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Al-Khwarizmi 
  Engineering  

Journal 
Al-Khwarizmi Engineering Journal,Vol. 13, No. 4, P.P. 30- 40 (2017) 

 

Natural-Convection Phenomenon from a Finned Heated 

                            Vertical Tube: Experimental Analysis 
      

                                                 Saad Najeeb Shehab       
        Department of Mechanical Engineering / Engineering Faculty / Al-Mustansiriayah University  

                                                                    Email: saad_najeeb16@ yahoo.com 

 
(Received 29 March 2017; accepted 21 May 2017) 

https://doi.org/10.22153/kej.2017.05.004 
 

 

Abstract  
  

       In this work, an experimental analysis is made to predict the thermal performance of the natural-convection 
phenomenon from a heated vertical externally finned-tube to surrounding air through an open-ended enclosure. Two 

different configurations of longitudinal rectangular fin namely, continuous and interrupted are utilized with constant 
thickness, different numbers, and different heights are extended radially on the outer surface of a heated tube. The tube 

is heated electrically from inner surface with five varied power input magnitudes. The effect of fins configuration, fins 
number, fins height, and heat flux of the inner tube surface on the thermal performance of natural convection have been 

studied and analyzed experimentally. Obtained results show that the tube with twelve interrupted longitudinal fins gives 

the best natural-convection thermal performance in terms of average Nusselt number, about 20% greater than that for 

the tube with continuous fins. Experimental correlations to predict the average Nusselt number for the heated tubes with 

continuous and interrupted longitudinal fins are proposed. The present data are compared to previous study and good 
convergence is noticed. 

  

Keywords: Vertical tube, continuous, interrupted, finned, natural-convection. 

 

 

1. Introduction  

 
     The natural-convection heat transfer from a 

vertical, horizontal, and inclined heated finned 

tube in different fin positions to surrounding air 
occurs in a many industrial and engineering 

applications. The importance applications are heat 

exchangers, evaporators, condensers, oil cooling 
systems, solar collectors, systems of energy 

storage,…and etc.  The main purpose of these 

systems or equipments is to increase of heat 

dissipation rate from tube surface by utilizing 
different configuration of fins with varying 

heights and numbers, and high thermal 

conductivity materials.        
Morgan [1] published a review of articles for 

the natural heat convection from outside surface 

of a heated smooth circular cylinder to 
surrounding air. He correlated the available 

experimental data to predict the Nusselt number 

values based on the diameter of cylinder for a 

wide range of Rayleigh numbers. Stewart  

and Verhulst [2] experimentally investigated the 
two dimensional natural-convection from a two 

heated copper horizontal tubes to cooled 

rectangular-section enclosure at constant 
temperature condition to simulate the natural-

convection heat transfer in systems of the 

underground thermal distribution. They correlated 

the experimental data to determine the Nusselt 
number for Rayleigh numbers ranging from 

2.1×10
8
 to 4.8×10

9
, and found that the natural-

convection heat coefficients computed for 
underground or utility corridors case with air as 

working fluid smaller compared with other 

experimental correlations for concentric tubes. 
Wu and Tao [3] numerically simulated the heat 

transfer by laminar natural-convection from a 

heated horizontal compound cylinder with 

longitudinal external fins. They utilized the 



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

31 

 

conjugated computational approach with primitive 
variables, and found the optimum fins number at a 

fixed fin height and the optimum fin height for a 

constant fins number. Kadhim and Abdulhussain 
[4] performed an experimental investigation for 

natural-convection from external surface of finned 

cylinder to surrounding air. They used two 

configuration of an external fins namely, 
triangular and rectangular with different 

inclination angles of cylinder and heat fluxes, and 

noted that the heat transfer from the triangular 
finned-cylinder is maximum at an inclination 90

o
 

(vertical position). Dogan et al. [5] presented a 

numerical investigation for natural-convection 

heat transfer from annular fins on a heated 
horizontal cylinder. They studied the effect of fin 

