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A thin layer of water in a field is formed after a farmer has watered it. The ambient air conditions are: temp. 20°C and relative humidity 5%. An extract of steam tables is given below.
Neglecting the heat transfer between the water and the ground, the water temperature in the field after phase equilibrium is reached equals
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- 10.3°C
- –10.3°C
- –14.5°C
- 14.5°C
Correct Option: C
Given data:
Φ = 5% = 0.05
Tdb = 20°C
From table
At 20°C, Ps = 2.34 kPa
| Φ = | Ps |
| 0.05 = | 2.34 |
Pv =.117 k Pa By Interpolation method,
| Tdb = - 15 + | × (0.117 - .1) | 0.26 - 0.10 |
= – 15 + 0.531 = – 14.5° C
