This research is conducted with conditions as follows. The numbers of thermosyphon is 10, 20. 100 tube and the length of condenser section 80 cm and evaporator section 20 cm. The average
temperature of LCZ 80 °C and temperature of inlet air at condenser section are 20 °C. The simulation time is 3 hours.

600 500

%

400

о

.s

300

о

s

200

Ы

100 0

0 20 40 60 80 100 120

Number of tube

Fig.5.The relation between heat extraction and numbers of thermosyphon

Figure 8 is the result of heat extraction from the solar pond which is simulating at Khon Kaen province. As there are 100 tube thermosyphon, 22.22 mm. of outside diameter, the extracted heat is 560 W and the average temperature of the pond decreases from 80 to 78°C.

Tube dimeter(mm) Fig.6.The relation between the heat extraction from the solar pond and outside diameter of thermosyphon

According to the solar pond performance, the more the numbers of thermosyphon, more heat can be extracted with non-linearity. Because of when the number of thermosyphon increase, the thermal resistances, Zi and Z9, decrease. It is observed that the internal thermal resistance of thermosyphon has changed slightly due to the small temperature change that results the more heat can be extracted from solar pond because of the increasing in the numbers of thermosyphon.

0 1 •e § и a °w "o i/5

85 80 75 70 65 60

0 5 10 15 20 25 30 35 40

Tube dimeter(mm)

Fig.7.The relation between average solar pond temperature and thermosyphon diameter

Regarding to the simulation, there are 3 outside diameters of thermosyphon; 12.70, 22.22, 34.92 mm. From the figure 8, the outside diameters of thermosyphon are 12.70 and 34.92 mm. the heat extraction are 1,088 W and 351 W respectively. The average temperature of the pond decrease from 80 to 78 °C as shown in figure. 7.

When the diameter increases, more heat extraction will be gained. Even though the size is increased, the rate of change of heat has decreased because of the internal thermal resistance also decrease. However, from figure.10, the extracted heat from solar pond is relatively small compared with the increasing of thermosyphon diameter Therefore, in the economic aspect; it is not worth to increase the thermosyphon diameter just to gain smaller extracted heat. Thus, this model is able to determine the appropriate diameter of thermosyphon for solar pond heat extraction.

Fig.8.The relation between the heat extraction from the solar pond and mass flow rate heat pipe heat Exchanger

The effect of mass flow rate on heat transfer characteristics of a thermosyphon heat exchanger under normal operating conditions was investigated theoretically. The air face velocity ranged from 1 to 5 m/s and 70 tube thermosyphon the heat extraction are 202 W and 1,067 W respectively. As shown in figure.8

3. CONCLUSION

This research shows the simulation of heat extraction from solar pond at Khon Kaen Province in northeastern Thailand. The results show the capability of thermosyphon and indicate the optimum sizing of thermosyphon in solar pond application. Finally the simulation shows the theoretical possibility to use thermosyphon as the heat exchanger device to extract heat from solar pond.

Acknowledgements — This research was conducted under Rajamangala University of Technology Isan Khon Kaen Campus, Thailand. The authors would like to express their sincere appreciation for all of the support provided.

References

A. Akbarzadeh and G. Ahmadi (1980) Computer simulation of the performance of a solar pond in Southern part Iran, Solar Energy, Vol. 44, pp. 143-151

2. Huseyin Kurt, ethi Halici and A. Korhan Binark (1999) Solar pond conception — experimental and theoretical studies Energy Conversion & Management 41 (2000) pp.939­3. Hillel Rubin, and Barry A. Benedict (1983) Modeling the Performance of aSolar Pond as a Sourace of Thermal Energy Solar Energy Vol 32 No 6 pp. 771-778

4. J. RHull (1980), Computer simulation of solar pond thermal behaviour, Solar Energy, Vol. 25, pp. 33.

5. J. Andrewe and A. Akbarzadeh (2004) Enhancing the thermal efficency of solar ponds by extracting heat fram the gradient layer Solar Energy, 78 (2005) pp.704-716