spacing, fin diameter, and temperatures difference 

between the base and the surrounding on the 
performance of heat transfer. They suggested a 

correlation to obtain the optimum fin spacing as 

function of fin diameter and Rayleigh number. 
Totala et al. [6] presented an experimental 

investigation for natural heat convection from a 

heated vertical cylinder to surrounding air. They 

evaluated experimentally the local natural 
convection heat transfer coefficient along the 

height of cylinder and compared the results of 

them with obtained results from a theoretical part 
and they found a good convergence between of 

them. Also, they found the maximum values of 

local heat transfer coefficient at the beginning and 
gradually reduces in the upward direction. 

Niezgoda-Zelasko and Zelasko [7] experimentally 

investigated the natural and forced-convection 

from longitudinally finned cylinder in vertical 
position. They used two air flow velocities, 

parallel and cross flow to the cylinder axis and 

computed experimentally convection heat transfer 
coefficients values for all cases. They found that 

the convection heat transfer coefficients for case 

of perpendicular flow 22% greater than case of 

parallel flow for cylinder axis and developed 
experimental correlations to compute heat transfer 

coefficient for natural and two cases of forced-

convection. Lee et al. [8] experimentally 
investigated the natural heat convection from 

vertical cylinder with two different types of plate-

fins namely, radial and inclined. They studied 
many parameters like number of fins, inclined 

angle of fins, and base temperatures on the 

convection heat transfer rate. They observed that 

the optimal heat resistance of cylinder with 
inclined plate-fins is 30% less with that of 

cylinder with radial plate-fins.  

     The objective of the present work is to present 
an experimental analysis for the natural heat 

convection from vertical externally finned-tube to 
surrounding air inside an open-ended enclosure 

utilizing two different configurations of external 

longitudinal fin, continuous and interrupted, with 
different numbers, heights, and regular distributed 

radially on the external surface of the heated tube. 

The influence of fins shape, fins number, fin 

height, and surface heat flux on the thermal 
performance of the natural-convection 

phenomenon is taken into consideration.  

 
 

2. Experimental-Setup 

 
     The experimental-setup is designed and 
manufactured to cover the experiments of the 

present work as shown in Figure (1). It consists of 

externally-finned tube vertically assembly inside 
an open ended square-section enclosure, voltage 

regulator, digital multi meter, and twelve channels 

data logger thermometer. The finned-tube 
assembly is fixed vertically into an acrylic sheet 

enclosure opened from top and bottom utilizing a 

plastic stand. It consists of tube with external 

diameter (D) of 28 mm,  inner   diameter  (d) of 
20 mm and length (L) of 200 mm and made from 
polished aluminum. Two configurations of 

longitudinal rectangular fin, continuous and 
interrupted are made from the same material of 

tube with thickness (t) of 2 mm and fixed radially 
on the tube outer surface with different numbers 

and heights. The interrupted fin consists of three 

equal segments with length (Lint) of 60 mm and 
the blank (b) between two segments is 10 mm as 
illustrated in Figure (2). The inside surface of tube 
is heated electrically using heating coil of 500 W 

capacity and putted in a Pyrex glass pipe with 

outer diameter of 20 mm to fit into the externally-

finned tube and joined to a voltage regulator 
model SAKO-TDGC2 size of 0.5 KVA with rating 

of current 2 A and voltage from 0 to 250 V to 

control the supplied voltage for the electrical 
heater. A digital multi meter type VICTOR-

VC890C
+
 having voltage range from 2 V to 750 V 

and current range from 20 mA to 20 A is utilized 
to gauge the supplied voltage and alternating 

current intensity passing to the heating coil. Two 

Teflon covers of 25 mm thickness are utilized to 

insulate and minimize heat lost from tube ends.  
The outer surface temperatures of tube are 

recorded using ten type-K calibrated 

thermocouples are distributed axially along the 
height of tube with equal distances as shown in 

Figure (3) also two the same type-K calibrated 

thermocouples are utilized to read the 

temperatures difference through Teflon covers in 



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

32 

 

the two ends of the tube to estimate the heat 
conduction lost, and connected to a twelve 

channels data logger thermometer model BTM-

4208SD  of   resolution  0.1 
o
C and   rating   from 

-100
 o

C to 1000 
o
C for type-K thermocouple prob. 

