Cylindrical heat pipes for the cooling digital light processing projector | |
| Author | Narong Pooyoo |
| Call Number | AIT Diss. no.ET-15-01 |
| Subject(s) | Heat pipes Lighting |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Energy |
| Publisher | Asian Institute of Technology |
| Abstract | Electronic devices use heat pipes to transfer heat efficiently and help in the miniaturization of these devices. The application of cylindrical he at pipes for cooling Digital Light Processing (DLP) projector can improve heat transfer, sa ve space, reduce noise and weight of the DLP projector, and is the topic of this research. Accordingly, the specific objectives of the study were: to study the performan ce of cylindrical heat pipes by numerical modeling and simulation studies using pure water and nanof luid as working fluids and including non- condensable gas effect; to desi gn, fabricate and to experimental ly investigate a cylindrical heat pipe for cooling a DLP projector (a Digital Micro mirror De vice (DMD) and a Ultra High Performance (UHP) lamp) and compare its actual performance with simulation results. To achieve the above noted objectives, earlier st udies were first reviewed. Heat pipes are not used commonly for cooling DLP projectors. The main steps of design and construction of heat pipes were: problem specifi cation, selection of liquids ma terials and wick structure, application of design procedures, finding optio nal solutions and evaluation of performance. The performance of cylindrical heat pipe can be evaluated by considering the thermal resistance of the outer wall temperature di stribution along the cylinder. The outer wall temperatures obtained by numerical simulatio n is in good agreement with experimental observation at the evapor ator. However, difference is observe d at the condenser section. It is also observed that the cylindrical heat pipe using pure water as work ing fluids shows the velocity vector inside cylindrical heat pipe differ from values obtained using the principles of heat pipe operation. Besides, ve locity vector and pressure pr ofile for nanofluid thermosyphon heat pipe is not available, and the simulati on results considering non-condensable gas effect are different from those obtained from the ex perimental results. These research gaps are therefore addresse d in this study. A numerical model was develope d considering pure water as th e working fluid taking into account the non-Darcian transport in liquid-vapor domain and ma ss flow rate at liquid-vapor interface domain. Then, this model was extended to nanofluid and non-condensable gas effect of cylindrical heat pipe using CFD commercia l software. A 3D numerical simulation on pure water and nanofluid including non-condensab le gas mixture considering non-Darcian transport and mass flow rate at liquid-vapor interface model was conducted and the results show that they are in good agreement with ea rlier analytical and e xperimental results. The velocity vector and pressure pr ofile inside cylindric al heat pipe also are in good agreement with the principle of heat pipe operati on. These models (considering pure water and nanofluid) were therefore used to design cylindr ical heat pipe for cooling DLP projector. An experimental setup to study the thermal resi stance of cylindrical heat pipe for cooling DLP projector considering R134a, pure water and nanofluid and non-condensable gas effect was fabricated. Experiments were conducted to (a) ev aluate the performance of cylindrical heat pipe and to show th e junction temperature of DMD (to be less than 60 Ԩ and UHP lamp less than 118 Ԩ ) using natural convection, (b) compare the performan ce of cylindrical heat pipe considering water, nanof luid and the effect of non-c ondensable gases considering ambient temperature and inclinat ion variation (to simulate the projector inclination and the projector operation in different ambient temper ature), (c) investigate the performance of DLP projector working with cylindri cal heat pipe, and (d) evaluate the effect on luminance on projector screen and power consumption usin g cylindrical heat pi pe. The experimental apparatus has rectangular tunnel feature, which can measure th e temperature distribution on the outer wall of cylindrical h eat pipe, junction temperature of DMD and UHP lamp and heat sink temperature. Four types of experiments were conducted using: R134a (for cooling DMD), pure water, nanofluid (for cooling UHP lamp) and non-condensable gas. Two plate heaters were inserted in the heating block to simulate heat source from DMD and UHP lamp of DLP projectors. The power s upply to the heaters wa s controlled by using an inverter. They were set to provide maximum power input of 47 W for UHP cooling and 8 W for DMD cooling. The surface temperature of heating bl ock (to simulate the ju nction temperature of UHP and DMD) was also measured under power supply changes and ambient temperature changes. Thermal resistance of cylindrical heat pipe in the four cases was obtained from measurements of the outer wall temperature. R134a cylindrical heat pipe-heat sink was then mounted on a DMD and two types of cylindrical heat pipes (pure water and nanofluids) were integrated to UHP lamp for evaluation of the cylindrical heat pipe combined with the DLP projector. Besides, the inte rface temperature between UHP lamps and heating block and between DMD and heating block, power consumption and illumination on screen of DLP projector, were also investigated. The study results show that two L-shaped cylindr ical heat pipes with screen mesh wick and one L-shaped cylindrical heat pipe with screen mesh wick using copper container are suitable for cooling 47 W UHP lamp and 8 W DMD, re spectively. The numerical simulation results of the outer wall temperatur e distribution considering R134 a, pure water and nanofluids cylindrical heat pipes agrees well with experimental re sults. Among the water-copper, nanofluid-copper and non-condensable gas mixt ure in cylindrical he at pipes, nanofluid- copper cylindrical heat pipe has the lowest th ermal resistance, while the non-condensable gas cylindrical heat pipe has th e highest thermal resistance. The two water-copper and two nanofluid-copper cylindrical heat pipes can ma intain the surface temperature of the heating block (to simulate UHP lamp junction temperature) at 80 Ԩ and 82 Ԩ , respectively and the R134a-copper cylindrical heat pipe can control surface temperature heating block (to simulate DMD junction temperature) below 60 Ԩ . The outer wall temp erature of nanofluid- copper cylindrical heat pipe, water cylindric al heat pipe and the non-condensable gas cylindrical heat pipe tend to decrease with le ss inclination, higher ambient temperature and higher heat inputs. For the projector, the wa ter cylindrical heat pi pe has the UHP lamp junction temperature (99 Ԩ ). The R134a-copper cylindrical heat pipe for cooling DMD can maintain DMD junction temperature at 41 Ԩ, below the existing cooling system. The electricity consumption and luminosity of water-coppe r cylindrical heat pipe is similar to that of the existing cooling system. The lifetime of UHP lamp and DMD in DLP projector is increased. Therefore, the cylindrical heat pipe ca n be used instead of fan and can also lead to miniaturization of projector. |
| Year | 2015 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Kumar, S. |
| Examination Committee(s) | Athapol Noomhorm ;Salam, Abdul |
| Scholarship Donor(s) | National Science and Technology Development Agency (NSTDA), Thailand |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2015 |