heat exchangers complete
DESCRIPTION
heat exchangerTRANSCRIPT
HEAT EXCHANGERSHEAT EXCHANGERS
HEAT EXCHANGER HEAT EXCHANGER SO FAR……….. SO FAR………..
Types of Heat Exchanger Application of Heat Exchanger Heat Exchanger Design
Consideration Factors Affecting Design Heat Transfer Co-efficient Temperature Approach
SCOPE OF SCOPE OF PRESENTATIONPRESENTATION
Fouling in Heat Exchanger Pressure Drop Design consideration Fluid Allocation Calculation of Shell and Tube Heat
exchanger
FOULING IN HEAT FOULING IN HEAT EXCHANGEREXCHANGER
“Fouling” is a general term that includes any kind of deposition of extraneous material that appears upon the heat transfer area during the lifetime of the heat exchanger
TYPES OF FOULINGPrecipitation foulingParticulate foulingChemical reaction foulingCorrosion foulingBiological fouling
MATERIALS SELECTION MATERIALS SELECTION FOR FOULING SERVICESFOR FOULING SERVICES
Copper-bearing alloy such as
90-10 copper- nickel
70-30 copper- nickel
83-17-0.4 copper-nickel-chromium
PRESSURE DROPPRESSURE DROP
Pressure drop in Heat Exchanger is made up of three losses
Frictional loss due to flow
Loss due to changes in direction
Losses due to sudden expansion or
contraction
DESIGN CONSIDERATIONDESIGN CONSIDERATION
Number of shells Tube selection
TypeLengthDiameter and Wall Thickness
Type of HeadStationary HeadRear Head
Tube Layout Baffles
Tube Layouts
There are four types of tube layouts
Square (900)
Rotated square (450)
Triangular (300)
Rotated triangular
(600)
PITCH LAYOUTPITCH LAYOUT
30º
PT
90º
60º
45º
PT
TUBE SPACING LAYOUTS TUBE SPACING LAYOUTS FOR TUBE SHEETFOR TUBE SHEET
BAFFLESBAFFLES
Two types of baffles are used in shell and
tube heat exchanger
Transverse Baffles
Longitudinal Baffles
DISC AND DOUGHNUT DISC AND DOUGHNUT BAFFLESBAFFLES
TUBESTUBES
Number of Tubes:
It depends on fluid flow rates and the available pressure drop
No. of tubes selected such that the tube side velocity is 0.9 to 2.4 m/sec and shell side velocity is 0.6 to 1.5 m/sec
Lower velocity limits corresponds to limiting the fouling and upper velocity limits corresponds to erosion
Tube side passes:
Almost all cases we have even number of tube side passes owing to factors of stress etc mechanical design for odd passes is difficult
Large number of tubes increase fluid velocity, heat transfer coefficient and minimize fouling. However this leads to increase in pressure drop and need for more pumping
SHELL AND TUBE HEAT SHELL AND TUBE HEAT EXCHANGEREXCHANGER
FLUID ALLOCATIONFLUID ALLOCATION
Tube side is preferred under these circumstances
Fluid which are prone to foulCorrosive fluidsToxic fluids to increase containmentStream with low flow rates to obtain
increase velocities and turbulenceHigh pressure streams
Material of construction
Material Typical service
Aluminium and austenic chromium-nickel steel
T < -100 0C
Carbon steel -100 < T < 0 0C
Refractory- lined steel
0 < T < 500 0C
Non-Corrosive service
Corrosive ServiceCorrosive Service
Material Typical service
Carbon Steel Mildly corrosive fluids
Ferritic chromium steel
Tubes for moderately corrosive service
Aluminium Mildly corrosive fluids
High nickel-chromium-molybdenum alloys
Resistant to mineral acids
THE CALCULATION OF SHELL AND TUBE HEAT EXCHANGER
Shell Side Film Co-efficient
• ho.De/k = 0.36 (De.G/μ)0.55 (Cp.μ/k)1/3 (μ/μw) 0.14
Shell Side Equivalent Diameter De = Wetted Perimeter 4 x free Area For square pitch De = 4 (PT
2 – πdo2/4)
πdo
For triangular pitch De = 4 (0.43 PT
2 – πdo2/8)
πdo/2
Tube side Heat Transfer Co-efficient Dittus-Bolter equation Sieder-Tate equation
Overall Heat Transfer Co-efficient 1 = 1 + 1 do + xw. do + Ro + Ri diUo ho hi di kw. dm do
True Temperature Difference
Q = U.A. tm = W.C.(T1-T2) = w.c. (t2-t1) tm = True Temperature tm = LMTD x FT
FT = correction factor
Pressure Drop in Shell & Tube Heat Exchanger
Tube Side P = 4.f L u2ρ
2df = 0.079 Re-0.25
f = 0.046 Re-0.2
Shell Side P = f Gs2 Ds L
2 x 106 de B S
f = 1.87 Re-0.2
Where,
Gs = shell side mass velocityDs = shell diameterde = equivalent diameterL = tube lengthS = baffle spacing
Bundle DiameterDb = do (N/k)1/n
Db = bundle diameterN =total no. of tubesdo = Outside diameter of tube
THANK YOUTHANK YOU