Another digital type-K calibrated thermocouple is 

used to measure the surrounding air temperature 

inside an enclosure. 

                                                

 
                                                                  a. Sketch of an experimental-setup 

 

 
                                                       b. Photos of an experimental-setup                                                                                          
1. Vertical externally-finned tube   2. Open ended enclosure    3. Stand    4. Voltage regulator    5. Digital multi meter   

6. Data logger thermometer   7. Heater    8. Thermocouple wires   9. Teflon covers   10. Longitudinal rectangular fins. 
 

Fig. 1. Experimental-setup.  

 

            
                        a. Tube with continuous fins                                                     b. Tube with interrupted fins 
 Fig. 2. Front views of longitudinal rectangular fins configuration.  



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

33 

 

 
                                              
Fig. 3. Schematic diagram of front-section for 

vertical externally-finned tube assembly with 

thermocouples locations. 

 

 

3. Tests Procedure and Computation 

 
     The present work is carried out for thirty 
different finned tubes. Two types of external 
longitudinal fin, continuous and interrupted are 

utilized with fixed length (L) of 200 mm and 
thickness (t) of 2 mm for all fins. The interrupted 
longitudinal fin consists of three segments of fins 

with constant length (Lint) of 60 mm and constant 
blank (b) of 10 mm, (Lint/b= 6). Five different 
numbers of each continuous and interrupted fins 

(N) namely, four, six, eight, twelve, and sixteen 
are fitted radially on the outer surface of heated 

tube with three different heights (H) 10, 20, and 
30 mm. Five varying values of surface heat fluxes 

(q) namely, 796, 1990, 3981, 5971, and 7962 
W/m

2
 are utilized.                                     

     The steady-state conditions for all experiments 
of the present work are attained from 90 to 120 

minutes depending on the power input. The 

thermocouples readings have been registered 
when the difference of two readings of 

temperatures is ± ≤ 0.5 oC within 15 minutes 
approximately. Then, the tube surface 
temperatures, surrounding air temperature inside 

an enclosure, input voltage, and current intensity 

passed to electrical heater are registered.  

     The power input (Qin) to the electrical heater 
into tube is computed as product of voltage (V) 
and input current (I) with power factor (cos ϕ): 

 ��� = � � �	
�                                                  … (1) 
It’s transformed to heat energy and transferred 

from finned-tube to air surrounding by natural-

convection (Qconv) and thermal radiation (Qrad), 
moreover the thermal conduction lost (Qcond) from 
ends of vertical finned-tube. Then,   ��� = ����� + ���� + �����                            … (2)  
    The loss of thermal radiation between outer 
surfaces of finned-tube and surrounding air inside 

an enclosure is calculated as follows [9]: ���� = � � ��� (����� − ���  )                            … (3) 
where, ε = 0.05 is the emissivity of polished aluminum, 
F is the shape factor, Ta is the surrounding air 
temperature, and Tsav is the average outer surface 
temperatures of vertical tube. For interval from 0 

to tube height (L) is computed as follows [9]: 

 ���� = 1"   # ��$
%

&  '(                                          … (4) 
where, Tsx is the local surface temperature. 
    The heat conduction loss (Qcond) is computed as 
thermal potential difference to thermal resistance. 

It’s found less than 3% of power input (Qin) 
because the two thick covers of Teflon are utilized 

in the finned-tube ends therefore can be neglected. 

