Heat transfer characteristics of looped parallel micro heat pipe

Abstract

With the increasing demand of high performance electronic devices, computer systems, integrated circuits (Ie) and microchips, the power densities in the electronic systems are increasing rapidly. Packaging and thermal management of electric equipments have become an important problem because of the increased power level and simultaneous miniaturization of the devices. It is very important to facilitate optimum cooling of electronic components in an electronic device because integrated circuit lifetime depends on it. An increasing market demand on powerful gadgets in smaller and smaller cabinets creates a trade off situation: either to enlarge the package to accept additional cooling or to sacrifice Ie lifetime. This is a great challenge in thermal design management. Among other cooling techniques heat pipe emerges a very effective and appropriate technology, also cost effective thermal design solution because of its excellent heat transfer capability, high efficiency and its structural simplicity. Thus application of heat pipe has expended gradually. Due to the space constraint in most of the personal computers and telecommunication devices, the size of heat pipes has to be carefully decided. So investigations on heat pipes are indispensable for further development and improvement of its performance. This experimental study has been performed to investigate the heat transfer . characteristics of looped parallel micro heat pipe (LPMHP). LPMHP consists of two single tube micro heat pipes of circular geometry having inner diameter of 1.8 mm and length of 150 mm placed parallel, connected by two U tubes of same diameter at the top and bottom ends. The experimental parameters are condenser inclination angle, heat input and properties of the working fluid. Taking acetone and ethanol as working fluids, heat transfer characteristics are determined experimentally for different condenser inclination angles at different heat inputs. An analysis of the experimental data gives the following results: Condenser inclination angle has a very little effect on the performance of LPMHP. Better performance is found for the vertical position of condenser. Heat input has significant effect on the performance of LPMHP. It is found that overall heat transfer coefficient is higher for higher heat input. Finally, it is observed that for the same heat input and condenser inclination angle LPMHP with acetone as working fluid performs better. An empirical correlation has also been developed which correlates all the experimental data within approximately "= 15% error.