Heat Exchanger Tube Pressure Drop Calculation, Online Calculator

Intube Pressure Drop




The intube pressure drop may be calculated by any number of methods available today, but the following procedures should give sufficient results for heater design. The pressure loss in heater tubes and fittings is normally calculated by first converting the fittings to an equivalent length of pipe. Then the average properties for a segment of piping and fittings can be used to calculate a pressure drop per foot to apply to the overall equivalent length. This pressure drop per foot value can be improved by correcting it for inlet and outlet specific volumes.






Friction Loss:







D_p = 0.00517/d_i*G²*V_lm*F*L_equiv


Where,

Dp = Pressure drop, psi

di = Inside diameter of tube, in

G = Mass velocity of fluid, lb/sec-ft2

Vlm = Log mean specific volume correction

F = Fanning friction factor

Lequiv = Equivalent length of pipe run, ft

And,









V_lm = (V₂-V₁)/ln(V₂/V₁)


For single phase flow,

V1 = Specific volume at start of run, ft3/lb

V2 = Specific volume at end of run, ft3/lb

For mixed phase flow,









V_i = 10.73*(T_f/(P_v*MW_v)*V_frac+(1-V_frac)/r_l


Where,

Vi = Specific volume at point, ft3/lb

Tf = Fluid temperature, °R

Pv = Press. of fluid at point, psia

MWv = Molecular weight of vapor

Vfrac = Weight fraction of vapor %/100

rl = Density of liquid, lb/ft3

Fanning Friction Factor:




The Moody friction factor, for a non-laminar flow, may be calculated by using the Colebrook equation relating the friction factor to the Reynolds number and relative roughness. And the Fanning friction factor is 1/4 the Moody factor. For a clean pipe or tube, the relative roughness value for an inside diameter given in inches is normally 0.0018 inch.




With this, we can calculate the factor,

Reynolds number =
Inside Diameter, inches =

Friction factor, F:

Equivalent Length Of Return Bends:




The equivalent length of a return bend may be obtained from the following curves based on Maxwell table and can be corrected using the Reynolds number correction factor.







L_equiv = Fact_Nre*L_rb


Where,

FactNre = Reynolds number correction

Lrb = Equivalent length of return bend, ft

Return Bend Equivalent Length:

Reynolds Correction:

Where,

G = Mass velocity, lb/sec-ft2

Di = Inside tube diameter, in

Visc = Viscosity, cp

Now that we have all the details described, we can calculate the pressure drop for some typical heater coils.

Coil Data
Tube inside dia., in:	Pipe straight length, ft:
Bend radius, in:	Number of returns:
Process Data
Mass vel., lb/sec-ft2:	Viscosity, cp:
Spec. vol. at start, ft3/lb:	Spec. vol. at end, ft3/lb:

 Pressure Drop, psi:

Online Heat Transfer Coefficient Calculator

Heat Transfer Coefficients


The inside film coefficient needed for the thermal calculations may be estimated by several different methods. The API RP530, Appendix C provides the following methods,

For liquid flow with R_e =>10,000,




h_l = 0.023(k/d_i)R_e^0.8*P_r^0.33(m_b/m_w)^0.14

And for vapor flow with R_e =>15,000,




h_v = 0.021(k/d_i)R_e^0.8*P_r^0.4(T_b/T_w)^0.5

Where the Reynolds number is,




R_e = d_i*G/m_b

And the Prandtl number is,




P_r = C_p*m_b/k

Where,

hl = Heat transfer coefficient, liquid phase, Btu/hr-ft2-°F

k = Thermal conductivity, Btu/hr-ft-°F

di = Inside diameter of tube, ft

mb = Absolute viscosity at bulk temperature, lb/ft-hr

mw = Absolute viscosity at wall temperature, lb/ft-hr

hv = Heat transfer coefficient, vapor phase, Btu/hr-ft2-°F

Tb = Bulk temperature of vapor, °R

Tw = Wall Temperature of vapor, °R

G = Mass flow of fluid, lb/hr-ft2

Cp = Heat capacity of fluid at bulk temperature, Btu/lb-°F

For two-phase flow,



h_tp = h_lW_l + h_vW_v

Where,

htp = Heat transfer coefficient, two-phase, Btu/hr-ft2-°F

Wl = Weight fraction of liquid

Wv = Weight fraction of vapor

The following script will allow us to try these formulas out using our browser.

