UI Steam Plant Boiler AnalysisMICHAEL CLARK BRIAN KISLING

COLIN SOWARDS VINCE SCHWARTZ

Goals•Synthesize given information

•Simplify the problem into reasonable terms/ideas

•Apply reasonable assumptions

•Keep records of all calculations

•Find Overall Heat Transfer Coefficient

•Find Heat Rate

•Assess possible performance improving options

Our Initial Model

T_in = 266 F x_in = 0P = 164.7 psiam_dot = 40800 lbm/hr

T_out = 365.9 Fx_out = 1

= 39,200,000 Btu/hr

Assumptions•Model the water/steam as pure (negate impurities)

•Flue Gas modeled as Air

•Steady State

•Boiler modeled as an adiabatic heat exchanger

•All pipes are equal diameter and have equal amounts of fouling on them

•Crossflow

Finding the Initial Q-ValueUse EES to calculate enthalpies

eq. 11.7a

= 39.2 MMBtu

Finding the T_inf-Valueeq. 11.6a

Setting the q’s equal to each other, and solving for the mass flow rate of the flue gas, the flue gas temperature can be backed out using the EES function call.

Analysis of the Pipes in the Boiler•1764 pipes• D_outside = 1.5 in• D_inside = 1.25 in• Mild steel

•Cross flow

•7 pipes per side

•Thermal Circuit

T_inf h_inf

Find the Convective Heat Transfer Coeff. (Outside & Inside)

Assume a constant pipe surface temperature

Find Necessary Pi-groups◦ Reynolds◦ Nusselt◦ Prandtl

eq. 7.53

(Laminar Flow) eq. 8.55

Thermal Circuit

Final AssessmentInitial boiler efficiency was thought to be around 76-78%

Our calculations put the boiler at a 77.8% efficiency

Overall Heat Transfer Coefficient;◦ U = 5.009 [Btu/hr-ft^2-R]

Rate of Heat Transfer◦ Q = 50.36 [MMBtu/hr]

Recommendations Replace the whole thing?

◦ NOPE◦ Too expensive◦ Would only improve the efficiency a minimal amount

Average commercial boilers tend to hover around 70% - 85% efficiency◦ Expensive boiler component additions would only

minimally increase overall efficiency

B.E.T Tube Cleaners◦ Increase boiler efficiency from 6% - 20%◦ Uses hourly compressed air/steam jets to clean pipes

Credit: fuelefficiencyllc.com

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