Study on the vapor chamber with refrigerant R-141b as working fluid for HDD cooling

The heat within the operating drive is mainly generated by the SPM, VCM, magnetic read/write head sensor, and windage loss. Temperature is often quoted as the most important environmental factor affecting disk drive reliability. The results of the investigation on the thermal cooling of vapor chamber with refrigerant R-141b as working fluid for cooling hard disk drive are presented. It was found that the vapor chamber cooling technique has a significant effect on the thermal cooling of hard disk drive. At the optimum condition (20% fill ratio of working fluid) that results in minimum HDD temperature, average HDD temperatures of VC with refrigerant R-141b as working fluid are 10.73% and 23.37% lower than those with water as working fluid and those without VC, respectively. The results of this study are of technological importance for the efficient design of cooling systems of the personal computers or electronic devices to enhance cooling performance.     

On the thermal cooling of central processing unit of the PCs with vapor chamber

An experimental investigation on the thermal cooling of vapor chamber for cooling computer processing unit of the personal computer is performed. Two different configurations of the vapor chambers with de-ionized water as working fluid are tested under the real operating conditions of PCs. Parametric studies including different aspect ratios, fill ratios, and operating conditions of PC on the CPU temperature are considered. It was found that the vapor chamber cooling technique has significant effect on the thermal cooling of CPU. Average CPU temperatures obtained from the vapor chamber cooling system are 4.1%, 6.89% lower than those from the conventional cooling system for no load and 90% operating loads, respectively. In additional, this cooling system requires 6.89%, 10.53% lower energy consumption for no load and 90% operating loads, respectively. The results of this study are of technological importance for the efficient design of cooling systems of the personal computers or electronic devices to enhance cooling performance.     

Heat transfer and flow characteristics in the hard disk drive tester

The numerical results of the heat transfer and flow characteristics in the hard disk drive tester are presented. The testing of the hard disk drive with keeping drives within the normal and high temperatures in the tester has been introduced as one of the manufacturing processes of the hard disk drive. The cooling air entering the tester is induced by the 10 axial fans into the tester and is impinged the hard disk drives and then discharged to the atmosphere. The k–ε standard turbulent model is applied to analyze the model. The results obtained from the model are verified by comparing with the measured data. Reasonable agreement is obtained from the comparison between the results obtained from the model and those from the experiment. The numerical results show that the flow and temperature distribution of cooling air are not uniformed. Which none-uniform temperature and accumulated heat are significantly factors to the failure of the hard disk drives. The results of this study are of technology importance for the efficient design and/or approved hard disk drive tester to decrease hard disk drive failure.     

The experimental and numerical investigation of a grooved vapor chamber

An effective thermal spreader can achieve more uniform heat flux distribution and thus enhance heat dissipation of heat sinks. Vapor chamber is one of highly effective thermal spreaders. In this paper, a novel grooved vapor chamber was designed. The grooved structure of the vapor chamber can improve its axial and radial heat transfer and also can form the capillary loop between condensation and evaporation surfaces. The effect of heat flux, filling amount and gravity to the performance of this vapor chamber is studied by experiment. From experiment, we also obtained the best filling amount of this grooved vapor chamber. By comparing the thermal resistance of a solid copper plate with that of the vapor chamber, it is suggested that the critical heat flux condition should be maintained to use vapor chamber as efficient thermal spreaders for electronics cooling. A two-dimensional heat and mass transfer model for the grooved vapor chamber is developed. The numerical simulation results show the thickness distribution of liquid film in the grooves is not uniform. The temperature and velocity field in vapor chamber are obtained. The thickness of the liquid film in groove is mainly influenced by pressure of vapor and liquid beside liquid–vapor interface. The thin liquid film in heat source region can enhance the performance of vapor chamber, but if the starting point of liquid film is backward beyond the heat source region, the vapor chamber will dry out easily. The optimal filling ratio should maintain steady thin liquid film in heat source region of vapor chamber. The vapor condenses on whole condensation surface, so that the condensation surface achieves great uniform temperature distribution. By comparing the experimental results with numerical simulation results, the reliability of the numerical model can be verified.     

