (0.00283 + 0.0001596) × 310.15 = 0.0029896 × 310.15 = 0.9273 ≈ 0.927 m³/kg dry air. Answer: within 0.920–0.930.
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