Tube diameter, in:		Mass flow, lb/hr-ft2:
Percent vapor, %:		Bulk Temp., °F:
Liquid Properties		Vapor Properties
Thermal cond., Btu/hr-ft-°F:		Thermal cond., Btu/hr-ft-°F:
Visc. bulk, lb/ft-hr:		Visc. bulk, lb/ft-hr:
Spec. Heat, Btu/lb-°F:		Spec. Heat, Btu/lb-°F:
Visc. @ wall, lb/ft-hr:		Temp. @ wall, °F:

h_l Coefficient, Btu/hr-ft²-°F:


h_v Coefficient, Btu/hr-ft²-°F:


h_tp Coefficient, Btu/hr-ft²-°F:


Reynolds number:LiquidVapor

It should be stressed at this time, that there are many ways to calculate the inside heat transfer coefficient, and a lot of care should be taken in the procedure selected for use in heater design. Other methods, such as HTRI, Maxwell, Dittus-Boelzer, or others may be more appropriate for a particular heater design.

Heat Loss Calculations and System Design

Heat Loss Calculations and System Design


Note: Urecon offers a complete computer assisted engineering service providing such information as: heat loss, time to freeze, fluid outlet temperature, minimum flow rates, tracing wattage required, heat gain, etc., all based on the specific requirements of each project. Basic information needed for typical heat trace design includes: project name/location; minimum ambient temperature; above and/or below ground; depth of bury if applicable; core pipe material and diameter; pipe length per circuit; insulation thickness; required maintain temperature; flow direction for sensor positioning; power point location (one or both ends, middle etc.); voltage available.


Contact Urecon for more info and help with custom design/calculations.


It is recommended that a safety factor of 10 to 25% be added to allow for such field conditions as voltage drop, under voltage condition, etc.

Heat Flow Chart Watts/ft/hr/100°F T⁽²⁾

Dia.(1)	Urethane Insulation Thickness
	25 mm (1 in)	40 mm (1½ in)	50 mm (2 in)	63 mm (2½ in)	75 mm (3 in)
1	1.8	1.4	1.2	1.1	1.0
2	2.9	2.2	1.8	1.6	1.4
4	4.9	3.6	2.9	2.5	2.2
6	6.9	4.9	3.9	3.3	2.9
8	8.9	6.3	4.9	4.1	3.6
10	n/a	7.6	5.9	4.9	4.2
12	n/a	9.0	6.9	5.8	4.9
14	n/a	10.4	7.9	6.5	5.6
16	n/a	n/a	8.9	7.4	6.2
18	n/a	n/a	9.9	8.3	6.9
20	n/a	n/a	10.8	9.0	7.6
22	n/a	n/a	11.8	9.9	8.3
24	n/a	n/a	12.7	10.8	9.0

Heat flow in watts per lineal foot



The table is based upon the application of the following formula:



Where:

W = Watts/ft/hr (W x 3.414 = Btu/hr)

K = Btu/ft²/hr/1°F/ft = 0.0108 for Urethane

T = temperature differential°F

D = outside diameter of insulation

d = outside diameter of pipe
Diameters for (D/d) taken as 3/1 for 1" pipe +1" insulation and is typical for all other combinations.

For other than 100°F T, divide by 100 and multiply by required T.



Formula


The heat loss for an externally traced pipe may be calculated by the following formula:




Where:

W = Watts per foot of pipe

Tm = maintained temperature°F

Ta = ambient temperature°F

Ln = natural log

Di = outside diameter of insulation (in)

Dp = outside diameter of pipe (in)

Ki = K value of insulation (BTU • in / hr • ft² •°F)

Dj = outside diameter of jacket (in)

Kj = K value of jacket (BTU • in / hr • ft² •°F)

Sf = Safety Factor

QUICK HYDRAULICS - Flowsheet Simulator and Pressure Drops

QUICK HYDRAULICS - Flowsheet Simulator and Pressure Drops
Windows 95/98/NT/2000/ME/XP



Quick Hydraulics offers a low cost alternative for flowsheet simulation, heat and mass balances and pressure drop applications. Quick Hydraulics has a wide range of application in process design. Calculations utilize an integrated component database that includes detailed properties for more than 800 components. User specified distillation curves and pseudo components are handled with a properties generation routine. Heat and mass balances as well as flash calculations are carried out automatically. The user has a choice of thermodynamic options and calculation modules to cater for most process flowsheet simulations.

