## THERMAL SCIENCE

International Scientific Journal

### EVALUATION MODEL OF THE STEADY-STATE HEAT TRANSFER PERFORMANCE OF TWO-PHASE CLOSED THERMOSYPHONS

**ABSTRACT**

Two-phase closed thermosyphons have good thermal conductivity and are widely used in heat transfer applications. It is essential to establish an effective method for evaluating the steady-state heat transfer performance of two-phase closed thermosyphons, as such a method can help to select appropriate designs and to improve the efficiency of these devices. In this paper, the equivalent thermal conductivity is derived by the principle of equal total thermal resistance, in which the influence of the adiabatic length is eliminated. An evaluation model of the steady-state heat transfer performance of two-phase closed thermosyphons is established. Test results of three two-phase closed thermosyphons with total lengths of 220 mm, 320 mm, and 500 mm show that as the heat transfer rate increases, the equivalent thermal conductivity of these devices decreases by 28.91%, increases by 6.10% and increases by 10.02%, respectively, among which the minimum value is 831.63 W/mK and the maximum value is 1694.19 W/mK. The decrease (in-crease) in the equivalent thermal conductivity in the evaluation model indicates a decrease (increase) in the heat transfer performance. The results show that the equivalent thermal conductivity of the model can effectively evaluate the heat transfer performance of two-phase closed thermosyphons.

