•Heat and mass transfer performances of small size Closed Loop Two Phase Thermosyphons.•Evaluation of the systems in connection with renewable energy systems applications.•Experimental analysis on a ...new test rig using water and ethanol as working fluid.•Analysis of the influence of heat load, operating pressure and filling ratio.•Heat transfer analysis in evaporator and condenser.
The authors have designed and realized an experimental test rig for the analysis of Closed Loop Two Phase Thermosyphons (CLTPT) of small dimensions where heat flow rate up to 1.7kW can be furnished. The experimental test rig consists of an evaporator and a water cooled horizontal condenser placed about 1m over the evaporator. The main characteristic of this apparatus is the presence of three different ways of measuring the mass flow rate: a continuous mode, an integral mode and an indirect mode.
The purpose of this analysis is to investigate the correlation between mass flow rate and heat flow rate. The results of an experimental analysis by using water and ethanol as tested fluids at different operating conditions are shown discussed and analyzed.
The influence of several parameters on the performances was studied experimentally: in particular heat load, operating pressure and fluid filling. The limits in the heat and mass transport are evidenced together with the unstable behavior at the high heat input.
From this work, understanding and useful information are provided for designing and building a two-phase thermosyphon for systems like solar heating.
Abstract
Graphene oxide (GO) has high thermal conductivity and strong hydrophilicity which can enhance the heat transfer performance of the fluid. Standby heat transfer is a long-time, low-heat power ...and small heat area heat transfer, caused in electronic equipment. In this paper, the heat transfer performance of flat plate pulsating heat pipe (FPPHP) under the different concentrations of GO as working fluid is studied to solve the standby heat transfer and analyze the enhancement and the retardation of the GO to FPPHP. The FPPHP is made of aluminum, 2 tubes, with the concentration of GO, is 0.1%, 0.3%, 0.5%, a heating power range of 1∼10 W, and a filling rate (FR) is 30%. The results of the experiment indicate that under the condition of the concentration of 30% of GO, the FPPHP startup at 4 W and run stably at 6 W. When the heating power is 10 W, the wall temperature of evaporation is 89.75 °C, the thermal resistance is 1.18 °C/W.
Display omitted
•A dumbbell-shaped 3D flat plate pulsating heat pipe was proposed.•The performance augmentation of PHPs through capillarity gradient was discussed.•The junction temperature of the ...heating source could be reduced by 42.49 °C.•It can manage an input power of 300 W with junction temperature below 85 °C.
With the development of the data center industry and the increasing power density of servers, it is crucial to remove waste heat from small-area heat sources to ensure the safe and efficient operation of data processing chips. To complement existing studies, in this paper, a novel three-dimensional flat plate aluminum pulsating heat pipe (3D-FPPHP) with four different channel structures for radial heat dissipation of high-power server chips was proposed. The results showed that under the favorable influence of the additional capillarity force provided by the variable diameter channels, the FPPHP filled with acetone can start up easily and has good robustness during variable power operation. When the input power was 150 W, the junction temperature of the heating source could be reduced by 42.49 °C (48.67%) compared to an identical aluminum plate. In addition, a heat sink module based on the proposed 3D-FPPHP with optimal charging ratio was tested in a 1U server chassis. The results showed that it can manage an input power of 300 W (corresponding to a heat flux of 41.15 W/cm2) and achieve a total thermal resistance of 0.2053 °C/W under the premise of ensuring a safe junction temperature of chips below 85 °C.
Energy consumption in the housing sector, is significantly high and continues to escalate. Urbanisation due to population growth and migration from rural areas to cities are two main reasons for this ...rising demand. With the uncertainty in the energy market and the increasing awareness of the impact of fossil fuels on the environment, research work in efficient building design has gained momentum. Energy conservation guidelines in many countries have become mandatory. Howerver, more emphasis has been given to commercial, institutional, governmental and industrial buildings, which commonly employ more efficient HVAC systems than those deployed in houses. Thus, the push towards energy conservation in the residential sector is less noticeable. This is further compounded with the absence of will power to enforce the same energy conservation rules as the case with other sectors. In this paper five passive cooling and heating strategies have been reviewed (passive building design, night ventilation, nocturnal cooling, PCM (Phase Change Material) and IEC (Indirect Evaporative Cooling), solar thermal energy). The aim is to evaluate how to implement them better in a cost-effective way in existing and new houses. The literature review confirmed the need for further investigation of energy efficient HVAC systems with passives strategies solutions for contemporary residential dwellings is required to make a meaningful impact on the energy map of this sector. Also, the viability of an easy to deploy and configure HVAC system for retrofit and new applications for more benefits of these passive strategies either individually or in a hybrid configuration needs to be explored.
