Air cooler sizing and rating (ht.air_cooler)¶
- ht.air_cooler.Ft_aircooler(Thi, Tho, Tci, Tco, Ntp=1, rows=1)[source]¶
Calculates log-mean temperature difference correction factor for a crossflow heat exchanger, as in an Air Cooler. Method presented in [1], fit to other’s nonexplicit work. Error is < 0.1%. Requires number of rows and tube passes as well as stream temperatures.
\[F_T = 1 - \sum_{i=1}^m \sum_{k=1}^n a_{i,k}(1-r_{1,m})^k\sin(2i\arctan R) \]\[R = \frac{T_{hi} - T_{ho}}{T_{co}-T_{ci}} \]\[r_{1,m} = \frac{\Delta T_{lm}}{T_{hi} - T_{ci}} \]- Parameters
- Thifloat
Temperature of hot fluid in [K]
- Thofloat
Temperature of hot fluid out [K]
- Tcifloat
Temperature of cold fluid in [K]
- Tcofloat
Temperature of cold fluid out [K]
- Ntpint
Number of passes the tubeside fluid will flow through [-]
- rowsint
Number of rows of tubes [-]
- Returns
- Ftfloat
Log-mean temperature difference correction factor [-]
Notes
This equation assumes that the hot fluid is tubeside, as in the case of air coolers. The model is not symmetric, so ensure to switch around the inputs if using this function for other purposes.
This equation appears in [1]. It has been verified. For some cases, approximations are made to match coefficients with the number of tube passes and rows provided. 16 coefficients are used for each case; 8 cases are considered:
1 row 1 pass
2 rows 1 pass
2 rows 2 passes
3 rows 1 pass
3 rows 3 passes
4 rows 1 pass
4 rows 2 passes
4 rows 4 passes
References
- 1(1,2)
Roetzel, W., and F. J. L. Nicole. “Mean Temperature Difference for Heat Exchanger Design-A General Approximate Explicit Equation.” Journal of Heat Transfer 97, no. 1 (February 1, 1975): 5-8. doi:10.1115/1.3450288
Examples
>>> Ft_aircooler(Thi=125., Tho=45., Tci=25., Tco=95., Ntp=1, rows=4) 0.550509360409
- ht.air_cooler.air_cooler_noise_GPSA(tip_speed, power)[source]¶
Calculates the noise generated by an air cooler bay with one fan according to the GPSA handbook [1].
\[\text{PWL[dB(A)]} = 56 + 30\log_{10}\left( \frac{\text{tip speed} [m/min]}{304.8 [m/min]}\right) + 10\log_{10}( \text{power}[hp]) \]- Parameters
- tip_speedfloat
Tip speed of the air cooler fan blades, [m/s]
- powerfloat
Shaft power of single fan motor, [W]
- Returns
- noisefloat
Sound pressure level at 1 m from source, [dB(A)]
Notes
Internal units are in m/minute, and hp.
References
- 1(1,2)
GPSA. “Engineering Data Book, SI.” 13th edition. Gas Processors Suppliers Association (2012).
Examples
Example problem from GPSA [1].
>>> air_cooler_noise_GPSA(tip_speed=3177/minute, power=25.1*hp) 100.5368047795
- ht.air_cooler.air_cooler_noise_Mukherjee(tip_speed, power, fan_diameter, induced=False)[source]¶
Calculates the noise generated by an air cooler bay with one fan according to [1].
\[\text{SPL[dB(A)]} = 46 + 30\log_{10}\text{(tip speed)}[m/s] + 10\log_{10}( \text{power}[hp]) - 20 \log_{10}(D_{fan}) \]- Parameters
- tip_speedfloat
Tip speed of the air cooler fan blades, [m/s]
- powerfloat
Shaft power of single fan motor, [W]
- fan_diameterfloat
Diameter of air cooler fan, [m]
- inducedbool
Whether the air cooler is forced air (False) or induced air (True), [-]
- Returns
- noisefloat
Sound pressure level at 1 m from source (p0=2E-5 Pa), [dB(A)]
Notes
Internal units are in m/minute, hp, and m.