**KEYWORDS**

PAPER SUBMITTED: 2020-08-25

PAPER REVISED: 1970-01-01

PAPER ACCEPTED: 2021-04-09

PUBLISHED ONLINE: 2021-05-16

**THERMAL SCIENCE** YEAR

**2022**, VOLUME

**26**, ISSUE

**Issue 2**, PAGES [1367 - 1377]

- Noie, S.H., Heris, S.Z., Kahani, M., Nowee, S.M. Heat transfer enhancement using Al2O3/water nanofluid in a two - phase closed thermosyphon. International Journal of Heat and Fluid Flow ( 2009 ), 30, pp. 700 - 705.
- Noie, S.H. Heat transfer characteristics of a two - phase closed thermosyphon. Applied Thermal Engineering ( 2005 ), 25, pp. 495 - 506.
- Z hang, H., Zhuang, J. Research, development and indust rial application of heat pipe technology in China. Applied Thermal Engineering ( 2003 ), 23, pp. 1067 - 1083.
- Fadhl, B., Wrobel, L.C., Jouhara, H. Numerical modelling of the temperature distribution in a two - phase closed thermosyphon. Applied Thermal Engineering ( 2013 ), 60, pp. 122 - 131.
- Jafari, D., Di Marco, P., Filippeschi, S., Franco, A. An experimental investigation on the evaporation and condensation heat transfer of two - phase closed thermosyphons. Experimental Thermal and Fluid Science ( 2017 ), 88, pp. 111 - 123.
- Kafeel, K., Turan, A. Simulation of the response of a thermosyphon under pulsed heat input conditions. International Journal of Thermal Sciences ( 2014 ), 80, pp. 33 - 40.
- Wang, X., Wang, Y., Chen, H., Zhu, Y. A combined CFD/visualization investigation of heat transfer behaviors during geyser boiling in two - phase closed thermosyphon. International Journal of Heat and Mass Transfer ( 2018 ), 121, pp. 703 - 714.
- Ma, L., Yin, X., Shang, L., Ji, Z. Modelling of two - phase closed thermosyphon based on SINDA/FLUI NT. Applied Thermal Engineering ( 2018 ), 130, pp. 375 - 3 83.
- Aghel, B., Rahimi, M., Almasi, S. Heat - transfer enhancement of two - phase closed thermosyphon using a novel cross - flow condenser. Heat and Mass Transfer ( 2016 ), 53, pp. 765 - 773.
- Payakaruk, T., Terdtoon, P., Ritthidech, S. Correlations to predict heat transfer characteristics of an inclined closed two - phase thermosyphon at normal operating conditions. Applied Thermal Engineering ( 2000 ), 20, pp. 781 - 790.
- Esen, M., Esen, H. Experimental investigati on of a two - phase closed thermosyphon solar water heater. Solar Energy ( 2005 ), 79, pp. 459 - 468.
- Jiao, B., Qiu, L.M., Zhang, X.B., Zhang, Y. Investigation on the effect of filling ratio on the steady - state heat transfer performance of a vertical two - phase closed thermosyphon. Applied Thermal Engineering ( 2008 ), 28, pp. 1417 - 1426.
- Sukchana, T., Jaiboonma, C. Effect of Filling Ratios and Adiabatic Length on Thermal Efficiency of Long Heat Pipe Filled with R - 134a. Energy Procedia ( 2013 ), 34, pp. 298 - 306.
- Noie, S.H., Sarmasti Emami, M.R., Khoshnoodi, M. Effect of Inclination Angle and Filling Ratio on Thermal Performance of a Two - Phase Closed Thermosyphon under Normal Operating Conditions. Heat Transfer Engineering ( 2007 ), 28, pp. 365 - 371.
- Jafari, D., Filippeschi, S., Franco, A., Di Marco, P. Unsteady experimental and numerical analysis of a two - phase closed thermosyphon at different filling ratios. Experimental Thermal and Fluid Science ( 2017 ), 81, pp. 164 - 174.
- Huminic, G., Huminic, A., Morjan, I., Dumitrache, F. Experimental study of the thermal performance of thermosyphon heat pipe using iron oxide nanoparticles. International Journal of Heat and Mass Transfer ( 2011 ), 54, pp. 656 - 661.
- Sarafraz, M.M., Hormozi, F. Experimental study on the thermal performance and efficiency of a copper made thermosyphon heat pipe charged with alumina - glycol based nanofluids. Powder Technology ( 2014 ), 266, pp. 378 - 387.
- Sarafraz, M.M., Hormozi, F., Peyghambarzadeh, S.M. Thermal performance and efficiency of a thermosyphon heat pipe w orking with a biologically ecofriendly nanofluid. International Communications in Heat and Mass Transfer ( 2014 ), 57, pp. 297 - 303.
- Naphon, P., Assadamongkol, P., Borirak, T. Experimental investigation of titanium nanofluids on the heat pipe thermal efficien cy. International Communications in Heat and Mass Transfer ( 2008 ), 35, pp. 1316 - 1319.
- Khandekar, S., Joshi, Y.M., Mehta, B. Thermal performance of closed two - phase thermosyphon using nanofluids. International Journal of Thermal Sciences ( 2008 ), 47, 659 - 667.
- Yu, Z. - T., Xu, X., Hu, Y. - C., Fan, L. - W., Cen, K. - F. A numerical investigation of transient natural convection heat transfer of aqueous nanofluids in a horizontal concentric annulus. International Journal of Heat and Mass Transfer ( 2012 ), 55, pp. 1141 - 11 48.
- Bashir, A.I., Everts, M., Bennacer, R., Meyer, J.P. Single - phase forced convection heat transfer and pressure drop in circular tubes in the laminar and transitional flow regimes. Experimental Thermal and Fluid Science ( 2019 ), 109, p. 109891.
- Sarafraz, M.M., Hormozi, F., Peyghambarzadeh, S.M. Role of nanofluid fouling on thermal performance of a thermosyphon: Are nanofluids reliable working fluid. Applied Thermal Engineering ( 2015 ), 82, pp. 212 - 224.
- Moffat, R.J. Describing the uncertainties in experimental results. Experimental Thermal and Fluid Science ( 1988 ), 1, pp. 3 - 17.
- Arya, A., Sarafraz, M.M., Shahmiri, S., Madani, S.A.H., Nikkhah, V., Nakhjavani, S.M. Thermal performance analysis of a flat heat pipe working with carb on nanotube - water nanofluid for cooling of a high heat flux heater. Heat and Mass Transfer ( 2017 ), 54, pp. 985 - 997.
- Sarafraz, M.M., Pourmehran, O., Yang, B., Arjomandi, M. Assessment of the thermal performance of a thermosyphon heat pipe using zirconia - ace tone nanofluids. Renewable Energy ( 2019 ), 136, pp. 884 - 895.