Effects of shield on thermal-fluid performance of vapor chamber heat sink

This work investigates the effects of a shield on the thermal and hydraulic characteristics of plate-fin vapor chamber heat sinks under cross flow cooling. The surface temperature distributions of the vapor chamber heat sinks are measured using infrared thermography. The thermal-fluid performance of vapor chamber heat sinks with a shield is determined by varying the fin width, the fin height, the fin number and the Reynolds number. The experimental data thus obtained are compared with those without a shield.Experimental results indicate that the maximum surface temperature of the vapor chamber heat sink is effectively reduced by adding the shield, which forces more cooling fluid into the inter-fin channel to exchange heat with the heat sink. However, using the shield increases the pressure drop across the heat sink. The experimental data also show that the enhancement of the heat transfer increases with the Reynolds number, but the improvement declines as the Reynolds number increases. When the pumping power and heat transfer are simultaneously considered, vapor chamber heat sinks with thinner, higher or more fins exhibit better thermal-hydraulic performance.     

Thermal cooling enhancement techniques for electronic components

Due to highly effective thermal spreaders, the vapor chambers have been widely applied on the electronic cooling. An effective thermal spreader can achieve more uniform heat flux distribution and thus enhance heat dissipation of heat sinks. This work investigates the thermal performance characteristics plate-fin vapor chamber. Parametric studies including different operating operation of CPU, coolant types, working fluids, filled ratios, flow direction of coolants, heat sink configurations, and the effect of the relevant parameters on the cooling performance in terms of the thermal resistance was considered and discussed. The results showed that the relevant parameters have a significant influence on the thermal resistance of the vapor chamber.     

Thermal performance of flat vapor chamber heat spreader

Experiments were performed to examine the spreading thermal resistance of centrally positioned heat sources and the thermal performance of a water charged, gravity assisted flat vapor chamber to be used for electronic cooling. Parametric studies including different heat fluxes and operating temperatures were conducted, and the effect of the relevant parameters on the cooling performance in terms of the spreading resistance was presented and discussed. The present vapor chamber heat spreader showed a heat removal capacity of 220 W/cm² with a thermal spreading resistance of 0.2 °C/W.     

Development of an OAPCP-micropump liquid cooling system in a laptop

An innovative one-side actuating piezoelectric micropump (OAPCP-micropump), which is combined with a 45 mm × 28 mm × 4 mm cold plate chamber, has been developed to drive liquid in a cooling system for a laptop. The results show that the shape and the numbers of the fins inside the cold plate chamber have strong effects on the pressure drops and flow profiles. The fluid in the pump chamber may impinge on the fins and increase the heat dissipation rate due to the oscillation by the actuator. The measured maximum flow rate of the OAPCP-micropump is 4.1 ml/s, and its maximum pump head reaches 9807 Pa. The new cooling system with an OAPCP-micropump design shows a stable performance on total thermal resistance due to the high flow rate.     

A State-of-the-Art Review of Compact Vapor Compression Refrigeration Systems and Their Applications

We present a critical review of the literature on the fundamentals, design, and application aspects of compact and miniature mechanical vapor compression refrigeration systems. Examples of such systems are those envisaged for electronics and personal cooling. In comparison to other refrigeration technologies (e.g., solid-state), vapor compression enables the attainment of low evaporating temperatures while maintaining a large cooling capacity per unit power input to the system. Over the past decade, there have been a significant number of studies devoted to the miniaturization of system components, with the most critical being the compressor. When compared with competing cooling technologies, such as flow boiling in microchannels, jet impingement, and spray cooling, refrigeration is the only one capable of lowering the junction temperature to values below the ambient temperature. The combination of vapor compression refrigeration with the aforementioned technologies is also possible, necessary, and beneficial, since it increases greatly the potential for reducing the system size. For each main application, this paper sheds some light on the thermodynamic and thermal aspects of the cooling cycle and on recent developments regarding its components (compressor, heat exchangers, and expansion device). Whenever appropriate, issues and challenges associated with the different cycle designs are addressed. An overview of the ongoing efforts in competing technologies is also presented.     

Heat transfer characteristics of high heat flux vapor chamber

To meet the challenge of heat spreading in electronic products, highly efficient high heat flux heat transfer vapor chambers have been manufactured and their heat transfer characteristics have been studied by a fast test system. A solid copper block with the same shape as the vapor chamber is used to compare the performance of the vapor chamber. The result shows that, it will take about 5 min to achieve a steady state in the fast test system. The heat transfer characteristics of the vapor chamber are more superior to those of the copper block. In this paper, total thermal resistance of the test system is used to evaluate the heat transfer characteristics of the vapor chamber, because it has already been used to consider both the spreading thermal resistance and the flatness of the vapor chamber.     