If the air cooler is induced, the sound pressure level is reduced by 3 dB.
References
- 1
Mukherjee, R., and Geoffrey Hewitt. Practical Thermal Design of Air-Cooled Heat Exchangers. New York: Begell House Publishers Inc.,U.S., 2007.
Examples
>>> air_cooler_noise_Mukherjee(tip_speed=3177/minute, power=25.1*hp, fan_diameter=4.267) 99.1102632909
- ht.air_cooler.dP_ESDU_high_fin(m, A_min, A_increase, flow_area_contraction_ratio, tube_diameter, pitch_parallel, pitch_normal, tube_rows, rho, mu)[source]¶
Calculates the air-side pressure drop for a high-finned tube bank according to the ESDU [1] method, as described in [2]. This includes the effects of friction of the fin, and acceleration.
\[\Delta P = (K_{acc} + n_{rows} K_{f}) \frac{1}{2}\rho v_{max}^2 \]\[K_{f} = 4.567 Re_D^{-0.242} \left(\frac{A}{A_{tube,only}} \right)^{0.504} \left(\frac{p_1}{D_o}\right)^{-0.376} \left(\frac{p_2}{D_{o}}\right)^{-0.546} \]\[K_{acc} = 1 + \text{(flow area contraction ratio)}^2 \]- Parameters
- mfloat
Mass flow rate of air across the tube bank, [kg/s]
- A_minfloat
Minimum air flow area, [m^2]
- A_increasefloat
Ratio of actual surface area to bare tube surface area \(A_{increase} = \frac{A_{tube}}{A_{bare, total/tube}}\), [-]
- flow_area_contraction_ratiofloat
Ratio of A_min to A_face, [-]
- tube_diameterfloat
Diameter of the bare tube, [m]
- pitch_parallelfloat
Distance between tube center along a line parallel to the flow; has been called longitudinal pitch, pp, s2, SL, and p2, [m]
- pitch_normalfloat
Distance between tube centers in a line 90° to the line of flow; has been called the transverse pitch, pn, s1, ST, and p1, [m]
- tube_rowsint
Number of tube rows per bundle, [-]
- rhofloat
Average (bulk) density of air across the tube bank, [kg/m^3]
- mufloat
Average (bulk) viscosity of air across the tube bank, [Pa*s]
- Returns
- dPfloat
Overall pressure drop across the finned tube bank, [Pa]
Notes
- The data used by the ESDU covered:
fin density 4 to 11/inch
tube outer diameters 3/8 to 2 inches
fin heights 1/3 to 5/8 inches
fin tip to fin root diameters 1.2 to 2.4
Reynolds numbers 5000 to 50000
[1] claims 72% of experimental points were within 10% of the results of the correlation.
The Reynolds number used in this equation is that based on V_max, calculated using the minimum flow area.
References
- 1(1,2)
“High-Fin Staggered Tube Banks: Heat Transfer and Pressure Drop for Turbulent Single Phase Gas Flow.” ESDU (October 1, 1986).
- 2
Hewitt, G. L. Shires T. Reg Bott G. F., George L. Shires, and T. R. Bott. Process Heat Transfer. 1E. Boca Raton: CRC Press, 1994.