Then the heat transfer by natural-convection 

(Qconv) can be computed as follows: �����  = � � �	
� − ����                                 … (5) 
It's also can be calculated from Newton’s equation 
of cooling as follows [10, 11]:  ����� =  ℎ��  �� (���� − �� )                           …  (6)  
The   average   natural-convection    heat   transfer 

coefficient (hav) can be calculated as:           
 ℎ�� = � � �	
� − ����    �� (���� − �� )                                  … (7) 
As is the surface area of finned-tube and computed 

as follows:  

 - tube with continuous longitudinal rectangular 

fins, �� = (./" − 01") + 202"                            … (8)  
 - tube with interrupted longitudinal rectangular 

fins, �� = (./" − 301"��4 ) + 602"��4                … (9) 
where, 

(D) is the outside diameter of tube,  (L) is the 
height of tube or fin length, (H) is the fin height, 

(N) is the fins number, (t) is the fin thickness, and 
(Lint) is segment length of interrupted fin. 
      The heat flux (q) practiced on the finned-tube 
is computed from power input to heating element 

dividing by inner surface area of tube (A): 

6 = ���� =
�� �	
�

.'"                                           … (10) 



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

34 

 

     The average Nusselt number (Nuav) based on 
the external diameter of finned-tube (Df) as 
characteristics length can be simply computed as: 

 08�� = ℎ��  /9:                                                 … (11) 
Also average Rayleigh number (Raav) is computed 
from:  ;<�� = =>�� ?>                                                … (12) 
where, (Pr) is Prandtl number and (Grav) is the 
average Grashof number (Grav): 

 =>�� = @A /9
B(���� − �� )CD                             … (13) 

and A = 1 �9⁄                                                             … (14) 
     Air properties utilized in the experimental 

calculations are taken at film temperature (Tf). It is 
computed as the arithmetic mean between the 

surrounding air temperature (Ta) and average 
surface temperature (Tsav) of the heated finned-
tube in (K).  

    The percentage error (e%) is evaluted as the 
percentage relative of absolute error (eab) to 
experimental value (Vexp): 

F% = F�H�I$J K 100 = L
�I$J − �����I$J L K 100   … (15) 

where, the absolute error (eab) is the absolute 
difference between experimental value (Vexp) and 
correlated value (Vcor) as follows:  F�H = M�I$J − ���� M                                          … (16) 
The mean relative quadratic error (ē) is computed 
as: 

F̅ =  OP Q�I$J − �����I$J R
D�

�ST
(U − 1)V W

T D⁄
    … (17) 

where, n is the data points number.  
 
 

4. Results and Discussions 

 
      The present work investigates experimentally 

effect of the fin configurations (continuous and 
interrupted), fin height, fin numbers, and the 

surface heat flux on the thermal performance for a 

heated finned-tube in vertical position into an 
enclosure with open ends. 

      Figures (4) to (7) illustrate the effect of 

number of fins on the temperatures difference 

(ΔT=Tsav–Ta) and average heat-transfer coefficient 
at different surface heat fluxes ranging from 796 

to 7962 W/m
2
 and fin height (H= 30 mm) for 

continuous and interrupted fins. They are clear 

that the temperatures difference (ΔT) and average 
heat-transfer coefficient (hav) sharply increases as 
surface heat flux (q) increases. Also, the average 

heat-transfer coefficient (hav) increases with 
increasing fins number (N) up to N= 12 and then 
decreases because the average surface temperature 

(Tsav) decreases with fins number increasing up to 
N= 12 and then increasing when the thermal 
dissipation by natural convection for tubes with 

16-fins becomes poor. Additionally, Figures (6) 

and (7) appear the values of average natural-
convection heat coefficient for interrupted fins are 

larger than those continuous fins because the 

interruptions in fin help to dissipate the growth of 

thermal boundary layer and interrupting it. 
 

 
 

Fig. 4. Effect of fins number on the temperaturestemperaturestemperaturestemperatures 
difference and surface heat flux for the continuous 

longitudinal fins.  

 
 

 
Fig. 5. Effect of fins number on the temperatures temperatures temperatures temperatures differencedifferencedifferencedifference and surface heat flux for the interrupted 
longitudinal fins.  



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

35 

 

 
 

Fig. 6. Effect of fins number on the average heat average heat average heat average heat transfer coefficienttransfer coefficienttransfer coefficienttransfer coefficient and surface heat flux for the 
continuous longitudinal fins.  