Heat Exchangers - Use heat exchangers in your flowsheet simulations. Specify the number of tubes, passes etc and get the program to calculate the pressure drops. Checks on heat exchange area are also carried out.

Comprehensive fluid database and estimation technology - Quick Hydraulics contains detailed properties for over 800 components. Users can add distillation curves, pseudo components and user defined components. Equations of state include Ideal, Soave Redlich Kwong, Peng Robinson, Chao Seader and Grayson Streed. Fluids include: supercritical and other common gases, water, paraffins, olefins, dienes, naphthalenes and aromatics, sulphur containing organics, halogen containing organics, nitrogen containing organics, alcohols and phenolics, ketones and aldehydes, esters, ethers, organic acids, oxygen containing organics, inorganic acids and inorganic halogen components.

Pumps and Piping - Pipe calculations can be done as single or two phase flow, with or without heat loss. Pipe fittings, insulation and elevation changes are taken into account. Fittings can be combined to simulate manifolds based on database or user supplied resistance coefficients. Pump simulation with differential heads, discharge pressure and power is performed. User supplied pump curves can be entered.

Range of simulation modules - Flowsheet simulation is performed by graphically connecting process equipment modules. Hydraulics systems are drawn using flowsheets. The simulation modules include:

Piping, elbows and tees, reducers, valves (gate, globe, butterfly, plug), check valves, pumps, heating/cooling coils, compressors/expanders, vertical and horizontal vessels (gravity settlers), axial and radial flow packed beds, shell and tube heat exchangers, air cooler heat exchangers, fired tubular heaters, restriction orifices, relief valves, control valves, strainers, steam traps, stream modifiers, stream splitters (including flashing) and component splitters.

Piping Systems FluidFlow3 - Design and Simulation Software

Piping Systems FluidFlow3 - Design and Simulation Software

A truly original software program for the design and optimization of pipe networks, transporting compressible, incompressible, gas-liquid two phase, settling slurries or non-Newtonian fluids.

The efficient and accurate modelling of your networks is essential for the design of energy efficient, safe, reliable flow systems that are easy to operate and maintain.

This product is used successfully in many diverse industries to model new and existing systems, size pipes, select boosters, controllers and other fluid equipment.

Please take a few minutes to discover why we are best in class.

The tools within FluidFlow3 enable you to:

• Build your networks rapidly  [2 min]
• Evaluate the results and consider design alternatives  [5 min]
• Communicate your design effectively to others  [1 min]

Heat transfer capabilities are included as standard within FluidFlow. At each network element you can select from any of 3 heat transfer options (pipes have 4 options):

• Ignore Heat Loss/Gain
• Fixed Temperature Change
• Fixed Transfer Rate
• Do Heat Transfer Calculation

For pipes, the software can also calculate heat loss/gain from the pipe. Pipes can be insulated with different types of materials using any thickness. Convection, conduction and radiation losses are calculated. This means you can use FluidFlow to optimize energy use by selecting the economic insulation thickness.

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The example opposite shows the heat loss from a 1 kilometer length of uninsulated pipe.


There are over 300 QA example calculations made before each release of FluidFlow. This is one of the verification heat transfer calculation examples.





An example circuit showing 2 heat exchangers with full modelling of both the shell and tubeside. Usually modelling of one side is sufficient.

Several Pressure Loss correlations can be used including: Deleware method, using manufacturers loss data, or using a fixed pressure loss.

With the 2-phase module you can also consider condensors and evaporators.




This network, shows how FluidFlow is used by a customer to model a chilled water cooling system in a Data Centre. Modelling of what happens due to pump failures is also considered in this model.

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