Examples
>>> AC = AirCooledExchanger(tube_rows=4, tube_passes=4, tubes_per_row=8, tube_length=0.5, ... tube_diameter=0.0164, fin_thickness=0.001, fin_density=1/0.003, ... pitch_normal=0.0313, pitch_parallel=0.0271, fin_height=0.0041, corbels=True)
>>> dP_ESDU_high_fin(m=0.914, A_min=AC.A_min, A_increase=AC.A_increase, flow_area_contraction_ratio=AC.flow_area_contraction_ratio, tube_diameter=AC.tube_diameter, pitch_parallel=AC.pitch_parallel, pitch_normal=AC.pitch_normal, tube_rows=AC.tube_rows, rho=1.217, mu=0.000018) 485.630768779
- ht.air_cooler.dP_ESDU_low_fin(m, A_min, A_increase, flow_area_contraction_ratio, tube_diameter, fin_height, bare_length, pitch_parallel, pitch_normal, tube_rows, rho, mu)[source]¶
Calculates the air-side pressure drop for a low-finned tube bank according to the ESDU [1] method, as described in [2]. This includes the effects of friction of the fin, and acceleration.
\[\Delta P = (K_{acc} + n_{rows} K_{f}) \frac{1}{2}\rho v_{max}^2 \]\[K_{f} = 4.71 Re_D^{-0.286} \left(\frac{\text{fin height}} {\text{bare length}}\right)^{0.51} \left(\frac{p_1 - D_o}{p_2 - D_o}\right)^{0.536} \left(\frac{D_o}{p_1 - D_o}\right)^{0.36} \]\[K_{acc} = 1 + \text{(flow area contraction ratio)}^2 \]- Parameters
- mfloat
Mass flow rate of air across the tube bank, [kg/s]
- A_minfloat
Minimum air flow area, [m^2]
- A_increasefloat
Ratio of actual surface area to bare tube surface area \(A_{increase} = \frac{A_{tube}}{A_{bare, total/tube}}\), [-]
- flow_area_contraction_ratiofloat
Ratio of A_min to A_face, [-]
- tube_diameterfloat
Diameter of the bare tube, [m]
- fin_heightfloat
Height above bare tube of the tube fins, [m]
- bare_lengthfloat
Length of bare tube between two fins \(\text{bare length} = \text{fin interval} - t_{fin}\), [m]
- pitch_parallelfloat
Distance between tube center along a line parallel to the flow; has been called longitudinal pitch, pp, s2, SL, and p2, [m]
- pitch_normalfloat
Distance between tube centers in a line 90° to the line of flow; has been called the transverse pitch, pn, s1, ST, and p1, [m]
- tube_rowsint
Number of tube rows per bundle, [-]
- rhofloat
Average (bulk) density of air across the tube bank, [kg/m^3]
- mufloat
Average (bulk) viscosity of air across the tube bank, [Pa*s]
- Returns
- dPfloat
Overall pressure drop across the finned tube bank, [Pa]
Notes
Low fins are fins which were formed on the tube outside wall, normally by the cold rolling process. The data used by the ESDU covered:
fin density 11 to 32/inch
tube outer diameters 0.5 to 1.25 inches
fin heights 0.03 to 0.1 inches
Reynolds numbers 1000 to 80000
[1] compared this correlation with 81 results and obtained a standard deviation of 7.7%.
The Reynolds number used in this equation is that based on V_max, calculated using the minimum flow area.
References
- 1(1,2)
“High-Fin Staggered Tube Banks: Heat Transfer and Pressure Drop for Turbulent Single Phase Gas Flow.” ESDU (October 1, 1986).
- 2
Hewitt, G. L. Shires T. Reg Bott G. F., George L. Shires, and T. R. Bott. Process Heat Transfer. 1E. Boca Raton: CRC Press, 1994.