 
 

 
 

Fig. 7. Effect of fins number on the average heat average heat average heat average heat transfer coefficienttransfer coefficienttransfer coefficienttransfer coefficient and surface heat flux for the 
interrupted longitudinal fins. 

 

 
     Figure (8) shows the behavior of average 

Nusselt number (Nuav) against fins number (N) for 
continuous and interrupted longitudinal fins at 

three varying fin heights (H= 10, 20, and 30 mm) 
and different surface heat fluxes. It is clear that 

the average Nusselt number as a function of fins 
number at first increases up to a maximum value 

with the increase of fins number and then 

decreases. The optimum fins number (Nopt) at 
maximizing average Nusselt number is (Nopt= 12) 
for all cases because the average surface 

temperature (Tsav) decreases down to a minimum 
value with fins number increasing up to (N= 12) 
and then increases. This leads to bad natural-

convection thermal performance at fins number   

(N= 16). Also it is clear that the values of average 
Nusselt number for interrupted longitudinal fins 
are greater than those of continuous fins. The 

interrupted fins cause higher values of natural-

convection heat transfer coefficient because the 
interruptions help to dissipate the growth of 

thermal boundary layer along the height of tube 

and interrupting it, and this leads to a higher 
natural-convection heat transfer rate and 

improvement of natural-convection thermal 

performance. Finally, it is clear that the average 

Nusselt number enhanced when surface heat flux 
increases because the average convection heat 

transfer coefficient increases as surface heat flux 

increasing for all studied cases. 

      Figure (9) appears two correlations between 

average Nusselt number and Rayleigh  number for 

two configurations of fin, continuous and 

interrupted at constant fins number (N= 12) and 
fin height (H= 30 mm) with a wide range of heat 
fluxes from 796 to 7962 W/m

2
. It is clear that the 

average Nusselt number increases with increasing 

average Rayleigh number. The following two 

experimental correlations for continuous and 

interrupted fins respectively; are concluded: 08�� = 6 K  10iDD(;<�� )B.�klT                   … (18) 08�� = 5 K 10iTm  (;<�� )D.l&n                     … (19) 
     Figures (10) and (11) show comparisons of the 

correlated average Nusselt numbers by Eqs. (18) 

and (19) with those experimental of present data 
for tubes with continuous and interrupted 

longitudinal fins. They are clear that the 

percentage error (e%) of the experimental values 
located between +8% and -8% of correlated 
values for continuous fins and between +10% and 

-7% of correlated values for interrupted fins. Also 

the mean relative quadratic errors (ē) are 0.168 
and 0.119 for continuous and interrupted fins 

respectively. 
     Moreover, the experiment is carried out on a 
heated vertical smooth tube with same conditions 

to compare than Morgan correlation: 08o = 0.48 (=>o  ?>)&.Dn                               … (20) 
This is valid for values of Rayleigh number 

between 10
2
 ≤ Ra ≤ 107 as shown Figure (12). It 

can be seen a good agreement in behavior.  

  



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

36 

 

 
                 a. Surface heat flux, q= 796 W/m2  

 
                  b. Surface heat flux, q= 1990 W/m2 

 

 
                c. Surface heat flux, q= 3981 W/m2  
  

 
                 d. Surface heat flux, q= 5971 W/m2  
 

                                          
                                                         e. Surface heat flux, q= 7962 W/m2  
 
 Fig. 8. Behavior of verage Nusselt number against fins number for different fin heights and surface heat fluxes.  



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

37 

 

 
Fig. 9. Experimental analysis of present data for continuous and interrupted longitudinal fins with concluded 

correlations.  

 

 

                         
Fig. 10. Comparison of correlated average Nusselt numbers with those of the present experimental work for 

continuous longitudinal fins. 

 

 

                        
Fig. 11. Comparison of correlated average Nusselt numbers with those of the present experimental work for 

interrupted longitudinal fins. 



