- #1
MaisieMitchell
- 6
- 3
New poster is reminded to always show their work when starting schoolwork threads
- Homework Statement
- Dry saturated steam at a temperature of 180ºC is to be produced in a
fire tube boiler from the cooling of 50 000 kg h–1 of flue gases from a
pressurised combustion process. The gases enter the tubes of the
boiler at 1600ºC and leave at 200ºC. The feed water is externally
preheated to 180ºC before entering the boiler.
The mean specific heat capacity of the flue gases is 1.15 kJ kg–1 K–1.
The latent heat of vaporisation of the water at 180ºC is 2015 kJ kg–1.
Feed water temperature = 180ºC.
The tubes within the boiler are to be 25 mm inside diameter with a
wall thickness of 3 mm. The average flue gas velocity through the
tubes to maintain the overall heat transfer coefficient value and to
minimise pressure losses is to be more than 22 m s–1 and less than
28 m s–1.
Assuming that the average density of the flue gases is 1.108 kg m–3,
calculate:
(i) the minimum and maximum number of tubes in each pass
(ii) the overall length of tubes at each of these numbers of tubes
(iii) the minimum number of tube passes in each case, if the length
of a boiler tube is to be less than 5 metres.
- Relevant Equations
- mg = n (Π/4 χ d^2 x v) x ρ (ρ is density)
Stuck with i & ii can somebody please guide me. none of my coursework material has anything similar in to help me work this one out.