Examples
>>> AC = AirCooledExchanger(tube_rows=4, tube_passes=4, tubes_per_row=8, tube_length=0.5, ... tube_diameter=0.0164, fin_thickness=0.001, fin_density=1/0.003, ... pitch_normal=0.0313, pitch_parallel=0.0271, fin_height=0.0041, corbels=True)
>>> dP_ESDU_low_fin(m=0.914, A_min=AC.A_min, A_increase=AC.A_increase, ... flow_area_contraction_ratio=AC.flow_area_contraction_ratio, ... tube_diameter=AC.tube_diameter, fin_height=AC.fin_height, ... bare_length=AC.bare_length, pitch_parallel=AC.pitch_parallel, ... pitch_normal=AC.pitch_normal, tube_rows=AC.tube_rows, rho=1.217, ... mu=0.000018) 464.5433141865
- ht.air_cooler.h_Briggs_Young(m, A, A_min, A_increase, A_fin, A_tube_showing, tube_diameter, fin_diameter, fin_thickness, bare_length, rho, Cp, mu, k, k_fin)[source]¶
Calculates the air side heat transfer coefficient for an air cooler or other finned tube bundle with the formulas of Briggs and Young [1], [2] [3].
\[Nu = 0.134Re^{0.681} Pr^{0.33}\left(\frac{S}{h}\right)^{0.2} \left(\frac{S}{b}\right)^{0.1134} \]- Parameters
- mfloat
Mass flow rate of air across the tube bank, [kg/s]
- Afloat
Surface area of combined finned and non-finned area exposed for heat transfer, [m^2]
- A_minfloat
Minimum air flow area, [m^2]
- A_increasefloat
Ratio of actual surface area to bare tube surface area \(A_{increase} = \frac{A_{tube}}{A_{bare, total/tube}}\), [-]
- A_finfloat
Surface area of all fins in the bundle, [m^2]
- A_tube_showingfloat
Area of the bare tube which is exposed in the bundle, [m^2]
- tube_diameterfloat
Diameter of the bare tube, [m]
- fin_diameterfloat
Outer diameter of each tube after including the fin on both sides, [m]
- fin_thicknessfloat
Thickness of the fins, [m]
- bare_lengthfloat
Length of bare tube between two fins \(\text{bare length} = \text{fin interval} - t_{fin}\), [m]
- rhofloat
Average (bulk) density of air across the tube bank, [kg/m^3]
- Cpfloat
Average (bulk) heat capacity of air across the tube bank, [J/kg/K]
- mufloat
Average (bulk) viscosity of air across the tube bank, [Pa*s]
- kfloat
Average (bulk) thermal conductivity of air across the tube bank, [W/m/K]
- k_finfloat
Thermal conductivity of the fin, [W/m/K]
- Returns
- h_bare_tube_basisfloat
Air side heat transfer coefficient on a bare-tube surface area as if there were no fins present basis, [W/K/m^2]
Notes
The limits on this equation are 1000 < Re < 8000 , 11.13 mm < D_o < 40.89 mm, 1.42 mm < fin height < 16.57 mm, 0.33 mm < fin thickness < 2.02 mm, 1.30 mm < fin pitch < 4.06 mm, and 24.49 mm < normal pitch < 111 mm.
References
- 1
Briggs, D.E., and Young, E.H., 1963, “Convection Heat Transfer and Pressure Drop of Air Flowing across Triangular Banks of Finned Tubes”, Chemical Engineering Progress Symp., Series 41, No. 59. Chem. Eng. Prog. Symp. Series No. 41, “Heat Transfer - Houston”.
- 2
Mukherjee, R., and Geoffrey Hewitt. Practical Thermal Design of Air-Cooled Heat Exchangers. New York: Begell House Publishers Inc.,U.S., 2007.
- 3
Kroger, Detlev. Air-Cooled Heat Exchangers and Cooling Towers: Thermal-Flow Performance Evaluation and Design, Vol. 1. Tulsa, Okl: PennWell Corp., 2004.