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

38 

 

                            
       Fig. 12. Comparison the present experimental data for a heated smooth tube with Morgan [1] correlation.  
 

 

5. Conclusions 

 
      The present work has performed an 
experimental analysis of a heated vertical 
externally-finned tube inside an opened enclosure 

exposed to natural-convection. The tube is 

electrically heated under constant surface heat 
flux and steady-state conditions. Continuous and 

interrupted longitudinal rectangular fins are 

utilized with different heights and numbers. The 
main conclusions can be drawn: 

1. The average Nusselt number is strongly a 
function of fins number, fin height, and surface 

heat flux.  
2. The optimum value of fins number is (Nopt= 

12) for interrupted and continuous fins when 

maximizing average Nusselt number.  
3. The average Nusselt number improves with 

increasing fin height and reaches to maximum 

values at (H= 30 mm).  
4. The tube with twelve-interrupted longitudinal 

fins gave best natural-convection thermal 

performance in terms of average Nusselt 

number about 20% higher than those 
continuous longitudinal fins. 

5. Two experimental correlations are concluded 
to expect the values of average Nusselt number 
for interrupted and continuous longitudinal 

finned-tubes. 

 

 

Nomenclature 

 
A                internal surface area of finned-tube, (m2) 
As surface area of heat transfer, (m

2
) 

b interrupted length, (m) 
d internal diameter of tube, (m) 
D external diameter of tube, (m) 

Df   external diameter of finned-tube, (m) 
F shape factor 
g gravitational acceleration, (m/s2) 
Gr Grashof number 
h convection heat transfer coefficient, 

(W/m
2
.K) 

H height of fin, (m) 
I input current, (A) 
k thermal conductivity, (W/m.K) 
Lint length of fin segment, (m) 
L height of tube or fin length, (m) 
N number of fins 
Nu Nusselt number 
Pr Prandtl number 
q surface heat flux, (W/m2) 
Qcond rate of heat conduction loss, (W) 
Qconv rate of natural-convection heat transfer, 

(W) 

Qin power input, (W) 
Qrad heat radiation loss, (W) 
Ra Rayleigh number 
t thickness of fin, (m) 
Ta surrounding air temperature, (

o
C) 

Tf film temperature, (K) 
Ts surface temperature, (

o
C) 

V voltage, (V) 
 
 

Greek Letters  

 ΔT Temperatures differences, (K) cos ϕ power factor  
β volumetric coefficient of thermal 

expansion, (1/K) 

ε surface emissivity 
ν kinematic viscosity, (m2/s) 
σ constant of Stefan-Boltzmann,                    

(5.67 × 10
-8

 W/ m
2
.K

4
) 



 Saad Najeeb Shehab                       Al-Khwarizmi Engineering Journal, Vol. 13, No. 4, P.P. 30- 40 (2017) 
 

39 
 

 

Subscript Symbols 

  
av average 
D based on tube external diameter 
opt optimum 
x local 
 

 

6. References  
 

[1] Morgan, V. T. “The Overall Convective Heat 
Transfer from Smooth Circular Cylinders”, 

Advances in Heat Transfer, Elsevier Ltd., Vol. 
11, pp. 199-264, 1975. 

[2] Stewart, W. E. and Verhulst, J. L. 
“Experimental Free Convection from Piping in 
District Heating Utilidors”, Journal of Energy 

Resources Technology, ASME, 108 (2), PP. 

173-178, 1986. 
[3] Wu, J. M. and Tao, W. Q. “Numerical 

Computation of Laminar Natural Convection 

Heat Transfer around a Horizontal Compound 

Tube with External Longitudinal Fins”, Journal 
of Heat Transfer Engineering, Vol. 28, Issue 2, 

pp. 93-102, 2007. 

[4] Kadhim, S. K. and Abdulhussain, K. 
“Experimental Study of  Inclination  Angle and 

Surface Area Effects for  Longitudinally  

Finned Cylinder on  Free  Convection  Heat 

Transfer in an Open Enclosure“ ,  Journal of 
Engineering and Technology, Vol. 27, No. 5, 

pp.171-179, 2009. 

