2. Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
http://www.iaeme.com/IJMET/index.asp 121 editor@iaeme.com
Figure 1 Aerogel blanket (5mm thick)
2. MANUFACTURING DETAILS
The primary raw materials used in the manufacture of the proposed insulated bottle
are stainless steel (AISI 304).
A satisfactory insulating effect is achieved with double-walled flasks of stainless
steel (AISI 304), because it has a low thermal conductivity coefficient of
approximately 14.9 W/(mK) at 20° C. For production reasons it is necessary to carry
out welding of individual stainless steel flasks lengthwise. The aerogel blanket
between the two flasks results in a considerable improvement of the insulating
capability. Flasks with a double wall and an aerogel blanket in the space between the
double walls increase the insulating effect.
To obtain a double-walled flask with blanket in between, deep drawing process is
used for generating the model. The inner bottle (SS1) is fixed within the outer bottle
(SS2) and sealed therewith at its upper end by welding, to form a double-walled
model with the insulating material between the two bottles, to minimize transfer of
heat. A bottom cap is fixed on the bottom of the outer bottle to protect the extra part
during manufacturing.
Figure 2 Section view & 3-D Model of Bottle
The oxide layers on the wall surfaces adjoining the space between two bottles are
provided to improve insulating properties, i.e. an outer surface of the inner bottle and
an inner surface of the outer bottle. It is adequate for the practical use to provide a
silver mirror layer only on the outer surface of the inner bottle instead of applying on
complete oxide layer. This indirectly contributes to reduce the cost of the proposed
bottles. When the cap is opened, i.e. it is in direct contact with the atmosphere,
Aerogel Blanket
Inner bottle-SS1
Outer bottle-
SS2
3. Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S. Charif D’ouazzane And Bianpambe H. W
http://www.iaeme.com/IJMET/index.asp 122 editor@iaeme.com
maximum heat transfer takes place through the neck and opening of the flask. Thus
elongated conduit is created, in order to minimize the heat flow through the neck tube.
As the length of the access conduit or neck tube is increased, it reduces the heat leak.
However, this approach is limited by structural considerations.
The outer cup is made of a sheet of stainless steel. Next, the insulating material is
added in the cup along with the liner. Lastly steel bottles are then painted.
3. DISCUSSION
Looking on the negative side of vacuum insulation bottles, as the furnaces are never
turned off, the workload of these machines is considerable and can reach 8.7 hours of
operations per year. It is therefore very important to have highly reliable vacuum
pumps and require little maintenance and low energy consumptions. For example, for
the operation of a line with 16 sections, a pump with a suction capacity of 700m3
/h is
normally used. Despite to their easy installation and low purchase cost, they are
dramatically expensive in operation, due to compressed air compression.
For testing the proposed model, a test was carried out. The bottle was filled with
boiling water, stoppered with a plug after the water being at 100° C., and then allowed
to stand for 6 to 24 hours at 27°C ambient temperature.
3.1 Mathematical Model
Considering the dimension for 1 liter bottle as-
Inner radius of bottle, r1 =0.0365m; Thickness of steel used =0.001m
Thickness of insulating material =0.005m; Length of inner bottle, L =0.225m
Required surface area of aerogel blanket = 2πrh + πr2
= 0.0697m2
Convective heat transfer for air, h2= 10W/m2
K
Convective heat transfer for water, h1= 100W/m2
K
Thermal coefficient for conduction of steel (AISI 3014), Ks at 100°C is = 16.3
W/mK; & at 27°C is = 14.9 W/mK
Table 1 Thermal Properties of Aerogel Blanket
T[°C] K[W/m.K] Cp[J/kg.K]
-50 0.0130 637
0 0.0141 864
10 0.0151* 893
20 0.0155* 931*
40 0.0160* 1000
100 0.0183 1150
150 0.0231 1234
According to Fourier’s law of heat conduction for heat transfer through the
cylindrical layer can be expressed as:Qcond, cyl. = - kA in W (1)
Where A = 2πrL is the heat transfer area at location r. As A depends on r, thus it
varies in the direction of heat transfer. Separating the variables in the above equation
and integrating from r = r1, where T (r1)= T1, to r = r2, where T(r2) =T2, gives:
= - (2)
Substituting A = 2πrL in equation (2) and performing integration we get
Qcond.cyl. = (3)
4. Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
http://www.iaeme.com/IJMET/index.asp 123 editor@iaeme.com
Where Rtotal = Rcylinder surface + Rcylinder base (4)
And
1) Rcylinder surface = ; is the thermal resistance of the cylindrical layer against
heat conduction, or conduction resistance. Thus the thermal resistance network for
heat transfer through the three layered composite cylinder (i.e. bottle: SS1-Blanket-
SS2) subjected to convection on both sides is given as:
Figure 3 Schematic showing layers of the bottle
Rcyl.surface total = Rconv,1+ Rcyl,1+Rcyl,2+Rcyl,3+Rconv,2
= (5)
Equation (5) represents total resistance offered to the heat flow i.e. convective
heat transfer of water, conduction resistance of curved surface and convective heat
transfer of air (surrounding) respectively. Thus substituting the values of variables in
equation (5) and finding the values of heat transfer through the curved surface.