Heat transfer characteristics of high heat flux vapor chamber

To meet the challenge of heat spreading in electronic products, highly efficient high heat flux heat transfer vapor chambers have been manufactured and their heat transfer characteristics have been studied by a fast test system. A solid copper block with the same shape as the vapor chamber is used to compare the performance of the vapor chamber. The result shows that, it will take about 5min to achieve a steady state in the fast test system. The heat transfer characteristics of the vapor chamber are more superior to those of the copper block. In this paper, total thermal resistance of the test system is used to evaluate the heat transfer characteristics of the vapor chamber, because it has already been used to consider both the spreading thermal resistance and the flatness of the vapor chamber.     

Thermal performance of plate-fin vapor chamber heat sinks

Since vapor chambers exhibit excellent thermal performance, they are suited to use as bases of heat sinks. This work experimentally studies the thermal performance of plate-fin vapor chamber heat sinks using infrared thermography. The effects of the width, height and number of fins and of the Reynolds number on the thermal performance are considered. Experimental data are compared with corresponding data for conventional aluminum heat sinks. The results show that generated heat is transferred more uniformly to the base plate by a vapor chamber heat sink than by a similar aluminum heat sink. Therefore, the maximum temperature is effectively reduced. The overall thermal resistance of the vapor chamber heat sink declines as the Reynolds number increases, but the strength of the effect falls. The effect of the fin dimensions on the thermal performance is stronger at a lower Reynolds number. At a low Reynolds number, a suitable number of fins must be chosen to ensure favorable thermal performance of the vapor chamber heat sink. However, at a high Reynolds number, the thermal performance improves as the fin number increases.     

Numerical simulation of a heat sink embedded with a vapor chamber and calculation of effective thermal conductivity of a vapor chamber

This study presents a numerical investigation of a whole set of thermal module, including a plate-fin heat sink embedded with a vapor chamber, subject to the influence of concentrated heat sources. Within the vapor chamber, the internal vapor is assumed as a common heat-transfer interface between the wicks. CFD simulations of the integrated heat sink are carried out with this assumption. The calculated results are in good agreement with the experiments, and show a maximum difference of 6.3% for the hotspot temperature rises. It is found that the area of the heat source has an important influence to the performance of the vapor chamber. The major spreading resistance of the vapor chamber comes from the bottom wall, where a concentrated heat source is applied. In addition, the isotropic and orthotropic approaches are proposed to calculate the effective thermal conductivities of the vapor chamber. By approximating the vapor chamber as a conduction plate, the effective conductivity can be obtained from the analytical solutions of the spreading resistances. The vapor chamber can reduce the spreading resistances sufficiently by its excellent lateral thermal spreading effect, which can be interpreted by the orthotropic approach.     

适度隔热发动机的发展

适度隔热发动机的概念是指对燃烧室等主要受热零部件采取隔热措施处理,如此燃烧室表面向冷却水的传热减少,可以显著减小发动机冷却系统的整体尺寸。对表面隔热技术和适度隔热技术对发动机性能的影响进行了介绍和分析;并探讨了适度隔热发动机的发展方向。     

Heat Transfer Augmentation of a Co-Rotating Disk Assembly with Special Emphasis on the Lower Disk

Experiments were performed to map local heat transfer coefficients on an unobstructed co-rotating disk system simulating the internal component of a computer disk drive assembly. The disk diameter was twice as large as a hard drive, and the rotational speed up to 5000 rpm was studied. The effects of two parameters, on the heat transfer phenomena the Reynolds number from 6.587 × 10 ⁴ to 3.096 × 10 ⁵ and the non-dimensional disk-to-disk ratio (L/D) from 0.02 to 0.06, were observed. The disks were positioned horizontally, and heat transfer was measured for the top faces of both disks. Emphasis is given to the top face of the lower disk in this research, as less experimental data are available in the literature. A transient liquid crystal technique was employed for the measurements, and the results reveal an interesting pattern of the heat transfer rate in the gap for the upper surface of the lower disk. The overall heat transfer is much lower for the surface of the lower disk as compared to that of the top disk. The maximum average heat transfer rate was established to be at L/D = 0.04 for the case with the highest rotational speed.     