[5] Dogan, A., Akkus, S. and Baskaya, S. 
“Numerical Analysis of Natural Convection 

Heat Transfer from Annular Fins on a 
Horizontal Cylinder“, Journal of Thermal 

Science and Technology, Vol. 32, No. 2, pp. 

31-41, 2012. 
[6] Totala, B.T., Shimpi, M.V., Shete, N.L. and  

Bhopate, V.S. “Natural  Convection 

Characteristics  in  Vertical  Cylinder “ ,  

International   Journal  of Engineering  and 
Sciences, Vol. 3, Issue 8, pp. 27-31, 2013. 

[7] Niezgoda-Zelasko, B. And  Zelasko,    J.  ”Free  
and  Forced  Convection  on  the Outer Surface 
of Vertical Longitudinally Finned Tubes”,  

Experimental Thermal and Fluid Science 

Journal, Elsevier Inc., Vol. 57 . pp. 145-156, 

September 2014.  
[8] Lee, J. B., Kim, H. J. and   Kim, D. 

“Experimental  Study  of  Natural  Convection 

Cooling of Vertical Cylinders with Inclined 
plate Fins”, Energies Journal, 9, 391, pp. 1-15, 

2016. 

[9] Cengel, Y. A. “Heat Transfer: A Practical 
Approach“, McGraw-Hill Companies, Second 

Edition, USA, 2008.  

[10] Favre-Marient, M. and Tardu, S.  “Convective 
Heat Transfer“, John-Wiley and Sons, Inc., 
First Edition, USA, 2009. 

[11] Bejan, A.“Convection Heat Transfer“, John-
Wiley and Sons Inc., Fourth Edition, USA, 
2013. 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

                  

 

 

 

 

 

 



   
 )2017( 30-40، صفحة 4د، العد13دجلة الخوارزمي الهندسية المجلم                                                        سعد نجيب شهاب      

 

40 

 

 

 

  تجريبيتحليل : مزعنف  الطبيعي من أنبوب عمودي مسخنظاهرة الحمل 
                                     

  سعد نجيب شهاب                                                            
  قسم الهندسة الميكانيكية / كلية الهندسة / الجامعة المستنصرية                                                            

 saad_najeeb16@ yahoo.comالبريد اللكتروني:                                                                 

                                                

  

                                            
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الى الهواء المحيط داخل مغل;ف  الحمل الطبيعي من أنبوب عمودي مزعنف خارجياً للتنبؤ باألداء الحراري لظاهرة   ةتجريبي يتناول هذا البحث دراسة      

متقطع;ة بس;مك ثاب;ت وأرتفاع;ات وأع;داد مختلف;ة وّزع;ت بش;كل مس;تطيلة طولي;ة من الزعانف ، مستطيلة طولي;ة مس;تمرة و نوعان مفتوح النهايتين.  أستخدم
للقدرة الداخلة. تم دراسة  تأثير شكل  مستويات مختلفة ةشعاعي على السطح الخارجي لألنبوب المسخن. تم تسخين األنبوب كهربائيا من السطح الداخلي بخمس

 النتائج المستحصلة أن األنبوب ذا داء الحراري للحمل الطبيعي عمليا. أظهرتوالفيض الحراري لسطح األنبوب على األوارتفاعهاالزعانف  الزعانف وعدد
ً حراريأداء  زعنفة طولية  متقطعة يعطي تي عشرةاألثن بزع;انف نفس;ه ألنب;وب ل %٢٠ح;والي بلحمل الطبيعي بدالل;ة مع;دل رق;م نس;لت بنس;بة أكب;ر أفضل ل ا

قورنت النتائج المقدّمة مع دراسة سابقة وأظهرت تقارباً ب بزعانف طولية مستمرة ومتقطعة. وألنابيمستمرة. أستنبطت عالقات عملية للتنبؤ بمعدل رقم نسلت 
  جيداً.