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Can anyone answer these questions about thermal efficiency ?
A heat exchanger is rated at 10 MW and is supplied with water at 20oC. The exchanger heats the water to 100oC at which point it is turned into dry steam. The heat exchanger supplies dry steam at 2 kg/s. If the specific heat capacity of water is 4.19 KJ/kg/K and the specific latent heat of vaporisation is 2.25 MJ/kg.
Determine:
a) The thermal Energy required to heat the water from 20oC to 100oCwater
b) The Thermal Energy required to change the state of 2 kg/s of water at 100oC to steam at 100oC
c) The Total Heat supplied to change the water to steam
d) The thermal efficiency of the heat exchanger
1 Answer
- Born YesterdayLv 74 years agoFavorite Answer
(a) Q = k×m×Δt = 4.19kJ/kgC×2kg×80C = 670.4 kJ
(b) Q = k×m = 2.25MJ/kg × 2kg = 4.5MJ
(c) .6704 MJ + 4.5MJ = 5.1704 MJ
(d) Assuming 100 MJ is supplied?
Efficiency is output/input.
= 5.1704/100 ≈ 5%
