EXPERIMENTAL INVESTIGATION OF HEAT PIPE PERFORMANCE

للكاتبين :

Mahmoud A. El-Kady* , Hesham M. Mostafa **

and Alaa-Eldin. M. Ibrahim ***

* Faculty of Engineering, Al Azhar University, Cairo, Egypt.

** Higher Technological Institute, Tenth of Ramadan City, Egypt.

*** Research student

ABSTRACT

An experimental study of the performance of a thermosyphon heat pipe was conducted. An

apparatus equipped with the required measuring instruments was designed and constructed to

investigate the effects of applied heat flux, wall temperature in the evaporator section, filling

ratio and the geometry for the outer surface of the condenser section on the performance of

thermosyphon. Pure water was used as working fluid inside thermosyphon throughout this

work. Three samples having different geometries for the outer surface of the condenser

section was studied. These samples are knurled sample, longitudinal grooved sample and

plain sample. The evaporator section was heated by using dry saturated steam to adjust and

control the evaporator wall temperature. The condenser section enclosed a double pipe heat

exchanger. The experimental measurements of temperature, pressure and volume flow rate are

collected and manipulated to calculate the convection heat transfer coefficient for water flow

in the annulus of the double pipe heat exchanger. Also, boiling, condensation and overall heat

transfer coefficient for thermosyphon heat pip are determined.

The obtained experimental results show that, the average values for the wall temperatures of

evaporator section and condenser section were reduced for the knurled sample and

longitudinal grooved sample than the plain sample, It is noticed that, decreasing filling ratio

from 1 to 0.5 cause a decrease in the wall temperature for the evaporator section and an

increases in the wall temperature for the condenser section, It is found that the condenser wall

temperature was reduced for both knurled and longitudinal grooved samples than plain

sample. Also, the temperature difference between the evaporator and condenser walls was

reduced for the same heat flux. This leads to an increase in the thermal performance of

thermosyphon when using knurled and longitudinal grooved samples than plain sample.

Boiling curves for knurled sample and longitudinal grooved sample gave higher heat flux than

plain sample. There is a certain decrease in the overall thermal resistance of thermosyphon

when using knurled sample and longitudinal grooved sample compared with plain sample.

The overall thermal resistance decreases with increasing heat flux, and take lower values for

knurled sample and longitudinal grooved sample compared with plain sample.

For water flow in the annulus of the double pipe heat exchanger which enclose the condenser

section Nusselt number increases with increasing Reynolds number. Also, Nusselt number

takes higher values for knurled sample than longitudinal grooved sample and plain sample

Also , The heat transfer coefficient by boiling and condensation increased in case off grooved

samed than smooth sample.

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