Examples
>>> AC = AirCooledExchanger(tube_rows=4, tube_passes=4, tubes_per_row=20, tube_length=3, ... tube_diameter=1*inch, fin_thickness=0.000406, fin_density=1/0.002309, ... pitch_normal=.06033, pitch_parallel=.05207, ... fin_height=0.0159, tube_thickness=(.0254-.0186)/2, ... bundles_per_bay=1, parallel_bays=1, corbels=True)
>>> h_Briggs_Young(m=21.56, A=AC.A, A_min=AC.A_min, A_increase=AC.A_increase, A_fin=AC.A_fin, ... A_tube_showing=AC.A_tube_showing, tube_diameter=AC.tube_diameter, ... fin_diameter=AC.fin_diameter, bare_length=AC.bare_length, ... fin_thickness=AC.fin_thickness, ... rho=1.161, Cp=1007., mu=1.85E-5, k=0.0263, k_fin=205) 1422.872240323
- ht.air_cooler.h_ESDU_high_fin(m, A, A_min, A_increase, A_fin, A_tube_showing, tube_diameter, fin_diameter, fin_thickness, bare_length, pitch_parallel, pitch_normal, tube_rows, rho, Cp, mu, k, k_fin, Pr_wall=None)[source]¶
Calculates the air side heat transfer coefficient for an air cooler or other finned tube bundle with the formulas of [2] as presented in [1].
\[Nu = 0.242 Re^{0.658} \left(\frac{\text{bare length}} {\text{fin height}}\right)^{0.297} \left(\frac{P_1}{P_2}\right)^{-0.091} P_r^{1/3}\cdot F_1\cdot F_2 \]\[h_{A,total} = \frac{\eta A_{fin} + A_{bare, showing}}{A_{total}} h \]\[h_{bare,total} = A_{increase} h_{A,total} \]- Parameters
- mfloat
Mass flow rate of air across the tube bank, [kg/s]
- Afloat
Surface area of combined finned and non-finned area exposed for heat transfer, [m^2]
- A_minfloat
Minimum air flow area, [m^2]
- A_increasefloat
Ratio of actual surface area to bare tube surface area \(A_{increase} = \frac{A_{tube}}{A_{bare, total/tube}}\), [-]
- A_finfloat
Surface area of all fins in the bundle, [m^2]
- A_tube_showingfloat
Area of the bare tube which is exposed in the bundle, [m^2]
- tube_diameterfloat
Diameter of the bare tube, [m]
- fin_diameterfloat
Outer diameter of each tube after including the fin on both sides, [m]
- fin_thicknessfloat
Thickness of the fins, [m]
- bare_lengthfloat
Length of bare tube between two fins \(\text{bare length} = \text{fin interval} - t_{fin}\), [m]
- pitch_parallelfloat
Distance between tube center along a line parallel to the flow; has been called longitudinal pitch, pp, s2, SL, and p2, [m]
- pitch_normalfloat
Distance between tube centers in a line 90° to the line of flow; has been called the transverse pitch, pn, s1, ST, and p1, [m]
- tube_rowsint
Number of tube rows per bundle, [-]
- rhofloat
Average (bulk) density of air across the tube bank, [kg/m^3]
- Cpfloat
Average (bulk) heat capacity of air across the tube bank, [J/kg/K]
- mufloat
Average (bulk) viscosity of air across the tube bank, [Pa*s]
- kfloat
Average (bulk) thermal conductivity of air across the tube bank, [W/m/K]
- k_finfloat
Thermal conductivity of the fin, [W/m/K]
- Pr_wallfloat, optional
Prandtl number at the wall temperature; provide if a correction with the defaults parameters is desired; otherwise apply the correction elsewhere, [-]
- Returns
- h_bare_tube_basisfloat
Air side heat transfer coefficient on a bare-tube surface area as if there were no fins present basis, [W/K/m^2]
Notes
The tube-row count correction factor is 1 for four or more rows, 0.92 for three rows, 0.84 for two rows, and 0.76 for one row according to [1].
The property correction factor can be disabled by not specifying Pr_wall. A Prandtl number exponent of 0.26 is recommended in [1] for heating and cooling for both liquids and gases.
References
- 1(1,2,3)
Hewitt, G. L. Shires, T. Reg Bott G. F., George L. Shires, and T. R. Bott. Process Heat Transfer. 1st edition. Boca Raton: CRC Press, 1994.