2.) Rcyl. Base = ; is the thermal resistance of the wall against heat conduction.
Note that the thermal resistance of the medium depends on the geometry and the
thermal properties of the medium. The thermal resistance network for heat transfer
through the three layered composite cylinder (i.e. bottle: SS1-Blanket-SS2) subjected
to convection on both sides is given as:
Rcyl.base total = Rconv,1+ Rb1+Rb2+Rb3+Rconv,2
= (6)
Figure 4 #
Schematic of base of the bottle (#
Concept behind the base of bottle i.e. SS1-
blanket-SS2)
5. Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S. Charif D’ouazzane And Bianpambe H. W
http://www.iaeme.com/IJMET/index.asp 124 editor@iaeme.com
Equation (6) represents total resistance offered to the heat flow i.e. convective
heat transfer of water, conduction resistance of curved surface and convective heat
transfer of air (surrounding) respectively. Where A = area of base & L1, L2, L3 are
the thickness of SS1, blanket, SS2 respectively. Now substituting the values of
variables in equation (6) and finding the values of thermal resistance. Thus replacing
the values of resistances we get Rtotal and thereafter Qcond.cyl. The value obtained for
heat transfer has the unit J/sec. Thus we get heat transfer after 1hour. The value of
heat regained by water will be heat power available for the next hour calculations and
so on.
Similar calculations were done for water at 0°C and the results are plotted on the
graph.
4. RESULT
The result of 3-D model is shown in the figure 5, which shows the temperature
variation with the thickness of the bottle. It can be seen that aerogel blanket provides a
good insulation as there is insignificant change in temperature of outer surface (SS2).
Figure 5 Thermal analysis of 3-D model at high temperatures
Figure 6 Graph showing the variation in temperature of proposed model verses time
0
10
20
30
40
50
60
70
80
90
100
0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.511.512.513.514.5
Temperature[°C]
Time [hr]
Temperature v/s Time
for water @100C
for water @0C
6. Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
http://www.iaeme.com/IJMET/index.asp 125 editor@iaeme.com
After the analysis was done, result was generated and the following graph was
obtained showing change in temperature verses time. It is clearly seen that the
temperature of water if kept at 100°C in bottle, after 1 hour is 90°C, after 6 hours is
60°C and after 12 hours it comes down to 40°C. This is indicated with the blue line.
The red line indicates the temperature change of chilled water with respect to time.
After 1 hour the temperature rises to 4°C, after 6 hours is 15°C and after 12 hours is
20°C.
5. CONCLUSION
Thus the innovation proposed above relates to an insulated vessel which is
manufactured at low cost i.e. Rs350/-, has appreciable insulating capabilities and
excellent volumetric efficiency, and which may also be suitably employed in a
thermos, cooler, icebox, insulated cup, thermal insulated lunch box, thermal insulated
electric pot, heat retaining rice cooker, or as an insulating layer in a bath tub. Being
manufactured at low cost compared to the commercially existing model, the selling
price will be much lower in comparison with vacuum flask. The proposed model can
be used by the people having low budget but intend to enjoy appreciable quality of
bottle or any above stated application.
The manufacturing of this bottle also requires lesser energy during manufacturing
which contributes to the cost effectiveness of the model. As the maximum allowable
temperature is 473K, so it will accomplish our purpose; if brought into practice.
REFERENCES
[1] A.F. Hasobee, Y.K. Salman, Natural convection Heat Transfer inside inclined
Open Cylinder, International Journal of Mechanical Engineering and
Technology, 5(11), Nov 2014, pp.92-103.
[2] Yunus A. Cengel, Heat and Mass Transfer, 5th edition, McGraw Hill Higher
education.
[3] H. Ishizaki, R. Taguchi, Zojirushi Vacuum Bottle Co.Ltd, Method of making a
stainless steel vacuum bottle with a silver mirrored surface, Patent-US4856174 A,
15-Aug-1989.
[4] M. Komeda, M. Fujiyama, Zojirushi Vacuum Bottle Co. Ltd, Stainless steel
thermos bottle, Patent-US4427123 A, 24-Jan-1984.
[5] A. Kitabatake, A. Kamata, K. Nishikawa, M. Fujiyama, I. Kawamto, Zojirushi
Corporation, Vacuum-insulated, doubled-walled metal structure and methods for
its production, Patent-US4997124A, 5-Mar-1991.
[6] F.P. Incropera, D.P. Dewitt, Fundamentals of heat and mass transfer, 7th
edition,
New York/USA: J. Wiley & Sons
[7] Warren M. Rohsenow, James P. Hartnett, Y.I. Cho, Handbook of heat transfer,
3rd
edition, McGraw-Hill
[8] Frank Kreith, R.J. Manglik, Mark S. Bohn, Principles of Heat Transfer, 7th
edition, Cengage Learning Inc.
[9] J.P. Holman, Experimental methods for engineers, 8th
edition, McGraw-Hill
series in Mechanical Engineering, 2011.
[10] Ashish Kumar, Dr. Ajeet Kumar Rai and Vivek Sachan, An Experimental Study
of Heat Transfer In a Corrugated Plate Heat Exchanger, International Journal of
Mechanical Engineering & Technology, 5(9), 2014, pp. 286 - 292.
