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This study experimentally investigated self-pumping transpiration cooling in a hot wind tunnel. The coolant (liquid water) automatically and continuously flowed from the water tank to the heated porous surface without the use of any pump and then evaporated on the porous surface, thereby dissipating a large amount of heat. The self-pumping cooling...
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... self-pumping transpiration cooling method proved to be very effective in solving the abovementioned problem of inhomogeneity. Figure 9 shows the schematic of self-pumping transpiration cooling for the sintered porous plate. There are a large number of micro-pores on the porous surface. ...
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![Figure 4. Wind tunnel system [22]](profile/Gan-Huang-5/publication/336247414/figure/fig2/AS:810976144285697@1570363188856/Wind-tunnel-system-22_Q320.jpg)
Self-pumping transpiration cooling is an advanced and effective method for cooling a high heat flux surface without the assistance of pumps and control systems. This study demonstrates a novel structure for self-pumping transpiration cooling with a protective porous armor structure. The results showed that the cooling system successfully drove liqu...
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... Self-pumping structures have been explored for their potential in intelligent coolant management. 26,27 Additionally, the underlying mechanisms have been explored in depth. [28][29][30][31][32][33][34] Similar to the conduit structures found in trees, directional porous structures can enhance channel flow through lateral permeability [as shown in Fig. 1(a)]. ...
This study uses numerical simulations based on the local thermal non-equilibrium model to investigate the effects of varying intervals between two blocking regions on the transpiration cooling performance of directional porous structures. Numerical methods illustrate the complex thermal interactions within the porous structure, enabling a detailed analysis of temperature distribution and heat transfer mechanisms. The results indicate that as the blocking intervals increase, the maximum temperature of the porous structure first decreases and then rises. A relationship is established between the degree of orientation and the inflection point in maximum temperature corresponding to the blocking interval. For isotropic structures, negligible interaction between the two blocking regions occurs when the blocking interval is approximately five times the width of the blocking region, while for directional structures with εx = 0.001, this interaction becomes negligible at an interval equal to the width of the blocking region. Additionally, the depth of the blocking region plays a crucial role. Under the same coolant injection rate, the maximum temperature of the directional structure is reduced by more than 200 K compared to the isotropic structure. Furthermore, the maximum temperature of the porous structure with two blocking regions is ∼50 K lower than that of a structure with a single blocking region. These findings contribute to assessing the performance of porous structures under blockage conditions and provide an overview for addressing potential issues in next-generation thermal protection systems.
... Their results indicated that, as the substrate porosity increases (from 0.1 to 0.9), both the evaporation rate and efficiency initially increase and then decrease, and the turning point is the porosity of 0.6. Huang et al. [13] conducted an experimental study of self-pumped evaporative cooling in a high-temperature wind tunnel. They achieved self-supplied coolant flow and evaporation on the porous surface, maintaining a stable temperature distribution. ...
... Porous media had great advantages in enhancing fluid-solid heat transfer (Sun et al., 2022), its structure (Yakimov, 2015) and physical characteristics (Liu et al., 2010; had significant impact on transpiration cooling effect. One of the most important parameters influencing the effect of transpiration cooling was particle diameter (Huang et al., 2017;Huang et al., 2019). Reducing the particle diameter minimized the pore channels, increased the specific surface area of porous, enhanced fluid convective heat transfer, and hence improved cooling efficiency (Shi and Wang, 2011). ...
Transpiration cooling is a highly efficient active thermal protection technology, which has a great application prospect in the thermal protection of hypersonic vehicles. Nevertheless, the problem of large injection pressure caused by porous structure in transpiration cooling system has been ignored in previous studies. In this work, the transpiration cooling performance of double-layer sintered metal particle plates with different particle diameter combinations and plate thickness were simulated. The results showed that the cooling effectiveness of double-layer plates was improved when the particle diameter of the porous plate in direct contact with the main stream decreased. The inner plate particle diameter and plate thickness had little effect on cooling performance. By increasing inner plate particle diameter, the coolant injection pressure can be lowered by 41% while the structural thickness was maintained. Further reducing the thickness of the outer plate to 1/4 of the total thickness can reduce the injection pressure to 38% of the single plate, which provided an optimization direction for reducing engine power consumption caused by heat dissipation.
... There is much research work on the steady problems of two-phase flow with liquid phase change in microstructure or nanostructure. A great number of experiments have been conducted to explore the wide range of two-phase flow regimes in different microstructures [12][13][14]. Several widely recognized mathematical models [15][16][17][18][19][20][21][22][23][24] and a series of numerical approaches have been developed to probe into the mechanism. ...
Two-phase flow with phase change in microstructure or nanostructure is an important issue in many fronts and critical applications nowadays, but with a lack of comprehensive understanding of the mechanism. This paper numerically investigates the transient behavior of two-phase flow with liquid phase change in the porous media, which consists of a series of connected pores at micro and nanoscale with the transient form of the semi-mixed model and self-compiled programs. Transient variation and spatial distribution of structure temperature, thermal non-equilibrium characteristic, phase change location and fluid-driven pressure are obtained and analyzed, and effects of initial system temperature, structure parameter and material property on the transient behaviors of two-phase flow and fluid-structure coupling heat transfer are discussed. The numerical simulations indicate that the two-phase flow with phase change in porous media is complex and ever-changing before reaching a steady state and affected by the above-mentioned three kinds of parameters significantly. Particularly, distinct phenomena of transient heat transfer deterioration and vapor block are discovered, and it is revealed that the transient heat transfer deterioration and vapor block are more serious in a porous matrix with smaller porosity and made of materials with higher heat capacity and density.
