Browsing by Subject "Thermal performance"

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Open Access
Effect of design and operating parameters on the thermal performance of aluminum flat grooved heat pipes
(Elsevier, 2018-03-05) Alijani, Hossein; Çetin, Barbaros; Akkuş, Y.; Dursunkaya, Z.
Four aluminum flat grooved heat pipes with groove widths of 0.2, 0.4, 0.8 and 1:6 mm are fabricated and the effect of filling ratio on the thermal performance is experimentally studied for four different heat flux values of 2.1, 3.2, 4.2 and 5:3W=cm2. An optimum filling ratio corresponding to each heat flux is determined where the heat pipe has the best thermal performance. Thermal performance of the heat pipes are evaluated using three indicators; (i) the temperature difference between the heat source and heat sink surfaces, (ii) the temperature difference between the peak system temperature and the temperature of the cooling ambient and (iii) heat pipe effectiveness defined as a temperature difference ratio under dry and operating conditions. A flow and evaporative mass scaling model is developed to interpret the experimental findings. Experimental results reveal that at the optimum point the heat pipe with the 0:4 mm groove width has the best thermal performance, and the heat pipe with the smallest 0:2 mm groove operates under dryout conditions even for the lowest heat flux, the reason of which is discussed based on interpretation of underlying phase change physics. Experiments reveal the existence of two operating regimes; with and without dryout in the grooves. Although higher heat loads can be carried under dryout conditions, a limit exists for the maximum heat flux where the pipe operates without the onset of dryout for a specific groove density.
Open Access
Thermal performance characterization of flat grooved heat pipes
(2017-07) Alijani Alijanvand, Hossein
Heat pipes are promising heat removal devices widely used in a variety of elds ranging from thermal management of electronic components to terrestrial and aerospace applications. Their working principle, phase change of a working uid, makes them superior to other conventional cooling methods. This thesis study focuses on at grooved heat pipes and the e ects of working uid, lling ratio, groove density, and input heat ux on their thermal performance are investigated. During the study, two aluminum heat pipe generations and one silicon heat pipe con guration, each having a set of di erent groove densities, are fabricated. In each set, di erent methods of heating and cooling are applied. In all the experiments on aluminum heat pipes, the working uid is isopropyl alcohol due to its wetting characteristics that makes it compatible with the aluminum surface. For the case of silicon, the heat pipes are charged with isopropyl alcohol and water. The optimum lling ratio, corresponding to the minimum temperature di erence along the heat pipe and maximum e ectiveness, is reported for each heat pipe. Moreover, as one of the operational limitations of heat pipes, the occurrence of dryout is visually observed and its extent is reported for each heat pipe operating at di erent lling ratios under di erent heat inputs. Furthermore, to nd the heat input to the heat pipes of rst generation and to simulate the phase change in one of the heat pipes of second generation, two 3-D computational models are developed and temperature distribution along the heat pipes are veri ed by the experimental results.