•Thin bi-particle size sintered wicks increase wickability due to the increased permeability and capillary pressure.•The increased permeability is achieved by using large particles.•The enhanced ...capillary pressure is related to the reduced effective capillary meniscus radius from small particles.
Two-phase thermal management systems such as heat pipes and vapor chambers offer high heat flux cooling performance in modern electronics and spacecrafts. However, the cooling performance is limited by poor wickability, i.e., ratio of permeability to capillary pumping capability, K/reff. In this study, we examine the enhanced wickability using bi-particle-size, sintered-particle wicks. The bi-particle-size wicks are sintered particle wicks having two different particle sizes (200/60, 200/100, 350/60, 550/60 μm) with two different particle weight ratios (75:25 and 50:50 wt%), and the wickability are characterized using a rate-of-rise method with FC-72 as a working fluid. It is found that the single-layer 200/100 μm (50:50 wt%) bi-particle-size wick enhances the wickability K/reff by 27% and 35%, compared to that of 200 and 60 μm uniform particle wick, respectively. This enhancement is due to the increased permeability from the large particle size and the reduced effective capillary meniscus radius from the small particles. This work provides an insight into advanced wick designs for high heat flux two-phase cooling systems.
The Li-ion battery is of paramount importance to electric vehicles (EVs). Propelled by the rapid growth of the EV industry, the performance of the battery is continuously improving. However, Li-ion ...batteries are susceptible to the working temperature and only obtain the optimal performance within an acceptable temperature range. Therefore, a battery thermal management system (BTMS) is required to ensure EVs’ safe operation. There are various basic methods for BTMS, including forced-air cooling, liquid cooling, phase change material (PCM), heat pipe (HP), thermoelectric cooling (TEC), etc. Every method has its unique application condition and characteristic. Furthermore, based on basic BTMS, more hybrid cooling methods adopting different basic methods are being designed to meet EVs’ requirements. In this work, the hybrid BTMS, as a more reliable and environmentally friendly method for the EVs, will be compared with basic BTMS to reveal its advantages and potential. By analyzing its cost, efficiency and other aspects, the evaluation criterion and design suggestions are put forward to guide the future development of BTMS.
Reducing heat accumulation within vehicles and ensuring appropriate vehicular temperature levels can lead to enhanced vehicle fuel economy, range, reliability, longevity, passenger comfort, and ...safety. Advancements in vehicle thermal management remain key as new technologies, consumer demand, societal concerns, and government regulations emerge and evolve. This study summarizes several recent advances in vehicle thermal management technology and modeling, with a focus on three key areas: the cabin, electronics, and exterior components of vehicles. Cabin-related topics covered include methods for reducing thermal loads and improving heating, ventilation, and air-conditioning (HVAC) systems; and advancements in window glazing/tinting and vehicle surface treatments. For the thermal management of electronics, including batteries and insulated-gate bipolar transistors (IGBTs), active and passive cooling methods that employ heat pipes, heat sinks, jet impingement, forced convection, and phase-change materials are discussed. Finally, efforts to model and enhance the heat transfer of exterior vehicular components are reviewed while considering drag/friction forces and environmental effects. Despite advances in the field of vehicle thermal management, challenges still exist; this article provides a broad summary of the major issues, with recommendations for further study.
•A comprehensive review on heat pipes based waste heat recovery technology is introduced.•The present state-of-the-art for this critical technology is detailed and included.•The background of the ...WHRS is studied.•The potential for this technology in different thermal applications is presented.
Heat pipes are becoming gradually more popular as a passive heat transfer technology due to their effective performance. The heat pipe heat exchanger (HPHE) is an effective tool in recovering waste heat. The present paper provides a comprehensive review of the state-of-the-art background of heat pipe for various waste heat recovery systems (WHRSs). Furthermore, the present paper focuses on a number of the most prevalent applications of utilizing heat pipe for WHR such as heating ventilating and air conditioning (HVAC) systems, solar photovoltaic, water desalination, ceramic kiln industry, steel industry, internal combustion engines, generators, and electronic components in which the heat pipe introduces several benefits. The waste heat resource, type and description of the employed heat pipe, and the working fluid for each application are studied comprehensively. Internal and external thermal modeling techniques, theories, and methodologies are presented for various applications. Based on the energy efficiency improvement, economic investment, and environmental impacts, the employing of HPHE in different applications is a successful and promising technology. Finally, the current challenges and future perspectives related to the use of the heat pipe for WHR in various applications are introduced.
PDF