... At present, the cooling technologies applied in aeroengines are mainly including film cooling [3][4][5], transpiration cooling [6][7][8], and impinging-film cooling [9][10][11]. Film cooling is the most commonly used for liner cooling. ...
This paper describes an experimental investigation on flow field characteristics of impinging-film cooling. Particle Image Velocimetry (PIV) technology has been applied to observe the effect of blowing ratio (0.04≤M≤0.3), temperature ratio (0.73≤Tu≤0.91), jet-to-plate pitch (1.6≤Zn≤3.2), and spacing of impinging holes (1.94≤Yn≤3.5) on the flow field patterns in an impinging-film cooling test rig under atmospheric pressure. Experiment results show that the near-wall entrained vortex at the downstream of the slit moves downstream of the test rig as the blowing ratio increases, which increases the effective protection length of the film. While the vortex at the end of the inducting slab is stronger, this will increase the mixing in the shear layer. The radial size of the near-wall entrained vortex tends to decrease as the temperature ratio increases at the low blow ratio, and the entrainment effect on the downstream of the slit becomes smaller, causing the separation zone to decrease. Increasing the jet-to-plate pitch, the size of the near-wall entrained vortex increases, and the thickness of the film layer increases, this strengthens the separation effect of the near-wall airflow from the wall surface. The larger the spacing of the impinging holes, the more uneven the velocity distribution of the film.
... However, nanowire-based spectral splitting technology is potentially applicable to PV-T collectors by adding a thermal absorber to collect the waste heat generated in the nanowires. The thermal absorber can be either convection air blowing through the nanowires or flowing water pumped by the capillary effect [101][102][103], which promises particularly innovative collector designs by minimizing the required pumping power. Table 2 provides a comprehensive summary of publications concerned with the development and use of nanomaterials for spectral splitting in solar applications. ...
Hybrid photovoltaic-thermal (PV-T) collectors, which are capable of cogenerating useful thermal energy and electricity from the same aperture area, have a significantly higher overall efficiency and ability to displace emissions compared to independent, separate photovoltaic panels, solar thermal collectors or combinations thereof. Spectral splitting has emerged as a promising route towards next-generation high-performance PV-T collectors, and nanotechnology plays an important role in meeting the optical and thermal requirements of advanced spectral splitting PV-T collector designs. This paper presents a comprehensive review of spectral splitting technologies based on nanomaterials for PV-T applications. Emerging nanomaterials (nanofluids, nanofilms and nanowires) suitable for achieving spectral splitting based on reflection, diffraction, refraction and/or absorption approaches in PV-T collectors are presented, along with the associated challenges and opportunities of these design approaches. The requirements from such materials in terms of optical properties, thermal properties, stability and cost are discussed with the aim of guiding future research and innovation, and developing this technology towards practical application. Nanofluids and nanofilms are currently the most common nanomaterials used for spectral splitting, with significant progress made in recent years in the development of these materials. Nevertheless, there still remains a considerable gap between the optical properties of currently-available filters and the desired properties of ideal filters. Aiming to instruct and guide the future development of filter materials, a simple generalized method is further proposed in this paper to identify optimal filters and efficiency limits of spectral splitting PV-T systems for different scenarios. It is found that the optimal filter of a spectral splitting PV-T system is highly sensitive to the value of thermal energy relative to that of electricity, which therefore depends strongly on the application and location. The efficiency limit of spectral splitting PV-T collectors is significantly higher than that of standalone PV panels. The stability of nanomaterial filters remains a critical challenge for their long-term employment and also for high-temperature operation in practical applications.
... The critical heat flux of this cooling system also exceeded 10 MW/m 2 after parameter optimization. Huang et al. [29] tested the self-pumping transpiration cooling effect on sintered porous plates in a wind tunnel, coupled with a hot mainstream. Their results showed that the self-pumping system effectively adapted to varying mainstream conditions. ...
... The surface temperature of the porous armor could be decreased by decreasing the thickness or increasing the heat conductivity, according to Fourier's law of heat conduction. The outer surface temperature was adjusted by changing the material or geometry of the porous armor, and thus was more flexible than the previous self-pumping transpiration cooling system [29]. In contrast, the surface temperature of the previous self-pumping transpiration cooling system was fixed at the boiling point of water, resulting in overcooling of the surface and the waste of coolant in some situations [29]. ...
... The outer surface temperature was adjusted by changing the material or geometry of the porous armor, and thus was more flexible than the previous self-pumping transpiration cooling system [29]. In contrast, the surface temperature of the previous self-pumping transpiration cooling system was fixed at the boiling point of water, resulting in overcooling of the surface and the waste of coolant in some situations [29]. (3) Tm = 815 K Figure 10. ...
Self-pumping transpiration cooling is an advanced and effective method for cooling a high heat flux surface without the assistance of pumps and control systems. This study demonstrates a novel structure for self-pumping transpiration cooling with a protective porous armor structure. The results showed that the cooling system successfully drove liquid water without any pumps and effectively cooled the heated surface. The water evaporated at the interface between the porous armor and the sintered porous plate, and then the vapor was exhausted through the porous armor with secondary heat convection cooling. The coolant mass flow rate reduced coolant consumption by approximately 39% with the aid of the porous armor. The self-pumping transpiration cooling system automatically adjusted the coolant mass flow according to different mainstream conditions. The surface temperature of the sintered porous plate maintained a near constant value under different mainstream conditions, while the temperature of the porous armor changed along with the mainstream conditions. The self-pumping transpiration cooling system was effective owing the protection of the porous armor, even when the outside porous surface had an evident blockage. Thus, the reliability of the self-pumping system was improved.