- 2
“High-Fin Staggered Tube Banks: Heat Transfer and Pressure Drop for Turbulent Single Phase Gas Flow.” ESDU 86022 (October 1, 1986).
- 3
Rabas, T. J., and J. Taborek. “Survey of Turbulent Forced-Convection Heat Transfer and Pressure Drop Characteristics of Low-Finned Tube Banks in Cross Flow.” Heat Transfer Engineering 8, no. 2 (January 1987): 49-62.
Examples
>>> AC = AirCooledExchanger(tube_rows=4, tube_passes=4, tubes_per_row=20, tube_length=3, ... tube_diameter=1*inch, fin_thickness=0.000406, fin_density=1/0.002309, ... pitch_normal=.06033, pitch_parallel=.05207, ... fin_height=0.0159, tube_thickness=(.0254-.0186)/2, ... bundles_per_bay=1, parallel_bays=1, corbels=True)
>>> h_ESDU_high_fin(m=21.56, A=AC.A, A_min=AC.A_min, A_increase=AC.A_increase, A_fin=AC.A_fin, ... A_tube_showing=AC.A_tube_showing, tube_diameter=AC.tube_diameter, ... fin_diameter=AC.fin_diameter, bare_length=AC.bare_length, ... fin_thickness=AC.fin_thickness, tube_rows=AC.tube_rows, ... pitch_normal=AC.pitch_normal, pitch_parallel=AC.pitch_parallel, ... rho=1.161, Cp=1007., mu=1.85E-5, k=0.0263, k_fin=205) 1390.88891804
- ht.air_cooler.h_ESDU_low_fin(m, A, A_min, A_increase, A_fin, A_tube_showing, tube_diameter, fin_diameter, fin_thickness, bare_length, pitch_parallel, pitch_normal, tube_rows, rho, Cp, mu, k, k_fin, Pr_wall=None)[source]¶
Calculates the air side heat transfer coefficient for an air cooler or other finned tube bundle with low fins using the formulas of [1] as presented in [2] (and also [3]).
\[Nu = 0.183Re^{0.7} \left(\frac{\text{bare length}}{\text{fin height}} \right)^{0.36}\left(\frac{p_1}{D_{o}}\right)^{0.06} \left(\frac{\text{fin height}}{D_o}\right)^{0.11} Pr^{0.36} \cdot F_1\cdot F_2 \]\[h_{A,total} = \frac{\eta A_{fin} + A_{bare, showing}}{A_{total}} h \]\[h_{bare,total} = A_{increase} h_{A,total} \]- Parameters
- mfloat
Mass flow rate of air across the tube bank, [kg/s]
- Afloat
Surface area of combined finned and non-finned area exposed for heat transfer, [m^2]
- A_minfloat
Minimum air flow area, [m^2]
- A_increasefloat
Ratio of actual surface area to bare tube surface area \(A_{increase} = \frac{A_{tube}}{A_{bare, total/tube}}\), [-]
- A_finfloat
Surface area of all fins in the bundle, [m^2]
- A_tube_showingfloat
Area of the bare tube which is exposed in the bundle, [m^2]
- tube_diameterfloat
Diameter of the bare tube, [m]
- fin_diameterfloat
Outer diameter of each tube after including the fin on both sides, [m]
- fin_thicknessfloat
Thickness of the fins, [m]
- bare_lengthfloat
Length of bare tube between two fins \(\text{bare length} = \text{fin interval} - t_{fin}\), [m]
- pitch_parallelfloat
Distance between tube center along a line parallel to the flow; has been called longitudinal pitch, pp, s2, SL, and p2, [m]
- pitch_normalfloat
Distance between tube centers in a line 90° to the line of flow; has been called the transverse pitch, pn, s1, ST, and p1, [m]
- tube_rowsint
Number of tube rows per bundle, [-]
- rhofloat
Average (bulk) density of air across the tube bank, [kg/m^3]
- Cpfloat
Average (bulk) heat capacity of air across the tube bank, [J/kg/K]
- mufloat
Average (bulk) viscosity of air across the tube bank, [Pa*s]
- kfloat
Average (bulk) thermal conductivity of air across the tube bank, [W/m/K]
- k_finfloat
Thermal conductivity of the fin, [W/m/K]
- Pr_wallfloat, optional
Prandtl number at the wall temperature; provide if a correction with the defaults parameters is desired; otherwise apply the correction elsewhere, [-]
- Returns
- h_bare_tube_basisfloat
Air side heat transfer coefficient on a bare-tube surface area as if there were no fins present basis, [W/K/m^2]
Notes
The tube-row count correction factor F2 can be disabled by setting tube_rows to 10. The property correction factor F1 can be disabled by not specifying Pr_wall. A Prandtl number exponent of 0.26 is recommended in [1] for heating and cooling for both liquids and gases.