Design and testing of a four-phase fault-tolerant permanent-magnet machine for an engine fuel pump

This paper discusses the design and testing of an aircraft electric fuel pump drive. The drive is a modular, four-phase, fault-tolerant system which is designed to meet the specification with a fault in any one of the phases. The motor employed has a permanent-magnet rotor with the magnets arranged in a Halbach array to maximize the air-gap flux density. Exceptionally high electric loadings are obtained by flooding the entire motor with aircraft fuel, which acts as an excellent cooling agent. Theoretical results are compared with test results gained in conditions approaching those found in an aircraft. Tests are carried out on the unfaulted drive and with one of several fault scenarios imposed. The electrical and thermal performance of the drive is assessed, showing how the flooded fuel cooling has excellent performance without introducing significant drag on the rotor.     

Feasibility study of a vapor chamber with a hydrophobic evaporator substrate in high heat flux applications

A novel vapor chamber was fabricated to assess the feasibility of combining hydrophobic and hydrophilic wettabilities in the evaporator to optimize thermal performance. The proposed vapor chamber included a separate layer of hydrophilic sintered copper powder wick that was pressed in intimate contact with a hydrophobic evaporator substrate with a water contact angle around 140°. The contact between the wick layer and the evaporator was provided by sixteen posts implemented on the condenser, which pushed the wick layer toward the evaporator. The thermal performance was evaluated based on the thermal resistance, source temperature, and temperature uniformity across the condenser. Results were compared with those of a baseline vapor chamber that was fabricated by sintering hydrophilic copper particles on a hydrophilic copper evaporator substrate. The wick size and the copper powders used to fabricate the wick structure were the same in both vapor chambers. Overall, the performance of the proposed vapor chamber was lower than that of the baseline vapor chamber, possibly due to microscale gaps between the wick layer and the evaporator substrate. However, the concept of using a hydrophilic wick to force liquid in contact with a hydrophobic evaporating surface could enable a new family of vapor chambers with low thermal resistance, if more efficient techniques for improving the mechanical contact between the wick layer and the evaporator are introduced through further detailed research. If successful, the fabrication cost of vapor chambers would be reduced as well, by using prepared wick structures, which do not require high-temperature sintering processes on evaporators.     

Numerical investigation on the electronic components' cooling for different coolants by finite element method

In this study, we conducted a numerical simulation to examine the cooling performance of an aluminum finned heat sink attached to a silicon chip, placed in a chamber of a rectangular cross-section. The heat sink is cooled by convective heat transfer utilizing nine commercially available gaseous coolants, namely air, hydrogen, helium, nitrogen, oxygen, carbon dioxide, freon12 vapor, propane, and ammonia. To select an appropriate coolant for electronic devices in terms of thermal–hydraulic performance, the maximum temperature on the chip domain and the associated pressure drop in the cooling channel as a function of coolant velocity are analyzed for the aforementioned fluids. It has been found that the minimum temperature is recorded for propane and freon12 vapor, which is approximately 31.1°C, for a coolant velocity of 0.5 m/s, but freon12 vapor shows the highest pressure drop, approximately 900 mPa, among all coolants. In the overall velocity regime, hydrogen shows the best cooling performance in terms of both cooling capacity and hydrodynamic characteristics. But considering safety issues, helium can be a better alternative. This comprehensive study provides a better understanding of different coolant performances, which will aid engineers to develop an effective cooling technique to accommodate the inexorably rising power demand.     

Temperature distribution of read/write head soldering with ribbon cable of HDD

In the present paper, the temperature distribution of the read/write head soldering with the ribbon cable of the HDD is presented. The soldering of the actuator/connector with the ribbon cable can be performed either by manual or semi-automatic process which has been introduced as one of the manufacturing processes of the HDD. Finite element analysis is applied to analyze the model. The properties of the soldering ball and boundary conditions have significant effects on the thermal stress and localized heat in the soldering process that cause the failure of the ribbon cable of the HDD. The results of this study are of technological importance for the efficient design and/or approval of the soldering HDD process to reduce yield loss of the hard disk drive.     

Performance of a heat pipe assisted night sky radiative cooler

A passive radiative cooling system was designed, constructed and tested under clear skies. This refrigerator operates by losing heat to the night sky through infrared (i.r.) radiation emission. It consists of a radiator, an array of heat pipe elements and a cold chamber. The heat pipe elements are so arranged that they act as thermal diodes, transferring heat from the cold chamber to the radiator. Performance tests show that the system has a cooling capacity of 628 kJ/m² per night with a sky coefficient of performance of 0.26. The lowest temperature attained in the cold chamber was 12.8°C for an ambient temperature of 20°C. The overall results indicate that the system has a great potential for providing a cold storage facility in developing countries and in remote areas.