There is a third correction factor in [1] for tube angles not 30, 45, or 60 degrees, but it is not fully explained and it is not shown in [2]. Another correction factor is in [2] for flow at an angle; however it would not make sense to apply it to finned tube banks due to the blockage by the fins.
References
- 1(1,2,3)
Hewitt, G. L. Shires, T. Reg Bott G. F., George L. Shires, and T. R. Bott. Process Heat Transfer. 1st edition. Boca Raton: CRC Press, 1994.
- 2(1,2,3)
“High-Fin Staggered Tube Banks: Heat Transfer and Pressure Drop for Turbulent Single Phase Gas Flow.” ESDU 86022 (October 1, 1986).
- 3
Rabas, T. J., and J. Taborek. “Survey of Turbulent Forced-Convection Heat Transfer and Pressure Drop Characteristics of Low-Finned Tube Banks in Cross Flow.” Heat Transfer Engineering 8, no. 2 (January 1987): 49-62.
Examples
>>> AC = AirCooledExchanger(tube_rows=4, tube_passes=4, tubes_per_row=8, tube_length=0.5, ... tube_diameter=0.0164, fin_thickness=0.001, fin_density=1/0.003, ... pitch_normal=0.0313, pitch_parallel=0.0271, fin_height=0.0041, corbels=True)
>>> h_ESDU_low_fin(m=0.914, A=AC.A, A_min=AC.A_min, A_increase=AC.A_increase, A_fin=AC.A_fin, ... A_tube_showing=AC.A_tube_showing, tube_diameter=AC.tube_diameter, ... fin_diameter=AC.fin_diameter, bare_length=AC.bare_length, ... fin_thickness=AC.fin_thickness, tube_rows=AC.tube_rows, ... pitch_normal=AC.pitch_normal, pitch_parallel=AC.pitch_parallel, ... rho=1.217, Cp=1007., mu=1.8E-5, k=0.0253, k_fin=15) 553.85383647
- ht.air_cooler.h_Ganguli_VDI(m, A, A_min, A_increase, A_fin, A_tube_showing, tube_diameter, fin_diameter, fin_thickness, bare_length, pitch_parallel, pitch_normal, tube_rows, rho, Cp, mu, k, k_fin)[source]¶
Calculates the air side heat transfer coefficient for an air cooler or other finned tube bundle with the formulas of [1] as modified in [2].
Inline:
\[Nu_d = 0.22Re_d^{0.6}\left(\frac{A}{A_{tube,only}}\right)^{-0.15}Pr^{1/3} \]Staggered:
\[Nu_d = 0.38 Re_d^{0.6}\left(\frac{A}{A_{tube,only}}\right)^{-0.15}Pr^{1/3} \]- Parameters
- mfloat
Mass flow rate of air across the tube bank, [kg/s]
- Afloat
Surface area of combined finned and non-finned area exposed for heat transfer, [m^2]
- A_minfloat
Minimum air flow area, [m^2]
- A_increasefloat
Ratio of actual surface area to bare tube surface area \(A_{increase} = \frac{A_{tube}}{A_{bare, total/tube}}\), [-]
- A_finfloat
Surface area of all fins in the bundle, [m^2]
- A_tube_showingfloat
Area of the bare tube which is exposed in the bundle, [m^2]
- tube_diameterfloat
Diameter of the bare tube, [m]
- fin_diameterfloat
Outer diameter of each tube after including the fin on both sides, [m]
- fin_thicknessfloat
Thickness of the fins, [m]
- bare_lengthfloat
Length of bare tube between two fins \(\text{bare length} = \text{fin interval} - t_{fin}\), [m]
- pitch_parallelfloat
Distance between tube center along a line parallel to the flow; has been called longitudinal pitch, pp, s2, SL, and p2, [m]
- pitch_normalfloat
Distance between tube centers in a line 90° to the line of flow; has been called the transverse pitch, pn, s1, ST, and p1, [m]
- tube_rowsint
Number of tube rows per bundle, [-]
- rhofloat
Average (bulk) density of air across the tube bank, [kg/m^3]
- Cpfloat
Average (bulk) heat capacity of air across the tube bank, [J/kg/K]
- mufloat
Average (bulk) viscosity of air across the tube bank, [Pa*s]
- kfloat
Average (bulk) thermal conductivity of air across the tube bank, [W/m/K]
- k_finfloat
Thermal conductivity of the fin, [W/m/K]
- Returns
- h_bare_tube_basisfloat
Air side heat transfer coefficient on a bare-tube surface area as if there were no fins present basis, [W/K/m^2]
Notes
The VDI modifications were developed in comparison with HTFS and HTRI data according to [2].
For cases where the tube row count is less than four, the coefficients are modified in [2]. For the inline case, 0.2 replaces 0.22. For the stagered cases, the coefficient is 0.2, 0.33, 0.36 for 1, 2, or 3 tube rows respectively.
The model is also showin in [4].
References
- 1
Ganguli, A., S. S. Tung, and J. Taborek. “Parametric Study of Air-Cooled Heat Exchanger Finned Tube Geometry.” In AIChE Symposium Series, 81:122-28, 1985.
- 2(1,2,3)
Gesellschaft, V. D. I., ed. VDI Heat Atlas. 2nd edition. Berlin; New York:: Springer, 2010.
- 3
Serth, Robert W., and Thomas Lestina. Process Heat Transfer: Principles, Applications and Rules of Thumb. Academic Press, 2014.
- 4
Kroger, Detlev. Air-Cooled Heat Exchangers and Cooling Towers: Thermal-Flow Performance Evaluation and Design, Vol. 1. Tulsa, Okl: PennWell Corp., 2004.
Examples
Example 12.1 in [3]:
>>> AC = AirCooledExchanger(tube_rows=4, tube_passes=4, tubes_per_row=56, tube_length=36*foot, ... tube_diameter=1*inch, fin_thickness=0.013*inch, fin_density=10/inch, ... angle=30, pitch_normal=2.5*inch, fin_height=0.625*inch, corbels=True)
>>> h_Ganguli_VDI(m=130.70315, A=AC.A, A_min=AC.A_min, A_increase=AC.A_increase, A_fin=AC.A_fin, ... A_tube_showing=AC.A_tube_showing, tube_diameter=AC.tube_diameter, ... fin_diameter=AC.fin_diameter, bare_length=AC.bare_length, ... fin_thickness=AC.fin_thickness, tube_rows=AC.tube_rows, ... pitch_parallel=AC.pitch_parallel, pitch_normal=AC.pitch_normal, ... rho=1.2013848, Cp=1009.0188, mu=1.9304793e-05, k=0.027864828, k_fin=238) 969.285081857